Method of improving the removal of investment casting shells

Abstract

The removal of an investment casting shell surrounding a metallic part is improved by adding a salt of alkali or alkaline earth metal to at least one of the layers of the shell.

1 - 3 . (canceled)  
   
   
       4 . A method of forming an investment casting shell in a shell preparation sequence and improving the removal of the investment casting shell surrounding a metallic part, wherein the shell preparation sequence comprises deposition of alternating layers of a refractory slurry and a dry refractory stucco onto a pattern, wherein an effective amount of the salt of an alkali or alkaline earth metal is added to at least one layer of the dry refractory stucco during the shell preparation sequence, and wherein the refractory slurry layers are free of added alkali or alkaline earth metal salt during the shell preparation sequence.  
   
   
       5 - 11 . (canceled)  
   
   
       12  The method of  claim 4 , wherein the salt of the alkali or alkaline earth metal is selected from the group consisting of: calcium carbonate, calcium sulfate, calcium magnesium carbonate, magnesium carbonate, magnesium sulfate, strontium carbonate, and mixtures thereof.  
   
   
       13 . The method of  claim 4 , including about 1 percent to about 30 percent of the salt of the alkali or alkaline earth metal, based on weight of the shell.