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|1. (WO2018047955) CASE-HARDENED STEEL, METHOD FOR PRODUCING SAME, AND METHOD FOR MANUFACTURING GEAR PART|
|Applicants:||JFE STEEL CORPORATION
|Title:||CASE-HARDENED STEEL, METHOD FOR PRODUCING SAME, AND METHOD FOR MANUFACTURING GEAR PART|
Provided are: a case-hardened steel suitable as a material for manufacturing a mechanical structural part having high rotary bending fatigue strength and impact fatigue strength at relatively low cost; and a method for producing the case-hardened steel. The case-hardened steel contains C, Si, Mn, P, S, Cr, Mo, B, Ti, N, and O in mass% determined by predetermined relationships, contains at least a predetermined amount of Al in relation to the amounts of B, N, and Ti, and contains the remainder comprising Fe and inevitable impurities. Moreover, √I≤80 is satisfied (where I represents the area (μm2) of oxide-based inclusions located at the center of the fisheye in the fractured surface following a rotary bending fatigue test conducted after subjecting the case-hardened steel to carburizing quenching and tempering).