CASE HARDENING STEEL HAVING EXCELLENT ROLLING FATIGUE PROPERTY AND CRYSTAL GRAIN COARSENING PREVENTION PROPERTY

摘要

PROBLEM TO BE SOLVED: To provide a case hardening steel giving case-hardened parts having excellent workability and crystal grain coarsening prevention properties and further having an excellent rolling fatigue life as the stock for bar-shaped machine parts such as a pulley for a CVT (Continuously Variable Transmission) requiring a carburizing depth and a rolling fatigue life.;SOLUTION: The case hardening steel having excellent rolling fatigue properties and crystal grain coarsening prevention properties is composed of a steel having a composition in which the contents of C, Si, Mn, S, Cr or the like are specified, and particularly comprising 0.008 to 0.025% N, 0.040 to 0.120% Al, 0.01 to 0.20% Nb and 0.005 to 0.020% Ti, and the balance Fe with inevitable impurities. Within 100 μm² in the cross-sectional face of the steel, nitrides, carbides or carbonitrides with the major axis of 0.01 to 0.1 μm comprising Ti are present by ≥5 pieces, and also, a nitride(s), a carbide(s) or a carbonitride(s) with the major axis of 0.01 to 0.1 μm comprising Ti and Al is present by ≥1 piece.;COPYRIGHT: (C)2007,JPO&INPIT