Impregnated ceramic core and method of making

Abstract

An impregnated fired, porous ceramic core for use in an investment casting shell mold in the casting of molten metals and alloys is strengthened by impregnating the core with an aqueous emulsion of water-insoluble polymer followed by drying to remove the water.

I claim:  
     
         1 . A method of strengthening a fired, porous ceramic core for use in investment casting, comprising: 
 impregnating the core with an aqueous emulsion of a water-insoluble polymer, and    drying the impregnated core to remove water.    
     
     
         2 . The method of  claim 1  wherein the water-insoluble polymer is selected from the group consisting of acrylic, styrene butadiene, polyvinyl acetate, styrene acrylic, vinyl acetate acrylic, vinyl-vinylidene chloride, epoxy, polyvinyl butyrol, and polyurethane.  
     
     
         3 . The method of  claim 1  wherein the aqueous emulsion comprises about 10% to about 60% of said water-insoluble polymer and balance essentially water.  
     
     
         4 . The method of  claim 1  wherein the aqueous emulsion comprises about 10% to 50% by weight of an acrylic polymer and balance essentially water.  
     
     
         5 . The method of  claim 4  wherein the acrylic polymer has a glass transition temperature from 15 to 40 degrees C.  
     
     
         6 . The method of  claim 4  wherein the aqueous emulsion comprises about 15% to 30% by weight of an acrylic polymer and balance essentially water.  
     
     
         7 . The method of  claim 4  wherein the acrylic polymer is self cross-linkable.  
     
     
         8 . The method of  claim 4  wherein the aqueous emulsion includes a cross linker for the water-insoluble polymer.  
     
     
         9 . The method of  claim 1  wherein the impregnating of the fired, porous core is achieved by immersing the core in the aqueous emulsion.  
     
     
         10 . The method of  claim 1  wherein the drying of the impregnated core is achieved by convection at superambient temperature.  
     
     
         11 . A method of strengthening a fired, porous ceramic core for use in investment casting, comprising impregnating the core with an aqueous emulsion of a water-insoluble acrylic polymer and drying the impregnated core to remove water.  
     
     
         12 . A fired, porous ceramic core for use in investment casting including water-insoluble polymer in pores of said core.  
     
     
         13 . The core of  claim 12  wherein the water-insoluble polymer is selected from the group of consisting of acrylic, styrene butadiene, polyvinyl acetate, styrene acrylic, vinyl acetate acrylic, vinyl-vinylidene chloride, epoxy, polyvinyl butyrol, and polyurethane.  
     
     
         14 . The core of  claim 13  wherein the core includes cross-linked acrylic polymer.  
     
     
         15 . The core of  claim 12  wherein the core includes about 0.2% to about 5% by weight polymer solids.