Method of heat treating a steel component

Abstract

Method for heat treating a steel component ( 28, 36 ) to provide the steel component ( 28, 36 ) with a surface having improved wear resistance. The method comprises the steps of carbonitriding the steel component ( 28, 36 ) at a temperature of 930-970° C., cooling the steel component ( 28, 36 ), re-heating the steel component ( 28, 36 ) to a temperature of 780-820° C. and either quenching the steel component ( 28, 36 ) to form martensite and tempering, or quenching the steel component ( 28, 36 ) to form bainite and tempering.

1 . A method for heat treating a steel component that provides a surface having improved wear resistance, the method comprising the steps of:
 a) carbonitriding the steel component at a temperature of 930-970° C.,   b) cooling the steel component,   c) re-heating the steel component to a temperature of 780-820° C., and including one of the following steps;   d) quenching the steel component to form martensite, and tempering, and   e) quenching the steel component to form bainite.   
     
     
         2 . The method according to  claim 1 , wherein step a) further comprises carbonitriding the steel component at a temperature of 930-970° C. for 5-10 hours. 
     
     
         3 . The method according to  claim 1 , wherein the steel component ( 28 ,  36 ) comprises steel with a carbon content of 0.6 to 1.20 weight %. 
     
     
         4 . The method according to  claim 1 , wherein step e) further comprises quenching the steel component to form bainite, and tempering. 
     
     
         5 . The method according to  claim 1 , wherein the steel component provides at least one of a rolling element and roller, and a steel component for an application in which is subjected to alternating Hertzian stresses. 
     
     
         6 . The method according to  claim 1 , wherein as a result of the method, the steel component provided with a carbonitrided layer having a thickness (d) of 0.3-1.5 mm wherein all of the carbides in the carbonitrided layer have a maximum longitudinal dimension of 0.2-0.3 m. 
     
     
         7 . The method according to any of the preceding claims,  claim 1 , wherein as a result of the method, the steel component is provided with a carbonitrided layer having a ratio (d:D) of depth (d) of the carbonitrided layer measured from the surface of the steel component to maximum transverse dimension (D) of said steel component of 1:4000 to 1:17,000 or more. 
     
     
         8 . A steel component comprising;
 a carbonitrided layer having a depth of the carbonitrided layer measured from the surface of the steel component of 0.3-1.2 mm, wherein   all of the carbides in the carbonitrided layer have a maximum longitudinal dimension of 0.2-0.3 m.   
     
     
         9 . The steel component according to  claim 8 , further comprising steel with a carbon content of 0.6 to 1.2 weight %. 
     
     
         10 . The steel component according to  claim 9 , further comprising at least one of a rolling element and roller, and a steel component for an application subjected to alternating Hertzian stresses. 
     
     
         11 . The steel component according to  claim 8 , further comprising a carbonitrided layer having a ratio (d:D) of depth (d) of the carbonitrided layer of the carbonitrided layer measured from the surface of the steel component to maximum transverse dimension (D) of said steel component of 1:4000 to 1:17,000 or more. 
     
     
         12 . A steel component for use under contaminated and/or poor lubricant conditions comprising:
 a carbonitrided layer having a depth of the carbonitrided layer measured from the surface of the steel component of 0.3-1.2 mm, wherein   all of the carbides in the carbonitrided layer have a maximum longitudinal dimension of 0.2-0.3 m.