Читать книгу Henley's Formulas, Recipes and Processes (Applied Chemistry) - Various - Страница 182

—This is prepared by melting the finest copper in a crucible, and adding the aluminum. The copper is cooled thereby to the thickly fluid point, but at the moment of the combination of the two metals, so much heat is released that the alloy becomes white hot and thinly fluid. Aluminum bronze thus prepared is usually brittle, and acquires its best qualities only after having been remelted several times. It may be remarked that, in order to obtain a bronze of the best quality, only the very purest copper must be used; with an inferior quality of copper, all labor is wasted. Aluminum bronze is not affected by exposure to the air; and its beautiful color makes it very suitable for manufacturing various ornamental articles, including clock cases, door knobs, etc.

Aluminum bronze wire is almost as strong as good steel wire, and castings made from it are almost as hard as steely iron; its resistance to bending or sagging is great.

I.—A good formula is 90 to 95 per cent of aluminum and 5 to 10 per cent of copper, of golden color, which keeps well in the air, without soon becoming dull and changing color like pure copper and its alloys with tin and zinc (bronze, brass, etc.). It can be cast excellently, can be filed well and turned, possesses an extraordinary hardness and firmness, and attains a high degree of polish; it is malleable and forgeable. On the latter quality are founded applications which were formerly never thought of, viz.: forged works of art for decorative purposes. An alloy of 95 parts aluminum and 5 parts copper is used here. The technical working of bronze is not materially different from that of iron. The metal, especially in a hot condition, is worked like iron on the anvil, with hammer and chisel, only that the temperature to be maintained in forging lies between dark and light cherry red. If the articles are not forged in one piece and the putting together of the separate parts becomes necessary, riveting or soldering has to be resorted to. Besides forging, aluminum bronze is well suited for embossing, which is not surprising considering the high percentage of copper. After finishing the pieces, the metal can be toned in manifold ways by treatment with acid.

II.—Copper, 89 to 98 per cent; aluminum and nickel, 1 to 2 per cent. Aluminum and nickel change in the opposite way, that is to say, in increasing the percentage of nickel the amount of aluminum is decreased by the equal quantity. It should be borne in mind that the best ratio is aluminum, 9.5 per cent; nickel, 1 to 1.5 per cent at most. In preparing the alloy a deoxidizing agent is added, viz., phosphorus to 0.5 per cent; magnesium to 1.5 per cent. The phosphorus should always be added in the form of phosphorous copper or phosphor aluminum of exactly determined percentage. It is first added to the copper, then the aluminum and the nickel, and finally the magnesium, the last named at the moment of liquidity, are admixed.

III.—A gold bronze, containing 3 to 5 per cent aluminum; specific gravity, 8.37 to 8.15. Handsome golden color. This alloy oxidizes less on heating than copper and iron, and is therefore especially adapted for locomotive fireboxes and spindles, etc.

IV.—A steel bronze containing on an average 8.5 per cent aluminum (including 1 per cent silicium); specific gravity, 7.7. Very ductile and tough, but slightly elastic; hence its use is excluded where, with large demands upon tension and pressure, no permanent change of form must ensue. This is changed by working, such as rolling, drawing, etc. {57} Especially useful where infrangibility is desired, as in machinery, ordnance, etc. At high temperature this bronze loses its elasticity again.

V.—This contains 8.5 per cent aluminum and 1 ¹/₂ to 2 per cent silicium. Its use is advisable in cases where the metal is to possess a good elasticity, even in the cast state, and to retain it after being worked in red heat.

VI.—An acid bronze, containing 10 per cent aluminum; specific gravity, 7.65. Especially serviceable to resist oxidation and the action of acids.

VII.—Diamond bronze, containing 10 per cent aluminum and 2 per cent silicium. Specific gravity, 7.3. Very hard; of great firmness, but brittle.