| 摘要 |
In order to provide a ball-and-roller bearing that has a longer life and which exhibits higher reliability than the prior art products not only under lubrication in the presence of foreign matter but also under lubrication in clean conditions, according to the present invention, a bearing material that contains 0.2 to 1.0 wt % of carbon and at least 1 wt % in total of one or more elements selected from among chromium, molybdenum and vanadium is subjected to a carbonitriding treatment and a hardening heat treatment to make an alloy steel in which the area ratio of carbonitrides present in the surface layer of said bearing material per unit area is adjusted to be at least 10%, a maximum grain size of carbonitrides present in said surface layer being no more than 3 mu m, the content of retained austenite ( gamma R) in said surface layer being 25 to 45 vol %, and said surface layer having a surface hardness of at least 750 Hv. At least one of the races and rolling elements of the bearing is made of this alloy steel.
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