Abstract
The present study investingated a spinel investment composed of MgO, Al2O3 and ZrO2 for titanium castings.The spinel investment with added fluorides, such as MgF2, CaF2, had a high compressive strength and the spinel content was increased after firing.For instance, using a spinel investment containing 3% MgF2 and 3% CaF2, the remaining expansion was 1.2-2.5% after firing at 1, 200℃ for 60min.The compressive strength was 0.9-2kgf/mm2.The remaining expansion depended on the composition of the spinel investment, firing temperature and firing time. Finally, a spinel investment with a remaining expansion equivalent to the casting shrinkage of titanium was prepared.A hard layer in which both aluminum and oxygen were dissolved in titanium, was formed at the surface of the titanium casting.However, high quality titanium castings could be cast with the spinel investment.
