| 摘要 |
PROBLEM TO BE SOLVED: To provide a non-heat treated steel for induction contour hardening gear, capable of providing homogeneous hardened layer structure even if a hardening process by ultrashort-time heating, that is, an induction contour hardening process is adopted and capable of providing a gear product having high rolling contact fatigue strength, at the time of manufacturing a gear by using the non-heattreated steel as a material and applying hot forging and successive machining to it. SOLUTION: The steel has a composition consisting of, by weight, 0.45-0.8% C, 1.0-2.0% Si, 0.1-1.5% Mn, 0.05-1.0% Cr, 0.05-0.3% V, 0.015-0.05%; sol.Al, and the balance Fe with impurities. This steel satisfies the condition of (hardenability index)=1.2-1.4×C(%)-0.28×Mn(%)-0.49×Cr(%)<=0.3, and the tempering hardness of the hardened material at 300 deg.C is regulated to >=HV600. This steel can further contain either or both of the following optional additive elements: (I) 0.0005-0.005% B and 0.005-0.05% Ti; and (II) <=0.2% S and/or <=0.1% Te.
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