| 摘要 |
PURPOSE:To considerably prolong the time when a frozen mold can be left standing by penetrating a binder from the mold molding surface thereby forming a hardened shell layer. CONSTITUTION:After molding or after freezing, a binder is coated on at least the molding surface 2 of a mold 1, by spraying, brushing or immersing therein to allow this to penetrate among the sand grains of the mold 1 from the surface, whereby a hardended shell layer 3 is formed. The binder is ordinary water glass, and is rapidly hardened by bringing the water glass into to contact with a gasous CO2. When the mold formed with the hardened layer 3 in this way is left standing in the atmosphere after freezing, the hardened layer 3 plays the role of a heat insulating layer covering the mold 1 and performs the action of retarding the temp. rise of the entire part of the mold 1 from the surface, thereby maintaining the surface stability of the molding surface 2. |
