Countergravity Casting Apparatus and Desulfurization Methods

Abstract

An apparatus for countergravity casting a metallic material, comprises: a crucible for holding melted metallic material; a casting chamber for containing a mold; a fill tube capable of extending into the crucible to communicate melted metallic material to the casting chamber; a gas source coupled a headspace of the melting vessel to allow the gas source to pressurize said headspace to establish a pressure differential to force the melted metallic material upwardly through said fill tube into said mold; and means for gettering sulfur.

1 - 13 . (canceled) 
     
     
         14 . A method for countergravity casting a nickel-based superalloy, the method comprising:
 melting the nickel-based superalloy;   disposing a mold under subambient pressure on a mold base with a fill tube of said mold extending through an opening in said base;   relatively moving said melting vessel and said base to immerse an opening of said fill tube in the melted nickel-based superalloy in said melting vessel and to engage said melting vessel and said base with seal means therebetween such that a sealed gas pressurizable space is formed between the melted nickel-based superalloy and said base; and   gas pressurizing said space to establish a pressure differential on the melted nickel-based superalloy to force it upwardly through said fill tube into said mold, the melted nickel-based superalloy passing through a filter which at least one of:
 reduces sulfur content of the passed melted nickel-based superalloy; and 
 filters sulfur-containing particles. 
   
     
     
         15 . The method of  claim 14  further comprising:
 introducing sulfur-gettering particles to the melted nickel-base superalloy upstream of the filter, the sulfur-gettering particles then gettering sulfur to become the sulfur-containing particles. 
 
     
     
         16 . The method of  claim 14  wherein the filter comprises a sulfur-gettering material. 
     
     
         17 . The method of  claim 14  further comprising:
 solidifying the melted nickel-base superalloy to block the fill tube. 
 
     
     
         18 .- 24 . (canceled)