Method of manufacturing machine component

Abstract

A method of manufacturing a machine component includes the steps of preparing a member made of steel containing 0.1 mass % or more of vanadium, forming a film containing vanadium at a surface of the member, and forming a nitrogen-enriched layer by heating the member having the film formed in a heat treatment gas atmosphere containing nitrogen gas and absent of ammonia gas. In the step of forming a film, the member is heated to and oxidized in a temperature range not lower than 500° C. and lower than A 1 transformation point of steel.

1 . A method of manufacturing a machine component comprising the steps of:
 preparing a member made of steel;   forming a film containing vanadium at a surface of said member; and   forming a nitrogen-enriched layer by heating said member having said film formed in an atmosphere of heat treatment gas containing nitrogen gas and absent of ammonia gas,   in said step of preparing a member, a member made of steel containing 0.1 mass % or more of vanadium being prepared, and   in said step of forming a film, said member being heated to and oxidized in a temperature range not lower than 500° C. and lower than A 1  transformation point of said steel.   
     
     
         2 . The method of manufacturing a machine component according to  claim 1 , wherein
 said heat treatment gas includes endothermic converted gas.   
     
     
         3 . The method of manufacturing a machine component according to  claim 1 , wherein
 said heat treatment gas is a gas mixture of the nitrogen gas and reducing gas.   
     
     
         4 . The method of manufacturing a machine component according to  claim 1 , wherein
 said heat treatment gas includes the nitrogen gas and has an oxygen partial pressure less than or equal to 10 −16  Pa.   
     
     
         5 . The method of manufacturing a machine component according to  claim 4 , wherein
 said heat treatment gas includes reducing gas so that it has the oxygen partial pressure less than or equal to 10 −16  Pa.   
     
     
         6 . The method of manufacturing a machine component according to  claim 5 , wherein
 said reducing gas is hydrogen gas.   
     
     
         7 . The method of manufacturing a machine component according to  claim 1 , wherein
 said step of forming a nitrogen-enriched layer is performed such that said member heated to said temperature range is not cooled to a room temperature in said step of forming a film.   
     
     
         8 . The method of manufacturing a machine component according to  claim 1 , wherein
 in said step of forming a film, said member is heated in a heat treatment chamber of an oxidative atmosphere, and   in said step of forming a nitrogen-enriched layer, an atmosphere in said heat treatment chamber is replaced with said heat treatment gas and then said member is heated in said heat treatment chamber to thereby form the nitrogen-enriched layer.   
     
     
         9 . The method of manufacturing a machine component according to  claim 1 , further comprising the step of quench-hardening said member by cooling said member having a nitrogen-enriched layer formed from a temperature greater than or equal to the A 1  transformation point down to a temperature less than or equal to M S  point, wherein
 in said step of forming a film, said film is formed as said member is oxidized in an oxidation apparatus,   in said step of forming a nitrogen-enriched layer, said member having said film formed is conveyed by a conveyance apparatus into a nitrogen-enriched layer formation apparatus connected to said oxidation apparatus with said conveyance apparatus being interposed and then said nitrogen-enriched layer is formed in said nitrogen-enriched layer formation apparatus, and   in said step of quench-hardening said member, said member is quench-hardened in a quenching apparatus connected to said nitrogen-enriched layer formation apparatus.   
     
     
         10 . The method of manufacturing a machine component according to  claim 1 , wherein
 said machine component is a component constituting a rolling bearing.