Joseph Gregory Horner

“ Yet again, die forging is a very elastic system, and herein lies much of its value. Though it reaches its highest development when thousands of similar pieces are wanted, it is also adaptable to a hundred, or even to a dozen, similar forgings. In such cases economy is secured by using dies of a very cheap character; or, by employing such dies as supplementary to anvil work for effecting neat finish to more precise dimensions than can be ensured at the anvil. ”

“ A white hot mass of metal can be placed in a matrix, and stamped into shape in a few blows under a hammer with as much ease as a medal can be stamped in steel dies under a coining press. But much detail is involved in the translation of the principle into practice. The parallel between coining dies and forging dies does not go far. The blank for the coin is prepared to such exact dimensions that no surplus material is left over by the striking of the coin, which is struck while cold. ”

“ But the blank used in die forging is generally a shapeless piece, taken without any preliminary preparation, a mere lump, a piece of bar or rod, which may be square or round irrespective of whether the ultimate forging is to be square, or round, or flat or a combination of forms. At the verge of the welding heat to which it is raised, and under the intensity of the impact of hammer blows rained rapidly on the upper die, the metal yields like lead, and flows and fills the dies. ”

“ A weld joint must as a rule be fluxed, or metal will not adhere to metal. There is not, however, the absolute need for fluxing that there is in soldered joints, and many welds in good fibrous iron are made without a flux. But the explanation here is that the metal is brought to a temperature of semifusion, and the shapes of joints are generally such that particles of scale are squeezed out from between the joint in the act of closing the weld. ”

“ When portions which differ greatly in dimensions have to be united, welding is the only method practicable at the anvil. It is also generally the best to adopt when union has to be Welding. made between pieces at right angles, or when a piece on which much work has to be done is required at the end of a long plain bar, as in the tension rods of cranes and other structures with eyes. The art of welding depends chiefly on having perfectly clean joint faces, free from scale, so that metal can unite to metal ”

“ The production of wrought iron has been a diminishing industry for many years, while that of steel increases. Though the plant employed for both is alike in essential principles of design, the growth in the use of steel has revolutionized the practice, chiefly on account of the more massive dimensions in which steel sections are rolled. ”

“ The hard solders are the spelter and the silver solders. Soft spelter solder is composed of equal parts of copper and zinc, melted and granulated and passed through a sieve. As some of the zinc volatilizes the ultimate proportions are not quite equal. The proportion of zinc is increased if the solder is required to be softer or more fusible. A valuable property of the zinc is that its volatilization indicates the fusing of the solder. Silver solder is used for jewelry and other fine metal work, arid has the advantage of high fusing points. ”

“ In the two-high mill it is clear that if the direction of the rotation of the rolls is always the same, then the plate being rolled must be taken back after each “pass” to the front of the rolls. Hence there is one “lost pass” for every reduction in thickness. This is the case in the “pull-over” mill, nearly obsolete. In the two-high reversing mill, introduced to avoid this “lost pass,” as soon as a plate has gone through, the direction of rotation of the rolls is reversed, and the plate is rolled again on the backward, journey, so avoiding the lost ”

“ The dies used for some of these are massive, and a single squeeze from the ram of the hydraulic press employed bends the steel plate between the dies to shape at once. Fairly massive forgings are also produced in these presses.
Die forging in its highest developments invades the craft of the skilled smith. In shops where it is adopted entirely, the only craftsmen required are the few who have general charge of the shops. The men who attend to the machines are not smiths, but unskilled helpers. ”

“ Little proof is needed to show that the various operations done at the anvil might be performed in a more expeditious way by the aid of power-operated appliances; for the elementary processes of reducing, and enlarging, bending, punching, &c., are extremely simple, and the most elaborate forged work involves only a repetition of these. The fact that the material used is entirely plastic when raised to a white heat is most favourable to the method of forging in matrices or dies. ”

“ In later heavier practice, rolls of cast steel and forged steel are becoming common. They are more costly than iron, but more durable and much lighter for equal strength. They are essential in armour 'plate rolls. The length of rolls should not exceed about four times their diameter, for otherwise they are liable to spring and produce plates thicker at the centre than towards the edges. ”

“ The ends are upset or enlarged in order to leave enough metal to be dressed down flush, by swaging or by flattering. The proportional lengths of the joint faces shown are those which conform to good practice. The fluxes used for welding are numerous. Sand alone is generally dusted on wrought iron, but steel requires borax applied on the joint while in the fire, and also dusted on the joint at the anvil and on the face of the latter itself. ”

“ Stripping means that when a considerable amount of fin has been formed, it is removed by laying the forging on a die pierced right through with an opening of the same shape and area as the forging, and then dealing the forging a blow with the hammer. The forging is thus knocked through the die, leaving the severed or stripped fin behind. The forging is then returned to the dies and again treated, and the stripping may be repeated twice, or even oftener, before the forging can be completed. ”

“ There is no limit in reason to the dimensions in which steel sections can be rolled, and they are never piled, however large, but always rolled from solid cast ingots. When steel ingots are rolled into sectional forms the reduction in transverse dimensions is very great. ”

“ Armour plate-mills are a special design for massive plates and sheet-mills are for thin plates or sheets having a less thickness than § in. Armour plate-mills are of twohigh reversing type usually, with forged steel rolls. They are of immense proportions, the rollers ranging from IO to 14 ft. in length, by from 3 to 4 ft. in diameter. In sheet-mills, on the other hand, two systems. English practice retains the two-high reversing mill for all heavy work, the exceptions being those just noted. American practice retains the three-high mill. ”

“ By “sectional forms IS meant all those which are not plates and sheets, such as bars of round and square section, angles, channels, rails and allied sections (fig. I) , for the production of which grooved rolls are required. The shapes and proportions of these grooves are such that reduction is effected very gradually. When metal is squeezed or hammered, one effect is to spread it laterally, since the metal cannot be appreciably squeezed in on itself. But the lateral extension is very muc less than the longitudinal. The most marked effect of reduction in thickness is extension in length. ”

“ Bending is effected either by the hammer or by the simple exercise of leverage, the heated bar being pulled round a fulcrum. It is always, when practicable, preferable to cutting out a curved or angular shape with a hot sett or to welding. The continuity of the fibre in iron is preserved by bending, and the risk of an Bending. imperfect weld is avoided. Hence it is a simple and safe process which is constantly being performed at the anvil. ”

“ The grooves form rectangular sections (box passes) . The top roll being raised, the ingot is passed through the largest groove; then the roll is lowered and it is passed through a second time. Then it is turned round through 90° and re-rolled. Afterwards the same processes are gone through till the last groove is reached. There is a great difference between, say, a plate and a rail, but the cogging-rolls have to be so designed as to produce blooms for varied forms. There are three principal forms: the box just noticed, the gothic and the diamond (fig. 4) , all open passes. For plates ”

“ While this is going on, the fibres of the flanges are being strained, because the rolls run at a higher speed at their peripheries than next the body. The metal is being violently thrust and drawn in different ways, so that while economy has to be studied by reducing the number of passes as much as possible, undue stress must be avoided by making the reductions as easy as is practicable. ”

“ Fluxes are either liquid or solid, but the latter are not efficient until they fuse and cover the surfaces to be united. Hydrochloric acid (spirits of salts) is the one used chiefly for soft soldering. It is “killed” by the addition of a little zinc, the resulting chloride of zinc rendering its action quiet. ”

“ But there are many large articles manufactured which do not strictly come under the term forgings, in which the aid of dies actuated by powerful hydraulic presses is utilized. These include work that is bent, drawn and shaped from steel plate, of which the fittings of railway wagons constitute by far the largest proportion. ”

“ Electric welding is largely taking the place of the hand process, but machines are required to maintain the parts in contact during the passage of the current. Butt joints are employed, and a large quantity of power is absorbed, but the output is immensely greater than that of hand-made welds. ”

“ These, with others, are employed for soft solder joints, the temperature of which rarely exceeds about 600° Fah. The best flux for zinc is chloride of zinc. For brazed joints, spelter or powdered brass is employed, and the flux is usually borax. The borax will not cover the joint until it has been deprived of its water of crystallization, and this is effected by raising it to a full red heat, when it swells in bulk, “boils,” and afterwards sinks quietly and spreads over, or into the joint. There are differences in details of working. ”

“ Also it is essential to have a temperature sufficiently high, yet not such as to overheat the metal. A dazzling white, at which small particles of metal begin to drop off, is suitable for iron, but steel must not be made so hot. A very few hammer blows suffice to effect the actual union ”

“ A certain amount of fin is squeezed out, and this is obliterated in the succeeding pass, and more formed, until in the finishing pass the amount of reduction is very slight, a surface finish being the principal result. ”

“ Then there are other alternatives.
If a long bar is required to have an enlargement at any portion of its length, not very much larger in diameter than the bar, nor of great length, upsetting is the method adopted. ”

“ That is, the edges are notched in a manner having somewhat the appearance of the dovetails of the carpenter; the notched portions overlap the opposite edges, and on alternate sides. Such joints when brazed are stronger than plain overlapping joints would be. ”