| 摘要 |
PURPOSE:To produce a collapsible core which prohibits penetration of a molten metal by forming a coating layer for smoothing on the surface of a shell core, coating an alcohol soln. of a phenolic resin thereon and further forming a coating layer cured by heating thereon. CONSTITUTION:The shell core 1a is obtd. by molding resin-coated sand. After the core is immersed into 1st slurry consisting of fine powder refractories, alcohol and the phenolic resin, the core is cured by heating to form the 2nd coating layer on the surface. The alcohol soln. of the phenolic resin is coated on said layer by impregnation, etc., and is dried to the extent of not curing to evaporate the alcohol component, by which the 2nd coating layer 3 is formed. The 3rd coating layer 4 is further formed thereon by immersing the core into 2nd slurry and curing the coating by heating. The 2nd slurry which consists of water and natural or synthetic mica or is incorporated with flake graphite and metal powder such as stainless steel powder is adequate. The collapsible core 1 which has the coating layer having resistant to flow by a molten metal and yields the product having a smooth casting surface is thereby obtd.
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