IV

ALUMINIUM-BRASS

221

strength varying from 13 to 30 tons per square inch. Alloys with 56 to 57 per cent copper and 40 to 42 per cent zinc approach nearer 31 tons tensile strength. Mr. Robey states that aluminium-brass is composed of of 10 per cent aluminium-bronze, copper, and spelter.

Aluminium-brass is close-grained, homogeneous, and tough, with a useful tensile strength, and great elastic resistance. With regard to transverse stress, a bar of Cowles's No. 2 brass, 1 inch square and 12 inches between supports, showed a breaking load of 72 cwts.; the deflection with 44 cwts. load was 04 of an inch, and the permanent set 01. Aluminium-brass forges hot, and, owing to its special casting qualities, low specific gravity, strength, toughness, and rigidity, is very suitable for ships' propellers, rudder frames, pumps, valves, pinions, etc., as well as for hydraulic work. With regard to casting, practically the same rules apply, as those given for aluminium-bronze. Its working qualities, when the amount of aluminium is high, are similar to those of the bronze. The working qualities are also governed largely by the quantity of zinc contained in the brass--the higher the percentage of zinc, the harder the metal, and the shorter the chip which flies from the tool.

Hercules Metal.--This is a cheaper form of aluminiumbrass made by the Cowles Company. It casts well, and whilst very hard and strong, works well under the tool. It is malleable when hot, and suitable for all castings where a strong metal is required. Its tensile strength varies from 30 to 40 tons per square inch; with an elongation of 10 to 30 per cent, according to the proportions of the constituents. It contains a proportion of iron as high as 7 per cent, together with a larger proportion of spelter than in the ordinary brass.

§ 81. The following tests were made by order of the navy department of the United States, and the table shows the favourable results of aluminium bronze and brass as compared with gun-metal.1

1 Paper by Mr. Dagger, Brit. Assoc. 1889.

Approximate Composition.

IV

ALUMINIUM-BRONZE

223

Aluminium alloys containing varying proportions of nickel are made, and are said to be very ductile and to possess a tenacity of from 33 to 44 tons per square inch. Tests made by Kircaldy on similar alloys, manufactured by the "Crown Metal Company," gave results ranging from 39 to 42 tons per square inch. According to Mr. Webster, two alloys are employed by the Company for preparing the bronze, designated as aluminium alloy A and nickel alloy B. The A alloy consists of 15 parts aluminium and 85 parts tin. The B alloy consists of 17 parts nickel, 17 parts copper, and 66 parts tin. The metals are melted in the usual way with the use of a flux, under a cover of common salt and potassium chloride. The two alloys are then melted together with copper. It has been found that the bronze is the harder and better the more it contains of the two alloys, and vice versa. The following is recommended as the best proportion : copper, 88 parts, and 8 parts of each of A and B. The copper is first melted and the alloys added; the mixture is then stirred with a wooden or clay rod (an iron rod must not on any account be used) until the mass is homogeneous, as shown by a test-ingot. A second quality alloy, which is cheaper than the preceding, is composed of 92 parts copper, and 4 parts each of the alloys A and B.

One great drawback to the use of aluminium-bronzes for manufactured articles is the difficulty experienced in soldering and brazing them. The Cowles Electric Smelting Company has issued the following directions:

§ 82. Brazing.—Aluminium-bronze will braze as well as any other metal by using brass solder (copper 50 per

cent, zinc 50 per cent), and borax.

:

§ 83. Soldering.—To solder aluminium-bronze with soft solder cleanse well from dirt and grease the parts to be joined. Then place the parts to be soldered in a strong solution of sulphate of copper, and place in the bath a rod of soft iron, touching the parts to be joined. After a while a copper-like surface will be seen on the metal. Remove

from bath, rinse quite clean, and brighten the surfaces. These surfaces can then be tinned by using a fluid, consisting of zinc dissolved in hydrochloric acid, in the ordinary way, with soft solder.

Mierzinski says that Hulot uses an alloy of the usual half-and-half lead and tin solder, with 12, 25, and 50 per cent of zinc amalgam.

CHINESE AND JAPANESE BRONZES

$84. The Chinese and Japanese have attained great perfection in making bronzes for art metal-work, of which the following may be taken as typical. The first is called shakudo, and contains

The above have been used for very large works of art, such as colossal statues. Professor Roberts-Austen states that the quantity of gold is very variable, some specimens which he analysed containing only 15 per cent gold. The other alloy is termed shibu-ichi, of which there are many varieties. The precious metals are employed to produce definite results.

IV

JAPANESE BRONZE

225

The gold enables the metal to receive a beautiful rich purple "patina" or coating when treated with certain pickling solutions, while shibu-ichi possesses a silver-gray tint, which becomes very beautiful under ordinary atmospheric influences. There are three pickling solutions generally in use. They are made up respectively in the following proportions, and are used boiling:

1 "That most widely employed is No. I.

When boiled in No. III solution pure copper will turn a brownish red, and shaku-do, which contains gold, becomes purple. Copper containing a small quantity of antimony gives a very different shade to that resulting from the pickling of pure copper. But the copper produced in Japan is often the result of smelting complex ores, and the methods of purification are not so perfectly understood as in the West. The result is that the so-called 'antimony' of the Japanese art metal-workers, which is present in the variety of copper called kuromi, is a complex mixture containing tin, cobalt, and other metals, so that the operator has a varied series of materials at command with which to secure any particular shade. Each particular tint is the result of very small quantities of metallic impurity.

"Another art material termed mokumè, which signifies

1 Roberts-Austen, Jour. Soc. of Arts, 26th October 1888.