Abbildungen der Seite
PDF

Aluminium is a remarkably light metal, its specific gravity, when cast in sand, being only one-third that of wrought iron. When the metal is properly treated, the colour of aluminium, of 98% per cent. purity, is bright white, nearly like silver. It is strong, ductile, easily worked, and not liable to rust. It may be easily melted in crucibles, and its specific heat is very high. Annealed aluminium is so soft and ductile that it may be beaten and drawn into the finest leaves and threads, like silver. Castings of aluminium are greatly improved in rigidity and strength by forging. The tensile strength of aluminium per square inch is generally from 5 to 7 tons when cast and not annealed, with elongation 3 per cent. from 11 to 17 tons when hard wrought and not annealed, with elongation 4 per cent.; and from 5 to 6% per cent, when wrought and annealed, with elongation from 18 to 26 per cent. Table 153. –WEIGHT OF ONE SQUARE Foot of SHEET-ALUMINIUM. (BRITISH ALUMINIUM Co., LIMITED.)

[ocr errors][merged small][merged small]
[graphic]
[graphic]

The weight per square foot of aluminium, 1 inch thick, of 98% per cent. purity, is 13 pounds when cast, and 14 pounds when hard wrought.

The addition of a very small quantity of aluminium to cast iron, steel, and bronze, greatly improves their homogeneity, and conduces to the production of sound and close-grained castings.

Table 154.—WEIGHT IN Pounds of ONE Foot IN LENGTH of AlumiNIUM TUBEs. (BRitish ALUMINIUM Co., LIMITED.)

[ocr errors]

The hardness of aluminium varies according to its purity, the purest metal being the softest. Aluminium of 98 per cent. purity is about as hard as copper. Aluminium becomes sensibly harder the more it is worked, either by hammering, rolling, drawing, or stamping. Aluminium may be cut nearly as easily as wood with either a circularsaw or a band-saw, efficiently lubricated with either turps, petroleum, tallow, or benzine. In turning or planing aluminium, it is necessary to take small cuts, and to continually lubricate with either turps, benzine, or petroleum. In filing aluminium, single-cut files are most efficient. The files may be cleaned by dipping in a solution of caustic soda, and afterwards washing them in running water, and drying them in sawdust. The proper speed for drilling aluminium lubricated with petroleum is given at page 209, Aluminium Bronzes are tough and strong, and highly non-corrosive when exposed to sea-water. An aluminium bronze composed of aluminium 10 per cent. and copper 90 per cent., has a tensile strength in castings of 30 tons per square inch, with an elongation of 22 per cent. in 4 inches. Its specific gravity is 7.65; and its melting point is 1753° Fahr. An aluminium bronze composed of aluminium 7% per cent, copper 90% per cent, and silicon 2 per cent., has a tensile strength in castings of 27 tons per square inch, with an elongation of from 42 per cent. to 48 per cent. in 4 inches. Its specific gravity is 77. It is very tough and ductile, but its elastic limit in castings is only about 4 tons per square inch; when forged, rolled, or drawn, the elastic limit is 14 tons per square inch. An aluminium bronze composed of aluminium 5 per cent, and copper 95 per cent., has a tensile strength in castings of 25 tons per square inch, with an elongation of from 50 per cent. to 60 per cent. in 4 inches. It has a very fine gold colour. Its specific gravity is 8-2 1. An aluminium bronze composed of aluminium 2% per cent. and copper 97% per cent., has a tensile strength in castings of 20 tons per square inch, with an elongation of 40 per cent. in 4 inches. Its specific gravity is 8:31. Weight of Aluminium Bronzes.—The nickel-aluminium in column A. of the following table is composed of 95 per cent. of aluminium and 5 per cent. of nickel. The tungsten-aluminium in column B. is composed of 95 per cent. of aluminium and 5 per cent. of tungsten. The aluminium-bronze in column C. is composed of Io per cent. of aluminium and 90 per cent, of copper. The aluminium-bronze in column D. is composed of 7% per cent. of aluminium, 90% per cent. of copper, and 2 per cent. of silicon. The aluminium-bronze in column E. is composed of 5 per cent. of aluminium and 95 per cent. of copper. The aluminium-bronze in column F. is composed of 2% per cent. of aluminium and 97% per cent. of copper. The aluminium-brass in column G. is composed of 2 per cent. of aluminium, 60 per cent. of copper, and 40 per cent. of zinc.

[ocr errors]

Table 155.—ApproxiMATE Weight of ONE SQUARE Foot of CAST PLATEs of Nick EL-ALUMINIUM, TUNGstEN-ALUMINIUM, VARIot's A LUMINIUM-BRONzEs, AND of Rolled PLATEs of ALUMINIUM-BRAss.

[ocr errors]

Wolframinium is an alloy of wolfram, copper, and aluminium. Its specific gravity is 2.74. Its tensile strength is, when cast in sand, Io tons per square inch; when cast in chills, from 12 to 13 tons per square inch; when forged, 15 tons per square inch; and when rolled or drawn, from 15 to 20 tons per square inch. Its elongation when hard is from 3 to 5 per cent. ; and when annealed, from 10 to 20 per cent. It may be forged, rolled, and drawn either hot or cold ; it takes a high polish, and does not tarnish.

Romanium is an alloy of wolfram, nickel, and aluminium. Its specific gravity is 2.75. Its tensile strength is equal to that of wolframinium, but it is much harder, and also of greater elasticity. It can be worked either hot or cold ; forged, rolled, drawn, or stamped; and it is suitable for large castings, large plates and bars.

Table 156.—Wright of one Foot IN LENGTH of SFAMLEss DRAws BRAss TUBEs, contaix ING 7o PER CENT. of CoPPER AND 30 PER CENT. of ZINc. TENSILE STRENGTH, ANNEALED, About 13. To NS PER SQUARE INCH. (MUNTz's METAL Co., LIMITED.)

[ocr errors][ocr errors][ocr errors][ocr errors][ocr errors]

Note.—To find the weight of a brass tube of a given internal diameter, add the factor at the bottom of the table to the weight of a tube of similar external diameter. For instance, the weight of a brass tube of 2 inches internal diameter, of 12 I.S.W.G. in thickness, is = 2:30 + 25 = 2:55 pounds per foot in length. For brass tubes composed of 2 parts of copper and I part of zinc, multiply the weights of brass tubes in the above table by '994.

[graphic]
« ZurückWeiter »