| 摘要 |
PROBLEM TO BE SOLVED: To ensure a long durable life even under the inclusion of foreign matter by forming at least the rolling element of a rolling bearing by use of a steel material containing a specified composition by weight ratio, and determining the residual austenite quantity on the surface layer within a specified range. SOLUTION: For example, the shaft of a differential gear case 7 is supported by a gear shaft support device formed of conical roll bearings 2, 3, and 6. Each part of the conical roll bearings 2, 3 and 6 is molded by use of steel containing C: 0.8-1.5%, Si: 0.4-1.2%, Mn: 0.8-1.5%, and Cr: 0.8-1.8%. When this material is carbonitrided to increase the nitrogen content in the surface layer part, the Ms point (martensite transformation starting point) in the surface layer part is lower than in the inner part. Therefore, when this material is hardened, non-transformed austenite is increased in the rolling element surface layer part, so that the residual austenite quantity in the surface layer part can be set within the range of 20-40% by volume. According to this, the surface peeling can be suppressed to extend the durable life.
|
