GB769485A - Zinc-aluminium alloys and a process for producing the same - Google Patents

Abstract

Zinc-aluminium alloys, suitable for use as bearing material and cages for ball or roller bearings, have compositions within the following range .Zn.at least 20.per cent .Al.30 - 60.per cent .B and C.0.001-15.per cent The B and/or C may be partially replaced by Si at least 0.001 per cent of B or C or B and C being present. The alloy may include 0.05-6.0 per cent of Cu. One or more of the following elements may also be present up to 6 per cent in total, Mg, Ni, Cr, Ti, Ca, Sr, Ba, Cd, Mn, Sn, V, Mo, Sb, W, Ce, P, Na, and K, Pb being present, if at all only as an unavoidable impurity and Fe not exceding 0.5 per cent. In forming the alloy one or more of the optional elements may be added as hydrides and monazite may be added to the melt. The resulting alloy is cast at a temperature of 550-680 DEG C. Preferably the melt is cooled in stages, first locally then as to the rest e.g. by using a cooled core, by casting in a sand mould and partially removing the mould after solidification and rapidly cooling the exposed region or regions or by casting in a sand mould with chill sections. The casting may be subjected to reheating at 180-400 DEG C., e.g. for 6-12 hours, then tempered and quenched in cold sand impregnated with oil. Alternatively the incompletely cooled castings may be heated to 300-400 DEG C. and placed succesively in sand baths of differing temperatures e.g. 200 DEG C., 100 DEG C., and 10-20 DEG C., for several hours in each. Specification 769,484 also is referred to.