Casting of copper
Copper is cast in the form of various groups of alloys, each having copper as the main element. Short descriptions of some of these are given below:
- High conductivity coppers: These are used mainly for their high electrical and thermal conductivities. Applications include tuyères for blast furnaces and hot blast cupolas, watercooled electrode clamps, switchgear, etc.
- Brasses: Cu-Zn-alloys, where zinc is the major alloying element. These are easy to cast, with excellent machinability and good resistance to corrosion in air and fresh water. They are widely used for plumbing fittings. High tensile brasses are more highly alloyed and find uses in marine engineering. Brasses are cast both in sand and in permanent moulds
- Tin bronzes: Cu-Sn-alloys, where tin is the major alloying element. With tin contents of 10 – 12 %, tin bronze castings are more expensive than brass. They have high corrosion resistance and are suitable for handling acidic waters, boiler feed-waters, etc. High tin alloys are also used in wear-resistant applications. Their applied casting techniques are sand and centrifugal casting
- Phosphor bronzes: Cu-Sn-alloys, with an addition of about 0.4 – 1.0 % P. These are harder than tin bronzes but have lower ductility. They are used for bearings where loads and running speeds are high and for gears such as worm wheels
- Lead bronzes: Cu-Sn-Pb-alloys. These are used almost exclusively for bearings, where loads and speeds are moderate
- Gunmetals: Cu-Sn-Zn-Pb-alloys. These are the optimal alloys for sand casting. They have a good combination of castability, machinability and strength, and good corrosion resistance. They are used for intricate, pressure-tight castings, such as valves and pumps. They are also used for bearings, where loads and speeds are moderate
- Aluminium bronzes: Cu-Al-alloys, where Al is the major alloying element. These combine a high strength with high resistance to corrosion. Their applications range from decorative architectural features to highly stressed engineering components. They have many marine uses, including propellers, pumps, valves. They are also used for the manufacture of nonsparking tools. Al casting techniques are applied
- Copper-Nickels: Cu-Ni-alloys, where Ni is the major alloying element. These are used for e.g. pipework for marine applications in severe conditions
- Copper-beryllium alloys: Beryllium is cast as a copper-beryllium alloy for the production of parts that require resistance to corrosion and very high mechanical characteristics. These include plunger tips for die-casting machines, precision parts for the electrical and mechanics industry, in watchmaking, for tooling, and for measurements instruments. Two alloy types are used: a copper-beryllium alloy with 2 % Be, and a copper-cobalt-beryllium alloy with 0.5 % Be. There is a tendency to reduce or exclude beryllium in alloys due to its known carcinogenic character. Casting is done in permanent moulds using pressure or gravity die-casting. For precision parts casting, the investment casting technique is used.
[175, Brown, 1999]
Source: European Commission, Reference Document on Best Available Techniques in the Smitheries and Foundries Industry, May 2005, p.20-21