Rolling-contact shaft member

Abstract

A rolling-contact shaft member, which is made of high-carbon steel and whose outer peripheral surface serves as a rolling-contact surface that rolling-contacts a mating material, includes: a carbonitrided layer having a carbon concentration of 1.1 to 1.6 wt % and a nitrogen concentration of 0.05 to 0.6 wt % in the range from the surface to the depth of 10 μm. The rolling-contact shaft member has a Vickers hardness of 700 to 840 HV at the outer peripheral surface and has a Vickers hardness of 600 HV or less in its central portion. A maximum value of an absolute value of a gradient of a change in the Vickers hardness from the outer peripheral surface to the central portion is 100 to 340 HV/mm.

What is claimed is: 
     
         1 . A rolling-contact shaft member, which is made of high-carbon steel and whose outer peripheral surface serves as a rolling-contact surface that rolling-contacts a mating material, comprising:
 a carbonitrided layer having a carbon concentration of 1.1 to 1.6 wt % and a nitrogen concentration of 0.05 to 0.6 wt % in a range from a surface to a depth of 10 μm, wherein   the rolling-contact shaft member has a Vickers hardness of 700 to 840 HV at the outer peripheral surface,   the rolling-contact shaft member has a Vickers hardness of 600 HV or less in its central portion, and   a maximum value of an absolute value of a gradient of a change in the Vickers hardness from the outer peripheral surface to the central portion is 100 to 340 HV/mm.   
     
     
         2 . The rolling-contact shaft member according to  claim 1 , wherein
 the Vickers hardness at the outer peripheral surface is 720 to 840 HV, and   the Vickers hardness in the central portion is 550 HV or less.   
     
     
         3 . The rolling-contact shaft member according to  claim 1 , wherein
 the rolling-contact shaft member has a Vickers hardness of 210 to 300 HV at at least one of its end faces.   
     
     
         4 . The rolling-contact shaft member according to  claim 2 , wherein
 the rolling-contact shaft member has a Vickers hardness of 210 to 300 HV at at least one of its end faces.