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Chromium and chromium-molybdenum carburizing steels are widely used for small- and medium- sized rolling bearings or gears, in Japan. Using a cylinder-to-ball type rolling contact fatigue rig, influence of various material factors such as chemical compositions, oxygen content, retained austenite and grain size in 1 % chromium carburizing steel was investigated. Life level of 1 % chromium steel has been increased gradually since 1968 when the test began. The increase in life level is mainly due to reduction in oxygen content by the improvement of steel-making technique. Manganese content increases the life and 1 % Cr steel with 1 % Mn has high reliable life. Prior austenite grain size does not seem to influence the rolling contact fatigue life.

Recently a demand for maintenance-free is increaing for mechanical components. We have already developed spherical plain bearings fitted with liners for railroad vehicles, which are now used in such places as anti-rolling equipments or longitudinal dampers in the vehicles for The New Tokaido Line. On the other hand, in construction machines or the like, development of a spherical bearing with high impact strength, resistance to high contact pressure and high resistance against muddy water is demanded. Investigations into anti-wear performance as well as creep resistance of various liner materials were made. It was found that polyimide resin with some fillers is the most superior.