| 摘要 |
PROBLEM TO BE SOLVED: To provide a high impact resistant square steel pipe provided with material characteristics of higher strength and a lower yield ratio compared with the conventional one, and combining super-lightness in weight and high collision safety, and to provide a production method therefor. SOLUTION: A square steel pipe comprising 0.019 to 0.35% C, 0.1 to 0.3% Si, 1.0 to 1.6% Mn,≤0.025% P,≤0.02% S, 0.010 to 0.050% Al, 2 to 35 ppm B and 0.005 to 0.05% Ti as essential components is subjected to induction heating, and is subjected to water-cooled quenching at a cooling rate of≥100°C/s, so that the high impact resistant square steel pipe in which tensile strength TS is≥1,700 MPa, and a yield ratio YR as the ratio between 0.1% proof stress YS and the tensile strength TS, (YS/TS) is≤72% is obtained. COPYRIGHT: (C)2004,JPO&NCIPI
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