Cast Copper Alloy Information

The coppernickels are metallurgically simple alloys, consisting of a continuous series of solid solutions throughout the copper-nickel system. Copper-rich alloys in the copper-nickel system are known as coppernickels; nickel-rich compositions in this system are called Monel alloys. The copper-nickels solidify over narrow freezi ng ranges, although the range extends somewhat with increasing nickel content. Segregation is not a serious problem.[Cu-Ni-Fe]

Iron, niobium (columbium) and sil icon can produce precipitation hardening in copper-nickels through the formation of silicides; however, precipitat ion takes place readily as the casting cools, and the alloys are consequently not age-hardenable. On the other hand. beryllium-containing C96600 can be age-hardened in the same manner as can ordinary berylliumcopper alloys.

Known commonly as Nickel Silvers, these are alloys which contain zinc and nickel as the principal and secondary alloying elements, with or without other designated elements. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver does not contain the element silver.

These copper-nickel-tin-lead-zinc alloys offer excellent corrosion resistance, high castability and very good machinability. They have moderate strength. Among their useful attributes is their pleasing silvery luster. Valves, fittings and hardware cast in nickel silvers are used in food and beverage handling equipment and as seals and labyrinth rings in steam turbines.

Despite their complex composition, nickel silvers display simple alpha microstructures. Nickel, tin and zinc impart solid solution hardening, and mechanical properties generally improve in proportion to the concentration of these elements. The nickel silvers are not heat treatable. The alloys' characteristic silver color is produced primarily by nickel. aided to some extent by zinc.

The leaded coppers offer the high corrosion resistance of copper and high copper alloys, along with the favorable lubricity and low friction characteristics of high leaded bronzes.[Cu-Pb]

The lead in these alloys is dispersed as discrete globules surrounded by a matrix of pure copper or high-copper alloy. The conductivity of the matrix remains high, being reduced only by whatever other alloying elements may be present. Lead contents range from about 25% in alloy C98200 to as high as 58% in alloy C98840. Between 1 % and 5% tin is added to alloys C98820 and C98840 for added strength and hardness. Similarly, alloys C98400 and C98600 contain up to 1.5% silver, while C98800 may contain up to 5.5% silver, balanced against the lead content to adjust the alloy's hardness.

These alloys undergo a two-step solidification process. That is, the copper fraction (pure copper or high-copper alloy) freezes over the narrow solidification range typical of such alloys. The lead solidifies only after the casting has cooled some 700 degrees Celsius (1,300 Fahrenheit). Segregation of lead from the last regions to solidify is serious challenge to overcome and can pose a problem. Chill-casting and/or using thin sections help trap the lead in a uniform dispersion throughout the structure.