CASE HARDENING STEEL EXCELLENT IN LOW CYCLE FATIGUE STRENGTH

摘要

PROBLEM TO BE SOLVED: To obtain a case hardening steel excellent in low cycle fatigue strength accompanying macroscopic strains by preparing a case hardening steel in which the chemical componental compsn. is specified and the relation among alloy elements is also strictly prescribed by formulae and inequalities to improve the plastic deformation resistance and intergranular strength. ;SOLUTION: A case hardening steel having a compsn. contg., by mass, 0.15 to 0.30% C, 0.5 to 3.0% Mn, ≤0.50% Si, ≤0.010% P, ≤0.035% S, 0.3 to 2.0% Cr, 0.45 to 1.0% Mo, 0.003 to 1.0% Nb, 0.015 to 0.060% Al and 0.003 to 0.030% N, in which the content of O is regulated to ≤20 ppm, and the balance Fe with inevitable impurities is prepd. At this time, the plastic deformation resistance HVav and intergranular strength Iequ1 and Iequ2 prescribed by the formulae, I, II and III satisfy the inequalities IV and V. Furthermore, in the formulae, [C], [Si], [Mn], [P], [S], [Mo], [Nb], and [Cr] respectively denote the mass % of each element.;COPYRIGHT: (C)1998,JPO