HIGH TENSILE STRENGTH STEEL FOR WELDING EXCELLENT IN TOUGHNESS OF ULTRALARGE HEAT INPUT HEAT AFFECTED ZONE AND ITS PRODUCTION METHOD

摘要

PROBLEM TO BE SOLVED: To provide high tensile strength steel for welding having excellent HAZ(heat affected zone) toughness in ultralarge heat input welding such as electro-slag welding applied in the assembly of the box column of a multistory building.;SOLUTION: The high tensile strength steel for welding excellent in the toughness of the ultralarge heat input heat affected zone has a composition containing, by mass, 0.01 to 0.2% C, 0.02 to 0.15% Si, 0.6 to 2% Mn, ≤0.02% P, 0.002 to 0.008% S, 0.0005 to 0.02% Al, 0.005 to 0.025% Ti, 0.002 to 0.008% N, 0.0005 to 0.008% O and one or more kinds selected from Ca, Ba, Sr, La and Mg respectively by 0.0003 to 0.01%, and the balance Fe with inevitable impurities and contains Ti-containing oxides with a grain size of 0.1 to 5 μm containing 0.5 to 50 at.% Mn by 20 to 1,000 pieces/mm2.;COPYRIGHT: (C)2002,JPO