Patent ID: 7678207

Claim:
A method for manufacturing an induction hardened member comprising the step of: hot working a steel consisting of C: 0.35-0.7%, Si: 0.30-1.1%, Mn: 0.2-2.0%, Al: 0.005-0.25%, Ti: 0.005-0.1%, Mo: 0.05-0.6%, B: 0.0003-0.006%, S: 0.06% or less, P: 0.02% or less, Cr: 0.2% or less, by mass, and a balance of Fe and inevitable impurities; cooling the hot worked steel at a cooling rate of at least 0.2° C./s, thereby manufacturing a steel product having a structure of bainite and/or martensite, the total volume fraction of bainite and martensite being 10% or more; subjecting the steel product to induction hardening at least once, wherein the heating temperature of the final induction hardening is 800-950° C., wherein the thickness of a hardened layer formed on the surface of the steel product by induction hardening is 2 mm or more, and the prior austenite grain size of the hardened layer is 8 μm or less through the thickness of the hardened layer.