| 摘要 |
PROBLEM TO BE SOLVED: To obtain an automotive hub unit beating which has an excellent fatigue life and excellent fatigue strength of a flange integrate into an outer ring while improving the machinability of the outer ring. SOLUTION: An alloy steel stock contains 0.05 to 0.95% C, 0.50 to 1.50% Si, 0.05 to 0.60% Mn,≤0.0035% S, and≤0.0015% O. This stock is subjected to graphitization treatment, a forming, stage and a machining stage in this order. The graphitization treatment is performed so that the content of a graphite structure in the machining stage reaches 0.5 to 3.0% by an area ratio. After the machining stage, the raceway grooves of the outer ring are subjected to induction hardening and tempering treatment, so that, in the surface layer parts thereof, a hardness is controlled to≥60 HRC, the content of retained austenite is controlled to≥10 vol.%, and the grain size of graphite present therein is controlled to≤1.0μm. COPYRIGHT: (C)2003,JPO
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