Nippon Seiko Kabushiki Kaisha

Nsk Corporation

Kousuke Nonaka

Yoichi Matsumoto

Kenji Yamamura

Yasuo Utsumi

At least one of the inner race, the outer race and rolling elements in the improved ball-and-roller bearing is made of an alloy steel that contains 0.1-1.2 wt % of C, 3.0-18.0 wt % of Cr, 0.01-1.5 wt % of Si, 0.3-1.5 wt % of Mn, up to 2.5 wt % of Mo, up to 0.002 wt % of O.sub.2 and up to 0.015 wt % of S and which is subjected to plasma-assisted carburization to such an extent that the relative surface carbon area is at least 15% the surface carbon concentration is in the range of 1.6-3.5 wt % and the amount of surface retained austenite is in the rang of 20 vol %-45 vol %. The bearing can work effectively for a prolonged lifetime even if it is placed under hostile conditions as exemplified by an increased areal pressure of load and entrance of foreign matter into lubricating oils.

Ball-and-roller bearing

A rolling member used as an outer race, inner race, a ball or roller of a bearing contains a metal flow in the structure formed by plastic working (fold forging). The angle of metal flow determined by a tangent line of the metal flow and the axis of rotation of the rolling member is 10.degree. or larger to improve the service line against rolling fatigue.

Rolling member

A rolling bearing comprise a bearing ring having inner and outer rings, and rolling elements. At least one of the inner and outer rings and the rolling elements is formed of a sintered alloy steel and has pores and carbides present therein. The largest one of the pores has a diameter equal to or smaller than 3 .mu.m in terms of a diameter assued if the largest pore were converted to a spherical shape. The largest one of the carbides has a diameter equal to or smaller than 12 .mu.m in terms of a diameter assumed if the largest carbide were converted to a spherical shape. The at least one of the inner and outer rings and the rolling elements has hardness higher than 64 and lower than 69 in terms of HRC.

Growing community of inventors

Fujisawa, Japan

Kousuke Nonaka