BRASS

( Laiton , cuivre jaune , Fr.; Me ing , Germ.) An alloy of copper and zinc. It was formerly manufactured by cementing granulated copper, called bean-shot , or copper clippings, with calcined calamine (native carbonate of zinc) and charcoal, in a crucible, and exposing them to bright ignition. Three parts of copper were used for three of calamine and two of charcoal. The zinc reduced to the metallic state by the agency of the charcoal, combined with the copper, into an alloy which formed, on cooling, a lump at the bottom of the crucible. Several of these, being remelted and cast into moulds, constituted ingots of bra for the market. James Emerson obtained a patent, in 1781, for making bra by the direct fusion of its two metallic elements, and it is now usually manufactured in this way. It appears that the best proportion of the constituents to form fine bra is one prime equivalent of copper = 63 1 ⁄ 2 + one of zinc = 32·3; or very nearly 2 parts of copper to 1 of zinc. The bright gold coloured alloy, called Prince’s, or Prince Rupert’s metal, in this country, consists apparently of two primes of zinc to one of copper, or of nearly equal parts of each. Bra , or hard solder, consists of two parts of bra and one of zinc melted together, to which a little tin is occasionally added; but when the solder must be very strong, as for bra tubes that are to undergo drawing, two thirds of a part of zinc are used for two parts of bra . Mosaic gold, according to the specification of Parker and Hamilton’s patent consists of 100 parts of copper, and from 52 to 55 of zinc; which is no atomic proportion. Bath metal is said to consist of 32 parts of bra and 9 parts of zinc. The button manufacturers of Birmingham make their plat in with 8 parts of bra and 5 of zinc; but their cheap buttons with an alloy of copper, tin, zinc, and lead. Red bra , the Tombak of some, (not of the Chinese, for this is white copper,) consists of more copper and le zinc than go to the composition of bra ; being from 2 1 ⁄ 2 to 8 or 10 of the former to 1 of the latter. At the famous bra works of Hegermühl, to be presently described, 11 parts of copper are alloyed with 2 of zinc into a red bra , from which plates are made that are afterwards rolled into sheets. From such an alloy the Dutch foil, as it is called, is manufactured at Nürnberg; Pinchbeck, Similor, Mannheim gold, are merely different names of alloy similar to Prince’s metal. The last consists of 3 of copper and 1 of zinc, separately melted, and suddenly incorporated by stirring.— Wiegleb. In the proce of alloying two metals of such different fusibilities as copper and zinc, a considerable waste of the latter metal by the combustion, to which it is so prone, might be expected; but, in reality, their mutual affinities seem to prevent the lo , in a great measure, by the speedy absorption of the zinc into the substance of the copper. Indeed, copper plates and rods are often bra ed externally by exposure, at a high temperature, to the fumes of zinc, and afterwards laminated or drawn. The spurious gold wire of Lyons is made from such rods. Copper ve els may be superficially converted into bra by boiling them in dilute muriatic acid, containing some wine stone and zinc amalgam. The first step in making bra is to plunge slips of copper into melted zinc till an alloy of somewhat difficult fusion be formed, to raise the heat, and add the remaining proportion of the copper. The bra of the first fusion is broken to pieces, and melted with a fresh quantity of zinc, to obtain the finished bra . Each melting takes about 8 or 9 hours. The metal is now cast into plates, about 40 inches long by 26 inches broad, and from one third to one half inch thick. The moulds are, in this case also, slabs of granite mounted in an iron frame. Granite appears to be preferred to every thing else as a mould, because it preserves the heat long, and by the asperities of its surface, it keeps hold of the clay lute applied to secure the joinings. The cast plates are most usually rolled into sheets. For this purpose they are cut into ribands of various breadths, commonly about 6 1 ⁄ 2 inches. The cylinders of the bra rolling-pre are generally 46 inches long, and 18 inches in diameter. The ribands are first of all pa ed cold through the cylinders; but the bra soon becomes too hard to laminate. It is then annealed in a furnace, and, after cooling, is pa ed afresh through a rolling pre . After paring off the chipped edges, the sheets are laminated two at a time: and if they are to be made very thin, even eight plates are pa ed through together. The bra in these operations must be annealed 7 or 8 times before the sheet arrives at the required thinne . These succe ive heatings are very expensive; and hence they have led the manufacturers to try various plans of economy. The annealing furnaces are of two forms according to the size of the sheets of bra . The smaller are about 12 feet long, with a fire place at each end, and about 13 inches wide. The arch of the furnace has a cylindrical shape, whose axis is parallel to its small side. The hearth is horizontal, and is made of bricks set on edge. In the front of the furnace there is a large door, which is raised by a lever, or chain, and counterweight, and slides in a frame between two cheeks of cast iron. This furnace has, in general, no chimney, except a vent slightly raised above the door, to prevent the workmen being incommoded by the smoke. Sometimes the arch is perforated with a number of holes. The sheets of bra are placed above each other, but separated by parings, to allow the hot air to circulate among them, the lowest sheet resting upon two bars of cast iron placed lengthwise. The large furnaces are usually 32 feet long, by 6 1 ⁄ 2 feet wide, in the body, and 3 feet at the hearth. A grate, 13 inches broad, extends along each side of the hearth, through its whole length, and is divided from it by a small wall, 2 or 3 inches high. The vault of the furnace has a small curvature, and is pierced with 6 or 8 openings, which allow the smoke to pa off into a low bell-chimney above. At each end of the furnace there is a cast-iron door, which slides up and down in an iron frame, and is poised by a counterweight. On the hearth there is a kind of railway, composed of two iron bars, on the grooves of which the carriage moves with its loads of sheets of bra . These sheets, being often 24 feet long, could not be easily moved in and out of the furnace; but as bra laminates well in the cold state, they are all introduced and moved out together. With this view, an iron carriage is framed with four bars, which rest on four wheels. Upon this carriage, of a length nearly equal to that of the furnace, the sheets are laid, with bra parings between them. The carriage is then raised by a crane to a level with the furnace, and entered upon the grooved bars which lie upon the hearth. That no heat may be lost, two carriages are provided, the one being ready to put in as the other is taken out; the furnace is meanwhile uniformly kept hot. This method, however convenient for moving the sheets in and out, wastes a good deal of fuel in heating the iron carriage. The principal places in which bra is manufactured on the great scale in England, are Bristol, Birmingham, and Holy well, in North Wales. The French writers affirm, that a bra , containing 2 per cent. of lead, works more freely in the turning lathe, but does not hammer so well as the mere alloy of copper and zinc. At the bra manufactory of Hegermühl, upon the Finon canal near Potsdam, the following are the materials of one charge; 41 pounds of old bra , 55 pounds refined copper (gahrkupfer) granulated; and 24 pounds of zinc. This mixture, weighing 120 pounds, is distributed into four crucibles, and fused in a wind furnace with pitcoal fuel. The waste varies from 2 1 ⁄ 2 to 4 pounds upon the whole. IMG:4147767755307473660_illo0167a.png:Bra furnace Fig. 159. represents the furnace as it was formerly worked there with charcoal; a , the laboratory in which the crucibles were placed. It was walled with fire bricks. The foundations and the filling-in walls were formed of stone rubbish, as being bad conductors of heat; sand and ashes may be also used; b , cast-iron circular grating plates pierced with 12 holes (see fig. 160. ), over them a sole of loam, c , is beat down, and perforated with holes corresponding to those in the iron discs; d , the ash-pit; e , the bock , a draught flue which conducts the air requisite to the combustion, from a sunk tunnel, in communication with several melting furnaces. The terrace or crown of the furnace, f , lies on a level with the foundry floor, h h , and is shut with a tile of fire-clay, g , which may be moved in any direction by means of hooks and eyes in its binding iron ring. Fig. 161. the tongs for putting in and taking out the charges, as viewed from above and from the side. IMG:4147767755307473660_illo0167b.png:Modern bra furnaces Figs. 162 , 163. represent the furnaces constructed more recently for the use of pitcoal fuel; fig. 162. being an upright section, and fig. 163. the ground plan. In this furnace the crucibles are not surrounded with the fuel, but they receive the requisite melting heat from the flame proceeding from the grate upon which it is burned. The crucibles stand upon 7 binding arches, a , which unite in the middle at the key-stone b , fig. 163. Between the arches are spaces through which the flame rises from the grate c . d is the fire-door; e , a sliding tile or damper for regulating or shutting off the air-draught; f an inclined plane, for carrying off the cinders that fall through the grate, along the draught tunnel g , so that the air in entering below may not be heated by them. The crucibles are 16 inches deep, 9 1 ⁄ 2 wide at the mouth, 6 1 ⁄ 2 at the bottom; with a thickne in the sides of 1 inch and 1 1 ⁄ 2 below; they stand from 40 to 50 meltings. The old bra , which fills their whole capacity, is first put in and melted down; the crucibles are now taken out, and are charged with the half of the zinc in pieces of from 1 to 3 cubic inches in size, covered over with coal ashes; then one half of the copper charge is introduced, again coal-dust; and thus the layers of zinc and copper are distributed alternately with coal-ashes betwixt them, till the whole charge gets finally fused. Over all, a thicker layer of carbonaceous matter is laid, to prevent oxidize ment of the bra . Eight crucibles filled in this way are put into the furnace between the 11 holes of the grate shelf; and over them two empty crucibles are laid to be heated for the casting operation. In from 3 1 ⁄ 2 to 4 hours the bra is ready to be poured out. Fifteen English bushels of coals are consumed in one operation; of which six are used at the introduction of the crucibles, and four gradually afterwards. When sheet bra is to be made the following proce is pursued :— An empty crucible, called a caster ( gie er ), is taken out of the furnace through the crown with a pair of tongs, and is kept red hot by placing it in a hollow hearth ( mundal ), surrounded with burning coals; into this crucible the contents of four of the melting pots are poured; the dro being raked out with an iron scraper. As soon as the melting pot is emptied, it is immediately re-charged in the manner above described, and replaced in the furnace. The surface of the melted bra in the caster is swept with the stump of a broom, then stirred about with the iron rake, to bring up any light foreign matter to the surface, which is then skimmed with a little scraper; the crucible is now seized with the casting tongs, and emptied in the following way :— IMG:4147767755307473660_illo0168a.png:Casting mould The mould or form for casting sheet bra consists of two slabs of granite, a a , figs. 164 , 165. They are 5 1 ⁄ 2 feet long; 3 feet broad, 1 foot thick, and, for greater security, girt with iron bands, b b , 2 inches broad, 1 1 ⁄ 2 thick, and joined at the four corners with bolts and nuts. The mould rests upon an oaken block, c , 3 1 ⁄ 2 feet long, 2 1 ⁄ 6 broad, and 1 1 ⁄ 4 thick, which is suspended at each end upon gudgeons, in bearing blocks, placed under the foundery floor, d d , in the casting pit, e e . This is lined with bricks; and is 6 3 ⁄ 4 feet long, 5 1 ⁄ 2 broad, and 2 deep; upon the two long side walls of the pit, the bearing blocks are laid, which support the gudgeons. The swing-blocks are 10 inches long, 18 inches broad, 15 inches thick, and are somewhat rounded upon their back edge, so that the casting frame may slope a little to the horizon. To these blocks two cro wooden arms, f f , are mortised, upon which the under slab rests, freely, but so as to project about 5 inches backwards over the block, to secure an equipoise in the act of casting. g g are bars, placed at both of the long sides, and one of the ends, between the slabs, to determine the thickne of the bra -plate. Upon the other slab the gate h is fastened, a sheet of iron 6 inches broad, which has nearly the shape of a parallel trapezium (lozenge), and slopes a little towards the horizon. It serves for setting the casting pot upon in the act of pouring out, and renders its emptying more convenient. That gate ( steinmaul ) is coated with a mixture of loam and hair. The upper slab is secured to the under one in its slanting position by an armour or binding. This consists of the tension bars of wood, i k l m , of the iron bars n , (3 to 3 1 ⁄ 2 inches broad, 1 1 ⁄ 2 inch thick, see the top view, fig. 165. ) of a rod with holes and pins at its upper end, and of the iron screw spindle o . The mode in which these parts act may be understood from inspection of the figure. In order to lift the upper slab from the under one, which is effected by turning it round its edge, a chain is employed, suspending two others, connected with the slab. The former pa es over a pulley, and may be pulled up and down by means of a wheel and axle, or with the aid of a counterweight. Upon each of the two long sides of the slab there are two iron rings, to which the ends of the chains may be hooked. The casting faces of the slab must be coated with a layer of finely ground loam; the thinner the better. When calamine is employed, 1 ⁄ 2 cwt. of copper, 3 ⁄ 4 cwt. of calamine, and 1 ⁄ 3 the volume of both of charcoal mixed, are put into 7 crucibles, and exposed to heat during 11 or 12 hours; the product being from 70 to 72 lbs. of bra .