Zircon sand--a viable alternative moulding system for titanium castings

Abstract

The experimental observations of casting Ti in sodium silicate bonded zircon sand mould are presented. Metal--mould reactions, in general, involved dissolution of oxides in liquid Ti resulting in contamination of the casting. Minimal metal--mould reactions occurred when Ti was cast in zircon sand mould containing approx 7.5 wt.% of ZrO₂. It has been further shown that the metal--mould reaction is considerably reduced if moulds were fired at high temperatures ( > 1273K). This ensured elimination of moisture from the mould and also resulted in some beneficial changes in the mould chemistry. The reduction in metal--mould reaction is reflected in the decrease in oxygen and hydrogen contamination and decrease in hardness. Thus microhardness profile and O analysis seems to provide a good index for evaluation of severity of metal--mould reaction. The method has been demonstrated to be satisfactory for casting Ti components.