00 I AUTOGENOUS WELDING AND CUTTING McGraw-Hill BookGompany Purffis/iers ofBoo/br Electrical World TheEn^neerin^andMinin^Joui-iial Engineering Record Engineering News Railway Age Gazette American Machinist Signal Engineer American Engineer Electric Railway Journal Coal Age Metallurgical and Chemical Engineering Power AUTOGENOUS WELDING AND CUTTING BY THEODORE KAUTNY, ING, NURNBERG TRANSLATED BY THE AUTHOR AND JAMES F. WHITEFORD MEMBER AM. SOC. MECH. ENGRS. FIRST EDITION McGRAW-HILL BOOK COMPANY, INC. 239 WEST 39TH STREET, NEW YORK 6 BOUVERIE STREET, LONDON, E.G. 1915 ^' Ganulated carbide grains Nos. 8 to 15. (i size.) are known as gran- ulated carbide; larger sizes as lump carbide. The various apparatus for the manufacture of acety- 7 8 AUTOGENOUS WELDING AND CUTTING lene are constructed for certain sizes of carbide grains and the correct size must be used, as otherwise the operation of the machine will be irregular and under certain conditions too much gas will be developed which may become dangerous. Carbide packed in metal drums may be safely kept in the same room as the generator but the carbide must be kept absolutely dry (Fig. 4). These drums are often damaged in handling, and if water in any form reaches the carbide, acety- lene is generated and great danger of explosion arises. It is therefore advisable to store carbide cans on wooden supports (Fig. 5). Carbide drums have either a screw cover or the opening on top is closed by a sheet metal plate soldered on. In FIG. 4. Cross sec- , tion of carbide drum the latter case, care must be exercised fitted with socket j n t h e opening of the drums, as a steel chisel used for such operation may cause a spark by contact with the drum which would ignite any acetylene that might exist within. Generators. For regular welding work in factories, stationary acetylene genera- tors should be given the pref- erence and these should be made according to the ex- isting local regulations. Portable outfits may be used to advantage in the in- terior of the factories but sta- FIG. 5. Carbide storage drum supported by wooden blocks for protection against water. tionary plants have been found to be more economical as the production of the gas is more easily regulated and overheating can be more easily avoided. ACETYLENE MANUFACTURE AND APPARATUS 9 During the transformation of the water and carbide, a considerable amount of heat is liberated which has been calculated at 220 British Thermal units for each pound of carbide gasified. With 4| pounds of water and 1 pound of carbide the temperature of the water will be raised to the boiling point and steam will be formed which will reduce the active amount of water in the generator. It follows therefore that the quantity of water in the generator must be greater than 4J pounds for each pound of carbide and this must be given consideration in designing generators. Acetylene generators may be divided into two classes, viz: 1. Generators in which small quantities of carbide are introduced, by hand or me- chanical arrangement, into a /-re c n F IG - 6. Cross section of por- SUrpluS Ot water. (..blgS. b, 7, table automatic "carbide to 8, 9, 10, 11, 12.) 2. Generators in which a quantity of water flows into a chamber partially filled with carbide, the quantity of water being regulated by mechanical action. (Figs. 13, 14, 15.) Generators of both types are in use which give satisfactory results, but there are also generators of each type that not only result in poor welding but which are dangerous to operate. water " acetylene generator. A. Gas chamber. B. Water Seal. C. Gas delivery pipe. D. Carbide holder. E-F. Delivery mechanism. G-H. Delivery chute. K. Purifier. P-Q. Delivery regulator. W. Cleaning pipe. Z. Gas valve. 10 AUTOGENOUS WELDING AND CUTTING Carbide to Water Generators. The generators of the first group, carbide to water, should be so con- structed that for each weight unit of carbide 10 weight units of water are available and that the latent heat in the carbide is distributed over the entire quantity of water so that a temperature of 45 C. (113 F.) is not exceeded. In order to distribute the heat over the entire quan- tity of water, it is necessary to provide a grate on which the carbide rests during the gasification process. In this manner the heat is absorbed by the surrounding water, which reduces its specific gravity and causes it to rise to the surface, while the cooler water along the walls of the generator flows down- wards. It is of advantage to use in cylindrical generators a grate fastened on a shaft which can be operated from without, in order to loosen the residue on the bottom of the generator. It is of the greatest importance for the welder that the apparatus is kept scrupulously clean and that a sufficient quantity of clean water is provided. When a quantity of mud or sludge has accumulated in the generator, the fresh carbide introduced will become imbedded in the sludge and will not reach the grate. The circulation of the water will thus be impeded so that great heat will develop locally and FIG. 7. Delivery device of a high pressure "carbide to water" acetylene generator. ACETYLENE MANUFACTURE AND APPARATUS 11 with the introduction of air into the generator as happens when the apparatus is refilled explosions are liable to occur. In such cases the gas generated becomes overheated causing the phenomenon of polymerisation and for our purpose such gas will be designated as overheated acetylene. Overheated Acetylene. Overheated acetylene there- fore is a gas which by means of the heat resulting from the decomposition of the carbide, is partially trans- formed into the vapors of liquid hydrocarbons. These vapors condense in this reacting mass, their carbon forming tar products. The overheating of the acety- lene in the generator is indicated by a local yellow or brown discoloration of the lime sludge caused by the tar products. The accumulation of sludge is a very important factor in the operation of all apparatus into which carbide is dropped. Even in such generators where the carbide is introduced within perforated drums, an accumulation of lime-sludge must be expected. In many acetylene generators the carbide is intro- duced in perforated metal boxes, which are placed within other metal holders. In such apparatus the greater part of the lime-sludge will remain within these metal holders, in which case cleaning the generator at weekly, or even longer intervals, is satisfactory. In charging, the boxes must be only half filled, as the residue of the acetylene production has a much larger volume than the original quantity of carbide. If these boxes are filled with too much carbide, the pressure produced by the increase in volume of the mass might cause them to burst. Further, this pressure from within will compress the outer layer of the lime-sludge firmly against the walls 12 AUTOGENOUS WELDING AND CUTTING K- ---2400 FIG. 8. Vertical and horizontal cross sections of large stationary "carbide to water" acetylene generator. (Dimensions shown in millimetres.) ACETYLENE MANUFACTURE AND APPARATUS 13 of the box preventing the access of water to the car- bide, thereby causing overheating of the gas. The tar products then forming will penetrate the layer of lime- sludge and transform it into a water proof mass around the remaining carbide. In such cases quantities of carbide will remain un- used in 'the box and will be lost. As such unused por- tions of carbide are usually thrown away with the resi- due into drains and sewers, acetylene will form there and may cause severe explosions. Effect of using overheated Acetylene. The use of over- heated acetylene easily causes burned welding seams. Part of the carbon of such acetylene being transformed into tar products, the re- mainder of the gas forms a mixture with free hydrogen and other hydrocarbon products. In a molten state iron ab- sorbs great quantities of hy- drogen which is expelled again during the solidification of the metal, resulting in a foaming of the welding seam. During this foaming of the welding seam the iron is divided into thin films, which fall back into the molten mass when the gas bubbles burst; and should free carbon be present in the flame it penetrates into these films and is absorbed by the iron. This results in the soft metal of the welding seam assuming the character- istics of steel and in some cases, the properties of grey FIG. 9. Cross section of "carbide to water" acetylene generator showing jacket for protection against frost. 14 AUTOGENOUS WELDING AND CUTTING cast iron. Under such circumstances the welding seam, upon cooling, becomes hard and brittle. Another consequence of the use of overheated acety- lene is the change in the relative proportions of the acetylene and the oxygen in the welding burner. As only the volume of the acetylene is dependent upon the injector pressure in the burner, while the density of the gas varies with the temperature, such a change produces an excess of oxygen in the flame; and this free oxygen enters into the molten iron and burns the weld- ing seam. Gasifying Dust Carbide. In acetylene generators in which so called granulated carbide is introduced, it may occur that when small granulations of car- bide are used, the heavier carbide sinks in the water while the gas bubbles adhering to the small particles carry them again to the surface. The bursting of these bubbles liberates the gas directly into the gas chamber and the remaining carbide particle sinks again and the process is repeated until the carbide is entirely decomposed. The continued repetition of this operation produces gas which is unsuitable for welding purposes. This occurs particularly when using dust carbide and there- fore this grade should not be used in carbide to water apparatus. To gasify dust carbide specially constructed acety- lene generators must be used in which the carbide is FIG. 10. Cross section of "carbide to water" acety- lene generator. ACETYLENE MANUFACTURE AND APPARATUS 15 introduced in closed boxes beneath the surface of the generator water so that it is only there that the trans- formation occurs. In some acetylene generators the carbide is intro- duced in closed boxes, made from perforated sheet FIG. 11. Stationary "carbide to water" acetylene generator where carbide is intro- duced in a closed drum B. Carbide delivery. G. Acetylene chamber. K. Water filter. R. Pressure regulator. T. Delivery pipe. If. Escape vent. V-W. Gasometer. iron, which boxes are passed through the water to allow the carbide to gasify beneath the gas collector. With such apparatus the gasometer bell must not be loaded as this might permit the pressure to increase so that the gas will break the water seal of the gasometer and escape into the generator room causing danger of explosion. This may also occur if the resistance which the gas has to overcome in its passage from the gene- rator to the gasholder appreciably increases. The con- 16 AUTOGENOUS WELDING AND CUTTING necting pipe should therefore be fitted with a waste pipe through which the accumulated water may be drained off and this should be considered in the con- struction of acetylene generators. Water to Carbide Generators. A widely used type of apparatus is one wherein the carbide is gasified in special chambers, the water supply to which is regulated by the movement of the gas- ometer bell. A retort containing such cham- bers can either be ar- ranged in the lower part of the gasometer or be provided in special generator ves- sels. In the operation of apparatus of this kind, it is necessary to insure that the outlet of the carbide chambers is in proper working order before the refilling is effected and also that the chambers are thoroughly washed and dried before recharging. If, in generators of this type, the carbide chamber is di- vided by a number of partitions, not more than 5 pounds of carbide should be placed in any individual section. Should a greater quantity of carbide in a single mass be periodically attacked by water, the influx of which water is stopped when the gasometer bell reaches a certain height, then the heat which will continue to be liberated may lead to spontaneous combustion upon the opening of the chamber; the atmospheric air entering and form- ing with the acetylene an explosive mixture. FIG. 12. Cross section of portable "car- bide to water" acetylene generator where carbide is introduced in a closed box. ACETYLENE MANUFACTURE AND APPARATUS 17 With apparatus of this kind the gasometer bell must be sufficiently large to take up the entire quantity of gas produced by the decom- position of the carbide contained in each chamber. Should the capacity be insufficient then ap- preciable after-generation of acetylene would occur which sur- J( | plus of gas would escape and Jz ^ be lost. Another point to be observed is that the individual sections are not more than half filled as the residue occupies greater space than the original carbide and consequently stoppages can FIG. 13. Cross section of "water to carbide" acety- lene generator equipped with automatic water feed. A. Water chamber. B. C. When refilling such appara- tus, the carbide holders must be dry and it is advantageous to provide an extra set of contain- ers so that while one set is in use, the other can be thoroughly cleaned and dried. Automatic Water Displace- ment Generators. Another group of generators is of the type where the carbide placed in a basket or similar holder is periodically dipped into the gen- erator water and withdrawn. This can be effected by having the carbide container firmly built into the gasometer bell, so that the carbide, with the sinking of the bell, dips into the water. Or the carbide container can be firmly Gas chamber. Purifier. D-Di. Gas delivery. E\-E ^ 1 5 si 1 1 u .1 >, S a a 'S .S "3 8 !| 3fi . g. ^, "" 1 ' ^ a D 1 C3 h^ 00 ^ S 3 S *" S 3 '"* Remarks "3 o Q 6 *o 3 J as! 3 a 11 P 1 to a 1 15 1 TO y 1 1 ! 1 1 I la (i.a Is % % Taken as 1 99.5 69 309 6.0 54 1.0 Standard Very clean 2 99.3 68 273 7.5 48 1.3 27.8 Good cut 3 98.0 68 286 9.1 51 1.6 53.8 Fairly good 4 97.6 68 295 9.8 53 1.7 67.3 Rough cut 5 96.8 66 363 11.8 64 2.1 18.5 101.9 Very rough 6 95.0 67 377 11.6 67 2.1 24.5 98.0 Not clean and ragged 7 92.2 69 552 15.0 96 2.6 77.7 150.0 Very ragged 8 88.2 69 615 16.2 107 2.8 98.1 170.1 Very ragged and rough 9 87.3 68 660 16.2 117 0.2 116.6 207.6 Very ragged and rough 10 83.3 68 855 18.9 152 3.4 181.4 222.6 Not cut through CHAPTER VII AUTOGENOUS WELDING OF IRON AUTOGENOUS welding is a process for fusing together metallic parts and is applicable for all metals and their alloys, of which the most important are iron, copper and aluminium. In dealing with the characteristics of autogenous welding, it appears advisable to discuss the more im- portant metals, a knowledge of which is essential for such process. Iron. Technical iron is an alloy of pure iron with other elements, the most important of which is carbon; and the different properties of this important metal are dependent upon the carbon content. Iron with less than .5% carbon is called malleable iron or mild steel, according to the method of produc- tion. With .5 to 1.5% carbon it is termed steel; and with greater carbon content it is known as cast iron or white iron (Figs. 43 to 51). Carbon in Molten Iron. Carbon is always pres- ent in molten iron similar to salt dissolved in water, but when the iron becomes solid, the diffused carbon assumes other forms. It may either form iron carbide as, for instance, in pig iron or mild steel, or it may be transmuted into graphite as is the case in grey cast iron. It may continue in the diffused condition within the iron, in which case the latter forms steel or white iron according to its contents of carbon. The exact transmutation process is dependent upon 50 AUTOGENOUS WELDING OF IKON 51 FIG. 43. Micro-photograph of mild steel bar. (Magnified 80 diameters) FIG. 44. Micro-photograph of steel bar contain- ing 0.4 % carbon. (Magnified 80 diameters) 52 AUTOGENOUS WELDING AND CUTTING the other materials mixed with the iron, especially the silicon and manganese. Silicon favors the formation of graphite in cast iron, while manganese favors the for- mation of steel or white iron according to its percentage, or the form of the carbon content. FIG. 45. Micro-photograph of steel bar containing about 0.75 % carbon. (Magnified 80 diameters) The fact that iron can assume entirely different physical qualities is of paramount importance in the autogenous welding of metals. When hydrogen is employed as a heating agent for the autogenous weld- ing, a decarbonization of the iron must always occur. With the employment of the gases for heating, whose products of combustion contain free carbon, the percentage of carbon "in the iron must increase during the welding operation. If a neutral flame, as for instance a properly adjusted oxygen-acetylene flame, is made to play upon the molten iron, the percentage of carbon in the metal remains unchanged. AUTOGENOUS WELDING OF IRON 53 FIG. 46. Micro-photograph of steel bar contain- ing about 0.75 % carbon. (Magnified 300 diameters) JT IG< 47, Micro-photograph of steel bar contain- ing about 0.75 % carbon hardened. (Magnified 80 diameters) 54 AUTOGENOUS WELDING AND CUTTING The molten iron however is still capable of absorbing free hydrogen, which gas is expelled as the metal be- comes rigid. The phenomenon of foaming of the iron may thus occur in the welding seam: the iron being divided into thin films surrounding the cavities from which the gas has been expelled. Effect of Excess Carbon. If the welding flame contains free carbon, the latter is able to penetrate into these thin films and, when the metallic mass cover- ing the gas bubbles sinks back into the molten material, the welding seam becomes enriched with carbon. The seam then becomes hard and brittle and in this manner the welded portion of wrought iron may assume the character of steel or even that of cast iron. The molten iron has also the quality to form a compound with oxygen, i.e. to be burned, and as the temperature of the iron is increased the disposition to combine with oxygen is also increased. At the same time, the chemical product of the combustion of the hydrogen, superheated steam, is set free with each increase in temperature and above a certain tempera- ture, the oxygen liberated from this superheated steam passes into the molten iron. Distinction between the superheating of the iron and the combustion of it, is made entirely according to the degree of the compound of iron and oxygen. A superheating of the iron is, in reality, a lesser degree of combustion. This effect of free oxygen has to be. considered mainly in such gases as contain free oxygen, free hydrogen, or free carbon, in their products of combustion. Similar phenomenon may take place in the employ- ment of acetylene, if this gas, in the course of its generation, has become overheated by the released reaction heat. The gas used in that case for the pur- AUTOGENOUS WELDING OF IRON 55 FIG. 48. Micro-photograph of nickel steel bar unmagnetic. (Magnified 300 diameters) FIG. 49. Micro-photograph of high-speed steel bar. (Magnified 80 diameters) 56 AUTOGENOUS WELDING AND CUTTING pose of welding has thus partly passed into the poly- mere compounds of acetylene. Contained in rolled or wrought iron are flaws, which were not eliminated previous to the ingot becoming rigid. In the process of rolling, these flaws are stretched out in the same direction as the rolling and fibrous layers of iron and residues are formed within the material. When such material is passing into the molten state, under the influence of the welding flame, these flaws contract into knotty particles, affecting the quality of the material and it assumes a grainy, in place of a fi- brous, character. However, by a suitable mechanical^ after-treatment, the welding place can be given the same character as of the original rolled material. Pearlite. It has been previously mentioned that the state of carbon within the iron determines the physical quality of the latter. In a compound of certain per- centages of carbon and iron, the particles of carbon assume a " mother of pear^" appearance, which par- ticles, sprinkled among the mass of the pure iron, are pearlite or cementite. Pearlite consists of an iron carbon alloy with from .8% to .9% of carbon, and is character- istic of mild steel. A simple method of determining the carbon per- centage of iron, and thereby its density, has been given by Baumann. Place a glass plate ruled with 100 equal squares, upon the photo of the magnified polished surface of the iron under examination and the carbon percentage can be approximated from the number of these squares filled with pearlite. If for example 23 of the 100 squares are filled with pearlite, the calculation is as follows: AUTOGENOUS WELDING OF IRON 57 FIG. 50. Micro-photograph of cast iron. (Magnified 300 diameters) FIG. 51. Micro-photograph of white iron. (Magnified 300 diameters) 58 AUTOGENOUS WELDING AND CUTTING It has also been mentioned that the percentage of silicon and manganese is the determining factor of the state of carbon contained in the iron. Grey cast iron is an iron of high carbon percentage in which the car- bon content is in the form of graphite. Welding of Cast Iron. If a mass of grey cast iron is to be treated by means of an autogenous weld- ing flame, grey cast iron of a high carbon percentage and with a certain higher percentage of silicon must be employed as a filling material. During the autog- enous welding process, a part of the silicon contained in the casting evaporates, and this quantity of silicon must therefore be replaced by the filling material. As cast iron also contains manganese, as well as silicon, the formation of white iron will occur in the FIG. 52. Etching of a good welding seam. welding place, if sufficient silicon evaporates so that the manganese predominates. This serves as an ex- planation for welding seams frequently becoming hard and brittle during the welding of grey cast iron. For the autogenous welding of such iron, it is there- fore necessary to employ as filling material small bars of grey cast iron of high percentage of carbon, and a still higher percentage of silicon. The structure of the grey cast iron is a grainy one and in order to lessen the influx of atmospheric oxygen and to secure a better structure of the material, it is advisable also to employ one of the common fluxes, in the welding of such castings. AUTOGENOUS WELDING OF IRON 59 After the place to be welded has been cut away sufficiently to secure good results, the welding flame is applied until the lowest portion of the metal reaches a molten state. The heated part is then amply sprinkled with the flux and the welding bar is also heated and plunged into the molten metal. Under a continuous influence of the welding flame, the molten material of the seam is stirred, so that the filling material flows off and fills up the place to be welded. It is important that the workman should carefully observe the flow of the welding seam and if the molten iron is blown out of the groove by the flame, the work- man should observe whether there is still an unfused portion inside the welding furrow, the characteristics of such imperfectness being the appearance of film- like layers imbedded within the molten mass. If so, he must see that the material is fused in this place "also. If the welding of the grey cast iron has been properly executed, the structure at the welding place will al- ways be of better quality than the original material. Welding of Cast Steel. In welding cast steel, it must be taken into consid- eration that this is a mate- rial in which the carbon percentage is between that FIG. 53. Good welds after hav- Of mild Steel and that of in S been subjected to severe , . T . , bending test. grey cast iron. It is best to employ small cast bars of the same metal, as filling material, but as these are not always obtainable Swedish soft iron may be used in conjunction with the cast bars. 60 AUTOGENOUS WELDING AND CUTTING With ordinary care, the proper percentage of carbon can be obtained at the welding place. Weldings of cast steel can however be executed with good results by using Swedish soft- iron alone, as filling material. FIG. 54. Decarbonization of iron in a welding seam. Welding of Hard Steel. For the autogenous weld- ing of hard steel it is advantageous to employ filling bars with a high percentage of manganese. As the elasticity of spring steel has its origin in the process of hardening, if it is desired to impart physical proper- ties to the welding place similar to those of the rest of the material, it is necessary to harden the material of the welding place in the usual manner. FIG. 55. Traces of carbon deposits in a welding seam. Welding of Wrought Iron or Mild Steel. In welding wrought iron or mild steel, Swedish soft iron of small carbon percentage is employed as filling material. The melting point of such a material is between 1500 and 1600 C. (2732 F. to 2912 F.). With increasing percentage of carbon the melting point becomes lower and it sinks as low as 1050 C. (1922 F.) with an iron of such high carbon content as grey cast iron. The melting point of iron oxide lies at 1350 C. (2462 F.). AUTOGENOUS WELDING OF IRON 61 In the autogenous welding of mild steel and wrought iron the melting of the oxides, if any exist, must be accomplished simultaneously with the melting of the metals. The melting point of the metal is sufficiently FIG. 56. Excessive carbonization in a welding seam. high to destroy the oxides and as the metal flows to- gether directly when these substances are worked upon, there is no need of a flux in the welding of these metals (Figs. 52, 53, 54, 55, 56). In grades of iron, having melting points lower than that of the iron oxide, the fusing of this oxide can not possibly be effected as the temperature of the latter is al- ways kept down by that of the molten metal. In the welding of such mate- rials therefore, it is neces- sary to employ a welding powder, or flux, which is able to chemically destroy the existing oxides. The stirring with the welding bar during the welding operation is also advisa- ble as this tends toward a mechanical destruction of the oxides. (Fig. 57.) In the autogenous welding of mild steel it is of great importance to consider the state in which the carbon exists. As previously mentioned the carbon always exists in a fluid condition in molten iron and it FIG. 57. Method of stirring the molten metal with the filling bar during the welding operation to destroy the films of oxide. 62 AUTOGENOUS WELDING AND CUTTING is only when the metal becomes rigid that its condi- tion changes. In the case of mild steel the carbon content consists of pearlite. Martinsite. It is well known from the hardening treatment that by a process of sudden cooling and quenching, certain states of the metal can be lastingly obtained which otherwise only exist at higher tempera- tures. In the autogenous welding of mild steel there is always the danger that, in consequence of a rapid cool- ing, a liquid form of the carbon is retained in the iron, so that the welding seam assumes the character of steel. It is then possible that Martinsite will exist in place of pearlite. Martinsite is a substance which has the same per- centage of carbon as pearlite, but differs from the latter in its great hardness. If martinsite is produced, the welding seam of mild steel becomes hard and brittle and, therefore such changes of the material should be avoided. Welding of Cast Steel and Wrought Iron. In the 'welding of cast steel and wrought iron or similar combination which is frequently done in the manu- facture of certain articles, the peculiarities of each metal must be carefully considered. In the construc- tion of motor valves, for example, the spindle is made of wrought iron and the disk of cast steel, owing to these parts being subjected to different stresses. The union is effected by means of the autogenous welding flame in the regular manner. CHAPTER VIII REPAIRS OF GREY CAST IRON A VERY wide field for autogenous welding is the repair of broken cast iron pieces. As previously mentioned, grey cast iron is an alloy with a high per- centage of carbon and a still higher percentage of silicon and the presence of the latter causes the carbon to exist in the form of graphite. Formation of White Iron. Silicon has so low a boiling point that under the influence of a welding flame it evaporates and without special precaution, the percentage of silicon contained would be consider- ably reduced during the welding of grey cast iron. This would result in the carbon content assuming an- other form and white iron would exist in that portion of the material influenced by the welding flame. Owing to the characteristics of white iron, the welding seam would become hard and brittle. This phenomenon must be avoided and its preven- tion is of such importance that the author repeats its mention here again. The details of the correct treatment are given in the preceding chapter. Presence of Tensions. In grey iron castings, high tensions exist in the individual portions, due to the unequal cooling of the mass, during its manufacture and these tensions usually cause cracks if other forces later on influence the substance. Such latent tensions exist in the spokes of wheels at the point where the relatively greater mass of the rim 63 64 AUTOGENOUS WELDING AND CUTTING joins the thinner mass of the spokes. Attempts to weld such spokes, without the necessary preparation, would result in new cracks when the cooling down takes place. The proper method of execution is first to heat the rim so that it will expand and thus enlarge the fissure in the spoke. While the casting is in such heated state, the welding of the crack should be completed in the regular prescribed manner of welding such material (Fig. 58). Value of Preheating. In this manner, the stresses, which occur when the piece under treatment gets cold and shrinks, may be avoided. The pre-heat- ing of the material trans- forms such tensions into pressure strains which are much more favourable to the cast material. The co-efficient of tension for cast iron is 0.014%; i.e., for every increase of 100 C. in temperature, there is an increase in the mass of the object equal to 1.4 m/m for each metre length. As the melting point of cast iron is 1050 C. it is evident that the total expan- sion of the material from freezing point (0 C.) to the molten state is 1.4 x 10.5 or 14.7 m/m for each metre length. Expansion. The conductivity of cast iron is com- paratively low and as the stretching is distributed over the material within reach of the heating, it may be assumed that this tension value of 14.7 has to be di- FIG. 58. Locomotive drive wheel with cracks in spokes repaired by autogenous welding. REPAIRS OF GREY CAST IRON 65 vided by 2 in order to obtain an approximately correct figure. Therefore for each metre length (39.37 inches) of the mass heated, by a portion being raised to the melting point, a stretching of 7.35 m/m (19/64 inches) results, i.e. about 3/32 inches for each foot in length, and in the portions outside but rigidly connected to the welding area a crushing of the material for about 5 m/m occurs during the welding operation. FIG. 59 FIG. 60 FIGS. 5960. Broken motor cylinder and same after having been repaired by autogenous welding. The material which is thus compressed during the welding is also subjected to as equally great tension due to shrinkage of mass when cooling. This stretching in cast iron objects exists in two dimensions in a plane and in three dimensions in a solid. Prevention of Cracks. To prevent subsequent forma- tion of fissures, it is absolutely necessary to previously heat all material affected by the expansion or, better still, to heat the whole casting equally to a dull red, except where a loose piece is to be welded on one end only. The whole mass in this manner undergoes such a universal stretching that the local surplus of heat oc- casioned by the welding operation has no appreciable effect in expansion. 66 AUTOGENOUS WELDING AND CUTTING Repairing Complex Castings. For the welding of a complex casting, as for example, a motor car cylinder, it is advisable to bring the material into a dull red state by a slow fire, in a suitable furnace, so that the heat penetrates the whole mass. While the casting is in such heated state it should be removed from the furnace and the fissure welded FIG. 61 FIG. 62 FIGS. 61-62. Broken machine support and same after having been repaired by autogenous welding. as quickly as possible and then be immediately returned to the furnace so that it can be again heated as pre- viously, before being finally allowed to cool. It may be safely expected in the welding operations so executed that no tensions or formation of new fissures will occur in the cooling down process (Figs. 59, 60). Repairing Large Castings. When repairing broken corners of engine bases and machinery beds or similar REPAIRS OF GREY CAST IRON 67 work, the material in the welding area should be suit- ably prepared and the welding started in the middle part of the fracture and continued to either end. When one half of the welding has been completed the whole mass should be allowed to get cold before the remainder of the work is executed, for if this is not done the appearance of a new crack may be expected during the second part of the operation (Figs. 61, 62). In this treatise only general points of view can be given, but a welder will always be able with the as- sistance of these data, to determine whether the autog- enous method can be employed and how such repairs should be executed. CHAPTER IX WELDING OF SHEET IRON THE method employed in the welding of sheets of mild steel varies according to the nature and thickness of the material worked upon. In the welding of thin sheets the seam is exposed to different temperatures of the flame and, in consequence of this, a slow drop in temperature occurs immediately upon the metal becoming rigid, so there is no danger of the metal in the welding seam becoming brittle. The welding of very thin sheets such as a thickness of \ m/m (.02 inches) can be facilitated by turning up the edges of the sheets so as to leave a small flange of per- haps 3 m/m (.12 inches) in height at the place of union (Fig. 63). FIG. 63. Thin sheets flanged The application of the welding preparatory for welding. flame ^ ^^ flangeg simulta . neously serves to fuse one with another effectively join- ing the two sheets and in this manner the flanges, being melted down, replace the bar of filling material used in heavier sheets. This method of working is used in all cases where the manufacture of stamped work is accomplished by uniting sections of sheet metal, previously cut for the purpose. Also, in the manufacture of cylindrical sections, it is usual to leave a flange or rib, where the sheets are to be joined and then to melt down this rib on the cylindrical surface. 68 WELDING OP SHEET IRON 69 c In such work it is advisable to tack the pieces to- gether by welding the edges of the flange at intervals of about 100 m/m (4 inches) before melting down the whole flange. In the tacking process, the flanges are held together with clamps, in order to secure the correct relative position of the sheets. Flanging of Sheets. In the manufacture of stamped sheet-steel articles, the flange is formed during the stamping process. This method of flanging sheets at the welding place is extensively employed in the manufacture of thin sheet metal articles (Fig. 64) and also in the construction of large vessels where thicker sheets are used. The latter are usually vertical cylindrical tanks built up of sheets of varying thickness ac- cording to the different service conditions. As the pressure of the liquid contents of a vessel varies at different heights, sheets are employed according to re- FIQ 64 quirements and become thinner upwards from the bottom. If the edges of the sheets are turned at right angles for about 25 m/m (1 inch), the welding can be made upon the outer edges of the rib itself. In this case the double layer of sheet remains as a sup- port which serves to give the whole vessel greater strength and power of resistance. If the thickness of the sheet exceeds 3 m/m (J inch), it becomes necessary to bevel the edges, so as to allow a perfect welding through the whole thickness of the material. In this case however, it is necessary to em- Sectional views of stampings of thin sheet metal with flanges for welding purposes. 70 AUTOGENOUS WELDING AND CUTTING ploy other metal for supplying the material lacking to fill up the welding groove. For such purposes, it is usual to employ a soft Swedish charcoal iron drawn into wire. In welding thin sheets, it is advisable to keep the filling wire in the direction of the welding seam so that it is possible to melt it directly into the groove. For this process a certain experience is required but, if one is not too easily discouraged, he will soon acquire the proper way of doing this kind of work. Welding of Very Thin Sheets. If still thinner pieces of sheet are to be united, the edges are usually FIG. 65. Double hook FIG. 66. Diagram showing appli- used in welding of cation of heat-absorbing blocks very thin sheets. to prevent overheating in the welding of very thin sheets. hooked together by a hemming operation (Fig. 65). Before applying the welding flame the hem is super- imposed upon a block of material which possesses great heat conductivity and sufficiently large to be effective. As will be seen in the accompanying illustration (Fig. 66), the parts to be joined lie in a groove in the block and, as the material is in several layers, the welding can be carried out without danger of burning the metal. In performing this work the torch should be held at as sharp an angle as possible as, in that manner, a larger thickness of material is placed in the direction of the axis of the welding flame. In such operations, it is of advantage to make the heated areas of the material as small as possible as this prevents the material be- coming warped and distorted. Position of Welding Torch. As the sheets become thicker the position of the burner must be more ver- WELDING OF SHEET IRON 71 tical to the work. The correct adjustment of the flame is of great importance for these operations and great care should be taken to insure that the flame has neither an excess of oxygen nor of acetylene. It is also impor- tant that the material is struck by the flame in welding so that the inner cone of the flame is from 3 to 5 m/m (| to 3/16 inches) from the sheet. In the welding of sheets of from 2 to 3 m/m in thick- ness, the burner has to be so placed that it meets the welding seam approximately under an angle of 45. FIG. 67. Butting together the edges of sheets for welding purposes. This method is satisfactory for sheets up to 3/32 inch in thickness. FIG. 68. Bevelling the edges of thick sheets for welding purposes. This method should be used on sheets having a thickness of i inch or over. Often in industrial work, a thorough welding of the seam is obtained in sheets up to a thickness of 5 m/m (3/16 inches) without the previous bevelling of the edges of the sheets. This however is a matter of in- dividual ability and those who are not experienced in the autogenous welding process , should always bevel the edges of the sheets, if they are more than 3 m/m (Figs. 67, 68, 69). Unless thick sheets are bevelled, FIG. 6 9 . - Double bev- . ' ellmg of edges of very the union, in the groove of the weld- thick sheets (f inch ing seam, is not reliable and the or over ) for welding i u- u i j purposes. places which are not properly joined act as a fissure which permit the easy breaking of the weld. Failures of Welds. In different cases, such imper- fect welding has been the cause of the rupture of ves- 72 AUTOGENOUS WELDING AND CUTTING sels subjected to pressure and thence deductions were drawn unfavourable to the fitness of autogenous weld- ing in general. But this was of course perfectly errone- ous, as in these cases, the conclusion can only be drawn as to the imperfect way the process was handled (Figs. 70, 71, 72, 73, 74, 75, 76, 77). FIG. 70. Evidence of superheating of a welding seam. In the case of fire, or ordinary blacksmith welding, such imperfect welds will occur if the process is unskil- fully handled, and this will frequently be the case where thick materials are welded in a fire. In welding thick sheets of mild steel, the heat stored, in the adjoining parts of the sheet, is sufficient to pre- vent the welding seam from cooling down too rapidly and thus becoming hard or brittle. FIG. 71. Excessive superheating in lower part of a welding seam. Existence of Oxides. In the slow cooling of the welding seam, where films of the oxide remain in the mass, there is a danger that the temperature of the material gets below the melting point of these oxides before the latter are destroyed. These oxides, WELDING OF SHEET IRON 73 when included in the material, arrange themselves across the direction of the rolling of the metal and thus en- danger considerably the strength of the metal in the weld. FIG. 72. Evidence of superheating of a welding seam and unwelded spots (a. a.). In order to avoid such a condition, the following method should be employed in the welding of sheets that are later on to be subjected to heavy pressure. Before the welding operation is commenced, the material adjoining the parts to be joined should be heated up to red heat, by the welding flame, thereby surrounding the place of union with a zone of heated metal. FIG. 73. Superheated and carbonized welding seam containing for- eign matter (a. b. c.). As this heat is therefore conducted to the parts to be welded during the operation, it is evident that there is an increase of heat at the weld rather than a loss of heat which would occur otherwise. The weld- ing can then be effected with comparative rapidity 74 AUTOGENOUS WELDING AND CUTTING as the material welded remains under the influence of the welding flame a much shorter time and the danger of the temperature of the metal falling below the melting point of the oxides is avoided. FIG. 74. Imperfect, superheated, and carbonized welding seam. Magnetic Properties of Iron. Iron has the pecu- liarity to lose its magnetism at a temperature close to 700 C. or 1300 F. In the welding of heavy sheets which are afterwards subject to exacting conditions, the welded parts should be heated by the flame after the welding operation is completed. Such subsequent heating has the effect that the structure of the material receives an im- portant refinement. FIG. 75. Fracture in a welding seam as the result of improper welding. In such a procedure it is necessary that between the heating immediately previous to the welding and the exposure to the flame subsequent to the operation a complete cooling down to a temperature not to exceed 20 C. (98 F.) occurs for effective results, The WELDING OF SHEET IRON 75 second heating should raise the temperature of the welded part to not less than 700 C. or 1292 F. FIG. 76. Unwelded place in seam (a a) in consequence of improper holding of the burner. Value of Reheating. For example, in two welds made in the same sheet, with equal care and under similar conditions, the difference in results may be easily recognised if one is allowed to cool down com- pletely and the other is reheated by the flame after the temperature lowers to approximately 20 C. or 98 F. Upon breaking the two welding seams, it will be found that the fracture of material of the welding seam, which has not been heated the second time, is composed of coarse crystals, while the fracture of the FIG. 77. Example of bad welding. reheated weld will consist of fine grains with fibres running through the metal. This change of material takes place at the temperature at which the iron loses its magnetism and it would mean a loss of energy and heat if the second heat exposure is continued to pro- duce a higher temperature than is absolutely necessary. 76 AUTOGENOUS WELDING AND CUTTING A process has, however, been developed which makes it possible to prevent a superfluous heating of material during the second exposure and to prevent the loss of heat and time consequent upon it. Test of Magnetism. By taking a common horse- shoe magnet (Fig. 78), the testing of the magnetic properties of the welding spot during the second exposure can be accom- plished. As soon as the magnetism disappears, the heating of the welded area should cease. Such second heating of the welding seams should be carefully done in all sheets which are later on subjected to pressures, especially in the repairing and manufacturing of steam boilers. Puddling Process. In welding heav y material which is later on sub- the magnetic prop- jected to exacting conditions, it is nec- t s essary that the welding seam during its creation be subjected to a process of refining which corresponds to the process known in steel works as " puddling." After due preparatory heating, the workman starts welding in the bottom of the V shaped groove formed by the two bevelled edges, but he must be sure that the welding flow shows a smoothness in the bath. Contents of oxide betray their presence by a somewhat darker condition in the fused material which may be noticed by a trained eye. When the welder notices a darker spot in the molten material he should turn the effective part of the welding flame upon it so that the oxide may be reduced to metallic iron. After the welder has built up the lowest part of the welding trough to a thickness of 5 m/m (3/16 WELDING OF SHEET IRON 77 inches), he starts gently hammering the molten metal by a small hammer with piens of such shape to enable the metal to be reached at the base of the groove (Fig. 79). The playing of the welding flame simul- taneously with the hammering is continued during the building up of the welding seam to its full thick- ness and it corresponds to a kind of puddling. During this operation it is necessary to cool the head of the hammer from time to time, by im- mersion in water, and thus prevent its destruction by the flame. Improvement in Material. By these means, densification of the material and an increased strength is obtained. After the whole weld- ing groove has been built up with filling material, it is common prac- tice to effect a smoothening of the surface by using a small hammer, with a contact of not to exceed 8 m/m, which hammer may also be plunged in water for cooling. It is essential to successful operation that this kind of hammering is done while the welding seam is at a bright red heat. If the welding seam is worked upon, while at a temperature below the red glow of the material, or with a larger hammer, internal fractures of the metal occur which damage the welding seam. Upon the right kind of hammering, the quality of the welding seam depends to a large extent (Figs. 80, 81). Use of Two Welding Torches. In the case of very thick sheets, the welding may be performed by welding flames on both sides of the sheet operated simul- taneously, but great care and strict observance of the FIG. 79. Puddling hammer. 78 AUTOGENOUS WELDING AND CUTTING above mentioned rules is necessary for satisfactory results. The edges of the sheets must be bevelled upon both sides and the welding will be performed to the best advantage with the sheets in a vertical or horizontal position (Fig. 82). FIG. 80. Photograph showing disappearance of burned par- ticles which had been contained in the welding seam. While there is always a mass of molten metal which would flow back into the groove formed, when the welding flame is played from above, a dropping away of the molten iron will occur in vertical welding and in consequence great difficulties arise in such work. FIG. 81. Photograph showing disappearance of burned particles which had been contained in a double-sided welding seam. Vertical and Overhead Welding. In executing vertical welding, or when a workman, tying on his back, has to weld the sheet from underneath, the drop- ping away of the molten iron can be prevented in the following manner: The area adjoining the welding place is heated until the metal is white hot and, when this condition is secured, the flame is played upon the weld while simul- taneously the filling wire is inserted in the welding groove. At such a high temperature, the adhesion of the material influences the molten portion of the filling wire so that the latter spreads itself out upon* WELDING OF SHEET IRON 79 the surface of the material, in homogeneous compound, and thereby the formation of drops is avoided. FIG. 82. Double weld in a very thick mild steel sheet. It is in this manner that experienced welders are able to execute, with equal ease, the repairs of boilers in any and every position that is required. CHAPTER X MANUFACTURE AND REPAIRS OF BOILERS THE autogenous welding process is variously applied to the repairs of boilers. In such work the strains imposed upon the places to be repaired have to be carefully considered, since, under service conditions, the material of a boiler is subjected to constant alter- ations resulting from changes of temperature and position. Effect of Temperature Variations. The structural appearance of mild steel sheets varies with the temper- ature of the metal. The same material, which is coarse grained in a cold state, will be finely grained and fibrous at the usual service temperature of modern boilers of 200 C. to 300 C. (392 F. to 572 F.). This is the reason why the power of resistance in the material of boilers is always greater at certain higher temperatures. FaMures of boilers often result from the usual manner of joining of overlapping sheets which consists of pier- cing the two sheets and inserting rivets. In the fur- nace, for example, the sheet exposed to the flame acts as a receiver of heat, and the second sheet as a con- ductor of heat, the double thickness of sheet somewhat retarding the passage of heat to the water. Causes of Failures. If the one sheet is much heated by the flame it must expand to a greater ex- tent than the other sheet, which is kept nearly of the same temperature as the water around it. In a cold state, the connecting rivets will stand parallel 80 MANUFACTURE AND REPAIRS OF BOILERS 81 to each other, but, when the two sheets are heated to unequal temperatures, a straining of the rivets will occur, since they pass from a parallel to a converging position. Further while the boiler is in service the inner surface of the fire tubes will remain of nearly equal tempera- ture so long as the fire door is kept closed, but each time the door is opened a cold air current will enter the fire tube and cause the material to cool down and shrink. These fluctuations of temperature impose con- siderable strains upon the material, but particularly upon the rivets. It is apparent therefore that the rivet holes must eventually become oval shaped and permit the water to enter the unoccupied space causing a corrosion of the material, which defects finally assume such pro- portions that the boiler has to be taken out of service. Change of Methods. As other methods of join- ing sheets were unknown, in the beginning of the boiler making industry, it was necessary to employ rivetting notwithstanding these defects. The process has been so developed and perfected that it will now be rather difficult, if at all possible, to replace the rivetting of boilers by autogenous welding. When a method of examining an autogenous welding seam has been devised by which the quality of the seam can be reliably determined without injuring the metal, it is probable that the welding process will be more generally employed in the construction of boilers. For the present, however, such welding method furnishes an economical and reliable means of repairing the corrosions and fractures which occur in boilers, during their use. To repair worn rivet holes, the adjacent rivets must be removed for a distance of from 300 m/m to 500 82 AUTOGENOUS WELDING AND CUTTING m/m (12 to 20 inches) in order to permit the material to stretch freely during the local heating caused by the welding and also to permit a free shrinking during the cooling down of the metal. Welding of Cracks. The same applies to the welding of cracks. Cracks in boiler sheets are usually caused by bending strains on the material consequent upon alternate internal pressures, and they are quite common in the places where such strains exist. When a crack is to be welded autogenously suitable preparation must be made to prevent the expansion of the adjoining portions of the sheet toward the weld- ing seam. As the metal has to be transformed into a plastic and liquid state, it is evident that such ex- pansion would result in the material of the welding seam being compressed and forced out during the operation. Crack welding executed in this manner would cause, during the cooling period, a shrinkage of the material in direct relation to the fall of temperature. The welded place would be compelled to stand such an extraordinarily strong pull as to be torn open again. Avoidance of Strains. It is therefore very neces- sary that subsequent strains in the welding seam during the cooling down process be avoided. In welding a crack in a boiler sheet it is advisable, after the nec- essary cutting away of the material, to drive a chisel or other wedge into the fissure to further expand it, in which case tension will exist in the adj oining portions. If, while such tension exists, the welding is completed to the place where the chisel is inserted, a pressure on the adjoining material must result, instead of a pull, when the chisel is removed. It is then possible to en- tirely weld up the place of the fissure in which the chisel was placed without fear of another fissure forming. MANUFACTURE AND REPAIRS OF BOILERS 83 Benefit of Preheating. Another very satisfac- tory method is for the welder to heat the edges of the fissure with the flame until they become plastic and then proceed to heat the adjoining portions of the sheet. The result is that the metal expands toward the edges of the fissure and in consequence, the plastic material is pressed out. The sheet is then allowed to cool down completely and the unfused material returns to its original position, leaving a wide slot-shaped opening in place of the crack. When the cooling down is completed, the welder, by inserting the filling bar into the middle of the slot and welding a small central portion, is then able to proceed with the welding from either end of the fissure toward the centre. In this case, the filling bar, which is molten in, takes the place of the chisel in the pre- viously mentioned process. To prevent the crack from extending further a hole should be drilled at each end. Welding in Patches. Cracks in boilers usually occur where the material has to give way to a bending strain in a certain direction and if it can be avoided, the welding seam should not be placed in the line of such strain. It is more advisable, in many cases, to cut out a part of the boiler sheet and insert a new piece instead of welding up a fissure, which piece should be inserted so that the new material occupies a position in the line of strain. In the welding in of a patch, it is also of advantage to avoid sharp corners in the piece applied, as such corners often serve as a starting place for other fissures. The corners should therefore be rounded off and those of the piece applied be fitted in a corresponding manner. Method of Welding. In welding in such a piece it is necessary to start the welding from a definite 84 AUTOGENOUS WELDING AND CUTTING point usually in the centre of one side, and to weld from this centre to either end of the straight line. The subsequent welding must be on the side adjoining the first part so that in a quadrangular piece the two sides forming an angle are welded first. The whole piece should then be allowed to cool and into the middle of the angle which is not yet welded, a chisel should be driven and the material forced apart. Or, a filling bar should be welded in so that the stretch- ing of the material, in the welded in piece, is prevented during the latter part of the operation. The welding of the last side is identical with the method of welding a fissure described above. Advantage of Dishing. In such repairs, the piece of sheet which is to be inserted may also be somewhat "dished" in the centre and if a piece so prepared is welded into a boiler shell it will be found that the " dished" part becomes straightened upon cooling, in which manner tensions are prevented. Of course, such welding procedures of importance must only be entrusted to workmen with experience on similar work and if possible only to those who have been trained for repair work on boilers exclusively. Puddling Process. In executing this kind of work, the adjoining portions of the sheet should be heated to effect a transfer of heat to the welding place from the ad- joining portions instead of allowing a loss of heat. In boiler repair work the welder can also, with advantage, employ the previously mentioned " puddling" process where the metal is worked by means of small hammers in conjunction with the application of the welding flame. A very common operation is the repair of furnaces, as frequently the corrugations of the furnace tube, with the use of certain water, have corrosions formed of sufficient depth eventually to render the boiler useless. MANUFACTURE AND REPAIRS OF BOILERS 85 Repairing Corroded Tubes. These corrosions are often found in great numbers on the water side of fire tubes and furnaces. The welder during such work should keep the fire door and chimney of the boiler closed to prevent the cooling down of the material by an occasional air current, which would spoil the suc- cess of the welding. This work puts great physical strains upon the welders and in many cases these operations must be executed by two alternating gangs of workmen, the working periods often not exceeding 20 minutes. It is of great importance that such work be completed without interruption as otherwise strains occur, and other con- sequences follow, which are injurious to the welding. CHAPTER XI MANUFACTURE OF CYLINDRICAL VESSELS IN welding the horizontal seams in cylindrical sec- tions of thin sheets, it is of advantage to employ a rail- way rail or similar device in the top of which a slot is cut lengthwise about 20 m/m wide by 5 m/m deep (about f x 3/16 inches). The rolled sheet is placed upon the FIG. 83. Method of using supporting rail in welding longitudi- nal seam in a cylindrical section of thin sheets. Also diagrams showing two methods of flanging the sheets for welding. rail in such a manner that the flanges to be joined lie in the middle of this slot while the sheet itself is imposed upon the rail top at either side (Fig. 83). During the welding process, the major part of the heat supplied to the sheet is thus conducted into the top of the rail so that undesirable stretchings or warp- ings of the sheet are prevented. In such welding rails MANUFACTURE OF CYLINDRICAL VESSELS 87 there is also special apparatus for carrying the sheet along during the operation. Welding of Horizontal Seams. In the welding of cylindrical sections of heavy sheets, it is necessary to take the expansion into careful consideration. If two sheets are to be welded lengthwise, local stretch- ings of the material adjacent to the welding seam will occur in consequence of the heat conducted from the welding flame. This expansion disappears again when the welded mass cools down. If the sheets are convexly inclined to each other, there will be two components of force acting from either side towards the welding place as a result of the expansion of the sheets. The material at the welding place is thus compressed and is lacking when the mass cools down and shrinks. At the same time a warping of the sheet edges occurs in front of the welding place, and so it may easily happen that the edges are pushed one above the other, in front of the welding seam. In such a condition the article is useless and un- serviceable, for if attempt is made to bring the sheet back to its origi- nal position by inserting a pin in front of the welding seam the re- sult will be that the entire section will become distorted. This phenomenon can be easily Fl ?- 84 r~ Dia s ram /ing sheet prepared for reproduced if one punches a hole in demonstration of ten- the middle of a sheet and severs ** produced during the welding operation. the sheet trom the hole to one edge. By heating the area around the hole, the area of the cut will be converted from a rectangular to a trian- gular shape (Fig. 84). If the welding proceeded from the edge to the hole, 88 AUTOGENOUS WELDING AND CUTTING the welding at the sheet edge however good, would always burst open as the welding approached the mid- _ die of the sheet (Fig. 85). For this reason it is necessary to keep open that portion of the sheet which is opposed to the place where the welding begins. It is, therefore, best to insert a FIG. 86.- Diagram show- drift in b means of which it j ing the effect of expan- sion in a sheet under the always possible to bring the sheets into the P^Per relative position. This pin has to be moved on as the welding proceeds and is finally removed only when it is necessary so that the welding may be finished (Fig. 86). Welding of Circumferential Seams. Similar pre- cautions must be taken in the welding of circumferen- tial seams, as it is beneficial to place the edges of the FIG. 86. Method of preserving the correct alignment of the edges of sheets during the welding operation. sheets at a distance of about 2 to 5 m/m (.08 to .2 inches) from one another according to the thickness of the material. This is best accomplished by securing the sheets with clamps so placed as to preserve the MANUFACTURE OF CYLINDRICAL VESSELS sheets in correct posi- tion for welding pur- poses. correct alignment and also to keep them the proper distance apart (Figs. 87 and 88). In this position, the sheet sections should be tacked together between the clamps by melting down filling material every few inches in order to give the mass a firm position. When this has been done, the seam can be safely FIG. 87 Use of clamps , . for holding edges of welded without fear of cracking or warping, for the material of the sheets is then placed at a constant distance from each other and the movement of one can- not handicap the movement of the other. Device for Welding Heavy Sheets. Where large and heavy sheet sections are to be made, it is of advantage to employ a stretching ring, of U shaped cross-section and a radius some- what less than that of the in- ner area of the sheet section (Fig. 89). FIG. 88. Diagram show- ing use of jig for main- taining correct alignment and distance during the welding of vertical cylin- drical sections. in . . ,, ,, . , tensions during the heads shall each be 1| times the thick- operation of weld- ne ss O f the cylindrical sheet, ing on a head. T i_-fj_ * r\ TTJ.I Liability of Corrosion. If the vessel manufactured by this method stands upright dur- ing use, the welding seam will be situated at the ex- treme lower end of the vessel. As some allowance must always be made for the existence of surface moisture, it is possible "that premature corrosion may occur in the seam, sufficient to damage the vessel. The following method has been evolved to prevent such a defect and at the same time secure increase in strength. The method consists in heating the two lower edges of the sheet of the cylindrical vessel and its bottom by the welding flame after the bot- tom has been inserted. The ap- plication of heat permits the closing in of the edges of the sheets toward the centre, in FIG. 99. Drawing in the , i ! f jv edges of a raised cylinder the shape of an arc, and when head for the purpose of in- the proper contour has been se- creasing the strength of cured, the welding can be pro- ceeded with in the usual manner. In this way the edge of the outer sheet is so drawn around that it absorbs a part of the strain caused by the internal pressure of the vessel (Fig. 99). MANUFACTURE OF CYLINDRICAL VESSELS 97 The welding seam at the base of such vessels can be removed beyond the reach of corrosion, due to the collection of moisture around the exterior, by welding an angle iron ring on to the ves- sel below the welded area (Fig. 100). The proper way to manufacture such vessels consists, however, in insert- ing the top, as well as the bottom, in such a manner so that either welding seam is FIG. 100. Angle-ring welded on placed in the cylindrical part and this method has been the bottom vessel. of a cylindrical generally accepted in such industry. When a vessel thus manufactured is to be used in a vertical position, it is advisable to weld an angle iron ring to the external shell of the lower head to serve as a support to the vessel (Fig. 101). If it is desired to apply either head of such vessels somewhat inside of the cylindrical portion, the diameter of the head, which has to be an ex- act fit, should be made slightly larger than the diameter of the shell. The outer sheet should then be heated externally so as to expand and per- mit the head to be easily inserted. FIG. 101. Support . J ... ring applied to a ver- The welding should be done while tical cylindrical ves- the external surface is still hot as, sel. otherwise, there would be danger of the welding seam bursting during the welding process. O 98 AUTOGENOUS WELDING AND CUTTING Applying an Intermediate Head. It sometimes becomes necessary to weld an intermediate head into a cylindrical vessel in a place that is otherwise inac- cessible. Except in the case where particular strength and lightness are required, a flanged head can be placed within the cylinder into which a number of holes have FIG. 102. Inserting an inter- mediate head in a cylinder by means of hole-welding. FIG. 103. Inserting an intermediate head by cutting the cylinder into two sections. been previously drilled. With ordinary care, the oper- ator can, by inserting the torch through the holes, weld the inner intermediate head to the surface of the external cylinder shell, after which, the holes can be welded up (Fig. 102). If the intermediate head has to be fitted absolutely tight and capable of resisting heavy pressure, it is advisable to cut the cylinder into two sections and to then place the head in position between them. By bevelling the edges of the sheets of both sections of the shell, the sections can be placed in the proper posi- tion and the welding executed in the usual manner (Fig. 103). CHAPTER XII MANUFACTURE OF RECTANGULAR VESSELS AND MISCELLANEOUS ARTICLES IN the manufacture of cylindrical or dome shaped sheet vessels the expansion of the material can be absorbed without extensive deformation, but this is not the case where rectangular bodies are to be made. Avoidance of Excessive Expansion. The proper welding of flat sheets makes it imperative to avoid excessive- heating of the material during the welding process, or to localize such heat upon those places which are not flat. The latter effect is obtained by providing the sheet body with a flange at the joining place, and then to weld upon the upper edge of this flange. Position of Welding Torch. If the welding is to be done in the corner of a rectangular vessel, it will be necessary to place the burner as much sideways as possible, in the direction in which the welding is to take place. It is thus possible to reduce to a minimum the amount of heat conducted into the adjoining flat parts of the vessel. If the burner were kept vertically upon the welding seam, the flame jet would be parted at the edge and thereby considerable areas would be heated and stretched so as to render warping of the sheet unavoidable after the cooling down. Location of Seams. If such a sheet is at an angle from the other sheet, it is advisable to place the union in the straight portion, at a distance of about 10 m/m 99 100 AUTOGENOUS WELDING AND CUTTING FIG. 104. Method of welding on the cover of a rec- tangula r sheet ves- sel. (f inches) from the edge. Also to keep the position of the burner, during the welding operation, so that the jet does not flatten itself upon the flat part, but plays against the corner. The position of the burner is very essential for avoiding a warping of the sheet. In welding on a cover, or head, it is advisable to cut the cover larger by about 20 m/m (f inches), and to bend a flange of about 10 m/m (| inches) in width, as this permits the welding to be effected with the welding flame directed towards the flat part of the cover. Manufacture of Safes. In many industrial branches, as, for instance, the manufacture of safes, distortion of the sheets is not permitted. If, in such cases, the welding seam has to be placed in the corner, a heavy cop- per plate of sufficient dimensions should be laid upon the cover which is to be welded. The vertical sheet should also be covered with a heavy copper band placed below the weld- ing seam (Fig. 104, 105). By this arrangement, the excess heat during the welding operation passes from the seam to the copper plates, owing to the great heat con- ductivity of such metal, and the stretching or warping of the sheets is avoided. Superheaters. Autogenous weld- ing is adapted for many purposes in the manufacture of heating appliances, as it provides an excellent means for joining the various parts, after they have been stamped, or cut, out of sheet metal, where FIG. 105. Application of heat- absorbing plates to prevent the warping of the sheets of a rectangular ves- sel during the welding operation. MANUFACTURE OF RECTANGULAR VESSELS 101 rivetting would be unsatisfactory. This is true of super- heating devices where the liquid or gas conducted through them is divided into the thinnest possible layers, in order that the higher heat ^__ otherwise given to the metal can be transmitted to the liquid or gas, so that the latter may be- c o m e superheated accordingly (Fig. 106). Radiators. Ra- diators for house heating or similar FIG. 106. Tube sheet of superheater with autogenously welded pipe connections. apparatus of the most varied types, which are kept at a pre-determined temperature by circulating water or steam, are also manufactured from sheet metal by this method at considerable less cost than by methods for- merly employed (Figs. 107 and 108). In fact, the stamping out of pieces of sheet metal, the flanging of the edges of the plates to be welded and the welding of them, employs numerous designs of machinery and, not only now forms an important industry, but extensive developments may with reason be expected in the future. Automobile and Aeronautical Motors. A strik- ing example of the scope- of this work is the automobile motor shown in the accompanying illustration (Figs. 109 and 110). This is composed of two steel tubes, for the cylinders, and several stamped sheet metal pieces welded together to form the water jacket and fittings. 102 AUTOGENOUS WELDING AND CUTTING FIG. 107. Portion of a ra- diator showing manner in which the individual sec- tions are welded together. FIG. 108. Radiator construc- ted from sheets by means of autogenous welding. FIG. 109 FIG. 110 FIGS. 109-110. Two views of a motor cylinder made of stamped sheet sections autogenously welded together. Such motor cylinders have a distinct advantage over those with cast iron bodies in that they possess greater strength with considerably less weight and the defects and service cracks experienced in cast iron cylinders are entirely avoided. Motors with any number of cylinders can be manufactured in this manner. MANUFACTURE OF RECTANGULAR VESSELS 103 The stamping and welding method thus renders possible the production of articles of the most varied types and in each case it is a matter of determining the approximate cost, to decide upon the method to be employed. When making sheet metal vessels it is often necessary to apply fittings for pipe or similar connections. For- merly this was accomplished by rivetting a suitable casting, or forging, on to the body, but such connec- tions have many technical deficiencies. Application of Pipe Fittings. This form of connec- tion has been replaced by the welding on of a boss of whatever metal is required for the purpose. In the production of this work, an experienced welder FlG . m ._ Boss welded Can build the boSS Of SUCh shape on a sheet vessel for and in such a manner that subse- pipe co ectio11 - quent surface finishing is unnecessary (Fig. 111). By boring a hole through the boss and the body sheet, which are then fused together, and cutting the necessary thread, a thoroughly satisfactory connection is secured into which the requisite pipes can be applied. Manufacture of Double Shell Vessels. For many industrial purposes vessels with double shells are employed as, for example, those which are heated by steam or hot water introduced into the interlying space between the two shells. The manufacture of such vessels has been much simplified by means of autogenous welding (Figs. 112-113). The upper edge of the inside vessel should be bent toward the outside by means of a flanging machine, or by the hammering process, so that the outside diameter of the flange is equal to the outside diameter of the other vessel. The flanged portion of the inner vessel can then be welded to the edge of the outer 104 AUTOGENOUS WELDING AND CUTTING FIG. 112. Double-shell vessel. FIG. 113. Vessel with double bottom. vessel and undue tensions need not be feared in this operation. Open Sheet Metal Vessels. In the manufacture of open semi-circular sheet vessels, where the bottom and the sides are made out of one sheet, considerable economy can be effected by cutting out the corner in a similar manner to that shown herewith. The sheet, so cut out, can then be formed so that the edges of the end plate and the edges of the sides come directly against each other and can be welded in the usual manner (Figs. 114-115). n FIG. 114 FIG. 115 FIGS. 114-115. Diagram showing method of developing the corner of an open vessel made from a flat sheet by autogenous welding. In actual practice, considerable difficulty is often experienced in the manufacture of cooking and similar utensils, resulting from the application of the spout. MANUFACTURE OF RECTANGULAR VESSELS 105 When the spout, which has previously been made from two stamped pieces, is welded on, the sides of the ves- sel expand and thus cause blisters which spoil the gen- eral appearance. Cooking Utensils. If the hole cut in the vessel, at the place where the spout is f to be fastened, is of smaller diameter than the spout to be applied, the material can be drawn out so that the outer edge fits exactly with the con- necting edge of the spout. The welding on of the spout can then be not only more easily, FlG . n 6 ._ Method of apply- but more neatly, done, as the ing a spout to a tea kettle place of welding is more acces- sible and the production of mis-shapen vessels is also avoided (Fig. 116). Ornamental Articles. In addition to kitchen uten- sils, various special articles are manufactured as, for example, handles of ornamental vases of the most variegated kinds. Shells of pressed sheets are made for the handles of canes and umbrellas. These are later brought upon the market, after they have been enameled, engraved and inlaid with gold, silver and mother of pearl. The welding method is also used for the manufacture of latch keys, door handles, window handles, gas stove appliances, apparatus for heating by the exchange of counter currents, connections for tube conduits, pistons, pedals for bicycles and articles of similar nature. By means of autogenous welding the manufacture of many articles is made possible from standard shapes and sizes of commercial iron and one need only refer to one of the most important articles, as an illustration. 106 AUTOGENOUS WELDING AND CUTTING Window Frames. Iron frames, for windows and doors, are used in very great quantities, in factory build- ings. A simple frame of angle iron, such as is generally used for these windows can be made by taking the necessary length of iron and cutting out a portion of one side, at each ^ corner to be made, as shown herewith (Fig. 117). 1 ==s=4 The frame is heated at each FIG. 117.- Method of cutting lace and bent to & ^ M j away an angle iron in the manufacture of a window SO that the Outer portion re- frame by autogenous weld- mains compose d o f undamaged material. The places of con- tact, formed by the bevel so cut at the corners, are then welded together autogenously and also any individual window braces that may be desired. If there is sufficient length of iron for the entire frame, all of the cutting away for corners can be first accomplished and when the iron has been properly bent the welding can be conducted without interrup- tion. Such work is also adaptable to armored con- crete, and in other various ways, in the building trades. CHAPTER XIII MANUFACTURE AND INSTALLATION OF LARGE PIPES AND CONDUITS FOR the manufacture of large and heavy pipes, by autogenous welding, the ruling items have been fully dealt with in the manufacture of cylindrical bodies. This field of application is very extensive, as large capacity pipes are often required for the most varied purposes. A simple tee connection is made by cutting the nec- essary hole in the main pipe somewhat larger than the diameter of the pipe which is to be applied. Application of Tee Connections. The end of the branch pipe, which has been previously flanged, is closely fitted to the contour of the outer surface of the main pipe and then they are welded to- gether (Fig. 118). A better practice, however, is to make the hole in the main pipe somewhat smaller than the diameter of the FIG. 118. One method of ap- plying a tee connection on a large pipe by welding. branch and then turn the edges of the sheet outwards, so that the pipe welded on fits straight on to the edges thus turned up (Fig. 119). A branch made in this manner is not only more neat in appearance, but is also of considerably greater 107 108 AUTOGENOUS WELDING AND CUTTING strength, as the welding seam is not subjected to the internal strains as in the other method. Further for conducting gases and liquids, this latter practice is to be preferred, as it prevents the formation of eddies in the sub- stances flowing through the pipes. Making of Large El- bows. An elbow for a FIG. 119. Another method of welding large capacity pipe is a tee connection on a large pipe. (This j i method is recommended in preference made b Y ^paring a to that shown in the preceding illus- number of pieces, which are longer on one side than the other, and uniting these segments by welding the circumferential seams so that shortest lengths lie in a horizontal line (Fig. 120). FIG. 120. Large pipe elbows made from several sheet segments by autogenous welding. Another way to make an elbow in such pipes is to take the piece of pipe of sufficient length for the bend and support it between two parallel blocks. Then heat the material on one side, by means of one or more LARGE PIPES AND CONDUITS 109 welding torches, until it is stretched on that side through greater expansion. By continuing the heating the material continues to stretch on the heated side causing this side to bulge. At the proper time, the parallel support of the pipe is removed and a contraction of the pipe, on the inner side of the bend occurs, thus forming a regular pipe elbow. This method is much employed, with great success, in the pipe making industry. When erecting pipe conduits it is necessary to take care that the connections are made in fairly large sec- tions and this is attained by using flanged screw con- nections, at regular intervals. Welding on of Flanges. The fixing of such flanges on to the pipe wall is either, through threads cut into the piping and in the inner surface of the flange, or by the rolling in process, or by means of welding. With the welding method, it is necessary, to recess the inner bore of the flange on a lathe so that the flange can be firmly welded on to the pipe end. Where it is practical, a collar can be turned in the walls of the pipe immediately behind the flange (Fig. 121). In the regular manufacture of flanged pipe by means of the weld- ing process, it is customary to use a flange with a collar of the same di- FlG> ameter and approximately the same thickness as the walls of the pipe. The edges of this collar are united with the pipe by means of autogenous welding. Experiments have proved that the welding on of a flange, if properly executed, will resist greater pressure 121. Pipe and flange bevelled pre- paratory to welding. 110 AUTOGENOUS WELDING AND CUTTING than if the pipe is threaded, or rolled in, and the joint made in this manner is absolutely gas and water tight. When erecting pipe lines, one must also bear in mind, that expansion and contraction of the piping will occur according to the changes in temperature to which they are subjected. Compensation Couplings. These changes are over- come by inserting compensation sleeves in the conduit at desirable places. Such parts not only increase the cost of the piping, but necessitate also considerable space, which is not always available, particularly in the case of large capacity conduits. FIG. 122. Expansion coupling welded between pipe flanges. In ship building for instance, the space, which exists between the sheets of the double bottom, is used for accommodating such pipings. Having regard for the large number of conduits, which are required in this case, the question of accommodating the com- pensation sections causes the builder- serious difficulties. These connections are often made to advantage by means of autogenous welding by making the bends out of several segments, in a similar manner to the above mentioned pipe elbows. LAKGE PIPES AND CONDUITS 111 Corrugated Sections. There is a very simple means of avoiding these compensation couplings altogether, i.e., by inserting into the conduit at intervals short pieces of piping, which have been provided with cir- cumferential corrugations on a rolling mill (Fig. 122). Such sections are very similar to the Morrison or Fox furnaces used in steam boiler construction and these corrugations provide sufficient elasticity to accommo- date the expansion and contraction of the piping, re- sulting from the changes in temperature. Bends inserted at intervals also serve to nullify the effects of the changes in the material which, in con- junction with the corrugated sections, eliminate the difficulties resulting from temperature variations. CHAPTER XIV MANUFACTURE AND INSTALLATION OF GAS AND WATER PIPE THE manufacture of gas and water pipe furnishes a field for autogenous welding, which has now assumed great proportions. This includes pipes of all diameters up to 4 inches. The method previously employed, in such manu- facture, consists of cutting the sheet metal of the re- quired length and width and heating the strips, in a special furnace, usually a gas oven, uniformly to the welding temperature of the material. When this tem- perature has been reached the strips are drawn, direct from the oven, through suitable dies in a tube drawing machine, which form the strips into the shape of a tube. Previous Method of Manufacture. As the ma- terial is cooled down, during this operation, to a tem- perature below the welding point, it is necessary to return the partly formed pipe to the oven for re- heating and then repeat the drawing process, with the exception that a smaller die is employed. During this operation, the edges of the strips are forced against each other, pressed firmly together and thus thoroughly welded. This method of manufacture was adopted when "puddled" iron was in general use and, in order to obtain a good weld, two, and even three, drawings were necessary to secure satisfactory results; a smaller die being used at each successive operation. In this work, ordinary fire welding is used and the reliability of 112 GAS AND WATER PIPE 113 such welding is dependent upon the overlapping edges reaching the proper welding temperature throughout. Although the pipe drawing is an exceptionally quick operation, local coolings of the material often occur as the result of currents of air in the room, caused by the opening of a door or window, and as a consequence the welded section is not as perfectly homogenous as is desirable. The existence of poor welds is often in evidence when the material opens during the process of cutting threads. Use of Mild Steel. With the introduction of mild steel into modern manufacturing, a new material was available which was gradually adopted for the manu- facture of gas and water pipe. The structure of mild steel is, however, quite different from that of pig iron and during the drawing operation considerable difficulty was experienced with the material breaking off at the drawing tongs, or fracturing at the die. Adoption of Rolling Method. For this reason, the tube mills gradually abandoned the drawing method, in pipe manufacture, and adopted pipe rolling machines, whereby the pipe was formed from a strip of sheet metal 1 , by being passed through a series of profile rolls (Fig. 123). The rolls used in these machines varied in size owing to the expansion of the material in them due to the increase in temperature while in operation. This constant expansion and contraction eventually produced breaks in the grips of the rolls, which had a bad influence on the product and made it necessary to adopt water cooling so that the rolls could be kept at an even temperature. Other difficulties, however, were introduced, for when the strips, at welding heat, were run through a series of water cooled rolls, the tem- perature of the metal was so reduced that the welding was not entirely satisfactory. 114 AUTOGENOUS WELDING AND CUTTING The foregoing serves to illustrate the reasons for the development and application of autogenous welding in the manufacture of mild steel pipes and the extensive adoption of such method by tube manufacturers. FIG. 123. Pipe rolling machine. Autogenous Welding Process. In this method, the strips of sheet metal are first run through a rolling machine, to be formed as a tube, the two edges of the strip butting together in place of overlapping. They are then placed in a special welding machine equipped with several sets of rolls properly adjusted so that the edges of the strips are conducted under a fixed welding flame and thoroughly fused together. The union of the metal for the proper dimension of pipe is secured by means of a set of welding rolls situated immediately behind the flame (Fig. 124). Defects to be Avoided. In the rolling of such pipe, it is evident that a V shaped groove must be formed, where the edges of the strip butt together, GAS AND WATER PIPE 115 as a result of the varying stresses on the material and if the edges are fused into this groove, a flattening of the outer diameter will exist at the welding point. This lack of material will become evident when the pipe is threaded, especially in thick-walled pipes, and it is absolutely impossible to fuse in supplementary material in this process. To avoid this difficulty, in the ordinary pipe rolling machines, the edges of the strips are pressed off at an angle according to the radius of the pipe to be made. In this manner, the upset ma- terial at the edges of the rolled strips is fused during the weld- ing operation and con- tributes to improving the quality of the pipes. In some of the tube- welding machines, a side pressure is ex- erted, during the weld- ing process, by a pair of rollers forcing the tube together, causing FIG. 124. Pipe welding machine equipped a combination of the with mechanically operated rolls. processes of autogenous and fire welding within the seam. Welding Speed. The usual pipe welding machines are arranged so that the formed pipe enters the machine in a cold state and the subsequent welding is executed at a speed of about 1 foot per minute, although many such welding machines operate at considerably higher 116 AUTOGENOUS WELDING AND CUTTING speeds. Tubes for bicycle frames are rolled at a speed of 80 feet per minute and over, which is much higher than the working speed of the welding machines. The equipment of a tube mill as regards such machines must vary according to the nature of the work. Preheating. Pipe welding machines are now in use with fittings which permit the pipe material to be heated to a tem- perature of 800 C. to 1000 C. (1472 F. to 1832 F.) im- mediately before it comes under the welding flame. By such preheating, the working speed of the machine is much increased and in some cases FIG. 125. Pipe welding machine equipped with oil preheater. double the capacity has been secured when compared with the cold method. At present there are two different methods of heat- ing, one by means of an oil flame (Fig. 125) and the other by means of a coke fire (Fig. 126). In the machines using the coke fire, there has been considerable difficulty experienced, due to the ashes from the fire lodging between the edges of the pipe and dam- aging the weld. This can be eliminated by providing a closed oven for the fire with a collar in the centre through which the pipe can be led, so there will be no direct heating of the material from the flame. Devices for Preheating. A French engineer, in an endeavour to utilize the waste heat of the welding GAS AND WATER PIPE 117 flame, arranged a block of heavy copper immediately in front of the flame. This block was provided with a hole for the passage of the pipe and so placed that the excess portion of the flame heated the interior of the copper block and this heat was then transmitted to the approaching pipe. FIG. 126. Pipe welding machine equipped with coke preheater. Such a preheating device is practicable, but for satis- factory results it would be necessary to prevent the loss of heat by means of a jacket of non-conducting ma- terial on the exterior of the copper block. If the excess heat from the flame was insufficient, supplementary heat could be supplied by arranging a row of Bunsen burners underneath the copper block. In welding machines, the method employed for pre- heating, whether an oil, a gas or a coke fire, is dependent entirely upon the cost of the fuel, since either method is entirely satisfactory with proper care. Guiding Device. In the existing pipe welding ma- chines it is very important that a guiding device be fixed in the cleft of the pipe which is not yet welded, so that the place to be welded can be brought properly under the welding flame. 118 AUTOGENOUS WELDING AND CUTTING The welding flame in such machines also requires attention as it is necessary that an extraordinary con- stancy of pressure and uniformity in the mixture of the gases is secured. Care should be taken to obtain the maximum uniformity of pressure in the construction and operation of the acetylene apparatus adapted for this purpose. Reliability of Flame. An acetylene apparatus, which regulates the flow of gas under different pres- sures, or which might allow blockages in the outlet from the gasholder, is unsuitable for use in such welding. It is well known that any heating of the material in the tip of the welding torch when in use will cause a change in the mixing proportion of the acetylene and the oxygen. Cooling of Torch Tip. As a change of the welding flame, so caused, would materially damage the pipe manufactured, it is essen- tial that the temperature of the burner tip be kept at an even degree by means of a water cooling apparatus (Fig. 127). FIG. 127. Welding burner equipped The rollers of the pipe with water cooling device for pipe welding ma chine may also welding machine. be cooled advantageously by similar water circulation. Installation of Pipes by Welding. In addition to the benefits resulting from the application of autogenous welding in the manufacture of pipe, there is also much economy possible by the introduction of this method in the laying of such pipes. In the laying of pipe with screw couplings as was formerly the practice, the walls of the pipe are de- GAS AND WATER PIPE 119 creased by one half of their thickness through the cutting of threads for connections and consequently the resistance capacity is correspondingly decreased. The strength of the walls of the pipe must therefore be sufficient for the pressure as well as for tensile stress and the depth of cut of the thread would neces- sitate a superfluous thickness of material. By the methods formerly used in the manufacture of pipes a definite thickness of material had to be maintained throughout as the welding could not be satisfactorily accomplished with material of different thickness in the same section. Reduction of Material. If the use of screw pipe connections is abandoned and the welding of pipe ends is adopted, it is unnecessary to provide thicker pipe walls for such installations than those sufficient to meet the subsequent stresses. Autogenous welding offers great advantages, there- fore, in both the manufacture and installation of such pipe. It is very essential, however, that a plumber engaged in such work, be perfectly familiar with the autogenous welding methods, as the pipe ends and the joining of side branches must be effected upon the spot. In such installations the dripping away of the material, on the lower part of the pipe shell, must be avoided as the welding must necessarily be executed at the end of the pipe. Education of Welders. This requires the use of acetylene apparatus in which superheating of the gases, during the generating process, is excluded, and also requires great experience and practice on the part of the workmen. In the instruction workshop of the autogenous weld- ing of metals at the Royal Technical High School of 120 AUTOGENOUS WELDING AND CUTTING Cologne, which was installed by and is now under the direction of the author, the autogenous installation of tubes has been made a special subject of instruction, and it is to be hoped that other training colleges will follow this example. CHAPTER XV CONSTRUCTION OF PIPE-SHAPED APPARATUS THE employment of autogenous welding in the man- ufacture of pipes has developed an important branch of industry, in the construction of cooling apparatus, employing the system of heat exchange by means of counter currents. Cooling Apparatus. Such apparatus consists, usu- ally, of an undulating shaped pipe capable of conduct- ing either liquid or gas, around which a similar shaped pipe of larger diameter is concentrically placed. The ends of the outer pipe are closed upon and welded to the walls of the inner pipes (Fig. 128) . C o n n e c t i o n s are FlG> 128 _ Method of tack _ then made and the direction of ing sheet sections before the liquid or gas, in the one weldm g- pipe, is opposite to the direction of the second fluid in the other pipe. Ammonia Machines. Ammonia cooling machines, and similar apparatus for the exchange of heat, con- sist of a series of straight tubes arranged parallel and joined at alternate ends so as to provide a continuous flow, but with an alternating upward and downward movement. The straight parts of such tubes are en- cased in larger tubes, the ends of which are closed in a special forming machine previous to their application so as to fit the outer diameter of the inner tube to 121 122 AUTOGENOUS WELDING AND CUTTING which they are then welded. The larger tubes are then joined, by short pipe sections, alternately above and below, and in this manner a very efficient counter current heat exchange apparatus is produced (Fig. 129). FIG. 129. Counter-current cooling apparatus manufactured from sheet metal by autogenous welding. The industrial possibilities for the employment of autogenous welding in the manufacture and assembling of tubes for the conduct of water and gas are very great. Similarly, extensive use is also made in the manufacture of thin shelled tubes of rather small diameter for isolation pipes in electrical installations and such purposes. There is also a wide field in the manufacture of tubes for the construction of cycles, flying machines, motor cars, metal furniture and other purposes, with a thick- ness of material varying between .5 m/m and 1.5 m/m PIPE-SHAPED APPARATUS 123 (1/64 and 1/16 inches) and numerous large factories de- vote themselves entirely to this particular industry. Bicycle Tubing. Such tubes, smoothened out by a cold drawing process after having been completed, are variously employed for bicycle manufacture. In these tubes, the material is often required to stand very great strains in one direction and for this reason, tubes have been developed, for such service, which possess an oval cross section in place of a circular one. This is ac- complished by drawing the circular tube through an oval form whereby the required cross section is secured. In constructing tubes of this kind which are used in cycle manufacture, the strain upon the strength of the tube is usually placed in its lengthwise, rather than in its crosswise, axis. A certain firm, for a number of years, produced an oval tube that was particularly su- perior to its rivals owing to its greater firmness, and during this time, the manner by which this greater power of resistance was ob- tained remained a secret. It was only on the occasion of a lawsuit that the process, used by this firm, became common property of the engineering world at large. Oval Shaped Tubing. In these tubes, the forming of the oval shape, FlG 130 _ Ov al-shaped from the circular tube was arranged so that the welding seam did not lie in the main axis of the tube, as is otherwise common, but immediately at the side of the axis (Fig. 130). During the last few years, the construction of aerial craft has become one of great importance. For this bicycle tubing with welding seam outside the line of strain. 124 AUTOGENOUS WELDING AND CUTTING purpose, it is essential to employ a construction tube of as little weight, but as great a power of resistance, as possible. ' In order to render relatively light, and thin shelled tubes, sufficiently strong for the great strains, in the operation of aerial machines, the author, on the occa- sion of the International Exhibition of Airships at Frankfort on Main in 1909, proposed several such con- struction tubes, which have since been accepted by industrial concerns (Fig. 131-132). FIG. 131. Two-section FIG. 132. Three-section tubing for aerial ma- tubing for aerial ma- chines, chines. Aeroplane Frames. If, for example, two triangu- larly shaped tubes are placed against one another and the places where they touch are autogenously welded together, a tube is obtained of light weight and strong resistance. Many similar tubes can be made of the most various kinds, according to the purpose for which they are to be employed. In welding such tubes into parts of machines, it is important that a superheating of the material near the welding place should be avoided. Joining of Tubes. This is done by the welder playing the flame upon the union, in a position as horizontal as possible, and by eliminating, at the same PIPE-SHAPED APPARATUS 125 time, the conduct of heat from the welding place to the adjoining portions of the material. To effect the latter purpose, the tubes, for a short distance from the weld- ing seam, should be surrounded by substances which conduct heat readily, as for example copper, so that the heat is absorbed by these protecting substances and its injurious influence upon the adjoining material is avoided. Where it is of advantage, in regard to the strain which it is later called upon to resist, the part may be hardened, in the usual man- ner, after it has been autogenously welded. Miscellaneous Apparatus. In making saddle supports, or rims of bicycles, from the prepared tube, a wedge shaped portion is cut out so as to leave a part of the original tube material intact. The material is then beiit round and the touching edges are welded (Figs. 133- 134). In the construction of aerial ma- chines, much use is made of the autogenous welding, but for the want of space, it is impossible to go further into this most interest- ing matter, and those interested are referred to the respective special literature on this subject. A process analogous to the manu- facture of bicycles is the making of iron furniture, and products of the most various kinds, such as bedsteads, chairs, etc., which can be easily manufactured by means of autogenous welding. This is also true in the manufacture of motor cars. FIG. 133. Bi- cycle frame tubing cut and bent into position ready for welding. FIG. 134. Section of a bicycle frame auto- genously welded. 126 AUTOGENOUS WELDING AND CUTTING Tapered Tubing. In pipe manufacture, it is often necessary to construct a pipe of such shape that the ordinary pipe forming and pipe rolling machines are unsuited, particularly tapered pipes, and similar shapes, which are formed, by the inclined roller process, and welded. Another important application is where welded pipe is drawn smaller in diameter, at regular inter- vals, by a process of great importance, in the manu- facture of ship masts, flag poles, lamp posts, fishing rods, etc. Ship Masts. The extent to which such process can be utilized can be better appreciated when it is known that recently, a Westphalian factory success- fully undertook the manufacture of fishing rods, whereby a pipe of 25 m/m (1 inch) 'diameter was re- duced, at regular intervals, so that the smallest section had a diameter of only 5 m/m (-5- inch). Autogenous welding, capable of withstanding such severe stresses, must be entirely satisfactory. CHAPTER XVI WELDING OF COPPER COPPER is, next to iron, the most important of metals and owing to its dense structure, which permits it to be easily polished, together with greater ductility, it is extensively used for the most varied industrial purposes. It has a specific gravity of 8.8 and a melting point of 1084 C. (2084 F.), while the boiling point is 1500 C. (2730 F.). In a heated condition, copper easily combines with atmospheric oxygen, forming oxide of copper, which compound first exists only on the surface, but later on, becomes absorbed in the solid material. The normal color of copper is a light salmon red, but when oxidation occurs, the color changes to a dark copper and, near hard soldered places, one may observe the light salmon red fractures merging into the dark brick red fracture, if the material is broken across the joining seam. In such cases, the copper is said to be burned. Molten Properties. In a properly adjusted autog- enous welding flame, the acetylene receives only a sufficient quantity of oxygen to convert it into free oxide of carbon and free hydrogen. If, on the other hand, there is a surplus of oxygen, in the welding flame, complete combustion of the gases takes place, forming carbonic acid and water. When this occurs, part of the flame, which contains these products of combustion, has no reducing qualities and by superheating the simultane- 127 128 AUTOGENOUS WELDING AND CUTTING ously formed steam, free oxygen is liberated, which combines itself with the copper. Molten copper has a great capacity to absorb gas and particularly hydrogen, which gases are again eliminated, when the copper solidifies. They rise in bubbles to the surface and then burst, shedding delicate particles of copper around them. This phe- nomenon is familiar to copper founders. If the welding place of the copper cools and the solid- ifying of the surface takes place, before such small gas bubbles have been liberated from the molten mass, these bubbles form porous places in the copper material. Copper has great affinity for oxygen at temperatures considerably below the melting point, losing its physical qualities by combining with it, forming oxide of copper. This characteristic of copper renders it necessary to observe strict precaution, in the autogenous welding of this metal. Also, in hard soldering of copper, this phenomenon occurs and it is necessary to protect the molten metal and the adjoining parts against absorb- ing oxygen out of the atmosphere. This protection is effected by the application of a welding powder, or flux, which has a melting point immediately below, and a point of evaporation somewhat higher, than the melting point of the copper. Welding Powders. In such industry, it is usual to apply mixtures of borates and silicates, as welding powders, but it is advisable, in welding copper, to add a substance which has a great affinity for oxygen. Many welding powders have been introduced which contain a certain percentage of compounds of phos- phorus and compounds of borium. Phosphorus has the particular ability to reduce oxides of copper to metallic copper, while at the same time, the molten mass becomes as light a liquid as water. WELDING OF COPPER 129 In copper founding, ingredients of phosphorus are generally used in the melting, but a high phosphor per- centage makes the copper brittle. The quantity of phosphorus added to the copper must not, therefore, be much larger than is absorbed in the process of dis- oxidation of the metal, so that the phosphorus does not remain in the copper substance except in infinites- imal quantities, which are harmless. Aluminium, too, has valuable dis-oxidizing qualities, of which ample use is made in the manufacture of steel castings. In autogenous welding the phosphorus is usually rendered effective by the employment of copper filling bars, which have a small percentage of phosphorus, but not more than 0.05%. These filling bars usually contain other ingredients in small quanti- ties, such as aluminium, or borium, and their manu- facture requires great care. Small ingredients of aluminium make the homo- genous mixing of the molten mass very difficult, as this substance has only about one fourth of the gravity of copper and equal distribution, over the whole mass of the copper, is almost impossible. Operation of Welding Flame. In the autogenous welding of copper, it is important that the welding flame should be properly adjusted. Also, if the inner cone of the welding flame touches the molten mass of the copper, a burning of the copper occurs, as will also happen to the filling bars, if they are similarly exposed. To obtain a good welding of copper, it is necessary to melt down the joint by careful operation of the torch and to introduce new material, from a suitable filling bar of copper, so as to stir the molten mass. If the filling bar has a certain percentage of phos- phorus, the latter will form a compound of phosphoric acid with the oxides of copper, which are being dis- 130 AUTOGENOUS WELDING AND CUTTING oxidized. This acid will flow along the surface as a thin tough film, protecting the copper from the oxygen of the atmosphere and consequently superheating, or oxidizing, of the copper cannot take place. In this case, the phosphoric acid, which is formed, replaces the welding powder which would otherwise be required. In this manner, pure welding of copper may be obtained but it is advisable, and particularly so for the beginner, to employ a good welding flux in addition. This welding powder is sprinkled upon the surface of the copper after it has been heated and melts down into a film shaped coating. It is advisable to cover the mass of copper to be welded, on either side, with welding powder in this manner, for in copper one has to deal with a metal which has a melting point higher than the melting point of its oxides. This is also the case in alloys of copper. Avoiding Burning the Metal. The experienced work- man in autogenous welding or hard soldering is able to judge from the glow of the heated spot of the copper when the burning of the metal with the oxygen of the atmosphere can take place, as this state of heating is characterized by a dazzling white appearance. If it is possible to effect a union of the metal before this high temperature of the copper, or its alloys, is reached, that is, if a temperature is secured, which is immedi- ately below the melting point of the metal, all combus- tion of the metal can be surely avoided. There have been methods evolved, by numerous firms, for the welding of copper and of copper alloys, which are founded upon such process. The parts of the metal, which are to be joined together, should first be cleaned thoroughly, at the place of welding, and then be placed one upon the other and heated by WELDING OF COPPER 131 an autogenous welding flame to a temperature slightly below the melting point. A metallic anvil, or rail, which has been heated, should be used and, upon such support, the parts to be joined should be heated and worked, by small hammers, so that a kind of fire weld- ing is effected. Hammering Method. In the working of copper alloys, such as brass, bronze, or various compositions, this method, particularly, is much in use. For this purpose, small hammers with heads of an area of 8 m/m (5/16 inch) square are used with advantage. It is necessary that these hammers strike that part of the material only, which has been heated to a suit- able temperature, under the influence of the flame. Usually, the workman takes the welding torch in one hand, with the small hammer in the other, and effects a kind of puddling, as was mentioned above in the welding of mild steel. The employment of a welding powder is not required in this case but, if such is employed, it should be care- fully eliminated from the joint by hammering. In welding brass, or brass alloys, the parts to be united may also be washed with the usual soldering water but in this case, the surfaces to be joined must, pre- viously, be thoroughly cleansed. CHAPTER XVII WELDING OF ALUMINIUM THE most important matter to consider, in the autogenous welding of aluminium, is the great dif- ference between the melting points of the metal and of its oxide. Metallic aluminium melts at 650 C. (1200 F.) while the melting point of the oxide of aluminium is upwards of 3000 C. (5450 F.). Another important item is the great affinity of alu- minium for oxygen and, in the melting of the metal, it will be observed that, on the surface of the single small drops, a compound is formed with the atmospheric oxygen as a thin and tough film. Influence of Oxide. It is not possible to destroy this film of oxide by the application of external heat, although this heat has a considerably higher tempera- ture than the melting point of the oxide. In the molten metal, its melting heat remains latent and, notwithstanding the temperature of the flame, the film of oxide is cooled down to the melting tempera- ture of the aluminium metal from beneath. For this reason, it is absolutely necessary, in welding aluminium that the film of oxide be destroyed, which may be done either chemically or mechanically. In the autogenous welding process, the oxide film is de- stroyed and a pure metallic combination is effected; in which respect, it differs from the soldering method. It is one of the characteristics of the soldering method that a union is effected, although imperfect, without the 132 WELDING OF ALUMINIUM 133 destruction of the oxide, so that a film still exists be- tween the parts that have been united. Electrical Properties. This is of great practical importance, for aluminium has different electrical properties from those of its oxide. Therefore, in each combination of masses of aluminium, where the films of oxide intervene, galvanic chains must exist, which eventually lead to the destruction of the union. If acid is present, as, for example, sulphuric acid, which is found diluted in the atmosphere of industrial districts, any combination that has taken place can- not be satisfactory, if the film of oxide has not been destroyed. Mechanical Destruction of Oxide. The destruction of this film can be effected by mechanical means. In this case, the surfaces of two parts of metallic alumin- ium are put one upon the other after they have been cleaned of all foreign substance, as oil or grease. The surfaces are then heated with the welding flame to a temperature of about 400 C. (750 F.) and are then gently, but rapidly, hammered. In this manner, the intervening films of oxide are destroyed and the metal is welded together. This elimination of oxide can also be effected by means of rolling. This process, which is identical with the puddling previously mentioned, is employed on a great scale, for the most various purposes, in Germany, particularly in the manufacture of sheet aluminium vessels. Another mechanical method consists in the following process. The edges of the aluminium parts, to be united, are prepared and melted in the usual way, and the molten material is then stirred with the filling bar. In this manner, the films of oxide are destroyed and it is thereby possible to make the various parts 134 AUTOGENOUS WELDING AND CUTTING flow together into one mass, by means of the stirring, in a manner similar to the uniting of separated drops of mercury poured out on the hand. This method is impracticable, in the case of rather thin sheet metal, because the quantity of material is insufficient. Such method is also somewhat unreliable; as there is always the danger that a small detached film of the oxide is molten in, causing local partitions in the weld- ing seam. Chemical Destruction of Oxide. The most re- liable method for the proper uniting of parts of alumin- ium is the one wherein the oxides are destroyed by a suitable flux. The established practices of autogenous welding of aluminium are founded chiefly on the use of such fluxes. This flux or powder consists either of a mixture of alkali chlorides and compounds of fluor and kalium with chlorides of alkalies or the latter alone. The composition of such a poWder is the following: Kalium Chloride (KC1.) 45% Lithium Chloride (LiCl.) 15 % Natrium Chloride (NaCl.) 30% Kalium Fluoride (KF1.) 7% Double Sulphide of Sodium (NaHSO 4 ) 3 % Welding Powder. The melting points of the single constituents of such a mixture vary considerably from each other and, in some of them, the melting point is above that of the aluminium metal. This involves the danger that single parts of the mixture may not be melted during the operation and thus become fixed within the molten metal, in the form of black grains. This imperfection can be remedied by first pulver- izing the individual constituents of the flux and then proceeding with the mixing process in the required percentages. Such a powder is extraordinarily hygro- WELDING OF ALUMINIUM 135 scopic and absorbs the moistness, which is always present in the atmosphere, thus forming a pulpy mass. For this reason, such powder for welding aluminium must never be left standing open in the air but must be kept in closed bottles and, if possible, in such bottles as are fitted with ground glass stoppers. It is also advisable to thoroughly seal the bottle with a thin coating of wax. Patent Process. In Germany, M. U. Schoop has taken out two patents for a method of autogenous welding of aluminium. The principal patent protects a process for the welding of metal with the use of a flux consisting of a mixture of alkali chlorides. The additional patent covers the addition of compounds of fluor to such mixtures. These two patents are in possession of the A. G. fur Autogene Aluminium Schweissung, Zurich, Switzerland. This Company manufactures the flux in the form of a kind of paste, which is put upon the parts of the alu- minium which are to be united by means of a brush. The welding bar, which must consist of pure alumin- ium, is also plunged into this paste. It is of advantage, in the employment of dry powders, to heat the filling bar so that the welding powder will melt and flow upon the bar as a thin film, which heating can be advantageously done by the welding flame. In the welding operation, the bar must be kept in a ver- tical position, so as to allow the film of the flux to flow down the surface of the bar. Care must be taken that there is no unnecessary heat- ing of the powder by the welding flame, or touching of it by the inner cone of the flame, because some of the constituents of the mixture would be liable to evap- orate and the composition of the rest be unfavourably influenced. 136 AUTOGENOUS WELDING AND CUTTING Sheet Metal. In the welding of sheet metal, the filling bar should be carried in the direction of the welding, so the filling material can be virtually inserted in the trough. The autogenous welding of aluminium requires great skill and training but, properly handled, the aluminium which has been welded is nearly equal in strength to the original metal. CHAPTER XVIII NICKEL AND OTHER METALS NICKEL is extensively employed in industry both in the pure state and in alloys with other metals. On the whole, its properties are very similar to those of iron. It has a melting point of 1600 C. (2912 F.) and, in a molten state, has the property of absorbing large quantities of gases, particularly oxygen, which gases remain intact after the mass cools down, forming cavities. Another property of great importance, in the autog- enous welding of nickel, is its great affinity for sul- phur, with which it forms many compounds. It is frequently stated that nickel is incapable of being welded by an autogenous welding flame but this is incorrect, although such process involves considerable difficulties. Welding Temperature. Nickel, like iron and most other metals and alloys, is entirely weldable. That is, at a certain heat below the melting temperature it may be plastically kneaded by means of mechanical force. Further, by executing the union at a tempera- ture below the melting point, the injurious absorption of gases by the metal does not generally occur. During the autogenous welding of an alloy composed of nickel and iron, it often happens that the nickel separates from its alloying component and a fracture of the welding seam will reveal small globules of pure nickel. 137 138 AUTOGENOUS WELDING AND CUTTING Use of Heated Anvil. Due to its great capacity for conducting heat, all welding of nickel must be done with the parts resting upon an anvil, which has pre- viously been heated to a dark red. This anvil can be heated in a coal fire or by a gas flame. In welding two plates, in the manufacture or repair of nickel utensils, it is necessary that the faces of the two parts which are to be united, must be thoroughly cleaned. They are then placed upon each other, heated to a temperature just below the melting point, with the welding flame, and hammered together with small hammers. With proper care, the two parts can be thus welded to a homogenous body. Hammering Process. When two slightly heated nickel pieces are thus hammered together on a heated support or are pressed together by heated rolls, the direct welding which takes place effects a pure metallic combination which in no wise differs from the original metal in respect to structure or physical properties. As in the case of ordinary iron, the existence of po- rous places often causes much trouble in rolling mills and frequently rolled nickel plates contain porosities, which are not discovered until they are further machined. Formerly, these damaged pieces had to be cut out and as they then had only the value of scrap, extensive losses in labor costs were often occasioned. Repairing Nickel. In repairing such places by means of autogenous welding, the porous places are so worked with a drill as to clean the inner walls of all foreign matter. After sufficient heating of the piece in the vicinity of the place to be repaired, a pointed pure nickel wire is inserted in the opening and at the same time kept constantly heated with the welding flame. Such work, however, must be done with the plate resting on an anvil heated to a dark red, NICKEL AND OTHER METALS 139 In the manufacture of nickel tubes or similar ap- paratus, the same general principles must be employed and appropriate methods can be developed for the most varied kinds of work. Rules for Welding Nickel. It is necessary that the following rules be carefully observed : 1. The surfaces to be heated must be absolutely free from grease and oil and made mechanically clean by scraping or similar method. 2. The work must be done while the material rests on an iron support heated to from 700 C. to 800 C. (1300 to 1475 F.). 3. The hammering must be performed with long handled hammers of about 1 Ib. weight and only when the nickel plate has been brought to a bright white heat and the support is at a temperature between the figures just quoted. The successful welding of nickel is a development of great importance and the process will be widely applied in the future as soon as the art is more generally under- stood. Welding of Silver. Similar phenomena appear in the autogenous welding of silver as in the welding of nickel, and here also it is advisable to employ the hammering process which has repeatedly been men- tioned for the effective joining of the metal. Welding of Gold. Matters are, however, quite different in the autogenous welding of gold and ample use is made of this autogenous welding process in the goldsmith industry. In the working of gold the pure melting process is all that is necessary to be employed for the metal to join smoothly. Welding of Lead. The soldering of lead, which has been introduced into industry nearly 100 years ago, is, on the whole, nothing else than autogenous welding, 140 AUTOGENOUS WELDING AND CUTTING which soldering can also be executed to advantage with a welding flame. As the melting point of the lead is very low and its capacity for conducting heat is relatively small, the work with the oxy-acetylene flame, therefore, must be very quickly done. The welding of thin lead sheets especially, by the oxy-acetylene flame, requires extraordinary skill and practice, but with the proper handling of the burner such welding, as well as that of lead bodies, is eco- nomical and technically very advantageous. Welding Together of Different Metals. It is often required in industry to weld together things which consist of different metals as, for instance, iron and copper or alloys of copper. On the whole, the prin- ciples given on the subject of copper welding must be observed. The combustion of the copper must be avoided and as its capacity to conduct heat is much greater than that of iron, the iron part must be melted down first in such work and then the copper must be made to flow into the iron, employing a copper bar as filling material. CHAPTER XIX CONCLUSION IN the foregoing pages, the working of the most important metals and metal alloys has been discussed and an attentive autogenous welder will be able, from the text, to form for himself a clear idea in regard to such metals as have not been dealt with here, as to how he must act in each particular case, in operations of these kinds. The whole of the technique of autogenous welding is at the present time in a course of technical refine- ment. New working methods are constantly appearing and the field of application for the process is being rap- idly extended. In the most various industrial establishments defi- nite working methods have been formed but which are now treated as manufacturing secrets, and it is in the nature of technical development that such processes should gradually become the common property of all students of the art of welding. The process which is considered to be the most im- portant one and which apparently is destined to pro- duce a revolution in many industries, is the puddling process, which has been repeatedly mentioned in the foregoing pages. The physical characteristics of metals frequently alter very considerably when the metal is converted into a molten state, and it is apparent that where, by the melting of the metal, such alteration occurs, there are valuable technical advantages in 141 142 AUTOGENOUS WELDING AND CUTTING effecting a homogenous combination below the melting temperature, as can be secured by the puddling of the heated metal parts. This puddling process is the basis of the fire welding which has been in use from time immemorial and, with the introduction of aluminium, it returned for technical purposes in the Hearus process. With the constant increase in the number of metal alloys, which are becoming available for technical purposes, it will also play an important part in the autogenous welding of such alloys. In the opinion of the writer, the general introduction of the puddling process opens further industrial pros- pects, as, by this means, many metals and metal alloys can be satisfactorily combined, which were formerly considered as thoroughly incapable of being welded. This opinion was held because such metals, in their molten condition, have great capacity for absorbing the gases which are the products of combustion of an autogenous welding flame, which would render autog- enous welding seams porous and brittle. Therefore the attention of the students of autogenous metal- working is specially directed to this process and its future development is earnestly recommended to them. INDEX Absorption of gases by molten metal, 3, 4, *13, 14, 54, 127, 137. Acetylene, basis of manufacture of, 7. chemical properties of, 5. combination of oxygen and, 5. dissolved, 19. overheated, 11, 13, 14, 54. piping of, 31. polymeres of, 6, 11. purification of, 20, 21. welding pressure of, 31, 35. Acetylene dissous, bottles for, 19. burners for using, 19, 35. general properties of, 19. preparation of, 19. shipment of, 19. use of, 19, 20. Acetylene generators, automatic, 17. carbide to water, 9, 10, 20. charging and cleaning of, 10, 11, 13, 16, 17, 19. compressed carbide, 12. dipping, 17. dust carbide, 14. polymerisation in, 11, 13. portable, 8. size of carbide for, 8. stationary, 8, 12. temperature limits for, 10. water requirements of, 10, 20. water to carbide, 9, 16, 21. Acetylene purifiers, chemical, 20, 21. direction of gas flow in, 21. material for, 21, 22. mechanical, 21. Advantage of using welding burners larger than standard, 43. Aeronautical motors, manufacture of, 101. Alloys, welding, of copper, 131. of nickel, 137. separation of components of, 137. 144 INDEX Aluminium, autogenous welding of, 132. chemical properties of, 132. electrical properties of, 133. melting point of, 132. methods of destroying oxide of, 132. oxides of, 132. patented processes for welding, 135. physical properties of, 132. soldering of, 138.. strength of welds in, 133, 136. welding powders for, 134, 135. welding of sheet, 136. Annealing metals after welding, 74. Annular welding, 95. Autogenous cutting of metals, cost of, 47. gas consumption of, 48. industrial applications of, 47. speed of, 48, 49. theory of, 44. Autogenous welding, different processes of, 2, 3, 4, 5. future developments of, 141. gas consumption in, 42. general description of, 1, 2, 50. industrial applications of, 1, 2. machines, 115. of aluminium, 132. cast iron, 58, 63. cast steel, 59, 62. copper, 127. gold, 139. hard steel, 60. iron, 61. lead, 139. mild steel, 60, 62. nickel, 137. pieces of different thickness, 91. pipe, 112, 114. sheet iron, 68. silver, 139. two different metals, 140. wrought iron, 60. puddling process of, 76, 131, 138, 139. Automobile motor manufactured from sheet metal, 101. Back firing of welding burners, 31, 36, 39, 41. Beagid, 18. INDEX 145 Bending tests of autogenous welds, 59. Benzine, general properties of, 4, 5. Benzol vapors, general properties of, 4, 6. welding uses of, 5. Bevelling of metal before welding, 69, 90. Blaus gas, 4. Blowholes in metal after welding, 54, 128, 137. Boilers, steam, causes of failures in, 80. construction of, 81. effect of temperature variations in, 80. manufacture of, 81. repairs to sheets in, 83, 84. repairs to tubes in, 85. Boss welded on vessel for pipe connection, 103. Bottles, capacity of, 23. for dissolved acetylene, 19. hydrogen, 3. oxygen, 23. handling of, 19, 29. repairs to, 27, 28, 29. valves and fittings for, 27, 28. weight of, 26. Brass, composition of, 39. welding of, 131. Burners, adjustable, 36. back firing of, 31, 36, 39, 41. cleaning of, 41. construction of, 35, 39, 40, 44. cutting, 44. equal pressure, 35. flame adjustment of, 37, 38. gas consumption of, 42, 48. injector, 31, 36. operation of, 37, 38, 39, 42. selection of, 36. use of large, 43. welding, 35, 39. Burning of metal during welding, 3, 13, 54, 72, 127, 130, 137. Bunsen burners for preheating, 117. Calcium carbide, commercial sizes of, 7. compressed, 18. drums, 7, 8. dust, 14. general properties of, 7. heat generated by gasification of, 9. 146 INDEX Calcium carbide, quality of, 20. storage of, 8. Carbide to water generators, 9, 10, 20. Capacity of oxygen bottles, 23. Carbon in molten iron, 13, 50, 54, 62. Carbonising flame, 38. Carbonization of metals, 38, 54. Care of burners, 41. Cast iron, expansion of, 64, 65. filling material for welds in, 58. general properties of, 50, 57, 58, 64. melting point of, 64. repairs of, 63, 65, 66. structure of, 50, 57, 58. welding of, 58, 59, 63. Cast steel, filling material for welds in, 59, 60. welding of, 59, 62. Causes of burning in the welding seam, 54. Charging acetylene generators, 10, 11, 13, 16, 17, 19 Chemical process for producing oxygen, 26. Chemical properties of acetylene, 5. aluminium, 132. copper, 127. hydrogen, 2, 3. iron, 50. oxygen, 3, 5. nickel, 137. Chemical purifiers, design of, 20. materials used in, 21. Circumferential seams, welding of, 88. Cleaning dust filters, 22. generators, 10, 11, 13, 16, 17, 19. tips of burners, 41. Co-efficient of tension in cast iron, 64. Combustible gases, 2. Complex castings, repairs to, 66. Composition of welding fluxes, 58, 128, 134. Compressed carbide generators, 18. Conduits, large, compensation couplings for, 110. corrugated sections for, 111. elbows for, 108. flanged connections applied to, 109. installation by welding, 110. manufacture of, 107. strength of welded, 109. tee connections welded on, 107. INDEX 147 Cooking utensils, manufacture of, 105. Cooling of heated welding burners, 37, 40. Copper, alloys of, 131. autogenous welding of, 127. filling material for welding of, 129. hammering method in welding of, 131. influence of phosphorus in, 129. melting point of, 127. oxides of, 128. position of burner in welding, 129. properties of, 127. soldering of, 128. welding powders for, 128. Critical temperature of air, 24. oxygen, 25. nitrogen, 25. Cutting burners, construction of, 45. designs of, 44. gas consumption of, 48. guiding devices for, 46. industrial uses of, 47. motor driven, 46. operation of, 45. Cylindrical vessels, circumferential seams welded in, 88. closed, 93. construction of, 86. corrosion in, 96. heads of, 94. horizontal seams welded in, 27. intermediate heads applied in, 98. internal strains in, 93. joint rings for, 92. large, 90. open, 91. supports for, 97. Defective welds, 54, 63, 71, 72, 128, 132, 137. Demonstrating expansion of sheets under influence of welding flame, 87. Devices for use in autogenous cutting, 46, 47. welding, 86, 88, 89, 90, 96, 100, 131, 139. Diameter of hose for gas welding, 31. Dipping acetylene generators, 17. Dissolved acetylene, bottles for, 19. general properties of, 19. 148 INDEX Dissolved acetylene, preparation of, 19. use of, 19, 20. welding and cutting burners for, 19, 35. Distinction between superheating and combustion of iron in welding, 54. Double shell vessels, manufacture of, 103. Dust carbide generators, 14. Dust filter for acetylene, 22. Education of welders, 119. Effect of excess carbon in molten iron, 54. Effect of temperature variations on boiler sheets, 81. Elbows manufactured from sheet segments, 108. by unequal heating of the sheets, 109. Electrolytic process for producing oxygen, 25. general description of, 25. power requirements for, 26. Expansion of cast iron during welding, 64, 65. Expansion of sheets during welding, 87. Experiments in autogenous cutting at Birmingham, England, 49. Explosions in acetylene generators, causes of, 11. Failures of welds in aluminium, 132. cast iron, 63. copper, 128. iron and steel, 54, 72. Filling material for welds in aluminium, 135. cast iron, 58. cast steel, 59. copper, 129. hard steel, 60. mild steel, 60. nickel, 138. wrought iron, 60, 70. Filter for acetylene, 22. Fittings for oxygen bottles, 26, 27. Flame, adjustment of burner, 37. carbonizing, 38. neutral or correct, 37. oxidizing, 37. Flanging of sheets for welding, 68, 69. Flexible metal hose for burners, 34. Fluid for testing the purity of oxygen, 24. Flux for welding aluminium, 134, 135. cast iron, 58. copper, 128. INDEX 149 Flux for welding steel, 61. wrought iron, 61. Foaming of the welding seam, 13. Frames, window, made by welding, 106. Future developments in autogenous welding, 141, 142. Gases, absorption of, by molten metals, 3, 4, 13, 14, 54, 127, 137. Gases, combustible, acetylene, 5. benzol, 4. blau, 4. hydrogen, 2. illuminating, 4. liquid, 4. Gas consumption of burners, 42, 48. Gasifying dust carbide, 14. Gas mains in welding shop, 31. Generators, acetylene, automatic, 17. carbide to water, 9, 10, 20. charging and cleaning, 10, 11, 13, 16, 17, 19. compressed carbide, 18. dipping, 17. dust carbide, 14. polymerisation in, 11, 13. portable, 8. size of carbide for, 8. stationary, 8, 12. temperature limits for, 10: water requirements of, 10, 20. water to carbide, 9, 16, 21. Gold, autogenous welding of, 139. Granulated carbide, 7. Hammering method in welding of aluminium, 133. copper, 131. nickel, 138. silver, 139. wrought iron, 76, 84. Hard steel, filling material for welds in, 60. welding of, 60. Heads welded in cylindrical vessels, 93, 94, 98. Heat absorbing plates, 70, 96, 100. Heat generated by gasification of carbide, 9. Hole welding, 98. Horse power required for producing oxygen with electrolytic process, 26. Horse power required for producing oxygen with liquid air process, 25. 150 INDEX Hose, diameter of, 31. fittings, 33. metal, 34. repairs, 34. rubber, 33. Hydrogen, basis of manufacture, 2. bottles for, 3. chemical properties of, 2, 3. commercial uses of, 3. difficulties in welding with, 3, 52. shipment of, 3. Hygroscopic purifying material, 21. Illuminating gas, difficulties in welding with, 4. Impurities in acetylene, 20, 21. carbide, 20. iron, 52. oxygen, 23. Influence of phosphorus in copper, 128. Injector burners, 31, 36. Installation of pipes by welding, advantages of, 118. in ships, 110. methods of, 109, 119. Instruction schools for welders, 1 19. Intermediate heads applied to cylindrical vessels, 98. Iron, absorption of oxygen by, 54. autogenous welding of, 52. carbon percentages in, 50. cast, 50, 57, 58, 63, 64. chemical properties of, 50. decarbonization of, 52. impurities in, 52. magnetic properties of, 74. malleable, 50. physical properties of, 52. Swedish, 59. white, 50, 52, 57, 63. wrought, 56, 60. Iron oxide, influence of, on welds, 61. melting point of, 60. methods for destroying, 61. Joining of pieces of different thickness, 91. Joint rings, application of, 91. expansion during welding, 92. position of burner during welding, 92. INDEX 151 Lead, autogenous welding of, 139. soldering of, 139. welding of thin sheets of, 140. Leaking valves on oxygen bottles, 27. Linen cloth for dust filter, 22. Liquid air process for producing oxygen, general description of, 24. power requirements for, 25. Low pressure acetylene, 35. Machines for cutting, 46. welding, 115. repaired by welding, 66. Magnetic properties of iron, 74. Manufacture of acetylene, 7. automobile motors, 101. bicycle tubing, 123. boilers, 81. cookjng utensils, 105. cooling apparatus, 121. conduits, 107. cylindrical vessels, 86. double shell vessels, 103. elbows from sheet segments, 108. by unequal heating of sheets, 109. fishing rods, 125. hydrogen, 2. liquid gas, 4. metal furniture, 125. open sheet metal vessels, 104. ornamental articles, 105. oxygen, 24, 25. pipe, 112. radiators, 101. rectangular vessels, 99. safes, 100. ship masts, 126. stamped sheet metal articles, 101. superheaters, 100. window frames, 106. Martinsite, characteristics of, 62. conditions producing, 62. influence on the welding seam, 62. Mechanical purifiers for acetylene, 21. Melting point of aluminium, 132. aluminium oxide, 132. copper, 127. 152 INDEX Melting point of iron, 60. iron oxide, 60. nickel, 137. steel, 60. Method of developing a corner in the manufacture of open sheet metal vessels, 104. Mild steel, autogenous welding of, 60. Miscellaneous articles manufactured by autogenous welding, 105. Mixture of gases in burners, 40. Naphthaline, 6. Nickel, autogenous welding of, 137. chemical properties of, 137. hammering process in welding, 138. melting point of, 137. physical properties of, 137. repairing of, 138. rules for welding of, 139. use of heated anvil in welding of, 138. welding alloys of, 137. welding temperature of, 137. Non-hygroscopic purifying material, 21. Nozzles of cutting burners, 44. welding burners, 37. Open sheet metal vessels, manufacture of, 104. Ornamental articles, manufacture of, 105. Overhead welding, 78. + Overheated acetylene, effects of using, 14, 54. evidence of generation, 11. Overlapping of sheets during welding, 87. Oxides of aluminium, chemical destruction of, 134. general properties of, 132. mechanical destruction of, 133. melting point of, 132. of copper, general properties of, 127. methods of destroying, 128. iron: general properties of, 61. melting point of, 60. Oxidizing flame, 37. Oxygen, bottles, for shipment, 26. handling of, 29. impurities in, 23. measuring consumption of, 23. methods of production, 24, 25, 26. pressure for welding, 27. testing, 24. INDEX 153 Oxy-acetylene cutting, data on, 48. speed of, 48. Oxy-acetylene flame, chemical properties of, 5. Oxy-benzol flame, practical uses of, 4. temperature of, 4. Oxy-blau gas flame, difficulties in welding with, 4. practical uses of, 4. Oxy graph, 46. Oxy-hydrogen cutting, data on, 48. speed of, 48. Oxy-hydrogen flame, chemical properties of, 2. difficulties with in welding with, 3. influence of excess of oxygen in, 3. practical uses of, 3. temperature of, 3. Oxy-hydrogen welding outfit, 3. Pantograph, 46. Pearlite, characteristics of, 56. method of determining percentage of, 56. Phosphorus in acetylene, 20. copper, 128. Phosphuretted hydrogen, 20. Pipe flanges, methods of welding, 109. preparation for welding, 109. strength of welded, 109. Pipe installation by autogenous welding, 118, 119. Pipe manufacture, autogenous, 112, 114. defects to be avoided in, 114. earlier methods of, 112. materials used in, 112. welding machines for, 115. Pipe-shaped apparatus, ammonia machines, 121. fishing rods, 126. heat exchange, 121. metal furniture, 125. ship masts, 126. tubing for bicycles, etc., 123. Pipe welding machines, burners for, 118. designs of, 115. flame adjustment for, 118. guiding devices for, 117. preheating apparatus for, 116. speed of, 115. Piping in the welding shop, 31. Pit equipped for welding large cylindrical vessels, 90. 154 INDEX Polymerisation, phenomenon of, 5, 11, 54. products of, 6, 11. Portable generators, 8, 16. Position of burner during welding, 70, 92. Powders, welding, for aluminium, 134, 135. cast iron, 64. copper, 128. iron and steel, 61. Preheating of boiler sheets, 83. cast iron, 64. methods of, 64. of pipe, 116. value of, 64. Preparation of metal for welding, 59, 70. Pressure reducing valves, 26. Prevention of cracks in welding of cast iron, 65. Puddling process, advantages of, 77. for aluminium, 133. boiler repairs. 84. copper, 131. iron, 76. nickel, 138. silver, 139. future of, 141. operation of, 76. tools for, 77, 139. Purification of acetylene, 20, 21. Purifiers for acetylene, chemical, 20. materials for, 21, 22. mechanical, 21, 22. Purifying material, hygroscopic, 21. non-hygroscopic, 21. Purity of oxygen, 23. Radiators, manufacture of, 101. Rail, welding, use of, 86. Rectangular vessels, construction of, 99. expansion during welding, 99. location of seams, 99. position of burner for welding, 99, 100. use of heat absorbing plates, 100. welding cover on, 100. Reducing valves, cleaning of, 29. construction of, 28. operation of, 29. repairing of, 30. INDEX 155 Regulation of burners, 39. flame, 37. Reheating of metal after welding, 74. Repairs by autogenous welding, 63, 138. Safes, manufacture of, 100. Schoop process of welding aluminium, 135. Sheet iron, autogenous welding of, 68. Silicon in cast iron, 52, 58. Silver, autogenous welding of, 139. hammering process in welding of, 139. Stampings of sheet metal, 69, 101. Stationary acetylene generators, 8, 12. Steel, cutting with autogenous flame, 44. general properties of, 50, 60. percentage of carbon in, 50. cast, composition of, 59. filling material for, 59. welding of, 60. hard, filling material for, 60. welding of, 60. mild, composition of, 50. filling material for, 60. melting point of, 60. welding of, 60. Strength of welds in aluminium, 136. cast iron, 59. pipe, 109. Styrolin, 6. Sulphuretted hydrogen, 20. Sulphur in acetylene, %). Superheaters, manufacture of, 100. Tacking of pieces before welding, 69, 121. Technique of autogenous welding, 1, 141. Tee connections welded on large conduits, 107. Temperature limits for acetylene generators, 10. Temperature of oxy-acetylene flame, 4. benzol flame, 4. hydrogen flame, 3. required for welding pipe, 116. Tensions in grey iron castings and their influence on welding opera- tions, 63. Testing magnetism during welding, 76. oxygen, apparatus for, 24. Thick sheets, bevelling of, 69. 156 INDEX Thick sheets, failures of welds in, 71. filling material for, 70. influence of oxides in welding of, 72. position of the burner in welding, 71. preheating of, 73. preparation for welds in, 71, 73. reheating of, 74. Thin sheets, filling material for welds in, 71. flanging for welds in, 68. position of the burner in welding, 71. preparation for welds in, 69. Tools for puddling process, 77. Tubing, welded, for aeroplanes, 124. automobiles, 122. bicycles, 123. furniture, 125. various designs of, 124. Union by welding of cast and wrought iron, 62. iron and copper, 140. Use of two welding burners simultaneously, 77. Value of re-heating of thick sheets, 75. Valves for oxygen bottles, 26. Vertical welding, 78. Water displacement generators, 17. Water requirements of acetylene generators, 10, 20. Water seal, Fouche", 32. Herzfeld, 33. inspection of, 33. with pressure chambers, 34. with signal whistle, 32. Water superheated to high temperature, 2. Water to carbide generators, 9, 16, 21. Welding, autogenous, 1. burners, 35. industrial applications of, 1, 2. machines, 115. of aluminium, 132. cast iron, 58, 63. cast steel, 59. copper, 127. gold, 139. hard steel, 60. iron, 61. INDEX 157 Welding, of lead, 139. mild steel, 60, 62. nickel, 137. pipe, 112, 114. sheet iron, 68. silver, 139. wrought iron, 60. pressure of acetylene, 31. oxygen, 27. puddling process of, 76, 84, 131, 138, 139. together cast steel and wrought iron, 62. cast iron and copper, 140. Welding burners, adjustable, 36. back firing of, 41. cleaning of, 41. construction of, 39. equal pressure, 35. flame adjustment of, 37. gas consumption of, 42. injector, 36. operation of, 71. selection of, 43. use of large, 43. Welding flame, adjustment of, 37. carbonizing, 38. chemical properties of, 5, 39. neutral, 37. oxidizing, 37. Welding powder for aluminium, 134, 135. cast iron, 58. copper, 128. iron and steel, 61. White iron, characteristics of, 50. formation of, 50, 63. Window frames, manufacture of, 106. Working pressure of acetylene, 31, 35. oxygen, 27. Wrought iron, autogenous welding of, 60. influence of oxides in welding, 61. melting point of, 60. use of flux in welding of, 61. THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO 5O CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. MAR IS W OflT :I3 1938 T 14 193o -IT 17 1941 M NOV 4 1938 MAY 12 1941 M MAR IT 1939 *&<- LD 21-95w-7,'37 YB I I 165 UNIVERSITY OF CALIFORNIA LIBRARY