COLD FORGED NON-TEMPERED HIGH-STRENGTH STEEL COMPONENT HAVING EXCELLENT IMPACT CHARACTERISTIC IN DIRECTION ORTHOGONAL TO AXIAL DIRECTION

摘要

PROBLEM TO BE SOLVED: To achieve both strength and the impact characteristics in a direction orthogonal to an axial direction in the cold forged non-tempered high-strength steel components having shaft-like parts.;SOLUTION: The cold forged non-tempered high-strength steel components having the shaft-like parts have components containing 0.20 to 0.35% C, ≤0.1% Si, 1.0 to 2.0% Mn, ≤0.02% P, ≤0.02% S, 0.05 to 0.5% Cr, ≤0.07% Al, ≤0.006% N, and ≤0.010% C, and the balance iron and inevitable impurities, in which the ratio of Mn to C (Mn/C) is ≥4, the ratio Al to N (AI/N) is ≥8, the shaft-like part is a ferrite-pearlite structure and the Gp grain size number at its cross section is ≥9.0 and the Fgc grain size number is ≥10.0 and the aspect ratio of an Mns-based inclusion at the longitudinal direction section is 6 to 7.5.;COPYRIGHT: (C)2009,JPO&INPIT