MANUFACTURE OF STEEL PRODUCT FOR WELDED STRUCTURE, HAVING EXCELLENT ATMOSPHERIC CORROSION RESISTANCE AND LOW YIELD RATIO

摘要

PROBLEM TO BE SOLVED: To provide the manufacture of a steel product for welded structure, having excellent atmospheric corrosion resistance and low yield ratio, which has high atmospheric corrosion resistance and weldability in an environment where 0.05 to 10 mdd salt comes flying and also has superior toughness and ≤80% yield ratio (yield point/tensile strength). ;SOLUTION: A steel, having a composition consisting of, by weight, 0.15% C, ≤0.7% Si, 0.2-1.5% Mn, 0.03-0.15% P, ≤0.02% S, 0.01-0.1% Al, ≤0.1% Cr, 0.4-4% Ni, ≤0.4% Cu, 0.1-1.5% Mo, and the balance Fe with inevitable impurities and satisfying inequality Pcm=C%+Si%/30+Mn%/20+Cu%/20+Ni%/60+ Cr%/20+Mo%/15+V%/10+5B%≤0.25%, is used. This steel is heated to 1050-1300°C and hot-rolled at ≥950°C at ≥40% draft. Successively, rolling is performed, and hot rolling is finished at 900-750°C followed by air cooling.;COPYRIGHT: (C)1999,JPO