Sand casting device and associated method with improved mechanical properties

Abstract

The present invention describes a method of casting a metal alloy comprising forming a sand based mold having the geometry to generate a desired object to be cast, placing the mold in an open pressure vessel, filling the mold with a molten metal alloy, immediately thereafter closing and pressure sealing the pressure vessel, pressurizing the sealed pressure vessel with an inert gas for a measured time said predetermined measured time sufficient for the molten metal to cool and fully solidify, depressurizing the sealed 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:
 forming a sand based mold having the appropriate geometry to generate a desired object to be cast;   placing the sand based mold in an open pressure vessel;   filling the sand based mold with a molten metal alloy;   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;   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.   
     
     
         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 ), olivine, staurolite, graphite, bentonite (clay), anthracite, water, organic and inorganic binders, 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:
 forming a sand based mold having the appropriate geometry to generate a desired object to be cast;   placing the sand based mold in an open pressure vessel;   filling the sand based mold with a molten metal alloy;   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 method of casting a metal alloy comprising the following steps:
 forming a sand based mold having the appropriate geometry to generate a desired object to be cast;   filling the sand based mold with a molten metal alloy   placing the sand based mold in an open pressure vessel;   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.   
     
     
         8 . The method of  claim 7  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. 
     
     
         9 . A method to reduce porosity defects in sand casted metal objects comprising:
 forming a sand based mold having the appropriate geometry to generate a desired object to be cast;   placing the sand based mold in an open pressure vessel;   filling the sand based mold with a molten metal alloy;   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;   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.   
     
     
         10 . A method to reduce porosity defects from mold-metal interface reactions comprising:
 forming a sand based mold having the appropriate geometry to generate a desired object to be cast;   placing the sand based mold in an open pressure vessel;   filling the sand based mold with a molten metal alloy;   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;   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.   
     
     
         11 . A method to improve the tensile strength, yield strength, and percent elongation of a sand casting comprising the following steps:
 forming a sand based mold having the appropriate geometry to generate a desired object to be cast;   placing the sand based mold in an open pressure vessel;   filling the sand based mold with a molten metal alloy;   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;   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.   
     
     
         12 . A method to reduce hazardous air pollutants in a sand casting process comprising:
 forming a sand based mold having the appropriate geometry to generate a desired object to be cast;   placing the sand based mold in an open pressure vessel;   filling the sand based mold with a molten metal alloy;   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;   depressurizing the sealed pressure vessel;   reclaiming and purifying the inert gas during the said depressurizing;   releasing non hazardous by-products separated from the inert gas back into the atmosphere;   containing hazardous by-products separated from the inert gas;   opening the pressure vessel and removing the metal filled sand mold; and   extracting the desired object from the sand mold.   
     
     
         13 . A device for casting a metal alloy comprising the following elements:
 a pressure vessel head;   a pressure vessel base incorporating a surface to support a sand casting 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.   
     
     
         14 . The device of  claim 13  wherein the pressure vessel base incorporates a unidirectional valve device to receive an inert gas from an external source. 
     
     
         15 . The device of  claim 13  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. 
     
     
         16 . A method of casting a metal alloy comprising the following steps:
 forming a sand based mold having the appropriate geometry to generate a desired object to be cast;   placing the sand based mold in an open pressure vessel;   filling the sand based mold with a molten metal alloy;   immediately thereafter closing and pressure sealing the pressure vessel;   pressurizing the sealed pressure vessel with helium for a predetermined measured time;   said predetermined measured time sufficient for the molten metal to cool and solidify;   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.