Method for reduction of time in a gas carburizing process and cooling apparatus

Abstract

The present invention provides a process for reduction of time in gas-carburizing process and cooling apparatus to perform carburization by step heating of a part during carburizing heating from 800° C., 850° C., 900° C. onwards to a carburization temperature of 930° C. with the part being held at each mentioned temperature for 10 minutes by adding LPG or propane along with methanol in the furnace for activation/diffusion, the holding time is thereby reduced for carburization, thereafter the carburized parts are quenched in the invented apparatus to discharge high severity of quenching.

1 . A method for reduction of time in gas-carburizing process utilizing step heating comprising the steps of:
 placing a part into a carburizing furnace;   heating said part to a first selected temperature;   holding said first temperature for a first selected time interval while adding a hydro-carbon gas along with methanol into said furnace;   heating said part to a second selected temperature;   holding said second temperature for a second selected time interval while adding a hydro-carbon gas into said furnace;   heating said part to a third selected temperature;   holding said third temperature for a third selected time interval while adding a hydro-carbon gas into said furnace;   heating said part to a final selected temperature; and   holding said final temperature for a final selected time interval while adding a hydro-carbon gas into said furnace.   
     
     
         2 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 1  wherein said first, second, third and final selected time periods are each 10 minutes long. 
     
     
         3 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 1  wherein said first selected temperature is 800° C., said second selected temperature is 850° C., said third selected temperature is 900° C. and said selected final temperature is 930° C. 
     
     
         4 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 1  further comprising the step of quenching said part in quenching oil flowing at a selected flow rate. 
     
     
         5 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 4  wherein said selected flow rate is selected to be between 1200 to 1500 rpm wherein this flow rate improves the microstructure of said part by increasing the effectiveness and severity of the quench and increases the effective case depth. 
     
     
         6 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 1  wherein said furnace is an atmospheric batch furnace. 
     
     
         7 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 1  wherein said furnace is an atmospheric continuous furnace. 
     
     
         8 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 1  wherein said hydrocarbon gas is selected from the group consisting of LPG and propane. 
     
     
         9 . A quench oil cooling gas carburizing apparatus for reducing the time required for carburization comprises:
 a chamber;   at least one circulation pipe for circulating quenching oil;   a movement means for moving said chamber to make contact with quenching oil circulating within said at least one circulation pipe; and   an agitation means in fluid contact with said quenching oil wherein said quenching oil is made to circulate at a selected flow rate.   
     
     
         10 . The quench oil cooling gas carburizing apparatus for reducing the time required for carburization according to  claim 9  further comprising a perforated grid disposed between said chamber and said circulation pipe wherein selected flow rate is reduced to a second flow rate as said quenching oil passes through said perforated grid whereby a microstructure of said part is improved. 
     
     
         11 . The quench oil cooling gas carburizing apparatus for reducing the time required for carburization according to  claim 10  wherein said selected flow rate is 1.6 m/s. 
     
     
         12 . The quench oil cooling gas carburizing apparatus for reducing the time required for carburization according to  claim 11  wherein said second flow rate is 1 m/s. 
     
     
         13 . A method for reduction of time in gas-carburizing process utilizing step heating comprising the steps of:
 placing a part in a quench oil cooling gas carburizing apparatus comprising;
 at least one circulation pipe for circulating quenching oil; 
 a movement means for moving said chamber to make contact with quenching oil circulating within said at least one circulation pipe; and 
 an agitation means in fluid contact with said quenching oil wherein said quenching oil is made to circulate at a selected flow rate; 
   heating said part to a first selected temperature;   holding said first temperature for a first selected time interval while adding a hydro-carbon gas into said furnace;   heating said part to a second selected temperature;   holding said second temperature for a second selected time interval while adding a hydro-carbon gas along with methanol into said furnace;   heating said part to a third selected temperature;   holding said third temperature for a third selected time interval while adding a hydro-carbon gas into said furnace;   heating said part to a final selected temperature; and   holding said final temperature for a final selected time interval while adding a hydro-carbon gas into said furnace.   
     
     
         14 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 13  wherein said first, second, third and final selected time periods are each 10 minutes long. 
     
     
         15 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 13  wherein said first selected temperature is 800° C., said second selected temperature is 850° C., said third selected temperature is 900° C. and said selected final temperature is 930° C. 
     
     
         16 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 13  further comprising the step of quenching said part in quenching oil flowing at a selected flow rate. 
     
     
         17 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 16  wherein said selected flow rate is selected to be between 1200 to 1500 rpm wherein this flow rate improves the microstructure of said part by increasing the effectiveness and severity of the quench and increases the effective case depth. 
     
     
         18 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 13  wherein said furnace is an atmospheric batch furnace. 
     
     
         19 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 13  wherein said furnace is an atmospheric continuous furnace. 
     
     
         20 . The method for reduction of time in gas-carburizing process utilizing step heating according to  claim 13  wherein said hydrocarbon gas is selected from the group consisting of LPG and propane.