Face coat composition for casting mold and method for the preparation of casting mold having face coat layer

摘要

Proposed is a novel face coat composition having improved stability used in the preparation of a shell-like casting mold for a high melting point metal or alloy by the lost-wax mold method by forming a face coat layer on a wax model using the composition and further forming a backup coat layer thereon followed by removal of the wax by melting and calcination of the shell-like mold formed from the layers. The face coat composition comprises a rare earth oxide powder as the refractory constituent and a binder which is a synthetic resin in the form of an aqueous emulsion, a water-soluble organic polymer in the form of an aqueous solution, a sol of an inorganic oxide such as aluminum oxide, silicon dioxide and zirconium oxide or a combination thereof. A small amount of a powder of rare earth glass can be admixed to the composition so that the face coat layer formed from the face coat composition may have still improved properties. The face coat layer formed from the inventive face coat composition is outstandingly resistant against attack of the high-temperature melt of a reactive metal or alloy so as not to form a reaction-hardened surface layer on the cast body.