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Forging Non-Ferrous Metals and Their Alloys

Hot and cold stamping of non-ferrous metals end their alloys is widely practised in industry, particularly in tile aviation and engine-building industries. Non-ferrous metals and their alloys are seldom forged by the hammer forging process.

Non-ferrous metals and their alloys are forged in machines of the same types as those used for forging ferrous metals, and with similar tools. The forging and stamping of non-ferrous metals and their alloys are based on the same principles as those used for ferrous metals. However, mention must be made of certain specific features which must be taken into consideration when forging and stamping non-ferrous metals and their alloys.

Non-ferrous metals and their alloys intended for forging can be classified into two groups: heavy and light metals and alloys. The first group includes copper, bronze, nickel, nichrome and brass. The second group covers light metals and alloys – aluminium, duralumin, and magnesium alloys. The chief conditions for forging some of these alloys are as follows.

Copper is used mainly in the electrical industry for manufacturing parts of electrical apparatus, busbars, wires, etc. Copper is not very ductile at temperatures from 230 to 600 C, and cannot be forged or stamped at temperatures above 800°C, due to its high brittleness. Pure copper is very seldom forged or stamped, and usually only its alloys - bronze and brass - are subjected to forging and pressing.

Brass is an alloy of copper and zinc. So-called malleable brass, consisting of 59 per cent copper, 45 per cent zinc and from 1 to 0.5 per cent lead, is most frequently subjected to forging and stamping. Sometimes brass containing no lead is used for stampings. Brass is stamped on the same kind of equipment and, by the same methods as those employed for stamping steel. Brass can be heated in ordinary forge furnaces which ensure a uniform temperature.

When stamping brass, its following characteristics should be born in mind. In the first place, the forging temperature range of brass is very narrow - from 730 to 750°C, and its optimal forging temperature interval ranges from 730 to 720°C. Therefore brass must be stamped very rapidly, preferably at one blow. Secondly, trimming must be effected at the forging temperature interval, i.e., between 730 and 720°Ci Softer the forging has cooled to room temperature.

Bronze is an alloy of copper and aluminium, tin and other elements; Aluminium bronze is very easily forged and stamped in presses and hammers. Its forging temperature interval ranges from 900 to 750°C. Bronze can be heated in the furnaces employed for heating steels.

Aluminium and duralumin are metals silver in colour, highly plastic and easily stamped.

Duralumin is an alloy of aluminium and copper (up to 4.5 per cent), manganese and magnesium (about 0.5 per cent). Forging temperature intervals for aluminium: 475-425°0 and for duralumin470-380°C.

Aluminium alloys are particularly widely employed in the aviation industry, because of their light weight and high strength. Aluminium and its alloys are usually heated in electric furnaces, the rate of heating being far slower than that of steel.

When forging and stamping aluminium and its alloys, which can be carried out on both hammers and presses, the following features must be born in mind.

1. All the forging tools (stamps, dies, etc.) must be heated to 200-250°C before commencing operations.

2. Experience shows that rectangular ingots and stock can be forged more easily than round ones, which frequently display cracks on forging. For this reason, round ingots and stock should not be used.

3. Aluminium alloys have a tendency to stick to the surface of the dies, thereby resulting in forgings with rough surfaces. For this reason the surfaces of the dies and their impressions must be very carefully polished. During stamping and forging these surfaces must be lubricated, and the dies heated to 200-250°C before starting work. They may be lubricated with a mixture of graphite and vegetable oil or masout.

4. Mixtures of aluminium powder and iron scale are highly produced in the same forge shop. Precautions should therefore be taken in order to exclude all possibility of mixing aluminium dust and iron scale and, thus, the possibility of explosions.

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