To provide a rolling device having the prolonged life by refining crystal grains in the material.
The rolling device employs a high-carbon bearing steel containing 0.5 wt.% or more C in at least one of an inner member, an outer member and a rolling element as the base material, makes the surface layer of a rolling contact side of a finished product consist of former austenite crystal grains with an average size of 3 μm or smaller, and have a nitrogen concentration of 0.3 wt.% or higher by nitriding or soft nitriding the high-carbon bearing steel during heat treatment. The heat treatment comprises: the first step of heating the material to 800 to 1,000°C to austenitize the metallographic structure, and then converting it into a martensite structure by quenching it; the second step of nitriding or soft nitriding it at a temperature of an Ae1 transformation point or lower; the third step of heating it to an austenitic temperature range of 780 to 880°C, and quenching it; and the fourth step of tempering it.
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UEDA KOJI
Yoshiaki Naito
Cui Shu Tetsu