Two piece mold used in manufacture of PDC drill bits and method of using same

Abstract

A graphite core mold having its own cavity is pressed into a cavity of a graphite shell mold. The core cavity is filled with tungsten carbide, mixed with a nickel alloy, heated and then cooled to thereby provide a carbide matrix body. After milling the carbide matrix body to thereby provide a carbide bit body, the intact shell mold is removed and then used again.

1 . A mold for forming a carbide matrix PDC bit body, comprising:
 a cylindrical shell having a closed end, an open end and a cavity commencing with the open end of said shell;   a cylindrical core having a closed end, an open end, and a cavity commencing with the open end of said core, said core having an outside diameter sized to closely fit within the inside diameter of the cavity within said shell, wherein the cavity within the core can be filled with a mixture of tungsten carbide powder and particles of a metallic alloy, which when heated and then cooled and then milled, form a carbide matrix PDC bit body.   
     
     
         2 . The mold according to  claim 1 , wherein said core comprises graphite. 
     
     
         3 . The mold according to  claim 2 , where said shell comprises graphite. 
     
     
         4 . The mold according to  claim 1 , wherein the closed end of said core and the closed end of said shell are pressed against each other. 
     
     
         5 . The mold according to  claim 1 , wherein said metallic alloy comprises nickel. 
     
     
         6 . A method for molding a carbide matrix body for a PDC drill bit, comprising the steps of:
 pressing a graphite core into a graphite shell;   pouring tungsten carbide powder and particles of a metallic alloy into a cavity in said core;   melting the mixture of the powder and the particles within the cavity in the core;   cooling the molten mixture to thereby provide a carbide matrix body;   removing the intact shell from around the core;   milling the carbide matrix body with the desired features of a PDC drill bit; and   removing the core from the carbide matrix body.   
     
     
         7 . The method according to  claim 6 , including the repetition of the steps according to  claim 6 , using the same graphite shell in the repeated process. 
     
     
         8 . The method according to  claim 6 , wherein the metallic alloy comprises nickel.