NON-TEMPERED SOFT-NITRIDED COMPONENT

摘要

A non-tempered soft-nitrided component that comprises a base steel material having a chemical composition which comprises, in terms of mass%, 0.35-0.50% C, 0.10-0.35% Si, 2.3-2.8% Mn, up to 0.10% S, 0.0030-0.0250% N, 0-1.0% Cu, 0-0.3% Mo, 0-0.5% Ni, 0-0.020% Ti, and Fe and impurities as the remainder and which satisfies 3.10≤(0.316C+0.122)×(0.7Si+1)×(5.1Mn-1.12)×(0.364Ni+1)×(2.16Cr+1)×(3Mo+1)≤6.00, the impurities including P, Al, and Cr in amounts of up to 0.08%, up to 0.05%, and less than 0.20%, respectively. In the non-tempered soft-nitrided component, a stress concentration part has a hardness HV, as measured at a depth of 0.05 mm from the surface, of 410-480 and a hardness HV, as measured at a depth of 1.0 mm from the surface, of 200 or greater and has a compound layer depth of 5 μm or less. The metallographic structure of the base steel material is a bainite structure. The non-tempered soft-nitrided component has excellent straightenability and high fatigue strength.