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The history of alloys

Copper and its alloys were probably the first metals to be employed by man, over 5,000 years ago, and they have since played an important part in every phase of his activities. The casting of these alloys is, therefore, the oldest branch of all the basic foundry industries and plays a vital part in engineering, science and architecture.

The art of alloying copper with other non ferrous metals and the casting of the alloy to achieve the desired shape, appearance and physical properties has been practised and utilised for hundreds of years. During many centuries foundrymen have remelted and used over and over again the alloys found in many forms of castings which have outlived their usefulness or fashion.

In those early days, the foundrymen would select from his stock of scraps, pieces which he considered suitable for the new casting he was making. This selection was a much simpler and less responsible one than it is today.

Specialisation has created a demand for many particular alloys often of unusual composition and physical properties. These special alloys ultimately return as scrap metal, and although a particular piece of scrap has its own analytical characteristics, more often the assembly of the part or its associated scrap will contain many different alloys. For instance, present day stocks of scrap comprise such complex alloy groups classed under general headings as silicon bronze, nickel bronze, gunmetals, aluminium bronze, manganese bronze, phosphor bronze etc., all mixed together. Each group, of course has a very wide analytical range. As specialisation increases, it is to be expected that collected scrap will become even more mixed with these special alloys; scrap, too is seldom clean, often being contaminated with dirt, grease, paint or plating.

Nevertheless, whilst the metal contained in all this scrap has a definite value, only those specialist organisations which are competent and equipped to select and refine scrap metals can process them without loss or reduction of their varied and intrinsic values.

The production of reliable quality ingots requires scientifically controlled melting, refining and alloying processes under the supervision of trained metallurgists. Economically it is necessary to handle large tonnages at one time, and refine the molten metal in bulk by the addition of proper slag-forming fluxes and other materials. The molten metal must be analysed chemically, and tested physically, and any necessary adjustments made to produce the required analytical composition and physical properties before casting into ingots. During the casting process, samples must be taken at regular intervals and checked so that the quality of the final product is completely controlled.

Ingots produced from refined used metals are often classed as "secondary metals." Such production implies an added guarantee of quality and consistency. When pure metals are originally produced from ores many impurities have to be removed, but, for particular purposes, some elements may be added back to make particular alloys; this secondary refining controls and prevents their unwarranged re-entry into the foundry.

It it of national importance that scrap metal should be consumed correctly and that the by-products of the refining processes should not be wasted. It would, of course, be economically impossible, and unnecessary, to use virgin metals which would require to be pre-alloyed for the majority of castings.

It is not always realised that great technical advances in the manufacture of copper-base alloy ingots from reclaimed metal have been made during very recent years and that, with their varied specification limits, they are recognised as engineering materials by all the Government bodies and principal engineering concerns in this and other countries.

 



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