Hot sheet metal forming by gas and direct quenching

Abstract

A hot forming by gas and direct quenching method and apparatus are disclosed. One method of using the system includes a heating step, a forming step, and a direct quenching step. This method increases the quenching speed and allows common steels with high critical cooling rate to be hot formed and quenched. This method reduces or eliminates the need for a furnace and/or the coating of the workpiece prior to the forming, as well as the removal of the coating after the forming. Furthermore, by using a hot gas containing carbon or nitrogen, the workpiece may be case hardened after the heating, forming and quenching steps.

What is claimed is: 
     
         1 . A hot sheet metal forming and direct quenching system for forming a workpiece, the system comprising:
 a gas chamber;   a workpiece disposed above the gas chamber;   a die disposed above the workpiece, the die including a die cavity;   a hot gas, wherein the hot gas enters the die cavity through a die inlet and exits the die cavity through a die outlet, and wherein the hot gas enters the gas chamber through a gas chamber inlet and exits the gas chamber through a gas chamber outlet;   
       a plurality of nozzles disposed within the gas chamber; and
 a fluid or mist being injected into the gas chamber through the plurality of nozzles. 
 
     
     
         2 . The system of  claim 1 , wherein the fluid or mist includes a mixture of water and dissolved air. 
     
     
         3 . The system of  claim 1 , wherein the workpiece includes a steel sheet. 
     
     
         4 . The system of  claim 1 , wherein the workpiece includes a composite of plain-carbon steel and low-carbon steel. 
     
     
         5 . The system of  claim 4 , wherein the hot gas contains carbon and/or nitrogen. 
     
     
         6 . The system of  claim 1 , wherein the workpiece includes a material selected from the group consisting of aluminum alloys, titanium alloys, and magnesium alloys. 
     
     
         7 . The system of  claim 1 , wherein the workpiece is configured to be moved manually or automatically in order to change a distance between the workpiece and the die. 
     
     
         8 . The system of  claim 1 , wherein the nozzles are spaced apart from one another. 
     
     
         9 . A hot sheet metal forming and direct quenching method, the method comprising:
 a heating step, the heating step comprising:
 positioning a workpiece between a die and gas chamber; 
 moving a heated gas into a die cavity disposed above the workpiece via a die inlet and out of the die cavity via a die outlet; 
 moving the heated gas into the gas chamber below the workpiece via a gas chamber inlet and out of the gas chamber via a gas chamber outlet; and 
 heating the workpiece by application of the injected heated, gas; 
   a forming step comprising:
 circulating the heated gas inside the die cavity via the die inlet and the die outlet; 
 circulating the heated gas inside the gas chamber below the workpiece via the gas chamber inlet and the gas chamber outlet; 
 forming the workpiece by increasing the gas pressure in the gas chamber and forming the workpiece to the die, the die being disposed above the workpiece; 
   a quenching step comprising:
 closing the die inlet and the gas chamber inlet; 
 opening the second outlet and de-pressurizing the gas chamber by releasing the heated gas from below the workpiece; 
 opening a plurality of nozzles and injecting a high-pressure cold fluid or mist; and 
 cooling the workpiece by application of the high-pressure cold fluid or mist. 
   
     
     
         10 . The method of  claim 9 , wherein the heating step occurs in a furnace that is separate from the gas chamber. 
     
     
         11 . The method of  claim 9 , wherein the cold fluid or mist is a mixture of water and dissolved air. 
     
     
         12 . The method of  claim 9 , wherein the workpiece includes a steel sheet. 
     
     
         13 . The system of  claim 9 , wherein the workpiece includes a composite of plain-carbon steel and low-carbon steel. 
     
     
         14 . The system of  claim 9 , wherein the gas includes carbon and/or nitrogen 
     
     
         15 . The method of  claim 9 , wherein the workpiece is selected from the group consisting of aluminum alloys, titanium alloys, and magnesium alloys. 
     
     
         16 . The method of  claim 9 , wherein the heated gas includes carbon. 
     
     
         17 . The method of  claim 9 , wherein the heated gas includes nitrogen.