Casting device and associated method for lost foam casting with improved mechanical properties

Abstract

The invention describes a method of casting a metal comprising the following steps: fabricating a pattern from polystyrene foam, coating the pattern with a ceramic slurry, filling sand around the pattern to create a sand mold, placing the sand mold in an open pressure vessel, filling the sand mold with a molten metal, immediately thereafter closing and pressure sealing the pressure vessel, pressurizing the sealed pressure vessel with an inert gas for a predetermined measured time, depressurizing the sealed pressure vessel, opening the pressure vessel and removing the metal filled sand mold, and extracting the desired object from the mold.

I claim: 
     
         1 . A method of casting a metal alloy comprising the following steps:
 fabricating a pattern from polystyrene foam having the appropriate geometry to generate a desired object to be cast;   coating the pattern with a ceramic slurry;   filling sand around the pattern to create a sand mold;   placing the sand mold in an open pressure vessel;   filling the sand mold with a molten metal alloy, thereby vaporizing the foam pattern;   immediately thereafter closing and pressure sealing the pressure vessel;   pressurizing the sealed pressure vessel with an inert gas for a predetermined measured time;   depressurizing the sealed pressure vessel;   said predetermined measured time sufficient for the molten metal to cool and solidify;   opening the pressure vessel and removing the metal filled sand mold; and   extracting the desired object from the sand mold.   
     
     
         2 . The method of  claim 1  wherein the sand based mold may be comprised of silica sand (SiO 2 ), chromite sand (FeCr 2 O), zircon sand (ZrSiO 4 ), and combinations thereof. 
     
     
         3 . The method of  claim 1  wherein the inert gas may be helium, argon, nitrogen, oxygen, or combinations thereof. 
     
     
         4 . The device of  claim 1  wherein the sealed pressure vessel is pressurized to a value in the range of 50 to 180 pounds per square inch with the inert gas. 
     
     
         5 . A method of casting a metal alloy comprising the following steps:
 fabricating a pattern from polystyrene foam having the appropriate geometry to generate a desired object to be cast;   coating the pattern with a ceramic slurry;   filling sand around the pattern to create a sand mold;   placing the sand mold in an open pressure vessel;   filling the sand mold with a molten metal alloy, thereby vaporizing the foam pattern;   immediately thereafter closing and pressure sealing the pressure vessel;   pressurizing the sealed pressure vessel with an inert gas for a predetermined measured time;   said predetermined measured time sufficient for the molten metal to cool and solidify;   withdrawing the inert gas from the sealed pressure vessel and transferring said inert gas into a reusable storage device thereby depressurizing the sealed pressure vessel;   opening the pressure vessel and removing the metal filled sand mold; and   extracting the desired object from the sand mold.   
     
     
         6 . The method of  claim 5  wherein withdrawing the inert gas from the sealed pressure vessel may include filtering and separating unwanted gaseous compounds prior to transferring the said inert gas into a reusable storage device. 
     
     
         7 . A device for casting a metal alloy comprising the following elements:
 a pressure vessel head;   a pressure vessel base incorporating a surface to support an investment mold;   a vertical travel guide in mechanical communication with the pressure vessel head and the pressure vessel base;   said pressure vessel head and pressure vessel base incorporating interlocking members capable of forming a pressure seal when interlocked; and   an actuator capable of engaging the interlocking members thereby forming a pressure seal when the pressure vessel head is in mechanical communication with the pressure vessel base.   
     
     
         8 . The device of  claim 7  wherein the pressure vessel base incorporates a bidirectional valve device with the means to receive an inert gas from an external source and exhaust said inert gas into an external source for later reuse.