GB606948A - Improvements in or relating to magnesium and magnesium base alloy castings - Google Patents

Abstract

The grain size of magnesium castings or castings of magnesium base alloys containing at least 70 per cent of magnesium, is refined, and the non-metallic impurity content thereof is reduced, by melting the metal or alloy, introducing at least one halogenated hydrocarbon or a carbon tetrahalide into the melt and thereafter casting the metal alloy. The preferred halogen is chlorine, e.g. a chlorinated aromatic hydrocarbon may be used, and preferably a fully chlorinated hydrocarbon, e.g. hexachlorobenzene. Alloys which may be treated include those containing about 3-12 per cent of aluminium with or without zinc, silicon, manganese, tin or lead in smaller proportions than the aluminium. The alloy may be treated at 1300-1550 DEG F. and it may be treated with a refining salt flux prior to the introduction of the halogenated hydrocarbon. Best results are obtained by using a halogenated hydrocarbon in amount between 0.01 and 0.3 per cent of the weight of the metal being treated.