Mold core for investment casting, process for preparing the same and process for preparing mold for investment casting having therewithin said mold core

A process for preparing an investment casting mold in which molten metal is thereafter cast;

• said process comprising the steps of:
• (a) kneading an aggregate with a first inorganic binder for increasing the strength and integrity of said aggregate for withstanding an injection molding operation for molding a lost model;
• (b) molding the kneaded aggregate and first inorganic binder into a core molding mold to be solidified therein to produce a core matrix;
• (c) dipping the solidified core matrix in a second inorganic binder bath so that the core matrix is impregnated with the second inorganic binder penetrating from the surface into a marginal portion of the body thereof, said second inorganic binder layer increasing the strength of said core matrix at a high temperature environment which is reached during a mold baking step and thereafter during a molten metal casting step;
• (d) coating the core matrix impregnated by said step (c) with a slurry followed by drying to form a coating layer;
• (e) covering said coating layer with paraffin wax to produce a core mold;
• (f) placing said core mold in position within a shell mold and then pouring a lost model forming material into said shell mold to produce a lost model having therewithin said core mold;
• (g) alternately coating a slurry and layer of stucco particles for a plurality of times to form a refractory layer which is then dried;
• (h) allowing said lost model to vanish so as to obtain a final mold;
• and
• (i) baking said core mold and said refractory layer simultaneously.