| 摘要 |
PURPOSE:To decrease casting defects such as gas holes and shrinkage cavities by using a resol type phenolic resin contg. a melamine compd. as a binder for titled sand grains to be used for a shell mold for casting. CONSTITUTION:A solid resol type phenolic resin contg. a melamine compd. or urea melamine compd. is used for the binder of binder-coated sand grains constituted of molding sand and the binder coated on the surface thereof. Since the chemical bonds incorporated much in the binder are decomposed, a large endothermic reaction arises in the shell mold obtd. by using such sand grains, by which the cooling of a molten metal is accelerated. Casting defects such as blowholes, pinholes, shrinkage cavities and the like are effectively decreased. The sand grains are particularly suitable for a copper alloy casting. |
