The Possibility of Fabricating Co-Cr Casting Plates by Using a Heat-Shock Method with Conventional Phosphate-Bonded Investments

The possibility of fabricating Co-Cr casting plates by using a heat-shock method with conventional phosphate-bonded investments was investigated. Commercial phosphatebonded investments (Snow white, Univest nonprecious: Shofu) were investigated. A block of a duplicated model was prepared by usingeach powder mixed with its specific colloidal silica solution. A sheet of wax pattern with 0.5 mm thick on the model was secondarily invested by slurry mixed with water, colloidal silica solution, and their mixture. After 30 min on investing, the mold was put into the furnace preheated at 800°C and kept there for 30 min. Only the mold prepared from Univest mixed with waterwas available for casting after the heat-shock treatment. Other molds exploded in the furnace orreceived cracks after the treatment.The Co-Cr castings obtained from the available molds werenot obviously sound because of insufficient firing. These results suggested that we might fabricate Co-Cr casting plates by using a heat-shock method with conventional phosphate-bonded investments, but we need further investigations to find suitable conditions for this method.