PRODUCT OF STEEL FOR INDUSTRIAL HARDS, INDUSTRIAL HARDS, AND MANUFACTURING PROCEDURES THEREOF

摘要

The present invention provides a steel product that consists of, by mass%, 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, and the balance Fe and inevitable impurities, and has a structure of bainite and/or martensite, the total volume fraction of bainite and martensite being 10 % or more, and an induction hardened member that is made of the steel product having a hardened surface layer formed by induction hardening and has a prior austenite grain size of 12 mu m or less through the layer thickness. The member has high fatigue strength and therefore is suitable for an automobile drive shaft, an automobile constant velocity joint or the like. IMAGE