Heat Treatment Process for Engine Ring Gear

Abstract

The present disclosure relates to methods of hardening toothed gear parts for engines. The method results in a uniformly hardened gear with minimized distortion.

What is claimed is: 
     
         1 . A method of hardening a toothed gear comprising steel, the steel comprising an iron alloy comprising about 0.2-0.8 % carbon, the method comprising
 (a) heating the gear to a temperature greater than the austenitizing temperature of the steel.   (b) quenching the gear to a temperature between the Martensite temperature for the steel and a temperature about 20° F. higher than the Martensite start temperature for the steel, namely the quenching temperature, and holding the gear at the quenching temperature until the gear is quenched to the quenching temperature uniformly throughout; and   (c) further quenching the gear in ambient air conditions.   
     
     
         2 . The method of  claim 1 , wherein in step (a) the gear is heated to a temperature greater than about 1400° F. 
     
     
         3 . The method of  claim 1 , wherein in step:(a) the gear is heated lo a temperature greater than about 1500° F. 
     
     
         4 . The method of  claim 1 , wherein in step (a) the gear is heated to a temperature greater than about 1600° F. 
     
     
         5 . The method of  claim 1 , wherein in step (a) the gear is heated to a temperature between about 1400-1800° F. 
     
     
         6 . The method of  claim 1 , wherein step (a) is performed for at least about 3 minutes. 
     
     
         7 . The method of  claim 1 , wherein step (a) is performed for at least about 1 hour. 
     
     
         8 . The method of  claim 1 , wherein step (a) is performed by placing the gear into a molten salt bath. 
     
     
         9 . The method of  claim 1 , wherein step (a) is performed until the gear is completely transformed to austenite. 
     
     
         10 . The method of  claim 1 , wherein in step (b). the gear is quenched to a temperature between about 250-1000° F. 
     
     
         11 . The method of  claim 1 , wherein in step (b) the gear is quenched to a temperature between about 350-650° F. 
     
     
         12 . The method of  claim 1 , wherein in step (b) the gear is quenched to a temperature between about 395-630° F. 
     
     
         13 . The method of  claim 1 , wherein step (b) is performed for at least about 1 minute. 
     
     
         14 . The method of  claim 1 , wherein step (b) is performed for at least about 3 minutes. 
     
     
         15 . The method of  claim 1 , wherein step (b) is performed for about 3-6 minutes. 
     
     
         16 . The method of  claim 1 , wherein step (b) is performed by placing the gear into a molten salt bath or a molten lead bath. 
     
     
         17 . The method of  claim 1 , wherein the gear is quenched at a rate of at least about −100° F./second. 
     
     
         18 . The method of  claim 1 , further comprising step (d) subsequently heating the quenched gear to a temperature above the Martensite start temperature for the steel of which the gear is comprised and subsequently quenching the further heated gear.