Low pressure induction carburization

Abstract

An apparatus for low pressure induction carburization including a hermetic, low pressure carburization chamber fitted with an inlet port for receiving a carburizing gas; an article support base within the chamber; an article disposed or secured on the article support base; and an electromagnetic induction structure shaped and disposed with respect to the article to direct an electromagnetic field into a first portion of a surface the article for directed induction heating of the article. The carburization chamber includes a low-pressure carburizing gas that was received into the chamber through the inlet port, and the first portion of the surface of the article is at a temperature in excess of a carburizing temperature.

What is claimed is: 
     
         1 . An apparatus for low pressure induction carburization comprising:
 a hermetic, low pressure carburization chamber fitted with an inlet port for receiving a carburizing gas;   an article support base within the chamber;   an article disposed or secured on the article support base; and   an electromagnetic induction structure shaped and disposed with respect to the article to direct an electromagnetic field into a first portion of a surface the article for directed induction heating of the article,   wherein the carburization chamber comprises a low pressure carburizing gas that was received into the chamber through the inlet port, and wherein the first portion of the surface of the article is at a temperature in excess of a carburizing temperature.   
     
     
         2 . The apparatus of  claim 1 , further comprising a cooling object disposed with respect to a second portion of the surface of the article, and wherein the second portion of the surface of the article is at a temperature below the carburizing temperature. 
     
     
         3 . The apparatus of  claim 1 , further comprising an additional inlet port for receiving a neutral gas. 
     
     
         4 . An apparatus for low pressure induction carburization comprising:
 a hermetic, low pressure carburization chamber fitted with an inlet port for receiving a carburizing gas;   an article support base within the chamber;   an iron or iron alloy article disposed or secured on the article support base; and   an electromagnetic induction structure shaped and disposed with respect to the article to direct an electromagnetic field into a first portion of a surface the article for directed induction heating of the article to a carburizing temperature in excess of about 1550° F. (about 843° C.); and   a cooling object disposed with respect to a second portion of the surface of the article, and wherein the second portion of the surface of the article is at a temperature below the carburizing temperature, wherein the cooling object provides both convective and conductive cooling to the second portion of the surface of the article,   wherein the carburization chamber comprises a low pressure carburizing gas that was received into the chamber through the inlet port at a pressure that is from about 5 mbar to about 20 mbar (about 500 Pa to about 2000 Pa), and wherein the first portion of the surface of the article is at a temperature in excess of the carburizing temperature simultaneously with the second portion of the surface of the article being at the temperature below the carburizing temperature.   
     
     
         5 . The apparatus of  claim 4 , further comprising an additional inlet port for receiving a neutral gas. 
     
     
         6 . The apparatus of  claim 4 , wherein the article comprises a gear comprising a plurality of teeth. 
     
     
         7 . The apparatus of  claim 6 , wherein the first portion of the surface of the article comprises the plurality of teeth and wherein the second portion of the surface of the article comprises a surface of the gear that is radially inward from the plurality of teeth. 
     
     
         8 . The apparatus of  claim 4 , wherein the carburizing gas comprises acetylene (C 2 H 2 ) and the neutral gas comprises molecular nitrogen (N 2 ). 
     
     
         9 . The apparatus of  claim 4 , wherein no portion of the article is masked with a masking coating layer. 
     
     
         10 . The apparatus of  claim 4 , wherein the carburizing chamber is at a pressure of from about 7 mbar to about 13 mbar (about 700 Pa to about 1300 Pa).