કાગ 國 渴 simultaneously by the controlling lever. For forging small articles such as bolts, screws, etc., special machines are in use, striking a large number of blows per minute, the hammer heads and anvil blocks being moulded or enrved into the appropriate forms so as virtually to form dies; the blows are usually struck by means of cams lifting the hammers and bending strong springs which force the hammer back when the cams release them. See also HAMMER, vol. xi. p. 379-381. For bending into shape large masses of metal such as thick armor plates that have to be curved to the ship's side, powerful hydraulic presses are employed; by means of the same appliances large weldings of metal that cannot readily be hammered on account of the shape can be readily made; thus, for welding the spokes and tires of iron and steel wheels and the like operations, hydraulic forging, squeezing, welding, and bending machines are found to be eminently satisfactory. Crank axles thus bent are said to be stronger than ordinary forged ones. Rolling Mills.-After the bloom has been forged more or less into shape by the steam hammers, it is passed between a pair of stout cast iron rollers, usually with roughened surfaces, which are made to revolve synchronously but in opposite directions by suitable gearing; the opposed faces of the rolls which meet the FIG. 44.-Cave's modification of Nasmyth's Hammer. VOL. XIII.-595 bloom between them are consequently moving in the same direction; by these "roughing rolls" the bloom is squeezed out into a rough irregular long plate or slab, much as a lump of dough is by a cook's rolling pin; this is passed through another pair of rolls with smoother surfaces, which draw the mass out into a thinner bar or slab. Instead of having the two sets of rolls arranged one in front of the other, they are often placed one above the other; the bar after passing in one direction between one pair is returned again through the other pair. Instead of four rollers, only three are generally used (forming a "three-high train"), the bar passing above the middle one whilst travelling in one direction and below it when passing the reverse way. The "puddle bar" or "muck bar" thus obtained in the form of elongated slabs of from 4 to 18 inches wide, and half an inch to 2 inches thick, according to the size to which it has been reduced, is then cut up into lengths of some few feet, several of which are piled one on the other, reheated, and rolled down again into another bar or slab of superior quality (No. 2). For thick plates the pile is made much heavier than for thinner bars; two puddle bar wide slabs are used for the top and bottom of the pile, between which are arranged thinner bars, either of puddle bar or No. 2; the pile being heated to a welding heat, is first passed between roughed rolls to consolidate it, then through other pairs of smooth rolls in succession, the space between each pair being suc cessively less and less so as to elongate the bar and dimin ish its section at each passage, much as wire is in wire drawing; this is usually effected by grooving the rollers used for the last few rolling stages so that the rolls are almost in contact with one another saving where grooved Fig. 46 illustrates two kinds of successions of grooves used for rectangular bars in a "two-high" train, and fig. 47 those for rails in a "three-high" train on A. Thomas's system. The bars are turned one quarter round at each passage, so that the pressure may be exerted alternately compressing and extending each component layer of bars in the pile and thus developing a more uniform texture. | rolls is regulated, and consequently the thickness of the Sometimes, in reducing the pile to the larger-sized bar which is ultimately sent through the "finishing train" of grooved rolls, a combination set of rolls is employed, consisting of one horizontal pair of rolls and one vertical pair FIG. 46.-Two-high Trains. just behind it, so that the mass is compressed both laterally and vertically simultaneously (fig. 48). The "housings," or stout cast-iron supports for the rollers, are arranged with a slot so that the gun-metal bearings for the axles of the rollers can be raised or lowered by means of a powerful adjusting screw, and in this way the distance between the bar rolled out. In order to facilitate this adjustment the bearings of the upper roller are sometimes attached to a frame with a counterpoise, and connected with a hydraulic ram so as at will to bring the movable roll nearer to or further from the other; in this way one pair of rollers can be made to do the work of several rectangular grooves. Sometimes two pairs of horizontal rolls are arranged one just in front of the other, so that the size of the bar passing from the hinder pair is still further reduced by passing through the front pair, which are a little closer together and revolve more rapidly. When very thick plates are rolled, the direction of rotation of the rolls is reversed instead of returning the plate back again, special "reversing engines" being used for the purpose. For special kinds of work, such as rolling taper iron (e.g., the movable tongues of railway "points"), a peculiar lifting arrangement is applied to the upper roll, so that as the metal passes between the distance apart is varied. When an hydraulic ram is employed to vary the distance apart of the rollers, this is simply effected by adjusting the ram so that the distance apart of the rolls is the minimum requisite, and opening a small discharge valve for the water when the bar is introduced; as the bar passes through, the water is ejected in a regular stream through the discharge valve, the rate being so adjusted that as the bar travels through the distance apart of the rolls gradually increases: by closing the valve the distance apart remains constant, so that after rolling a taper end the rest of the bar can be rolled of uniform section. With a "two-high" train not reversed at each successive passage, the bar is lifted by hand or otherwise to the top of the top roller, which then guides it back to the side from which it started, after which it is put through the next groove, and so on; this causes loss of time, and prevents the bar being rolled so many times before it cools; accordingly for thin plates or rods of small section the three-high train is always used (or some more complex analogous combination of rollers). As a rule the speed of rotation of the rolls is less the heavier the plate, etc., rolled; for very thick armor plates (of which sizes up to 20 and 30 tons are sometimes rolled) a comparatively small number of revolutions per minute suffices; for thin rod a much larger number up to several hundreds; from 80 to 100 revolutions is about the usual speed for rolling rails and similar heavy bars, 50 or 60 being employed for very thick ones, 120 to 150 for lighter bars, and considerably more rapid speeds for very thin bars, rods, and wire. Space will not permit of descriptions of the details of various kinds of rolling-mill plant, etc., introduced in different works, and more especially of numerous American improvements in this direction, particularly those of Messrs. Fritz; for descriptions of these, the technological journals, etc., of the last few years must be consulted. For rolling tires a peculiar arrangement of comparatively small rolls is employed; the ingot after having a hole punched through it (or cast in a thick ring if of molten "ingot metal") is subjected to a kind of rolling action between two surfaces, one inside the ring and the other outside, so that the circumference of the ring is gradually extended and its thickness diminished, whilst the flange is simultaneously formed. When thin rods of rectangular section are required (e.g., nail rod), they are often made by rolling out a bar into a long wide thin plate, which is then passed through a "slitting mill" consisting of a pair of steel rollers with d'eep grooves, the projecting portions of the one fitting into the grooves of the other, but not reaching to the bottom of the grooves. These projecting portions act as revolving shears, so that the plate is "slit" as it passes into thin rods, the width of which is regulated by the width of the grooves; after passing through the machine these are straightened by hand. In order to cut puddle bars into lengths for piling, powerful shears are employed. Fig. 49 represents one form of double shears worked by a reciprocating lever actuated by an eccentric; fig. 50 represents a much more powerful form of guillotine shears. A massive plate B with a terminal shearing edge A A works slowly up and down in guides by means of eccentrics C, C, C on the shaft D; this cutting edge passes just in front of a similar one permanently fixed to the guide posts. The plate to be sheared is supported on a table a a in front of the shears, running backward and forward upon a little railway; whilst the upper cutting edge is elevated, the plate is quickly run into position, and as the cutting edge descends is sheared across, the cut-off por FIG. 48.-Universal Rolls. tion dropping down; as the cutter ascends again the plate is turned round or pushed forward, so as to bring under the cutter the portion to be sheared at the next down stroke. is raised. A powerful fly-wheel is requisite whenever the plate to be sheared or punched is massive. For cutting "crop ends" off hot or cold railway bars after rolling so as to reduce them to a uniform length, an arrangement analogous to a travelling table is used, urged forward by an eccentric, a toothed wheel and screw, or a chain and axle, etc., fig. 51; on this the bar FF is placed against stops B, B, and the table then moved forward (as represented in the figure by means of the handle G actuating an eccentric on the axis AA) so as to bring the bar gradually against the pair of rapidly revolving circular (usually toothless) saws C, C worked by a band and pulley E, and thrown out of gear by shifting the band to the "idle pulley" D when required; to prevent the saws from becoming overheated, the lower portions dip into water troughs as they revolve. A single circular saw revolving 5000 times a minute (with a circumferential velocity of about 300 miles per hour) has been used for this purpose. For obliterating file marks, reducing to roughly plane surfaces, cutting slots, smoothing, and many other purposes for which grindstones, etc., were formerly employed, emery wheels made of pulverized emery cemented together with calcium silicate are often used with great advantage. Cold Rolling.-In the ordinary processes of rolling iron plates and rods, etc., the metal is at a high temperature so as to be softened by the heat; when cold iron is similarly rolled the compression thereby produced gives a much greater stiffness and elasticity; thus Fairbairn found that an increase in strength in bars from 60,746 b per square inch before rolling to 88,230 after was thus effected. Whipple (of the U. S. navy) finds that in sheet iron the tenacity is thus increased by 60 and even 100 per cent. of the original value, and Thurston has recently found analogous results both as to increase in tenacity and power to resist strains and in the The same kind of machine serves for cutting boiler plate to any required dimensions, and for shearing purposes generally. Substituting a solid steel plunger for the cut Fig. 50. ting edge, the machine becomes a punching machine, the plate to be punched being supported on a travelling table, and the spot where the rivet-hole, etc., are to be pierced being brought under the end of the punch whilst the latter Fig. 51. modulus of elasticity. The process is largely in use in America, being carried out by rolling the bars, etc., out to a little larger dimensions than the finished metal is intended to have; they are then "pickled" in dilute hydro chloric acid to dissolve off the film of oxide from the surface, passed through limewater to neutralize the adherent acid, and finally rolled many times in succession between grooves of great smoothness, so cut as only to compress portions and not the whole of the circumference at each passage through the rolls. For a description of the appliances used in cold rolling as carried out at the works of Jones & Laughlin, U. S., who make a specialty of this business, see Engineering, vol. xxvi. p. 347 (1878). For straightening and planishing circular steel bars such as shafting rods, etc., a peculiar machine is sometimes used, consisting of a pair of revolving disks with bevelled faces, which compress the rod slightly between them, at the same time rotating it and transversing it forwards (and, by reversal, backwards) by one continuous movement, so that all parts of the surface are equally operated on, and the bar leaves the machine circular, straight, and bright-surfaced. Numerous other machines are in use for various special purposes, such as wire-drawing, drilling, 1 During several years past a series of papers on "American Iron and Steel Works," by A. L. Holley and Lenox Smith, have may be gained as to modern American improvements in variappeared in Engineering, from which much detailed information ous directions. screw-tapping, etc.; the description of these would take up more space than can be given here. his eyes to the fact that it is possible for other nations, though less naturally favored as to ores and fuel, to compete successfully with him, and undersell him, not only as to foreign trade, but even in the case of English contracts for iron work for home use. A marked feature in most American iron-works is the general handy, compact, and efficient nature of the machinery of all kinds, and the use of various physicalexertion-saving contrivances and arrangements for venti- The reheating furnaces employed to heat up to a lation and cooling of workshops, etc., many of which welding temperature the piles intended to be rolled are appliances are not so frequently to be met with on the essentially low reverberatories, much resembling pudeastern side of the Atlantic, more especially in England. The general arrangement and planning out of works, dling furnaces, in which the atmosphere is kept as little moreover, is usually far superior to that of the older oxidizing as possible; notwithstanding, a certain amount British works, which have gradually grown to their pres- of slag is formed from the fusion of the oxide of iron ent dimensions, and consequently have not been systemat- coating the bars and its union with silica from the furically laid out as a whole. In consequence of attention to nace bed when of sand, as is often the case; ferric such details as these, the output of finished material from oxide ores ("dry bottoms") are preferable, yielding a given amount of plant is frequently considerably greater in America than would be attained in other countries, whilst less cinder and causing less waste in consequence, the labor required is not proportionately increased; thus whence the name. To avoid introduction of air, the the largest makes of Bessemer metal from a given converter doors for introducing and withdrawing the piles are ever registered have been attained in American works; and banked up with small coal, etc. Gas forms a most so in other instances. To a considerable extent the same suitable fuel, and various forms of gas-fired reheating remarks apply to Continental establishments, at any rate furnaces have been introduced: thus in Sweden Eckto many of those of more modern arrangement; of late years, however, the spirit of competition and other influ- man's gas reheating furnace has been in use many ences have rendered it imperative upon the British iron-years, consisting of a chamber in which charcoal is master to pay more regard to such matters than was for- partially burnt by an air blast so as to form impure merly the case, and to adopt many American and Conti- carbon oxide, which passes by a tube into the renental improvements in details, experience having opened heating furnace and is there burnt. Siemens regener ators applied to reheating furnaces have also been frequently employed, and with good results, either with his gas producers or with other forms of gas generator; at Munkfors the Lundin gas producer (using damp sawdust, 10) is employed. Another form of reheating gas furnace is the Ponsard furnace (see ? 40). The chief advantage of gaseous fuel for reheating furnaces is that the atmosphere can be much more exactly regulated so as to be non-oxidizing, thus avoiding waste by "cutting (ie., oxidizing) the piles; independently of which, moreover, a saving in cost of fuel consumed is effected; thus Holley states that, in reheating Bessemer ingots or ordinary blooms in Siemens furnaces, 350 to 400 lb of coal are used to the ton, whilst the ordinary fires would consume 800 to 1000 lb. On the other hand, if the waste heat from the reheating furnace is used to generate steam, the saving in fuel that would otherwise have to be burnt for the purpose just about equals the difference in fuel consumption between the Siemens and the ordinary reheating furnaces. Price's retort reheating and puddling furnace (fig. 52) is a sort of combination of a gas producer and an ordinary puddling furnace; the firegrate is supplied with fuel which has been heated in a low tower surmounting the grate by the waste gases circulating in a flue round the tower; in this way the coal is coked, the gases passing to the fireplace; a blast is introduced under the fire bars so as to burn the coke and produce a large body of flame of reducing character owing to the admixture of hydrocarbons from the coking process in the tower; the blast is heated by passing through a chamber surrounded by the waste-gas flue; by regulating it the atmosphere can be made more or less reducing at pleasure. The saving of fuel effected is said to amount to about one-third of that which would be required in an ordinary puddling furnace, whilst when arranged as a reheating furnace a still greater saving is pro duced. Utilization of Waste Heat.-In all iron-works the amount of heat escaping from the puddling and reheating furnaces (except when regenerative) is enormously in access of the amount actually utilized; to economize this waste heat to some extent, it is usual to A ver- At 47 sition of Pig Charge Iron used. 66 mins. mence- Boil. 80 mins. 111 mins. 120 mins. Final Steel. allowance being made for its different calorific power. are more extensively employed. Schilling has examined the For reheating furnaces in which coal is burnt, the con- relative rates at which carbon, silicon, phosphorus, and sulsumption of fuel is usually in excess of 50 per cent. phur are eliminated from the pig irons of Gittelde and Zorge of the metal ultimately rolled for each time it is re-taining the results given in the following table: in a charcoal steel-puddling forge at Zorge (Hanover), obheated. The yield of puddle bars from a given quantity of pig varies somewhat with the quality in spite of some of the iron oxide of the fettling being reduced, the weight of malleable iron (cinder being deducted) finally obtained in hand furnaces is always somewhat less than that contained in the pig iron used; the latter averaging say 94 or 95 per cent. of iron, the yield of puddle bar may be said to run from 88 to 92, averaging about 90 per cent. Before an ordinary class of iron ore is converted into good bar iron there is in practice requisite a consumption of coal (or of its equivalent in coke, taking say three parts of coke to represent 5 of coal) to about the following extent per 100 parts of malleable iron finally obtained, that is, when each operation is conducted about as economically as is practicable on the large scale:Smelting to pig iron (140 parts of pig)... 250 Puddling to puddle bar (140 pig becoming 125 puddle In reference to this last item the consumption of puddle bar varies much with circumstances; a considerable fraction of the final iron is obtained in the form of mill scale, which is not lost, being utilized in the puddling forge, or for smelting, etc.; the rest is obtained in the form of cuttings, 'crop ends," and "scrap" of various kinds, often not very largely inferior in value to the bar iron. So-called com- Average. Iron (by differ- 26. Puddled Steel and Natural Steel.-If in the operation of converting pig iron into malleable iron by puddling in a reverberatory furnace the process be stopped before the decarbonization is complete (the Natural steel is to refine pig iron (323) in the inverse temperature of the furnace being a little lower, so that relation that puddled iron is to puddled steel: the last the partial solidification of the mass on decarbonization is derived from pig iron by stopping the decarbonization -"coming to nature"-takes place more easily), the at a stage before it is complete; the first is obtained by resulting metal is a more or less carbonized iron, which, carrying the refining process somewhat further than when prepared from pig free from any large quantity the stage usually attained in the refinery. The forge of sulphur and phosphorus, is susceptible of many of or hearth used for natural steel making is substantially the applications to which steel is put. Considerable like that employed for refining, a brasqued bottom of skill in manipulation is necessary in order to obtain charcoal dust being put on, and the pig iron melted anything at all approaching to a uniform product, the down and gradually decarbonized by the conjoined tendency being towards the production of a mass with action of an inclined blast blowing downwards upon lumps of soft wholly decarbonized iron, and sometimes it and of the cinder floating above it; if the decarof but little decarbonized pig irregularly distributed bonization is carried too far a little fresh pig is added through it. This is best overcome by conducting the to recarbonize the whole. The details of the manipdecarbonization more slowly and at a somewhat lower ulation (upon the mode of performance of which the temperature than is usually done in ordinary puddling, character of the resulting product depends) vary in and using less fettling and a less oxidizing atmosphere. different localities; thus Tünner describes five distinct A manganiferous pig is almost essential to the obtain-modifications practised in Siegen, Tyrol, Carinthia, and ing of a good product, first because the oxidation of Styria; save in these districts the manufacture of this the manganese gives a more fluid slag, and secondly class of steel is but small. The bars ultimately formed because the small quantity retained by the product de- from the blooms are usually hammered out by hand For further creases the injurious effects of sulphur, phosphorus, entirely, and not machine rolled at all. etc., on the physical properties of the metal. details see Percy's Metallurgy. 27. Bessemer's (Original) Process.-The method usually known in this country as "Bessemer's pro The manufacture of puddled steel in England is now but small, the Bessemer and Siemens-Martin processes having largely superseded it. Occasionally, however, substances apparently consisting of badly puddled iron, and possessing some degree of hardening power, are sold under the name of steel; but, not having been fused so as to give uniformity of composition, these products are incapable of being used advantageously for purposes for which the elasticity and capability of resisting wear and tear possessed by good steels are essential. The want of a definite understanding as to whether the term "steel" is nowadays to be understood as implying that the product has been completely fused (as maintained by some, see 3) or not leads occasionally to disputes and lawsuits, when inferior kinds of "puddled steel," or badly decarbonized puddled iron, are supplied under the terms of a contract which simply mentions "steel" as the character of the metal to be supplied, without precisely stating its nature, quality, or properties, or the mode of its production. On the Continent, puddled steels made from pig of pure qualities so far as sulphur and phosphorus are concerned cess "of steel making does not, strictly speaking, belong to the class of methods now under discussion, being a combination-process consisting of two parts:one the Bessemer process proper, of which the essential feature is the conversion of cast iron into wrought iron by the method (due to Bessemer) of forcing air through the molten mass so as to burn out the carbon; the other (due to Mushet) consisting of the conversion of the molten wrought iron thus obtained into steel by mixing with it a suitable proportion of fused carbonized iron containing manganese, in the form of spiegeleisen or ferro-manganese; this combination process is discussed more fully in 36. The decarbonizing and desiliconizing of iron by the action of an oxidizing atmosphere is the essential feature of the processes of refining pig iron (223) and of making natural steel (2 26); but prior to 1855 these processes had |