PURPOSE: To obtain a sand core which withstands high-pressure casting and has a good collapsing property by molding a sand core prototype by a shell molding method using RCS and treating this prototype with an org. acid salt, then drying the prototype, applying a coating material thereon and drying the coating.
CONSTITUTION: The resin coated sand(RCS) formed by coating silica sand, etc., with a coal acid resin is prepd. and the sand core prototype is produced by the shell molding method of blowing this sand into heated molds. This prototype is immersed into an aq. org. acid soln. of calcium acetate, etc., and is then dried for about 30 minutes at 120°C. The surface thereof is then coated with the slurry-like coating material consisting of a neutral aq. dispersion essentially consisting of powdery refractories and is dried. As a result, the coating material is instantaneously flocculated by the org. acid salt existing on the surface and near the surface of the sand core prototype and the surface of the sand core prototype is thickly coated with this material without spilling on the surface.
KUNIMURA MASARU
IITANI HIDEYUKI
KOYA MORIE
