| 摘要 |
PURPOSE:To improve load resistance and shock resistance in characteristics a bearing ring so as to prevent the generation of harmful permanent deformation on a raceway surface by specifying a ball diameter, a pitch circle diameter, and a residual austenite amount in steel composing at leapt one of an inner ring raceway and an outer ring raceway in a ball bearing. CONSTITUTION:Generally, in a high precision small size ball bearing 3 used for a hard disk drive device HDD, for example, diameters Dw of plural balls 8, 8 built in between an inner ring raceway and an outer ring raceway are 3mm or less, while a diameter Dpw of a pitch circle, in which these plural balls 8, 8 are arranged, is 11mm or less. Especially, a residual austenite amount in steel such as bearing steel and stainless steel composing at least one of the inner ring raceway 4 and the outer ring raceway 6 in the ball bearing 3 is set to 6% by volume or less. As the amount of austenite, which has less yield stress than martensite, is reduced, impression resistance on the raceway surface is improved, and a harmful deformation is hardly caused by a small load. On the other hand, deterioration with the lapse of time in the surface precision of the raceway surface can be prevented.
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