Rolling apparatus

Abstract

A rolling apparatus including an external member having a raceway surface on an inner peripheral surface thereof, an internal member having a raceway surface on an outer peripheral surface thereof, and a plurality of rolling elements which are rotatably provided between the raceway surface of the external member and the raceway surface of the internal member. A surface of at least one of the internal member, the external member, and the rolling elements is subjected to carbonitriding or nitriding; an area percentage of a nitride containing Si and Mn is 1% or more and 20% or less; surface hardness is HV750 or more. When depth from the raceway surface or depth from a rolling surface of the rolling element is defined as Z and diameter of the rolling element is defined as d, hardness at Z=0.045 d is HV650 to 850, and hardness at Z=0.18 d is HV400 to 800.

The invention claimed is: 
     
       1. A rolling apparatus comprising:
 an external member having a raceway surface on an inner peripheral surface thereof; 
 an internal member having a raceway surface on an outer peripheral surface thereof; and 
 a plurality of rolling elements which are rotatably provided between the raceway surface of the external member and the raceway surface of the internal member, wherein the rolling elements are made of steel which contains 
 0.95 to 1.10 mass % of C, 
 0.4 to 0.7 mass % of Si, 
 0.9 to 1.15 mass % of Mn, 
 0.9 to 1.20 mass % of Cr, 
 remaining Fe and inevitable impurities, and 
 wherein a surface of at least one of the internal member, the external member, and the rolling elements is subjected to carbonitriding or nitriding, 
 an area percentage of a nitride containing Si and Mn is 1% or more and 20% 3.65% or less, 
 a hardness on a surface is HV750 or more, 
 a concentration of nitrogen on a surface layer of at least one of the internal element, the external element, and the rolling elements is 0.2 mass % to 0.64 mass %, and 
 when depth from the raceway surface or depth from a rolling surface of the rolling element is defined as Z and diameter of the rolling element is defined as d, hardness at Z=0.045d is HV650 HV770 to 850 816, and hardness at Z=0.18d is HV400 HV700 to 800 771, 
 when an amount of retained austenite on the raceway surfaces is defined as γr AB  and when an amount of retained austenite on the rolling surface of the rolling element is defined as γr C , 
 γr AB −15≤γr C ≤γr AB +15 (0≤γr AB , γr C ≤50, and a unit is vol. %) is satisfied. 
 
     
     
       2. The rolling apparatus according to  claim 1 , wherein
 a concentration of nitrogen on a surface layer of at least one of the internal element, the external element, and the rolling elements is 0.2 mass % or more, and a number of nitride of which size is 0.05 μm to 1 μm and which contains Si and Mn in an area of 375 μm 2  is 100 or more. 
 
     
     
       3. The rolling apparatus according to  claim 2 , wherein
 at least one of the carbonitrided or nitrided internal member, external member, and rolling elements is made of steel which contains   0.3 to 1.2 mass % of C,   0.3 to 2.2 mass % of Si,   0.3 to 2.0 mass % of Mn,   0.5 to 2.0 mass % of Cr,   5 or less of Si/Mn,   remaining Fe and   inevitable impurities.   
     
     
       4. The rolling apparatus according to claim  3  1, wherein
 a carbonitrided or nitrided member is the rolling elements. 
 
     
     
       5. The rolling apparatus according to  claim 4 , wherein, when an amount of retained austenite on the raceway surfaces is defined as γr AB  and when an amount of retained austenite on the rolling surface of the rolling element is defined as γr C ,
 γr AB −15≤γr C ≤γr AB +15 (0≤γr AB , γr C ≤50, and a unit is vol. %) is satisfied.