Single-chamber vacuum furnace with hydrogen quenching

Abstract

A method for operating a hardening furnace with hydrogen cooling, including filling the interior of the furnace with workpieces, sealing the interior of the furnace and evacuating it, filling the interior of the furnace with an inert gas, convective heating the workpieces with circulation of the inert gas, evacuating the interior of the furnace, further heating the workpieces by radiant heating and maintaining a theoretical temperature, switching off the heating, filling the interior of the furnace with hydrogen under high pressure, and circulating the hydrogen for cooling the workpieces, evacuating the interior of the furnace and filling it with an inert gas up to approximately atmospheric pressure, and opening the furnace and unloading the workpieces.

1 . A method for operating a single-chamber vacuum hardening furnace, including the steps of: 
 filling an interior of the furnace with workpieces;    sealing the interior of the furnace;    evacuating the interior of the furnace;    heating the workpieces and maintaining a theoretical temperature;    filling the interior of the furnace with hydrogen under high pressure, switching off the heating and circulating the hydrogen for cooling the workpieces;    discharging the hydrogen and evacuating the interior of the furnace;    filling the interior of the furnace with an inert gas up to approximately atmospheric pressure; and    opening the furnace and unloading the workpieces.    
   
   
       2 . A method according to  claim 1 , which, between the evacuating and heating steps, includes the further steps of: 
 filling the interior of the furnace with an inert gas;    convective heating the workpieces with circulation of the inert gas; and    evacuating the interior of the furnace.    
   
   
       3 . A method according to  claim 2 , wherein the inert gas of at least one of said filling steps is nitrogen.  
   
   
       4 . A method according to  claim 1 , wherein said discharging step comprises conveying the hydrogen out of an operating building via a flue.  
   
   
       5 . A method according to  claim 4 , wherein said flue is higher than a roof height of the operating building.  
   
   
       6 . A method according to  claim 1 , wherein during and/or after said step of heating the workpieces and maintaining a theoretical temperature, a gas containing carbon is conveyed at least one time into the interior of the furnace.  
   
   
       7 . A method according to  claim 6 , wherein said gas containing carbon is pumped out of the interior of the furnace prior to said step of filling the interior of the furnace with hydrogen under high pressure.  
   
   
       8 . A method according to  claim 6 , wherein said gas is a acetylene.  
   
   
       9 . A method according to  claim 8 , wherein a carrier gas is added to said acetylene.  
   
   
       10 . A method according to  claim 1 , wherein a fan is provided for circulating the hydrogen, and wherein the speed of the fan is adapted to be regulated.  
   
   
       11 . A device for carrying out the method of  claim 1 , and comprising a safety zone that surrounds the hardening furnace, wherein the safety zone is adapted to prevent walking or travelling in the immediate vicinity of the furnace, with the exception of a front side of the furnace that is adapted to be opened by mechanical or electrical means.