LIBRARY OF THE UNIVERSITY OF CALIFORNIA Class MANUALS OF TECHNOLOGY EDITED BY PROF. AYRTON F.R.S. and R. WORMELL D.Sc. M.A. STEEL AND IKON COMPRISING THE PRACTICE AND THEORY OP THE SEVERAL METHODS PURSUED IN THEIR MANUFACTURE, AND OF THEIR TREATMENT IN THE ROLLING MILLS, THE FORGE, AND THE FOUNDRY BY WILLIAM HENEY QREENWOOD F.C.S., M.INST.C.E., M.'LM.E. ASSOCIATE OF THE EOTAL SCHOOL OF MINES WITH 97 DIAGRAMS FROM ORIGINAL WORKING DRAWINGS OF THE ^TWELFTH THOUSAND UNIVERSITY CASSELL AND COMPANY, LIMITED LONDON, PARIS, NEW YORK & MELBOURNE. MCMII ALL RIGHTS EESERVED First Edition January 1884. Reprinted June 1884, 1887, 1890, 1891, 1893, 1896, igoo, 1902. GENERM- ' P E E F A C E . TUB aim of the present work on Steel and Iron has been to produce, within moderate limits, a comprehensive Manual of practical information and of the scientific principles upon which the practice rests. The author hopes in this manner to render the book of service to the general student of the branch of Technical Science of which it treats, and also to offer to the intelligent work- man a succinct statement of the scientific principles upon which depends the success of the several processes con- ducted or superintended by him, and upon which the construction of his plant or machinery is based. The book, therefore, is not intended to supersede the expe- rience and practical knowledge that can be gained only in the Works, but the author hopes it will be found a useful adjunct to, and contribute to a clearer under- standing of, these things. The information has, as far as possible, been brought up to date, and for this purpose numerous articles in English and Foreign Scientific Journals and Proceedings of Societies have been consulted. In elucidating the text, the author has preferred to use practical drawings rather than mere pictures, and he thinks that an elementary acquaintance with mechanical drawings will enable the reader to fully understand 101974 VI STEEL AND IRON. them. Although a few of the woodcuts have been re- produced from papers in the Proceedings of learned Societies, &c., the great majority have been reduced from original working drawings of existing furnaces and plant, all drawn accurately to scale; and the author takes this opportunity to acknowledge his obligations to the numerous Ironmasters, Engineers, and others who have kindly furnished him with such drawings and assistance. Throughout the chemical portion the nomenclature, atomic weights, and notation now universally employed have been adopted ; and here also only a preliminary elementary knowledge of inorganic chemistry is required of the reader. Within the compass of this volume, it has been impossible to enter with minute detail into the con- sideration of all the particulars which are necessary to make the student perfectly conversant with the whole range of the metallurgical and mechanical treatments between the iron ore and the production of the finished bar, rail, or section, but typical examples of the various operations have been described, and their details more or less fully discussed so far as scientific principles are involved. W. H. G. CONTENTS. CHAPTER I. EXPLANATION OP TERMS 1 CHAPTER II. REFRACTORY MATERIALS, CRUCIBLES, ETC 14 CHAPTER III. THE ORES OF IRON . .30 CHAPTER IV. METALLURGICAL CHEMISTRY OF IRON 40 CHAPTER V. CAST- OR PIG-IRON 61 CHAPTER VI. THE PRODUCTION OF PIG-!RON . . .' "' ... . ' . 79 CHAPTER VII. THE BLAST FURNACE. HOT-BLAST STOVES, HOISTS, LIFTS, ETC. Ill CHAPTER VIII. FUEL, BLAST, CHARGES, YIELD AND WASTE GASES or THE BLAST FURNACE 168 CHAPTER IX. CASTINGS IN IRON, FOUNDRY APPLIANCES, ETC. . * . .185 CHAPTER X. MALLEABLE OR WROUGHT IRON 202 CHAPTER XI. THE PRODUCTION OF MALLEABLE IRON DIRECT FROM THE ORE 211 CHAPTER XII. INDIRECT METHODS FOR THE PRODUCTION OF MALLEABLE IRON. THE PRODUCTION OF MALLEABLE IRON IN OPEN- HEARTH FURNACES . , 228 viii STEEL AMD IRON. CHAPTER XIII. PAGH REFINING OP PIG-!RON, OR THE CONVERSION OF GREY INTO WHITE IRON IN THE COKE REFINERY . . . .238 CHAPTER XIV. PUDDLING, OR THE PRODUCTION OF MALLEABLE IRON BY THE DECARBURISATION OF PIG-!RON IN THE REVER- BERATORY FURNACE .248 CHAPTER XV. MECHANICAL PUDDLING AND ROTARY PUDDLING FURNACES. 285 CHAPTER XVI. FORGE AND MILL MACHINERY, FURNACES, PLANT, AND OPERATIONS . . . ^ . . . . . 300 CHAPTER XVTI. STEEL AND INGOT IRON . . . . . . 384 CHAPTER XVIIL THE METHODS EMPLOYED IN THE PRODUCTION OF STEEL. THE PRODUCTION OF STEEL DIRECT FROM THE IRON ORE, AND BY THE CARBURISATION OB 1 MALLEABLE OR BAR IRON. 402 CHAPTER XIX. THE PRODUCTION OF STEEL BY THE DECARBURISATION OP PIG-IRON IN THE FINERY OR IN THE PUDDLING FURNACE 433 CHAPTER XX. PRODUCTION OF STEEL BY THE FUSION OF PIG-!RON WITH MALLEABLE IRON OR WITH IRON ORES IN THE OPEN- HEARTH STEEL-MELTING FURNACE 445 CHAPTER XXI. THE BESSEMER OR PNEUMATIC PROCESS FOR THE PRODUC- TION OF STEEL FROM PIG-!RON. THE BASIC PROCESS FOR THE CONVERSION OF PHOSPHORIC PIG-!RON INTO STEEL IN THE BESSEMER CONVERTER . . . .460 CHAPTER XXII. THE PRODUCTION OF HOMOGENEOUS STEEL INGOTS, FLUID COMPRESSION OF STEEL, COMPOUND ARMOUR PLATES, ETC. 506 OF THE UNIVERSITY OF STEEL AND IE CHAPTER I. EXPLANATION OF TERMS. 1. CHEMICALLY pure iron exists only as a curiosity and has no practical application in the arts. It is void of commercial value as a constructive material, and cannot be prepared upon a large scale. Yet in combination with very small proportions of carbon, and almost infini- tesimal proportions of other elementary bodies, as sulphur, silicon, phosphorus, &c., it yields products such as Steel, Malleable or Wrought-iron, and Cast or Pig-iron, which possess properties rendering them by far the most impor- tant factors in our metallurgical industries. It is with the production and working of these commercial varieties of iron that it is proposed to deal in this volume, but before proceeding to the treatment of the subject proper it may be well to offer a few remarks upon, and define once for all, the interpretation which we shall place upor certain words and phrases which are now universally used to designate special physical qualities of the metals ; and upon the names given to the products obtained, and processes performed, in the metallurgical or mechanical treatment of Iron and Steel. 2. Tenacity is the property of resisting fracture from the application of a tensile or stretching force, and is usually stated in England in terms of the number of tons or hundredweights required to break a bar one square inch in sectional area. In France, Germany, and B STEEL AND IRON. [Chap. I. generally over the Continent, the force or weight is expressed in kilogrammes (2-2046 Ibs.), with the square centimetre as the unit of area (the centimetre = -3937 inch), whilst in Russia the units often employed to express the pressure and the sectional area are the atmosphere (about 15 Ibs.) and the square inch respec- Fig. 1. Forms of Test-pieces ; a, before fracture, and b, after fracture. tively. '00635 x number of tons per square inch = number of kilogrammes per square centimetre. This quality of tenacity is possessed by wrought or malleable iron and by steel in a very marked degree, tho latter standing at the head of the metals in this respect ; but, as will be mentioned subsequently, this quality is much affected, in steel especially, by its composition, by its freedom from certain deleterious elements and foreign matters, and also by the molecular condition arising either from the mode of its preparation or from its previous treatment, physical or mechanical, as by hammering, rolling, annealing, hardening in water or oil, &c., &c. Chap. I.] DUCTILITY. 3 Figs. 1 and 3 indicate the more general forms of test pieces employed in testing the tenacity of bars, plates, &c., of wrought iron or steel, together with their usual mode of fracture ; and Fig. 2 shows the grip for holding the test-piece in the machine. The length of the test- pieces and the area of their cross section vary in different works. Thus in testing bars, while some firms operate upon samples of only two inches in length between the points of measurement, and with half an inch of sectional area (-79 inch diameter), as in Fig. 1, , others and their practice is the more general operate upon pieces of six, eight, or ten inches in length. The shorter lengths are employed in engineering establishments, Test- liiece. Fig. 2. One Form of the Bridle and Grip for holding the Test-pieces in the Testing Machine, (p. 352). for the testing of forgings, or finished work, whilst the larger specimens are always employed by the manufac- turer in testing rolled bars or plates. 3. Ductility is the property of being permanently extended by a tensile force, or of being drawn into wire. Like tenacity, it is powerfully influenced by the com- position of the iron or steel, and is markedly affected by each one-tenth per cent, of carbon that enters into the composition of the metal, whilst silicon in very much smaller proportions likewise sensibly affects it. Experi- ments conducted at Woolwich indicate that this quality varies also with the temperature; thus wrought-iron, such as Yorkshire rods, 70 inch in diameter, which possessed at 100 Fahr. a ductility represented by 25, showed a ductility of only 15 at a temperature of 200 Fahr., and of 13' 7 5 at a temperature of 500 Fahr. 4 STEEL AND IRON. [Chap. I. 4. Elasticity is represented by the length to which a given rod, bar, or plate of metal may be extended by a tensile force without remaining permanently lengthened on removal of the stretching force. 5. The limit of elasticity is an expression employed to represent the force, required to extend a given section of metal to the limit of its elastic strength ; or is the greatest tensile stress registered before an appreciable permanent set is produced in a given section of the metal. Within certain limits the stretching of either iron or steel beyond its original elastic limit increases the strength and range of its elastic action ; cold-rolling and wire-drawing afford examples of such an increase of strength by the permanent extension of metallic rods beyond their original elastic limit. Iron wire after this treatment attains to a tensile strength of upwards of 100 tons to the square inch. Iron or steel rods which, as received from the rolling mill ready for wire-drawing, have a tensile strength of 57 tons to the square inch, after drawing down as far as is practicable without annealing will have acquired a tensile strength of 80 tons to the inch, and tlie same wire, when finished to No. 14 gauge (087 inch diameter), possesses a tensile strength of upwards of 98 tons to the inch.* The wire employed by Sir William Thomson in his deep-sea soundings sus- tained 149 tons to the inch. Steel, which in bars of the ordinary sizes used for bridge building has a tensile strength of about thirty-two tons to the square inch, with an elongation of 15 per cent, in samples of one foot in length and an elastic limit of about seventeen tons per square inch, will have, after drawing into wire, a tensile strength of seventy-two tons to the square inch, with an elongation of 4 per cent, in samples of one foot in length.f In the same manner the links for Suspension Bridges have been purposely strained slightly beyond the original limit of their elasticity before putting to work, * " Revue Universelle des Mines," 1881. t Transaction* of the American Society of Civil Engineers. 1880. Chap. 1.1 LIMIT OP ELASTICITY. ft whereby bars of somewhat altered dimensions are pro- duced, but which possess also a little more rigidity than the originals. Again, bridge or ship-plates of the same quality will vary as much as two tons to the square inch in their tensile strength, according as the rolling is finished at a high heat or at a very low temperature, the latter yielding the stronger plate, but after annealing both plates will then have the same lower strength. 6. It is understood that to subject a test-piece to repeated tensile stresses, each of which is just insufficient to give a permanent set to the sample, will gradually in- crease the tensile strength corresponding to the limit of elasticity. In other words, to remove the stress after each pull or elongation of the specimen caused by the stress, gives a slightly higher figure as the limit of elasticity than if the limit be determined by watching the point where the elongation begins to increase in a marked manner without removing the stretching weight after each elongation ; so that these repeated pulls are attended with the same result as an increased hammering of the specimen. Mr. T. F. Barnaby, in a report to the Admiralty, says that Bessemer steel heated to 400 Fahr. is ten tons per square inch stronger than when at the normal temperature, and loses at the same time but one-third of its ductility, and this increase in strength appears to hold up to 600 Fahr. In iron, again, there is an increase, but only to the extent of one-third of the above, and the increase in strength is attended by the loss of from one-quarter to one-half of its ductility. At a very dark-red heat there is a great fall in the tensile strength of both iron and steel.* 7. The high range of the limit of elasticity in steel, compared with the ultimate strength of the metal, together with the greater range of its elastic action, and its superior tensile strength over iron, are the advantages opon which the introduction of steel as a constructive material largely depends. * The Engineer, March 31st, 1882, STEEL AND IRON. [Chap. I. 8. Fatigue is the diminished resistance to fracture which comes after repeated applications of stress, especially after stresses varying within a wide range. Fig. 3. Forge Tests of the Malleability and Ductility of Iron and Steel. 9. Malleability is the quality of permanently ex- tending in all directions by pressure, as by hammering Chap. I.] WELDING. 7 or rolling, without rupture, and is essential in the metal to be extended by rolling into thin sheets. All malleable metals are more or less ductile, whilst iron and steel are amongst the most malleable. Russian sheet-iro-n has been exhibited at Paris of a thickness not exceeding T f^ part of an inch, and Fig. 3 shows a usual test of this quality as applied to steel rivets and angle irons, which are first heated to redness, and then bent or hammered into the forms shown without cracking at the edges. 10. Welding is the quality whereby, if two clean surfaces are presented at a suitable temperature, and pressure applied as by hammering or squeezing by hydraulic or other power, they will unite to form one coherent mass. The conditions necessary for welding are these : 1. that the surfaces shall be perfectly clean. 2. that the iron or steel shall be at a temperature producing a plastic, coherent, and amorphous, non-crystalline (but not fluid) state. Under these conditions but moderate pressure is required to ensure a perfect weld. This property of welding is typically presented by wr ought-iron at a white heat, and in a scarcely inferior degree by the milder qualities of steel, whilst in cast-iron there is an entire absence of it. As above mentioned, it is necessary that the surfaces to be welded be quite clean and free from scale, and for this purpose the smith throws upon the white-hot surface of iron on his hearth a quantity of sand (silica), which forms a readily fusible and fluid slag with the oxide of iron on the welding surface, so that, when the two surfaces are placed in contact and the mass is struck with the hammer, the fluid slag is thrown out, leaving the metallic surfaces in contact, clean and free from oxide or cinder. When steel is the subject of operation, the smith often prefers a mixture of ten parts of borax (Na 2 B0 3 ) with one of sal-ammoniac (NH 4 C1), which powder he uses instead of sand for cleansing the oxide from the surfaces to be welded. 8 STEEL AND IRON. [Cha?. L Professor Ledebur concludes that the difficulty in welding some varieties of malleable iron arises from the presence of such foreign bodies as carbon, silicon, sulphur, phosphorus, oxygen, manganese, copper, &c. ; and he adds that, up to 07 per cent., oxygen in comomation is less injurious to welding than a larger proportion of manga- nese, silicon, or phosphorus, but if oxygen be present beyond 1 per cent., then welding becomes impossible. The above-mentioned elements harden malleable iron, and probably affect its weldability by their ready oxidability. All foreign substances present in the iron, except fluid silicates, which remove the scale and so clean the surfaces to be welded together, have an injurious influence upon the welding quality, hence the purest iron can usually be the more easily welded. 11. The temperatures employed in working iron and steel are often expressed by such terms as "red-heat," "white -heat," &c., and the following figures indicate approximately the temperatures so defined : Incipient redness correspondsto^a temperature 52 - c ( ^ R) _ Dull red 700 C. (1292 F.) Cherry red 900 C. (1652 F.) Deep orange :j 1100 C. (2012 C.). White-heat 1300 C. (2372 P.). 12. Toughness, in metals, is a relative expression of the power of resisting fracture by bending or torsion, and it is measured by the number of times to which a definite section of the metal can be bent through a certain angle on either side the perpendicular without any fracture. 13. Softness is a relative term sometimes used to express the quality of a metal whereby it easily perma- nently yields to pressure without fracture. 14. Annealing, in the case of iron and steel, is the name applied to the operation by which the metal is first heated to bright redness, and is then allowed to cool down Chap. L] COLD-SHORT. ( J slowly, either in the open air, or, more usually, under a layer of ashes or other materials having an inferior con- ductivity for heat. Annealing is often prescribed as an antidote for correction or prevention of the irregularities in strength arising from unequal or irregular cooling in steel and other castings, or in forgings the several parts of which have been finished under the hammer at different temperatures. By again re-heating such articles to a uniform red-heat, and then allowing them to cool down as slowly as possible, the molecules are enabled to assume a more uniform and normal condition with respect to each other, whereby the probability of any local tension or strain existing at any point is minimised. Sheet-iron, after rolling, is frequently annealed in quantities of eighteen tons of plates at once, for which purpose the plates are placed in boxes of about ten feet in length, five feet six inches in depth, and three feet six inches in width. The boxes, when charged, are run into furnaces where they remain about twenty-four hours, so as to become regularly and uniformly heated throughout ; they are then withdrawn and allowed to cool down during four days without the access of air, after which the sheets come out quite clean and free from scale. The same term (annealing) is also applied to the operation of slowly heating to redness of crucibles before introducing them into the steel melting furnace, as described on page 420. 15. Cold-short is the term employed to express the condition of iron or steel, in which it cannot be worked by hammering or rolling at or below a dull red-heat without more or less fracturing or cracking at the edges, according to the degree of the cold-shortness ; though such metal may, under the same conditions, be worked with the utmost facility at a white or welding heat. Red-short, on the other hand, is applied to such metals as do not permit of being readily worked at a temperature at or above redness, although such metal frequently admits of being worked 10 STEEL AND IRON. (Chap. 1. by hammering or rolling without fracture at a low red- heat. Amongst the elements which, in small quantities, induce cold-shortness in iron or steel, may be enumerated phosphorus, silicon, arsenic, and antimony, of which the first mentioned is the most common source of this defect ; whilst red-shortness is often the result of the presence of an undue proportion of sulphur in the metal, but copper, antimony, silver, calcium, &c., also produce the same effect. 16. Ore is the name applied to the metalliferous matter in the state in which it is extracted from the mine by the miner, and which in the case of iron is always either an oxide or carbonate of the metal, accompanied by certain extraneous matters, gangue, or vein stuff, essentially siliceous, calcareous, argillaceous, or bituminous in character, as will be further noticed when speaking of the several ores of iron. In Wales and some other districts the term "mine" is used as synonymous with ore, the same word being thus used to designate both the workings and the metalliferous matter extracted from them. 17. Reduction, or Smelting, is the process or processes employed for the separation or extraction on the large scale of a metal from its ores, and the active element used in effecting the reduction is known as the " reducing agent," which, in the case of iron or steel, is invariably carbon or carbonic oxide (CO), aided by a very high temperature. 18. Calcination is the process in which iron-ores are heated in heaps, or kilns at a comparatively low tempera- ture, for the expulsion of water, carbonic anhydride (CO 2 ), sulphur, and other volatile matters, with the oxidation of the ferrous oxide and carbonate to the condition of ferric oxide. The necessary heat is produced either by the combustion of the bituminous matters in the ore itself, as in certain Scotch Blackband Ironstones, or by the addition of fuel which is mixed with the ore to be calcined in the heaps or kilns, or by the waste heat drawn from the blast furnaces. Chap. L] FLUX AND SLAG. 11 19. Fining is the term employed to designate the stage of the process in the conversion of pig into malleable iron, during which the decarburisation of the pig-iron is mostly effected, either in the puddling and pig-boiling processes, or in the charcoal finery vorking upon refined metal. 20. Refining is the process sometimes employed to effect the partial decarburisation and purification of pig- iron, with its conversion thereby into white, refined, or plate metal, as a preliminary to its conversion into malleable iron by its subsequent treatment either in the puddling furnace or in the charcoal finery. 21. Puddling and Pig-boiling are processes whereby pig or refined iron is converted into malleable iron either in fixed reverberatory or in revolving furnaces. 22. Shingling, or Nobbling, is the name applied to the treatment to which the puddled ball is subjected in the squeezer or under the hammer, for the welding together of its particles into a solid bloom, with the expulsion of slag, cinder, and scoriae from the puddled ball, 23. Cementation is the process by which the car- burisation of malleable iron for the production of steel is effected, by the prolonged exposure of it at a tempera- ture below fusion, to the action of solid or gaseous carbonaceous matters. The same term is also applied to the converse class of operation, by which articles made of cast-iron are rendered malleable by a process of decarburisation, effected by exposing them to the pro- longed influence of heat and oxidising materials, as haematite, iron-ore, etc. 24. A Flux is a substance added to the furnace charge, which, by combining with the siliceous and extraneous matters or gangue of the ore, yields at the furnace tem- perature a readily fusible substance known as a slag. In the case of iron ores accompanied by a gangue of infusible quartz, the ore might still be smelted without the addition of any flux, but it would only be at the expense of a los* 12 STEEL AND IRON. [Chap. I. of iron ; since ferrous oxide (FeO) readily combines with quartz or silica, producing a fusible ferrous silicate, which is not reducible by carbon or carbonic oxide, the reducing agents of the blast furnace, and which therefore would pass away into the slag with a corresponding loss of iron. A similar result follows if the gangue be argillaceous, for the aluminous silicate (clay), which alone is practically infusible, combines readily with a portion of the ferrous oxide of the ore, producing thereby a double silicate of alumina and iron, which is easily fusible ; but to obviate the loss of iron which would thus result it is usual to add a flux of limestone, which enters into combination with the silica or siliceous clay, yielding thereby fusible silicates, or slags of the double silicates of lime and alumina. In the haematite districts, where the ores are the rich oxides of iron (hematites), it becomes necessary to add as the fluxing materials not only lime but also argillaceous matters, in the form of shales or argillaceous iron-ore. The conditions regulating the quality and amount of materials added as fluxes will be more fully discussed when treating of the blast- furnace reactions. 25. Slags are the readily fusible compounds, resulting,, as above noted, from the combination in the furnace of the siliceous and other matters of the ore with one another, and with the materials added as fluxes, the re- sulting slags in virtue of their lower specific gravity floating above the molten metal in the furnace hearth. Slags from the Blast-furnace, Bessemer Converter, Siemens Hearth, or other iron- or steel-producing furnaces or apparatus, are thus anhydrous silicates of lime, magnesia, alumina, iron, and manganese, with smaller proportions of other metallic bases derived, as just noted, from the extraneous matters of the ore, the ashes of the fuel, the flux added to the furnace charge, and, in a certain degree, from the materials of which the furnace is constructed. The slags are possessed of the most various physical, chemi- cal, and mechanical properties, depending upon a variety of Chap. 1.] FURNACE SLAGS. 1 3 causes, such as a light or heavy burden, the former usually yielding light-coloured, white, or grey slags, whilst the latter has a tendency to yield slags containing iron and which are thus either black or dark in colour. An excess of lime generally produces a very friable slag of a dull stony aspect ; but whilst a blast-furnace slag will be dull and opaque if cooled slowly, a similar slag will be lustrous and glassy if cooled quickly. Blocks of slag from the blast-furnace frequently present layers of grey, brown, blue, reddish-black, and white in the same block ; further, as a rule, the slower the rate at which the .slag has cooled, the greater is the tendency to assume a crystal- line structure ; also, if the slag be not a definite chemical compound but a portion crystallised out during cooling, leaving the residue as an amorphous mass, it is found that the crystallised portion has often a definite chemical com- position, whilst the amorphous portion cannot be formu- lated. Again, a slag which usually cools so as to form a highly-coloured vitreous body, will often swell up into a white pumice-like body if allowed to flow in contact with water when it is tapped from the furnace j and, in the same manner, hair-like masses or aggregations of fine shreds are produced by the mechanical action of the blast meeting the pasty descending slag in the furnace. Ferrous oxide increases the fusibility of the slag, whilst magnesia decreases it, and thus a dolomitic (magnesian) limestone added to the blast-furnace as a flux decreases the fusibility of the slag, and has a tendency to whiten the pig-iron. Small quantities of the metallic silicates suffice to impart their distinctive tints to the slags in which they occur ; thus the dark green or greenish-black colour so frequently observed in the slags produced in the iron manu- facture is due to the presence of a ferrous sulphide ; whilst the blue colour often seen in iron slags is by some attributed to the presence of Titanic oxide, and by others to ferrous oxide ; and the amethyst-blue colour of certain charcoal furnace slags appears to be due to the 14 STEEL AND IRON. [Chap. II. presence of manganese. Ferrous oxide when present also materially lowers the melting-point of the slag. 26. Blast-furnace slags are regarded essentially as com- binations of monobasic and sesquibasic silicates of lime and alumina respectively, in the proportions represented by the following formula 3 (CaO, Si0 2 ) + 2 A1 2 (X, 3 Si0 2 ; whilst Dr. Percy considers the slag or cinder of the refining furnace (tap or forge cinder) to be an ortho- silicate of the formula 2 FeO, SiOjj, or Fe 3 Si0 4 . CHAPTER IL REFRACTORY MATERIALS, CRUCIBLES, ETG 27. THE refractory materials used in the metallurgical treatment of iron and steel are usually fire-clays (impure hydrated silicates of alumina) and a few natural rocks or minerals, either alone or suitably mixed with other in- gredients, as lime, graphite or plumbago, burnt-clay, &c. The materials so prepared are then moulded into bricks or crucibles of various forms, into pipes, tiles, tubes, &e., as may be required, or are rammed in position upon furnace hearths, so as to form bottoms or linings in the different ways to be subsequently noticed. 28. Rocks can rarely be used alone, owing to their want of homogeneity, their great tendency to crack when exposed to high temperatures, and their want of cohesion after being once broken up prior to their being moulded into the special shapes required in furnace construction. 29. Clays also can rarely be used singly or in their raw state, but require admixture with other ingredients, as well as some preliminary mechanical treatment, to adapt them to the requirements of practice, since raw untem- Chap. H.] REFRACTORY MATERIALS. 15 pered clays when used alone invariably contract in volume, and crack when exposed to a high temperature, leaving thereby fissures and depressions which quickly destroy the furnace in which they occur. Clays are re- fractory in proportion to their basic character that is, to the alumina (Al.j0 3 ) which they contain and are less useful as fireclays, as they become acid (siliceous) in their character ; whilst the presence of ferrous oxide (FeO) to the extent of 2 or 3 per cent, renders most fire-bricks useless at the temperature of the Siemens Steel-Melting Furnace. The plasticity of clays, or their capacity to be moulded into any required form without loss of cohesion, is due to the chemically combined water which they con- tain, and depends to some extent upon the amount of alumina which enters into their composition, and upon the degree of fineness of the structure of the clay ; the finer the particles usually the more plastic is the clay. The hygro- scopicwater of clays maybe expelled by heating them to 100 C. (212 Fahr.), without thereby impairing their plastic quality ; but at a higher temperature the combined water is also expelled, and the clay then loses all plasticity, which quality it does not recover, even when again mixed with water, although the water so added is soaked up rapidly. Alkalies, when present to the extent of from 1 to 2 per cent., render fire-clays or fire-bricks fusible at high temperatures. Lime and magnesia (both by themselves very refractory materials) suffice, when in but small portions, to make most fire-clays comparatively fusible. 30. Lime (CaO) and Magnesia (MgO) are very refractory, and are both used in the manufacture of certain crucibles employed in metallurgical operations, but it militates against the use of magnesia that it is somewhat expensive and difficult to obtain, although large quantities of an impure magnesian limestone have latterly been found in the island of Eubrea. Lime always occurs native in the form of calcic carbonate, which, upon the application of heat, loses its carbonic anhydride (CO ? ) and becomes caustic, but on the withdrawal of 16 STEEL AND IRON. [Chap. II. the heat, and fresh exposure to atmospheric influences, it rapidly re-absorbs carbonic anhydride and moisture, partially slacks, and falls to powder ; hence it can only be used in such furnaces as allow of a continuous, non- intermittent heat, as in certain Styrian furnaces, where it is sometimes employed. Owing to the facility with which lime and silica combine to form a fusible silicate, it is necessary to avoid contact of the two in any part of a furnace exposed to a white heat. 31. Magnesite the impure magnesia occurring at Eubcea and elsewhere contains a little lime besides silica, serpentine, and ferrous nilicates, which latter require separation by hand either before or after calcination of the mineral. Magnesia is used either in the form of bricks or as crucibles, and, like lime, it first requires calcination at a very strong heat to expel carbonic anhydride, and also to prevent the contraction that would otherwise take place upon heating. The calcined material is then mixed with from 15 to 30 per cent, of the imperfectly calcined or raw mineral, and from 10 to 15 per cent, of water is added, when, after thoroughly mixing, it is then pressed into iron moulds, dried, and burnt as with ordinary bricks. 32. Bauxite is a hydrated aluminous ferric oxide of variable composition, containing usually about 60 per cent, of alumina and only from 1 to 3 pei* cent, of silica, with 20 per cent, of ferric oxide (Fe 2 3 ) and from 15 to 20 per cent, of water, but other specimens contain much largei proportions of silica with less ferric oxida It is a very refractory body, and affords an example of a substance containing some 20 per cent, of oxide of iron, but being yet practically infusible; whilst 4 or 5 per cent, of ferrous oxide in most fire-clays renders them as fusible as ordinary bricks, and 2 per cent, of ferrous oxide in Dinas-brick renders it quite useless in the steel-melting furnace. 33. Bauxite Bricks are formed by mixing the calcined bauxite with from 6 to 8 per cent, of some binding material such as clay and plumbago, whereby, upon the application of intense heat, the plumbago partially reduces the iron of II.] FIRE-CLAYS. 17 the bauxite, and the brick so produced becomes practi- cally infusible. Where such bricks can be applied, they are much more durable than the best fire-bricks; they resist the most intense heat, as also the action of basic slags ; after heating for some time they become intensely hard, and then also resist strongly the mechanical action of wear or abrasion. 34. Fire-clays are such as will withstand exposure to a high temperature without melting or sensibly softening. As already noted, they are essentially hydrated aluminous silicates, with more or less lime and magnesia in the form of carbonates, iron as pyrites (FeS 2 ), free silica (Si0 2 ), smaller quantities of potash (K 2 0) and soda (Na 2 O), with water in both the combined and hygroscopic form, as is shown by the following AVERAGE ANALYSES OF VARIOUS WELL-KNOWN FIRE-CLAYS. Con- Stour- bridge Clay. South Wales Clay. tinental Clay used for Fire- Dinaa Clay. bricks. Silica 63-30 67-12 66-10 96-73 Alumina . 23-30 21-18 19-80 1-39 Potash __ 2-02 | Soda - I 20 Lime 73 32 19 Magnesia 84 Ferrous Oxide (FeO) 1-80 48 Ferric Oxide (Fe 2 3 ) 1-85 6-30 Water Combined . ^ Hygroscopic . I Organic Matter . J 10-30 4-821 1-39 I 90 J 7-50 50 99-43 100-44 99-70 99-49 The value of a fire-clay largely depends upon its free- dom from such bodies as calcic carbonate (CaCO 3 ), iron pyrites (FeS 2 ), and ferrous oxide (FeO), any of which at high temperatures would readily combine with the free 1 8 STEEL AND IRON. 1C tap. IL silica (Si0 2 ) of the clay, with the formation of readily fusible vitreous silicates. The presence of 3 or 4 per cent, of foreign oxides in a siliceous clay that is, such as contains much free silica will render it fusible ; but if the clay be aluminous, then, owing to the in- fusibility of most aluminates, even 6 or 7 per cent, of ferrous oxide does not destroy its refractory quality ; hence, wherever a scouring basic slag has to be en- countered, an aluminous clay as free as possible from silica is desirable. The presence of alkalies in sensible amount as 1 per cent, or upwards materially impairs the refrac- tory character of the clay. Oxide of iron also has a strong fluxing effect, and 2 per cent, or upwards affects the fusibility of the clay, although if alkalies be absent, then 3 per cent, of ferrous oxide does not very seriously affect fire-bricks, except at the very highest temperatures. 35. Fire-clays occur most largely in the Coal Measures of the carboniferous strata ; also, though less frequently, in various other geological formations. Clays obtained from the same locality and apparently of the same kind are found to differ widely in their degree of fusibility, arising from variations in the proportions of the free and combined silica, from the influence of free silica as explained in the preceding paragraph, and also from the substitution of small quantities of one metallic oxide for another ; thus a clay containing magnesia (MgO) is rendered more fusible if a little lime (CaO) be substituted for a certain proportion of the magnesia. Further, the power to resist heat is influ- enced by the molecular condition of the particles of the clay in a manner but imperfectly understood, as also by the presence of organic matter, and by the mechanical arrangements of its particles generally the coarser the particles the more refractory will be the material. 36. Fire-bricks should withstand 1 continued exposure to the highest temperatures of a furnace without decomposi- tion, cracking, fusing, or sensibly softening; 2 they should bear considerable pressure whilst heated without suffer- ing fracture or distortion ; 3 they should be unaffected Chap. EL] FIRE-BRICKS. 19 by considerable, and sometimes sudden, variations of tem- perature; 4 for certain applications they require to be unaffected by contact at a white heat with such metallic oxides as those of iron and magnesia, or other basic slags or scoriae ; 5 contact with heated fuel should be with- out effect upon them ; 6 they should be able to resist at one time an oxidising, and at another a reducing, action ; 7 for commercial considerations, fire-bricks are re- quired to be regular in shape and uniform in quality. Bricks combining all these qualities are rarely to be met with; thus the Dinas and other silica bricks to be sub- sequently described, whilst serving admirably for the con- struction of reverberatory furnace-roofs, where the bricks do not come into contact with metallic oxides or scorise, would be quite worthless (owing to the large proportion of free silica entering into their composition) in the bottom of a furnace upon which iron or steel was to lie molten for any lengthened period. 37. In the manufacture of fire -bricks, their constituent fire-clays cannot be used directly asth'ey are found that is, in the raw state since, although the clay may be sufficiently refractory for the purpose intended, yet when subjected to rapid alternations or changes of temperature, or even in the drying of the bricks after being moulded, they are found to split or crack. To obviate this difficulty without also impairing the refractory nature of the clay, the raw clay is first tempered or exposed for some time to the action of the atmosphere before moulding into bricks, and other materials also such as previously burnt fire-clay, old bricks, graphite in powder, small coke, crushed quartz, or siliceous sand (as may be required for the particular purpose to which the bricks are to be applied), are also mixed with the clay. Where resistance to extreme heat only is required, then an excess of silica is preferable in the clay, but if scouring basic slags are also to be encountered, then graphite, coke, or materials of that class, are added. 38. For brick-making, the fire-clay, as just noted, is 20 STEEL AND IRON. [Chap. II first exposed under sheds to the atmosphere, but protected from the weather, and is then, either alone or in admixture with such substances as above named, ground between rolls or under edge stones to a fine powder, which is then mixed with water and thoroughly incorporated in a pug-mill ; after which the mixture is moulded into bricks by machine or hand labour, as in the case of ordinary bricks. The bricks are then laid out to dry, and, when sufficiently dry and resisting are placed in kilns, each holding from 15,000 to 20,000, arranged so as to allow of the heated gases from the combustion of the fuel burning on a grate at the end of the kiln to circulate around and between them ; the bricks after some six days' exposure in this manner are then suffi- ciently burnt and ready for withdrawal, for which purpose the fires are withdrawn, and the kilns allowed to cool down. The shrinkage during the drying and burning of fire-bricks is considerable, so that for the production of a 9-inch brick the raw clay brick will require to be from half-an-inch to three-quarters of an inch longer than the burnt brick ; the exact amount requiring determination for each mix- ture of clay, since the amount of contraction varies for almost every clay or mixture of clays. 39. Fire-bricks must be set in fire-clay and never in lime mortar, otherwise at furnace temperatures the free silica of the clay or brick would combine with the lime of the mortar, to the production of a readily fusible silicate of lime, and the consequent destruction of the furnace. 40. Dinas Brick is a highly refractory brick, made from a fire-clay occurring in the Vale of ISTeath which con- tains 97 per cent, of silica, with about 1|- per cent, of lime, and smaller proportions of alumina, ferrous oxide, alkalies, and water. The brick presents on fracture a yellow matrix, embedding fragments of quartz, giving the frac- ture a rough, hackly appearance. These bricks are employed in the roofs of reverberatory and heating furnaces, where they will withstand a clear white heat, but, as already mentioned, they become perfectly useless whenever they come into contact with oxide of iron. Chap. II.] SILICA BRICKS. 21 41. Silica Bricks, as the name implies, are composed largely of silica, the rock or stone from which they are made by the Landore Siemens Steel Company being the Dinas Rock of the Swansea Valley, yielding 98 per cent, of silica, the remaining 2 per cent, being chiefly alkaline matter. For their manufacture the stone is first broken up into a suitable size for crushing under rolls weighing some three tons each, and during the crushing under the rolls lime cream (a thin paste of lime and water) is also added to the pan for incorporation with the ground silica ; and in this manner about half-a-hundredweight of lime is added to each ton of silica stone. The mixture so ob- tained is pressed into moulds somewhat smaller than the burnt bricks are required to be, the bricks being usually hand-made to the various shapes and sizes needed in furnace construction. The bricks, which are now very tender, are carefully placed for drying upon a floor heated by steam, when, after thirty-six hours' exposure, they are stacked in bee-hive ovens or kilns, each holding about 35,000 bricks, and are there heated or burnt during about five days, from whence, after the cooling down of the kiln, which occupies another five or six days, the kilns are opened and the bricks withdrawn. The bricks are still tender or brittle in comparison with ordinary bricks, and require considerable care in transport, and need to be kept from any lengthened exposure to rain or wet. They are of a light yellowish-brown colour, with a coarse, irregular, granular fracture, and are highly refractory ; they are used most extensively for the roofs, ports, and other parts of the Siemens Open Hearth steel-melting furnace, where the most intense heat occurs. For these purposes the bricks made by the afore-mentioned company are not only sup- plied to the various English steel works, but are exported largely to America, and elsewhere. Silica bricks expand in burning, so that a brick about eight and three-quarter inches long before burning comes out nine inches long after burning, whilst a considerable further expansion occurs 22 STEEL AND IROW. [Chap. H. when the bricks are heated to high temperatures, followed by a corresponding contraction on again cooling ; and hence it becomes necessary on first heating furnaces where these bricks are used, to loosen the tie-rods, and to tighten them up again as the furnace cools; or the same purpose is effected by affixing powerful springs between the buck- staves of the furnace and the nuts on the tie-rods, to compensate and allow for the expansion and contraction of the roof during its working. If the furnace castings and tie-rods are sufficiently strong to resist the pressure pro- duced by the expansion of the bricks, then the roof itself rises and falls in the crown as it is heated and cooled. These bricks cannot be set in a lime mortar, but are set with the smallest possible quantity of a paste of silica sand, or of silica cement and water. Silica bricks, as already explained, are invaluable for resisting the high temperature in the roof of the Siemens furnace, but for the hearths of furnaces, cupola linings, &c., exposed to the contact of metallic oxides, an aluminous brick is preferable. ANALYSES OF FIRE-BRICKS, SILICA-BRICKS, GANISTER. * Glenboig Fire- brick. Newcastle Fire- brick. Silica Brick, Dowlais. Sheffield Ganister. Silica . 62-10 58-00 97-5 89-04 Alumina . 33-10 36-50 1-4 5-44 Ferric Oxide . 3-00 1-67 0-55 2-65 Lime 0-90 0-50 0-15 0-31 Magnesia . trace 0-90 0-10 0-17 Jfotaah . 090 2-12 Soda _ 0-30 Loss in Calcination 2-30 100-00 99-99 99-70 99-91 * Proceedings of the Iron and Steel Institute. Snelua : Refractory Materials. Chap. TL.1 GAX1STER. 23 42. Siliceous Sand is an exceedingly refractory material, containing in some varieties as much as 97 per cent, of silica, the remainder consisting of a little lime, alumina, oxides of iron and water. This sand is used for mixing with fire-clays, &c., in the manu- facture of fire-bricks, also as the principal ingredient hi the mortar used in the setting of silica bricks it is also employed in making the bottom or hearth of the Siemens Melting Furnace. Sands less pure than the above are also employed for making the pig-beds of blast furnaces, and by the moulder in making his moulds for castings in cast-iron. Though highly refractory, yet, owing to the absence of all binding qualities, sands are not available for most of the applications to which fire- bricks are applied. 43. Firestones, sandstones, granites, millstone-grit, serpentines, steatites, conglomerate, and other siliceous or quartzose rocks, are sometimes highly refractory, and will stand considerable changes 01" temperature without cracking ; hence such rocks are frequently employed for the hearth-stones of blast furnaces, the boxes of the cementation furnace (see p. 407), and also in the con- struction of reverberatory furnaces. But amongst the causes which limit the use of the rocks in furnace con- struction are the want of homogeneity in the rocks, the frequent presence of notable quantities of lime, oxide of iron, iron pyrites, &c., which decrease the infusibility of the stone and also the stratification in the sandstones, which necessitates special care that the stones be bedded in the planes of stratification, to prevent exfoliation on the application of heat. 44. G-anister is a siliceous rock in which the silica is cemented together by argillaceous matter, and, with- out any admixture, the rock has usually sufficient cohesion to hold together after being simply rammed around a wooden model of the interior of the furnace, in the manner described when speaking of the crucible steel -melting furnace, and of the ordinary Bessemer 24 STEEL AND IRON. [Chap. II, Converter. The ganisters used for these purposes, also, whilst binding fairly well together, do not shrink much on heating. 45. Crucibles are open-mouthed vessels, which are capable of being moved to and from the furnace by means of tongs, and in which steel or other metals may be exposed to the high temperatures required for their fusion. It is necessary that crucibles should possess in the highest degree all the qualities required of good fire-bricks, such as the power to resist a continued exposure to the high temperature of the steel-melting fur- nace without softening, or becoming tender, or suffering any distortion of shape ; they should not crack or split by sudden alternations of temperature ; they should not be affected, save in the slightest possible degree, by contact with incandescent fuel, as coal or coke, or by the slag and ashes produced on their combustion. They should, further, be capable of withstanding the corrosive action of the manganous oxide (MnO) resulting from the oxidation of the manganese in the spiegeleisen or ferromanganese, added to the crucible charge in the production of crucible, or, as it is commonly called, cast-steel; and moreover, the crucibles should be sufficiently strong to support the weight of the molten metal when lifted by tongs from the furnace. Crucibles usually the better resist the corrosive action of slags, according as they are more regular in texture, and according to the fineness to which the constituents have been ground, but under these same conditions the tend- ency to crack is increased. 46. The smaller crucibles known, according to their shape, as Cornish, London, Hessian, and FrencJi respec- tively, are made from certain mixtures of fire-clay and sand suitably prepared, then moulded to shape, dried, and kiln- burnt ; but they are only used for laboratory experiments by assayers and chemists. A brasqued crucible is one of the above-named in which a lining or brasque of carbonaceous matter has been introduced ; * the brasque of the larger- * See the author's "Manual of Metallurgy," Vol. L Chap. II.] STEEL-MELTING CRUCIBLES. 25 Fig. 4. Steel-melting Crucibles, Cover and Stand. sized crucibles is formed of anthracite powder, powdered gas-carbon, and gas- tar. 47. The crucibles employed by the steel melter are of the form and proportions shown at s, Fig. 4. They measure from 16 to 19 inches in height, are about 9 inches in diameter at the widest part, and from 6 or 8 inches in diameter at the mouth ; they are capable of holding charges of about 75 pounds of bar- iron or blister-steel, previously sheared into small pieces, and which when melted occupy a little more than one-half of the capacity of the crucible. These crucibles when in use are placed upon a conical foot or stand (Fig. 4, d) for raising the pot above the fur- nace bars, and also to enable the hole in the bottom of hand-made crucibles to be stopped with sand* before metal is charged into them. After the charge has been introduced into the crucible the mouth is covered by a loose lid, c ; this and the stand d being made also of fire- clay, but of a somewhat cheaper variety than the pots them- selves. It is the practice on the Continent, where machine- made pots with solid bottoms are employed, to provide the lid c with a loose stopper, a. The charge is introduced into these latter crucibles before they are inserted into the melting-hole or furnace, in which case the lid is placed in position, and luted on after the charge has been intro- duced, and then it is only necessary to remove the stopper, a, instead of the whole lid, for the inspection of the con- tents of the crucible during the melting process. 48. Steel-melting crucibles or pots, as they are called, require a judicious and careful selection of the fire-clays * See p. 420 26 STEEL AND IRON. [Chap. U. employed in their manufacture, the ingredients also needing to be mixed only in their best proportions. The materials usually employed are fire-clay, both burnt and raw, with graphite and powdered coke ; the burnt clay being obtained by breaking up and grinding to powder the old crucibles, which must, however, be cleared from all adhering slag before being used for this purpose. 49. Many steel melters have their own* mixture for making their pots or crucibles, and also use different mixtures according as the steel to be melted is hard like tool steel, or of the milder quality such as is required for structural purposes ; but all agree in using a mixture of fire-clays rather than a single clay, however celebrated its refractory quality may be ; whilst the addition of coke- dust and burnt clay lessens the tendency of the fire-clay to contract in heating, but a sufficient amount of raw clay is requisite to afford the plasticity necessary for moulding. A usual crucible mixture employed in Sheffield consists of Stourbridge clay, Blue clay, China clay (Kaolin), burnt clay in the form of old crucibles broken up and freed from adhering slag, together with plumbago, and coke-dust ; or, if for melting specially hard steel, the plumbago is fre- quently either omitted or introduced in much smaller quantity. The proportions employed by Mushet in his crucibles for melting steel were : 5 parts of Stourbridge fire-clay, 5 parts China clay or Kaolin, 1 part of old pot, and 1 J part of coke dust. Crucibles made from such mix- tures as the above are tough when hot, and many may be hammered flat without breaking when at the temperature of the steel-melting furnace. 50. Uniformity in fineness of the materials is ensured by first grinding the dry ingredients to an almost impalp- able powder, after which the clays are carefully weighed and thoroughly mixed in the required proportions, either upon the floor, or, as is now more general, in a suitable mill. If the mixture be made upon the floor, water is thrown over the clays, and the whole is thoroughly kneaded together by men trampling or treading with Chap. II.] MANUFACTURE OF CRUCIBLES. ' 27 their bare feet in a systematic manner over the mass during several hours, the clay being period- ically cut up and turned over with the spade during the process ; and it is still usually considered that better results are obtained by treading the mixture than by mixing in the mill. After thorough incorporation by either method, the clay is then cut up and weighed into portions called balls, each sufficient for the produc- tion of one crucible (pot) ; these balls are further worked by hand upon a table or bench before being introduced into the well-oiled and smooth cast-iron mould, or flask, b (Fig. 5), of the external shape of the crucible; the plug, a, is either a hollow casting or a solid plug of lignum vitse, with a pin at its lower end of about five inches in length, which passes through a correspond- , -f . ^ , , /. Fig. 5. Flask and Plug ing hole in the loose bottom plate, /, f g or crucible-making, of the flask and so serves to centre the plug in the mould ; the plug is also made as smooth as possible, and is well oiled before each insertion into the clay in the flask, b. 51. In the manufacture of crucibles by hand, the ball of clay, thoroughly worked, accurately weighed, and prepared in the manner just described for the preparation of a crucible, is then thrown into the flask, b, and the plug, a, is forced into the mass of clay by alternately lifting it up and pressing it down again, the concluding pressure being obtained by striking the plug two or three smart blows with a large wooden mallet. In this manner the clay rises all around the plug, filling up accurately the space between the inner surface of the mould or flask and the body of the plug. Finally, by a dexterous twisting movement of the plug, which is at the same time lifted upwards by a pin passing through its eye-stud, d. STEEL AND IRON T . [Chap. II. it is withdrawn, leaving the clay in the form of the crucible inside the flask. The small surplus clay which rose above the mould as the plug was forced down is then cut away by passing the knife around the top edge of the mould, at the same time slightly inclining it towards the centre as it passes around the cir- cumference ; thus a clean upper edge is left, and the mould is now lifted by the trunnions, c c, and carefully placed with its loose bottom plate upon a small post fixed in the ground (Fig. 6 k), when by allowing the flask to fall the crucible remains in the position shown in Fig. 6. A mould of tin-plate of the form of the fru strum of a cone is then placed around the mouth of the mould, pressing it inwards to the form shown in Fig. 4, and the crucible is then removed by carefully lifting it with the aid of a pair of sheet- iron plates fitting around the sides of the crucible. The crucibles are then placed by the workman upon the shelves in the pot-house, where they are allowed to dry slowly for from twenty -four to forty -eight hours, before they are removed to the shelves around the steel-house against the furnace flues (see Fig, Fig. 6. Form of Crucible 84, p. 4 18), and where the cru- Bibles remain for a further period of at least ten days or a fortnight before they are sufficiently dry and seasoned to allow of their being safely used for the purpose of steel melting. It is, however, considered desirable, wherever possible, that the crucibles should remain for five or six weeks in the stoves, or on the shelves of the steel-house before being used, the slower drying being favourable to the longer duration and the production of a more refractory crucible. Chap. H.] PLUMBAGO CRUCIBLES. 29 52. The operations last described vary somewhat in different establishments ; thus, instead of drying the cru- cibles upon the shelves of the steel-house, in some of the larger works, especially upon the Continent, the crucibles are removed from the pot-house and arranged upon suitable shelves in a series of chambers, where they remain about a fortnight, heated air being in the meantime propelled by a fan through the chambers, whereby the temperature is gradually raised to between 75 C. and 85 C. (167 F. to 185 F.). After drying in this manner, the crucibles may then be removed and intro- duced direct into the furnace without the intermediate process of annealing as described on p. 427. 53. In machine-made crucibles the operations are the same as those above described, except that the plug for forming the inside of the crucible is driven into the ball of clay thrown into the bottom of the mould or flask, and withdrawn by a suitable me- chanical arrangement instead of by hand labour. In machine-made crucibles the centre pin, e (Fig. 5), in the plug, which serves as the guide to centre the plug when first introduced by hand into the mould, and which leaves a hole through the bottom of the hand-made crucible, is unnecessary in a machine in which flask and plug are fixed quite vertical and concentric ; hence machine-made pots or crucibles do not have this hole through the centre of the bottom. 54. In the so-called plumbago crucibles the fire- clays are only added in sufficient quantity to give the cohesion and plasticity to the plumbago necessary to enable it to be moulded into the required shapes. Plumbago crucibles are usually much thicker than the ordinary Stourbriclge clay pots, their surface is also smoother, and particles of metal do not therefore so readily cling or fix themselves to the sides of the pot. Thus for the purposes of melting alloys, such as brass, special mixtures of cast- iron, and the like, they are much superior to the ordinary clay crucibles; but for steel-melting purposes, 30 STEEL AND IRON. [Chap. IIL considering their very much greater cost, their advantage is not so decided, although they withstand a higher tem- perature without softening, and greater alternations of temperature without cracking ; when heated, however, to the temperature of molten steel they are not so tough as the clay crucibles, and are thus considered more dangerous to the puller-out from their greater liability to crush under the pressure of the tongs. CHAPTER IIL ORES OF IRON. 55. ALTHOUGH iron is an ingredient in greater or less proportion of a vast number of minerals and metallurgical products, yet its workable ores do not constitute numerous classes of metalliferous minerals, varying widely in their chemical composition and richness in the metal for which they are to be smelted, like the ores of many of the other metals employed in the arts. But the minerals constituting the workable ores of iron belong to a very limited class, which differ, however, rather considerably in composition and in their richness in metallic iron ; the only minerals worked for the production of iron being such as contain either the oxides or carbonates of iron, accompanied by a gangue, or foreign matters, usually consisting largely of calcareous, siliceous, argillaceous, or bituminous minerals ; and it is upon the nature and quantity of the foreign matter associ- ated with the pure mineral, that the practicability, or other- wise, of profitably working the deposit of ore depends. Thus a haematite iron ore, though rich in iron, if associated with any considerable proportion of a mineral phosphate (as calcic phosphate), or with ferrous sulphide (iron py- rites), would be thereby much reduced in value, or probably useless; whilst 5, 10, or 15 per cent, of manganese in Chap. III.] MAGNETIC IRON ORB. 31 spathic ores, or of carbonaceous matters in a clay iron- stone, would enhance the value of the ore. 56. The sulphides and silicates of iron occur very abundantly as minerals and metallurgical products, but for reasons to be subsequently explained are not available as ores of iron ; and of the oxides of iron used in iron-smelting, the most important are the magnetites, and the red and brown hcematites, whilst the carbonates embrace the spathic iron-ores, and the argillaceous car- bonates known as clay ironstones. 57. The ores of iron also do not permit of the same variety of treatment for the reduction of the metal as is characteristic of many other metals, the only re- ducing agents practically employed in iron-smelting being carbon and carbonic oxide. 58. Iron-ores occur in almost the whole of the geo- logical series, but most abundantly in the older formations, as the Silurian, Devonian, and Carboniferous strata, al- though the brown and argillaceous haematites also occur rather largely in the Oolites of Europe. 59. Native and meteoric iron, the former constituting the hard fine-grained buttons known as " native steel," is sometimes found where coal seams have been ignited in the vicinity of ferruginous deposits; but this and "meteoric iron" are of such comparatively rare occurrence, irregular distribution, and small weight, as not to be considered amongst the ores or sources of iron, as employed in the arts. 60. Magnetic iron-ore or " Magnetite " is the richest and one of the most widely distributed of the ores of iron. The pure mineral is iron-black or iron-grey in colour, gives a black streak, is brittle, magnetic, and sometimes distinctly polar ; it occurs crystallised in the cubic system as octahedra and dodecahedra, but is more generally found in the massive form, yielding a crystal- line or granular fracture ; and it is also found in the form of grains or sand. The composition of magnetite is represented by the formula FegO^, or FegOa, FeO \ 32 STEEL AND IRON. [Chap. when pure it yields 72*41 per cent, of iron, but the ore usually contains only from 80 to 90 per cent, of the magnetic oxide of iron, accompanied with from 5 to 15 per cent, of silica; and it will be noted from the appended analyses that the Swedish magnetites are practically free from sulphur and phosphorus, whilst some contain considerable proportions of manganese. 61. The following are ANALYSES or MAGNETIC IRON-ORE. Danne- mora ore (Ward). Oural ore. Devon- shire (Riley). Pers- Terg. Bisp- berg (Aker- man). British Colum- bia. Ferric oxide (Fe 2 O 3 ) 27-50 68-98 13-00 72-17 68-8 67-31 Ferrous oxide (FeO) 56-80 66-50 2-20 21-7 28-33 Manganous oxide ) (MnO) j 0-24 0-37 0-56 27 0-16 trace Alumina (A^Og) 3-81 3-60 35 _ Lime (CaO) 1-80 1-21 0-56 3-42 Magnesia (MgO) . 80 1-52 8-53 Silica (SiCg . . 13-20 24-76 10-51 Phosphoric anhy- ) dride (P 2 O 5 ) j 0-03 0-57 024 P. -008 0-07 Ferrous sulphide ) (FeS 2 ) 0-04 029 0-09 Water (OH 2 ) . . Insoluble residue . = 3-20 9-40 1-93 TiCyll 3-97 100-34 99-16 98-95 99-433 99-8* Metallic iron . 61-16% 56-66% 53-97% 63-84% - 62. Magnetic iron ore occurs in granite, gneiss, clay- slate, hornblende-schist, and occasionally in limestone formations, and it is also often accompanied by red and brown haematites. It is from these ores (magnetites) smelted with charcoal that much of the famed Dannemora (Swedish) iron is obtained. The ore employed at Danne- mora yields from 25 to 60 per cent, of metallic iron, Chap. IIL] RED HAEMATITE. 33 but the average falls below 50 per cent. ; the ore is accompanied by a gangue, containing silica and lime, in sufficient quantities to permit of its being smelted without the addition of any further flux to the furnace charge. 63. This ore is found in considerable abundance in Norway, Sweden, Piedmont, Saxony, Canada, the United States, Mexico, the Ourals, Siberia, the Island of Elba, in the West of England, in Devon, and in Cornwall. 64. Franklinite is less magnetic than magnetite, which it otherwise closely resembles ; it occurs in the metamorphic Silurian limestones of New Jersey, United States. In New Jersey it is first treated for the extrac- tion of zinc, and the residues so obtained are afterwards smelted for spiegeleisen. Franklinite is a mixture of ferric and manganic oxides (Fe, Mn) 3 O 4 with ferrous, manganous and zincic oxide (Fe, Mn, Zn) O, of which Rammelsberg gives as the average of several analyses 45-16 per cent, of iron, 9-38 per cent, of manganese, 20-30 per cent, of zinc, with 25-16 per cent, of oxygen. 65. Red Haematite is the name applied to a most im- portant class of the ores of iron, which consist essentially of anhydrous ferric oxide Fe 2 O 3 , and which occur of various shades of colour, from deep red to steel-grey, with a crystalline, fibrous, columnar, botryoidal, or amorphous structure; they occur further both in the earthy and the compact form, as also soft or hard, &c. From the variety of their physical characters the red haematites have received special names ; thus, the crystalline variety as occurring at Elba, Brazil, &a, is known to the mineralogist as specular-iron, or iron-ylance, and possesses a bluish or steel-grey colour ; it crystallises in the rhombohedral system, yielding a red streak, and containing, when pure, 70 per cent, of metallic iron. The scaly, micaceous, or foliated variety, which is used as the basis of a paint for iron work, is known as micaceous iron-ore ; and when red haematites assume the form of dull, hard, compact masses, often reniform or kidney-shaped, as occurring in Cumberland, they are then 34 STEEL AND IRON. [Chap. IIL known as kidney ore. The soft and more earthy varieties constitute red ochre, whilst puddler's-mine or ore is the soft, unctuous, compact, earthy form employed for the making and repair of the bottoms of puddling furnaces ; another form of hematite, occurring as small, hard, flattened grains, is recognised as lenticular clay-iron ore. 66. The haematite iron ores, owing to their freedom from sulphur and phosphorus, and to the large proportion of silicon contained in the pig-iron smelted from them, have been in large and increasing demand since the intro- duction of the Bessemer process for the manufacture of steel; for until the recent discovery of the "-basic pro- cess" of Bessemer conversion, only such pig-iron was suitable for the process, and it is now estimated that the gross output of the Furness district alone amounts to nearly one million tons of haematite ore annually. 67. The following table shows the average composi- tion of these ores : ANALYSKS OK RED HAEMATITE IKON OKES. Barrow- Ulver- Ulver- in- Furness Richards) stone (Dick). stone (Spiller). Canadian. Ferric oxide (Fe 2 3 ) 94-88 86-50 94-23 85-037 Manganous oxide (MnO) 0-04 0-21 0-23 Alumina (A1 2 3 ) 0-07 0-51 Lime (CaO) . 0-34 2-77 0-05 Magnesia (MgO) trace 1-46 trace ,___ Silica (Si0 2 ) . 4*55 5-130 Carbonic anhydride (C(X) 2-96 Phosphoric ' (? 2 O^ 0-03 trace trace 0-032 Sulphuric (SO S ) 0-11 0-09 Sulphur (S) . 0-075 Pyrites (FeS,) . / Water (OH 2 ) . 0-47 0-03 0-56 Organic matter Insoluble residue 6-55 5-18 100-56 100-88 Per-centage of iron . 66-42% 60-u5% 65-98% 59-528 Uhap. in.] BROWN HAEMATITE. 35 In the North Lonsdale district the ores average from 52 to 54 per cent, of metallic iron, the highest yielding from 60 to 62 per cent., whilst the poorest contain about 40 per cent. 68. The most important deposits of red haematite are found in the Cambrian, Silurian, Devonian, and Carbon- iferous rocks ; the deposits of North Lancashire, Cumber- land, and Flintshire occurring in veins in the mountain limestones of the Carboniferous series, and although the ore is not magnetic, the veins run more or less north and south. Red haematite is often associated with the brown oxides, and the ore is classed as hard or soft, according as it contains free silica in excess or other- wise. The more important Continental and foreign deposits of these ores occur in Sweden, Norway, South Germany, Canada, and the United States. 69. Brown haematite, or brown iron-ore, is when pure a hydrated ferric oxide, represented by the formula 2 Fe 2 O 3 3 OH 2 , and would thus yield 5 9 -89 per cent, of metallic iron. It has a dull lustre, and varies from blackish- to yellowish-brown, but it affords an invariable yellowish-brown streak. It occurs in irregular, compact, more or less homogeneous masses, in the Carboniferous limestone and lower Coal Measures of the Forest of Dean, Gloucestershire, and Glamorganshire ; whilst a less pure variety, containing more or less mechanically mixed sand, occurs in the Lias, Oolites, and Lower Greensands of Northamptonshire, Lincolnshire, Buckinghamshire, and Oxfordshire ; brown haematites also form one of the most important of the ores smelted in France and Germany. 70. The Spanish mines of Somorrostro, near Bilbao, yield a brown haematite of Cretaceous age, which was probably deposited from hot springs charged with ferrous carbonate, FeC0 3 . This ore in the un dried state yields from 50 to 64 per cent, of iron, with about 1 per cent. of manganese, with only a little sulphur or phosphorus j and distributed throughout are blocks of unaltered spathic ore. 36 STEEL AND IRON. (Chap. 1IL 71. " Bog-iron-ore " is an impure brown haematite, smelted in Canada principally for foundry purposes. Limonite, again, is another form, as are also the so- called "Lake ores," which occur in granular concretionary masses, dredged during the winter months from the bottom of certain shallow lakes of Norway, Sweden, and Finland ; whilst the mineral known as " Gothite " is also a crystallised and rich variety of the brown haematite ores. 72. As previously mentioned, brown haematites vary much, both as regards the per-centage of metallic iron which they contain, and also in their freedom from such impurities as phosphorus and sulphur, whilst manganese is almost always present in those ores, and they are accompanied by more or less earthy matter. 73. As types of the several classes may be taken the following ANALYSES OF BROWN HAEMATITE IRON-ORES. Forest Glamor- North- New Somor- of Dean ganshire ampton- South rostro Somor- (Dick). (E. Kiley). shire (Percy). Wales. (Baker). rostro Ferric oxide (Fe 2 3 ) 90-05 59-05 56-20 60-72 78-80 80-75 Manganous oxide (MnO) / 0-08 0-09 0-20 0-651 8-16 Alumina (A1 2 3 ) . 0-14 trace 2-43 ^ 3-50 3-10 Lime (CaO) . 0-06 0-25 0-49 I 11-175 trace 0-82 Magnesia (MgO) . 0-20 0-28 0-17; trace 1-04 Silica (Si0 2 ) . 0-92 34-40 29-09 12-66 5-55 3-24 Phosphoric anhy- ) dride (P 2 5 ) j 0-09 0-14 0-84 trace trace Sulphuric anhy- 0-OfiR dride (S0 3 ) ~~~ -. UUo Sulphur . traces 0-075 trace Pyrites (FeS 2 ) Water (combined) . (hygroscopic) 9-22 0-09 6-14} 0-24 j 10-90 13-77 1-60 11-653 2-90 Metallic iron . . 63-04% 41-34% 39-34% 42-5% 55-16% 56-52% Cbap. in.] SPATHIC IRON ORES. 37 74. Titaniferous iron ore, or Ilmenite, occurs massive, but is found more generally as a dark-coloured or black sand along the shores of the Bay of Naples, the North-east coa'st of America, Labrador, New Zealand, &c. In these districts certain ferru- ginous crystalline rocks suffer disintegration, and the lighter portions are washed away, whilst the heavier titaniferous particles, or grains, constituting the bluish iron sands, accumulate upon the shore in sufficient quantity to be collected, and, after a preliminary mechanical treatment, to be smelted in the American Bloomery Furnace for the production of wrought-iron direct from the ore. The titaniferous sands contain a large proportion of magnetite, besides titaniferous iron- ore, and these are usually accompanied by free silica, with more or less magnesia. Titaniferous iron ore is a most refractory mineral, and, on account of its fine state of division, is difficult to treat in the blast furnace, but it has been used with some success as a lining material for the several forms of revolving puddling and other furnaces. 75. Spathic iron ores, Siderite, Clay ironstones, Blackband, and Cleveland ironstone are the names given to certain classes of the ores of iron, in which the metal occurs as a ferrous carbonate (FeCO 3 of greater or less purity, and from which nearly two-thirds of the total weight of the pig-iron produced in Great Britain are smelted. The purer varieties are described as spathic ores, whilst the amorphous argillaceous ores of the Coal Measures are known as clay ironstones, and when largely impregnated with carbonaceous or bituminous matter they constitute blackband ironstone. 76. Spathic ore in its purest form constitutes the crystallised mineral known as Siderite, which, when pure, yields 48*27 per cent, of metallic iron. Siderite occurs as a mineral having a pearly lustre, and varying from yellow to brown in colour, but when it occurs in veins exposed to water and atmospheric influences, it is usually found to have suffered decomposition, and tc 38 STEEL AND IRON. [Chap. Ill have become converted into brown haematite to a considerable depth from the surface. Spathic ores often contain considerable quantities of manganous oxide, as is the case with the spathic ore of the Brendon Hills, in Somersetshire, which ore has been in recent years extensively transported to Ebbw Vale, South Wales, to be smelted for the production of the manganiferous pig-iron known as spiegeleisen. The other more important associates of spathic ores are calcic and magnesic carbonates, with occasionally also quartz, with copper and lead in small proportion. This ore occurs in the Carboniferous rocks of Durham, Corn- wall, Devon, and Somersetshire, but more largely on the Continent, as in the mountain masses of Siegen and Musen, in Rhenish Prussia, where it is found in rocks of Devonian age ; at Thuringia, in Hungary, it occurs in Permian rocks ; whilst extensive deposits also are present in Styria, Westphalia, Lolling, and Carinthia, in Austria, as also in Hanover and in Russia. 77. Clay ironstone is the argillaceous, amorphous, compact, or earthy variety of ferrous carbonate, occurring either in detached nodules, or in layers of nodular concre- tions, distributed through the shales and clays of the Coal Measures, or in beds of considerable thickness in Liassic rocks. When not discoloured by admixture with carbonaceous matters or by atmospheric decomposition, it ranges in colour from light grey or yellow to brown, but the lighter-coloured varieties rapidly become brown on exposure to the atmosphere ; and, like Siderite, it contains besides ferrous carbonate, appreciable quantities of calcic, magnesic, and manganous carbonates, along with clay (aluminous silicate), phosphoric acid, iron pyrites (FeS 3 ), and occasionally also other minerals, as blende (ZnS) and galena (Pb S). The principal localities of its occur- rence are the clays and shales of the Coal Measures of North and South Staffordshire, Derbyshire, Yorkshire, Warwickshire, Shropshire, North and South Wales. Denbighshire, and in Scotland. III.] CLEVELAND IRONSTONE. 39 78. Blackband ironstone is a clay ironstone, con- taining from 15 to 25 per cent, of bituminous, coaly, or other carbonaceous matter, which gives it almost the appearance of ooal ; it occurs in beds most largely in Lanarkshire and Linlithgowshire, to a smaller extent in North Staffordshire, and also in South Wales. Owing to the large amount of carbonaceous matter contained in this ore, it can be calcined in heaps without the addition of any further fuel, and the calcined product will yield from 50 to 60 per cent, of metallic iron. ANALYSES OP SPATHIC AND OTHER IKON-ORES. Spathic ore, from Somerset- shire (Spiller). Clay iron- stone from Dudley (Dick). Black- band, Scotland (Colqu- houu). Cleveland Ironstone (Dick). Ferrous oxide (FeO) . 43-84 45-86 40-77 39-92 Ferric oxide (Fe 2 3 ) 0-81 0-40 2-72 3-60 Carbonic anhydride (C0 2 ) 38-86 31-02 26-41 22-85 Manganous oxide (MnO) . 12-64 0-96 0-95 Alumina (A^C^) 5-86 7-86 Lime (CaO) . 0-28 1-37 0-90 7-44 Magnesia (MgO) . . , - 3-63 1-85 0-72 3-82 Potash (K 2 0) . 0-27 Silica and insoluble residue 0-08 10-68 8-76 Clay .... 10-10 Phosphoric anhydride ) ft> r\ \ _ 0-21 __ 1-86 (^2^5) ) Pyrites (FeS 2 ) . _ o-io _ 0-11 Water (OH 2 ) . 0-18 1-08 1-00 2-97 Organic matter . 0-90 17-38 100-32 100-29 100-00 100-41 Metallic iron . 34-67% 35-99% 33-57% 33-62% 79. Cleveland ironstone is a less pure variety of the argillaceous ferrous carbonate, taking its name from the district of Cleveland, in the North Riding of Yorkshire, 40 STEEL AND IRON. [Chap. TV. where it is most largely found. It varies in colour between dull bluish-yellow and dark blue, becoming in some specimens almost black; but the darker varieties often contain sensible proportions of ferrous silicate. Owing to the large proportion of phosphates contained in the Cleveland ironstone, it was, until the invention of the Thomas-Gilchrist or basic process for the manufacture of Bessemer steel, used solely* for the production of foundry and forge qualities of pig-iron; but it is now possible, by means of that process, to largely eliminate the phosphorus from the pig-iron during the Bessemer conversion. This inferior class of ore has been rendered available for the manufacture of pig-iron suitable for conversion into Bessemer steel. CHAPTER IV. METALLURGICAL CHEMISTRY OP IRON. 80. PURE metallic iron, as already stated, is a body difficult of preparation, especially in the compact state, except by purely chemical methods only applicable to laboratory operations, and the pure metal cannot there- fore be considered as a substance of practical commercial importance ; but in combination with variable but small proportions of carbon, and other metallic and non-metallic elements, such as sulphur, silicon, phosphorus, manganese, &c., it constitutes the various qualities of pig-iron, steel, and malleable iron. 81. Pure iron is prepared by the electrolysis of ferrous chloride (Fe C1 2 ), by the reduction of ferric oxide (Fe 2 O 3 ), or of ferrous chloride, by heating either of them to redness in a tube through which a current of hydrogen gas is passed ; or in a nearly pure state it can be obtained by the fusion under a layer of glass free from metallic oxides, of Lbap. IV.] PURE IRON 41 fine iron wire or iron filings, with artificially-prepared magnetic oxide of iron. Iron as prepared by the last method is a metal varying in colour from bluish-grey to silver whiteness according to the state of its aggre- gation ; as reduced from ferric oxide by hydrogen, it forms a grey powder, which is pyrophoric (that is, takes fire spontaneously on exposure to the atmosphere) if the temperature employed in its production has not exceeded dull redness ; but it no longer possesses this quality if the temperature employed in its preparation has exceeded this limit. Electro-deposited iron absorbs or occludes hydrogen to the extent of from seventeen to twenty times its own volume, and it appears probable, as will be subsequently noted, that the combinations of iron with carbon, such as cast-iron and steel, also possess this quality when the metal is in its fused state. As obtained from ferrous chloride (FeCy, the metal yields well-defined cubical crystals, and the metal is always crystalline after fusion, although a fibrous structure is developed by hammering or rolling. Iron is capable of receiving a high polish, it is very tenacious, ductile, and malleable, the last quality being unaffected by heating and subse- quent rapid cooling, neither is it hardened by this treat- ment. Pure iron is one of the best conductors of electricity, but this property is impaired as the iron becomes more and more impure. It can be magnetised to a very high degree, but rapidly loses its magnetism. Pure iron is softer than the commercial varieties of malleable iron, and has a specific gravity of 7 '87. Its fusing point does not appear to have been accurately de- termined, for whilst Pouillet estimates it at from 1500 C. to 1600 C. (2732 Fahr. to 2912 Fahr.), Scheerer gives it as 2100 C. (3812 F.), but the presence of small quan- tities of carbon in combination with the metal rapidly lowers the fusing point. 82. Iron is unaffected by dry air at ordinary tempera- tures (except in the pyrophoric or spongy state already described), or in perfectly pure water free from air, oxygen, 42 STEEL AND IRON. [Chap. IV, or carbonic anhydride ; but if exposed to a moist atmos- phere, then the oxidation commonly known as rusting rapidly proceeds, especially if carbonic anhydride be also present, as is usual, in the atmosphere. The presence of carbonic anhydride appears essential to the oxidation of the iron by moisture, since the metal may be kept bright for almost any length of time in pure lime water, or in a solution of soda. Under the joint influence of moisture, oxygen, and carbonic anhydride, ferrous carbonate is first produced on the surface of the iron, but this, by absorbing a further proportion of water and oxygen, becomes changed to a hydrated ferric oxide, with the liberation of carbonic anhydride, which latter then reacts upon a fresh portion of the iron in the presence of water and oxygen, and a further quantity of ferrous carbonate is produced, and so the cycle continues to be repeated. Further, the hydrated oxide, or rust, is electro-negative with respect to the metallic iron upon which it is formed, and the electrical condition thus resulting still further promotes the affinity of the metal for oxygen ; and the corrosion of the iron thus proceeds rapidly, even to the extent of enabling the iron slowly to decompose water with the evolution of hydrogen at ordinaiy temperatures. Water holding carbonic anhy- dride in solution, even though free oxygen may be absent, rapidly attacks and oxidises metallic iron. Iron, when heated to redness in contact with air or oxygen, is rapidly oxidised, with the production of a black scaly oxide readily detachable from the surface of the iron. This oxide constitutes, on the large scale, the hammer scale or hammer slag of the forge. Iron at a red heat decom- poses water with the liberation of hydrogen. 83. Hydrochloric acid attacks metallic iron with the formation of ferrous chloride (Fe C1 2 ) and the liberation of free hydrogen. Concentrated sulphuric acid (H 2 SO 4 ) also attacks the metal with the liberation of sulphurous anhydride (S0 2 ), whilst ferrous sulphate (Fe SO 4 ) remains in solution ; but if the diluted acid bo employed, then Chap. IV.] OXIDES OF IRON. 43 hydrogen is liberated, and ferrous sulphate remains as in solution as before. The action of nitric acid upon iron, at the ordinary temperature, varies with the degree of con- centration of the acid. Thus, ordinary nitric acid attacks iron vigorously with the evolution of nitrous fumes in. abundance, but if the acid be dilute there is no sensible escape of gas, but ferrous nitrate (Fe2N0 3 ) and ammoniac nitrate (NH 4 NO 3 ) occur in solution ; thus (10 HNO 8 + 4 Fe = 4 (Fe, 2 NO 8 ) + NH 4 NO 2 + 3 H 2 O) strong-fuming nitric acid is without action upon the metal, a bright surface of which may be introduced into the cold concentrated acid without inducing any chemical decomposition, in which case the surface of the metal on immersion assumes a dull whitish appearance, and no further action ensues, the metal having assumed what is known as the passive condition. The atomic weight of iron is 56, and its chemical symbol is Fe. 84. Oxides of iron. As noted in section 82, iron is not acted upon by exposure to dry air or oxygen at ordinary temperatures, but if exposed to these gases at a temperature approaching to redness, then oxida- tion rapidly enues with the production of a scale or slag known as "hammer scale," which is not, however, uniform in either composition or in physical characters. The outer layer of scale is found to be strongly magnetic, almost metallic in lustre, brittle, fusible only at the highest temperatures, more highly oxidised, and some- what redder in colour than the inner layers, which are less lustrous, spongy, tougher, and less magnetic than the outer layers. 85. Magnetic oxide (Fe a 4 ) is, as just noted, the oxide of iron entering most largely into the composition of hammer-scale or hammer-slag, but this scale contains besides magnetic oxide, a variable excess of ferric oxide (Fe 2 O 3 ), and hence, the varying physical qualities of hammer-scale mentioned in the preceding section. Mag- netic oxide of iron also results when iron is exposed at a red heat to the action of aqueous vapour ; and this oxide 44 STEEL AND IRON. [Chap. IV. also remains when ferrous carbonate (FeCO 3 ) is heated to redness in contact with the atmosphere ; as also, according to Kuhlman, when a mixture of ferrous sul- phate (Fe S0 4 ) and calcic chloride (Ca CL,) is heated in a covered crucible ; whilst Ebelmen states that it results as one of the products obtained by exposing ferrous silicate to the action of heat. Magnetic oxide occurs native (p. 31) as a black lustrous mineral known as magnetite. 86. Ferric oxide (Fe 2 O 3 ) is a very stable and practically fixed oxide of iron, decomposable however at a white heat, with the liberation of oxygen and the production of the magnetic oxide (3 Fe 2 O 3 2 Fe 3 O 4 + O). Ferric oxide is produced when ferrous sulphate is strongly heated, the salt suffering decomposition with the elimina- tion of sulphurous anhydride (SO 2 ) and sulphuric anhy- dride (S0 3 ), whilst a bright red pulverulent powder, forming the "rouge" or "colcothar" of commerce, is obtained, which has the composition of ferric oxida Ferric oxide is decomposed until the reduction of metallic iron by heating it in a current of carbonic oxide (CO), hydrogen, ammonia (NH 3 ), or cyanogen (CN), or by heating it along with carbon. Ferric oxide after ignition is only slowly acted upon by either hydrochloric, nitric, or sulphuric acid, but previous to ignition it is readily soluble in these acids with the production of stable ferric salts ; if heated with an excess of sulphur, sulphurous anhydride (S0 2 ) is evolved, and ferrous sulphide (FeS) is obtained. 87. Ferric oxide is prepared in the laboratory by heating ferrous nitrate, oxalate or sulphate, or a mixture of ferrous sulphate and sodic chloride; whilst it occurs in nature in sufficient abundance to be worked as an ore of iron under the forms of haematite, iron-glance, specular- iron, micaceous iron, &c., as previously described when speaking of the ores of iron. This oxide is used in the arts for giving the purple and orange-yellow tints re- quired in the manufacture of glass and porcelain. Cbap. IV.] FERROUS OXIDE. 45 88. The hydrated ferric oxide (Fe 2 O 3 ,3H 2 O) is the most stable of the hydrated oxides of iron, and occurs native as brown haematite, Limonite, and Gothite. As the freshly-precipitated oxide obtained by adding potash, soda, or ammonia, to a solution of a ferric salt, it is an amorphous, brownish-red body, readily soluble in acids, and even slightly soluble in water containing carbonic anhydride in solution. It has the composition indicated by the above formula, but after remaining precipitated for some time it loses a portion of its water of com- position ; or by boiling with water during six or seven days, it loses two equivalents of its water of composition, retaining but one equivalent, assuming thereby a more brick-red colour, and becoming only slightly soluble in the mineral acids. 89. Iron rust is essentially hydrated ferric oxide, pro- duced on the exposure of metallic iron to the joint action of air and water, but more rapidly if carbonic anhydride be also present in the manner described (p. 42). 90. Ferrous oxide (FeO) constitutes the third oxido of iron of any metallurgical importance, since, in com- bination with carbonic anhydride, silica, or sulphuric acid, it yields the more important salts of iron, and forms also the base of several of the iron ores. Thus clay- ironstone contains eighty per cent, of ferrous carbonate, and it exists in a still larger proportion in the crystallized ores such as Siderite or spathic iron ore, whilst in com- bination with silica, constituting it ferrous silicate (2 FeO, SiO 2 ), it enters largely into the composition of the various slags, cinders, &c., produced in the metal- lurgical treatment of iron. 91. Ferrous oxide, both in its anhydrous and hydrated forms, is however a very unstable body, rapidly passing to a higher state of oxidation by exposure to tho atmos- phere. The hydrated oxide or ferrous hydrate is precipitated as a white flocculent precipitate, when potash or soda is added to a solution of a ferrous salt; but the precipitate rapidly changes, however, from white 46 STEEL AND IRON. fChap. IV. to green and then to brown, owing to the absorption of oxygen. The anhydrous oxide, according to Debray, may be prepared by passing steam and hydrogen in definite proportions, over heated ferric oxide (Fe 2 O 3 ), when the oxide in question is obtained as a black, amorphous, non- magnetic, and very unstable body. 92. A fourth oxide constituting ferric anhydride, which in combination with water is known as ferric acid (H, r FeO 4 ), is not of metallurgical interest, since it has never been obtained in the free state ; and its alkaline salts, which result in small proportion when nitre and iron filings, or nitre and ferric oxide, are heated to dull redness in suitable proportions, are very unstable salts, rapidly and spontaneously decomposing with the libera- tion of oxygen and the separation of ferric oxide. 93. Iron and carbon, by their union in various pro- portions, modified by the presence of small quantities of silicon, manganese, sulphur, phosphorus, &c., and by the conditions as to combination or mechanical diffusion in which the carbon exists in the iron, practically determine the several grades of pig-iron, steel, and malleable iron. The essential constituents, however, of these commercial modifications of iron, are, as before stated, iron and carbon, Although iron does not combine with carbon at ordinary temperatures, yet their union when brought into contact at or above a red heat may be readily effected, both directly and indirectly, with the formation of compounds less highly carburised than pig-iron. Thus, by exposing malleable iron for some days to a temperature at or above a red heat, say 1,000 C. to 1,200 C. (1,832 Fahr. to 2,192 Fahr.), to the action of either carbon in powder, or of other carbonaceous materials, in closed vessels, as in the ordinary manufacture of blister or cement steel by the process of cementation (p. 406), it is found that a union of the carbon and iron gradually takes place, the iron bars becoming more highly carburised than the original metal ; the carburisation proceeding from the surface towards the middle of the bar, and penetrating farther Chap. IV.] CAST- OR PIG-IRON. 47 into the bar the longer the temperature and contact are EQ ain tained. 94. Case-hardening, again, is another example of the superficial carburisation of wrought-iron articles, by- heating them to redness for a short time, in contact with leather, horn, or other highly carbonaceous, or some cyanogen, compound. Further, at more elevated tempera- tures, such as those attained in the blast furnace, carbonic oxide (CO), coal gas, volatile hydro-carbons, cyanides, &c., are decomposed by metallic iron, with the carburisa- tion of the latter ; and again, the production of cast-steel by the crucible process is an example of the direct union of carbon and malleable iron, at the more elevated temperature required to melt steel. 95. Cast or pig-iron, which forms the most highly car- burised form of commercial iron, seldom if ever contains more than 475 per cent, of carbon; whilst mild steel con- taining not more than (HO per cent, of carbon is now in daily production, and differs from wrought or malleable iron having a similar content of carbon, rather in the mode of its manufacture and superior tenacity than in its chemical composition. Carbon occurs in pig- or cast-iron under two distinct forms, viz., as dissolved or chemically- combined carbon, and as mechanically-diffused crystalline grapldte, the latter being distributed with considerable regularity throughout the mass of iron. The quality, as well as the class, of pig-iron, as also its applicability to the various purposes to which it can be put, are greatly influenced both by the total amount of carbon present in the iron, as well as by the relative proportions of the combined to the graphitic carbon. Thus cast-iron contain- ing a large proportion of graphitic .carbon, with smaller quantities of carbon in the combined form, is dark grey in colour, breaks with a flaky, crystalline fracture, and is hence known as grey pig-iron; but if the proportions are reversed, and the carbon be largely or almost wholly in solution or chemically combined with the iron, then the pig- is much harder than grey pig-iron, is whiter in 48 STEEL AND IRON. [Chap. IV. colour, and breaks with a coarse granular or crystalline fracture, and such iron is designated as white-iron, a special class of which, usually rich in manganese, being known as spiegeleisen. The white irons are often also the most highly carburised forms of pig-iron. Between the two extreme limits in the relative proportions of graphitic and combined carbon in cast-iron, the gradations are numerous and almost imperceptible, but are attended with a corresponding gradation in the colour and other physical qualities of the metal ; whilst in other specimens the two forms of grey and white iron are distinctly interspersed throughout the same mass, giving the pig- the characteristic dappled appearance peculiar to mottled iron ; and, as will be noted when speaking of the commercial classification of pig-iron (p. 75), manufac- turers are able to classify for the market the produce of the blast furnace, according to its physical qualities, under eight different heads or numbers, from the softest grey to the hardest white iron, each of the numbers being especially suitable for particular applications in the forge or foundry. 96. Mr. G. J. Snelus has shown* that when very grey pig-iron is reduced to powder, scales of graphite can be detached from the crystalline faces of the iron, and also that by sifting and levigating the fine borings of grey iron the graphite can be mechanically separated more or less perfectly. The action of acids upon pig-iron varies with the state in which the carbon exists in the pig- ; thus, upon treatment with hydrochloric acid the metal is dissolved, and any combined or dissolved carbon unites with the hydrogen of the acid to the formation of gaseous and liquid hydrocarbons, of which the latter are very volatile, of a brown colour, and possess a most disagreeable odour , at the same time the graphite or uncombined carbon re- mains along with the silica, as an insoluble residue; hence, when grey cast-iron is thus treated, a large proportion of its carbon remains as graphite in the insoluble residue, * Proceedings of the Iron and Steel Institute, 187L Chap IV.] FERROUS CARBONATE. 49 whilst if white iron be similarly treated, only a small proportion of its carbon remains in the insoluble residue, the greater portion having combined with hydrogen, as above mentioned, and escaped in the gaseous form during the solution. 97. That white cast-iron is a definite carbide of iron of the formula Fe 4 C, which would represent about 5 '08 per cent, of carbon, has been maintained by Karsten, but the evidence advanced does not appear sufficient to warrant the assumption of any such atomic combination occurring in the commercial varieties of pig-iron. Grey pig-iron can be rendered white by a variety of operations ; thu? by rapid or sudden cooling, as by pouring the fluid metal into cold metallic moulds, as in the familiar instance of chill casting ; but under these circumstances the conver- sion into white iron often extends but to a small depth into the body of the casting, and such castings, upon breaking, present a white hard skin enveloping a grey soft interior. When grey cast-iron in mass is allowed to cool slowly from a state of fusion, as in the case of the fluid metal standing in a foundry ladle, a large amount of graphitic matter known as " Kish" separates and rises to the surface as the metal cools, whilst if this same metal be run into moulds and cooled quickly ', the greater portion of this carbon remains unseparated from the iron, thus indicating that the fluid cast-iron is capable of holding in solution an amount of carbon which separates if the metal be allowed to cool slowly. 98. Ferrous carbonate (Fe CO S ) is metallurgically one of the most important salts of iron, since the anhy- drous ferrous carbonate occurs crystallised as Siderite or spathic iron ore, and in its amorphous form it is the usual chemical combination under which a large pro- portion of the iron occurs in the various clay ironstones. When speaking of iron-rust (p. 42), it was explained how ferrous carbonate was first produced when iron was ex- posed to the joint action of atmospheric air or oxygen, moisture and carbonic anhydride (C0 2 ), and how by 50 STEEL AND IRON. [Chap. IV. further exposure the ferrous carbonate was again decom- posed, with the deposition of hydrated ferric oxide, or iron-rust. Ferrous carbonate is slightly soluble in water, but more so in water containing free carbonic anhydride, and this solution on exposure to the atmosphere suffers decomposition, with deposition of the hydrated ferrous oxide as before mentioned. Ferrous carbonate is also decomposed at a red heat in the absence of air or oxygen, with the production of magnetic oxide of iron (Fe 3 O 4 ), and .the liberation of carbonic oxide (CO) and carbonic anhy- dride (C0 2 ) gases, thus : 3 (Fe, CO 3 ) = Fe 3 O 4 + 2 CO 2 + CO. 99. Sulphur and iron, by their union under special chemical conditions, may be made to yield a considerable number of sulphides of iron. The direct combination of sulphur and iron results when these elements are brought into contact under the influence of heat, the combination being attended with a considerable further evolution of heat ; and according to the proportions of the elements present, and to the temperature employed, ferrous sulphide (FeS), ferric sulphide (Fe 2 S 3 ), ferric di- sulphide (FeS 2 ), or magnetic sulphide (Fe 3 S 4 ), or a mixture of these several sulphides, results. The higher the tem- perature employed the lower is the degree of sulphurisa- tion of the products ; also, since ferrous sulphide (FeS) dissolves both iron and sulphur, if either be present in excess, the composition of the body resulting from the heating together of iron and sulphur is exceedingly variable. Mr. Parry has shown that pig-iron heated in a tube filled with the vapour of sulphur absorbs a portion of the sulphur, which it retains even after heating in vacuo during several hours ; and hence it is inferred that sulphur may be in this manner imparted to the metal in the blast furnace, or in other furnaces where sulphurous ores and fuels are employed. 100. The effect of small quantities of sulphur in pig- iron is to make the iron stronger and whiter, and its presence may be thus advantageous in the metal to bo used in the foundry for special classes of castings, such as Chap, rv.] FERROUS XUL^JJIDK. i 51 shot, &c. ; but the presence of very small quantities of sulphur in wrought-iron or steel is attended with the worst results, 0-2 per cent, of sulphur sufficing to produce in iron or steel a marked red-shortness, or impaired malleability at a red heat ; whilst the same metal may be hammered or rolled in the cold state with perfect facility. Since iron pyrites is a frequent impurity in the ores and coal used in the production of iron, it becomes necessary whc-n such ores or fuels have been used to take special care that only such processes are employed for the conver- sion of the pig-iron into malleable iron or steel as will eliminate the sulphur during the process of its con- version, and so prevent the production of red-short mal- leable iron or steel. Pig-iron produced from Cleveland ores usually contains from 0'02 to O'l per cent, of sulphur; but, when forge-cinder is added to the charge of ore in the blast furnace, then it is found that the common forge- pig resulting often contains as much as 0'7 per cent, of sulphur. 101. Ferrous sulphide (FeS) is a usual constituent of the ores of nickel and copper, as in nickel and copper pyrites, but it never occurs free in nature. It can be prepared artificially as previously mentioned by the direct union of sulphur with iron at a red heat ; by heat- ing to redness ferrous sulphate in a charcoal-lined crucible ; by the ignition of hammer-scale with sulphur ; or, by the precipitation of a ferrous salt by an alkaline sulphide. As artificially prepared by the dry methods above enumerated, it forms a very dark brown or black body, having a semi-metallic lustre. It is not sensibly affected by exposure to the atmosphere at ordinary tem- peratures ; but, if heated slightly, as in the operation of roasting, it suffers partial oxidation and ferrous sulphate results, whilst, at a higher temperature, the latter salt is decomposed with the production of feme oxide (Fe 2 O 3 ) and the liberation of sulphurous and sulphuric anhydrides; and, if the ferrous or ferric sulphate and ferrous sulphide be present in the mixture 52 STEEL AND IRON. [Chap. IV. in equivalent proportions, then, upon strongly heating the mixture, the whole of the sulphur from both the sulphide and the sulphate escapes as sulphurous anhy- dride, and ferric oxide alone remains. When heated with carbon, ferrous sulphide is but slightly acted upon ; or, if ferric oxide be substituted for the carbon, then a portion of the sulphur is eliminated as sulphurous anhydride, but there is no reduction of metallic iron. Ferrous sulphide is not affected by heating with silica alone, but if carbon be also present then the ferrous sulphide suffers decomposition largely. 102. Ferrous disulphide (FeS 2 ) constitutes the familiar brass-yellow mineral occurring in radiated fibrous masses, having a strong metallic lustre, and known generally as yellow iron pyrites, cubic pyrites, or mundic ; also ; in its softer and whiter form, as marcasite, or white iron pyrites. Heated with access of air, iron pyrites is decomposed with the evolution of sulphurous anhydride (S0 2 ), in which way it is commonly employed as the source of sulphurous anhydride in the manufacture of sulphuric acid, whilst the residues so obtained, and known as " Bl&e Billy" are used as a fettling for the puddling furnaces in the Cleveland district. 103. Magnetic pyrites or pyrrhotine occurs native, associated like the other sulphides of iron with the ores of nickel and copper, but it has no special metal- lurgical importance. 104. Iron and phosphorus unite with the utmost facility under the influence of heat, producing readily fusible phosphides of a grey colour. A ferrous phos- phide also results when ferrous .phosphate is heated to a high temperature along with carbon. Pig-iron also absorbs phosphorus when heated in the vapour of the latter. 105. The chemistry of the numerous definite phos- phides of iron that can be prepared by purely chemical methods is not of metallurgical importance, although the presence of very small proportions of phosphorus in any Cliap. IV.] PHOSPHORUS AND IRON. 53 of the commercial forms of iron, whether as pig-iron, malleable iron, or steel, is attended by important and usually most injurious results. In the blast furnace almost the whole of the phosphorus present in the ores and fuels of the furnace-charge passes into the pig-iron produced, unless the furnace be working upon a highly basic slag or scouring cinder containing much iron, when a portion of the phosphorus will pass out in the slag, probably in the form of a phosphate ; but when the slag is in its normal grey condition, almost the whole of the phosphorus appears to pass into the pig-iron. Hence ores containing a notable amount of phosphorus are only available, unless the blast furnace be allowed to work as before described upon a basic slag, for the production of pig-iron of forge quality for puddling purposes ; for foundry purposes where castings of delicate forms but of little strength are required; for the production of a special pig available for the basic Bessemer process ; or for certain other special purposes. 106. The influence of phosphorus in pig-iron, malle- able iron, and steel is more fully detailed at pp. 72, 207, 393, respectively; and it will suffice here to note generally, that its presence in pig-iron renders the iron more fluid when in the molten state, and thus well adapted for casting light and delicate ornamental castings, but such iron is also very weak, and not adapted to the production of strong heavy castings. 107. In malleable iron and steel, small proportions of phosphorus suffice to render the metal sensibly harder, without materially affecting its tenacity, but it renders the metal at the same time decidedly cold-short. Cold- short metal cracks and breaks, especially at the edges, when treated under the hammer, although such material may be readily worked by hammering or rolling when suitably heated ; but, if in malleable iron or steel the pro- portion of phosphorus attains to - 5 per cent, or upwards, then, in addition to being cold-short, the metal also shows a marked falling-off in tensile strength. The late Mr ; 54 STEEL AND IRON. [Chap. IV. A. L. Holly, C.E., of the United States, concluded from his experiments that the effect of phosphorus varied much according to the proportion of the other impurities present, so that, in iron containing not more than 0*15 per cent, of silicon, or 0'03 per cent, of carbon, phosphorus up to 0-2 per cent, might be present without injury to the metal. 108. Silicon is always present more or less in all varieties of commercial iron, either in combination with the metal, or, as in the case of malleable iron, it may possibly occur only as a constituent of the intermixed cinder in such iron. 109. A compound of iron, silicon, and carbon results when oxide of iron and silica in the form of sand are simultaneously reduced by heating a mixture of these bodies along with carbon, to the temperature of a wind- furnace ; or a like compound is obtained by heating silica, iron, and carbon to the same high temperature; or by treating such a mixture in a Siemens gas furnace. Mr. Riley has prepared an alloy or pig-iron, containing as much as 21 per cent, of silicon, which alloy presents a bright grey or silvery-white colour, and is crystalline, hard, and so brittle that it might be pulverised in a mortar. 110. Authorities differ as to the condition in which silicon exists in pig-iron, some maintaining that in dark- grey pig-iron, silicon, like carbon, exists both in the chemi- cally combined and in the graphitic state ; whilst others are of opinion that it never occurs except in the state of chemical union with the iron ; and experimenters have not yet been able to separate by mechanical means the silicon from pig-iron in the same manner as graphite has been separated. 111. Silica always suffers reduction in the blast fur- nace, in amount proportionate to the quantity of carbon present in the furnace, and to the increase in temperature attained ; hence the pig-iron produced in the blast fur- nace is, as already mentioned, always contaminated with silicon, and with every increase in the temperature of the Chap. IV.] FERROUS SILICATES. 5,1 blast there is a corresponding increase in the proportion of silicon reduced and entering the pig-iron ; so that hot- blast pig is always more highly siliceous than cold-blast, and grey iron, as requiring a higher temperature for its production, is also more siliceous than the white iron pro- duced in the same furnace. The excess of fuel employed when first blowing in a furnace often results in the metal first tapped being more highly siliceous than that produced in subsequent workings, and, under these conditions, the siliceous pig known as glazed or blazed pig often results. Poor ores and smelting mate- rials ai'e also conditions favourable to the production of a siliceous iron ; and further, siliceous pig is more frequently produced when the furnace is working upon very refractory ores. The mechanical and chemical influence of silicon upon pig-iro>n, malleable iron, and steel will be more fully spoken of whim treating of those metals (pp. 72, 207, 394). 1 1 2. Ferrous silicates of variable composition are formed as the result of the union of oxygen with silicon and iron ; and thus the various slags and cinders pro- duced in the blast furnace, the puddling, refining, re-heat- ing, or other furnaces employed in the production or sub- sequent manipulation of iron are essentially ferrous silicates. Pure silica and oxide of iron unite at a white- heat to the production of a fusible ferrous silicate, and in this manner, during the ordinary operation of weld- ing together two pieces of iron, the blacksmith removes the oxide or scale, which during the process of heating the iron in the smith's fire forms upon the surfaces of the bar to be welded, by throwing upon the heated surface a quantity of siliceous sand, whereby a readily - fusible ferrous silicate is produced, which flows away under the pressure of the hammer or press employed in welding together the two surfaces of the metal, and so leaves the two surfaces to be united quite clean and in the best condition for being successfully welded. 113. Ferrous silicate (2 FeO Si0 2 ) yields about 70 per 56 STEEL AND IRON. [Chap. TV cent, of ferrous oxide and 30 per cent, of silica ; it melts at a white heat, but if heated with access of air it suffers partial decomposition, with the production of ferric oxide and the separation of silica. Thus tap-, forge-, or mill-cinder i.e., the slag of either the puddling or re-heating fur- nace which is essentially a ferrous silicate of the above formula, yields, when roasted with access of air during several days in suitable kilns or ovens, a highly refractory dark grey and lustrous body, consisting essentially of ferric or magnetic oxide, with small proportions only of silica. The roasted tap-cinder is known as " bull-dog" and is used largely for making the bottom of the puddling fur- naces ; and it may be noticed in passing that, during the roasting of the tap- or forge-cinder from the puddling fur- nace for the production of bull-dog, there liquates from the mass two other products : the one which collects in the bottom of the kiln, and is known as " bull-dog slag," is more siliceous than " bull-dog," and carries with it much of the phosphorus contained in the cinder ; whilst the other product is still more siliceous, and runs away from suitable openings left in the kiln for the purpose, carrying with it also the larger proportion of the phos- phorus contained so largely in the slag or cinder of the puddling furnace. 114. The inferior class of pig-iron occurring in the market under the name of Cinder-pig in contradistinction to all mine pig i.e., pig smelted entirely from ore or mine is obtained by treating in the blast furnace these rich slags or cinders, along with a certain proportion of other inferior ores or mine ; and Dr. Percy states that when ferrous silicate of the composition 2 FeO SiO 2 is so treated, or otherwise strongly heated with carbon, about two-thirds of its iron is reduced, leaving behind a more siliceous slag having a composition represented by the formula 2 FeO 3 Si0 2 ; but since, as will subsequently appear, the phosphorus from the pig-iron passes out during the puddling process into the tap-cinder of the puddling furnace, so the pig-iron (cinder-pig) produced by smelting Chap. IV.] ALLOYS OF IRON. 57 such slags and cinders is also proportionately contami- nated more largely with phosphorus, and is hence oi decidedly inferior quality. 115. Iron and Nitrogen are usually described in chemical works as yielding two or more distinct nitrides of iron. When iron-wire is heated to redness for some hours in a current of dry ammoniacal gas, the wire so treated is stated by Despretz, Fremy, Savart, and Dick to gain slightly in weight, to be more brittle, and less alterable by exposure to the atmosphere than pure iron, and to become also whiter in colour \ whilst Savart adds, that after attaining to this condition, if it be longer exposed to the ammoniacal vapour, the metal assumes a dark-grey colour, becomes soft, has a graphitic fracture, and will not harden in water. The evidence as to the exact increase in weight of the iron by the above treatment is very con- tradictory, the statements ranging between 0*2 to 12 or 13 per cent., and from such evidence it is impossible ta state whether nitrogen does or does not play any import- ant part, as is sometimes understood, in the process of cementation for the conversion of bar-iron into blister-steel. 116. Bois and Boussingault have examined commercial iron and steel for nitrogen, and state that they find from 0-005 to 0'124 per cent, of nitrogen in all specimens. The gases occluded by steel, and contained in the blow- holes or honeycombs of steel ingots, have been analysed by Mr. Parry, Mr. Stead, and others, and they find such gases to yield from 10 to 15 per cent, of their volume of nitrogen. 117. Iron and many of the other metals unite with great facility to form alloys ; thus, for instance, when the ores of iron and of a second metal are simultaneously reduced, an alloy of the two metals often results, though with but few exceptions these alloys are without com- mercial importance ; and further, the alloys of pure iron and the various metals hereinafter enumerated are but little known, only the triple alloys of carbon, iron, and other metals having been much studied. 58 STEEL AND IRON. [Chap. IV. 118. Manganese is a constant constituent of pig-iron ?nd of steel, but of the alloy of pure iron with manganese very little is known, whilst with pig-iron its alloys are of very considerable importance. As spiegeleisen, or white iron containing from 8 to 15 per cent, of manganese, it is a regular article of commerce ; whilst more latterly special alloys known as ferromanganese, containing from 50 to 75 per cent, of manganese, have been the objects of a regular manufacture for use in the production of mild steel, principally by the Bessemer and Siemens processes. The especial application of ferromanganese to these processes will be subsequently referred to, as will also the effects of manganese upon cast-iron (p. 74), upon malleable iron (p. 204), and upon steel (p. 394). The presence of manganese in iron ores is favourable to the elimination of sulphur from the pig-iron produced from such ores, but its influence, if any, is small in diminishing the amount of phosphorus passing into the pig-iron. 119. Tungsten and iron unite readily, when tungsten is reduced from its compounds by carbon in the presence of metallic iron, but a very elevated temperature is required for the reduction. Thus, if grey pig-iron be heated to a very high temperature in a closed crucible along with tungstic oxide, the tungsten is reduced by the graphite of the pig-iron, and then unites with the iron present, with the production of a hard, fine-grained, almost silver-white steel of great tenacity and considerable malleability ; if the same experiment be repeated with white-iron or spiegel- eisen containing only very small proportions of graphitic carbon, it is found, the conditions being otherwise the same, that little or no tungsten is reduced, indicating that combined carbon in pig-iron does not effect the reduc- tion of tungsten from tungstic oxide. For further infor- mation respecting the effect of tungsten upon steel, refer to p. 395. 120. Chromium, when alloyed with iron, decreases the fusibility of the metal, and like tungsten is said also to Chap. IV.] ZINC AND IRON. 59 increase the tenacity, malleability, and ductility of the steel in which it occurs. Chromium appears to partially replace carbon in steei. 121. Copper does not readily unite for the production of a homogeneous alloy by the simple fusion of any mix- ture of the two metals, but if iron be added in small quantities to brass or bronze in a state of fusion it is readily taken up, and the resulting alloy has a higher tensile strength than the original brass. An apparently homogeneous alloy of copper and iron seems to result upon the simultaneous reduction of a mixture of the oxides of copper and iron, the former being always main- tained in excess. Copper in small quantities renders malleable iron or steel red-short, and sensibly diminishes its tenacity, while pig-irons containing copper are unfit for conversion into malleable iron or steel. 122. Aich-metal is a malleable, ductile, and tenacious alloy of copper, zinc, and iron in the proportions of about 60 per cent, of the first mentioned, with 38 to 44 per cent, of zinc, and from 0'5 to 3 per cent, of iron. Sterro-metal is a similar alloy containing from 2 to 4 per cent, of iron introduced in the form of malleable iron, with from 1 to 2 per cent, of tin ; such an alloy is brass-yellow in colour, and has been proposed on account of its high elasticity, tensile strength, and the facility with which it may be worked either hot or cold, as a material for the construc- tion of ordnance, but its introduction has not, however, been favourably received. 123. Zinc and iron yield, when heated together, more or less crystalline, brittle, and friable alloys, which, however, are without practical application to the arts, and are more properly zinc alloys, since about 7 per cent, is the maximum amount of iron that molten zinc will take up ; but the manufacture of galvanised or zinced plates that is, plates coated with a thin layer of zinc, or with an alloy of zinc and iron form an important branch of metallurgical industry. Galvanised plates, whilst possessing the strength due to 60 STEEL AND IRON. [Chap. IV. the iron, are not affected on exposure to atmospheric in- fluences by rusting or corrosion, so long as the zinc coating remains intact. The galvanising process is effected by dipping the malleable iron plates, previously cleansed from scale or rust by immersion in dilute sulphuric acid, into a bath of molten zinc the surface of which is covered by sal-ammoniac (NH 4 C1) ; under these conditions the surface of the iron plate becomes coated or alloyed with a thin protecting layer or coating of zinc, or of a zinc alloy. 124. Tin and iron unite when heated together, with the production of grey or white alloys, which are harder than tin, and break with a crystalline or granular frac- ture. In this manner alloys of the two metals in almost any proportions may be obtained, but like the alloys of zinc, they are also without practical application to the arts, although in the production of Terne-plates the sur- face of an iron plate is coated by dipping it when cleaned into a bath of molten tin, whereby a firmly adherent non-oxidisable coating of a stanniferous alloy covers the surface of the iron. Small quantities of tin in mal- leable iron or steel suffice to render the same cold-short ; and also only workable with great care even at a red heat, such metal being also brittle, and exceedingly diffi- cult to weld. 125. Antimony can be readily alloyed with iron, but its presence in wrought-iron, to the extent of only 0-2 or 0'3 per cent., is sufficient to render the iron both red- short and cold-short. 126. Nickel also may be readily alloyed with iron, by the direct fusion of the two metals, or by the simultaneous reduction of their mixed oxides. The presence of nickel in iron does not affect its malleability, but the alloy is whiter in colour than pure iron, is not so easily affected by exposure to air or moisture, and takes a better polish than iron. A native alloy of nickel and iron with other metals occurs in the meteoric masses which are occasionally found. Chap. V.] PIG-IRON. 61 127. Cobalt, like nickel, readily alloys itself with iron, producing similar alloys to those last described ; and small quantities do not produce any material alteration in the physical or working qualities of the iron or steel. 128. Lead does not appear to unite with iron when the two are melted together, and no satisfactory alloy has been described of these metals. 129. Aluminum yields, with steel, alloys of various composition, but they are without value or practical application to the arts. The effect of aluminum upon steel is to diminish the tensile strength of the latter. 130. Silver does not appear to unite with iron when melted along with it, for the silver is found, upon soli- dification of the fused mixture, to have separated through- out the mass, and not to have produced any homo- geneous alloy of the metals. 131. Gold alloys itself readily with iron, upon simple fusion together of the two metals, the alloy being harder than malleable iron. 1 32. Platinum alloys with iron without difficulty, the melting-point of the alloy being below that of steel. Steel containing 1 per cent, of platinum is tough, fine- grained, tenacious, and ductile. Similar alloys are also obtainable by the substitution of small quantities of the rarer metals palladium and rhodium. CHAPTER V. CAST- OR PIG-IRON. 133. Pig-iron is the form in which the product of the treatment of iron ores, with fuel and fluxes in the blast furnace, occurs in commerce. It is a granular crystalline compound of iron with carbon, silicon, sulphur, phos- phorus, and manganese, with oftentimes also smaller G2 STEEL AND IRON. [Chap. V quantities of other metals, such as arsenic, titanium, copper, chromium, B. Diagram showing the Variations in the Internal Forma Oc Blast furnaces. Chap. VII.] INTERNAL FORM OF THE BLAST FURNACE. 113 charcoal furnaces are usually of considerably greater height in proportion to the diameter than coke furnaces, and the angle or slope of the hearth and boshes is, as a consequence, very acute. 221. In the blast furnace for the production of pig- iron, the blast is supplied through nozzles or twyers laid approximately horizontal, and not at an angle downwards, as occurs when malleable iron is produced direct from the ore in the small Bloomery furnaces of the United States and Canada. 222. As indicating the increase in height and capacity of the blastfurnace of recent practice over that of twenty years ago, it will suffice to note that whereas in 1861 the Cleveland furnaces averaged from 60 to 70 feet in height, from 16 to 20 feet in diameter at the boshes, and had a capacity of about 12,000 cubic feet, in the same district the prevailing height is now from 90 to 100 feet, with from 25 to 30 feet diameter at the boshes, and a capacity of from 30,000 to 40,000 cubic feet. A furnace at Ferry-hill has been erected of 105 feet in height with 50,000 cubic feet capacity. In Germany, however, the furnaces are still much smaller than in England, the largest only having a capacity of perhaps 15,000 cubic feet. 223. The best internal shape, size, and proportions of the blastfurnace are not capable of absolute determination by theoretical considerations alone; the dimensions varying with the nature of the ore and fuel (charcoal or coke) worked in the furnace, the pressure and temperature of the blast, and the rate of driving (amount of air to be blown into the furnace in a given time). The best practical guide of the proper internal shape of a furnace for working any particular class of ore and fuel is afforded by an examination of the form which a furnace working upon like materials presents when blown out after a working campaign. For, any errors in the original design of shape are marked in such a furnace by the addition or accretion of materials upon such parts as were originally I 114 STEEL AND IRON. [Chap. VTT. too large in diameter, and a corresponding undue wearing away of such other parts as were too small, until the furnace ultimately assumes its best form. Much, however, may be determined as to the variations in size and shape necessitated by differences in the ores, fuels, fluxes, blast, m the hearth after the withdrawal of the previous charge is now added, and in a little over one hour from the commencement, the Fig. 39. Elevation of Charcoal Finery. 232 STEEL AND IRON. |"Chap. XH. workman having in the meantime constantly broken up and raised the metal from the hearth bottom towards the wyers, the metal will have " come to nature," as it is termed, and a lump of pasty, malleable metal, mixed however, with much slag or cinder, collects in the bottom of the hearth, from whence it is withdrawn in one bloom or ball weighing something under 2 cwts. This bloom is forthwith shingled under the steam-hammer or under a helve of about 6 tons weight, for the production of a flat bar or slab of from 1 J inch to 2 inches in thickness, which is nicked or partially cut through so as to yield when subsequently broken up by the sledge hammer, pieces or stamps weighing about 28 Ibs. each. The fracture of each bar is examined as it is thus broken up, and only such slabs as present a fairly crystalline and uniform grain of metal are used in the formation of the pile for the finished sheets. During the conduct of the process of fining, it is the practice to tap out the slag or cinder from the hearth two or three times, as may be required. Such slags or cinders are of a highly basic character, containing towards the end of the fining operation as much as 75 per cent, of ferrous oxide. 417. The stamps obtained as above are subsequently piled upon the flattened end, from 12 to 18 inches in length, of a staff made of a metal similar in quality to that of the stamps themselves. The pile formed by placing about three of the stamps upon the staff is raised to a welding heat in the hollow-fire, and then welded into a solid mass under the hammer, whereupon the slab so formed is nicked on the under side and then doubled upon itself, whereby the top and bottom surfaces of the pile are produced from the same surface of the slab. The pile is again raised to a welding heat in the hollow-fire and again welded under the hammer into a billet, which is taken whilst still hot, sheared from the handle of the staff, and at once rolled into a bar. 418. The particular method of procedure just described for the production of the hammered bloom is known as Chnp.XII.l THE LANCASHIRE HEARTH. 233 the method of " tops and bottoms," from their upper and lower surfaces being produced from the same face of the slab, and these blooms are afterwards sent to the rolls for rolling ont into sheets, of which the upper and lower sides present the same kind of surface. 419. The hollow-fire just referred to as being employed for reheating the stamps for rehammering and re welding, is a deep rectangular hearth or chamber of brickwork, arched over at the top, whilst in the sides are openings closed by sliding doors. The bottom of the hearth is formed of cast-iron plates, beneath which the air is free to circulate for keeping the plates cool. On the bottom plate is built a layer of fire-brick, and the hearth is not provided with any chimney or stack, but the gaseous products of com- bustion before escaping to the atmosphere, pass from the hollow-fire through a partition or wall between it and a second chamber in which the pile of stamps is placed for a preliminary heating, before it is inserted into the flame of the hollow-fire. The firing door or stoke-hole is on one side of the chamber, and through this door the coke, which is the fuel here employed, is introduced on to the hearth bottom. The chamber is at all times only partially filled with fuel, and the combustion of the same is maintained by a blast of atmospheric air introduced from an inclined twyer near to the surface of the fuel. In this manner the chamber or furnace above the fuel is filled with flame, which plays around the stamps placed within it for reheating ; the pile does not rest upon the bottom, but is supported in the midst of the flame, in which manner it is raised to a welding heat without coming into contact with the fuel, the handle of the staff all the time projecting beyond the furnace door. 420. The Lancashire Hearth or Swedish Finery is also a rectangular closed chamber or hearth, the sides and bottom of which are of cast-iron plates. The hearth communicates by horizontal flues with the stack, and fche pig-iron is first placed in them for heating before it is drawn forward into the hearth itself. Charcoal 234 STEEL AND IRON. [Chap. XII. is the fuel employed in this health, and a blast heated to a temperature of 100 C. (212 JFahr.) is intro- duced through one twyer, this temperature being given to it by passing it on its way to the twyer through a series of iron tubes heated by the waste gases of the finery ; the blast is delivered at a pressure of from 1 lb. to 1^ Ib. to the square inch. The method of pro- cedure with the Lancashire hearth is first to charge upon the heated hearth a quantity of charcoal, upon which is then drawn from the flues or heating chambers already mentioned a charge of about " cwts. of the pig-iron pre- viously placed there for heating by exposure to the gases in the flues j the blast is then turned on and more charcoal is added, in which manner the metal is slowly melted and trickles down before the blast, by which it is partially decarburised and fined before it reaches the hearth bottom, where it partially solidifies or hardens, and the workman is constantly engaged breaking it up with his bars and raising it before the blast for further fining and decarburisation. As the decarburisation thus proceeds, the metal becomes less fusible, and the workman is able to raise the whole charge to the top of the fuel in the hearth, and this being accomplished, it is immediately followed by the addition of fresh charcoal and an increase in the temperature by the turning on of more blast, whereby the partially fused metal is again perfectly melted, and thus better separated from the slag with which it is mixed ; and, this being effected, the fined metal is collected into a ball upon the hearth bottom, which ball is then withdrawn from the furnace, shingled as usual, and cut up into suitable lengths for piling and reheating, either in a separate fire or in a gas-furnace. The pile is then rewelded and further treated under the hammer, or rolls for the production of malleable bars. 421. The fuel consumed in this hearth amounts to about 150 Ibs. of charcoal per 100 Ibs. of bars produced, whilst the process is attended with a loss of about 1 5 per Chap. XII.J THE WALLOON PROCESS. 235 cent, of the weight of the pig-iron introduced into the furnace or finery. 422. The Walloon process, like the Swedish- Lancashire hearth last described, is an example of the three operations of melting down, breaking up, and balling of the product in one and the same furnace, as a continuous operation, and is principally interesting as being the method according to which, in Sweden, the famed Dannemora malleable iron is produced. 423. The furnace employed in the Walloon process is a simple quadrangular hearth measuring from 2 feet to 2 feet, 6 inches in width, and about 10 inches in depth ; it is formed of thick cast-iron plates, and is fitted with an inclined twyer through which the blast is introduced from two pairs of primitive bellows, worked by cams upon a revolving shaft driven usually by water power. The hearth is surmounted by a hood and chimney of brick- work, for taking away the gases, &c., from it. In one side of the hearth, and opening near the bottom of it, is an aperture through which the liquid slags produced by the process are tapped out. 424. The hearth, having worked off its last charge, is partially cleaned by tapping out most of the remaining slag, but it is still necessary to leave in the hearth suffi- cient of the highly basic slag to assist in the decarburisa- tion of the succeeding charge; for the fining in this pro- cess is always conducted in a bath of slag. Besides the slag, there will also remain a residue of incandescent charcoal, and upon this the succeeding charge of from 2 to 3 cwts. of metal, previously cast into small pigs suitable for manipulation in this hearth, is placed. The hearth is then filled up with fresh charcoal, whereupon the blast is turned on, at first more slowly, but more freely as the process goes on. The metal for refining soon begins to melt, and falls down in front of the blast in its descent towards the hearth bottom ; it thus becomes partially decarburised and purified under the oxidising influence of the blast, the decarburising action being also assisted 236 STEEL AND IRON. [Cbap. tEt. by the highly basic slags of ferrous silicate, which collect upon the surface of the metal in the hearth. The slags, as before mentioned, are tapped out through the slag- hole as their quantity becomes excessive, only sufficient being retained in the hearth to cover the fluid metal, and promote by its basic character the desired decar- burisation of the pig-iron ; but the richer portions of the slags tapped out are collected, and, along with the hammer-scale obtained in the hammering of the bars, are added to a subsequent charge during the first or melting- down stage of the process. A pasty mass of partially-refined iron thus collects in the bottom of the hearth, and the workman, with the assistance of a strong iron bar, then collects the metal into one mass or bloom, and raises it on to the top of the fuel, more fuel being at the same time added and the pressure of blast further increased. In this manner the metal again melts and passes down as before into the hearth, having undergone a further degree of fining or decarburisation, by exposure to the oxidising influence of the blast, so that the metal has by this time assumed a spongy con- dition, when it is again collected into one bloom or ball, and withdrawn from the furnace to be shingled for the expulsion of mechanically-mixed slag and the consolidation and welding together of the particles of the spongy mass. The blooms thus obtained weigh from 1 to 2 cwts. each, and are cut up at the same heat under the hammer into three or four pieces of suitable lengths, which are then re- heated, and again hammered for drawing out into bars. 425. The melting-down stage of this process occupies from three to three and a-half hours, and the whole operation, including balling and shingling of the blooms, requires about five hours for its completion. The hearth is worked much hotter than the ordinary charcoal finery, and the loss of metal is from 15 to 20 per cent, of the charge of pig-iron introduced, while the consumption of charcoal amounts to about 150 Ibs. for every 100 Ibs. of pig-iron treated. Ohap. Xn.1 THE WALLOON PROCESS. 237 426. During the drawing down of the shingled bloom into bars some five or six reheatings of the metal are necessary, of whi'ch the first is effected in the finery hearth itself, during the first or melting-down stage of the process, the shingled bloom being held for this purpose by a pair of suitable tongs in the fore part of the hearth, where the temperature is sufficient to heat the bloom almost to a welding heat ; but the later reheatings are effected in a separate fire. 427. The exact method of procedure observed in the working of the Walloon process varies somewhat from that described above in different works and localities. Thus, instead of introducing the charge on to the hearth in the form of small pigs or slabs, as previously described, it is not unusual to prepare the pig-iron, which is generally of a white or mottled quality, in slabs of 15 or 16 feet in length and 3 inches in thickness, and when the hearth is filled up with charcoal and the blast turned on, a slab is introduced by resting it on a roller in front of the hearth, whilst its extremity is pushed over the plate in front of the twyer, and so held in the middle of the hearth at a distance of 9 or 10 inches above the bottom. The end of the slab is thus presented to the high tempera- ture of the hearth near the twyer, and as it melts down it is gradually pushed farther into the hearth until in this manner the amount of metal required to produce a bloom of about 100 Ibs. in weight has been introduced. By this method the fining or coming to nature, is very rapid; and the workman during the melting down also constantly rabbles the metal with iron bars as it collects on the hearth. 428. The metal produced in these charcoal or Walloon fineries is of a superior quality ; but attempts to use hot- blast and coke instead of cold-blast and charcoal are attended with a deterioration in the quality of the product. 238 CHAPTER XIII. REFINING OF PIG IRON, OR THE CONVERSION OF GRE\ INTO WHITE IRON IN THE COKE REFINERY. 429. WHEREVER the process of dry puddling (p. 248) is pursued for the production of the better qualities of malleable iron such as those yielded by the Yorkshire furnaces, this preliminary treatment of pig-iron for the production of a partially decarburised and desilicised white or refined iron is still pursued. Now, in dry puddling the oxidation necessary for the conversion of pig-iron into malleable iron is more dependent upon the action of the atmospheric oxygen than it is in pig-boiling or wet-puddling, for in the latter slags rich in oxides of iron are present in larger quantity, and the oxidation of the impurities in the pig-iron is more largely affected by these rich slags than by atmospheric oxygen. Hence dry-puddling is only applicable to the working of white or refined iron, since such metal in passing from the solid to the molten state, passes through a soft pasty condition not afforded by grey iron under like cond itions, and this state of the pig-iron is highly favourable to oxidation by the oxygen of the air. 430. The refining of pig-iron now under considera- tion is, therefore, only preliminary to the puddling of the metal in the reverberatory furnace ; and it con- sists in melting pig-iron in a rectangular hearth with coke or charcoal ; and at the same time directing upon the surface- of the melted metal a blast of atmospheric air from several inclined twyers, where- upon under such strongly oxidising conditions, the pig- iron under treatment (usually grey), besides under- going a partial decarburisation, has its silicon also largely oxidised with the formation of silica ; and this, Chap. XIII.] THE REFINERY. 239 uniting with ferrous oxide yields a highly basic slag of ferrous silicate, in which slag also occurs a proportion of the phosphorus and sulphur present in the original pig- iron. The result is the production of a white or par- tially purified refined metal, which is subsequently more readily and quickly converted into malleable iron in the puddling furnace, owing to the decreased fluidity of the Fig. 40. Elevation of the Refinery for converting Grey into White Iron. molten refined metal, and its greater freedom from impurities. The refined metal may be either run directly from the refinery to the puddling furnace, or, as is more usual, it may be cast into forms easily broken up into pieces suitable for introduction into the furnace It is thus noticeable that whilst the object of the Swedish and German fineries already described was the production of malleable iron direct, the product of the English refinery now being considered, is only a partially purified or refined metal requiring further treatment in the puddling furnace for its conversion into malleable or wrought iron. 431. The refinery or running-out fire, in which the refining operation is conducted, consists of a strong 240 STEEL AND IRON. [Chap, cast-iron framework, surmounted by a low brick chimney or stack of from 16 to 18 feet in height (Figs. 40, 41). The hearth is a quadrangular cavity about 4 feet square and from 15 to 18 inches in depth, and which is bounded on two of its sides and at its back by cast-iron water blocks, a a, fitted within the vertical iron framework of the furnace, and through these blocks a current of water Fig. 41. Plan of the Refinery and of the Mould for the Refined Metal. constantly circulates. The front side of the hearth is closed by a cast-iron dam-plate, in which the tap-hole is placed, and by which both metal and slag are tapped out into the casting-pit or pig-mould, b, made of thick cast- iron plates or blocks, with rebated joints luted with fire-clay and held together by suitable clamps. The pig- mould is about 12 inches in width by from 14 to 16 feet in length ; it is placed in front of the refinery, and rests longitudinally upon the edges of two long cast- iron or brickwork cisterns, through which a current of water flows to aid in the quicker cooling of the refined metal, both by cooling the mould and by supplying the water which is thrown over the surface of the heated metal in the mould. The water in these cisterns is Chap. XIII.] THE REFIXERY. 241 maintained at a level of about 1 inch below tlie under- side of the pig- bed or mould. In order to still further facilitate the breaking-up of the plate of refined metal so obtained, a projecting rib is often left in the bottom of the mould, producing a corresponding groove and line of weakness in the plate of metal cast therein. 432. The bottom of the hearth is formed of blocks of dressed sandstone of about 12 inches in thickness, which themselves rest upon a substructure of brickwork or masonry. Above the side water blocks, a a, and carried upon suitable projections or lugs, are the cast-iron twyer plates of some 2J inches in thickness, which are provided with openings ' for the introduction of the two or three (according to the size of the hearth) blast nozzles or twyers upon each side of the hearth. The water twyers are usually of from 1^ to If inch in diameter, and are inclined downwards at an argle of from 30^ to 35. The blast is supplied at a pressure of from 2 to 3 Ibs. per square inch, according to the nature of the coke employed; and the twyers upon the two sides of the refinery are arranged s.o that the blast delivered by each one is directed towards the space between the two twyers on the opposite side, thereby distributing the blast more uniformly over the whole surface of the molten metal in the hearth ; each nozzle is further provided with a stop or regulating valve for adjusting the supply of blast from each twyer during the working of the charge, w w are water troughs or boshes into which the waste water from the twyers is delivered, and in which the workman cools his tools during the working of the charge. The back of the furnace between the base of the stack and the water blocks is closed by wrought or cast-iron doors hung to the side frames, and the front above the darn-plate is also closed by a sliding door, connected with a lever by which it can be readily raised or lowered. A dust-plate is also usually fixed on the dam-plate to facilitate the filling and working of the fire. Q 542 STEEL AND IRON. [Chap. HI1 433. In the Yorkshire refineries five twyers only are employed, two being placed in one side and three in the opposite side of the hearth, but arranged as before so as not to oppose each other. In some of the smaller refineries, however, sometimes but one blast nozzle is used, and that is introduced at the back of the furnace, in which case also the several parts, as the water blocks, moulds, and the castings of the framework, are all made propor- tionately smaller and lighter in section. 434. According as the charge of the refinery is made up of selected pig-iron, old castings, and other scrap, &c., or, as in rarer cases, of the molten pig-iron run direct from the blast furnace into the refinery, so the refineries are distinguished as " melting-down " and " running-in " respectively : and while the melting-down refineries are always built at some distance from the blast furnace, it is usual to build the running-in ones in the immediate vicinity of the blast furnace from which they are to receive their charges of molten metal. 435. The refinery works continuously that is, as one charge is tapped out, the hearth before it has cooled down is immediately prepared for the reception of the next. But on commencing to work a new furnace, or after a stoppage, a quantity of broken sandstone is first spread over the floor of the hearth and a fire made in the centre, whereupon coke is added through the folding doors ordinarily closing the back of the furnace, and a light blast is at the same time turned on ; after this the charge of pig-iron, scrap, and coke is introduced by piling on the materials in alternate layers, until the whole charge, varying with the dimensions of the refinery but averaging about two tons of metal in the larger furnaces, has been made up, when more fuel is added to the top of the pile, and the full power of the blast turned on. Such a charge requires about six cwts. of coke for its refining, and the process occupies from three to four hours for its completion according as white or grey iron is under treatment ; the last-mentioned taking a little more time Chap XIII.J REFINERY CINDER. 243 to arrive at the same stage than is necessary when white iron forms the raw material. The refining is accele- rated by the addition to the charge of basic slags, cinders, or scale, such as is obtained from the reheating furnaces, hammer -scale, &c. ; such additions acting as oxidising agent?, and so assisting the oxidising action of the blast, whilst also increasing to a small extent the total yield of iron from the refinery, since the carbon of the pig- iron is partially oxidised by the oxygen of the oxides of iron present in the scale or cinder, and an equivalent amount of iron is at the same time reduced and added to the yield. 436. The first effect of the heat in the newly-erected or repaired refinery is to soften the sandstone and glaze the surface of the hearth. The pig-iron, &c., of the charge begins to melt after the lapse of about one hour from the commencement, and it trickles down during its fusion through the mass of coke on to the bottom of the furnace, where, in from one and a-half to two hours the whole of the charge is collected, and so lies in a fused condition beneath the superincumbent coke, of which latter more is now added. The blast is continued for another half -hour or a little more, during which time a further proportion of silicon from the pig-iron is oxidised, producing silica, which, together with an additional amount of silica derived from the ash, &c., of the fuel, combines with ferrous oxide re- sulting from the oxidation by the blast of a portion of the iron, thereby producing a highly basic and readily fusible slag or cinder of an orthosilicate or ferrous silicate of the formula 2FeO SiO 2 = Fe 2 SiO 4 , containing from 40 to 60 per-cent. of iron, and presenting when cold the usual very dark-blue or black colour, with the vitreous, lustrous fracture characteristic of cinders rich in iron. Such a slag exercises, as previously shown, a powerfully decarburising influence upon the molten metal beneath it, and thus under the joint influence of this slag and the oxy- gen of the blast, the carbon and silicon with smaller quantities of sulphur and phosphorus and the greater 244 STEEL AND IRON. [Chap. XIII portion of the manganese present in the original pig-iron are oxidised, as indicated by the accompanying analyses of the original pig-iron, and of the refined metal obtained ANALYSES OF REFINERY CINDER OR SLAG.* Dowlais (Eiley). Bromford Crystallised Ordinary cinder. Crystallised cinder. cinder. (Forbes). Ferrous oxide . 65-52 54-94 61-28 Silica . . . i 25-77 33-33 22-76 Manganous oxide . 1-57 2-71 3*58 Alumina " ., 3-60 5-75 7-30 Lime . . . 0-45 1-19 3-41 Magnesia .' > ; 1-28 0-50 0-76 Sulphur . . -v.- 0-23 0-46 Ferrous sulphide . 0-27 Phosphorus . 1-37 0-99 Copper . traces Per-centage of iron 50-96 42-84 47-66 ANALYSES OF REFINED IRON. Ebbw Vale (Noad). Bromford (Dick). France (Regnault). iron. Refined iron. Refined iron. Pig iron. Refined iron. Carbon . Grap Silicon. Sulphur Phosphorus . Manganese . Insoluble matter . Iron . hite 2-40 2-54 0-22 0-13 0-86 0-30 0-32 0-18 0-09 0-24 3-07 0-63 0-16 0-73 trace 0-14 3-00 4-50 0-2 1-7 0-5 95-14 92-3 97-8 Percy : "Metallurgy," Vol. II. Chap. XIII. J REFINED IRON. 245 therefrom. More fuel is added to the refinery from time to time, that the temperature of the hearth may be main- tained by the combustion of the fuel under the action of the blast, until the desired degree of fining has been effected. The whole time occupied in the refining process for an average charge is about three hours, or a little less when \\hite iron predominates in the charge, and somewhat beyond this time if grey iron be under treat- ment. During the refining the surface of the fuel on the hearth is in a continual state of agitation, produced by the escape of carbonic oxide, formed during the decar- burisation of the metal by the oxygen of the blast, and by the fluid basic slags upon the surface of the melted metal. 437. When the refining is considered complete or has been carried as far as is required, the contents of the hearth, slag and metal together, are tapped out into the cast-iron mould, b (Fig. 41), when the slag or cinder floats upon the surface of the metal, and being the more fusible of the two remains fluid after the surface of the metal in the mould has become partially solidified, and the slag can thus be tapped off from the surface of the refined metal into other moulds placed for its reception at the lower end of the mould, b, while the plate of refined metal is the more rapidly cooled, and rendered also more or less hard and brittle by throwing a quantity of water over its surface. 438. The plate of fine metal, refined iron, plate metal, or simply metal, as the product of the refinery is variously called, consists of a plate of metal of from 1 to 3 inches in thickness, 12 inches in width, and from 12 to 14 feefc in length. It is grooved along its under side, and has been rendered brittle by quick cooling, so that it is easily broken up into pieces suitable for ready transport to the puddling furnace, where its final conversion into malle- able or wrought iron is effected. The plate of fine metal presents a bright silvery-white fract-are, the lower part of the slab affording a compact radiated or columnar 246 STEEL AND IRON. [Chap. JCIII. structure, while the upper portion presents a dull and cellular appearance on fracture. 439. In the melting down and refining of pig-iron, che loss of iron is somewhat greater and the consumption of fuel is about 20 per cent, in excess of what is required when the metal is taken in the fluid state direct from the blast furnace ; but the average loss may be taken as equal to 10 or 11 per cent, of the weight of the pig- iron operated upon. The loss is greater in refining hot-blast than it is with cold-blast pig-iron, owing to the larger proportion of silicon, phosphorus, sulphur, manga- nese, &c., in the former than in the latter; while pig- iron smelted from Blackband ores, owing to its extreme fluidity when melted, is difficult of treatment in the re- finery, and occupies accordingly a longer time for refining. 440. In the ordinary melting-down and refinery pro- cess about 24 cwts. of good grey iron are required to yield 1 ton of refined metal, with a consumption during the pro- cess of about 2J cwts. of coke ; and about 136,000 cubic feet of blast per ton will be required if white iron, or 153,000 cubic feet if grey iron, be the metal to be refined. The weekly produce of a refinery with six twyers working upon grey iron ranges from 80 to 100 tons, while 150 to 160 tons may be refined if white iron be the subject of operation. If the metal be run in its fluid state direct from the blast furnace into the refinery, then about 22-3 cwts. of common forge, or 21*1 cwts. of good grey iron, will suffice to yield one ton of refined metal, the consumption of fuel at the same time being reduced to about 2 cwts. of coke, and requiring on)y 94,000 cubic feet of blast per ton of metal treated. 441. The washing process of Baron Krupp, as pur sued at Essen, Prussia, is a species of refining in which the silicon and phosphorus of the pig-iron are largely oxidised and removed by their reaction at a high tempe- rature upon refractory but rich oxides of iron, such as rich iron-ores or hammer-scale. Mr. I. L. Bell discovered that by thoroughly mixing molten pig-iron and such oxidising Chap. XIII.] WASHING PROCESS. 247 ores upon the bed of a reverberatory furnace, in an oscillating cylinder or in otlier suitable apparatus, a violent reaction ensued, and that, in ten minutes from its com- mencement, the silicon and phosphorus of the pig-iron were oxidised, and passed into the slag, the former being reduced from 1*8 to 0-05 per cent., and the latter from 1-4 to (HO per cent. ; but the carbon during the same interval was but slightly affected, being reduced only from 3-5 to 3-3 per cent. 442. As now carried on at the Essen Works, the washing process is conducted upon the hearth of a Pernot revolving regenerative gas furnace, such as is described at p. 297, the revolving hearth of which is about 12 feet in external diameter and 3 feet deep, and is lined or fettled to a depth of 9 inches over the bottom and 15 inches on the sides with lumps of a refractory ore containing from 6 to 15 per cent, of silica, or if more than the latter limit be present, then an addition of lime requires to be made to combine with the excess. The charge of pig-iron, weighing from 5 to 7 tons, and containing, if possible, about 1 per cent, of manganese, is melted in a cupola, and run therefrom into the furnace, rotating at the rate of eleven revolutions per minute, where the metal is heated to a temperature in excess of that required for the puddling process, but below that required for the fusion of steel. At this temperature a violent reaction at once ensues, ar above, which lasts from five to eight or nine minutes, during which the slag produced during the process enters into a a state of violent ebullition,, and runs over the sides of the hearth. The termination of the process is marked by the sudden evolution of a considerable volume of carbonic oxide which had previously been almost nil. The fined metal is freed from much of its silicon and phosphorus, though only very slightly decarburised, and it is then either run into pigs or is at once transferred to the open-hearth steel-melting furnace for the produc- tion of steel by the latter process. After each charge the hearth requires to be refettled with small ore. 248 CHAPTER XIV. PUDDLING, OR THE PRODUCTION OF MALLEABLE IRON B\ THE DECARBURISATION OF PIG-IRON IN THE REVER- BERATORY FURNACE. 443. BY far the largest proportion of the wrought or malleable iron occurring in commerce is the result of the partial decarburisation and more or less complete re- moval of silicon, sulphur, phosphorus, manganese, and other foreign elements or impurities from pig-iron, by its treatment in the reverberatory or puddling furnace ; under which type of furnace is included, besides the fixed ordinary furnace, also the various revolving furnaces heated either by raw coal or by gaseous fuel. 444. The word puddling was originally restricted* to the working of refined iron which never became thoroughly liquid, but was in a puddled or pasty state throughout ; and when unrefined iron began to be worked and was found to melt perfectly, and boil up freely, the process was then termed " pig -boiling" 445. As previously noted, the great distinction be- tween the puddling process and the treatment of pig-iron in the open hearth is, that in the open hearth finery the pig is melted in contact with the fuel, and that only the purer materials, therefore, such as charcoal or coke, are available for use in such furnaces ; whilst in the rever- beratory or puddling furnace the metal is melted on the bed of the furnace without coming into contact with the fuel employed, and hence raw coal, inferior qualities of fuel and other materials, can be used without mate- rially deteriorating the quality of the product. Further, the puddling process admits of a much more extensive use of the various mechanical labour-saving devices which have during late years been applied to these operations. * Proceedings of Institute of Mechanical Engineers, 1877. Chap. XIV.] REACTIONS IN THE PUDDLING PROCESS. 249 446. The reactions involved and changes effected during the puddling process are similar to those occurring in the open -hearth finery. The first result of the treat- ment of the pig-iron upon the hearth of the reverberatory furnace is to effect the conversion of any graphitic carbon into combined or dissolved carbon, since it is only upon carbon in the combined state that the subsequent oxidising influence of atmospheric oxygen is appreciably effective. Secondly, the combined car- bon is oxidised to the condition of carbonic oxide, either, as in " dry-puddling," by the oxygen of a blast of atmospheric air, or by the current of air which passes on its way from the fireplace to the stack over the exposed surface of the liquid metal ; or, as in " pig-boiling " or " wet-puddling," the prodiiction of car- bonic oxide is the result of the reaction of the combined carbon of the pig-iron upon the oxides of iron introduced into the furnace in the form of forge-scale, finery-cinder, tap-cinder or " bull-dog," the purple ore known as " blue- billy," or the purer ores, such as haematite, magnetite, or roasted spathose ore, each or several of which are added to the furnace at different times during the process, and should thus be as free as possible from earthy matters. Thirdly, the silicon, sulphur, and phosphorus of the pig-iron are largely oxidised during the puddling process, and escape in combination with iron into the tap-cinder or slag of the puddling furnace. Lastly, the charge is collected into balls of a size suitable for with- drawal from the furnace and treatment under the ham- mers or squeezers. It may be noted in passing that the division of the subject into dry-puddling and pig-boiling respectively, as will be fully noticed hereafter, depends upon whether the decarburisation and oxidation of the impurities of the pig-iron are more largely effected by the oxygen of the atmosphere, and to a minor degree only by the oxidising basic fluxes, as haematite, forge- scale, tap-cinder, &c., enumerated above, or vice versa, where the major effect is produced by the reduction of 250 STEEL AND IRON. [Chap. XIV. the oxides of iron in the oxidising materials above mentioned, whilst the oxygen of the air plays only a minor part in the reactions. 447. White iron is more suitable than grey iron for conversion into malleable iron by the puddling process, since the former, when raised to near its melting-point, assumes a pasty state highly favourable to the removal of its carbon and silicon under the oxidising influence of atmospheric oxygen, or of the other oxidising agents em- ployed for the decarburisation and purification of the pig-iron. On the other hand, grey pig-iron, although it requires a higher temperature for its fusion, passes at once from the solid to the fluid state without passing through an intermediate pasty condition. It is also more fluid when melted than white iron, so that immediately it melts it sinks at once below the covering of slag which collects upon the surface of the molten metal, and is thus protected from the oxidising influence of the blast, with a consequent delay in the completion of the fining pro- cess, and an increased consumption of fuel and waste of iron from oxidation, besides imposing additional labour upon the workmen engaged in the puddling. 448. No decarburisation of the pig-metal takes place until the graphitic carbon has entered into the state of combination or solution, or until all the grey iron has been converted into white iron ; so that for dry puddling it is a usual practice to submit grey pig-iron to a preliminary treatment in the refinery for its conversion into white or refined metal before passing it to the puddling furnace, and the operation of puddling is always much accelerated by this previous treatment of the pig-iron in the refinery ; whether the metal is to be subsequently treated either by the " dry " or " wet " divisions of the puddling process. 449. The process of puddling for the more or less complete removal of carbon, silicon, sulphur, phosphorus, manganese, and other foreign elements from pig-iron, and the conversion thereby of hard, brittle, cast-iron, contain- ing from 3 to 10 per cent, of impurities, into a compara- Chap. XIV. I PUDDLING PROCESS. 251 tively soft and ductile malleable iron, containing in its first stage as puddled iron (before piling) from one-half to 3 per cent, of impurities, was introduced by Cort in the year 1784 ; and, where mineral fuel is abundant, it has almost entirely superseded the older or open-hearth processes, from which it differs, as previously noted, in being con- ducted upon the bed of a reverberatory or other furnace in which the bed is separated from the grate upon which the fuel is consumed, and whereby the metal and fuel are prevented from coming into contact. The temperature re- quired for the fusion of the pig-iron and its subsequent working is maintained by the flame and heat from the combustion of the gases produced by the fuel in the grate ; so that raw coal and inferior fuels that cannot be used in the open-hearth finery are available for the puddling process ; whilst by the adoption of gas furnaces, wood, brown coal, and peat, either alone or in conjunction with other fuels, are also applicable to the puddling operation ; and thus the puddling process, which was formerly con- fined to districts affording coal at a cheap rate, can now be applied ir districts devoid of coal, if they possess any of the classes of fuel just described, although coal con- stitutes by far the best and most suitable fuel, no matter whether it be for direct combustion on the grate or for conversion into gas to be burnt on the furnace hearth. 450. Notwithstanding that several patented and im- proved puddling furnaces and apparatus will be described in the subsequent pages, yet none of them are in general use, so that the puddling furnace and forge practice, as generally carried on at the present time, do not show during the past fifty years the same advancement as is manifested in the various other departments of the iron industry. The little modifications in the form of the furnace have been directed towards effecting an economy, in fuel, but the largest economy has resulted from the increased output due to the more general use of basic fluxes in the furnace constituting the pig-boiling process ; whilst the use of charcoal pig-iron and refined 252 STEEL AND IRON. [Cbap. XIV. metal have been mostly abandoned. And whilst the loss of iron was formerly about 16 per cent, of the charge, at present the average will be from 8 to 11 per cent., the consumption of fuel having decreased during the same interval to the extent of some 15 per cent. 451. As indicated in the preceding sections, the puddling processes are of two classes. In the older, or " dry-puddling," the oxidation of the elements neces- sary for the conversion of the pig-iron into malleable iron is principally effected by the oxygen of the air drawn by the chimney draught over the surface of the melted metal in the furnace, and assisted only to a smaller degree by the presence of oxidising fluxes or slags, technically termed fettling. In the more modern and, in point of production, by far the more important process known as " pig-boiling," or " wet- puddling," the oxidation obtained during the process is to a large extent effected by the various basic slags, cinders or scale, &c., added to the charge, the oxygen of the air playing only a secondary part in the reactions. Hence, in the pig-boiling process, the decar- burisation being principally effected by the oxides of iron in the cinder or slag, and this reaction being the more active as the basicity of the cinder or its richness in oxide of iron increases ; it follows that, during the earlier or melting-down stage, in which the silicon of the pig-iron is being oxidised by the oxygen of the atmosphere passing through the furnace, and the cinder produced is accordingly somewhat siliceous, there is almost an entire absence of decarburising influence upon the bath of molten metal ; but as the process pro- ceeds, and the proportion of silicon in the pig-iron becomes largely decreased, or almost ra7, then the iron also becomes more rapidly oxidised, whereby the cinder speedily becomes more basic in its character, and the reaction between the cinder or slag and the com- bined carbon of the metal increases in activity, with the copious evolution of carbonic oxide and a correspond- Chap. XIV.1 ELIMINATION OF PHOSPHORUS IN PUDDLING. 253 ing decarburisation of the metal, and the reduction of iron from the slag or cinder. 452. The elimination of sulphur from the charge is always very imperfect in the pig-boiling or wet method of puddling, a portion only of this element being separated and passing into the slag (tap-cinder), where it probably occurs as a sulphide of iron, although the exact form of its occurrence in tap-cinder is very uncertain , but the elimination of sulphur, as far as it goes appears to pro- ceed somewhat steadily from the beginning to the end of the puddling process. The conditions favourable to the elimination of sulphur from the product of the puddling furnace are 1, regularity of working; 2, the presence of a good basic slag or cinder, which it is the object of the puddler to produce by the proper addition of a fettling rich in oxide of iron, oxide of manganese, lime, &c. ; 3, sufficient duration of the contact of the iron with the cinder before the commence- ment of the boil, and hence any delay in the process tends to the removal of a larger proportion of sulphur, as also of phosphorus. 453. The elimination of phosphorus is likewise imper- fect, and the rationale of its separation is not clearly under- stood. However, the fact remains that about 80 per cent, of the phosphorus in the pig-iron under treat- ment passes out during the puddling process, and the tap-cinder produced at the same time always contains a considerable amount of phosphoric anhydride (P 2 O 5 ) (seo analyses, p. 280), and it is suggested by Dr. Percy* that probably the phosphorus first liquates as a liquid phosphide of iron from the metal when it is in the pasty condition, and that it is subsequently oxidised to the condition of phosphoric anhydride. The examinations of the slags, &c., made in Silesia (p. 279) indicate that during the melting down of the pig-iron the phosphorus in the metal is decreased by about one-third, and that subsequently its elimination goes on pretty * "Metallurgy," Vol. II. 254 STEEL AND IRON. fCliap. XIV. uniformly to the end of the process. It is found also that, as the proportion of silicon and phosphorus in the puddled product becomes lower, the proportion of carbon left in the malleable iron by the puddling process is usually higher. 454. Manganese, when present in considerable pro- portion, delays the fining of the pig-iron by preventing the breaking-up of the oxides of iron in the silicates of iron of the cinder added to the puddling furnace, and it thus also promotes the better elimination of sulphur from the puddled product. The analyses just referred to appear to indicate that the manganese is largely separated during the melting down stage, after which the elimination pro- ceeds much more slowly, but it goes on again towards the close of the fining stage. 455. The puddling furnace employed in pig-boiling, as illustrated in Figs. 42 46, has a hearth of the form shown in Fig. 44, with a low flat arch or roof of fire- brick, z (Fig. 43), sloping gradually from over the front wall of the fireplace to the flue at the stack end of the furnace, and which in the small single furnaces is higher at the working side over the door (Fig. 46) than it is at the opposite side. 456. The fire-bridge, a, between the hearth, c, and the grate, b, is formed of a hollow cast-iron frame encased in fire-brick, while a similar bridge, n, across the other end of the hearth is known as the flue bridge, and separates the hearth from the flue and the stack, of which the stack, y, is built of common red bricks lined with fire-brick, and varies much in dimensions according as it is con- nected with one or more furnaces, but for one furnace only it ranges from 30 to 50 feet in height, and is strengthened as shown, by angle-irons up each corner, and well braced together by tie-rods passing around the stack. The stack is surmounted by a damper connected with a lever and chain, the latter brought down within reach of the puddler that he may regulate the draught as required during the working of the process. The outer, Chip. THE PUDDLING FURNACE. 255 or the side and end walls of the furnace, are enclosed within strong cast-iron plates, d, d (buckstaves), bolted together Fjg. 42. Front Elevation of Fuddling Furnace. through suitable flanges, and the plating of one side is connected with that on the opposite side by tie-bolts or rods, passing from side to side over the top of the furnace. 457. The hiarth^ c t in the pig-boiling furnace is about Fig. 43. Vertical Longitudinal Section of the Puddling Furnace. 6 feet in length, but it differs in depth, form, and in the nature of its lining, according as pig-boiling or, dry 256 STEEL AND IRON. [Chap. XIV. puddling is to be conducted thereon. It measures about 3 feet 9 inches in width at the fire-bridge end, and 2 feet 9 inches at the flue-bridge end. The bridge, a, between the hearth and the grate-bars is formed of a hollow cast-iron frame enclosed in fire-brick, and the fire- bars are of the ordinary wrought iron type, readily movable for the removal of any clinker, &c., adhering to them, and they are supported on the usual bearers, t, t. The bottom of the furnace bed is formed of cast-iron plates, of which the exact form and method of supporting varies in different localities; but the plates are often rebated together, and the joints carefully caulked, the whole being supported upon dwarf pillars, bearers, or brackets, as shown in Fig. 43, to permit of the circulation of air beneath them. The sides of the hearth also are variously constructed, but are often formed of hollow castings permitting of their being kept cool by the circulation of air through them ; Fig. 44. Horizontal Section showing Plan of Bed of Puddling Furnace the castings are covered at the top and back by brick- work, which overlaps or projects inwards at the top or upper edge beyond the side castings, so as to form a recess into wliich the fettling, or refractory lining, is introduced for the protection of the side plates. The depth of the fireplace or grate-bars below the bridge varies with the nature of the fuel to be consumed, a greater depth being required for slightly bituminous coals. But the best fuel for the ordinary grate is a non-caking coal containing but little sulphur, and which burns with the production of a long flame that thus plays CLap. XIV. 1 THE PUDDLING FURNACE 257 over the whole length of the furnace hearth. The area of the grate-bars is made from one-third to one-half of the area of the bed, being thus considerably larger in proportion to the area of the bed than is required with the reheating, balling, or ordinary rever- Pig. 45.-End Elevation of Puddling Furuace. Fig. 46. Transverse Section of Puddling Furnace on line A B, Fig. 44. beratory furnace. The firing-hole, h (Figs. 42, 45), is placed in the front or working side, with its sill- plate about 10 inches above the level of the grate-bars ; it is not however closed by any door, but after firing or the introduction of the necessary fuel on to the grate, it is stopped by placing upon the sill of the fire-hole a few lumps of coal, and then throwing over these a shovelful of small coal against the opening into the grate. The working door, w, is placed some 10 inches above the bed of the furnace, and it is closed by a door formed of a large fire-brick tile, slab, or quarry fixed in an iron frame, and suspended by a chain from a lever, I (Fig. 46), at the opposite end of which is a counterbalance weight and suspended chain, whereby the door can be readily raised and lowered for the introduction of the charge and with- drawaj as required of the puddled lulls, and for theso purposes only is the door used, the working of the charge being effected without opening the door by the puddier 258 STEEL AND IRON. [Chap. XIT introducing his bars or paddles through the small rect- angular-arched opening or notch, k (Figs. 42, 46), called the stopper-hole, the sides or edges of which serve as a fulcrum for the rabbles during the stirring and working of the charge. In the large or double furnaces there are two working doors, one on each side, but such furnaces require two sets of men for their manipulation and are altogether equivalent to two ordinary furnaces, but they are more economical in fuel. (*$eep. 270). Below the sill-plate of the working door is the tap-hole, m (Fig. 42), which is stopped with sand during the working of the furnace, and through which the slag (tap-cinder) is withdrawn as needed ; but, besides being tapped from the tap-hole, m, the cinder flows over the flue-bridge during the working of the furnace, and collects at the bottom of the stack. The flue from the flue-bridge to the stack varies in area with the nature of the fuel to be employed ; thus, while for the consumption of bituminous coal the area of the flue requires to be about one-fifth of the superficial area of the grate-bars, for the use of anthracite coal the sectional area of the flue is made but one-seventh of the area of the grate. 458. In some furnaces, in addition to the working hearth, there is also a second bed or hearth, situated beyond the flue-bridge, and between it and the stack. This second hearth serves for heating the pig-iron previous to placing it upon the working bed. In such furnaces the second bed is heated either by the flame on its way to the stack, after passing over the working bed ; or in other furnaces, such as those heated by gas, the gases are burnt on the second hearth by the aid of a hot-blast, the blast being heated by passing the air through the hollow blocks of the sides of the working hearth, and then through a coil of pipes between the furnace and the base of the chimney, before they enter the second hearth for the combustion of the gases. 459. The working bed, v (Fig. 43), or lining of the hearth of the puddling furnace was formerly made of Chap. XIV.1 FETTLING OF PUDDLING FURNACE. 259 sand when dry puddling only was pursued, but for " pig- boiling " or " wet puddling" the lining is made of those refractory substances rich in the oxides of iron, such as tap-cinder or hammer-scale mixed with the broken- up old bottoms of the puddling furnace, such matters aiding by their oxidising character in the conversion of pig-iron into malleable or wrought iron. The bottom is prepared by first introducing on to the hearth a layer of broken slags, tap-cinder or hammer-scales, and of hearth bottoms, and then raising the temperature suffi- ciently to fuse or soften these materials that they may be spread over the bottom to a uniform depth of about 3 inches ; and upon this is placed a layer of about li inch in thickness of a " fettling " consisting of a nearly pure oxide of iron, in the form of a soft red hsematite known by the name of " puddler's mine." The side plates are also fettled or covered with a lining consisting of roasted tap-cinder, or "bull-dog," as it is technically called, which is rammed well in under the projecting rib of brickwork or fire-clay slabs already spoken of as covering the top edge of the side plates. Practical puddlers attach considerable importance to the fettling being fixed as close and dense as possible around the furnace for the production of a cleaner iron. Like the bottom, the sides then also receive a coating of puddler's mine; or, instead of the "bull-dog" previously mentioned, other bodies rich in oxides of iron, as htematite, magnetite, or roasted spathic iron ore free from earthy matters, are also used for fettling the sides ; and for a like purpose " blue billy " that is, purple ore residues derived from the treatment of roasted cupreous Spanish and Portuguese pyrites by the wet process for the ex- traction of copper, and which residues contain about 96 per cent, of ferric oxide, with a little lead, copper, sulphur, calcium, &c. is also used. The fettling of the side plates requires renewal or repair after the working-off of each heat, besides which, after every shift of twelve hours, sufficient scrap-iron is introduced into 260 STEEL AND IRON. (Chap. XIV the furnace to make a ball, which is worked up into a bloom, and during this operation a proportion of the metal is oxidised, thus giving to the bottom a further coating of oxide of iron. ANALYSES OF THE MATERIALS EMPLOYED AS FETTLING FOR THE PUDDLING FURNACE. Bull-dog. Purple ore. Pottery -mine. Ferrous oxide 3-55 46-53 Ferric oxide . 63-90 95-10 Manganons oxide , 2-54 Silicon . 15-75 __ Titanic acid . 10-89 __ Phosphoric anhydr de 93 0-69 Carbonic anhydrid 30-77 Sulphur. . :.--.! 0-35 0-07 Sulphuric acid _ , 0-04 Iron pyrites . " 0-34 Copper . Lead (as sulphate) __ 0-18 1-29 Lime 2-41 Calcium ___ 0-49 Alumina 0-97 Sodium . . _ 0-29 Magnesia 1-39 Insoluble residue 2-13 2-27 Water and organic matter 11-93 99-55 99-88 460, Other substances besides those enumerated in the preceding section are occasionally employed as fettling materials. A good fettling in addition to having the chemical qualities as above should also melt with a clear face, whilst such as crumble away, and thus tend to become mechanically mixed in an unfused condition, with the metal of the puddled ball are objectionable, since it is exceedingly difficult, if not impossible, to expel such matters during the hammering or rolling of the bloom Cliap. XIV.] MANIPULATION OF THE PUDDLING PROCESS. 261 into finished iron, and their presence produces, therefore, laminations of slag in the finished bar. Lime is some- times used for fettling, but anything of a quartzose or siliceous nature is to be avoided, and the best material for the purpose is the best tap that is, cinder from such reheating furnaces as work with cinder bottoms, and are employed in heating the wrought-iron piles for the rolling mills, but not the tap from the reheating furnaces working with the ordinary brick bottom covered with sand. The use of best tap is said to afford good malleable iron even from the poorer pig-irons, and to yield a greater weight of balls or puddled bars than the pig-iron operated upon, the difference being derived from the reduction of a portion of metal from the best tap. 461. Different fettlings* are, however, recommended, according to the class of iron to be produced ; thus, with malleable iron for plates, sheets, bright or polishing iron, a good fettling is formed of best tap, covered with ground bull-dog ; for merchant iron, sections, =m upr \ jected to pres- | pi Mf | sure between I the three rolls, till it assumes the form of a round bloom having the de- sired diameter and the neces- sary consolida- tion, when by raising the top roll the bloom is thrown out from the squeezer, with a little assist- ance from the workman aided by a bar. The bloom is again received on a bogie for conveyance to the forge rolls, into which it is at once introduced for rolling into puddled bar. Fig. 51. Front Elevation of Squeezer for Puddled Balls. Fig. 52. Plan of Squeezer for Puddled Balls. Chap. XVI.l ROTARY SQUEEZER. 305 533. Rotary squeezers may be arranged either hori- zontally or vertically, and they consist of a strong fixed cast-iron casing forming about three-fourths of a com- plete cylinder, with about one-fourth of the circum- ference removed to admit of the introduction of the puddled ball into the machine. The inner surface of this cylinder is roughened by corrugations, or is studded with blunt triangular studs or teeth, while within the outer cylinder another cylinder or drum revolves upon an axis parallel with the axis of the outer fixed casing, but eccentric with regard to it. The outer surface of this inner revolving drum is roughened similarly to the inside of the casing, so that as the inner cylinder revolves the puddled ball is carried around between the roughened surfaces of the inner drum and the outer casing, the space between the two surfaces diminishing in the direction of the rotation from the point of entrance of the puddled ball to its ejection. Owing to the eccentricity of the inner barrel with respect to the casing, the puddled balls introduced at the widest part are carried round by the revolution of the inner drum and forced through the smaller part of the ap- paratus, whereby the particles of the puddled ball undergo a gradual welding together; and finally the ball falls from the narrower end of the machine as a cylindrical bloom ready for passing through the puddling rolls. The inner drum rotates at a velocity of about twelve revolutions per minute and is driven through a bevel wheel and pinion placed beneath the machine, and connected respectively with a driving shaft from some convenient source of power and the axis of the drum. But since the distance between the revolving drum and the casing at any point is always fixed, it follows that the puddled balls to be shingled or squeezed in this machine should be fairly regular as to size and weight, since the larger the ball the greater will be the compres- sion to which it will be subjected in passing through this machine, so that the shingled blooms will not be uniformly U 306 STEEL AND IRON. fChap. XVI. homogeneous if they are produced from different-sized puddled balls, besides which undue strains are put upon the machine if very large balls be passed through it. 534. A special squeezer designed by Winslow and im- proved by Banks has been introduced for working thg large balls produced in the Danks furnace. The squeezer, of which the end elevation is shown in Fig. 53, consists of two corrugated rolls, a, a, of about 18 inches in diameter and 4 feet in length, the necks of which revolve in bearings fixed in strong cast- iron housings or stan- dards, b, whilst above the rolls, on a shaft parallel with them, is fixed a large, ir- regular, or cam- shaped roll, c. The shaft of this roll is connected with each of the two lower rolls by gearing, through which the whole is driven ; so that the puddled ball which is introduced into the machine at the widest or most open part of the cam, and carried downwards by its rotation and by that of the corrugated rolls, is compressed and reduced in diameter as the cam revolves, two revolutions of the cam sufficing to squeeze the ball into a bloom ready for the puddling rolls. The rolls, a, a, revolve at the rate of from fifteen to twenty revolutions per minute, and in the same direction as the cam, c. At the end of the rolls, a, a, are fixed rams or hammers working horizontally, the end of whose tups are formed as shown at d t of a shape that will permit of their passing Fig.53. End Elevation of the Danks- Wiuslow Squeezer. Chap. XVI.) THE TILT HAMMER. 307 into the space above the rolls, and between them and the cam, so that whilst the ball is undergoing pressure between the rolls with reduction in its diameter, the ends are prevented from spreading out unduly by a fesv strokes of these horizontal hammers. 535. An hydraulic squeezer, a modification of the above, is also in use in America ; it consists of two hori- zontal lower rolls and a large irregularly-shaped upper roll, and between the upper and the lower rolls the puddled ball is squeezed. The bloom is thrown in and out from these rollers by hydraulic cylinders placed below. 536. Hammers of various classes are largely employed in the forge both for shingling the puddled ball, and for the working of the finished iron, or of steel ingots intc the various classes of blooms, billets, forgings, tons, are in most frequent use, whilst for forging purposes 312 STEEL AND IRON. [Chap. XVL and especially in the treatment of large masses of steel, hammers of 10, 20, 50, and 100 tons are at work. Figs. 55 and 56 are illustrations of a 4J-ton shingling hammer with cast-iron standards, supplied by Messrs. Thwaites and Carbutt to a South Wales forge. It is double-acting, and has a cylinder, a, supported upon cast-iron standards. Fig. 55. Front Elevation of Double- Acting St earn Pig. 56. Side Ele- Hammer, for Shingling of Puddled Balls and vation of Steam Cogging of Steel Ingots, showing the Steam Hammer. Cylinder, Valves, and Hammer tup in section. Fig. 55 shows the steam-ports, 6, 6, with the cylindrical equilibrium valve, c. The extremity of the valve casing is connected with a pipe opening above the roof of the building for the escape of the exhaust steam into the atmosphere. Thus the steam escapes from the bottom ports, and exhausts through the inside of the cylindrical valve, c, whilst from the upper port the steam escapes Chap. XVI.] THE STEAM HAMMER. 313 directly to the atmosphere as the valve descends for the admission of steam, which enters by the pipe, k (Fig. 56), and circulating in the space around the valve, is admitted alternately above and below the piston as the valve descends or ascends. The valve, c, is easily worked by Fig. 57. Double acting Steam Hammer for general forging purposes. the lever p, whilst the stop- valve between the boilers and the hammer is regulated by the lever q. 545. In steel works a type largely adopted for ham- mering steel ingots into slabs, blooms, billets, and general forgings, &c., is a double-acting hammer of 8 tons or upwards, with wrought-iron square or circular columns UNIVERSITY 314 STEEL AND IhON. [Chap. XVL (Fig. 57) supporting a deep cross-girder of box section, also formed of w rough t-iron plates and angle irons riveted together ; upon this girder is carried a pair of standards of cast-iron fitted upon their inner faces with steel guides working in a corresponding groove in each side of the hammer tup, or, as is now becoming more general, the cast-iron standards are themselves replaced by steel castings. Resting on the top of these standards, and with its centre between them, is the steam cylinder, which in an 8-ton hammer is about 30 inches in diameter and 7 feet stroke, with its piston rod of steel 6 inches in diameter, connected at one end with the piston and at the other extremity suitably connected with the hammer tup, weighing about 8 tons, which tup also was formerly always made of cast-iron, but is now frequently replaced by a steel casting. The movable hammer block, n (Fig. 57), is secured by a dovetail joint and wedges to the tup A of the hammer, the block being first planed on its lower or working face, and carefully fitted into the tup to allow of its ready removal and change, as is very frequently required. The slide valve of these hammers is a hollow cylindrical-balanced valve, c, Fig. 55, easily worked by a lever under the control of the hammer driver, whilst the stop valve for opening or closing the passage for steam between the boilers and the valve casing is controlled by a second lever, also within the driver's reach. 546. The foundations for steam-hammers are required to be of the best, heaviest, and most substantial description, especially for the larger hammers. Such foundations are usually formed first of a layer of concrete, or of concrete on wooden piles driven as far as possible into the earth ; upon the concrete are placed cast-iron bed-plates of weights pro- portionate to the size of the hammer ; or, in heavy hammers, it is usual to alternate heavy cast-iron plates with balks of oak timber arranged in various ways, and upon this foundation are finally fixed the heavy anvil- block or blocks, of cast-iron, into which the working bottom anvil block, m (Fig. 55), is fitted by a dovetail joint Chap. XVI.] THE HASWELL FORGING PRESS. 315 and wedges in the same manner as the to-p anvil or block is fixed in the tup of the hammer. As indicating the massive character of steam hammer foundations, it will suffice to note that the bottom anvil block for a 10- toii double-acting hammer weighs about 110 tons, whilst the superstructure of hammer and base plate of the same hammer weighs only about 80 tons. 547. Jtamsbottom's duplex or horizontal hammer con- sists of two horizontal blocks or tups, each of considerable weight, which are supported upon friction wheels running upon rails. The horizontal blocks or tups approach to- wards, and separate from, each other alternately as the hammer is worked, for whichpurpose they are connected by a system of links with a vertical steam-engine fixed below the ground, and so underneath the hammer ; or, instead of the link connections and a single engine, it is usual with the larger hammers to work each of the tups directly from a separate steam-engine, in which case it is necessary to apply u mechanical arrangement, whereby it is ensured that the two sliding tups approach the work at the same velocity, and strike it at the same time. Thb duplex hammer is without anvil, the work being supported on a carrier or carriage between the tups, which should thus strike the work simultaneously upon its two opposite sides. This hammer has not, however, been very fa- vourably received, nor generally adopted. 548. For the production of forgings, &c., in iron and steel, by compression instead of by impact from the blows of the steam hammer, more elaborate and refined tools have been introduced, in which hydraulic power has been largely brought into service. Of such machines are the powerful hydraulic forging presses of Sir Joseph Whit- worth and Co., and the smaller presses of Mr. Haswell, of Vienna, while particular modifications of such plant occur in the various special presses employed for flanging and bending plates now in extensive use for the finishing of boiler and ship's plates for the engineer. 549. The Haswell press is not capable of the general 316 STEEL AND IRON. [Chap. application to which the Whitworth presses are applied, its operations being confined to specific purposes, such as the forging of wheels, axle boxes, flanging, v X i > : t -4 -J "i" U, 4. z \ t ! T 'I -i---| L 58. Front and End Elevation of Sir J. Whitwoirtih and Co.'s Hydraulic Forging Press. 318 STEEL AND IRON. fCliap. XVI of 2,000 tons. Such a press has a massive cast-iron base, z, Fig. 58, and four steel pillars, u, u, (or two pillars in the smaller presses) secured as shown. The pillars are screwed with a square thread along the upper half of their length, while upon the top of these pillars is the cast- iron head or table, b, carrying the hydraulic-lifting cylinders, c, c, the rams of which are fitted into cross- heads connected with rods, e, e y which pass through the moving head, /, and are attached to the plates, g, which are bolted to the under-side of the forging ram work- ing in the large hydraulic forging cylinder, k, carried in the moving head. Thus, as water is admitted or dis- charged from beneath the rams, c, the moving head is raised or lowered, so as to regulate the distance between the under-surface of the pressing ram and the work on the anvil, whereby only a short stroke of the forging ram is necessary at any time. During the application of the pressure for forging, the resistance is received by the columns, u, through the locking nuts, t /, j, which, by suitable mechanism are brought during the working of the press into firm contact with the moving head, f. The quick pitch screws, , s. with the wheels, <, as also the spur wheels, v, v, on the periphery of the locking nuts, j, j, are so geared together as to automati- cally rotate the locking nuts, j, j, upwards or downwards as the moving head is lifted or lowered, by the lifting rams, e ; and the same mechanism serves for finally bringing the nuts tight against the moving head, after it has been placed at the desired height from the work under treatment. The forging or pressing cylinder, 7 c, is carried by the moving head,/, and the necessary power for forging is obtained by admitting water from the force-pumps to the top side of the forging ram, which thus descends upon the work on the anvil and effects the desired compression, whereupon the upward or return stroke of the ram is promptly and automatically effected by the rams, c, c, connected, as already described, with the plates, g. During the working of the press, the CLap. XVI.] THE FORGE TRAIN OF ROLLS. 319 bottom of the rams, c c, is maintained in constant com- munication with the pressure of water from a small accumulator, so that immediately the higher pressure is taken off the top of the forging ram and the water is allowed to escape from the forging cylinder, then the rams, c, c, ascend, and make the upward stroke of the forging ram, the next stroke being simply effected as before, by the admission of the water from the pumps on to the top side of the forging ram which again descends upon the work. In this manner the strokes of the press follow in comparatively quick succession, the work under treatment being moved and manipulated as re- quired, between the strokes of the press, exactly as with the steam hammer. 551. In working with hydraulic forging plant, the anvils and movable bottom faces of the forging ram may be either flat, as is usual with steam hammers, or the face may be modified so as to be more effective in their opera- tion, since in the slow application of pressure the anvils are not so frequently broken as would occur if the same forms of anvil were subjected to the impact produced by the stroke of the steam hammer. 552. The Rolls employed for the conversion of the shingled bloom of malleable iron into puddled bar, or into merchant bars, plates, sections, , p, are on the outside of the housings and suspend the bearer, k, from two lugs cast for this purpose on the side of the standards. The power of the engine is transmitted through a claw-clutch or crab on the end of the engine shaft, and thence through a spindle to the lower pinion of a pair which run in their own standards, while the wabbler ends, a, a, of the pinions (Fig. 59) are connected by spindles and coupling-boxes or wobblers with the ends of the roughing rolls ; the other projecting or wabbler ends of the two roughing rolls being in like manner coupled by boxes and spindles with the near ends of the two finishing rolls ; or, as is sometimes 326 STEEL AND IRON. [Chap. XVL done, only the lower finishing roll is connected by a spindle with the lower roughing roll, and motion is then imparted to the top finishing roll by gearing fixed on the outer projecting ends of the two finishing rolls. This latter method of driving from the lower roughing roll only has the advantage of permitting the use of larger or smaller roughing rolls, as may be desired, with- out interfering with the finishing rolls. 560. In rolling small and light sections, which are therefore whilst hot very flexible and difficult to keep from bending and twisting during the operation, it is usual to provide an apron or fore-plate in front of the rolls, as also guide jaws for directing the work straight as it enters the rolls, in which manner much of the twisting is avoided, and the train so provided is hence known as a "guide train" and the iron produced therein as " guide iron." 561. In rolling sections, bars, &c., the bottom roll is always provided with " stripping -plates ; " these are plates of iron which rest at one end in a cross bar supported by the roil standard, and at the other end upon the roll itself. They are shaped to fit into the several grooves of the rolls, and are also bevelled off at their lower edge so as to fit on the circumference of the roll, with their upper surface tangential to the surface of the roll. They thus act as chisels or wedges in clearing the bars from the grooves of the bottom roll, thus preventing " collaring," or wrapping of the bars around the bottom roll. 562. In two high trains revolving constantly in one and the same direction it is, as already explained, necessary to return the work over the top roll from the back to the front of the rolls, after each pass of the work between the rolls ; and thus much time and labour is lost, to over- come which either " three high rolls " or mills that can be reversed at each passage of the work have been largely adopted for the mill-trains. 563. In the case of reversing mills the reversal is effected either by reversing the engine itself, as Chap. XVI.] THREE HIGH ROLLS. 327 introduced by Mr. Ramsbottom for the rolling of rails, &c., or by the introduction of hydraulic, friction, or other clutches and gearing on the engine shaft, whereby the rotation of the rolls is reversed whilst the engine continues its revolutions always in the same direction. 564. For lifting the work to the top of the upper roll in the two high non-reversing mills, it is usually sufficient when light work is being rolled to receive it as it issues behind the rolls upon forked levers suspended from a travelling carriage above, and by which the workman raises the bar to the required level, so that the roller-man in front of the rolls may seize it with his tongs and draw it forward on to the fore-plate of the mill for insertios into the next hole of the rolls ; but where heavy sections or plates are rolled, some two high plate mills have movable fore-plates or feed-plates fitted to the mill, so that as the work issues from behind the rolls it is re- ceived on this plate, which is at once raised to the re- quired level by a single-acting engine, or by an arrange- ment of levers worked either by hand or by power, 01 the table is elevated by an hydraulic cylinder and ram. The work thus elevated is drawn over the top rolls to the front side of the mill, ready for its reintroduction between the rolls. 565. Three high rolls, introduced more particularly into mills for rolling light work, such as merchant or guide iron, but also adopted in some rail mills, consist of roughing and finishing rolls, each of which is a combina- tion of three rolls in its own pair of housings. With three high rolls the mill is usually driven from the middle roll, although under special circumstances it may be driven from the lower one that is, the engine shaft is coupled with the middle or lower pinion respectively, according to which method is pursued. In the three high train there are thus three pinions through which the rolls are driven, the wabbler ends of the pinions being coupled as before by spindles and coupling-boxes with the ends of the three 328 STEEL AND IRON. [Chap. XVL rolls : and the middle roll therefore revolves forward with the lower one, and backwards with the upper one, or vice versd, according to the direction of rotation of the middle roll, so that the work thus passes backwards and forwards alternately through the grooves or holes between the middle and bottom rolls, and between the middle and upper rolls re- spectively. The work, as it issues from the grooves in the lower rolls, is received and lifted (either by levers, or by a table ascending with the work, in the manner already described) to the level of the holes between the middle and upper roll, after passing through which the bar is received on the other side by a corresponding arrangement, and immediately lowered to the level of the lower pair of rolls. 566. In three high mills various mechanical arrange- ments are made for adjusting the distance of the top and bottom roll from the middle one. In two high mills, the top roll is movable for the purpose of adjustment, but in the three high system either the middle roll may be fixed and the top and bottom rolls run in adjustable bearings, or, as in Fig. 63, the bottom roll is fixed, and the middle and top rolls are carried in adjustable bearings. A three high 15-inch train for rolling merchant bars upon the first system with movable top and bottom rolls, has the bolsters or bearers 011 which the journals or necks of the middle roll work fixed solidly by bolts to shoulders in the housings or standards; while the top and bottom rolls are raised or lowered simultaneously towards the middle or fixed roll by four housing screws, two in the top for holding down the top roll, and two in the bottom for elevating the bottom roll, and these four screws may all be revolved together by means of vertical shafts and attached gearing. The gearing revolves continually from the mill engine, but by an arrangement of belts and a friction clutch in connection with them, the housing screws are made to revolve in either direction or to remain stationary, and in this manner all four screws Chap. XVI.] THREE HIGH ROLLS. 329 revolve at once ; but a greater degree of accuracy, especially for light work, is attained where means of adjusting the top and bottom rolls separately is adopted. In some English mills, like that illustrated (Fig. 63), the bottom roll is fixed and the other two rolls are adjusted by wedge- Fig. 63. End Elevation of Housing for Three High Rolls. shaped blocks, a, placed respectively beneath and above the bearers of the middle and top rolls, so that by turning the nuts, 6, on the screwed ends of the wedges, they are drawn inwards or moved outwards, and so the position of the rolls adjusted. 567. In most American three high trains for merchant iron, the top and bottom rolls are grooved. 330 STEEL AND IRON. [Chap. XVI (Fig. 64), and the middle roll has the collars turned upon it, instead of grooving the bottom and middle rolls, as is often practised in England. The American plan requires shorter rolls for the same number of passes, and also does not necessitate turning over the bar after each pass, the grooves opening alternately upwards and downwards, so that the fin that was formed in the top groove in the upper pass is smoothed down by the solid bottom of the groove in the upper pass. One of the mosl prominent diffi- culties and ob- jections to the three high mills arises from the necessity of pro- viding between the middle and top rolls suspended and balanced stripping-plates for turning the work out oi the grooves as it issues from the rolls. 568. In plate mills, the general arrangement of the mill is the same as that illustrated by Figs. 59 and 60, except that the rolls are plain cylinders of uniform diameter throughout, instead of being grooved in the manner described for rail and other mills rolling mer- chant iron. And also the top roughing roll is balanced by counterweights in the manner shown in Fig. 65, whilst the top finishing roll is not coupled by spindles with the roughing rolls but runs freely, being revolved only by the friction of the work passing between it and the bottom roll. The plate mill consists, as before, of two pairs of rolls varying in different mills from 20 to 36 inches in diameter and from 4 to 9 feet in length. The Fig. 64. Three High Eolls for Merchant Iron. hap. PLATE MILL ROLLS. 331 roughing rolls are grain-rolls that is, such as are cast from a tough quality of cast-iron, not chilled on the surface Fig. 65. End Elevation of Plate Mill Housing, showing Balance Weights for Top Roughing Roll. whilst the finishing rolls are chilled castings, of which the chill extends to a depth varying between j inch and 1J inch. All the rolls run in brass bearings and are carried in housings, in the top of which are fitted nuts, a, and 332 STEEL AND IRON. [Chap. XVI. setting-down screws, b, the movement of the setting- down screws being effected either by hand or by power. When the former plan is adopted a large hand-wheel, d, is fixed to the head of each screw, the degree of rotation being indicated by a pointer and a graduated ring, c, fixed on each housing, so that the workman may see that both screws are set down to the same degree, so giv- ing the same thickness to both edges of the plate as it passes between the rolls. Instead of the screws being actuated by hand, spur and bevel gearing governed by a self-acting arrangement for feeding down uniformly both screws at once is also applied, especially to the larger mills, while such self-acting motion becomes necessary when tapered plates are being rolled, in order that the rolls may be uniformly and gradually fed down to give the desired decrease in thickness from end to end of the plate as it passes between the rolls. The top roughing roll rests in a bolster, g, supported upon bars, h, h, which are con- nected with a system of levers, k, I, and balance weights, M, (Fig. 65), suspended beneath the bed plate or foundation of the rolls, and which balance weights are sufficient to lift the top roll, as the feed-screws are turned back, and so to keep the roll constantly in contact with its top bearing, thus preventing the fall of the top roll on to the bottom roll as the bloom or slab leaves the rolls after each passage between them. The balancing of the top roll also admits, without difficulty, of the introduction between the rolls of a pile, bloom, or slab of 4, 8, or 10 inches or up- wards in thickness. The finishing rolls have as a rule much less work put upon them than the roughing rolls, since the former usually reduce the plate but a fraction of an inch below what has been effected in the latter, but being truer on the surface than the rough- ing rolls they take out the buckling and any irregularities of thickness from the rough plate. The top finishing roll runs loose in its bearings and is neither balanced nor coupled by either gearing or spindles with the other rolls, Chap. XVI.] THE PLATE MILL ROLLS. 333 but revolves solely by the friction of the plate passing beneath it, as the plate is carried through by the rotation of the lower roll ; and the upper roll thus drops clown through the thickness of the plate on to the lower roll as the plate leaves the rolls after each pass. The dis- tance apart of the rolls is diminished at each pass by screwing clown the feed-screws, and in mills which do not reverse the plate is lifted by the arrangement of movable table already described, and passed over the top of the rolls to the front side, to be again inserted between the rolls. To overcome this loss of labour and time in the manipulation of the plate, reversing mills have been most extensively adopted, in which the plate passes between the rolls in one direction and returns in the opposite. The plates after passing between the rolls from front to back are received at the back side on a horse or platform inclined towards the rolls, the horse being fitted with friction rollers over which the plate moves as it is delivered from the rolls, so that when the mill is reversed the plate is easily pushed forward with the aid of tongs or bars down the inclined surface of the horse and so into the rolls, thus returning to the front side of the rolls where it is received on a bogie, which runs out with the end of the plate as it issues from the mill. The plate is thus easily passed backwards and forwards through the mill, the rolls being reversed and the screws set down to diminish its thickness at each pass, until the desired thin- ness has been attained, upon which the plate is conveyed to the mill floor in the vicinity of the shears, where it is laid down to cool and straighten if necessary. 569. In plate-mills and two high mills generally the top roll, as measured around the surfaces in contact with the metal, is made slightly larger than the bottom roll, so that the upper surface of the metal as it is rolled is thus extended a little more than the under surface and in this manner the leading end of the plate tends to curve downwards as it leaves the rolls ; thus collaring around 334 STEEL AND IRON. [Chap. XVI. the top roll is prevented, and stripping-plates are fitted as already described for preventing collaring around the bottom roll. 570. In passing through the plate-rolls the exten- sion of the metal is almost wholly in the direction of its length, since, owing to the gripping together of the two rolls there is but little if any extension in' width. Hence the bloom, slab, or pile, as the case may be, is first passed between the roughing rolls in the direction of the breadth of the plate so as to extend it to the full width required, after which the plate is turned round and passed into the rolls in a direction at right angles to its previous direction, or in the direction of its length. The opera- tion of rolling is then continued by passing and repass- ing the plate through the rolls with a continued reduction in its thickness and a corresponding extension in its length, until the thickness required before transferring it to the finishing rolls has been attained, upon which the rough plate is passed to the harder and truer finishing rolls for finishing accurately to the requisite thickness ; after which the plate is laid upon the mill floor to cool preparatory to transference to the shears, where the ends and sides are cut, as may be necessary, to reduce the plate to the necessary dimensions. 571. With iron plates formed from piles built up in a special manner, the plate is passed through the roughing rolls in the direction of its length and breadth al- ternately (with the object of attaining as much uniformity as possible in the strength of the plate in the two directions of its length and its breadth), until the full width of plate has been attained, after which the rolling is continued entirely in the direction of its length. 572. Sheet mills are similar in arrangement to the plate mills, except that the rolls are lighter and the me- chanism required for manipulating the work at the rolls is neither so heavy nor so extensive. The sheet mills of Birmingham and of South Wales have rolls varying usually between 18 and 22 inches in diameter and from 3 to 6 Chap. XVI.] ANNEALING OF SHEETS. 335 feet in length, and run at from thirty to thirty-five revo- lutions per minute. For the production of the larger sheets in such mills, the billets employed are about 1 J inch in thickness, and two of them are usually undergoing the rolling operation at the same time, passing between the rolls crosswise from the front side and then being returned by the back-hand over the top of the rolls to the front side, whilst the screws are set down to reduce the space between the rolls after each passage of the work. The plate is in this manner reduced to about -J-inch in thickness, when the two plates are placed one upon the other and passed together through the rolls for a few times, until finally two sheets each about 3 feet 6 inches wide by 5 feet in length are produced. The sheets are then annealed at a red-heat and, after reheating, are again returned to the rolls in pairs and further extended in length and diminished in thickness ; whilst if the sheets are to be very thin each one is again doubled upon itself crosswise, reheated, and again rolled. The sheets thus produced are put on one side to cool, after which they are sheared to size, again annealed, and finally made into bundles for sale. 573. The annealing just mentioned is effected by placing the sheets in wrought-iron or steel annealing pots or boxes, which, when filled, are run into a reverbe- ratory furnace and allowed to remain there for about twenty-four hours. The annealing pots vary greatly in size, some of the larger ones holding as much as eighteen tons of sheets, each 1 feet long, while the box for holding the same measures about 10 feet 6 inches in length, 5 feet 6 inches in depth, and 3 feet 6 inches in width. Such pots are charged by first piling up the sheets on a base plate, over which the cover or pot is turned and dropped as a cover over the pile, the box so prepared being luted up with clay around the joint of the cover and base plate. The whole is then inserted into the furnace, and heated as above, after which such a pot requires about four days to cool down after withdrawal from the furnace, before 336 STEEL AND IRON. [Chap. XVI the sheets are ready to be withdrawn. Very much smaller pots than the above are in use in South Wales for annealing purposes. 574. The so-called Universal or Belgian mill for Pig. 66. Universal or Belgian Boiling Mill. rolling plates and bars, has two horizontal rolls, a, a, running in standards or housings, and geared together in the ordinary way; but the mill has in addition a pair of vertical rolls, 6, b (Fig. 66), working in front of the horizontal rolls. The top horizontal roll is balanced by Chap. XTI.l SPEED OF ROLLING MILLS. 337 counter-weights, c, c, after the manner of the plate-mill, so as to keep the roll against its top bearing. The distance between the rolls is regulated as usual by screws work- ing through nuts in the top of the housings, which screws receive the necessary rotation either by two separate hand-wheels, or, as is more commonly the case, they are connected by suitable gearing with a shaft, e, actuated by one wheel, d, which is rotated either by hand or by steam power. The vertical rolls work upon slides, and can be moved towards each other or apart from one another by a right and left-handed screw, k, &, working in nuts carried upon the housings or bearings respectively of the two vertical rolls, and actuated by means of the worm-gearing, h, h, moved by a hand-wheel, m, which is under control of the workman. The vertical rolls are rotated from the driving pinion, g, of the mill through spur and bevel gearing so arranged that the bevel wheels slide along their shaft, and thus follow the lateral movement of the rolls as these are either separated or brought closer together. The work as it passes through these rolls is com- pressed on the edge by the vertical rolls and on the flat between the horizontal rolls ; so that a mill of this class may be employed for the production of a considerable variety of sections of flat bars by simply adjusting the horizontal and vertical rolls to the thickness and width respectively of the bars required. 575. Four high rolls have been employed for small mills with some measure of success in the rolling of wire rods for fencing and other purposes where small rolls only are required, but such mills are obviously imprac- ticable for heavy work. 576. The size and speed of mills differ widely, accord- ing to the work upon which they are employed ; thus whilst reversing mills for rolling heavy plates with rolls of from 20 to 36 inches in diameter revolve only at the rate of twenty-five or thirty revolutions per minute, the smaller mills, producing merchant bars or guide iron, w 538 STEEL AND IRON. {Chap. XVL with rolls of from 12 to 18 inches in diameter, are generally speeded to run at the rate of from 80 to 125 revolutions per minute ; and the still smaller mills, such as those rolling billets into wire, with rolls of from 8 to 12 inches in diameter, run at from 250 to as much as 500 revolutions per minute. The roughing rolls, again, in reversing mills rolling iron rails, and having rolls of from 20 to 24 inches in diameter, run at about 30 revo- lutions per minute, although when the mill is non-rever- sing, the speed considerably exceeds this figure. Mills rolling steel usually run 25 or 30 per cent, faster than the corresponding mill working upon iron, while the power required to roll steel, largely owing to the much lower temperature to which the metal is heated, is con- siderably in excess of that necessary to roll the same section in iron. 577. In rolling steel rails at the Crewe Works the mill runs at the rate of forty-five revolutions per minute, and a 1 J-inch steel ingot is cogged down in the roughing rolls, and is completed in the finishing rolls at the same heat into a 30-feet rail weighing 84 Ibs. to the lineal yard, passing seventeen times through the grooves of the rolls during the operation, and occupjdng altogether about two minutes for its completion. It may be noted in pass- ing that when the rail leaves the finishing rolls it is carried along upon a series of five rollers in the floor opposite the rolls, (and which are revolved by suitable power and gearing,) to a circular saw of 8 feet in diameter, where the ends are cut square and to the exact length, and sub- sequently, after the rails have become cold, they are straightened in a horizontal straightening press, and then passed on for drilling at either end under double- drilling machines, as required for the fish-bolts. 578. The usual time occupied in England in rolling a double length of steel rail with six roughing and five finishing passes is a little over two minutes. In the American mills, driven feed -rollers like those just mentioned for receiving the rail from the mills are Chap. XVI.} THE SLITTING MILL. 339 employed both in front and in the rear of the rolls wherever heavy work is manipulated. 579. In some of the American mills rolling steel rails, the rails are rolled in a single length of 90 feet, sufficient for three ordinary 30-feet rails, into which lengths the long rail is cut by the hot saw. For this purpose the Bessemer ingots are cast 14 inches square and weigh about one ton each; such ingots, after reheating, are passed to a three high blooming or cogging mill running at the rate of forty or forty-five revolutions per minute, and through which the ingot makes from eleven to thirteen passes in from one and a-half to two minutes, producing a 7-inch bloom which, as it leaves the last roughing pass, is transferred by the rollers, previously described, to the rail or finishing mill, consisting of a 21- to 24-inch train, running at seventy-five revolutions per minute ; through this mill without any reheating the bloom makes other seven or nine passes, issuing as a 90-feet rail, which is then cut up into three lengths by the hot saw. The whole operation between the reheating furnace and the rail bank occupies but from three to four minutes, and when cold, the rails are transferred to the drilling machine. In some mills of recent date, both English and American, the rails are rolled in lengths suitable for cutting into four ordinary 30-feet rails. 580. The slitting mill for the production of " slit " or " nail rods " consists of a pair of rolls, housed in the usual manner, but which are made to act as a compound shearing machine, for which purpose collars acting as circular cutters are specially turned upon the rolls ; or, instead of being turned upon the roll itself, separate steel collars or discs are fitted upon a spindle or arbor, stops being introduced between the discs for keeping them apart to the required distance. The discs or collars are so arranged that those on the upper roll fall into the space or groove between the collars on the lower roll, leaving however sufficient space between the top of the disc and the bottom of the coiresponding 340 STEEL AND IRON [Chap. JTVX groove to admit of the thickness of the metal that is being cut by the mill. Flat bars pushed into such a mill in the same manner as they would be between the rolls of an ordinary mill, are divided or cut during their passage through the rolls, so as to be delivered at the opposite side or rear of the mill as a series of bent and twisted strips or rods of rectangular section, requiring to be straightened by hand and made into bundles, when they are ready for sale to the nail forgers. The bars, on entering the slitting mill, are steadied by guides, and the cutters are cooled by water continually running over them. 581. Rolling mill engines vary considerably in type and power ; they are made direct-acting, high-pressure, either non-condensing, condensing or compound, while both vertical and horizontal types are employed ; but non- reversing, high-pressure, non-condensing engines with heavy fly-wheels, are usually adopted for the smaller milk rolling merchant and guide iron in two or three high mills; whilst for the heavy mills producing iron and steel plates, rails, heavy angles, sections, and the like, reversing mills are the more usual. 582. Reversing Mills are usually driven by horizontal engines either of the high-pressure or of the compound type ; such engines being fitted either with variously designed friction clutches, hydraulic clutches, differential gear, &c., for effecting the reversal of the rolls whilst the engine moves constantly in the same direction; or, as is more general, the engine itself for reversing mills is reversed at each pass of the work between the rolls, according to the plan introduced by Mr. Ramsbottoni, and hence generally known as the Ramsbottom reversing mill engine, but it is altered or modified to suit the special conditions of different mills. A pair of recently constructed high-pressure and non-condensing engines of this type are represented in Fig. 67. The pair of engines are coupled to two cranks placed at right angles on the same shaft, upon which is also a steel pinion, p, gearing into a steel wheel, w, on the second motion shaft, the latter being in line with the bottom roll 341 342 STEEL AXD IRON. [Chap. XVI of the train of rolls ; and the end of the engine shaft is coupled by a claw-clutch or crab through a spindle and coupling-boxes with the mill pinions, and so on to the rolls of the mill. The gearing is about three to one, so that the engine makes three revolutions for each revolution of the mill rolls. Such an engine is without fly-wheel, and is reversed each time that the heat passes through the rolls and so rotates them alter- nately in one direction and then in the other. For this purpose the engine is fitted with a slot-link valve motion, and the reversal is effected by the driver, who sits either alongside of the engine or on an elevated platform above, so as to be able to see the movements required, and, by moving over the two levers, d, d, one con- nected with an equilibrium valve on the steam main, and the other with a small steam cylinder for reversing the engine, he is able, by first closing the steam valve with the one lever, and then by moving the other lever which works the small steam cylinder just mentioned, and so reversing the link motion, to control the engine; while at the same time the too sudden reversal by the small reversing cylinder is prevented by the introduction of a water cylinder or cataract arrangement, which, along with the reversing engine, is placed between the pair of engines. 583. Reversing engines are now made also somewhat extensively upon the compound type; a pair of such engines, erected for rolling steel plates, having a pair of high-pressure cylinders of 24 inches in diameter, connected with two low-pressure cylinders of 44 inches diameter. 584. At the Crewe works a three high rail mill, the cogging rolls of which are fitted with rising and falling hydraulic tables for lifting the work to the level necessary for passing the work between the middle and lower or between the middle and upper roll respectively, is being driven by a Corliss engine with 4-feet cylinder and 5-feet stroke. 585. For driving a single-sheet mill with 20-inch rolls, at thirty-two to thirty-five revolutions per minute, a non- Chap. XVI.] PILING FOR MERCHANT IRON. 343 condensing engine with 27-inch cylinder and 5-feet stroke, having a fly-wheel weighing 10 tons, and running at seventy revolutions per minute, has been applied ; or, foi driving a double-sheet mill under like conditions of speed and pressure of steam, an engine with 35-inch steam cylinder and 5-feet stroke, with a fly-wheel of 70 tons in weight, is in use ; while, as another example of the power required to drive a sheet-mill, may be cited an engine at work at Messrs. Morewood's, Birmingham, for driving a 21-inch mill making thirty to thirty-five revolutions per minute, and capable of rolling sheets of 4 feet in width and of 30 B. W. G. in thickness, in which the steam cylinder is 30 inches in diameter, with a 5-feet stroke, and works direct without the intervention of gearing, and has a fly-wheel 25 feet 6 inches in diameter and 60 tons in weight. It is calculated that in a mill such as the last mentioned a force of about 400 tons tending to separate the rolls is exerted during the process of rolling the above sheets. 586. The method and particular arrangement observed in building up or piling the bars and slabs of malleable iron into packets or piles for reheating and welding together into a solid mass, either under the hammer or in the rolls, or by a combination of the two processes, varies for every class and quality of work, and for the same kind of work different makers also follow different practices often peculiar to themselves. 587. For the production of No. 2 iron the bars of No. 1 are cut up into lengths, and the pieces so obtained are ar- ranged, if for the production of the larger sizes of merchant iron, into the form of a pile or stack of some 6 or 8 inches square and from 30 to 40 inches in length, such piles averaging about 4 cwts. each, and their constituent bars are placed so that the joints of the several bars do not fall one above the other, but always cross or break joint. The pile so formed is held together by an iron hoop, and after being raised to a welding heat in the reheating or balling furnace, the several bars of tho pile are welded 544 STEEL AND IRON. [Chap. XVT. together by passing the pile through grooved rolls in the manner already described ; or the welding together may be effected by first hammering and subsequently drawing the hammered bloom into bars by passing the same through the grooves of the bar or guide- mill. For smaller bars the piles of about 100 Ibs. each are only about 18 inches long and from 3 to 4 inches square, formed from flat bars of about J inch in thickness but, as already noted, p. 324, billets are more generally used for these smaller sizes. 588. In like manner, for the production of iron plates the piles vary in size with that of the plate to be rolled, but the pile is formed by placing the component bars in layers, of which the bars in one layer are placed across those of the layer beneath, and so on until the whole pile is built up to the top layer, which is covered like the bottom by a slab of about 1^ inch in thickness, and of a length and width .suitable to the dimensions of the par- ticular plate which it is designed to produce. Scrap and crop-ends are also built up along with the puddled bar in these piles. 589. For iron rails, again, some eighteen or twenty pieces of puddled bar, each about 3 inches wide and -fth inch in thickness, are arranged along with scrap-iron in the middle of the pile, while the top and bottom iron plates or slabs are each formed either of a plate of No. 2 iron of 6 or 7 inches in width and 1 inch in thickness, or of a puddled bloom which has been already doubled over upon itself, and previously rewelded. Care is observed in rolling such a pile that it be so passed through the various holes of the rolls that these top and bottom plates are eventually rolled into the two heads of the rail. 590. As already noted, for the production of No. 2 and the higher qualities of iron, as also of plates, rails, tees, angles, &c., in malleable iron, the puddled bar, after being cut under the shears into suitable lengths, is piled along with scrap-iron, crop-ends, &c., into piles for re- heating, welding together, and drawing into bars, &c., in Chap. XVI.] PILING FOR RAILS. 345 the mill rolls. This process of piling is not carried on at random, but a regular method of placing the bars is observed, and in many works special care and attention are paid to the quality of the iron introduced into the several parts of the same pile, as also in the arrangement of the constituent bars with regard to the section to be rolled, so as to produce the best result as to strength and ductility, both with and across the fibre or grain of the finished iron after welding up and rolling. 591. In the production of small round or square bars of merchant iron, the piles, after heating and hammering or rolling into square bars of 1 J inch or 2 inches square, are then cut under the cropping shears into lengths or billets of from 12 to 24 inches according to the weight of bar required, and these billets are afterwards reheated in a small reheating furnace, which is kept filled by the introduction of cold billets as the others are heated and withdrawn for rolling in the finishing rolls into small bars. 592. Since, in the welding together of the component bars in a pile, butt joints unless covered by other bars or plates do not weld properly, it is usual to form the top and bottom members of such piles by single bars or slabs. Thus, in piles for rails the top and bottom layers are made up of slabs produced by the doubling over and welding together under the hammer of two or more puddled blooms, without the same having been previously rolled into bars in the puddling mill ; but the hammered blooms so produced are reheated and rolled into the desired slabs. The ends of the bars, for like reasons as to difficulty of welding, should be cut square, and the bars should also be as free as possible from all scale, dirt, rust, or other foreign matters which interfere with the welding together of the constituent bars of the pile, and hence with the homogeneity of the finished bar. 593. The piles, as made in South Wales, for rolling into rails weigh about 15 cwts. each, and four of these are placed at the same charge into the reheating furnace, 346 STEEL AND IRON. [Chap. XVL and the heat (charge) is rolled into blooms, which are then returned to the furnace for about thirty minutes to be again reheated, after which they are passed to the mill, and in nine passes through the rolls such blooms become finished rails ready for cutting to length, and subsequently drilling or punching for the fish-plate bolts. 594. With steel the above operations of piling and reheating for welding are not carried on, the steel being always cast into an ingot of sufficient weight for the pro- duction of the desired bar, plate, rail, &c., and which ingot is usually reheated before rolling, unless, as in the arrangement of Mr. Gjers, the large ingots required for rails, &c., are placed in "soaking pits" (p. 382 ), whence they are directly transferred to the hammer or rolls as the case may be, to be drawn down into blooms and slabs, and then either at the same heat or after reheating, are passed to the mill for rolling into rails, plates, bars, etc. For the heavier classes of work, such as rails, &c., the practice of cogging and rolling direct from the ingot without the intervention of the hammer has become universal ; whilst for the production of the heavier class of plates this practice is also coming more and more into favour. For the treatment of such heavy steel ingots in- the cogging or roughing rolls, either after reheating or direct from the soaking pits, very large and strong rolls are required, and such are now being introduced for this purpose up to 36 inches in diameter. 595. The crop-ends of rails, angles, heavy sections, bars, &c., are cut off immediately the work leaves the rolls and whilst the metal is still hot ; for which purpose the rail or bar, &c., is drawn from the rolls to the front of a circular saw of from 4 to 8 feet in diameter, and which runs at the rate of from 800 to 1,200 revolutions per minute. The saw is carried in a swinging frame which can be moved out towards the work by a rack and pinion arrangement controlled by the workman, which thus, amid a shower of sparks, rapidly cuts across the work, leaving the ends comparatively clean and square. Chap. XVI.] SHEARS FOR CUTTING PUDDLED BARS. 347 596. Puddled bars are also generally sheared hoi either by crocodile or guillotine shears into lengths suitable for piling, &c., and such shears are likewise employed for cutting up the bars that are not cut up by the hot saws, as also for cutting off the rough or crop-ends of puddled, Fig. 68. Shears for cutting up Puddled Bars and Slabs. finished, or other bars, and occasionally also for dressing the sides and edges of plates and shearing them to size ; although for this latter process larger and broader-faced guillotine shears (Figs. 69, 70) are more generally adopted, except for the smallest and lightest plates or sheets where the crocodile or alligator shears are still in use. 348 STEEL AND IRON. [Chap. XVI. 597. The crocodile, cropping, or alligator shears, by which names the same tool is known, has two jaws, the lower, D (Fig. 70), of which is fixed, and either forms part of the cast-iron foundation or is secured to it, whilst the other jaw, E, vibrates or oscillates on a pin passing through the jaw, and supported in bearings on the casting of the lower jaw. The upper jaw, E; has the form either of a heavy straight or bent lever, one end of which is fitted with a blade, F, of steel hardened on the edge to act as the cutter, whilst the end of the lever on the opposite side of the bearing is coupled by a connecting rod, G, either with a crank, H, or with an eccentric on a revolving shaft, or, as is more usual, espe- cially with the heavier shears, the power is derived from a small independent engine, upon the shaft of which a crank is formed and the same coupled by a connecting rod with the end of the moving jaw of the shears. In such an arrangement it is necessary to fix a fly-wheel upon the engine shaft so as to store up the energy re- quired to effect the shearing operation. The lower jaw like the upper one is fitted with a cutting edge of hardened steel, which works opposite to the blade on the fixed jaw, and these knives are readily replaced as they wear out. Fig. 70 shows a crocodile shears as applied to a powerful plate shears, where it is employed for cutting up the scrap produced from the shearing of plates, vever the employment of heavy weights or of very long levers, and it is more usual to use a smaller weight connected with a system of compound levers for multiplying the stress cor- responding to any given weight ; but Mr. Wicksteed* has described a single lever metal testing-machine well adapted for the ordinary testing purposes of the manu- facturer, where minute accuracy, such as may be necessary for the purely scientific investigator and the recording of his every step, is not required. In this machine the multiple levers are abandoned and replaced by a single lever, L, with a moving weight, M, of one ton in weight ; one end of the test-piece, t, is connected by clips, &c., to knife-edges on the beam, L, whilst the other extremity of the test-sample is likewise coupled by similar clips to a bonnet screwed on to the end of the hydraulic piston, a, of the pulling cylinder, b. The beam or lever, L, oscillates through a small arc upon knife-edges supported by the standard, B, whilst the weight, M, can be moved along the lever by a screw, actuated by the hand- wheel, ra. The machine is so arranged that the weight, M, can be moved to the extremity of the shorter end of the lever, in which position it exactly balances the long end of the lever and the other connections suspended from it, and this point marks the zero of the graduated scale, n, attached to the lever, and over which a pointer carried by the weight, M, travels as the weight moves along the lever. The distance between the point of sus- pension of the test-piece and the fulcrum or centre of oscillation of the lever is exactly 3 inches, and thus, as the weight, M, of 1 ton moves towards the end of the lever, each 3 inches of its traverse indicates an additional stress of 1 ton upon the test-piece. The clips or jaws for holding either extremity of the test-piece are steel plates, parallel and serrated on their inner faces in the manner indicated at G o (Fig. 2, p. 3), but tapered at the * Proceedings Institute of Mechanical Engineers, 1SS2. 353 354 STEEL AND IRON. [Chap. XVI. back to an incline of 1 in 6. which angle is sufficient to give the grip required to hold the piece, while it loosens its hold immediately the stress is removed. Ths ram, a, of the pulling cylinder, b, has a stroke or vertical motion of 6 inches, besides which the bonnet and shackle, /?, holding the test-piece can be screwed upon the ram, a, over a further rangp. of 6 inches, so as to accommodate test-pieces vaiying in length to this extent. 603. The stress is thus put upon the test-piece, t, by forcing down the ram, a, which also takes up the neces- sary extension or stretching of the sample, and since the pull at either end of the specimen is equal ana opposite to that at the other end, it follows that when the machine is in equilibrium the weighing apparatus i.e., the lever and movable weight, M exactly balances, and indicates the force which is being exerted through the hydraulic cylinder upon the test-piece. During the operation of testing, the weight, M, is moved so as to keep the lever, L, just floating, without allowing it to come into contact with either the upper or lower stops 011 the stan- dard, K, until the test-piece gives way and is fractured, upon which the lever falls through a small space on to a block of wood carried for this purpose by the standard, K, whereupon, by taking the reading on the scale of the distance from zero travelled by the weight, M, the exact stress upon the test-piece at any stage, or at the breaking point, is determined. 604. The pressure is put upon the hydraulic cylinder, b, and ram, #, through a horizontal hydraulic cylinder, D, at the back of the machine, which cylinder has but one-fifth of the area though five times the length of stroke of the pulling cylinder, 6, so that the cubic contents of the two cylinders are identical The cylinder, D, has a central piston or ram connected with a cross-head, E, to which is also attached a pair of parallel horizontal screws, which work through the wheels, s, as through screwed nuts. The right-hand extremity of the cylinder, D, is connected by a pipe, e, with the top of the pulling cylinder, b, while the opposite end 01 Chap. XVI.} REHEATING FURNACES. 355 left side of the cylinder, D, communicates with the lower end of the pulling cylinder and thus, supposing that both cylinders and pipes are quite filled with water or oil, it follows that by this mechanical device any pressure that is exerted upon the piston of the larger or pulling cylinder is balanced by one-fifth of that pressure upon the piston of the smaller cylinder; so that the horizontal screws with the wheels, s, and gearing, u, u, through which the power for forcing the water from the smaller to the larger cylinder is transmitted, only sustain a pressure equal to one-fifth of the load upon the test-piece, while the piston of the larger cylinder moves upwards or downwards with but one-fifth of the speed of the smaller piston. The smaller cylinder thus acts as the force pump for the larger or pulling cylinder, the power for rotating the screws and wheels, s, and the gearing, u, u, being sup- plied either by manual labour, or, as is more usual, the power is derived from some revolving shaft, and trans- mitted through a movable belt working either upon one or other of two fast pulleys or upon one loose pulley on the driving shaft of the machine, according as the machine is at work or at rest. 605. The furnaces, or reheating arrangements of the forge and mills, for heating the piles, blooms, billets, &c., of wrought-iron, or the ingots, slabs, blooms, billets, &c., of steel, to prepare them for treatment under the ham mer- er in the rolls, or by both, are (1) the open fire, as used in conjunction with the finery, and already described (p. 237); (2) the hollow fire, as employed in South Wales for reheating the piles or stamps in the manner described (p. 233) ; (3) the reverberator^/ or balling fur- nace of the forge, and the reheating or mill furnace as usually constructed for mill purposes for reheating iron or steel for the hammers or rolls ; and (4) the soaking- pits of Mr. Gjers. Of the four types just enumerated, it will only be necessary to refer further to the third and fourth types, since the first two are confined in their use to certain special and local methods adopted in the S56 STEEL AND IKON. [Chap. XVL manufacture of malleable iron, as already described, while the method of soaking has only been proposed for the treatment of steel ingots. 606. The forge reverberatory, or balling furnace, is most generally constructed and arranged to burn raw coal or other solid fuels upon its own grate-bars ; whilst the re/ieating furnaces for the mills and forging hammers, although still constructed in some works to burn only solid fuel on their own grates, are yet frequently replaced by furnaces burning gaseous fuel ; and in steel works the furnaces employed for heating steel ingots, billets, blooms, slabs, &c., are almost universally con- structed for the combustion of gaseous fuel in the manner proposed and carried out by Siemens, Bicheroux, Ponsard, Boetius, &c., &c., so that furnaces consuming solid fuel directly upon their own grates are now the exception in steel works. 607. The reheating 1 , mill, or balling furnace, adapted to the consumption of raw fuel direct upon its own grate, resembles in external appearance and form an ordinary puddling furnace, and, like it, is supported (Fig. 72) externally by cast-iron plates and buck-staves, a, a, secured from side to side and from end to end by wrought- iron tie-rods passing over the top, and secured to the plates by nuts on the screwed ends of the tie-rods. The balling furnace has a smaller area of grate-bars than the puddling furnace in proportion to the area of its bed; the chimney, 6, is also a little higher, and 8 or 9 inches wider, than would be the case for the same area of hearth in a puddling furnace, whilst the formation of the bottom of the furnace is also different : for while the mill furnace bottom is formed of sand on the top of a fire-brick lining, the puddling furnace, as previously noted, is made and fettled with furnace cinder and cer- tain ores of iron. This type of furnace is employed more particularly in iron works for raising to a welding heat the piles of puddled bar or the higher grades of malleable iron, previous to the rewelding of the same under the Chap. XVI.J REHEATING OR BALLING FURNACE. 357 hammer, or in the mill rolls ; but they are now only very rarely employed for reheating steel ingots or blooms in preparation for the rolling mills. 608. Balling furnaces differ in size, form, and number Fig. 72. Vertical Section of Reheating or Balling .b'urnace. of their doors according to the nature of the charges they are intended to receive. As constructed for reheating the piles, &c., for rolling into merchant iron, and as built for the South Wales forges, the bottom of the hearth is "Fig. 73. Plan of Bed of Reheating or Balling Furnace. made of cast-iron plates fixed about 14 inches below the working door, and upon this is laid a course of fire-bricks upon which the working bottom is made by well ramming in sand in a moist state. The bottom or bed, c, slopes uniformly from the working door, d (Fig. 73), to the back 358 STEEL AND IRON. [Cliap. XVJ, of the hearth, as also from the fire-bridge, g, to the stack, b. The fire-bridge is built about 9 inches in width, and reaches to within about 14 inches of the roof, and the chimney or flue-end of the hearth is rounded off, and slopes, as shown (Fig. 72), towards the bottom of the stack. The cinder from the hearth thus flows along this flue to the tap-hole, 7i, at the base of the stack, and the tap-hole is prevented from closing up by the cooling and solidifica- tion of the slag or cinder within it by keeping a small fire constantly burning in front of it. The stoking-hole, k, is closed or stopped after firing by introducing lumps of coal into the opening, and then throwing a shovelful of coal slack over them just as is done with the puddling furnace, whilst the draught is maintained and regulated to the requirements of the furnace by a stack, upon the top of which is a damper suspended from one end of a lever, from the other end of which hangs a rod reaching to the floor level. The height, as given above, of the roof from the bed of the furnace is adapted to the production of merchant iron of ordinary sizes, but for the heating of large slabs or forgings the roof may be raised, and the size of the doors increased considerably. In some fur- naces, also, the cast-iron bed-plates are not introduced, in which case the sand bottom is prepared by ramming sand into a bottom of rubble masonry. 609. The workman, or " bailer," introduces the charges of piles into the balling furnace with the assistance of a heavy bar with a flattened end, called a "peeler." The flattened end of the peeler rests during the time of charging, either upon the sill of the furnace door, where the smaller piles are placed upon it, or with the heavier packets the peeler with the pile upon it is carried upon a bogie, which delivers it at the height of the furnace door. In either case, the peeler with the pile upon it is pushed into the furnace, and the peeler is then withdrawn in such a manner as to leave the pile standing across the furnace parallel with the fire-bridge, when the end farthest from the charging door following the incline of the bed of the Chap. XVI.] REHEATING OF PILES. 359 furnace thus stands about 6 inches lower than the end nearest the door. For the production of merchant bars, four such piles are inserted into the furnace at one charging or heat, care being taken not to disturb the bars making up the pile during the charging of the same. The charge thus introduced into the furnace is called a " hea.t," but the number of piles introduced for a heat obviously will differ with the size of the same, so that instead of four piles, as above, making up the heat, some sixteen or eighteen smaller piles are frequently introduced as a heat for the same furnace. When the charging is completed, the door is lowered into posi- tion, and a shovelful of coal is thrown around it to prevent the admission of air. The temperature of the furnace is then raised by cleaning the grate-bars, adding more fuel through the stoking door, re-stopping the latter with coal, and then raising the chimney damper. In this manner the larger piles first mentioned will attain to a welding heat in about one hour, or with the smaller piles thirty minutes will suffice to raise them to a welding heat, at which temperature they are withdrawn from the furnace by seizing each one separately with a pair of tongs and drawing it forward on to a bogie in front of the door, which is run rapidly to the rolls, through which the dripping pile is at once passed. The whole of the piles having been thus withdrawn, the furnace bottom is usually slightly repaired by the introduction of a little sand, after which all is ready for the intro- duction of another heat. The withdrawal of the charge and repair of the bottom usually occupy from fifteen to twenty minutes. 610. During the reheating of piles or of ingots they are moved about a little to promote more rapid and uniform heating over the whole surface of the mass, otherwise the lower side, being in contact with the bottom of the furnace, is not exposed like the upper surface to the action of the flame within the furnace, and would hence remain comparatively cold for a much longer period than the top 360 STEKL AND IRON. [Chap. XVL of the pile or ingot, &c. ; while, as the mass approaches a welding heat, oxidation and scaling of the iron pro- ceed somewhat rapidly, and such scale falls on to the bottom of the furnace, where it combines with the silica or sand of the bottom with the production of a readily fusible slag or cinder, which flows away freely to the bottom of the stack, from whence it escapes by the tap- hole already mentioned. 611. The flue-cinder, or mill furnace slag, thus produced daring the balling or reheating process is essen- tially a bibasic ferrous silicate of iron, containing from 50 to 60 per cent, of ferrous oxide, representing from 40 to' 45 per cent, of metallic iron, the other constituents of the cinder being about 30 per cent, of silica, with small percentages of ferric oxide, manganous oxide, alu- mina, lime, magnesia, sulphur, and phosphoric anhydride. 612. The consumption of coal in the production of No. 2 merchant iron from the ore, embracing that con- sumed in the calcination and smelting of the ore, the puddling of the pig-iron, and the reheating for rolling into No. 2 quality of iron, is, roughly, about four times the weight of the bars produced ; and there is an additional consumption of from 9 to 10 cwts. of coal per ton for each additional piling and reheating necessary for the produc- tion of each higher grade of merchantable iron ; so that to make treble-best iron nearly 6 tons of coal are consumed per ton of bars, whilst steel bars can be produced with the consumption of about 3 tons of coal per ton. 613. The yield of merchantable iron per ton of pig- iron treated differs with the locality, the quality of the pig, the skill of the workman, and the quality of iron pro- duced, or the number of separate pilings and reheatings to which it has been submitted ; but the average loss in the Staffordshire district is about 25 per cent., and in South Wales it is somewhat greater. Thus the loss in the Dudley district of Staffordshire between the pig-iron treated and the puddled bars produced is about 10 per cent, or, more accurately, 24 cwts. of pig-iron usually Chap. XVI.] GAS REHEATING FURNACES. 3G1 yield 22 cwts. of puddled bars, while 22| cwts. of the latter are required to produce a ton of merchant bar. 614. The loss in rolling steel is not nearly so great as in iron, since the piling and welding processes are unne- cessary, while lower temperatures with a proportionately smaller oxidation and loss are adopted throughout the manipulation of steel ; thus, in rolling rails from steel ingots with the adoption of the soaking-pit arrangement of Mr. Gjers for the heating of the ingots, and one reheating of the 8-inch blooms produced by the cogging of the same, the loss, including crop-ends, at the West Cumberland Steel Works,* over a week's working was only 12 per cent, of the weight of ingots charged. 615. Gas furnaces have been extensively introduced, instead of the reheating or balling furnaces heated in the manner last described, by the combustion of solid fuel upon the grate-bars of the furnace itself. Gas furnaces for reheating purposes are of the reverbera tory type, either upon the regenerative principle of Sir W. Siemens, or, like those of Bicheroux, Boetius, &c., without regenerators ; but they are all heated by the combustion of gaseous fuel produced either in separate producers or gas generators, such as those of Siemens, Wilson, and others, and from which the gases produced in the manner described (p. 369), are conveyed through culverts and gas-mains to the furnace hearth, to which they are admitted, along with the heated air necessary for their combustion, through suitable valves and ports as required for the production of the necessary furnace heat ; or, instead of the producers being separated from the furnace itself, they are also made part of it, and thus replace the grate-bars of the ordinary coal furnace as in the Casson-Dormoy, the Bicheroux, the Ponsard, and the Boetius reheating furnaces. In the last-mentioned the gases ascend from the producer direct to the fire-bridge of the furnace, where they meet with the heated air for their combustion. Reheating furnaces burning gaseous * Mr. Snelus : Engineer, March 16, 1883. 362 STEEL AND IRON. [Chap. XVI, fuel vary in construction with differences in the materials employed for the generation of the gas and with the mode of its combustion ; thus the Bicheroux and Boetius furnaces are without regenerators, but the air required for combustion is previously heated in the manner de- scribed (p. 280), while the waste heat of the flame as it leaves the bed of the furnace either escapes to the atmo- sphere or is used to raise steam by passing it beneath the steam boilers. 616. The production of gases in separate chambers or generators, with the subsequent combustion of the same by their union with the oxygen of the atmospheric air on the hearth of the furnace, was proposed and fre- quently tried, but without practical success, early in the present century. The subject occupied the attention of Bischoff in 1839, and from that time its further development has been in progress ; but the greatest practical development and success was that obtained by Sir William Siemens with his separate gas-producer and regenerative furnace (p. 273), as now so extensively em- ployed for reheating purposes in the forge and mill, and for the steel-melting furnaces, as well as for many other metallurgical operations where high temperatures, with great cleanliness and control over the flame, are neces- sary. Its adoption marks one of the greatest improve- ments of recent years in connection with the economy and use of fuel for furnace purposes. 617. The waste gases of the blast furnace, although providing a gaseous fuel extensively applied to the raising of steam, heating of the hot-blast, roasting of ores, burning of lime, bricks, &c., is yet too irregular in amount, and varies so much in quality according to the working of the blast furnace, that it has not been found applicable for combustion in the puddling or reheating furnace. 618. In the gas furnace the temperature is more under control, and there is a greater purity of flame upon the hearth than is possible in furnaces consuming raw coal upon the ordinary grate - bars. Further, an Chap. XVI. SIEMENS GAS-PRODUCER. 363 oxidising, neutral, or reducing atmosphere can be main- tained in the heating chamber of the furnace according as more or less atmospheric air is admitted for the com- bustion of the producer gases, and the loss of metal from oxidation is thereby diminished ; this economy in the reheating of 1^-inch iron billets for the production of iron wire amounting to about 5 per cent. ; for while in the gas reheating furnace the loss from oxidation does not exceed 2J per cent, of the metal charged, with the ordinary coal furnace the loss is nearly 7 per cent. With steel, however, the direct economy is less, since the temperatures employed are lower and the oxidation and waste are therefore less active, whether coal or gas furnaces be employed. The use of the gas furnace is also attended with a total absence of smoke. 619. The use of the gas-producer instead of the ordinary grate permits of the consumption of inferior classes of fuel, such as coal slack, anthracite culm, and every variety of bituminous or semi-bituminous coals, lignites, peat, air-dried wood, &c. Beyond the use of inferior fuel, the adoption of the gas-producer is attended also with a saving in the quantity of fuel consumed, be- sides affording a more uniform heat ; and by preventing the contact of the fuel with the highly heated lining of the furnace, it obviates the destructive action of the same upon the furnace, which accordingly requires less repairs and makes more prolonged campaigns. 620. The Siemens gas-producer is a fire-brick chamber, A (Figs. 74, 75), rectangular in plan, and usually built below the level of the ground. The front side, />, of the chamber is inclined as shown from the top to the bottom, at an angle of from 45 to 60, a usual angle being about 50, and this slope is formed of cast-iron plates lined with fire-brick, or is built in a series of arches as shown in Fig. 74, stepped back so as to give the required slope. At the bottom of the chamber are the wrought-iron fire-bars, s, placed at a slight inclination from the front to the back of the 364 Fig. 74. Vertical Section through.Two'of Siemens'Gas-producorg. fig. 75. Plan at floor level of one block of Siemens Gas-producers. Chap. X^L] SIEMENS GAS-PRODUCER. 365 chamber, and resting upon bearers, t, t, of cast-iron or of old rails built into the masonry. In the centre of each four chambers or block of producers is built the up-take, d, from 10 to 12 feet in height, which is divided up to the height of the damper, m, (or about 3 feet from the floor level), into four distinct flues, a, a', a", a"' (Fig. 75), which open above the damper, m, into one common up-take ; so that by inserting or withdraw- ing the iron damper plate, at m, any one of the four gas- producing chambers can be shut off or opened to the up-take without interfering with the action of the other producers of the block, when the cleaning out or repairs of any of the chambers becomes necessary. From the top of the up-take the iron cross-tube, e, leads to the main gas tube; or, in some works, instead of the up- take, d, and the cross-tube, e, a curved wrought-iron tube has its foot at the bottom of the up-take and curves over from thence to the main gas tube. The arched roof of the producer has several apertures built into it for pottering the fire, observing the working, and for feed- ing in the coal, &c., respectively; thus the plug or sight- holes, l y closed by a cap or a cast-iron ball that can be readily rolled off the aperture and replaced as required, supply a ready means of inspecting the producer as to the condition of the gas and the fire, as also for the introduction of the iron bars required for pottering down and breaking up the fire as it becomes necessary during the working. Over the aperture, A, is placed a sheet-iron or cast-iron hopper, with a slide or damper in the bottom between the cavity of the hopper and the producer, and this hopper is kept constantly filled with fuel, which is dropped down on to the sloping side of the producer by drawing out the slide when and as required; the charge of coal in the hopper thus serving to keep the charging aperture closed and comparatively gas-tight, whilst at the same time the coal becomes warmed and dry before its introduction into the producer ; and in this manner a thick layer of coal is always kept on the 366 STEEL AND IRON. [Chap. XVI fire-bars without opening the chamber to the atmosphere during the time of charging. Those producers are usually built in rows, with an arched passage or cave, z, along each side, through which ready access is gained to the ash-pit for the clinkering, cleaning out, and removal of the ashes ; for which purpose a few of the fire-bars are withdrawn and the collected clinker broken down by the introduction of suitable bars, whilst from a flexible pipe placed opposite each producer the workman is able to cool down the clinker and ashes by delivering upon them a jet of water. A little water is also introduced into the ash-pit from time to time for evaporation by the radiated heat of the producer, and the steam there- from, ascending over the mass of heated fuel in the body of the producer, is decomposed with the oxida- tion of the incandescent carbon and the liberation of hydrogen, thus increasing the volume of the combustible gases carbonic oxide and hydrogen passing from the producer. With a like object variously devised steam and air jets, j, have been proposed, and some form of these is now generally applied to the producers, with the view to a further economy of fuel by more perfectly con- suming the coke resulting from the distillation of the coal in the upper zones of the producer, and thereby in- creasing, as above, the volume of carbonic oxide and of hydrogen escaping to the furnaces for combustion. Such blast-jets are introduced eithej below the fire-bars into the ash-pit, which is then closed by folding doors, w, or the blast is introduced by suitable nozzles into the body of the fuel in the producer, either from the sides, by the front, or from below. 621. A blast of atmospheric air suitably proportioned to the capacity of the producer increases alike tho volume of combustible gases from the producer, the pressure of gas in the mains, and likewise their initial temperature ; it also effects a more complete and larger consumption of fuel and thereby a larger volume of gas is produced by each gas-producer, thus necessitating the use of a smaller Chap. XVI.] WILSON GAS-PRODUCER 367 number for the generation of the volume of gas required per furnace ; and by the application of a blast also the inferior classes of fuel are used to greater advantage. The pressure of gas within the gas mains and brick culverts leading to the furnaces is sufficient to prevent the leakage of air from the exterior to the interior of the mains through any small crevices, cracks, or other imper- fections in the construction of the tubes and culverts, and the outward pressure is further increased by the use of steam or other blast at the producers. The admission of air to the gas mains, besides diluting the gas, would obviously be attended with the production of a more or less explosive mixture within the mains. 622. The producer, as thus described, has essentially the form originally introduced by Sir W. Siemens, modi- fied only in minor details as suggested by long experience, and it is still the form most generally adopted, although Siemens, Wilson, Casson, and others have introduced circular and other producers, each of greater capacity than those above described, and fitted with variously devised atmospheric or steam blasts, but these have not to any very considerable extent superseded the origi- nal form. 623. The Bicheroux, Gas- son, and Ponsard gas pro- ducers are of the same type and are palpable copies of the Siemens producer ; but the circular producer of Messrs. Brook and Wilson presents features substantially differ- ing from the original Siemens construction, inasmuch as it is a closed circular chamber (Figs. 76, 77) of brickwork within a wrought-iron casing, and into which chamber Fig. 76. Vertical Section on line A, B, Fig. 77, of the Brook and Wilson Gas Producer. 368 STEEL AND IRON. [Chap. XVI the fuel is discharged at the top from the hopper a. This producer has a solid hearth without grate-bars, the blast of air for combustion being supplied into a T-shaped distributor in the centre of the hearth by a blowing arrangement, consisting of a steam jet, b (Fig. 76). directed into a conical trumpet- mouthed nozzle, c, in which manner both steam and air are propelled into the centre of the producer, in the proportion of about 5 parts of the former to 100 of the latter. The gases generated in the producer make their exit by the ports d, d, to the downtake e, com- municating with the gas - culvert leading to the furnaces where the gases are to be con- sumed. The valve in the downtake, worked by the chain and balance-weight, f, serves to shut off any producer for repairs, &c., as may be required ; g, g, are doors for clearing away clinker, &c., from the health ; and h, h, are sight-holes for observing the working of the producer, and for the introduction of bars, &c., for pottering down the fuel to the hearth. 624. The action of the Wilson producer is the same as that of the Siemens producer already described. The oxygen of the atmospheric blast entering amongst the red-hot fuel at the bottom of the producer serves to support and maintain combustion, with the oxidation of the carbon to the state of carbonic anhydride (C0 2 ), Fig. 77. Vertical Section of the Brook and Wilson Gas Producer. Chap. XVI.] GASES FROM SIEMENS PRODUCER. 369 which gas, ascending through the superincumbent mass of incandescent carbon (fuel), is reduced by the combination of each volume of carbonic anhydride with an additional proportion of carbon, yielding thereby two volumes of combustible carbonic oxide (CO), which forms the most important and useful constituent of the escaping gases. The steam entering the producer also, if not present in excess, is wholly decomposed in passing over the incan- descent fuel, with the production thereby of hydrogen and carbonic oxide, which likewise go to swell the volume of combustible gases passing from the producer ; whilst the upper part of the producer simply acts as a retort for the distillation, by the sensible heat of the burning fuel below, of the volatile hydrocarbons from the fuel intro- duced through the hopper above, in the manner already mentioned, before the fuel descends to the more strongly heated zones below. 625. The gases produced in the Siemens, or other producer, differ considerably according to the nature of the fuel and the manner in which the producer is managed. Although, as previously stated, all classes of coal, coal- slack, anthracite culm, coke, lignite, peat, sawdust, &c., may be used alone or bettei in conjunction with coal, yet the best fuel for the gas producer is a bituminous or semi-bituminous coal, not too strongly caking. If the producer be worked with an open ash-pit, and without any atmospheric or steam blast, then only a limited supply of air reaches the fuel through the grate-bars, and the oxygen accordingly combines with and maintains the combustion of the lower layers of fuel upon the bars at the bottom of the producer; whilst the heat of combustion drives off or distils over the volatile constituents (con- sisting of hydrocarbons with other gases and vapours) from the superincumbent mass of coal. The carbonic anhydride produced at the grate-bars by the combustion of the carbon of the fuel and atmospheric oxygen, ascends through the producer over the superincumbent incan- descent coke and carbonaceous matters, and is thus re- Y 370 STEEL AND IRON. [Chap. XVI. duced to carbonic oxide, each volume of carbonic anhy- dride yielding two volumes of carbonic oxide thus C0 2 + 0=2 CO which escapes from the producer to the uptake and onwards to the gas main. Thus the gases passing from the producer contain in addition to the com- bustible hydrocarbons and vapours previously mentioned a large proportion of carbonic oxide, dilated with a certain proportion of nitrogen from the atmosphere, and a smaller proportion of unreduced carbonic anhydride. If artificial blast be also employed then a larger propor- tion of carbonic oxide occurs in the gases, owing to the oxidation of a portion of the fixed carbon of the fuel by the oxygen of the blast; whilst the steam evaporated from the water in the ash-pit, as also the small quantity used in the production of the blast, ascends through the incan- descent fuel, and suffers decomposition, giving up its oxygen to the carbon of the fuel and producing thereby carbonic anhydride, which is immediately again reduced to the state of carbonic oxide as above, whilst the com- bustible hydrogen from the water is also added to the gases from the producer : thus OH 2 + C = CO + 2 H. The addition of carbonic oxide and hydrogen from these sources obviously increases the calorific value of the gases. ANALYSES OF GASES FROM THE PRODUCER. Using Durham coal. Using fine coal slack. Using a mixture of three-fourths caking with one-fourth non- caking coal. Carbonic oxide . Marsh gas (CH^ . Hydrogen Nitrogen Carbonic anhydride 26-89 1-45 11-55 56-11 4-00 23-41 2-22 13-82 55-86 4-69 24-2 2-2 8-2 61-2 4-2 100-00 100-00 100-00 Per-centage of com- > bustible ga.?es f 39-89 39-45 34-6 Chap. XVI.] SIEMENS REGENERATIVE FURNACE. 371 626. From the previous analyses it will be noted that the combustible or heat-producing gases, viz., carbonic oxide, carburetted hydrogen (CH 4 ), and hydrogen, are in the aggregate practically the same in the three examples, constituting in the first two instances nearly 40 per cent, of the total volume of the gases ; whilst the nitrogen and carbonic anhydride, which constitute 60 per cent, of the volume of the producer gases, act only as diluents, and do not add (except by their sensible heat) to the heat of the furnace. The 4 or 4-5 per cent, of carbonic anhydride indicated in these analyses represents the maximum pro- portion of this gas at which the producer can be con- sidered to be working well, for any appreciable excess over this figure indicates that from some cause it is working badly. 627. The Siemens regenerative gas furnace consists of three parts, viz., the producers or apparatus for the generation of the crude gas ; the regenerators or chambers filled with a chequer work of fire-bricks, which alter- nately absorb and store up the waste heat of the flame and gases as they escape from the furnace hearth, and then subsequently give up this heat to the gases from the producers, and to the air for supporting their com- bustion, as each of them passes through the separate regenerators before meeting for combustion upon the bed or hearth of the furnace ; and lastly, there is the furnace structure proper. 628. The Siemens regenerative reheating, or mill furnace is supported externally by iron plates, supported by stancheons, buck-staves, and tie-bolts in the usual manner and as shown in Figs. 78 and 79. The bed or hearth of the furnace is supported upon cast-iron plates kept cool by the free circulation of air beneath them, admitted through suitable holes, p p, left in the external plating, and the bed slopes slightly from front to back, where a tap-hole is made for tapping out the cinder or slag at required', intervals. Upon the cast-iron bed plates there is first laid a course of fire-bricks 372 STEEL AND IRON. [Chap. XTI. (Fig. 78), and upon this is introduced a layer of sand, B, of from 10 to 12 inches in thickness, which forms the working bottom of the furnace. The two ends of the furnace are quite symmetrically built, and are each pro- vided usually with two ports or openings for the admis- sion of the heated gases, and with three others for the admission of the heated air required for their combustion. The gases and air, after passing through one pair of Fig. 78. Sectional Elevation of Siemens Reheating or Mill Furnace. heated regenerators, G, A, are admitted to the hearth at one end through the ports just mentioned, and after combustion the waste gases pass from the hearth through the ports at the opposite end, and from thence through the other pair of regenerators to the chimney. The course of the gases is reversed from one end to the other of the furnace at frequent intervals, in the manner to be imme- diately described. The size of hearth, as also the size and number of doors with which the furnace is fitted, depend upon the size of work to be heated. The roof of the furnace is built of the best fire-brick, is arched from side to side as shown, and slopes from the two ends Chaj>. XVI.] SIEMENS REHEATING FURNACE. 373 towards the centre of the hearth, whilst its height above the bed is determined by the class of work to be heated in the furnace. 629. Transversely beneath the furnace proper are built the -four arched chambers, A, A 1? G, GI (Fig. 78) each filled with a chequer work of fire-bricks, and constituting the regenerators, of which the two smaller, G, GI, are for heating Fig. 79. Front Elevation of Siemens Mill or Reheating Furnace, with Section through the Cave and Reversing Valve. the producer gases, whilst the larger ones, A, AJ, perform the like function with respect to the air for their combustion. The chequer work of the regenerators is arranged in the manner shown, so as to allow of a comparatively free passage of air or gas through them, and at the same time to expose the largest possible surface for the absorption of the heat from the waste gases as they leave the furnace for the stack, or for imparting heat to the air and gases previous to their combustion upon the hearth. The admission of the producer gases and of atmospheric 374 STEEL AND IRON. [Chap. XVI. air to the furnace is controlled by separate valves placed in the cave, v, in front of the regenerators, and below the floor level, which valves are worked by notched levers, m, and hand screws n, placed on pillars in front of the furnace, and connected by levers with the valves. The mushroom valve, A, (Fig. 87, p. 447) for the admission of air, is about 25 or 30 per cent, larger in area than the gas valve, d, Fig. 79. The gases from the gas culvert enter the gas box 6, and pass by the mushroom regulating valve, d, through the valve, H, the tongue of which, h y can be turned over or reversed, as shown dotted in the figure, so as to direct the gases towards either of the gas regenerators, G or G ]5 as required. From the reversing valve H, the gases enter the culvert or -flue, I, and so pass to the bottom of the regenerator chamber, G 15 (Fig. 78), through which they ascend from the cooler lower portion towards the upper or hotter layers of brickwork nearer to the furnace. The air also enters through a corresponding regulating mushroom valve and a reversing valve a, placed behind the gas valve, as shown in the transverse section of the steel-melting furnace (Fig. 87, p. 447), the arrange- ment of the valves and for the reversal of the current being identical in both the reheating and the steel-melting furnaces ; and the air is thus conveyed to the bottom of the air regenerator, A I? which, as already mentioned, is the larger chamber in each pair. The air and gases thus ascend through their respective regenerators to the furnace hearth, which they enter : the first-named through three openings, a, a l} while the gas enters by the two ports, 9-. 9\> by which means the air is admitted above and behind the gas as shown in Fig. 78. If the furnace be already heated, combustion of the gases at once ensues upon the meeting of the same upon the furnace hearth, producing thereby a large flame and an intense heat, pro- portionate to the amount of gas admitted through the regulating valve already named ; whilst, as before noted, a reducing, neutral or oxidising flame can be maintained by varying the proportion of air to gas admitted to the Chap. XVI.] SIEMENS REHEATING FURNACE. 375 furnace. The air and gases are thus admitted at one end of the furnace, after having been heated in their course from the regulating valves to the furnace by passing over the heated chequer work of the pair of regenerators at the same end of the furnace ; the flame and waste gases escape at the same time by the ports at the opposite end of the hearth and are drawn down by the chimney draught through the chequer work of the other pair of regenerators, A, G, reheating the chequer work therein, and passing on until they reach the flue, K, by which the gases pass, as shown by the arrows, to the chimney. 630. The regenerators are thus always worked in pairs consisting of one large and one smaller chamber, of which the air passes through the former and the gases through the latter on their way to the furnace. 631. The waste gases and products of combustion are thus always drawn downwards by the chimney draught from the top to the bottom of the regenerators, or in the reverse direction to that traversed by the gases and air on their way to the furnace hearth ; and the waste gases instead of escaping to the chimney at the temperature of the furnace, give up in their passage over the chequer work of the regenerators a large proportion of their sensible heat, and finally pass away to the chimney at a temperature of only about 150 C. (302 Fahr.). In this manner the upper tiers of bricks in the regenerators may be heated to a temperature only slightly lower than that of the furnace itself, whilst the courses of brickwork lower down or farther from the furnace become successively less and less heated. While one pair of regenerators is being thus heated by the gases escaping from the furnace towards the stack, the heat stored up in the brickwork of the other pair is being absorbed by the producer gases and the air passing through them towards the furnace, until the temperature of -one pair of regenerators has been sen- sibly or sufficiently reduced, and the temperature of the other pair at the same time proportionately raised, then the direction of the gaseous current is reversed by moving 376 STEEL AND IRON. [Chap. XVI. the tongue, h (Fig. 79), of the reversing valve, H, into the position shown by the dotted lines, when the flame and waste gases are then drawn away at the opposite end of the furnace through the other pair of regene- rators, which are heated in the same manner as before, whilst at the same time the gases and air are drawn upwards towards the furnace through the last heated pair of regenerators. The gases and air thus enter the regenerators at. their lower or cooler end, and ascend towards the more strongly heated parts, becoming in their passage gradually heated by contact with the heated brickwork, until, when entering the furnace, the producer gases and the air have a temperature almost equal to that of the waste gases escaping from the opposite end of the furnace. The gases and air thus raised to an elevated temperature only mix upon entering the furnace hearth, when their combustion fills the same with an in- tensely heated flame; and were it not for the introduction at intervals of cold or comparatively cold materials into vhe furnace, together with a proper adjustment of the amount of gas admitted, it is obvious that, by reversing the course of the gas at regular intervals, a gradually increasing temperature would be obtained, since the heat produced by the combustion of the gases is added to that absorbed by the gases and air from the regene- rators in their passage through them, so that after each reversal of the current the temperature of the regene- rators and therefore of the flame would be higher than it was after the previous reversal ; and the temperature ultimately attainable in the regenerative furnace is only limited by the capacity of the refractory materials of which the furnace is constructed to withstand the heat. 632. Most of the heat generated by combustion is retained in the furnace and regenerators, since the tempe- rature of the gases escaping from the chimney under careful working of the furnace rarely much exceeds about 150 C. (302 Fahr.), whatever may be the temperature of the furnace ; whilst, in the ordinary reheating furnace burn- Chac. XVI.] SIEMENS REHEATING FURNACE. 377 ing coal in its own grate-bars and without regenerators, the amount of heat carried away to the stack by the waste gases exceeds that which is utilised in doing useful work ; hence the regenerators, by utilising the waste heat, effect a considerable economy in fuel over the ordinary furnace without regenerators, and this saving is greater in proportion as the working temperature is increased. 633. From 6 to 8 square feet of regenerator surface is usually calculated as being necessary to take up or absorb what is practicable of the heat generated by the combustion of 1 Ib. of coal. 634. With a cold furnace, or on first lighting up a new furnace, it is necessary to dry it carefully by burning a large fire upon the hearth for some days before turning the gas into it ; and after thus thoroughly drying a large tire of vvood and shavings requires to be made upon the hearth, so as to fill it with flame and so ignite the gases immediately they enter the furnace before any explosive mixture of gas and air can collect within the furnace. Combustion having been thus commenced, the tempera- ture of the furnace is gradually raised as the gaseous current is from time to time reversed ; since after each re- versal the gases enter with a higher initial temperature, owing to the increased temperature of the regenerators, produced as already described ; but when the furnace has attained a sufficiently elevated temperature, its further working is then regulated and controlled by limiting or increasing the supply of gas and air thereto, by means of the regulating valves already mentioned, and also by the chimney damper ; and the nature of the flame is also controlled by the relative proportions of air and gas respectively admitted to the furnace. The regu- lating and reversing valves are moved by levers, m, and hand screws, n, (Fig. 79) or by notched levers worked by the workman from the front of the furnace. The current requires reversing at intervals of from thirty to fifty minutes, according to the size of the furnace and the temperature to be maintained. 378 STEEL AND IRON. fChap. XVI. 635. The Bcetius gas reheating furnace is without regenerators, but the air for combustion is delivered through slots in the fire-bridge, and also from a broad flat opening, situated above and behind the aperture for the admission of gas from the producer to the hearth of the furnace. The air for combustion is heated before its admission by being circulated through a series of flues in the casing walls and roof of the producer, of which the inner walls are purposely built only 4^ inches in thickness, so as to transmit the heat of the pro- ducer freely to the flues through which the air for main- taining the combustion of the gases is drawn. The producer is a deep rectangular chamber with one sloping side and an inclined grate at the bottom, resembling the Siemens producer already described, but it is built as a portion of the furnace itself and thus replaces the grate- bars of the ordinary coal furnace. The producer is closed by an arched roof, in which there is an opening for the introduction of the fuel, and the producer gases pass to the furnace hearth through a long narrow slot, situated above the fire-bridge. The producer gases and heated air thus meet at the fire-bridge and produce a large volume of flame, which plays over the hearth and fills the body of the furnace, whilst the heated gases, the pro- ducts of combustion, &c., escape by the flue at the other end of the hearth, and are either used in the raising of steam, &c., or are allowed to escape directly to the chimney, according to the arrangement of the furnace. This furnace is said to save from 15 to 20 per cent, of the fuel required for the ordinary coal-burning reheating furnace. 636. The Bicheroux reheating furnace, like that last described, consists of a furnace, a, and gas-producer, b, in one structure, (Figs. 80, 81,) which is unprovided with any regenerative apparatus, but heats only the air required for the combustion of the producer gases. The air is heated by circulating it through a broad flat flue of from 25 to 30 feet in length, and of almost the full width of the Chap. XVI.] THE BICHEROUX REHEATING FURXACE. 379 furnace hearth beneath which it is built, whereby a large heating surface is presented to the air as it passes to the fire-bridge to meet the producer gases ; by this means a high initial temperature of gases and air, though in this respect inferior to that attainable with the Siemens Fig. 80. Sectional Elevation of the Bicheroux Reheating Furnace. regenerators, is obtained before combustion takes place, and thus a high temperature is readily produced on the furnace hearth. This furnace is somewhat largely em ployed in steel works for the reheating of steel ingots for the rolling mills, in which process it consumes about Fig. 81. Plan of the Bicheroux Reheating Furnace, on the line A B c D. (Fig. 80.) 2J cwts. of small coal per ton of ingots heated, and witli Casson's modification in the gas-producer, constituting the C asson-Bicheroux furnace, it is finding its way into some of the principal iron works of Staffordshire and elsewhere. Fig. 81 shows the method of heating the air by circulat. 380 STEEL AND IRON. [Chap. XVL ing it through the hollow sides, d, d, of the gas producer, before it enters the furnace from the long slot, e, e, behind the gasports, f. 637. The Casson-Bicheroux furnace has also been adopted as a puddling furnace, and is reported to afford larger yields and a superior quality of iron with less labour and fuel than with the ordinary furnace ; but there is an alleged extra amount of labour required in cleaning the producer bars. 638. The Ponsard furnace and recuperator, employed for reheating purposes in the rolling mill, has a gas pro- ducer placed below the floor level, not materially differing in design from the ordinary Siemens gas producer, except that it forms part of the furnace structure, so that the gases pass for combustion direct from the producer cham- ber to the fire-bridge of the furnace. The supply of gas from the producer to the furnace is controlled only by a damper inserted in the throat of the producer, between it and the bridge of the furnace ; while the air for com- bustion is conveyed from the recuperator or regenerator to the fire-bridge by a flue passing behind and parallel with the gas-flue, and the air thus enters above the gas ports. At the opposite end of the furnace the flame and products of combustion from the hearth are drawn away, and are conveyed by a flue running beneath the bed to a single chamber or "recuperator," as it is called, filled with a chequer work formed partially of perforated and partially of solid bricks, arranged so as to form a series of vertical passages or flues from the top to the bottom of the recuperator, but also constructed so that the adjacent vertical passages or flues do not communicate in any manner with each other, while the alternate vertical passages do so communicate with each other through hori- zontal perforatings or holes in the bricks themselves. Thus the circulation of the air proceeds in a transverse as well as in a vertical direction, as it ascends from the bottom to the top of the recuperator and thence to the bridge of the furnace. This form of recuperator thus Chap XVI.] PONSARD FURNACE AND RECUPERATOR. 381 necessitates the use of two kinds of fire-bricks in its construction, viz., the hollow or perforated bricks above- mentioned, which are laid transversely across the chamber, and by which the several air flues communicate the one with the other ; while the other bricks, forming the flues through which the waste gases from the furnace descend 011 their way to the stack, are oblong bricks, square in cross section, and laid end to end in the direction of the length of the furnace. In this manner the action of the recuperator is made continuous, there being no reversal of the current such as is required with the Siemens furnace, but t-ie flame, the products of com- bustion, and the waste gases pass continuously from the same end of the furnace through one set of vertical flues or passages from the top to the bottom of the recuperator, while the cold air for supporting combustion is admitted by a valve at the bottom of the recuperator chamber, and ascends through the other set of vertical flues, the brick sides of which are heated by the waste gases cir- culating around them in the adjacent flues. The air then enters the furnace, after traversing the recuperator, at a temperature of from 482 C. to 538 0. (900 Fahr. to 1,000 Fahr.). 639. The leakage through the several joints in the brickwork of the recuperator is largely prevented by forming shallow grooves along the faces of the bricks where they come into contact with each other, which grooves are filled with mortar as the bricks are laid, and, since the mortar expands under the heat of the recupe- rator, the several flues are kept fairly tight. Since the pressure of air ascending through the air passages of the recuperator is always slightly in excess of that of the waste gases descending in the other passages, it hence follows that any leakage from bad joints, cracks, &c., would be mostly from the air to the waste-gas passages, and the only effect would be to more completely consume the gases from the furnace, with a proportionate addition thereby of heat to the recuperator. 382 STEEL AND IRON. [Chap. XVI. 640. In Austria and Hungary, a gas furnace using wood for its fuel has been arranged with three hearths between the gas generator or producer and the stack, thus combining a reheating and puddling furnace in one struc- ture. The first hearth close to the producer constitutes a reheating hearth, and is heated only by the sensible heat of the gases from the producer, whilst on the second or puddling hearth the maximum heat is obtained, the producer gases being there burnt by the admission over the fire-bridge of the air necessary for their com- bustion ; and the third hearth, situated nearest to the stack, is employed in heating the charge of pig-iron before its introduction on to the middle or puddling hearth, the requisite heat being afforded by the waste- gases from the puddling hearth on their way to the stack. 641. By the use of the so-called " soaking pits " Mr. Gjers* has shown that it is easy to roll a bloom, rail, or other finished steel bar from a suitable steel ingot without the expenditure of any fuel for reheating, the initial heat of the ingot, together with the store of latent heat in the fluid steel which is given out during its solidification, being more than enough for the require- ments of the hammering or rolling processes. 642. Steel ingots, when newly stripped that is, with- drawn from the moulds in which they have been cast are far too hot in the interior for immediate rolling, and if allowed to stand in the open until the interior has cooled down sufficiently, it is then found that the exterior has become much too cold to roll satisfactorily. Hence the soaking arrangement is intended to provide for the uniform distribution throughout the ingot of the excess of heat stored up by the fluid metal in the interior, whereby a uniform and sufficiently high tempera- ture is obtained to enable the ingot to be easily rolled in the blooming or cogging mill and afterwards passed through the finishing rolls. 643. The soaking pits consist of a number of vertical * Iron and Steel Institute, 1882. Chap. XTI.] SOAKING PITS. 385 pits built together in a mass of brickwork below the level of the floor, each pit being about 3 inches wider across the mouth than the ingots it is intended to accommo- date, so as to allow space for the fins of metal, &c., often hanging to the bottoms or tops of the ingots. The pits are also built from 6 to 18 inches deeper than the length of the ingot, and they should be lined with very heavy fire-bricks to withstand heavy wear and the blows of falling ingots. A separate lid or cover is . applied to each of the pits to exclude atmospheric air, and the whole is served by an ingot crane, which lifts the ingots from the pits and delivers them at the blooming rolls. Before using the soaking arrangement it is necessary to first well dry the brickwork, and then to heat it to redness by placing hot ingots within the pits, after which the apparatus is ready for work. As soon as the ingots are stripped in the casting pit, they are lifted out at once and placed by the crane into the previously- heated soaking pits, where they are covered by the lids above mentioned, and there allowed to remain during from twenty to thirty minutes or upwards according to the size of the ingot; after this interval the excessive heat of the molten metal in the interior, with the latent heat which has become sensible during solidification, becomes more evenly distributed throughout the mass, whereby the metal presents a fairly uniform temperature throughout, with a surface heat in excess of that presented by the ingot on its first introduction into the pit, and altogether the metal is sufficiently hot for treatment in the rolls or under the hammer. Comparatively little heat escapes during the process of soaking, since the ingot is surrounded by a mass of brickwork, which is heated by the surplus heat of the ingots successively introduced into the pits to a temperature almost equal to that of the ingots themselves. 644. During the soakkig a quantity of gas exudes from the metal and fills the pits with a non-oxidising atmosphere of hydrogen, nitrogen, carbonic oxide, and 384 STEEL AND IRON. [Chap. XVIL carbonic anhydride, to the exclusion of atmospheric air, and the loss of metal by oxidation is therefore avoided. The above gases are seen escaping slightly around the covers of the pits during the soaking operation, and when the covers are lifted combustion of the enclosed gases at once ensues. CHAPTER XVIT. STEEL AND INGOT IRON. 645. STEEL is essentially a compound of pure iron with small per-centages, ranging usually from O'l to 1-25 per cent, of carbon, existing, not as graphite, but either as combined or dissolved carbon, the latter view now receiving influential support. All other elements, although several are invariably present in greater or less proportion, must still be regarded as impurities in the steel, notwithstanding that it may be advantageous to introduce some of them to impart special qualities to the metal, or to neutralise the effect of the presence of others of them. ANALYSES or STEEL. g>| S- 5 . . | Is II B se II 'l |-| II P.2 -of 5.2 || |- 1 22- 5 1 ij 11 CO 0-08 2-60 0*94 Silica . Phosphoric anhy- ) dride J 20 '52 per cent. 5-25 Sulphur . 3-09 trace Ferric oxide . 6-24 Phosphorus . . 0-48 0-075 Ferrous oxide 62-14 Silicon . 0-99 O'll Alumina 3-00 Manganese . 2-01 < 0-27 Lime and Magnesia ' I'oO 750. The conduct of the process, as above described, is practically the same as the pig-boiling process (p. 261), except, that for the production of puddled steel, the decarburisation or fining of the pig-iron is effected more slowly although less completely than in pig-boiling; thus the process for the production of puddled steel lasts from one hour and fifty-five minutes to two hours and fifteen minutes, permitting of only five or six charges being worked off during the twelve hours ; while the puddling or pig-boiling process for the production of malleable iron, usually lasts only from one hour and thirty-five minutes to one hour and fifty-five minutes per charge when working the usual charges in single furnaces, or between six and seven charges are worked off during the day of twelve hours. The consumption of fuel, also, which ranges between 20 and 25 cwts. of coal to the ton of malle- able iron produced, reaches to 25, 30, or 35 cwts. of the same coal for the production of a ton of puddled steel ; but the use of the Siemens gas furnace in the puddling of steel is attended with a considerable economy in fuel ; the metal produced, however, is said to be less homo- geneous, from the presence of intermixed cinder, necessi- tating re-melting, whilst the metal also welds very irnper- Uhap.XIX.] PUDDLING OF STEEL. 439 fectly. The loss of weight between the puddled steel bar and the original pig-iron is between 6 and 9 percent., or, as might be expected, slightly less than when malleable iron is produced. 751. The slag or cinder from the puddling of steel, is more fluid, is less rich in iron and is consequently less de- carburising than the cinder occurring in the corresponding stages of the puddling of malleable iron. For maintaining this condition of the slags such materials as quartz, clay, mill-cinder, poor slags, &c., are added to the furnace during the melting-down stage; and for still further promoting the fluidity, &c., of the cinder, black oxide of manganese is sometimes added before balling up the metal. 752. As in the crucible steel processes, so also in the puddling of steel, the use of various physics for the elimination of sulphur and phosphorus from the charge have been proposed and tried. Of such are potassic chromate, potassic ferrocyanide, and other cyanogen com- pounds or mixtures containing carbon; but a more general physic sometimes employed in this process is SchafJiautVs powder, which consists of a mixture of black oxide of manganese, common salt, and potter's clay. It is added at intervals during the rabbling of the charge, and before the balling up. 753. The shingled blooms of puddled steel are re- heated either in the hollow tire or in the balling furnace before either tilting under the hammer, or rolling into bars. 754. Mr. Eiepe, under whose patent the production, of puddled steel was formerly carried on at the Mersey Steel .tnd Iron Company's works, and at the Low Moor Iron- works, proposed to work upon less than the usual charges of pig-iron, and so he introduced only about 2 cwts. of metal at each heat. The patentee also appeared to attach considerable importance to the working of the furnace at the lowest possible temperature, for which purpose, as the. metal melted, the damper was partially 440 STEEL AND IRON. [Chap. XIX. jlosei ; and afterwards twelve or fourteen shovelsful of forge or mill-cinder were added, and the whole carefully melted down, after which the molten metal was worked with the addition of a small quantity of a mixture of black oxide of manganese, common salt, and clay, all ground together. After the lapse of some minutes the chimney damper required to be raised, and about 40 Ibs of pig-iron was placed near the fire-bridge upon a bed of coke put there for the purpose, so that when the bath began to boil and the pig near the bridge was trickling down into it, the whole of the pig-iron was then raked down into the bath of metal and the mixture well incorporated, whereupon boiling commenced, jets of carbonic oxide issued from the surface and grains of steel began to appear through the surface of the cinder; the damper was then partly closed and the rabbling continued, the jets of carbonic oxide gradually disappear- ing as the metallic grains collected together, and the whole mass assumed a pasty consistency. The charge was then balled up into several balls, the portion not forming the first balls being kept well covered with cinder, and it was said that if the temperature was maintained too high throughout this stage, the charge afforded less uniform results, and much of the metal passed into the condition of malleable iron. The balls were subsequently shingled and worked into bars as usual. 755. Amongst other processes for the partial decarburi- sation and elimination of silicon, sulphur, and phosphorus from pig-iron with the production of steel thereby, are the chemical methods of refining proposed by Mr. Heaton and Mr. Henderson. 756. The Heaton Process, known also as the nitrate process, is a refining operation in which sodic nitrate instead of atmospheric air is employed as the refin- ing agent. The operation is conducted in a circular cupola or converter, formed of iron plates lined with fire-brick or fire-cla} and fitted with a movable bottom Chap. XLK.] THE HEATON PROCESS. 4H secured to the body of the cupola by iron clamps. Into this bottom is introduced the charge of 10 or 12 Ibs. of sodic nitrate to the hundredweight of metal to be refined, and this is covered with a perforated cast-iron plate to prevent its floating upwards as the fluid cast-iron is subsequently run into the converter, whilst a little silica (sand) and air-slacked lime are also sometimes added along with the nitrate. 757. The sodic nitrate being thus charged into the bottom of the converter and secured in position by the perforated plate just mentioned, the molten pig-iron is then run in from above through a spout provided for this purpose, and in about two minutes brown nitrous fumes begin to appear within the converter, followed by blackish grey and then whitish fumes, but it is only after some five or six minutes that the cast-iron perforated plato is melted by the fluid pig-iron, whereupon a violent reaction immediately ensues, accompanied by an active state of ebullition in the metal and the emission of a bright yellow sodium flame from the chimney or top of the cupola. After continuing for about 1^ minute the ebullition ceases and the metal settles down, whereupon the bottom of the cupola is detached, and removed upon a truck placed beneath the converter. The crude steel and slag are then poured or turned out on to the floor, since the metal is not sufficiently fluid to permit of its being directly cast into ingots. 758. The crude steel so obtained is broken up and the pieces are subjected to sundry pilings, reheatings, and shingling into blooms, which are again cut up and again reheated for rolling into bars ; or, instead of piling and shingling into blooms as just mentioned, the crude steel is at once hammered into blooms or flat cakes, which are broken up into small pieces, sorted carefully, and then melted in crucibles for the production of cast-steel in the ordinary manner. The process yields, however, a very irregular product, and is not carried out on a manufacturing scale. 442 STEEL AXD IRON. [Chap. XIX. ANALYSES OP PRODUCTS, &c., OF THE HEATON PROCESS. Pig-iron introduced into cupola (Miller). Hard 1 Hard crude steel crude steel (Miller). , (Snelus). 1 Soft crude steel (Miller). Soft crude steel (Snelus). Carbon . 2-330 1-800 2-061 993 1-098 Silicon with a) little titanium | 2-950 266 014 149 trace Sulphur . 113 018 trace trace trace Phosphorus 1-455 298 489 292 344 Arsenic . 041 039 024 Manganese Calcium . 318 090 319 064 088 310 072 Sodium . 141 . Metallic iron 92-293 97-026 98-144 759. From these analyses it is obvious that the pro- cess effects a partial refining of the pig-iron, whereby there is a material decrease in the proportion of carbon, but the sulphur and phosphorus are only partially eliminated, whilst silicon is present only in small proportions in the crude steel produced by this process. 760. The Henderson or Fluorine process, like the last described, is a fining process intended to produce malle- able iron or steel from inferior or Cleveland pig-iron, by the decarburisation and separation therefrom of silicon, sulphur, and phosphorus under the influence of fluorine liberated from a bed of fluor-spar spread upon the hearth of a puddling furnace, and upon which is placed a titanif erous pig-iron produced by the fusion of about 20 cwts. of Cleveland pig-iron with some 7 cwts. of Norwegian titaniferous iron ore. By the fusion of such a charge upon the bed of a puddling furnace prepared as above, the silicon, sulphur, and phosphorus of the pig-iron are partially eliminated. It is claimed that 80 per cent, of the phosphorus in the pig-iron escapes in a vaporous form, and that only the remainder passes into the slag, which is thus, unlike the ordinary puddling-furnace cinder, not too phosphoric to permit of its use in the blast-furnaca Chap.XIX/| THE UCHATIUS PROCESS. 443 The operation is entirely completed by working the charge under a layer of slag, and no stirring or rabbling is necessary during the conduct of the process, the only manual labour after charging being that of balling-up the charge. 761. A simpler modification of the Henderson process consists in mixing at once the finely ground fluor-spar with titaniferous iron ores upon the bed of the puddling fur- nace, and charging thereupon about 4 J cwts. of pig-iron ; after which the furnace is closed to prevent the admission of air, and the temperature is raised as high as possible. Under these conditions the mixture of fluor-spar and titanic iron-ore on the bed of the furnace only assumes a pasty con- dition, which is favourable to the slow decomposition of the calcic fluoride (fluor-spar) by the silicon and other elements of the pig-iron. The heat generally lasts about ninety minutes, but after about seventy minutes from the time of charging the sampling of the bath commences, and is con- tinued every few minutes until the process is judged to be complete. As in the previous modification, there is no stirring or rabbling of the charge. 762. Of the methods for the production of steel by the fusion of pig-iron with rick ores or oxides of iron, the most important is the Siemens open-hearth direct process (p. 456). The Uchatius process, although pursued in Sweden with some measure of success for the treatment of pig-iron with the magnetic iron ores of Bispberg, has been discontinued in England, owing largely to the want of uniformity in the product obtained. It consists in the production of a crude steel by the partial decarburisation of pig-iron, by fusing the latter along with materials capable of yielding oxygen, such as ferric oxide, roasted iron ores, &c. The pig-iron is first melted in a cupola, and is then granulated either by running the molten metal into water or by other suitable methods, after which a mixture is made of the granulated pig with 20 per cent, of its weight of the roasted and pulverised spathic iron ore or oxide of iron, 444 STEEL AND IRON. [Chap. XH with a little black oxide of manganese, and about 4 pei cent, of its weight of fire-clay ; such a mixture is then charged into clay crucibles and melted in an ordinary furnace, under which treatment the ferric oxide suffers reduction by the carbon of t*he pig-iron with the evolution of carbonic oxide, and a proportionate decarburisation of the pig-iron to the condition of steel is the result. If the softer welding tempers of steel are to be produced, then, in addition to the above mixture, a small quantity of malleable iron is added to the crucible charge, while harder tempers are obtained by the addition of charcoal. The yield of cast-steel from the crucibles is usually some 6 per cent, in excess of the weight of the pig-iron em- ployed, and generally the finer the granulation of the pig- iron the milder is the temper of the steel produced. 763. A modification of the Uchatius process goea under the name of the Ellerhausen process, but it differs from it in the manner of mixing the pig-iron with the oxidising materials, such as powdered haematite, iron sand, or powdered magnetite; thus, instead of the granulation adopted in the Uchatius process, the mixture of pig-iron and decarbu rising materials used in the Ellerhausen process is effected by running simultaneously the fluid metal from the blast furnace and the iron ores as above, into a series of moulds placed on a revolving table. The pig-blooms so produced are melted and puddled upon the bed of a puddling furnace, yielding iron or steel according to the method of puddling and consequent degree of decarburisation effected, but, as in the Uchatius process, and in all other methods of producing steel by the fusion of mixtures of pig-iron and oxidising agents, such as iron ores, arsenious anhydride, nitre, &c., the product is irregular in temper and quality, and these processes do not, therefore, me^t with favour in England. 764. The production of steel by the decarburisation of pig-iron by the Si-emens open-hearth process is described in the next chapter (p. 456.) 445 CHAPTER XX. PRODUCTION OF STEEL BY THE FUSION OP PIG-IRON WITH MALLEABLE IRON OR WITH IRON ORES IN THE OPEN- HEARTH STEEL-MELTING FURNACE. 765. THE methods of producing steel in the open- hearth regenerative furnace of Sir W. Siemens are divisible into three classes, according as iron ores are added to the furnace charge or otherwise. Thus steel is produced on the large scale in this furnace: 1st, By the fusion alone of a mixture of pig and scrap-iron or scrap-steel consti- tuting the Siemens-Martin process ; 2nd, by the treatment of pig-iron with certain classes of iron ores without the addition of scrap, according to the direct open-hearth pro- cess of Sir W. Siemens ; and 3rd, by a combination of the two processes according to which pig-iron, iron or steel scrap, and certain pure iron ores are treated in the same furnace. Whilst the first is the more generally pursued on the Continent, the third process is preferred in England, and latterly it has become customary to desig- nate the steel made by any of the above modifications as "open-hearth steel." The open-hearth processes are under better control than the Bessemer, since ample time is afforded by them for the testing of the metal, and for the addition of such proportions of pig-iron or of iron ore as are required, so as to yield a more or less carburised product according to requirements. 766. The open-hearth steel-melting and regenerative gas furnace generally employed in these processes enables the highest temperatures to be attained without requiring a strong draught or inducing a cutting flame. The fur- nace resembles in its general arrangements the reheating furnace (p. 371), and, like it, is constructed with two pairs of regenerators, A, A, G, G (Fig. 86), built trans- versely beneath the furnace bed, and it is provided with a 446 STEEL AND IRON. [Chap XX reversing gas valve, g, and air valve, a (Fig. 87), similar in construction and action to those already described, except that, a higher temperature being required in the melting furnace, the several valves and also the heating surface of the regenerators, are made proportionately greater, u (Fig. 87) is the gas culvert, whilst v is the flue leading to the chimney. Above the regenerators is the furnace, with its hearth supported upon cast-iron plates, b, b (bath-plates, Fig. 86), between the under-side of which and the top of the regenerator chambers air is free to circu- late for the cooling of the bottom. The plates are lined with a single thickness of fire-brick, and above this is made the bottom of quartzose or other refractory sand, introduced, when the furnace is hot, in layers about 1 inch thick, each layer being rammed down gently and partially vitrified or glazed before the next one is applied, a total depth of from 14 or 16 inches of sand being in this manner introduced. The bottom so prepared re- quires repairing and levelling a'fter each heat, and before introducing the succeeding charge, by placing fresh sand in the holes or pits left in the bottom when the metal has been tapped out. The ordinary bed is formed of siliceous sand, as just described, but basic linings have been tried and used successfully in Austria, France, and in England for rendering the process a basic one for the treatment of phosphoric pig-iron if required; while in some of the Continental furnaces working the ordinary Siemens-Martin process, the bottom is also formed of a mixture of clean sand and burnt quartz in equal propor- tions, incorporated with 15 per cent, of fire-clay. 767. The hearth, h, is regular in form, and slopes from all sides towards the tap-hole, p, situated at the back, below the middle working door. At the front side of the furnace are three doors, of which the two side ones are principally used for introducing the charge of pig-iron and scrap, whilst the central one is a little lower than the other two and forms the working-door through which the ore or other additions of pig or scrap required during the 447 t 86. Longitudinal Section of the Siemens Open-Hearth Steal- Melting Furnace. Tig. S7. Cross Section of the Siemens Steel-Melthur Purnnonu 448 STEEL AND IRON. [Chap. XI. working are chiefly introduced. The ports, s, 8, are five in number in each end or block of the furnace, and of these the three delivering the heated air from the regenerators to the hearth open at a higher level than the other two ports through which the gas is delivered. The two ends of the furnace are quite symmetrical, and are con- structed of Dinas or silica bricks, as is also the long roof, r, which slopes downwards towards the centre of the hearth from each end of the furnace, and direct? thereby a plunging flame on to the centre of the hearth. The furnace is supported externally by cast-iron buck- staves, plates, rails, tie-rods, advantages of being able to test or sample the metal after the manner of the Siemens process, thereby ensuring the greater uniformity characteristic of the latter metal with some of the rapidity of conversion presented by the Bessemer process. For this purpose, the first part of the operation, during which a blast of air is passed through the fluid metal, is conducted as rapidly as possible, after which the hearth is turned round so as to close or shut off the blast, and the process is then continued to completion after the manner of the Siemens process. 777. The Ponsard furnace, already described (p. 380), has a circular, movable, and inclined hearth, mounted Chap. XX.] THE PONSARD REVOLVING FURNACE. 453 on wheels, and which can be turned through half a revolution upon an inclined axis. A, A, G, G (Fig. 88) are the air and gas regenerators respectively. The furnace is fitted with the usual arrangement of valves, C Fig. 88. Vertical Section of the Ponsard Steel-Melting Furnace. &c., for reversing the direction of the current of th& air and gas, the latter passing from the producers, through the regenerators, G, to the hearth, c, by the port, b, where it meets with the heated air required for its combustion ; the air having ascended on its way to the furnace through the regenerator, A, along the flue, e, to the air port, f, while the flame and products of com- bustion pass away from the hearth, c, through the regene- rators at the opposite end of hearth, and thence to the chimney. 778. As previ- ously noted, this i i Fig. 89. Transverse Section of the Ponsard furnace has been Furnace on line C D (Fig. 88). applied with re- ported success to a sort of combined Siemens and Bessemer arrangement for the production of steel, for which purpose a blast of air is conveyed to a chamber, d, in the bottom of the spindle or axis, upon which the 454 STEEL AND IRON. [Cliap. XX. hearth rotates, and is from thence conveyed by a pipe to a t wyer box, z, from which three or more twyers open into the bath of metal, as shown in the cross section (Fig. 89). The charge of pig-iron is either melted on the hearth or is introduced on to it in a molten state through the runner, m ; and then, after blowing the charge for some minutes, during which the door, g, is opened for the escape of the flame, the furnace is rotated by the gearing, x, through half a revolution, by which the twyers, k, are rotated to the upper side of the hearth above the level of the metal. The blast is then shut off, and the completion of the decarburisation, fining, and sampling is pursued in the usual manner of the open-hearth process, with the addition of spiegeleisen or of ferromanganese at the end of the decarburisation, as in the ordinary open-hearth process. The metal is tapped out into the ladle from the tap-hole, b, which now occupies the lowest position in the bed of the furnace, and is placed opposite to the spout, m, by which the fluid metal is introduced. The furnace is supplied with gas from gas producers of the ordinary construction. The hearth or bed, c, also can be withdrawn upon the carriage, N, as shown, so as to permit of the ready repair of the roof without waiting for the cooling down of the same, whilst by uncoupling the blast arrangements the whole hearth after withdrawal from beneath the roof, can be run away upon a line of railway, and a relined, or repaired and dried bottom can be quickly run into position under the roof with but little delay. The combined Bessemer and Siemens processes have not been as yet generally applied, but it is obvious that this furnace is available for either the Bessemer, the Siemens, or the combined processes of Bessemer and Siemens, as above described. 779. The combined open-hearth and Bessemer process is conducted in Styria by first running the pig-iron from the blast furnace into the Bessemer converter, and there partially decarburising it by blowing air through it ; but before complete decarburisation is effected the metal Chap. XX.] OPEN-HEARTH AND BESSEMER PROCESS. 455 is poured from the converter into a ladle, and is thence conveyed to a fully-heated Siemens furnace, where it boils during some three or four hours, and at intervals additions of malleable iron and scrap steel altogether equal to 4 or 5 per cent, of the charge, are made, until finally, when the desired temper or degree of decarburisation has been reached, some 5 or 6 per cent, of spiegeleis-en and a little ferromanganese are added. The combined process is best adapted to the production of the harder classes of steel ; it requires, however, careful manipulation, and its success depends largely on being able to maintain the boil in the Siemens furnace during the entire refining period. 780. Attempts have been made to shorten the open- hearth process by blowing air or steam into the bath of molten metal during the earlier stages, for which purpose a hollow rabble conveying air or steam into the bath is in- serted through the furnace door ; but these processes are not at all of general application. The combined process as pursued at Ruhrort, is effected* by introducing the blast through twyers formed of iron tubes covered with fire-clay, and each bent over at the end so as to form a nozzle of about one inch in diameter, with three blast outlets in each nozzle. Three of these twyers are introduced horizon- tally into the furnace, and then turned downwards so as to dip into the molten metal on the hearth, and thus to deliver the blast below the surface, whilst the three twyers are joined outside the furnace into one pipe, connected by a flexible tube with the blast supply. At Ruhrort, the charge consists of 35 per cent, of white iron, with 65 per cent, of scrap, which are melted in the Siemens furnace, and then blown for fifteen or twenty minutes by an arrangement as above, with blast at a pressure of about 12 Ibs. per square inch. The temperature of the bath rises much higher than in the ordinary Siemens- Martin process, and occasionally necessitates the ad- dition of cold rail ends or other scrap to the bath. * Prof. Kupelwieser : Oest. Zeitwhrift fur Berg- und Hiittenwescn, 1882. 456 STEEL AND IRON [Char- XX. The operation of blowing is also attended with the escape of brown fumes from the surface of the bath. 781. The Siemens open-hearth process, in which pig- iron, steel scrap, and the purer haematite iron-ores are employed, is generally preferred in England to the scrap process alone, although there is no special necessity for the use of scrap in the process, except that it is a convenient mode of using up the large proportion of scrap of various kinds, such as crop ends of rails, bars, shearings., &c., largely produced in all steel works. 782. The open-hearth process is conducted in the Siemens regenerative steel-melting furnace, described p. 445, and into the heated furnace the charge of about 30 per cent, of haematite pig-iron, with 70 per cent, of steel scrap, is introduced. The pig-iron is first introduced and distributed over the bed of the furnace, when the scrap is placed upon it, and after complete fusion of the charge, Spanish or African rich haematite iron-ore in lumps is added at intervals for the decarburisation of the bath of metal. In this manner during the working of an 8-ton charge of metal, from 25 to 28 cwts. of ore will be added, each addition of ore being followed by a state of violent ebullition or boiling of the metal on the furnace hearth. Samples of the metal are with- drawn from time to time, and are tested for malleability, for toughness, and for carbon, as described for the Siemens-Martin process, whilst ore or pig is added from time to time, according as further decarburisation or in- creased hardness is required. When the desired degree of softness has in this manner been attained, the metal is allowed to stand for a short time in the furnace, to clear itself of slag, and small quantities of limestone are also added during the process if the covering of slag be insuffi- cient, its addition also throwing down a proportion of iron from the slag, which otherwise would pass away unreduced and be lost. Spiegel, or ferromanganese, or a mixture of these, is added at the end of the process, in the same manner as in the conduct of the Siemens- Mart in process; or for the Chap. XX.] OPEN-HEARTH STEEL PROCESS. 457 production of very soft metal, where only from J cwt. to 1^ cwt. of ferromanganese is required for the recar- burisation of an 8-ton charge ; the ferromanganese is often first heated to redness and then added direct to the metal in the ladle as it runs from the tap-hole of the furnace. 783. In the Siemens process the yield often exceeds by from 1 to 2 per cent, the combined weights of the pig-iron and scrap introduced into the furnace, since in the decarburisation of the pig-iron a proportion (probably amounting to about one-half) of the ore which is added suffers reduction, and the metal so separated passes into the steel and increases the yield. 784. The duration of the open-hearth process where iron-ores are employed is from nine to eleven or twelve hours when working upon 8-ton charges, and is thus some- what longer than the scrap process, while the hearth is also more strongly attacked by corrosion than in the last- mentioned process. The methods of tapping the furnace and casting of the rnetal into ingots are the same as in the Siemens-Martin process. The moulds, also, and the arrangements for casting described under the Bessemer process, are also available for, and are used in this process 785. One block of four ordinary Siemens gas-producers will yield gas sufficient for an 8-ton melting furnace, and the consumption of coal in the process varies from 10 to 14 cwts. per con of metal produced, according to the quality of the coal and temper of the steel to be produced. 786. The Siemens open-hearth, liketheBessemerprocess, proceeds by first decarburising the bath of molten metal, and then recarburising it by the addition of spiegel- eisen, ferromanganese, or other highly manganiferous alloy of iron, &c. This addition obviously introduces at the same time a small proportion of other impurities, like sulphur, silicon, phosphorus, &c., into the steel; but this result is now minimised by the almost universal use of ferromanganese as the recarburising material, whereby 458 STEEL AND IRON. [Chap. XX. a smaller weight of the recarburising alloy is required for the introduction of sufficient manganese into the steel to prevent the red-shortness otherwise manifested by the metal, and to improve its malleability, without at the same time introducing too much carbon and such im- purities as attend the use of the larger amounts of spiegeleisen ; and the use of ferromanganese is therefore especially necessary in the production of soft or mild steel. One advantage of the open -hearth process is that the steel can be quite dead melted, the process not being limited as to time, since the nature of the flame and the temperature of the furnace are so much under control that the bath of fluid metal, after having been reduced to the lowest degree of carburisation required, may stand comparatively unaltered for any reasonable period, during which time samples may be taken for testing as required, and additions of pig-iron, wrought- scrap, spongy metal or iron-ore made to adjust it to the desired temper and quality, whilst spiegeleisen or ferro- manganese can be added in the solid condition immediately before casting in the required proportion, with the obtaining of a product (steel) of which almost the exact composition is known before casting. 787. In the open-hearth methods of producing steel the decarburisation and the separation of silicon and man- ganese from the pig-iron of the charge, do not appear to pro- gress with the regularity which occurs in the Bessemer converter. Daring the first period or melting down of the charge in the Siemens furnace, the carbon, silicon, and manganese are each more or less oxidised, so that at the end of this stage about 50 per cent, (the proportions varying with the temperature of the furnace) of these elements has been removed. After the charge is melted down, however, the metal remains tranquil in the bath, undergoing little, if any, decarburisation, until the whole of the manganese has been oxidised, and the silicon in the molten metal has been reduced to about -02 per cent. ; this condition is attained in from three to four hours, after . XX.] BASIC OPEN-HEARTH STEEL PROCESS. 459 which the bath of metal begins to boil from the escape of carbonic oxide, resulting from the oxidation of the carbon, and this state continues until the carbon is re- duced to about Ol per cent, or under, at which point the bath again becomes tranquil, and the slag, which thirty minutes previously was of a brownish colour, begins to blacken, owing to the slight oxidation of iron now going on. 788. Haematite pig-iron containing but small propor- tions of sulphur or phosphorus is used for the open-hearth processes, since practically the whole amount of the two elements just named remains in the finished steel, unless the hearth be specially prepared of a basic character, as by the use of bauxite and magnesic bricks, or of a mixture like calcined dolomite and anhydrous coal-tar, which mixture under the heat of the furnace, yields a hard, basic, refractory lining. By conducting the open-hearth processes upon such a lining, with the addition at short intervals of a small proportion of lime and iron ore to the charge, a highly phosphoric and basic slag is produced during the working, which, owing to the excess of lime present, removes the silicon completely, and the phos- phorus almost totally, so that a steel is obtained prac- tically free from phosphorus. As conducted at Creusot, a 15-ton charge of pig-iron and common iron scrap, refined under a current of gas as in the ordinary Siemens- Martin process, but in a basic lined furnace, is worked off in twelve hours. The roof of the furnace is of silica brick, as usual, but the junction between the roof and the sides of the hearth is made by a course of bauxite brick. 789. Pig-irons containing but little carbon or silicon are preferable for the open-hearth processes, since such irons require less time for decarburisation and fining, whilst also siliceous pig often yields an inferior steel, although the silicon may be, and is, wholly oxidised in the furnace. Manganese, when present beyond 0'5 per cent., delays the process, and also 460 STEEL AND IRON. (Chap. XXI. tends to destroy the siliceous bottom of the furnace owing to the formation of fusible slags of manganous silicate. But, notwithstanding the above remarks, a mixture of several brands of iron is always preferable for ensuring uniform results, and chemical analysis alone is not sufficient to determine the quality and adaptability of a pig-iron for conversion into steel by this process, since frequently chemically similar irons will act quite differ- ently in the furnace as to prolonging the process, destroying the bottom, and yielding a metal of deficient strength. 790. The iron-ores employed in the ordinary direct Siemens open-hearth process for the decarburisation of the pig-iron should be, for reasons above stated, of the purest classes, and as free as possible from sulphur or basic sulphates ; the ores more generally used for addition to the bath of metal are the Elba, Sommorostra, Mockta, and Marabella haematites. CHAPTER XXI. THE BESSEMER OR PNEUMATIC PROCESS FOR THE PRO- DUCTION OF STEEL FROM PIG-IRON. 791. THE conversion of pig-iron into steel by the Bessemer process, of which the world's present annual production amounts to nearly 3,000,000 tons, essentially consists in blowing a large volume of atmospheric air through molten pig-iron. The blast is introduced from below, and the molten pig-iron is decarburised and fined by the oxidation and combustion of its carbon, sili- con, and manganese, with the development therejby oi sufficient heat to keep the bath of metal in a fluid state to the end of J-he .process ; while the met^l so decarburised is usually then recarburised to the -desired degree by the addition of a certain proportion of the Chap. XXI.] THE BESSEMER PROCESS. 461 white manganif erous pig-iron known as spiegeleisen, or by the addition of a special alloy richer in manganese, . con- stituting the ferromanganese of commerce. The Bessemer process is not adapted to the production of malleable iron, but it yields a steel, or, as it is occa- sionally called, " ingot iron," at a cheap rate, of fair quality for structural purposes, and possessing in its several grades a great range of temper or hardness. 792. Grey pig-iron is solely used for the process, since as the decarburisation and conversion into steel are entirely effected by the action of the oxygen of the air forced through the metal, the greater fluidity of grey iron is manifestly advantageous, since the plasticity of molten white iron is liable to interfere with the free passage of the blast through the metal during the earliest stages ; but nevertheless, as will be shown when treating of the basic process, white or mottled iron may be employed, but not so advantageously as grey. 793. In the Bessemer process the oxidation and refin- ing of the metal proceed simultaneously throughout the en- tire mass of the charge, and it is thus unlike the puddling process where the fining proceeds largely at the surface of the metal, under the combined influence of the oxygen of the air and of the oxides of iron and manganese in the puddling furnace cinder. In the ordinary Bessemer process, as conducted in a converter lined with ganister, practically the whole of the sulphur and phosphorus in the pig-iron remains in the steel produced, and since the yield of steel is some 10 per cent, less than the amount of pig-iron introduced into the converter, the proportions of these elements (sulphur and phosphorus) may be absolutely a little greater in the steel than in the pig-iron from which it has been produced ; but in the puddling process it has already been shown that from 75 to 80 per cent, of the elements sulphur, phosphorus, and copper are removed in the cinder produced in the furnace. Hence for the original Bessemer process only the purer pig-irons, such as the haematites of Cumberland and 462 STEEL AND IRON. [Chap. XXI. elsewhere, which are practically free from the above delete rious elements, are available ; but by a modification of the process introduced by Messrs. Thomas and Gilchrist, and known as the "basic process," in which the Bessemer converter is lined with a highly basic dolomitic lining, tho sulphur and phosphorus of the pig-iron are very largely eliminated from the charge, and so phosphoric pig-irons, such as those of Cleveland and the Continent, are made available for use in the specially lined Bessemer converter. 794. The Bessemer process thus comprises the original process as conducted in a siliceous or acid-lined converter, and now generally known as the " acid process," and the " basic process " as conducted in a basic- lined converter ; but it is with the former, or acid process as conducted in the siliceous or acid-lined converter, that the considera- tions in the piesent sections refer. 795. In the conduct of the Bessemer process a blast of atmospheric air is supplied to the Bessemer converter at a pressure of from 18 to 25 Ibs. per square inch, accord- ing to the weight of the charge, and the consequent depth of metal through which the blast has to be forced by the blowing engines. The blast is admitted from a number of small jets or perforations in the twyers fixed in the bottom of the vessel, and ascends through the molten pig-iron contained in the converter. Its effect is to oxidise and burn out almost the whole of the carbon, silicon, and manganese of the pig-iron, their removal following the same order as occurs in the puddling furnace or in the refinery, and the rapid combustion so set up within the converter raises the temperature of the bath to a very high degree, the rise of temperature com- mencing almost from the first entrance of the blast and continuing to the conclusion of the blow. 796. The Bessemer process is conducted in a vessel or converter, which may be either fixed, in the manner adopted to a limited extent in Sweden and revived by a patentee in South Wales, or, as is much more general, it is capable of rotation in a vertical plane through an Chap. XXI.) THE BESSEMER CONVERTER. 463 angle of a little more than 180, for which purpose it is supported upon a pair of trunnion arms, resting upon suitable standards. The movable converter affords greater facilities for discharging the metal from the vessel at the end of the blow, and also by simply turning down the vessel into an almost horizontal position the charge lies outside the range of the blast from the whole of the twyers, and may there remain for some time after the blast is shut off. With the fixed vessel a me- chanical arrangement -of a stopper or plug actuated by steam or air is necessary to close each twyer, to prevent the metal from running into and stopping up the air passages when the blast is stopped at the end of the blow. 797. The movable converter generally adopted for the conduct of the ordinary Bessemer process gives, as just noted, greater facilities than the fixed vessel for emptying out the charge of metal and slag after the completion of the blow by pouring it from the mouth instead of tapping it out from the bottom, as is necessary with the fixed vessel. The usual form of the converter is that shown in Fig. 90 ; it consists of a shell of wrought-iron plates riveted together, of which the neck or throat, a, of the vessel is inclined at an angle of about 30 to the body, b. The neck is directed, when the vessel is in the vertical position, towards an open chimney or stack, K, into which the gases, flame, sparks, and ejections of slag, &c. , occurring during the blow, are directed, and the hood, s, forms a like protection against sparks during the period the vessel is passing from the horizontal to the vertical position. Around the centre of the body of the converter is a stout band or trunnion ring, upon which is a pair of trunnion arms, A, by which the vessel is suspended upon cast-iron standards, or other supports. These converters, or vessels, have usually a capacity sufficient for the treatment of 6, 8, 10, or 15 tons of pig- iron at a single charge, and must not only be large enough to conveniently hold these amounts of fluid metal, but must also afibrd sufficient space to prevent the 464 STEEL AND IRON. [Chap. XXI ejectment of the metal during the most active period of the boiL An 8-ton converter will accordingly measure Fisr. 90. Arrangement of the Bessemer Converter. at the trunnions about 8 feet 4 inches inside the casing, or 6 feet 10 inches inside the lining, the latter having a thickness of about 9 inches; whilst the shell plates are made f , {, and 1 inch in thickness, according to the Chap. XXI.] THE BESSEMER CONVERTER. 465 capacity of the vessel. The neck, a, of the converter forms a kind of spout during the teeming of the metal into the ladle, and its position also tends to prevent the ejections of metal, &c., during the blow. The size of the neck also requires consideration, since if it be too wide there is a loss of heat, and a tendency to deposit metal (skulls) around the mouth and inside of the vessel during the blow, and if the opening be unduly small, then the back pressure within the vessel is increased and the duration of the blow is prolonged. 798. Of the two trunnions, A, one is solid and carries a pinion, c, into which gears a rack, d, forming a prolonga- tion of the ram or piston, e, of an hydraulic cylinder, which may be placed vertically in the masonry below, or horizontally, as shown. By the movement of the ram, e, the converter can be rotated through about, -^ths of a revolution, by which the vessel can be moved into any position between the extreme vertical, when the mouth is directed towards the chimney, K, and the corresponding opposite position, where the mouth is directly downwards as required for the discharge of the slag, &c., from the vessel. The rack and hydraulic piston are thus required to be double-acting, so as to tip the vessel either upwards or downwards, and its action is controlled by a valve worked by hand, and placed at some distance from the vessel. The dotted lines in Fig. 90 show the vessel rotated into the horizontal position for receiving its charge of molten pig-iron, or of spiegeleisen, from the trough, D. The trunnion, c (Fig. 91), on the opposite side of the converter, is hollow, to permit of the passage through it of the blast from the blowing engines. From the hollow trunnion a pipe, c?, of elliptical section passes to the cylindrical chamber, or twyer boxjf, forming the movable bottom of the converter, but retained in position by means of bolts and cotters. The bottom, or guard plate, g, forming the upper side of the twyer box, f t is perforated by ten or fifteen (according to size of the vessel) circular holes pitched at equal distances E 466 STEEL AND IRON. [Cliap. XXL from one another, and into each of these holes is inserted a slightly conical fire-clay twyer, k, of about 20 or 22 inches in length, and perforated in the direc- tion of its length by ten or twelve holes of f inch in diameter for the admission of blast from the twyer chamber, f, to the body of the vessel. The lower ends of the twyers stand slightly below the lower surface of the guard-plate, but each twyer is held up in contact with the plate by stops carried in horizontal arms, which can be turned aside as required for the removal and renewal of any twyer, and for which purpose also the bottom plate, t, of the twyer box can be quickly removed. Thus, after knocking out and removing any faulty twyer, a new one is readily inserted by first luting it around with fire-clay, then driving it into the opening in the guard-plate, and finally securing it in position as before with the stops, and subsequently running in slurry that is, a semi-fluid mixture of gaiiister and fire-clay with water around the inside of the twyer so as to make a good joint ; and after replacing the bottom plate, 2, the bottom is dried, and the vessel is again ready for the reception of its charge. 799. Various arrangements in connection with the hollow trunnion have been devised for automatically turning on the blast as the^.converter is moved from the horizontal to the vertical position, so that during this movement the metal should not pass into and close the passages in the twyers ; arid also to shut off the blast, as soon as the metal in the converter is below the level of the twyers, in turning over from the vertical into the position for teeming at the conclusion of the bk>w ; but it has been found in practice that these arrangements are liable to derangement, and generally the blast is now shut off and opened by a separate valve, under the control of the same man (vessel-man) who works the mechanism for turning over the converter as required at the commencement and conclusion of the blow. 800. The provision for the removal and renewal of single twyers in the converter bottom from time to time Chap. XXL] THE BESSEMER CONVERTER. 467 has been already noticed; but a further improvement has been introduced and is now generally adopted, of con- structing the bottom of the converter so that not only single twyers, but the entire bottom, can be removed and replaced in about three-quarters of an hour by a new bottom, thus obviating the loss of time from stoppages for the cooling, repair, and heating up again of the bottom, as required with the old or fixed bottoms, after every ten or twelve blows. Without some such means as the present for the removal and replacing rapidly of the old bottom, it would be impossible to obtain the sixty and seventy casts (requiring six new sets of twyers) during the day of twenty-four hours, as has been accomplished in America from a single pair of converters* This arrangement, known as the"Holley movable bottom," further obviates the necessity of running-in slurry or fluid gaiiister, &c., around the joints, with its defect of rendering it possible that a weak spot shall remain around the twyer through which the metal may break out. The Holley bottom (Fig. 91) is previously built up, dried, and then attached to the converter with the assistance of a hydraulic lift (H, Fig. 90), or other equivalent appliance; and the annular irregular space (a, Fig. 91) forming the junction of the bottom with the body of the vessel is inclined roughly at an angle of 45% and is then directly accessible from the outside of the vessel, so that it can be closed perfectly by ramming in plastic cakes of ganister as required, whilst the interior of the vessel still remains red-hot. An old bottom is thus removed and a new one inserted with less than an hour's delay. 801. The converter is lined to a thickness of from 9 to 12 inches with a most refractory lining, (Fig. 91), the material generally employed being a siliceous sandstone or ganister containing from 85 to 90 per cent, of silica, and which occurs below the Coal Measures. The ganister is first coarsely ground, and then is used either alone or in admixture with a little powdered iire-briek ; 468 STEEL AND IRON. [Chap. XXI. these materials are then mixed with a little water and rammed well in between the iron casing of the converter and a wooden model or core having the internal form of the vessel ; or, instead of the whole lining being thus made up of ganister, the vessel is frequently first lined with a single thickness of fire-brick, with a propor- tionate decrease in the thickness of the ganister. For the Fig. 91. Lower Portion of Bes?emer Converter showing Holley's MovaMe Bottom. purpose of lining the vessel, the bottom is removed and the converter is then turned with its mouth downwards, when the mouth of the converter having been closed with a board, and the core or model introduced, the work- man stands upon the top of the core and rams down the ganister with iron rammers around the sides of the core, between it and the external walls of x .he vessel. The ramming being completed, the pattern is withdrawn and the vessel rotated through an angle of 180, when the bottom is refixed, and the whole is then carefully dried end heated up for the reception of the charge. Instead Chap. T.XL] ARRANGEMENT OP BESSEMER PLANT. 469 of mixing the ganister with water in the preparation of the bottoms of the converter, in South Wales tar has been substituted for the water, and this yields, when heated, a non- volatile or fixed infusible cement of solid carbon, which is said to become exceedingly hard on drying, and to resist both chemical action and mechanical abrasion. 802. A single Bessemer plant usually consists of a pair of vessels or converters, generally arranged on opposite sides of a central circular casting-pit; although more recent practice is to place the vessels on the same side of the pit, arranged with their axes parallel to one another or inclined at a slight angle towards the centre; the latter arrangement gives greater space in the casting-pit, whereby a large number of moulds can be fixed at once, and the facilities for an increased output are thus thereby improved. In the centre of the casting-pit is fixed a hydraulic crane consisting of a central cylinder by which it is raised and lowered, and around which it revolves by gearing placed under the command of the workman, who stands on the crane ; to the head of the central hydraulic ram is attached a pair of wrought-iron girders forming a platform, which carries the ladle, a balance for which is provided by a cast-iron counterpoise fixed at the other extremity of the table. The crane, after the ladle has received the charge of molten steel from the converter, is rotated in a horizontal plane over the tops of the moulds around the periphery of the pit, and the tap-hole of the ladle is thus brought successively over the centre of each mould, into which the metal from the ladle is tapped. 803. The gearing for turning over the converter, as also that for rotating and elevating the pit crane, is connected with valves and levers controlled by a man upon an elevated platform outside the casting-pit; but the gearing for moving the ladle in or out from the centre over the several moulds, is worked by a man on the platform of the crane, the same man also controlling the mechanism by which the ladle is finally turned over at 470 STEEL AND IRON. [Char. XXL the close of the casting operation, to discharge the whole of the cinder, slag, &c., from the ladle into the slag-pit. With the arrangement in which the converters are placed side by side instead of opposite to each other, the central crane is made to serve the converters only, whilst two auxiliary but similar hydraulic cranes are fixed at oppo- site corners of the casting-pit, and there receive the ladle with its charge from the central crane and move it over the moulds for .completing the casting operations, and the same cranes subsequently strip the moulds from the ingots, and remove the latter from the pits. 804. Between each pair of converters, but elevated considerably above the floor level, is built a small cupola for melting the spiegel or other manganiferous alloy to be added to the converter at the termination of the blow. This cupola stands so that a movable spout or shoot, D (Fig. 90), of wrought-iron lined with a mixture of ganister and fire-clay, will deliver the necessary spiegeleisen direct from the tap-hole of the cupola to the mouth of the converter, as the latter stands in the horizontal position for receiving the end of the spout; or at other works the spiegeleisen is first run into a ladle suspended upon a suitable weighing machine, and the required weight carefully run into the ladle before it is teemed from the latter into the converter. Also beyond the casting-pit, and at a short distance from the converters, are built the cupolas or other furnaces employed in melting the pig-iron to be run from them along a trough, like that last described, to the mouth of the converters. Formerly, when five or six blows per day only were made, two such cupolas sufficed for a pair of 8-ton converters, but more recently four large cupolas of 7 feet inside diameter, and 37 feet in height, have been erected to melt the pig-iron for a like pair of converters; while in America, where the most rapid working is made, the furnaces for melting the charge are even more numerous. 805. In England at the Barrow, the West Cumberland Chap. XXI.] FIXED BESSKMER CONVERTER, 471 and other works, and in America at Chicago and else- where, to save the time and expense of remelting the pig- iron, the molten metal is taken direct from the blast furnaces to be charged into the converters. For this pur- pose, at the Barrow works, the metal is tapped from the blast furnace as usual, but instead of running it into pigs it is run across the pig-bed in a sand channel to the boun- dary wall of the pig-bed, over which it falls from a spout into a ladle mounted on a carriage and wheels, standing for its reception in a sunken siding. When the ladle has received sufficient metal for a charge, the stream is stopped or diverted on to the pig-bed, whilst the surface of the molten metal in the ladle is covered with coal-dust, after which the ladle and contents are taken to an elevated siding, whence the metal can be dis- charged directly into the mouth of the converter. For ensuring greater uniformity in the composition of the charges, the metal for each charge is taken from several blast furnaces ; and at Barrow the fluid pig-iron is conveyed upwards of a mile from the blast furnace to the converters ; but at other works more complete and elaborate arrangements have been made for taking the metal direct from the blast furnaces. In Belgium, the metal for supplying a pair of 6- ton con- verters is taken direct from four furnaces from which the pig-iron is first run into ladles, which are then raised by an hydraulic lift as shown at L (Fig. 90), to the mouth of the converters where their contents are emptied into the vessels; but in order to keep up the continuous supply of molten pig necessary to get thirty casts per shift of twelve hours from the one pair of con- verters, two cupolas are also built in connection with the plant, and these supply 60 or 70 tons of metal per shift, which is run into the ladles as before, and elevated to the converter mouth in like manner. 806. The fixed Bessemer vessel, or converter, of a casing of wrought-iron plates riveted together and provided with a spout at one side for receiving the 472 STEEL AND IRON. fCtap. XXI. molten metal of the charge, while the vessel is sur- mounted by a hood or dome for the escape of the gases. The casing is lined with fire-brick, whilst arranged in a circle around the bottom of the apparatus is a series of perforated clay twyers, and at the bottom cf the vessel also is a tap-bole for drawing off the charge at the end of the blow. The tap-hole is closed during Ihe blow by a suitable stopper, with a similar arrangement to that named above ( 796) for closing the twyers. 807. The ladle (Fig. 92) employed for receiving the steel from the converters, and conveying it to the moulds, is constructed of iron plates riveted together, like an ordinary foundry ladle, except that instead of the metal being poured from a lip in the side of the ladle, the lining of the Bes- semer ladle slopes from all parts of the bottom towards the one point where the tap-hole, a, is situate. The tap-hole is closed OT p en f d b ? a , fir r cla y *pp e r Ladle. or nozzle, attached to the end of an iron rod, 6, coated with clay, and which bends over and downwards over the top edge of the ladle in the manner shown, so that by connecting this rod or goose-neck with a suitable lever, the stopper can be raised or depressed for letting out or stopping the flow of metal from the ladle into the several moulds, over which the ladle is placed in succession, and into which the charge is to be cast. Care is taken during the casting that the metal does not wash the sides of the mould in its descent to the bottom, or otherwise unsound and sticking ingots frequently result. The ladle is suspended as already 'described, upon the two girders, c, connected to the head of the hydraulic pit-crane, and is provided with a worm and worm-wheel arrangement, c?, for tipping the ladle over and emptying out the slag after the whole of the metal has been run into the moulds. Chap. XXI.J BESSEMER INGOT MOULDS. 47-3 808. The ladle is lined with a refractory material such as sand or ganister, having the same or a similar composi- tion to that of the lining of the converters. Where the metal is taken direct from the blast furnace, and very rapid working is aimed at, as many as fourteen ladles are sometimes prepared for a single Bessemer casting-pit, so that there may be always one or more ladles dry and in readiness, although for ordinary working four or six ladles will suffice for one pit. The ladles and stoppers are carefully dried and heated before running the steel from the converter into them. 809. The moulds in which Bessemer steel ingots are cast are usually of cast-iron, open at both ends, and are frequently octagonal or circular but more generally square in transverse section ; and the moulds are made with a considerable taper from top to bottom, so as to allow of their readily stripping from the ingots shortly after cast- ing the metal within them. While the more usual practice is to fill each mould separately, and to run in the steel from the top, yet casting in groups is also frequently pursued ; for this purpose several moulds are arranged around a central one somewhat taller than the others, and into which the rnetal is run at the top, whilst by an arrangement of fire-clay tubes or passages leading from the bottom of the central or feeding ingot, and open- ing upwards into each of the other moulds of the group, all the moulds of the groups except the central ones are filled from the bottom, the steel gradually rising upwards to the required level. In every case the ingots are properly stoppered down, by throwing a shovelful of sand into the mould on the top of the still fluid metal, and then covering it with an iron plate fastened down by a cross-bar passing over the top of the plate and wedged down by wedges passing through eyes fixed for the purpose in the top of each mould. Ingots for rails are about ll^ inches square, and are, when the group system is adopted, for the most part cast in groups of sixteen at once, for which purpose the bottom on which the moulds 474 STEEL AND IROX. [Chap. XXI are placed consists of a cast-iron slab or plate having the curve of the pit, and is about 13 feet long by 3 feet wide, with a recess in the middle of about 6 inches square and 3 inches deep for the reception of a brick, over which the central mould is fixed, the other moulds being arranged in a double row of four moulds each on either side of the central one, whilst channels or runners of fire-brick are made in either side of this central mould with sixteen branches opening upwards each into its own mould, and whereby the sixteen moulds are all cast at the same time, and each is run from the bottom. 810. For the conduct of the Bessemer process the converter or vessel, if not already strongly heated from the blowing of a previous charge, is dried and heated by first making within the vessel a fire of wood, to which coke is then added and a gentle blast turned on. This is con- tinued until the lining has become thoroughly dry and has attained to a red heat, upon which the vessel is turned with its mouth downwards for the emptying out of the coke, the same being completely expelled from the converter by passing a strong current of blast through the vessel for a few seconds. The heated converter is then placed in the horizontal position (as shown in Fig. 90) for the reception of its charge of from 5 to 15 tons (according to the size of the converter) of molten pig- iron, which is delivered along a suitable clay-lined movable wrought-iron channel or trough D, into the mouth of the converter. The molten pig-iron is either delivered from the cupola in which it has been re-melted, or the charge is received direct from the blast furnace in the manner already described. The form of the converter when it stands in the horizontal position, permits of the charge lying in the hollow of the side of the vessel without reaching to the level of the twyers, and in addition to the pig-iron it is also not unusual to throw into the converter 10 or 12 per cent, of the charge in the form of scrap, consisting of rail ends, shearings, and various steel croppings, which Chap. XXIJ THE BESSEMER BLOW. 475 are added before the introduction of the molten pig- iron. The vessel, thus charged, is turned up into the vertical position, after first turning on the blast to prevent the metal from passing into the twyers, since, if this is per- mitted to occur, it would partially or completely close the twyers, and so obstruct the passage of the blast. 811. During the passage of the vessel from the horizontal to the vertical position showers of sparks and burning graphite are ejected from the mouth of the con- verter, and for the first three or five minutes of the blow the flame from the mouth of the converter has a faint yellowish-red colour, is small in volume, very slightly luminous, and is accompanied by sparks, and these phenomena continue during the first stage of the blow which corresponds to the first step in the puddling process and during which the graphitic carbon passes into the dissolved or combined form, while the silicon also is being oxidised to form silica, which combines with ferrous and manganous oxides yielding slags of the silicates of iron and manganese. The temperature of the molten charge at the same time rapidly rises throughout this period, while the flame, which was more or less un- steady during the first stage, gradually increases in volume and luminosity, until in the second stage or "boil," lasting from six to ten minutes, it acquires a dense yellow colour, is very brilliant, and of very greatly increased volume, whilst frequently repeated ejectments of slag and sparks of burning iron are also thrown from the mouth of the converter. During this stage the metal is in a state of violent ebullition, and carbonic oxide is being evolved in large quantities from the oxidation of the car- bon in the pig-iron by the oxygen of the blast, whilst the pressure of the blast, which at the commencement of the blow was from 20 to 25 Ibs. per square inch, falls during the boil to from 15 to 20 Ibs. per square inch. The boil is succeeded by the third or "fining " stage, which is characterised by the diminished volume, greater 476 STEEL AND IRON. [Chap. XXI. transparency, less brilliancy, and pale rosy or amethyst tint of the flame, with fewer and less violent ejectments of sparks, &c., from the converter mouth. In from eighteen minutes to twenty minutes from the commencement of the blow with an 8-ton charge, the " flame drops/' or sud- denly shortens, indicating the almost total decarburisation of the charge and the conclusion of the blow, upon which appearance the converter is rapidly turned down into the horizontal position and the blast shut off, any further continuation of the blow beyond this point being attended with oxidation, waste of iron, and deterioration of the product. From 7 to 10 per cent, of molten spiegeleisen, or a smaller proportion of ferromanganese, according to the temper of steel to be produced, is then run into the converter either from the ladle in which the alloy has been weighed, or direct from the small cupola already named, and in the same manner as the original charge of pig -iron was introduced. The introduction of the spiegel- eisen is always attended by a violent reaction within the converter and the emission from the mouth of a long lumi- nous and roaring jet of flame, the appearance of which indi- cates that the blow was fully completed before the con- verter was turned over ; since, if the metal be much under- blown, the flame on the addition of the spiegeleisen does not appear, or is very small and feeble, owing to the small reaction induced by the spiegeleisen under this condition. 812. Formerly it was the practice to turn up the converter, and continue the blow for a few seconds after the addition of the spiegeleisen, but latterly this course has been discontinued, and the metal, after standing for a few minutes in the converter for the completion of all re- action following the addition of the spiegel or ferroman- ganese, and also to allow of the escape of gas and the separation of slag from the metal, is then poured from the mouth of the vessel into the ladle, sufficient slag being at the same time poured into the ladle to cover the sur- face of the fluid steel and retain the heat therein. The lining of the ladle is also heated to redness by burning Chap. Z.XI.] THE BESSEMER PROCESS. 477 a coal or coke fire within the ladle, previous to the pour- ing of the steel into it. When the whole of the metal has been discharged from the converter, the ladle, which has in the meantime been standing on the central lift or crane of the casting-pit, is turned round from beneath the converter, and carried over the several moulds, when casting of the metal into ingots proceeds as already de- scribed. After the withdrawal of the ladle from beneath the mouth of the converter, the latter is turned right down, and the residue of the slag, with any detached ganister from the lining, &c., of the inside of the vessel, is discharged into the slag-pit beneath the converter, its more complete expulsion being effected by blowing a strong blast of air through the vessel for a few seconds. 813. The ordinary Bessemer blow in the ganister or acid-lined converter thus occupies from fifteen to twenty minutes for the conversion of 8-ton charges of English haematite ; but with Swedish pig-iron the proportion of impurities, especially the silicon, is lower, and the con- version is accordingly much quicker, although it requires greater care and experience in its conduct to prevent over- blowing, that is, blowing after the point of total decar- burisation has been attained, for if this occurs then con- siderable loss and difficulty arise from the coating of the vessel and ladle with a firmly adhering coating or "skull" of metal. Swedish haematites, besides being lower in silicon are also richer in manganese than the English, and in the treatment of Swedish pig in the Bessemer con- verter, the boil commences earlier than with the English irons, and a larger amount of the brown vapours or smoke ascends from the mouth of the vessel during the earlier stages of the blow than occurs in the corresponding period of a blow in which English haematites are under operation. 814. The method, as described above, for the conduct of the Bessemer process thus consists in continuing the blow or current of blast, until almost complete decarburi- sation of the metal within the converter is attained, and 478 STEEL AND IRON. [Chap. XXL then restoring the necessary amount of carbon required for the conversion of the charge into steel of the desired hardness or temper by the addition of spiegeleisen, or other highly manganiferous alloy. It has also been pro- posed to attain the .desired degree of carburisation in the finished product by arresting the blow at the proper point before total decarburisation is reached ; but this method, which was formerly used in Sweden, is not pursued in England, and the first-named method is generally adopted as affording less practical difficulty in its conduct, while also yielding more certain and uniform results. In Austria and Sweden also a " slag test," as described (p. 485), is adopted for the determination of the end of the blow, instead of watching for the dropping of the flame as last described. 815. The result of the reactions in the Bessemer con- verter is essentially the same as that occurring in the puddling or in the refining process, except as regards sulphur, phosphorus, and copper, which in the siliceous or acid-lined converter are not eliminated or diminished. In the Bessemer process the silicon of the pig-iron first suffers combustion and oxidation under the influence of the oxygen of the blast, with the formation of silica which immediately unites with ferrous and manganous oxides, yielding a siliceous slag which floats above the molten metal ; and, as shown in the following analyses (published respectively by the authorities of the Neuberg Works in Styria, and by Mr. Snelus when at the Dowlais Works) of the pig-iron employed, and of the condition of the charge at different periods of the process, it appears that the manganese is also oxidised rapidly, and that the iron does not oxidise to any appreciable extent until the silicon, manganese, and carbon have been almost entirely removed. If the blast be continued after the carbon has been eliminated, then the iron suffers oxidation and waste, and the overblown m&tol so produced, if examined, is found to possess the usual qualities of rottenness, &c., charac- teristic of burnt iron. A.S will subsequently appear when Chap. XXI. J ANALYSES OF BESSEMER PRODUCTS. 479 ANALYSES OF PIG-IRON, AND OF THE BESSEMER CHARGE AT DIFFERENT PERIODS OF THE BLOW IN THE NEUBERG WORKS. Grey pig-iron smelted with char- coal from spathic Metal at the end of the first stage of the blow. Metal towards the end of the boil. Metal before the addition of spiegel- eisen. Final product of mild steel. m 'ii-ores. Graphite 3-180 _ Combined ) carbon ) 0-750 2-465 0-949 0-087 0-234 Silicon . 1-960 0-443 0-112 0-028 . 0-033 Phosphorus . o-o to 0-040 0-045 0-045 0-044 Sulphur 0-018 trace trace trace trace Manganese . 3-460 1-645 0-429 0-113 0-139 Copper . , 0-080 0-091 0-095 0-120 0-105 Iron . '. 90-501 95-316 98-370 99-607 99-445 99-989 100-000 100-000 100-000 100-000 ANALYSES OF THE PIG-IRON AND OF THE BESSEMER CHARGE AT DIFFERENT STAGES OF THE BLOW, &c., AS PRODUCED IN THE DOWLAIS WORKS.* Metal ; Metal at Melted pig-iron irom the con- c, ' blow and Steel Steel as charged into the con- verter. verter at the end of the first stage of the blow. alter blowing for 9 minutes. before the addi- tion of spiegel- eisea. from the cast ingot. from ths rolled raiL Graphitic \ carbon } 2-070 Combined ) carbon \ 1-200 2-170 1-550 0-097 0-566 0-519 Silicon . 1-952 0-790 0-635 0-020 0-030 0-030 Sulphur 0-014 trace trace trace trace trace Phosphorus . 0-048 0-051 0-064 0-067 0-055 0-053 Manganese . 0-086 trace trace trace 0-309 0-309 Copper . 0-039 0-039 Mr. Snelus, Iron and Steel Institute. 480 STEEL AND IRON. [Chap. XXI. treating of the basic process, similar deterioration and waste of iron do not result from the short overblow in the treatment of phosphoric pig-iron in a basic-lined con- verter, since with the basic lining the combustion in the overblow is maintained largely at the expense of the phosphorus, while with the acid or ganister lining this oxidation of phosphorus is impossible. 816. The intense heat produced during 1 the Bessemer blow is principally due to the high calorific power and extreme rapidity with which the combustion and oxida- tion of the silicon of the pig-iron to the condition of silica are effected. Silicon generates, during its combustion to silica, 7,830 units of heat (centigrade). Manganese also probably acts a like part as a generator of heat, and may thus partially replace the silicon in the pig-iron required for the Bessemer process, while carbon, although developing considerable heat by its combustion * and oxidation, produces gaseous carbonic oxide as the result of its combustion in the Bessemer converter, and this gas absorbs a large proportion of the heat so generated, and is thus largely carried away from the mouth of the con- verter without being utilised. If the blow be continued beyond the point of total decarburisation, then the heat is afterwards largely maintained by the oxidation and waste of iron, and this waste always occurs more or less towards the end of the blow. A large excess of oxygen is also left in the metal at the close of the blow which seriously affects the malleability unless sufficient manga- nese in the form of spiegeleisen or of ferromanganese, is added, to combine with this excess of oxygen, and so pass it out into the slag ; and the special use of ferroman- ganese instead of spiegeleisen is to enable sufficient manganese to be thus introduced into the metal for the removal of the oxygen without at the same time adding so much carbon and silicon as to render the metal hard. The metal at the end of the blow, before any addition of spiegel- eisen or ferromanganese has been made, resembles burnt * Greenwood : " Manual of Metallurgy," Part L Chap. XXI.] THE BESSEMER PROCESS. 481 iron in its behaviour. It is red-short, unweldable, un- forgeable at a red heat, crumbles and falls into powder under the hammer, and is altogether rotten and wanting in cohesion, owing to the presence of surplus oxygen and silicon in the metal j but these elements are removed and the malleability, &c., of the metal restored as just noted, by the use of manganese alloys, while the temper or hard- ness of the resulting steel depends largely upon the amount of carbon introduced in the spiegeleisen or other manganiferous alloy employed. 817. Silicon is thus essential as a heat producer for the successful conduct of the ordinary Bessemer process, and should be present to the extent of about 2J per cent, in the pig-iron applied to Bessemer use, yet any considerable excess of this element is a source of trouble, since the silica (Si0 2 ) produced by its combustion combines with ferrous oxide, thus increasing the proportion of slag in the converter and loss of iron in the process. It may also become difficult to completely remove the whole of the silicon before the metal has reached the degree of decar- burisation requiring the stoppage of the blow, for the analyses (p. 479) show that the carbon and silicon are being simultaneously eliminated during the Bessemer conver- sion, and it is possible therefore sufficient silicon may re- main in the metal to induce hardness, brittleness, and an inferior quality of steel after the carbon has been wholly removed, and it is thus usual to consider that the propor- tion of silicon in the pig-iron for this process should not exceed that of the carbon. But, as just stated, a deficiency of silicon also results in a cold-blow and inferior metal, whilst practical difficulties arise at the same time from the formation of skulls in the ladle and converter. Thus, since haematite pig-iron by remelting in the cupola usually loses about 1 per cent, of its silicon, it follows that with pig-irons such as certain varieties of those occurring in the South of France, &c., which contain the minimum of silicon required for the Bessemer process, they cannot, accordingly, be worked with any success after F F 482 STEEL AND IRON. [Chap. X*J they have been mnelted in the cupola, although they work well if conveyed direct from the blast furnace to the converter. 818. The pig-iron required for the original Bessemer process is therefore of a special character, and the demands 01 the trade have thus produced in the market a special quality of haematite grey pig known as No. 1, No. 2, and No. 3 Bessemer pig-iron, indicating that such metal is of a quality adapted to the requirements of the Bessemer and other steel-making processes. Bessemer pig-iron is smelted from Cumberland or other haematite iron ores, and it contains at least 2 per cent, of silicon with not more than O'l per cent, of phosphorus; or for special qualities, as for plates, &c., the phosphorus should not exceed '04 per cent. Such pig-iron is also required to be grey, since the use of white iron is attended with a greater loss of iron, whilst also the com- bined carbon in white iron passes into carbonic oxide in the earlier stages of the blow, before the necessary heat of the metal has been attained and the combustion of the silicon effected. Bessemer pig-iron is also almost free from sulphur and copper, since but very small quantities of these elements exercise an injurious effect upon the finished steel, and their proportion is not reduced during the conduct of the Bessemer process. The average quality of Bessemer pig will contain from 3*5 to > per cent, of carbon with 2 per cent, of silicon, 1 per cent, of manganese with O04 per cent, of phos- phorus, and 0-04 per cent, of sulphur. The presence of manganese within certain limits is also desirable, since it acts as a heat producer in the Bessemer converter and combines with the excess of oxygen blown into the vessel, while its oxide unites readily with the silica resulting from the oxidation of the silicon, producing thereby readily fusible slags or silicates, which are how- ever highly corrosive in their action upon the siliceous lining of the converter ; but the oxidation and waste of iron from the action of the blast, and the deterioration Chap. XXI.] BESSEMER SLAGS. 483 in the quality of the steel owing to the presence of ferrous oxide or of an excess of oxygen in the metal, are exceedingly limited, so long as there remains any unoxidised manganese in the charge. The pig-iron smelted from spathic ores sometimes contains the required proportions of silicon and manganese, and is sufficiently free from sulphur and phosphorus to be available, as in Westphalia, for the Bessemer process ; but such pig-iron usually contains more copper than is present in the haematite irons ; and thus, whilst English Bessemer steel contains only the small proportion of copper introduced into it by the addition of spiegeleisen or of ferromanganese at the end of the blow, the con- tinental Bessemer steels, such as those of Neuberg, c., frequently contain also small proportions of copper de- rived from the use of pig-iron which has been smelted from spathic ores. The pig-iroA employed in Westphalia is gmelted from a mixture of haematite and spathic ores. ANALYSES OF BESSEMER PIG-IRON. No. 2 Grey Bessemer (Author). South Wales Haematite (Head). No. 1 Grej Haematite (Author). Carbon, Graphitic . . . Combined . . . Silicon 2-579 1-175 1-758 2-560 0-075 3-650 3-045 0-704 2-003 Sulphur 0-014 0-053 0-008 Phosphorus 0-038 0-130 0-038 0-576 0-037 0-309 Copper . ,-.-, 0-027 819. The slags produced in the Bessemer process differ much, both in composition and appearance, from the corresponding slags of the puddling process ; for whilst the puddl ing-furnace slag or cinder is a well-fused basic ferrous silicate, the Bessemer slag as left in the converter after the pouring out of the fluid metal, and then turned out into the slag-pit beneath the vessel, 13 484 STEEL AND IRON. [Chap. XXV decidedly siliceous or acid in its character, and consists of a heterogeneous, porphyritic-looking, siliceous mix- ture, consisting of a well-fused portion of slag proper, cementing together considerable quantities of apparently unfused quartzose or siliceous matters detached from the sides and bottom of the converter during the blow. The composition of the slag, taken as a whole, is accordingly exceedingly varied ; but the analyses and appearance of the fused portion, taken at the several periods of the blow, afford some evidence of the progress and condition of the blow at the corre- sponding stages ; so much so that in Austria and Sweden a slag-test has been proposed and used for the determina- tion of the point of decarburisation at which the blow is to be stopped. Agreeably with previous conclusions, the tabulated analyses below indicate that during the first and second stages of the process and until near the end of the boil, the silicon and manganese are being rapidly oxidised and removed with the formation of fusible sili- cates, whilst the iron during the same period is but little affected; but in the short period of the fining stage between the end of the boil and the conclusion of the ANALYSES or SLAG FROM THE GANISTER BESSEMER CONVERTER. Slag taken at end of the first period of the blow (Snelus). Slag taken at end of the boil (Snelus). Slag taken at end of blow before the addi- tion of spie- geleisen (Snelus). Slag taken after the addition of spie- geleisen (Snelus). Siliceous mixture as emptied from thfc converter at the end of the blow Silica . 46-78 51-75 46-75 47-27 72-25 Alumina 4-65 2-98 2-80 3-45 2-43 Ferrous oxide 6-78 5-58 16-86 15-43 20-65 Manganous , 37-00 37-90 32-23 31-89 2-95 Lime . 2-98 1-76 1-19 1-23 1-04 Magnesia 1-53 0-45 0-52 0-61 0-13 Alkalies trace trace trace tiace Sulphur 0-04 trace trace 0-86 Phosphorus 0-03 0-01 o-oi o-oi trace Chap. XXI.] GASES FROM THE BESSEMER CONVERTER. 485 blow the iron sutlers combustion, so that the slag, examined just before the addition of the spiegeleisen, shows a large increase in the proportion of ferrous oxide. 820. The slag test, noted above as having been in use in Austria and Sweden, is made by introducing an iron rod into the slag in the converter, upon withdrawing which a specimen of the slag adheres to the rod, and presents different appearances according to the degree of decarburisation attained by the metal in the bath. The slag always presents a peculiar brownish tint so long as the metal retains any carbon, whilst it becomes totally black, with the lustre characteristic of the presence of ferrous oxide, immediately the whole of the carbon is removed from the metal in the converter, and the various intermediate percentages of carbon are indicated by corresponding tints of the slag; thus, 0*75 per cent, of carbon in the charge is indicated by a lemon-yellow coloured slag, which changes to orange as the carbon falls to 0*60 per cent, becoming light-brown with a content of Q'45 per cent, of carbon, while 0'30 per cent, of carbon is indicated by a dark-brown colour, and (H5 per cent, by a bluish-black slag. 821. The gases escaping from the mouth of the Bessemer converter, as shown by the accompanying results obtained from a blow of eighteen minutes' duration, indicate that at the commencement of the blow when the temperature is low and the flame is only slightly luminous, the carbon of the metal is being burnt to carbonic anhydride (C0 2 ), with an entire absence of carbonic oxide (CO) ; but after an interval of only two minutes the proportion of carbonic anhydride has begun to decrease, and carbonic oxide then forms a sensible proportion of the escaping gases. The propor- tion of carbonic oxide to carbonic anhydride in the gases escaping from the mouth of the converter, con- tinues to increase as the temperature within the con- verter rises. During the boil, or from ten to fourteen minutes from the commencement of the blow, when a 486 STEEL AND IRON. [Chap. XXL very high temperature prevails in the converter, and a large luminous flame issues from the mouth of the vessel, there is a most notable increase in the proportion of carbonic oxide, whilst towards the end of the blow the name assumes a red dish- violet tinge from the combustion of carbonic oxide at the mouth of the converter, and there is then an almost entire absence of carbonic anhydride in the escaping gases, until, finally, when the blow is over, and the limit of decarburisation is attained, the flame of carbonic oxide is succeeded by a stream of white-hot gas consisting largely of nitrogen. ANALYSES OF THE GASES FROM THE MOUTH OF THE BESSEMER CONVERTER. Time after commencement of blow.* After addition i! H| | IJ A 83 1 Ten minutes Twelve minutes Fourteel minutes. of Spiegeleisen at Bochum Works. Carbonic anhydride 1071 8-sy 8-20 3'58 2-30 1-34 0'86 Carbonic oxide . . None. 3-95 4-52 19-59 29-30 3111 82-6 78-55 Oxygen . . . . 0-92 132 Hydrogen. . . ) Nitrogen . . . ) 88-37 088 86-58 2-00 85-28 2-00 2-16 74 83 ; 66-24 2-00 65-55 2-8 14-3 2-52 163$ 822. Carbonic oxide is more stable at very elevated temperatures when in contact with metallic iron, than is carbonic anhydride under like conditions, t and it is suggested that this may account for the fact that whilst carbonic anhydride is present in the earlier and cooler periods of the Bessemer blow, yet it is almost entirely replaced by carbonic oxide at the higher temperature attained during the boil and at the end of the blow. 823. The temperature of the flame and of the escap- ing gases from the Bessemer converter at any period of the blow falls below that required to melt a wire of pla- tinum or of an alloy of platinum and iridium, when the * Snelus. Iron and Steel Institute. f Experiments of J. S. Bell, Esq. Thap. XXI.] OUTPUT OF BESSEMER WORKS. 487 sam-e is held within the flame ; whilst a wire of gold is always melted during the boil or towards 'the end of the blow ;* hence, since the melting-point of gold is about 1,300 C., and taking the melting-point of platinum as 2,000 C., it follows that the temperature of the flames rises to a point exceeding 1,300 C., but never attains to 2,000 C. 824. The rapidity of conversion, small amount of labour and extraordinary output of a Bessemer plant, contrast strongly with the old puddling operations. The fining of an amount of pig-iron which would occupy in the puddling furnace with its small charges, from two and a half to three days for its completion, is effected in a single Bessemer blow, lasting only about twenty minutes ; whilst in America sixty or seventy of such charges, ave- raging 8 tons each, are regularly made from a single pair of converters during the twenty-four hours, and as much as 2,830 tonst of steel have been produced in one week from such a pair of vessels ; but, generally, in England the output although very great, falls considerably short of these figures. These largely increased outputs are attributable to a great increase in the number of cupolas employed in melting the pig-iron, or where the metal is taken direct from the blast furnace, to the saving of the time required for remelting the pig-iron, as by these means it is possible to always keep in blast one or other of the converters in each pair ; also, further, greater rapidity of work has resulted from the general introduction of the method of more quickly replacing the twyers, converter bottoms, and of repairing the lining of the vessels upon the method introduced by Mr. Holley (p. 468) ; and lastly, the output has been increased by the better facilities and greater space afforded for placing, tilling, and removing the ingots and moulds by arranging the two converters on the same side of the casting-pit instead of upon opposite sides of it, and at the same time increasing the number of cranes * Dr. W. M. Watts. + Windsor Richards, Cleveland Institute of Engineers, 1880-1. 488 STEEL AND IROX. {Cbap. XXI. available for fixing the moulds and clearing away the ingots, &c., from the pit. The importance and saving of time to be effected by the adoption of a ready method of changing the bottoms of the converters is obvious, when it is considered that after every ten or twenty blows, and sometimes after even less than this, the converter bottom requires complete renewal, and before this occurs from twelve to twenty twyers will have been replaced by new ones ; so that whilst the actual Bessemer blow lastfi only from fifteen to twenty minutes, according to the class of pig-iron under treatment, yet the repairs to the converters, clearing the casting-pits of ingots, &c. t replacing of moulds, and other preliminary operations, occupy by far the largest proportion of the time of the workmen. 825. After every eighty or ninety blows the con- verter requires thoroughly relining, the vessel having in the meantime been frequently partially repaired by ramming on patches of ganister upon the more corroded parts of the lining. To obviate the considerable loss of time necessitated by a stoppage for the relining, drying, and warming-up of a converter, a method of construction has been proposed by Mr. Holley, but as yet only partially adopted, whereby the body of the converter is made loose from the trunnion ring, to which it is secured during the working by wrought-iron knees and cotters, so arranged as to permit of their ready removal. Thus whilst the vessel rests securely upon the trunnion ring during the conduct of the blow, &c., yet by turning the vessel mouth downwards it is readily disconnected from the trunnion ring by removing the above-named cotters, and the body of the vessel is then received upon a bogie carried by the table of an hydraulic lift, H (Fig. 90), fixed below, and by lowering which, the converter freed from the trunnion ring as above is lowered bodily from its position, and so re- moved. By a reverse order of the movements a fresh vessel can be inserted and secured in position, so that by keeping extra vessels ready lined and dried the delay from Chap. XXL] BESSEMER BLOWING ENGINES. 489 this cause is considerably reduced. Instead of the hydraulic lift and removal from below, in the manner just described, at Eston, for the removal of the basic-lined converters to be subsequently described, a 60-ton overhead travelling crane is arranged so as to lift the converter upwards from the trunnion ring and carry it away to a suitable carriage, whilst a fresh con- verter is, in the same manner, introduced from above. 826. The blowing engines employed for delivering the blast to the converters at a pressure of from 20 to 25 Ibs. per square inch are of various types, vertical and horizontal, compound, non - condensing or condensing ; but the consideration of the details of such en- gines would be too long for the present volume, and it must suffice to say that in the more recent com- pound types the high and low-pressure cy- linders, A and B re- spectively (Fig. 93), are made with steam cylinders of 36 inches and 60 inches in dia- Fig> 93 ._ Elevation of vertical Compoimd meter respectively, Bessemer Blowing Engines. with blowing cylin- ders, c, c, each of 48 inches in diameter, and having a 490 STEEL AND IRON. [Chap. XXI. uniform stroke of 5 feet. Other engines have been made, however, a little larger in size, in which the high-pressure steam cylinder measures 42 inches in diameter, whilst the low-pressure cylinder is 78 inches in diameter, and the air or blowing cylinders for^such engines are each of 54 inches diameter, all having, as before, a stroke of 5 feet. The engines (Fig. 93) have piston inlet valves, a, a, open- to the air cylinders, c, c, and have several small circular wrought-iron valves, b, b, b, b, working automatically for the delivery of the blast to the blast main. With the last-mentioned engines a boiler pressure of 90 Ibs. to the square inch is sufficient to give the required pressure of 25 or 30 Ibs. to the blast delivered to the converters. The steam cylinders are also jacketed, and the high-pressure steam cylinder is fitted with expansion-slides on the back of the main slide-valve, while the low-pressure cylinder is fitted with piston valves. APPLICATION OF THE SPECTROSCOPE TO THE BESSEMER PROCESS. 827. The spectroscope has been applied successfully to the analysis of the flame issuing from the mouth of the Bessemer vessel, and for the determination accordingly of the proper moment at which to turn down the con- verter and stop the blow ; but the conclusion of the blow is of such easy practical determination to the practised Bessemer man that the use of the spectroscope in the regular conduct of the process has not been extensive, and in England it is now generally discarded, although on the Continent, where irons less siliceous than the English haematites are employed, the termination of the blow is not so decisively marked, and the instrument is still in occasional use. The principal phenomena observed at different periods of a blow lasting twenty- four minutes, as seen simultaneously by the naked eye and through the spectroscope, are herewith tabiilated. Chap. XXI.] SPECTRA OF CONVERTER FLAMES. 491 PHENOMENA OBSERVED BY APPLICATION ov SPECTROSCOPE TC BESSEMER PROCESS. Time from the commencement of the blow. Appearances presented to the naked eye. Appearance of the spectrum. 4 minutes Very small flame with Faint continuous spectrum. sparks of metal 5 Flame pale, but in- Continuous spectrum, with creasing in size two yellow sodium lines flashing across it. 6 Large unsteady flame Sodium lines steady and fixed. 8 n Flame brighter and Yellow sodium lines, with larger lines also in the red and violet bands, appear. 10 Boil commenced ac- Spectrum as the last, but companied by with additional lines ap- bright dense flame pearing in the red, with car- bon lines in the green and blue, and other mangan- ese lines also in the green. 15 Flame becomes larger Spectrum more distinct, and and more trans- the lines better defined. parent JO Less luminous and Spectrum as before, but diminishing volume fading in intensity. of flame 24 Flame drops Green lines in the carbon and manganese bands disap- pear. With less siliceous and more manganiferous irons, such as those of Sweden and the Continent, the spectrum is more obscured and less distinct from the larger proportion of brown fumes escaping from the mouth of the converter ; with s\:ch pig-irons the boil also commences earlier than the above, and the yellow line of the spectrum flashes in about thirty seconds from the commencement of the blow, becom- ing steady and fixed in from one to one and a half minutes. The other appearances occur in regular sequence, as tabu- lated above, but the intervals between the several periods are less, and the blow terminates some minutes earlier. 492 STEEL AND IRON. [Chap. XAL THE BASIC PROCESS OF MESSRS. THOMAS AND OILCHRIST FOR THE CONVERSION OF PHOSPHORIC PIG-IRON INTO STEEL IN THE BESSEMER CONVERTER. 828. The pig-iron used in the ordinary Bessemer or acid process as last described, requires to be practically free from phosphorus, which renders pig-irons other than those smelted from haematite iron ores, unavailable for the production of steel in the Bessemer converter ; but by the process introduced by Messrs. Thomas and Gilchrist, and known generally as the " dephosphorisation or basic pro- cess," the phosphoric pig-irons, smelted from the spathic and less pure ores of the Cleveland district of England, as also the similar brands of pig-iron rich in phosphorus smelted on the Continent, are rendered available for the production of steel in a modified Bessemer converter or in other steel-producing furnace. Hence the steel-producing processes, as conducted in the Bessemer converter or in the open-hearth furnace of Sir W. Siemens, are divisible into two classes ; the one is conducted in acid-(siliceous) lined vessels or furnaces, in which only the purer kinds of pig-iron can be operated upon, and the second is con- ducted in similar vessels or furnaces, but with basic linings, which are capable of using the more impure phos- phoric pig-irons. The first-named methods constitute the regular Bessemer and open-hearth processes described in the previous pages, and we shall now proceed to describe the processes for the conversion into steel of pig-iron containing considerable proportions of phosphorus, after she manner now regularly pursued at Estoii and else- where in England, as also in Westphalia, Germany, Belgium, and France, where, from pig-iron containing on an average, as at Creusot,* 3 per cent, of carbon, 1 '3 per cent, of silicon, from 1 -5 to 2 per cent, of man- ganese, from 2-5 to 3 per cent, of phosphorus, and - 2 per cent, of sulphur, steel is produced suitable for rails, yielding 0'43 per cent, of carbon, with a trace only of * Annalcs des Mines. Chap. XXI. J BASIC BESSEMER PROCESS. 493 silicon, - 76 per cent, of manganese, 0'06 per cent, of phosphorus, and 0'02 per cent, of sulphur. 829. The basic process is conducted in a plant, ar- ranged after the manner employed for the usual Bessemer process ; but the application of loose bottoms and inter- changeable converters named in the previous pages are of still greater importance in the conduct of this than in the ordinary process, owing to the much greater destruction of the lining of the vessel in the basic process, together with the difficulty of clearing the vessel of the hard and tough slag which accumulates within it at each blow, and which thus necessitates much moro frequent stoppages for repair than occurs with the or- dinary Bessemer process. 830. The converters employed in the basic process are generally shorter and wider than the ordinary acid- (ganis- ter)- lined vessels, and the neck or throat, gr, instead of being fixed at an inclination, is con- centric (Fig. 94) with the body of the vessel, so that the metal can be received by and poured from the converter with equal facility upon either side of the axis of the trunnions whereby the duration of the lining is prolonged. The basic process is, however, fre- quently conducted in the ordinary Bessemer converter and plant, with the sub- stitution of a basic (dolomitic) lining for the ordinary * Proceedings of Inst. Civil Engineers, 1881. Fig. 94. 10-ton Converter employed In the Basic Bessemer Process.* 4^4 STEEL AND IKON. |Cbap. XXI. ganister lining. The 10-ton vessel (Fig. 94) constructed specially for the basic process is made in four parts, connected by bolts and cotters for ready detachment ; the trunnion belt, a, and the arms, b, b, are of cast-iron, made in two pieces of box section, while the body is made of 1-inch wrought-iron plates riveted together and strengthened by strong straps. The trunnions are 15 inches in length and 21 inches in diameter, while the vessel itself measures 10 feet 8 inches across the trunnion belt. The tipping gear is attached to the trunnion arm as usual, and consists of a worm-wheel, c, 8 feet in diameter, gearing with a screw, d, of 4j-inch pitch, the latter receiving its motion in this case direct from the cranks of a pair of double-acting hydraulic engines, e, fixed on the standards of the converter, and the vessel is thereby capable of rotation through a complete circle, or 360 in either direction, the movement being controlled as in the ordinary process, by the man on the stage or pulpit outside the casting-pit. Converters of this class for the treatment of 15-ton charges measure 24 feet 5 inches in height, with an internal diameter of 1 feet 8 inches, and weighing when lined ready for work, from 60 to 80 tons. The arrangement of casting-pit, and of the cranes for working the pit, do not differ from the most recent of the ordinary Bessemer arrange- ments. 831. The great desideratum for the success of the basic process is the preparation of a lining which/ whilst being strongly basic, shall resist the excessively high tempera- ture attained during the blowing of the metal, without softening or melting; and the material generally applied for this purpose is dolomite or magnesian limestone, either made into bricks and laid in a cement of anhydrous tar, or the strongly burnt and ground dolomite is rammed into the vessel along with tar as the cementing material. But with a process whose introduction is so comparatively recent there are, as usual, numerous new proposals for the formation of the lining, but all at present appear to Cliap. XX1.J BASIC-LINED CONVERTER. 495 employ a combination of hard-burnt magiiesian lime- stone (dolomite) and anhydrous tar. 832. Dolomite on heating to whiteness contracts about 50 per cent, of its volume, so that it is necessary to heat the stone or the magnesian bricks, whichever are employed, to a high temperature before introducing them into the converter. The ground and hard-burnt stone, mixed with tar, is more generally employed in England, but in Westphalia and on the Continent the lining of the body of the converter is made of hard-burnt dolomite bricks, set in anhydrous tar asphalte, the bricks having been burnt at an intense white heat so as to be ringing hard, and thus not suffering disintegration by exposure; whilst the tar or cement used for the joints must riot contain water or any appreciable amount of moisture, since steam has a very injurious disintegrating effect upon the lining. The bottom of the vessel is made of considerable thick- ness, measuring about two feet, and it is formed of the same materials as the body lining, viz., burnt or calcined dolomitic limestone and tar, which mixture is rammed well down upon a bottom plate, on which is a number of projecting spikes each about half an inch in diameter, and long enough to reach quite through the finished bottom. These pins, on the withdrawal of the bottom plate, leave holes through the bottom which subsequently act as twyers for the admission of the blast. The magnesite bricks employed contain about 93-85 per cent, of magnesia, with a trace of lime, 1'07 per cent, of ferric oxide, 0'58 per cent, of alumina, and 4-65 per cent, of silica. 833. With the converter illustrated (Fig. 94) the lining has been inserted somewhat differently ; the upper portion or neck of the vessel is movable, and is relined separately, while the body itself may be lined in its place like the ordinary Bessemer converter, except that the core around which the basic lining is rammed is a cast-iron plug of the internal form of the vessel, and which has been heated by a coke fire previous to its insertion into the vessel. Into the space between this core and the old 496 STEEL AND IRON. [Chap. XXL lining a mixture of hard-burnt ground dolomite and tar is rammed, which becomes slightly plastic when heated, and so forms a solid compact mass around the core ; whilst the tar must have been previously boiled to expel all water. The bottom of the vessel is rammed up with a like mixture as last described. During the working of the process the lining of the body oi the vessel is never allowed to wear below 3 or 4 inches in thickness before stopping for thorough repairs. 834. The converter having been suitably lined with basic material and carefully warmed up, the process of conversion is commenced by first introducing into the vessel well-burnt lime, as free as possible from silica, to the extent of from 15 to 20 per cent, of the weight of the charge of pig-iron, and a little coke breezes is at the same time added, and these materials are then brought to a bright glow by gentle blowing through the converter, before the charge of from 7 to 15 tons of molten phos- phoric pig-iron, low in silicon, and at as high a tempera- ture as possible, is introduced into the vessel. The blast at a pressure of about 25 Ibs. per square inch, is now turned on, when the converter is turned up, and the blow lasting from thirteen to twenty-five minutes, is conducted in the usual manner until the carbon is eliminated from the charge ; but instead of stopping the blow at this point, according to the ordinary Bessemer practice, the blow is continued for two or three minutes longer, and it is during this over- or after-blow that the phosphorus is removed from the metal. The carbon lines in the spectrum of the flame usually disappear in about ten minutes, in a blow lasting altogether about fifteen. During the after-blow the temperature rises rapidly, attaining eventually to about 1,800 C. ; and during this period also red fumes are emitted from the mouth of the vessel, at first only slightly, but they become more copious and increase in density towards the end, and particularly during the last half- m-inute of the conduct of the process. The larger the Chap. XXI.] THE BASIC PROCESS. 497 proportion of phosphorus in the pig-iron, the thicker ia the smoke and greater the elevation in the temperature. When the process is judged to be nearly complete, and the phosphorus to be almost eliminated, the vessel is turned down, and a sample of the metal is removed in a suitable ladle and cast into a small ingot, which is then hammered out flat, cooled in water, and broken, when, according to the degree of its malleability and ductility, with the appearance of the fracture, the workman judges of the degree of purification, and the vessel is again turned up, and the blowing resumed for a short time longer if the dephosphorisation is thought to be in- complete. The operation of sampling is repeated until the desired condition is attained, but with practice usually one sampling will suffice to determine the end of the blow. 835. The fracture of the sample taken from the converter presents large and bright crystals when the process is incomplete, the crystals becoming smaller as the dephosphorisation is more perfect. When a satis- factory test-sample has been obtained, the slag is run out from the converter as completely as possible to prevent any portion of the phosphorus from being again reduced from the slag by prolonged contact with the molten metal; but at other works, again, as at the Horde Works, the slag is not run off before the spiegel is added. The necessary amount of spiegeleisen, or of ferromanganese, or of both, is then added in the usual way, the molten spiegeleisen being added to the metal in the converter, whilst a little ferromanganese in its cold state is thrown into the ladle; but the addition of spiegeleisen is attended with only a weak and much less marked reaction than occurs at this stage of the acid process. The necessary recarburisation having been thus effected, the teeming of the metal into the ladle and the casting into ingots are conducted in the usual manner. Instead of adding the spiegeleisen or ferromanganese to the converter in the manner just described, in another modification of the basic process the metal at the end a a 498 STEEL AND IRON. [Chap. XXI. of the after-blow is emptied into the ladle, and then a proportion of molten haematite pig-iron is added thereto, whereupon a violent reaction usually ensues and the slag overflows the ladle. After the reaction has subsided a small proportion of spiegeleisen or of feri'omanganese is added to complete the recarburisation of the steel, and then the casting proceeds as before. 836. The following analyses indicate the changes in thv ANALYSES OF THE METAL AT VARIOUS PERIODS OF THE BASIC PROCESS AS CONDUCTED IN WESTPHALIA. Metal after blowing for Original pig-iron. 4^ min. ""- lit min. and end of ordinary blow. 13 min. or end of after-blow. Carbon . 2-94 0-538 2-48 0-811 0-049 Silicon . 0-523 0-009 - Phosphorus . 1-22 1-25 1-32 0-786 0-021 Manganese . 0-611 0-247 0-123 Copper . Sulphur 0-152 0-111 0-206 0-277 0-262 0-119 0-206 ANALYSES OF METAL AT VARIOUS PERIODS OF THE BASIC BESSEMER PROCESS AS CONDUCTED AT ESTON.* Metal after blowing for Driginal Pig- iron. 6 min. 12 min. 14|min. or end of ordi- 16$ min. 16 min. 35 sec. or at end of after addition of spiegel. blow. after- blow. Carbon 3-57 3-40 0-88 0-07 trace trace 0-124 Silicon 1-70 0-28 o-oi trace nil nil 0-030 Phosphorus Manganese. 1-57 0-71 1-63 0-56 1-42 0-27 1-22 0-12 014 0-10 0-08 trace 0-22 0-270 Sulphur 0-06 0-06 0-05 O-Oo 0-05 0-05 0-04 Proceedings of Cleveland Institute of Engineers. Chap. 531.] ELIMINATION OF PHOSPHORUS. 499 composition of the charge in the basic-lined converter at various periods of the blow, as examined at Eston and in Westphalia, and from these it appears that the carbon, silicon, and manganese begin to burn off almost at the commencement of the blow, while the phosphorus remains practically unchanged up to the end of the ordinary blow ; but during the two or three minutes of the after-blow the phosphorus is rapidly oxidised and eliminated from the metal, while the proportions of carbon and silicon during the same period do not suffer further change. At Horde* the green carbon lines are observed in the spec- trum of the blow two minutes after the commence- ment, while in about ten minutes the green lines disap- pear, indicating the termination of the ordinary blow according to the old or acid process, whilst an after-blow of about two minutes is necessary for the elimination of the phosphorus. The third series of analyses below show that after the addition of the spiegeleisen there is, besides an increase in the amount of carbon, also a sensible increase in the percentage of both silicon and manganese present in the steel ; and it is to be further noted that after the addition of the spiegeleisen a slight increase occurs in the amount of phosphorus in the steel beyond ANALYSES OP THE CHARGE IN THE BASIC-LINED CONVERTER AT THE RHENISH STEEL WORKS. After Original pig iron from the cupola (Jordan). After blowing 10 min. (Jordan). 2 min. over-blow or 15^ min. from the commence- ment Steel after addi- tion of spiegel (Jordan). (Jordan). Carbon 3-276 0-590 0-026 0-302 Silicon 0-476 0-222 0-002 0-016 Phosphorus 2-600 2-064 0-062 0-092 Manganese . 1-131 0-122 0-197 0-540 Sulphur 0-062 0-139 0-051 0-040 * Dr. F. C. G. Miiller : Glascr's Annalen, 1880. 500 STEEL AND IRON. [Cbap. XXI. what was contained in the spiegel itself, and that a small proportion of this element must have been therefore re- duced at this stage in some manner from the phosphoric anhydride in the slags. 837. Phosphorus can thus be eliminated during the Bessemer blow in a basic-lined converter, but for success the slag also should be as basic as possible. The phosphoric anhydride produced in the converter as the result of the oxidation of the phosphorus, either directly by the oxidising action of the blast, or by the reaction of phosphorus upon ferrous oxide, with the production thereby of ferrous phosphate and metallic iron, could in either case only exist in the converter in combi- nation with a powerful base ; and any excess of silica present in the slag would therefore at once set free the phosphoric anhydride from any oxide of iron with which it had combined, and the phosphorus would then be again reduced by the carbon, or at the high tem- perature prevailing in. the converter even by the iron itself. But it is more probable, owing to the excess of silica always present in the ganister-lined converter, that any ferrous oxide that may be formed during the process immediately enters into combination with silica, and thus any phosphoric ao-hydride resulting from the oxidation of phosphorus would not come into contact with any ferrous oxide with which to enter into combination, and without it the phosphoric anhydride would immediately be again reduced by the carbon present in the metal. But with the basic-lined vessel, on the contrary, the phosphoric anhy- dride resulting from the combustion of the phosphorus enters at once into combination with the lime added to the charge, and yields thereby a calcic phosphate which is not subsequently reduced, whilst it is probably owing to the superior affinity of carbon for oxygen over that of either phosphorus or iron for oxygen that the com- bustion and oxidation of the phosphorus and iron in the charge do not take place to any appreciable extent until the whole of the carbon is eliminated. Chap. XXI.] SLAGS OF THE BASIC PROCESS. 501 838. The slags produced in the basic process are small in quantity except towards the close of the blow, when they become more abundant, and finally exceed the amount in the ordinary Bessemer process. These slags are highly basic silicates of lime and magnesia, containing also, as would be expected, notable proportions of phos- phoric anhydride and ferrous oxide, but the proportions of these last-named oxides are small during the earlier stages of the blow increasing, however, towards the end, and assuming large proportions in the slag produced during the last minute of the after-blow. Average specimens of the slag produced in the basic process contain about 10 per cent, of silica, with from 10 to 15 per cent. of phosphoric anhydride, about 10 per cent, of ferrous ANALYSES OF THE SLAGS TAKEN AT THE END OF THE BASIC PROCESS. Slag at Slag pro- duced at Creu- sot.* Slag at end of the after- blow. Slag after the addi- tion of spiegel- Slag at the end of the ordin- ary blow. period of total decar- burisa- tion but before the Slag at end of dephos- phori- sation or after- eisen. after- blow. blow. Silica . 16-50 8-05 8-22 9-67 22-00 12-00 Alumina and a \ little chromic > 3-80 Not determined oxide Lime . Magnesia 46-30 4-00 56-54 3-10 56-03 3-29 46-94 Not determined J 47-00 j 54 00 Ferrous oxide Manganous oxide . 7-07 5-30 8-37 4-45 9-24 6-27 10-20 Not determined j 11-00 1 11-00 Sulphur 33 Sulphuric anhydride 0-63 0-29 Sulphates 5-00 5-00 Phosphoric 13-74 18-55 17*15 9-70 1^-00 16-00 Vanadic acid 1-92 Annales des Mines. 502 STEEL AtfD IRON. [Chap. XXL ANALYSES OF THE SLAG OR CINDER AT VARIOUS STAGES OF THE BASIC PROCESS.* i Time from commencement of blow. Slag 14| min. 16 min., ladle after 6 min. 12 min. or end of decar- 35 sees, or end of teeming the burisa- after- metal. tion. blow. Silica .... 42-60 35-60 33-00 16-60 18-60 Phosphoric anhydride . 0-15 2-61 5-66 16-03 13-87 Metallic Fe . 2-00 4-80 6-15 11-35 7-10 oxide, and from 40 to 50 per cent, of lime and magnesia, accompanied by variable quantities of man- ganous oxide. It thus appears that these slags very materially and fundamentally differ from the ordinary Bessemer slags, which contain at least double the above proportions of silica, while frequently reaching a content of over 50 or 60 per cent of silica (see analyses on p. 484). The quantity of pure slag produced in the basic-lined con- verter is about 20 per cent, of the weight of the steel produced, and is thus almost double the amount yielded in the siliceous or acid-lined converter. The increase in the basicity of the slag during the after-blow is shown by the last series of tables above, as is also the notable increase in the phosphoric anhydride which rises from 5 '66 per cent, at the point of total decarburisation of the charge to 16 '03 per cent, at the end of the after-blow, while in like manner, the iron, which amounted to 6'15 per cent, at the first-mentioned period, stands at 11 '35 per cent, at the end of the over-blow. 839. The pig-iron for the basic process, unlike that required for the ordinary Bessemer process, requires to be low in silicon and sulphur, but comparatively rich in phos- phorus, average samples of such pig as is used in the basic * Proceedings of Cleveland Institute of Engineers. Chap, XXI.] PIG-IRON FOR BASIC PROCESS. 503 process containing from 0*5 to 1 *0 per cent, of silicon, from 0-05 to O'lo per cent, of sulphur, 0-35 to 2-00 per cent, of manganese, and from 1 to 3 per cent, of phosphorus, the higher proportions of phosphorus and inanganes-e being, however, preferred. White pig-iron is generally employed, as affording less loss during its conversion, both as to direct waste of metal and in the wear of the basic lining of the vessel, while the length of blow with such metal is also of shorter duration ; yet either white, grey, or mottled pig-irons are available for the process. 840. The fuel or heat-producing elements in the pig-iron of the ordinary Bessemer process (p. 480) are silicon, manganese, and carbon, whilst in the dephos- phorisation or basic process, besides the elements just enumerated, phosphorus requires to be added to the list of heat-producing elements. Phosphorus affords by its combustion to phosphoric anhydride 5,747 heat units (C.), and performs the same calorific function during the "after-blow" in the basic process that silicon does during the ordinary Bessemer blow, hence, within certain limits, it may be considered that the value of a pig-iron for the basic process is directly proportional to the amount of phosphorus which it contains, so that even tap-cinder mixed with the manganiferous ores of Spain is being smelted in Cleveland for the production of a cheap phosphoric pig-iron, available for the basic process. 841. The presence of an excess of silicon in the pig- iron used for conversion into steel in the basic-lined vessel increases the amount of slag, and more rapidly destroys the lining of the vessel, besides which it in- creases the waste of metal, and prolongs the blow by lengthening the period necessary for the slag to attain the basicity required before the elimination of phosphorus can be effected. But if silicon be entirely absent, then the blow becomes too cold and slow j hence the metal for treatment by the basic process should contain a small proportion of silicon, as previously mentioned, but the process cannot deal with highly siliceous pig-iron. 504 STEEL AND IROX. [Chap. XXL 842. Where the silicon in phosphoric pig-iron exceeds about 1 per cent, such pig-iron is best treated by the " transfer method," according to which the metal is first treated for its partial desilicisation in the ordinary Bessemer converter with an acid lining, from whence, after blowing for ten or fifteen minutes, the metal is transferred, with the exclusion of as much as possible of the siliceous slag, to a basic-lined converter, in which the blowing is resumed for about three minutes for the elimination of the phosphorus. The transfer method was pursued at,Witkowitz with two converters, one acid and the other basic-lined, and the following analyses show the composition of the metal after treatment in the acid- lined vessel for partial decarburisation and desilicisa- tion, and of the same metal after transference to the basic-lined vessel for dephosphorisation ; but the method is now abandoned for the unmodified process with the basic-lined converter only. ANALYSES OF PRODUCTS AT Two STAGES OF BASIC PROCESS BY TRANSFEK METHOD. After treat- Molten pig-iron. ment in acid-lined converter for partial After comple- tion in basic-Jined decarburiga- tion, &c. 3-5 to 4 0-22 0-14 Silicon * 2-5 0-81 Phosphorus .... 0-17 0-20 0-036 843. Manganese is desirable in the pig-iron to the amount previously named (p. 503) for use in the basic process, since its presence favours the elimination of sul- phur, which is otherwise reduced only in small degree by the process ; and, also, in its absence the after-blow is liable to produce an inferior and uncertain temper of steel. 844. The yield in the basic process is about 85 per cent, of the weight of the charge of pig-iron, &c., CLap. X1] LINING OP BASIC CONVERTER. 505 uitroduced into the vessel, as against about 90 per cent, with the ordinary Bessemer process, while the output or number of blows obtained from the basic-lined converter is only about eight or ten per day of twelve hours for each vessel. 845. The wear upon the dolomitic or basic lining of the vessel is also heavier than upon the ganister or acid-lined vessel, so that, as previously noted (p. 493), the form of the ordinary converter has been modified, with a view to the equalisation of the wear upon its two opposite sides, by arranging for the vessel to receive the molten pig-iron and also to deliver the charge of steel into the ladle from either side of the converter in- discriminately ; but notwithstanding this, the basic- lined vessel requires either relining or very considerable repairs after about every sixty blows. In Bohemia, where loose twyers are employed, the bottoms last on an average from twenty-five to thirty blows before needing renewal ; but the twyers are replaced singly or in pairs during the interval, as required. In the Cleveland works, where no such renewals of the twyers are made, the bottoms only last about eleven blows before requiring to be replaced. Since the amount of steel produced from a basic-lined con- verter before relining becomes necessary, is considerably less than that produced from the siliceous-lined vessel, it follows that if the same make is to be obtained by the basic as with the acid process, then either more vessels will be required or greater facilities for rapidly changing the vessels must be adopted, and thus the application of the methods devised by Holley and others for rapidly removing one converter and replacing it by another are of more urgent importance in the basic than in the ordinary process. 846. The amount of basic materials, as lime, -plates, 230 -refinery, 230 Colcothar, 44 Cold-rolling of iron and steel, 4, 5 steel, 387 shortness in iron, 9, 53, 60, 207 steel, 9, 393 -shots in iron-castings, 189 Collaring in the rolls, 326 Columbian iron-ore, 32 Combined Siemens and Bessemer process, 453 Coming to nature, 264, 272 Commercial classification of bar- iron, 209 pig-iron, 75 Composition of blast-furnace gases, 96 gas-producer gases, 370 used in moulds for steel castings, 518 Compound armour plates, 514 Compressed air lifts, 167 Compression of steel, 512 by carbonic anhydride, 513 steam pressure, 512 Conduct of the Bessemer process, 474 Consumption of coal in the produc- tion of merchant bars, 361 puddled bars, 360 coke in steel-melting, 426 fuel in the blast furnace, 169 puddling of steel, Conversion of grey into white-iron by chilling, 68 in the refinery, 238 pig-iron into malleable iron in open-hearths, 212, 228 Converted bars, 412 Converter, Bessemer, 462, 464 for the basic process, 493 Fixed Bessemer, 462 Heaton, 441 Converting furnace, 406 Copper and iron, 59 pig-iron, 173. steel, 59, 396 Cores, 20J Corrosion of iron, 205, 388 steel, 337 Coupling boxes for rolling milli 321, 323 Cowper's hot-blast stoves, 151 Crarnpton's puddling furnace, 295 Crane, Bessemer hydraulic, 469 Crocodile shears, 348 squeezers, 301, 302 Cropping shears, 343 Crucible-moulds, 27 Cast-steel, 415, 426 , Consumption of coke in production of, 426 Crucibles, 24, 419 Annealing of, 420 Brasqued, 24 Cornish, 24 French, 24 Hessian, 24 London, 24 Plumbago, 29, 426, 430 Steel-meiting, 24, 419, 426 Crude steel, 441 Crystallisation in cylinders of cast- iron, 188 flat plates of cast-iron, 187 Cubic pyrites, 52 Cup and cone for blast furnaces, 115, 121, 176 Cupola blast furnace, 111, 118 for melting spiegeleisen, 470 the Bessemer process, 470 foundry, 189, 193 -DAMASKEENING, 393 *-> Dam-plate, 117 stone, 117 Dandy in puddling furnace, 276 Danks furnace, 2-8 revolving puddling furnace, Vcr tical section of, 288 -Winslow squeezer, 306 Danuemora brands of bar-iron. 431 524 STEEL AND IRON. Dannemora iron, 235 iron ore, 32 Dead-melting of steel, 425, 507 in open-hearth furnace, 453 -weight test for rails, &c., 401 Decarburisation methods for the production of steel, 403 Decomposition in the Bessemer converter, 475, 478 Definition of ductility, 3 elasticity, 4, 5 malleability, 6 steel, 385 tenacity, 1 Deflection of rails, 401 Detmore's puddling furnace, 275 Devonshire iron-ore, 32. Dimensions of blast furnaces, 113 Dinas clay, Analysis of, 17 fire-bricks, 19, 20 Direct basic Bessemer process, 506 Bessemer procet s, 471 process for the production of malleable iron, 211 Siemens, for the production of malleable iron, 213 steel, 406 reduction of iron ores for steel, 402,403 Distribution of heat in the blast furnace, 101 Disulphide of iron, 52 Dolomite, 106, 495 Double bullet bar iron, 431 puddling furnace, 270, 277 shear steel, 411, 414 squeezer, 302 Doubles, 211 Drawing the heat in the cementa- tion process, 411 Dropping of the charge in puddling, 262, 264 flame in the Bessemer process, 476 Dry-bottom for puddling, 274 puddling, 238, 249, 252, 267, 271 -sand castings, 197 Drying in puddling process, 272 Ductility of metals, 3 Effect of carbon upon, 8 heat upon, 3 silicon upon, 3 Dull-red heat, 8 T^ASTWOOD'S mechanical rabble, Economy of fuel in the blast furnace, Effects of hammering or rolling steel, 397 other metals on pig-iron, 73 wire-drawing, 387, 397 Elasticity, Limit of, 4, 5 in steel, 399 of metals, 4 steel, 397, 400 Elevation of blowing engine, 162 puddling furnace, 254 Rachette furnace, 137 Refinery, 239 Elimination of phosphorus in basio Bessemer process, 500 puddling, 253 sulphur in the basic process,253 silicon and phosphorus in the open-hearth processes, 458 Ellerhauseu's process for the pro- du tion of steel, 444 Engines, Blowing, 143, 160 for Bessemer process, 489 Rolling mill, 340 Extensiou of the metal in plate- rolling, 3J4 Eye of f urnace, 126 -piAHLUN blast furnace, 13(5 - 1 - Falling-weight test for rails, &O., 401 Farnley iron, 268 Fatigue of metals, 6 Feeder, 129 Feeding-gates, 201 Feed-rolls, 338 Ferric acid, 46 anhydride, 46 disulphide, 50, 52 oxide, 44 Hydrated, 45 sulpbide, 50 Ferrous carbonate, 49 silicate, 55 Roasting of, 83 sulphide, 50, 51 Ferromanganese, 58, 75, 78, 99 Use of in the Bessemer process, 480 Ferry-hill blast-furnace, 113 Fettling, 252, 256, 259, 260, 290 Fillifer's calcining kiln, 91 FiHe-metal, 245 Finery, 229, 230 -cinder, 232, 244 for the production of steel, 433 process, 229 Fining, 11 stage of the Bessemer process, 475 INDEX 525 Finishing rolls, 323, 325 Fire-bricks, 18 Analyses of, 22 Dinas, 19, 20 Glenboig, 22 Newcastle, 22 Silica, 21, 22 bridge of the puddling lurnace, 255 -clays, 17 Analyses of, 17 The hollow, 230, 233 Firestones, 23 Firing-hole of the puddling furnace, Fix, for the Danks furnace, 200 Fixed Bessemer converter, 462, 471 Flame from the Bessemer converter, 475, 486 Flask and plug for crucible making, 25,27 Flexibility of steel, 400 Floating of solid on fluid pig-iron, 68 Flow-gates, 201 Flue-bridge of the puddling furnace, 255 cinder or slag, 360 -dust, 159, 185 Fluid compression of steel, 510 Fluidity of blast furnace slags, 109 Fluorine steel process, 442 Flux, 11, 103 Nature and quantity of, 104 Fore-hearth of the blast lurnace, 117 -plate for rolls, 322, 326 Forest of Dean iron-ore -, 86 Forgo, 303 iron, 51, 57 -scale, 14, 56, 206 -tests for steel, 399 of malleability, &c., 6, 401 train for rolling puddled bars, 319 Forging presses, 315 Forms of blast furnace, 111 Formula of blast furuace slags, 14, 106 refinery slags, 14, 243 Foundations for stearn hammers, 314 Foundry appliances, 185 Cupola, 189, 190, 193 iron, 53, 66, 76, 186 sand, 196 Fov.r-higb rolls, 337 Frankliuite, 33 French Admiralty tests for steel, 399 Frontal helve, 3US Fuel for the blast furnace, 168 cupola fouudry, 193 Furnace, Alfreton, 182 Furnace, Annealing, 420 Balling, 356 Blast, 111 Action of the, 94 Blauofen, 133 Bloomery, 222 Blowing in a, 139 Carinthian gas, 382 Catalan, 218 Cementatioi), 406 v Charges of, 177, 268, 292, 410, 4H, 426, 427, 435, 449, 452, 456 Cleveland blast, 111 Converting, 406 Cupola blast, 111 Danks puddling, 288 Ev of, 126 Gas, 361, 363 High blooinery, 225 " In blast," 93 Moltiug, 417, 429 Mill, 1356 Open-hearth steel-melting, 445 Pernot, 297, 451 Pousard, 278, 361, 380, 452 Puddling, 255, 270, 273, 275, 276. 277, 280, 288, 294, 295, 297 for steel, 435 Eachette, 133 Refinery, 239 Reheating, 355 Scotch blast, 111 Siemens melting, 428, 445 regenerative, 371 reheating, 3/1 rotary, 213 Staffordshire, 110 Steel-melting, 417, 429 -- Stiickofen, 215 -tops, 121, 124, 125 Fusibility of blast furnace slags, 109 (^.ALVANISING of iron, 58 ** Gangue, 10 of iron ores, 93 Ganister, 123 Analyses of, 22 Gas furnaces, 361, 363 Advantages < >f , 363 Bicheroux, 280, 361 Boetius, 378 Carinthian, 382 Ponsard, 278, 361 Siemens regenerative, 361, 371 ports of the open-hearth steel- melting furnace, 448 producers, 362 Brook and Wilson's. 367 Casson's, 367 526 STEEL AND IRON. Gas producers, Fuel for, 362 Gases, Composition of blast furnace, 182, 183 froin Bessemer converter, 485 Siemens producer, 369 Analyses of, 370 soaking pits, 383 occluded by steel, 392, 507 Gates, 201 Pouring, 201 Gjer's calcining kiln, 89 - pneumatic lift, 167 - soaking pits, 382 Glamorganshire iron ores, 36 Glazed bars, 413 pitf-irou, 55, 73, 78, 99 Glenboig fire-bricks, 22 Gold and iron, 61 Goose-neck, 126, 472 Gothite, 36, 45 Grades of pig-iron, 76 Granite, 23 Graphite in iron, 48, 62 Green-sand castings, 197 Grey pig-iron, 48, 63, 98, 102 Gridiron brand of bar iron, 431 Griffiths' mechanical rabble, 287 Group casting of steel ingots, 473 Guide-iron, 3i!6 -jaws, 326 train of rolls, 326 Guillotine shears, 348, 351 1T.SEMATITE, Brown, 35 - 1 - 1 Analyses of, 36 Red, 33 Hammers, 307 Helve, 307, 308 -scale, 42, 43 - Shingling, 300 -slag, 42, 43 Tilt, 307 Hardening of steel, 388 Haswell's forging press, 315 Hearth, Blast furnace, 111, 115, 117, 132 Swedish-Lancashire, 233 Heat, A, in puddling, 266 balling furnace, 359 Bessemer process, 480 -producers in basic process, 503 Heating-power of the gases from the Bessemer converter, 480, 486 Heaton converter, 441 process for the production of steel, 440 products, Analyses of, 442 Height of the blast furnace. 118 Helve, Shingling, 308 Henderson's process for the produc- tion of steel, 442 Hessian crucible, 24 High bloomery furnace, 225 Hoists, 143, 164 Holley's movable bottom for the Bessemer converter, 467, 468 Hollow Fire, The, 230, 233 Honeycomb structure in steel ingots, 424, 507 Hoop L bar-iron, 431 F bar-iron, 431 Horizontal rotary squeezer, 304 Horse, 143 Hot-blast, Advantages of, 174 iron, 69, 77, 173, 179 pipes and the fracture of, 151 stove, 143, 144 Circulur, 147 Cowper's, 151 Massi.ck's, 148, 159 Pistol pipe, 149 Rectangular, 14> Regenerative fire-brick, 151 Westphalian, 150 Whitwell's, 155 Temperature of, 143, 155, 158, 173, 178 Twyer, 126 Use of, 173 Housings for rolls, 321 Hydrated ferric oxide, 45 Hydraulic casting press, 511 forging process, 315 lifts, 166 squeezer, 307 TLMENITE, 36 -*- Incipient redness, 8 Inclination of twyers in the blast furnace, 127 Inclined plane, The, 164 Indirect process for the production of malleable iron, 212, 228 Ingot-iron, 384, 385, 461 moulds, 423 Preparation of, 423, 427 Iron, Allo>s of, 57 Aluminum and, 61, 208 Antimony and, 60 Carbide of, 49 Carbon and, 46, 48 Carbonate of, 49 j Chromium and, 58 Cobalt and, 61 I Cold-blast, 69, 70 I short, 9, 53, 60, 207 INDEX. 627 lion, Copper and, 59 Dannemora, 235 Direct reduction of malleable, 211 Disulphide of, 52 Fuel used in smelting, 114 Galvanised, 59 glance, 33 Gold and, 67 Grey pig-, 49, 63, 98 Hot-blast, 69, 77, 173, 179 Lead and, 61 Low Moor, 208, 268 Malleable, 202 Manganese and, 58 Merchant bar-, 209, 343 Metallic, 40 Meteoric, 31 Mottled cast-, 48, 63, 66 moulds, Preparation of, for the reception of the steel, 423, 427 Native, 31 Nickel and, 60 Nitrogren and, 57, 385 Occlusion of gases by, 41, 67, 392 ores, 30 Analyses of, 32 Bispberg, 32 Brown, 35 Calcination of, 81 Clay ironstone, 37, 38 Lenticular, 34 Magnetic, 31 Oural, 32 Persberg, 32 Phosphorus in, 53 Preparation of, 80 Bed haematite, 33 Boasting of, 81 Self -fluxing, 104 Smelting of, 92 Spathic, 37 Titaniferous, 79 Weathering of, 80 Oxides of, 43 Oxygen and, 43 Passive condition of, 43 Phosphorus and, 52, 72, 207, 393 -pLtes, 209, 210 PlatinunPand, 61 Puddling of, 11, 248, 254 Pure, 1, 40 pyrites, 52, 86 Bed-shortness of, 51, 60, 207 Rusting of, 42, 45 Silicates of, 31 Silicon and, 54, 207 Silver and, 61 -smelting in Japan, 139 Specitic gravity of, 41 Iron Specular, 83 Sulphides of, 31 Sulphur and, 50, 71 Tin and, 59, 60, 2~>8 Titanium an I, 208 Tungsten and, 58 Welding of, 7, 55, 204, 387 White, 48, 98 Wrought, 202 Zinc and, 59, 208 JAPAN, Iron-smelting in, 139 u Jerking strains, Effect of steel, 401 T7-AOLIN or China clay, 26 ** K idney iron ore, 34 " Killed," in crucible steel-melting, 425 Kilns, Calcining, 84, 88 Kilogramme, 2 Kisb, 49, 69 Krupp's washing process, 246 T ADLE, Bessemer casting, 469, -" 472 Lake-ore, 36 Lancashire hearth, 233 Langen's blast f miace top, 124 Lattens, 211 Lead and iron, 61 Ledebur, Prof., on welding, 7 Lenticular iron ore, 34 Lettiug-down of steel, 389 Lifts, 143, 164, 165 Perpendicular, 165 Lime, 15 in blast furnace slags, 108 the basic Bessemer process, 505 Use of in the Styrian furnaces, 16 Limestone as a flux, 104 Fpssiliferous, 105 Limit of elasticity in steel, 400 Limonite, 36, 45 Lining of Bessemer converter, 467 Basic, 494 Danks furnace, 291 Second, for Danks furnace, 291 Lloyd's fans, 194 tests for steel plates, 399 Loam, 197 Castings in, 197 Loss in calcination of iron ores, 84 puddling process, 267, 268 rolling of steel, 361 528 STEEL AND IRON. Loss in Siemens-Martin process, 451 Low Moor iron, 208, 268 Lurman's closed hearth, 132 TV/1 AGNESIA, 15 m Magnesite, 15 bricks, Ib, 495 Magnetic iron, Analysis of, 32 ore, 31 oxide, 43 pyrites, 52 Magnetite, 31, 44 Maintenance of a uniform pressure of blast, 163 Make of iron in the blast furnace, 103, 136, 174, 179 Malleability, Definition of, 6 of iron, 7, 204 Malleable cast-L-on, 282 iroD, 202 . Analysis of, 205 castings, 282 Cold-short, 9, 53, 60, 207 Commercial varieties of, 203, 209 Corrosion of, 205 Direct production of, 211 Ductility of, 204 Indirect production of, 228, 248 Malleability of, 7, 234 Melting point of, 204 Phosphorus and, 207, 393 Production of, direct from the ore, 211, 213, 217, 222, 225 from pig-iron, 212, 228, 248 in India, 432 steel by carburisation of, 406 Red-shortness in, 51, 60, 207 Silicon and, 207 Specific gravity of, 205 Strength of, 208, 209 Sulphur and, 51, 207 Transverse strength of, 400 - Welding of, 7, 55, 204 Mallett on buoyancy of cast-iron, 166 Manganese, Action of, in steel, 388, 393, 395, 433 the open-hearth furnace, 459 the basic process, 504 Alloys of, 394 in blast furnace slags, 103 pig-iron, 74, 98 puddling process, 254 Iron and, 58, 74 Malleable iron and, 204 Manipulation of the puddling process, 201 Manufacture of crucibles, 25 tyres, 517 Marcasite, 52 Massicks and Crookes' hoc-blast stove, 148, 159 Mechanical puddling, 285 rabbles, 285 Eastwood's, 286 Griffith's, 287 Morgan's, 287 Pickles', 286 Wbitham's, 278, 287 treatment of the puddled ball, 30J, 301 Melting-down refinery, 242 furnace, 417 Siemens, 429, 4i5 heat, or No. 6 temper of blister- steel, 411 holes, 417 house or furnace, 41ti of cast-steel, 415 steel in reverberacory f urnacea, 429 point of cast-iron, 66 malleable iron, 204 pure iron, 41 steel, 387 stage of puddling, 261 Merchant iron, 203 Consumption of fuel in produc- tion of, 360 Piling for, 343 Metallic sponge from tLe Cnenot process, 404 Metallurgical terms, 1 Meteoric iron, 31 Micaceous iron ore, 33 Mild centred steel, 516 steel, 385, 397 Advantages of, 402 Unsoundness of, 506 Mill, 300 -cinder, 56, 360 furnaces, 356 rolls, 320 Mills, Belgian rolling, 336 Four-high, 337 Reversing, 326, 332 Rolling, 324 Three-high, 326, 327 Millstone-grit, 23 Mine, 10, 56 and cinder pig, 56 Mixtures of iron for foundry use. 186 Mopping of crucibles, 423 Mor_-au's mechanu al rabble, 287 Mottled pig-iron, 48, 63, 6t> INDEX. 52? Moulds, Bessemer, 473 -- for the fluid compression of steel, 510, 512 Mundic, 52 IV AIL rods, 210 ** Native iron, 31 steel, 31 Natural steel, 404 New South Wales iron-ores, 36 Nickel, Iron and, 60 Nitrogen, Cast-iron and, 385 Iron and, 57, 385 Steel and, 57, 384 Nobbling, 11, 269 North Lonsdale blowing engines, 163 iron-ores, 35 Northamptonshire iron ores, 36 Nose-helve, 308 rvCCLUSION of gases by iron, 41 v -^ pigr-iron, 67 steel, 392 Oil-hardening, 391 Open-hearth and Bessemer steel processes, Combined, 453, 454 steel, 445, 447, 456 melting furnace, Siemens, Longitudinal section of, 447 Transverse section of, 447 Ores, Dressing of, 84 Iron, 30 Production of steel direct from the, 402, 403, 406 Self-fluxing, 104, 136 Ovens, Blast, 143 Overblown Bessemer metal, 478 Overblow of the basic Bessemer process, 496, 506 Oural iron ores, 32 Output of the blast furnace, 180 Bessemer plant, 487 Oxides of iron, 43 Oxygen, Iron and, 43 PARRY'S process for the produe- * tion of steel, 281 of double puddling, 281 Passive condition of iron, 42 Peeler, 358 I I Persberg brands of bar iron, 431 iron ore, 32 Pernot revolving furnace, 297, 451 Perpendicular lifts for the blast furnace, 165 Phosphorus, Bar-iron and, 207, 393 Calorific power of, 503 Cast-iron and, 72 Conditions for removal in basic process, 500 Elimination of, in the puddling process, 253, 267, 271, 281 Iron and, 52, 72, 207, 393 Reduction of, in the blast furnace, 53, 97, 102 Steel and, 393 Physics employed in steel melting, 432,439 Pickles' mechanical rabble, 288 Pickling of plates, 388 Pig-bed, 129 -boiling, 11, 248, 252, 259, 267 Forge, 51, 57 -iron, 61 Action of acids upon, 69 All-mine, 78 Analyses of, 64, 65 Bessemer, 73, 461, 482 Blazed, 55, 73, 78 Cinder-, 78 Classification of, 75 Conversion of, into malleable iron in open-hearths, 212, 228 Copper and, 73 Crystalline forms of, 63 Effects of other metals upon. 73 from clay ironstone, 492 Cleveland ores, 51, 492, 503 for the basic process, 492, 502 Foundry, 50, 66, 76 Glazed, 55, 73, 78, 99 Grades of, 77 Grey, 49, 63, 98 Manganese and, 58, 74, 98 Melting-point of, 66 Mine and cinder, 78, 83 Mottled, 48, 63, 66 Occlusion of gases by, 67 Phosphorus and. 72 Production of, 79 Refining of, 238 Silicon and, 67, 72, 99 Specific gravity of, 63 Strength of, 71 Sulphur and, 50, 71 Tin and, 74 Titanium and, 73 White, 49. 63, 98 Pigs, 130 - Swedish, 130 530 STEEL AND IRON. Piles for rolling, 324 Piling for best-iron, 210 merchant iron, 343 plates, 344 rails, 344 Pipe in hard steel, 506 stoves, 144 Disadvantages of, 151 "W'estphalian, 135 Piping of steel ingots, 392, 424, 506 Pistol-pipe hot-blast stove, 149 Plane, Inclined, 164 Plan of bed of converting furnace, 408 puddling furnace, 255 refinery, 240 Plate-metal, 245 -mills, 320, 333 shears, 349 Plates, Piling for, 344 Strength of, 209 Platinum and iron, 61 steel, 61, 396 Plug -holes in the gas producer, 365 Plumbago crucibles, 29, 426, 430 Pneumatic lifts, 167 process for the production of steel, 460 Ponsard gas-furnace, 278, 361, 380, 452 producers, 367, 380 recuperator, 380 Potassic iodide, a physic for steel, 433 Pottery-mine, 260, 261 Pouring gates, 201 Preparation of iron-ores, 80 Press for compressing fluid steel, 511 Pressure of blast for the Bessemer converter, 462, 475 blast furnace, 171, 172 Price's puddling furnace, 276 Process of fluid compression of steel, 510 Producer, The gas, 362 Production of heavy cast-iron cast- ings, 195 homogeneous steel ingots, 506 malleable iron direct from the ore, 211, 213, 217, 222, 225 from cast or pig-iron, 212, 228,248 pig-iron, 79 sound steel ingots by pressure, 509 rotation, 514 stirriner, 514 steel by the carburisation of malleable iron, 406, 430 Production of steel by the fusion of bar-iron with charcoal, 430 pig-iron with mal- leable iron, 445 decarburisation of pig- iron, Methods for the, 403, 433 direct from the ore, 402 Methods for the, 402 Parry's process, 281 Puddled ball, Forge train for the rolling of, 319 Mechanical treatment of, 300, 301 bar, 209, 324 Consumption of fuel in the production of, 360 steel, 434 Analyses of, 438 Puddler's mine or ore, 34, 259 Puddling, 11, 248, 254 Drv. 238, 249, 252 Furnace, 255 Bicheroux, 280 Caddick and Maybery's, 273 Carinthian gas, 275 Crampton's, 295 Banks, 288 Detmore's, 275 Double, 270, 277 Elevation of, 254 for steel, 435 Gas, 273 Pernot's, 297 Plan of bed of, 255 Price's, 276 Siemens, 273, 288 Spencer's, 294 Vertical section of, 254 Loss in, 267, 268 Mechanical, 285 Methods of, 249 Parry's double, 281 process, 248, 250, 435 Balling stage of, 262, 264 Boiling stage of, 262, 264 Dry, 249, 252, 267, 271 Elimination of phosphorus in, 253, 267, 271, 281 ' sulphur in,253 Manipulation of, 261 Melting-down stage of, 261 Wet, 248, 252, 267 Reactions in, 249 rolls, 319 - tools, 280 Pullers-out, 422 Pulpit of Bessemer plant, 469 Pure iron, 1, 40 Purple iron-ore, 260 Pyrites, Cubic, 52 Magnetic, 52 INDEX. 531 Pyrites, White-iron, 52 Yellow, 52 Pyritous ores, Boasting of, Pyrrhotine, 52 T)ACHETTE furnace, 136 ** Rail ingots, 473 ' rolling, 338, 516 tests, h99, 400, 401 Rails from the Siemens-Martin pro- cess, 451 Piling for, 344 Ramsbottom's duplex steam ham- mer, 315 Raw steel, 433 Reactions in the Bessemer con- verter, 475, 478 blast furnace, 94, 96 Catalan furnace, 221 open-hearth steel-melting furnace, 458 puddling furnace, 249 refinery, 243 Rectangular hot-blast stove, 144 Recuperator, Ponsard's, 380 Red haematite, 33 Analyses of, 34 ochre, 34 shortness in iron, 9, 51, 59, 60, 71, 207 steel, 51, 39i, 395 Reducing agent, 10 in the blast furnace, 94, 95 Reduction, Definition of, 10 of ferric oxide by carbonic oxide, 96 phosphorus in the blast fur- nace, 53, 97, 102 silicon in the blast furnace, 54, sulphur in the blast furnace, 98 Reeking of ingot -moulds, 423 Refined iron, Analyses of, 244 metal, 239, 244 Refinery, 229, 239 cinder or slag, Analyses of, 244 Formulae of, 243 Elevation of, 239 Melting-down, 242 Plan of, 240 Eunning in, 242 Yield of, 246 Yorkshire, 242 Refining of pig-iron, 11, 228, 229, 238 Reactions in the, 243 Refractory materials, 14 Regenerative gas-furnace, Siemens 371 Eegenerators, 373 Surface of, 377 Regulator for the blast furnace, 163 Reheating furnace, 355 Bicheroux, 378 Boetius, 378 Siemens, 371 Eelining and repairing of converters, Eeverberatory furnace for steel- melting, 429 Eeversing mills, 327, 330 Engines for, 340 valves for Siemens furnaces, 374 Revolving furnaces, 287 Crampton's, 288, 295 Danks, 288 Maudsley's, 288 Menelaus', 288 Pernot's, 293 Ponsard'a, 278, 380, 452 Sellers', 288 Siemens, 213, 288 Spencer's, 294 Tooth's, 283 Walker and Warren's, 287 Rising of steel in the moulds, 424 Eivets, 7 Tests for, 401 Eoasting of ferrous silicates, 83 iron ores, 81 between closed walls, 87 in kilns, 88 open heaps, 84 pyritous ores, 86 Rocks, Use of, in furnace construe tion, 14 Rollers, Feed, 338 Roiling, Effect of cold-, 4, 5 mill engines, 340 Size and speed of, 337 mills, 319 American, 339 Belgian, 336 for steel, 316, 516 of plates, 211, 330, 333 rails, 338, 361 steel, Loss in, 361 Rolls, 319 for merchant iron, 327 Four high, 337 Housings or standard for, 321 Mill, 319, 324 Puddling, 319 Roughing, 319, 330 Roots' blower, 194 Rotary furnace, Siemens, 218 532 STEEL AND IRON. Rotary squeezer, 304 Rotation of steel castings, 514 Rouge, 44 Rough pottery-mine, 261 Roughing rolls, 319, 330 hole, 131 Running-in refinery, 242 of pig-iron, 129 -out fire, 229, 230, 239 Russian sheet-iron, 7 Rusting of iron, 42 O AGGERS, 284 ^ Sampling in the basic process, 497 Sand-bed, 129 Burnt, 196 Foundry, 196 Siliceous, 23 Sandstones, 23 Sap in blister steel bars, 411 Saw for cutting hot iron, 346 Scaffolding of the blast furnace, 139, 142 bchafhautl's powder, 271, 439 Schiele's fans, 194 Scotch twyers, 127 Scouring slags, 110 Section of Bessemer ingot, 506 Self-fluxing iron-ores, 104, 136 -going iron ores, 104 Serpentine, 23 Shear-steel, 411 Double, 411, 414 Single, 414 Shearing machine, 348 Bhears, Crocodile, 348 for puddled bars, 347 Guillotine, 348, 351 Plate, 349 Sheds for tempering clay, 418 Sheet-iron, Russian, 7 Annealing of, 9 -mill, 334, 342 Sheets, 211 Annealing of, 335 Sherman's process, 433 Shingling, 11, 309 hammer or helve, 300 - machinery, 300 Ship-plates, Strength of, 5, 401 Siderite, 37 Siemens and Bessemer process, Combined, 453 direct process for the production of steel, 406 gas producers, 363 Gases from, 369 Siemens-Martin process for the pro- duction of steel, 445, 449 melting furnace for crucible steel 428 open-hearth steel melting fur- nace, 445 process, 456 process for the direct production of malleable iron, 211, 213 Regenerative gas furnace, 273, 361, 371 reheating furnace, 371 Revolving puddling furnace, 288 Rotator, 213 Sight-holes in producer, 365 Silica bricks, 21 Analyses of, 22 Silicates, Colour of, 12 Ferrous, 55 Silico-ferromanganese, 507 Analyses of, 508 melting, 508 Silicon, Bessemer pig-iron and, 481, 482 Cast-iron and, 54, 67, 72, 99 Effects of, in the basic process, 503 heat producer in Bessemer pro- cess, 503 Iron and, 54, 207 Reduction of, in the blast fur- nace, 54, 69, 99 Steel and, 394 Use of, in production of sound ingots, 507 Silver, Iron and, 61 Singles, 211 Single shear-steel, 414 Size of rolling mills, 337 Skimming gates, 201 of crucible steel, 423 Skulls, Bessemer, 465, 477 Slag, 11 Basic Bessemer process and, 500 Bessemer, 483 Blast furnace, 12, 14, 103, 103 Analyses of, 107 Phosphorus in, 98 Sulphur in 98, 109 Uses of, 131 Bricks of, 131 Mill-furnace, 360 test for the Bessemer blow, 470, 478, 485 -wool, 132 Slags, 12, 103 Formulae of, 12, 106, 217, 243 from the puddling of steel, 438, 439 of the Catalan furnace, 218 Puddling furnace, 253, 266 INDEX. 533 Slags, Refinery, 14, 243, 244 Scourine, 110 Sulphur in, 98, 109 Slips in*the blast furnace, 142 Slit-rods, 210, 339 Slitting mill, 210, 339 Slurry, 466 Smelting of pig-iron, 92 Soaking-pits, 382 Gases from, 383 Soft-centred steel, 516 Softness, Definition of, 8 Solubility of pig-iron in acids, 69 Somorrostro iron-ore, 35, 36 Sound ingots produced by pressure, 510 rotation, 514 stirring, 514 South Wales process for the con- version of pig-iron into malleable iron, 229 Sow, 129 Spathic iron-ore, 37 Specific gravity of compressed steel, 512 malleable iron, 41, 205 pig-iron, 63 steel, 387, 512 Spectroscope, Application of, to the Bessemer process, 490 Specular iron, 33 Speed of puddling-rolls, 324 rolling mills, 337 Spenser's revolving furnace, 294 Spiegel, Analysis of, 65 Cupola for melting, 470 Spiegeleisen, 58, 74, 99 Analysis of, 65 Charges of furnace for, 178 Ores for production of, 38 Use of, in steel-mating, 393, 395, 480, &c. Spindles for rolls, 321, 323 Sponge, Metallic, 225, 404 Spring temper of blister- steel. 411, 414 Sprue gates, 201 Squeezers, 301 Alligator and crocodile, 301 Brown's, 301, 303 - Double, 302 Horizontal, 303 - Hydraulic, 307 Rotary, 304 Winslow's, 306 Staffordshire blast-furnace, 111, 116 charges for puddling-furnaces 268 tap-cinder, 280 twyer, 127 Stampings, 232, 269 Stamps, 232 Steam-hammer, 310, 518 Foundations for, 314 -hoists, 168 Steatite, 23 Steel, 384 Action of manganese in, 388, 394, 433 Alloys of, 394 Aluminum and, 61, 396 Analysis of, 384 Annealing of, 391 Bessemer process for the manu- facture of, 460 Blister, 411, 412 Burnt, 391 Carbon in, 384, 398 Castings in, 518 Cast or crucible, 415 Catalan process for the produc- tion of, 403 Cementation, 411, 412, 415 Chromium and, 388, 396 Copper and, 59, 396 Corrosion of, 387 Crude, 441 Decarburisation methods for the production of, 403 Definition of, 385 Double-shear, 411, 414 Elasticity of, 391, 397, 401 Ellerhausen process for the pro- duction of, 444 Flexibility of, 400 Forge tests for, 399 Gold and, 396 Government tests for, 399 Hardening of, 388 Heaton crude, 440 Henderson process for the pro- duction of, 442 Homogeneous, 416 ingots, Unsoundness of, 506 in the Catalan forge, 403 Limit of elasticity of, 401 Manganese and, 388, 394, 433 melting crucible, 24, 419 furnace, Siemens open-hearth, 445 house or furnace, 416 point of, 387 Methods for the production of ,402 Natural, 404 Nitrogen and, 384 Occlusion of gases by, 392 Oil-hardening of, 391 Open-hearth, 445 Phosphorus in, 393 Physics for, 432 Platinum and, 61, 396 Production of, by the decarburi- sation of pig *ron in the fiuery, 433 534 STEEL AND IRON. Steel, Production of, by the fusion of bar iron with charcoal, 430. pig - iron with malleable iron, 445 direct from the ore, 402, 406 - Puddled, 434 rails, Analyses of, 401, 479 Boiling of , 338 .Red-shortness of, 51, 394, 395 Rigidity of, 397 Rolling of, 346 - Shear, 411, 414 Siemens-Martin, 445, 449 direct process for the prodxic- tion of, 406 Silicon and, 394, 507 Soft or mild centred, 516 Specific gravity of, 387 Structural uses of, 5, 402 Styrian method for the produc- tion of, 433 Sulphur and, 393 Tempering of, 388, 389 Tempers of, 398 Tenacity of, 397 Tensile strength of, 397 Tin and, 60, 396 Titanium and, 396 Transverse strength of, 400 Tungsten and, 388, 395 Uchatius method for the pro- duction of, 443 Wire-drawing of, 387, 397, 401 Sterro-metal, 59 Stopper-hole, 258 Stoppering of steel ingots, 422, 424, 460,473 Stourbridge clay, Analyses of, 17 Stoves, 143 Hot-blast, 143, 147, 150, 151, 155, 159 Strength of bar-iron, 53, 209 castings, 186 cast-iron, 71 iron, 208, 209 steel, 53, 397, 399, 400, 401 Units of, 1 Stripping of ingots, 382, 472 -plate for mill rolls, 326 Stiickof en furnace, 225 Styrian blast furnace, 130, 133 method of producing steel, 433 Sulphide of iron, 50 Sulphur, Cast-iron and, 50, 71 Elimination of, in the puddling process, 253, 267, 271 in slags, 28, 109, 253 - Irou and, 50, 71, 207 - Malleable iron and, 51, 207 Pig-iron and, 50 Sulphur, Reduction of, in tlie blatrt furnace, 98, 102 Steel and, 3P3 Suspension links, 4 Sweden, Walloon process of, 229, 235 Swedish blast furnace, 112, 124, 135 brands of bar-iron, 431 calcining kiln , 91 finery, 233 iron ores, 32 Lancashire hearth, 233 pigs, 130 rpAP-CINDER, 56, 266, 276, 279, Formulae of, 14 hole of the blast furnace, 117 Siemens furnace, and stop- ping of, 448 Tapping of the blast furnace, 129 Teeming-holes, 417 of steel ingots, 422 Temperature attainable in the re- generative furnace. 376 Effect on the ductility of iron, 3 strength of iron, 5 in the tempering of steel, 390 of blast for the blast furnace, 143 furnace, 101 the Bessemer flame, 486 Temperatures, 8 Temper of steel, 398 Tempering of steel, 388 Tenacity, Effect of annealing upon, 2 hammering upon, 2, 397 hardening upon, 2, 388 wire-drawing upon, 4, 387, 397, 398 of malleable iron, 2, 53, 209 metals, 1 steel, 2, 397 Tensile strength, 2, 4 Effect of temperature upon, 5 for axles, &c., 402 ships' plates, 401 of iron, 208 steel, 397, 398, 400 Terms, Metallurgical, 1 Terne-plates, 60 Terre-noire silicon steel, 509 Test-pieces, Forms of, 2 Length of, 3 Testing machine, 351 of rails, 401 plates, rivets, &c., 401 INDEX. 535 Tests of the metal in the basic pro- cess, 497 Thomas, Gilchrist process, 492 Three-high rail mill, 342 rolls, 327 Throat of the blast furnace, 114 Tilt-hammer, 307 Tin, Iron and, 59, 60, 208 Pis-iron and, 74 ~ Steel and, 60, 397 Titanic steel, 396 Titauif er< >us iron-ore, 36 sands, 79 Smelting of, 224 Titanium, Blast furnace slags and, 109 Iron and, 73, 208 Nitrocyanirte of, 142 Tools, Puddler's, 280 Topping of steel ingots, 424 Tops and bottoms, Method of, 233 Furnace, 121, 124, 125 Toughness of metals, 8 Transfer method of the basic pro- cess, 504 Analysis of the pro- ducts from, 504 Transverse strength of malleable iron, 400 steel, 400 Trial or tap-bars of the cementation process, 409 Trornpe or blowing machine of the Catalan furnace, 219 Tube for taking waste gases f rom'the blast furnace, 125 Tungsten, Iron and, 58 Steel and, 388, 395 Tunnel bead, 116 Turf, Use of, in the blast furnace. 171 Twyers, Hot-blast, 126 Scotch, 127 Staffordshire, 127 Tymp, 117 -arch, 117 stone, 117 Tyres, h oiling of , 517 Strength of, 401 TTCHATIUS process for the pro- u duction of steel, 443 Ultramarine, Artificial, 109 [Jlverstone iron-ore, 34 Unit employed in Russia, Trance, &c., for tensile stress, 2 Universal rolling mill, 336 Unsoundness of steel ingots, 392, 424, 425, 506 Use of the hot-blast, 173 Utilisation of the waste heat of the blast furnace, 121, 123, 181 dimensions of the blast furnace, 111, 113 Vein-stuff, 10 Vertical Section of blast furnace, 116, 118, 119 cementation furnace, 407 Danks revolving puddling furnace, 288 Pernot's revolving puddling furnace, 254 puddling furnace, 254 re-heating furnace, 372 Siemens open-hearth >teel furnace, 447 Vessel-man, 466 TJTABBLERS of roUs, 322 Walker and Warren's revolv- ing furnace, 287 rallo Walloon process of Sweden, 229, 235 Washing process, Bell's, 246 Krupp's, 246 Waste gases of the blast furnace, 181 Methods for the col- lection of, 121, 125, 181 Water-balance lift, 165 Weathering of iron ores, 80 Welding, 7, 55, 204 Effect of foreign bo-dies upon, 8 of steel, 387 Westphalian hot-blast stove, 150 Wet puddling, 249, 269, 267 Wheelswarf, 410 White-heat, 8 pig-iron, 48, 98 Production of, 98, 102 Whitham's rabbling apparatus, 278, 287 Whitwell's stove, 155 Whit worth process for the fluid compression of steel, 510 Whitworth's casting press, 511 definition of steel, 385 hydraulic forging press, 316 Winches, 168 Winslow's squeezer, 308 Wipes, 308 Wire-drawing,Effect on the strength of iron of, 4 steel of, 387, 397, 398 536 STEEL AND IRON. Wire-drawing, Elastic limit of, 4 gauge, Birmingham, 211 Wood, Use in the blast furnace of, 171 Wootz, 432 Wrought-iron, 202 VELLOW iron pyrites, 52 - 1 - Yield of the basic process, 504 Yield of the blast furnace, 175, 179 merchant bars, 360 Siemens open-hearth steel furnace, 457 Yorkshire refinery, 242 7INC, Iron and, 59, 208 ^ Zinced plates, 59 Zones of the blast f ornace, 100 Printed by CASSELL& COSIPAKY, LIMITED, La Belle Sauvage, London, E.C 5.9C2 RETURN TO the circulation desk ot any University ot California Library or to the NORTHERN REGIONAL LIBRARY FACILITY Bldg. 400, Richmond Field Station University of California Richmond, CA 94804-4698 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS 2-month loans may be renewed by calling (510)642-6753 1-year loans may be recharged by bringing books to NRLF Renewals and recharges may be made 4 days prior to due date. DUE AS STAMPED BELOW MAR 1 2001