NON-TEMPERED STEEL SOFT NITRIDED COMPONENT

摘要

This invention provides a non-tempered steel soft nitrided component that, even when soft nitriding is carried out in such a state that tempering is omitted, has high fatigue strength and excellent bending correction properties. The soft nitrided component is characterized in that it is produced by soft-nitriding a machinical component of a non-tempered steel characterized by comprising by mass C: 0.30 to 0.45%, Si: 0.1 to 0.5%, Mn: 0.6 to 1.0%, Ti: 0.005 to 0.1%, and N: 0.015 to 0.030% with the balance consisting of Fe and impurities and having a mixed texture comprising bainite and ferrite or a mixed texture comprising bainite, ferrite, and pearlite, the bainite fraction in the mixed texture being 5 to 90%, and that the texture of the diffusion layer in the mixed texture is such that the size of a rod-like ?' nitride, in the longitudinal direction, present within ferrite grains in the diffusion layer is not more than 20 µm. The steel as a material to be subjected to this soft nitriding treatment may contain one or more of Nb: 0.001 to 0.1%, Mo: 0.01 to 1.0%, Cu: 0.01 to 1.0%, Ni: 0.01 to 1.0%, B: 0.001 to 0.005%, S: 0.01 to 0.1%, and Ca: 0.0001 to 0.005%.