Gas quenching installation and the corresponding quenching method

Abstract

The invention relates to a gas quenching installation comprising a quenching cell ( 12 ), a buffer tank ( 10 ) which is intended to contain the quenching gas ( 6 ), gas connection means ( 32 ) which link the buffer tank ( 10 ) with the quenching cell ( 12 ) and gas supply means. Said gas supply means consist of an evaporator ( 8 ), the outlet ( 20 ) of which is connected to an inlet ( 22 ) in the buffer tank ( 10 ), and a high pressure storage tank ( 4 ) for the liquid-state quenching gas ( 6 ) which is connected to an inlet ( 16 ) in the evaporator ( 8 ), the connection means between the evaporator and the buffer tank having no gas compression means. The invention applies to installations used for the nitrogen quenching of steel parts.

1 - 14 . (canceled)  
   
   
       15 . An apparatus which may be used for gas quenching comprising: 
 a) a quenching cell to receive the objects to be quenched, wherein said cell can withstand pressurization with a quench gas up to a quenching pressure (P quench ); and    b) a pressurized quench gas delivery means connected to said cell, wherein said gas delivery means comprises: 
 1) a buffer tank for containing said quench gas at a specified buffer pressure (P buffer );  
 2) a first gas connection means that connects said buffer tank to said cell;  
 3) a first controllable shut-off means for said first gas connection means; and  
 4) a feeding means for feeding said buffer tank with said quench gas at a pressure greater than about atmospheric pressure, wherein said feed means comprises: 
 i) an evaporator;  
 ii) a second connecting means connected to both said evaporator and said buffer tank, wherein said second connecting means comprises no gas compression means;  
 iii) a high pressure storage tank for storing said quench gas in the liquid state at a storage pressure (P storage ); and  
 iv) a third connecting means connected to both said evaporator and said storage tank.  
 
   
   
   
       16 . The apparatus of  claim 15 , wherein: 
 a) said first shut off means divides said first connecting means into a buffer part associated with said buffer tank and into a cell part associated with said cell;    b) the volume of said buffer tank (V buffer ), and the volume of said buffer part (V ct ) form an effective buffer volume (V buffer,eff );    c) the volume of said cell (V cell ), and the volume of said cell part (V cc ) form an effective cell volume (V cell,eff ); and    d) said effective buffer volume (V buffer,eff ) is greater than said effective cell volume (V cell,eff ).    
   
   
       17 . The apparatus of  claim 16 , wherein said effective buffer volume (V buffer,eff ) is at least about 1.2 times greater than said effective cell volume (V cell,eff ).  
   
   
       18 . The apparatus of  claim 17 , wherein said effective buffer volume (V buffer,eff ) is between about 1.4 times and about 5 times greater than said effective cell volume (V cell,eff ).  
   
   
       19 . The apparatus of  claim 16 , wherein: 
 a) said buffer pressure (P buffer ) is greater than said quenching pressure (P quench ); and                b   )     ⁢           ⁢     V     buffer   ,           ⁢   eff         ≥       V     cell   ,           ⁢   eff       ⁢         P   quench         P   buffer     -     P   quench         .               
   
   
       20 . The apparatus of  claim 19 , wherein:  
     
       
         
           
             
               V 
               
                 buffer 
                 , 
                 
                     
                 
                 ⁢ 
                 eff 
               
             
             = 
             
               
                 V 
                 
                   cell 
                   , 
                   
                       
                   
                   ⁢ 
                   eff 
                 
               
               ⁢ 
               
                 
                   
                     P 
                     quench 
                   
                   
                     
                       P 
                       buffer 
                     
                     - 
                     
                       P 
                       quench 
                     
                   
                 
                 . 
               
             
           
         
       
     
   
   
       21 . The apparatus of  claim 15 , wherein said buffer pressure (P buffer ) is greater than or equal to about 1.2 times the quenching pressure (P quench ).  
   
   
       22 . The apparatus of  claim 21 , wherein said buffer pressure (P buffer ) is less than about 1.8 times said quench pressure (P quench ).  
   
   
       23 . The apparatus of  claim 15 , wherein said buffer pressure (P buffer ) is between about 15 and about 35 bar.  
   
   
       24 . The apparatus of  claim 15 , wherein said quenching pressure (P quench ) is between about 5 bar and about 25 bar.  
   
   
       25 . The apparatus of  claim 24 , wherein said quenching pressure (P quench ) is between about 10 bar and about 20 bar.  
   
   
       26 . The apparatus of  claim 24 , wherein said storage pressure (P storage ) is greater than said buffer pressure (P buffer ).  
   
   
       27 . The apparatus of  claim 26 , wherein said storage pressure (P storage ) is greater than about 8 bar.  
   
   
       28 . The apparatus of  claim 27 , wherein said storage pressure (P storage ) is between about 10 bar and about 40 bar.  
   
   
       29 . The apparatus of  claim 28 , wherein said storage pressure (P storage ) is between about 15 bar and about 40 bar.  
   
   
       30 . The apparatus of  claim 15 , further comprising an auxiliary quench gas supply connected to said buffer tank via an auxiliary connecting means capable of supplying said buffer tank with an auxiliary quench gas.  
   
   
       31 . The apparatus of  claim 30 , wherein said auxiliary quench gas supply comprises at least one member selected from the group consisting of hydrogen and helium.  
   
   
       32 . The apparatus of  claim 15 , wherein said quench gas comprises nitrogen.  
   
   
       33 . The apparatus of  claim 15 , wherein said quench gas comprises carbon dioxide.  
   
   
       34 . A method of operating the apparatus of  claim 15 , comprising: 
 a) filling said buffer tank with said quench gas at said buffer pressure (P buffer );    b) placing said object in said cell;    c) opening said shut-off means until said quenching pressure (P quench ) is reached in said cell;    d) cooling said object to a specified temperature; and    e) removing said object from said cell.    
   
   
       35 . A method of gas quenching comprising: 
 a) placing objects in a quenching apparatus, said apparatus comprising: 
 1) a quenching cell to receive said objects to be quenched, wherein said cell can withstand pressurization with a quench gas up to a quenching pressure (P quench ); and  
 2) a pressurized quench gas delivery means connected to said cell, wherein said gas delivery means comprises: 
 i) a buffer tank for containing said quench gas at a specified buffer pressure (P buffer );  
 ii) a first gas connection means that connects said buffer tank to said cell;  
 iii) a first controllable shut-off means for said first gas connection means; and  
 iv) a feeding means for feeding said buffer tank with said quench gas at a pressure greater than about atmospheric pressure, wherein said feed means comprises: 
 aa) an evaporator;  
 bb) a second connecting means connected to both said evaporator and said buffer tank, wherein said second connecting means comprises no gas compression means;  
 cc) a high pressure storage tank for storing said quench gas in the liquid state at a storage pressure (P storage ); and  
 dd) a third connecting means connected to both said evaporator and said storage tank; and  
 
 
   b) filling said buffer tank with said quench gas at said buffer pressure (P buffer );    c) placing said object in said cell;    d) opening said shut-off means until said quenching pressure (P quench ) is reached in said cell;    e) cooling said object to a specified temperature; and    f) removing said object from said cell.