Anti-Veining Additive for Silica Sand Mold

Abstract

This invention relates generally to a composition for silica sand cores and molds suitable for in the casting of metals. The sand core composition contains a hinder and a uniformly dispersed anti-veining additive. The mixed metal oxides collapse into a visco-plastic state when the foundry mold/core is heated by the molten metal during casting. A change in state of the MMOx from solid to a visco-plastic at the casting high temperatures provides space and lubricity within the foundry shape sufficient to compensate for the thermally-induced physical expansion of the silica grains. Thereby avoiding the mechanical forces which cause cracks and fissures in the mold or core that produce veins and other surface imperfections associated with the high coefficient of thermal expansion of silica sand.

The invention claimed is: 
     
         1 . A bonded silica sand mold for use in manufacturing metal castings, the metal castings produced with said bonded silica sand mold are substantially free of surface veins, said mold comprising:
 an additive of mixed metal oxides.   
     
     
         2 . A bonded silica sand mold as claimed in  claim 1 , wherein said additive mixed metal oxides comprise less than 6.0% by weight of said bonded silica sand mold. 
     
     
         3 . A bonded silica sand mold as claimed in  claim 1 , wherein said additive of mixed metal oxides comprises at least five metals selected from the group consisting of Na, Al, Si, Ca, Mg, K, Fe. 
     
     
         4 . A bonded silica sand mold as claimed in  claim 1 , wherein said additive of mixed metal oxides comprises of at least 40% by weight of Silicon. 
     
     
         5 . A bonded silica sand mold as claimed in  claim 3 , wherein said additive of mixed metal oxides comprises of at least 40% by weight of Silicon. 
     
     
         6 . A bonded silica sand mold as claimed in  claim 1 , wherein said additive of mixed metal oxides combined have a softening temperature of above at least 1,000° F. (540° C.). 
     
     
         8 . A bonded silica sand mold as claimed in  claim 1 , wherein said mold further comprising:
 an organic binder.   
     
     
         9 . A bonded silica sand mold as claimed in  claim 1 , wherein said additive of mixed metal oxides comprises at least four metals selected from the group consisting of Na, Al, Si, Ca, Mg, K, Fe. 
     
     
         10 . A bonded silica sand mold as claimed in  claim 1 , wherein said additive of mixed metal oxides comprises between 1%-6% by weight of the bonded silica sand mold. 
     
     
         11 . A bonded silica sand mold for use to manufacture metal castings as claimed in  claim 9 , wherein said mold further comprising:
 an organic binder.   
     
     
         12 . A bonded silica sand mold for use in manufacturing metal castings, the metal castings produced with said bonded silica sand mold are substantially free of surface veins, said mold comprising:
 an additive of mixed metal oxides, mixed metal oxides comprising of at least two metals selected from the group consisting of Na, Al, Si, Ca, Mg, K, Fe;   wherein said additive of mixed metal oxides comprises between 1%-6% by weight of the bonded silica sand mold.   
     
     
         13 . A bonded silica sand mold as claimed in  claim 12 , wherein said Ca is at least 9% by weight of the mixed metal oxides. 
     
     
         14 . A bonded silica sand mold as claimed in  claim 12 , wherein said additive of mixed metal oxides combined have a softening temperature of above at least 1,045° F. 
     
     
         15 . A bonded silica sand mold as claimed in  claim 12 , wherein said mold is a phenolic urethane cold box mold. 
     
     
         16 . An anti-veining mixed metal oxides additive, said mixed metal oxides comprising of at least four metals selected from the group consisting of Na, Al, Si, Ca, Mg, K, Fe. 
     
     
         17 . An anti-veining mixed metal oxides additive as claimed in  claim 16 , wherein said additive of mixed metal oxides in combination have a softening temperature of above at least 1,045° F. 
     
     
         18 . An anti-veining mixed metal oxides additive as claimed in  claim 17 , wherein said mixed metal oxides comprises of at least four metals selected from the group consisting of Na, Al, Si, Ca, Mg, K, Fe. 
     
     
         19 . An anti-veining mixed metal oxides additive as claimed in  claim 16 , wherein
 said Na is at least 9% by weight of said mixed metal oxides, and   
       said Si is at least 40% by weight of said mixed metal oxides.