| 摘要 |
PROBLEM TO BE SOLVED: To provide a wheel supporting rolling bearing unit with an inner ring caulked and fixed to a hub ring, having a longer rolling fatigue life. SOLUTION: In the inner ring 2 of the wheel supporting rolling bearing unit, an austenite crystal grain size Sγof a surface layer portion forming a second inner ring raceway surface 2a and the maximum grain size Sc of carbide existing in the surface layer portion are satisfied with Sγ-15Sc+2≥0. The hardness of a core portion is Hv250-Hv450. The hardness of the surface layer portion forming the second inner ring raceway surface 2a and a face 2b fitted to the hub ring 10 is greater than that of the core portion. Besides, a hoop tension value remaining on a small outer diameter face 21 of the inner ring 2 is 150 MPa-260 MPa. COPYRIGHT: (C)2007,JPO&INPIT
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