CHAPTER XI.

FORGING IRON AND STEEL.

SECT. I.-GENERAL VIEW OF THE PRACTICE OF FORGING IRON AND STEEL.

In entering upon this subject, which performs so important and indispensable a part in every branch of mechanical industry, I propose first to notice some of the general methods pursued, commencing with the heaviest works, and gradually proceeding to those of the smallest proportions. This arrangement is principally adopted that the apparatus, which undergo a corresponding change in their kind and dimensions, may be adverted to.

After this, the management of the fire, and the degrees of heat required for various purposes, will be described; and then the elementary practice of forging will be attempted: I shall first speak of those works made principally in one piece, and afterwards of such as are composed of two or more parts, and which require the operation of welding.

The heaviest works of all, are generally heated in air furnaces of various descriptions, some of which resemble but greatly exceed in size those employed in the works where iron is manufactured, and in which the process of forging may be truly considered to commence with the very first blow given upon the ball, as it leaves the puddling furnace for being converted into a bloom.

At these works, in addition to the ordinary manufactures of bar, plate, and hoop iron in all their varieties, the hammermen are employed in preparing masses, technically called "uses," which mean pieces to be used in the construction of certain large works, by the combination or welding of several of these masses. A square shaft, to be used at an iron-works in Wales,

also consult with advantage, Aikin's "Illustrations of Arts and Manufactures," and various articles in the Encyclopedias, &c. &c.

196

LARGEST PADDLE SHAFTS.

was made by laying together sixteen square pieces, measuring collectively about twenty-six inches square, and six feet long. These were bound together, and put into a powerful air furnace, and the ends of the group were welded into a solid mass under the heavy hammer weighing five tons; the weld was afterwards extended throughout the length. The cylindrical paddle-shafts of the largest steam-ships are wrought in a similar manner, and when their dimensions require it, these enormous works are extended by successive additions at the one end to any required length occasionally, as in the instances referred to, the entire mass is composed of scrap iron to ensure its being of the best possible quality, and the material is scarcely cold from the commencement of the process until its completion*.

These ponderous masses are managed with far more facility than might be expected by those who have never witnessed such interesting proceedings. First, the "heat" has a long iron rod attached to it in continuation of its axis, to serve as a 'porter" or guide rod; the mass is suspended under a traversing crane at that point where it is nearly equipoised, the crane not only serves to swing it round from the fire to the hammer, but the traverse motion also moves the work endways upon the anvil, and small changes of elevation are sometimes effected by a screw adjustment in the suspending chain. The circular form is obtained by shifting the work round upon its axis by means of a cross lever fixed upon the porter, and moved by one or two men, so as to expose each part of the circumference to the action of the helve; this is readily done as the crane terminates in a pulley, around which an endless band of chain is placed, and the work lies within the chain, which shifts round when the work is turned upon the anvil: the precision of the forgings produced by these means is very surprising.

A similar mode of work is adopted on a smaller scale for

*The above remarks refer to the paddle shafts of engines, such as those built by Messrs. Maudslays for the "Great Western" steam-ship, consisting of three pieces connected as usual by drag links. The center piece, or middle length, was 12 feet long, the two outer, or the paddle shafts, were 22 feet long each, the largest or the central diameter was 18 inches, and they tapered off to 12 inches at the smallest or the external parts, the bearings being 16 and 15 inches diameter. The collective weight of the three pieces was near 20 tons, and their value upwards of a thousand pounds before they left the forge of Messrs. Acraman's of Bristol, at which they were made.

SMALLER SHAFTS; SCRAP IRON; SMITH'S HEARTH.

197

many of the spindles, shafts, and other parts of ordinary mechanism, which are forged under the great hammer, often of several bars piled together and faggoted; a suitable term, as they are frequently made of a round bar in the center, and a group of bars of angular section, called mitre iron, around the same, which are temporarily wedged within a hoop, somewhat after the manner of a faggot of wood. Such works are likewise made of scrap-iron, which consists of a strange heterogeneous medley of odd scraps and refuse from a thousand works, scarcely two pieces of which are alike.

A number of these fragments are enveloped in an old piece of sheet iron, and held together by a hoop, the mass is raised to the welding heat in a blast or air furnace, and the whole is consolidated and drawn down under the tilt-hammer; one long bar that serves as the porter being welded on by the first blow. The mingling of the fibres in the scrap-iron is considered highly favourable to the strength of the bar produced. The scrap-iron is sometimes twisted during the process of manufacture, to lay all the filaments like a rope, and prevent the formation of spills, or the longitudinal dirty seams found on the surface of inferior iron.

Sometimes the formation of the scrap iron is immediately followed by the production of the shafts and other heavy works for which it is required; at other times the masses are elongated into bars sold under the name of scrap-iron, although it is very questionable if all that is so-named is produced in the manner implied.

The long furnaces are particularly well suited for straight works and bars, but when the objects get shorter and of more complex figures, the open fire or ordinary smith's hearth is employed. This, when of the largest kind, is a trough or pit of brickwork about six feet square, elevated only about six inches from the ground; the one side of the hearth, is extended into a vertical wall leading to the chimney, the lower end of which terminates in a hood usually of stout plate iron, which serves to collect the smoke from the fire. The back wall of the forge is fitted with a large cast-iron plate, or a back, in the center of which is a very thick projecting nozzle also of iron, perforated for admitting the wind used to urge the fire; the aperture is called the tuyere.

198

LARGE HEARTH; ANCHORS; VERTICAL HAMMER.

The blast is sometimes supplied from ordinary bellows of various forms; at other times, as at the Woolwich dock-yard, by a series of enormous air-pumps, which lead into another cylinder or regulator, the piston of which is loaded with weights, so as to force the air through tubes all over the smithy, and each fire has a valve to regulate its individual blast; but the more modern and general plan is the revolving fan, also worked by the engine, the blast from which is similarly distributed.

In some cases the cast-iron forge back is made hollow, that a stream of water may circulate through it from a small cistern; the water-back is thereby prevented from becoming so hot as the others, and its durability is much increased. In other cases the air, in its passage from the blowing apparatus, flows through chambers in the back plate so as to become heated in its progress, and thus to urge the fire with hot blast, which is by many considered to effect a very great economy in the fuel.

Some heavy works of rather complex form, such as anchors, &c. are most conveniently managed by hand forging; many of these require two gangs of men with heavy sledge hammers, each consisting of six to twelve, who relieve each other at short intervals, as the work is exceedingly laborious. Their hammers are swung round and made to fall upon one particular spot, with an uniformity that might have suggested to the immortal Handel the metre of his " Harmonious Blacksmith,” but not certainly the melody; the conductor of this noisy, although dumb concert so far as relates to voice, stands at a respectful distance, and directs the blows of his assistants with a long wooden wand. The Hercules or crane, used for transferring the work from the fire to the anvil, which is at about the same elevation as the fire itself, is still retained.

The square shanks of anchors are partly forged under a vertical hammer of very simple construction, called a "monkey." It consists of a long iron bar running very loosely through an eye or aperture several feet above the anvil, and terminating at foot in a mass of iron, or the ram. The hammer is elevated by means of a chain attached to the rod, and also to a drum overhead, which is put into gear with the engine, and suddenly released by a simple contrivance, when the hammer has reached the height of from two to five feet, according to circumstances. The ram is made to fall upon any precise spot indicated by the

SMALLER WORKS AND HEARTHS.

199

wand of the foreman, as it has a horizontal range of some twenty inches from the central position, it is guided by two slight gye rods, hooked to the ram and placed at right angles; the gyes are held by two men, who watch the directions given. This contrivance is far more effective than the blows of the sledge hammers, and although now but little used is perhaps more suitable to such purposes than the helve or lift hammer, which always ascends to one height, and falls upon one fixed spot.

The square shank of the anvil, and works of the same section, are readily shifted the exact quarter circle, as the sling-chain is made with flat links, each a trifle longer than the side of the square of the work, which therefore bears quite flat upon one link, and when twisted it shifts the chain the space of a link,

and rests as before.

Many implements and tools, such as shovels, spades, mattocks, cleavers, &c. are partly forged under the tilt-hammer; the preparatory processes, called moulding, which include the insertion of the steel, are done by ordinary hand forging. The objects are then spread out under the broad face of the tilt-hammer, the workman in such cases being sometimes seated on a chair suspended from the ceiling, and by paddling about with his feet, he places himself with great dexterity in front or on either side of the anvil with the progressive changes of the work; the concluding processes are mostly done by hand with the usual tools. A similar arrangement is also adopted in tilting small sized steel. With the reduction of size in the objects to be forged, the number of hands is also lessened, and the crane required for heavy work is abandoned for a chain or sling from the ceiling, but for the majority of purposes two men only are required, when the work is said to be two-handed. The principal or the fireman, takes the management of the work both in the fire and upon the anvil; he directs and assists with a small hammer of from two to four pounds weight; the duty of his mate is to blow the bellows and wield the sledge-hammer, that weighs from about ten to fourteen pounds although sometimes more, from which he derives his name of hammerman.

As the works to be forged become smaller, the hearth is gradually lessened in size, and more elevated, so as to stand about two and a half feet from the ground: it is now built hollow, with an arch beneath serving as the ash-pit to receive