CASE-HARDENING STEEL BEING EXCELLENT IN CONTACT PRESSURE FATIGUE STRENGTH, IMPACT STRENGTH AND BENDING FATIGUE STRENGTH

摘要

It is intended to provide a case-hardening steel which is capable of improving all of the characteristics including contact pressure fatigue strength, impact strength and bending fatigue strength of a carburized gear and elevating the strength of a carburized member by gas carburization at a low cost. This case-hardening steel is one comprising, in terms of % by mass, 0.10 to 0.35% of C, 0.40 to 1.50% of Si, 0.10 to 1.50% of Mn, not more than 0.030% of P, not more than 0.030% of S, 0.50 to 3.00% of Cr, 0.02 to 0.20% of Ti, 0.005 to 0.050% of Al, 0.0010 to 0.0050% of B, not more than 0.0100% of N, 0 to 3.00% of Ni, 0 to 1.00% of Mo, 0 to 0.20% of Nb, 0 to 0.20% of V, and the balance Fe and unavoidable impurities, wherein the requirements Ti3.4N and 7Si+3Cr+Mn≥7.0 are satisfied and the abnormal layer depth in gas carburization is 10 μm or less.