| 摘要 |
PURPOSE:To prevent erosion on the surfaces of water soluble patterns and to reduce a drying time by adding water content less than theoretical value to a hydrolyzing binder to prepare a slurry, and coating the slurry on casting molds then causing hydrolysis reaction by the moisture in the atmospheric air. CONSTITUTION:An ethyl silicate binder is hydrolyzed by the water content which is set less than theoretical value and molding sand of refractory fine granular aggregate is put therein, whereby a refractory slurry contg. undecomposed ethyl silicate binder is prepd. Such binder is coated and stuck over the entire part of an expendable material pattern which is beforehand made to the preset pattern of a prototype. Refractory molding sand is coated thereon before the coating material dries up. The coating is subjected to atmospheric drying to allow the moisture in the atmospheric air to be absorbed therein so that the undecomposed ethyl silicate binder is hydrolyzed and begins to gel. Thus, the erosion of the surface of the water soluble pattern by excess moisture is prevented and the drying is accelerated. |
