STEEL FOR STRUCTURAL USE HAVING EXCELLENT COLD FORGEABILITY AND CHIP-BREAKABILITY

摘要

PROBLEM TO BE SOLVED: To provide a steel for structural use combining excellent cold forgeability and chip-breakability.;SOLUTION: The steel for structural use having excellent cold forgeability and chip-breakability has a composition comprising, by mass, 0.1 to 1% C, 0.5 to 0.2% Si, 0.1 to 1% Mn, 0.03 to 0.1% S, ≤0.0005% Al, 0.001 to 0.01% Ti, 0.001 to 0.005% O and 0.01 to 0.05% N, and the balance Fe with inevitable impurities. Also, in the steel structure after cold forging, the number of sulfide-based inclusions 1 parted to ≥3 pieces to the cogging direction, and in which the respective length in the cogging direction is ≤20 μm covers ≥40% to the whole number of the sulfide-based inclusions in the polished face.;COPYRIGHT: (C)2006,JPO&NCIPI