| 摘要 |
PURPOSE:To prevent the development of fault, such as breakage of the core or penetration of molten metal into the sand core at the time of die casting and to improve the collapsibility of the sand core after casting by executing the specific coating treatment on the sand core surface molded by using organic binder. CONSTITUTION:At first the sand core surface molded by using the organic binder, is applied slurry adding one kind or more of refractory of fine powdery silica flower, zircon flower or alumina flower, etc., to binder of colloidal silica, ethyl silicate or water glass, etc., to fill up interstice among the grains of the sand core surface. Further, the surface of this sand core is applied slurry adding the fine powder having lubricity, such as mica or vermiculite to water soluble organic binder containing phenol resin, methylcellulose or polyethylene oxide, etc. In this way, the penetration of molten metal into the surface grain for the sand core and the collapsibility of the sand core is improved.
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