Excellent induction hardening gear and a method of manufacturing the same in wear resistance and surface fatigue characteristics

摘要

PROBLEM TO BE SOLVED: To provide a gear having excellent wear resistance and surface fatigue characteristics that is suitable for use in automobiles and various industrial machines, and a manufacturing method therefor.;SOLUTION: An induction hardening gear includes a component composition containing, by mass%, 0.25-0.65% of C, 0.70-2.00% or more of Si, 0.30-2.00% of Mn, 1.50% or less of Cr, and, as needed, one or more of 0.010-0.060% of Nb, 0.005-0.050% of Ti, and 0.0005-0.0100% of B in which the value of Z calculated by formula (1) is 15≤Z≤30, the balance being Fe and inevitable impurities. The structure of the induction hardening part is mainly of tempered martensite inside of which 90 or more carbides with a grain size of less than 300 nm per 100 μm² are finely dispersed. Formula (1): Z=10Si+Cr+50 (D×Ceq)/A where Si and Cr represent the amount of the respective elements contained (mass%), and D, Ceq, and A represent the hardenability index, carbon equivalent and Ac₃ transformation point respectively. The steel of the component composition is subjected to hardening and tempering after being hot forged and processed to a gear shape, and subjected to induction hardening and tempering as a surface hardening heat treatment.;COPYRIGHT: (C)2013,JPO&INPIT