STEEL HAVING EXCELLENT WELD HEAT AFFECTED ZONE TOUGHNESS, AND ITS PRODUCTION METHOD

PROBLEM TO BE SOLVED : To realize excellent HAZ (Heat Affected Zone) toughness even on high heat input welding of ≥200 kJ/cm. SOLUTION : The steel having excellent weld heat affected zone toughness contains, by mass, 0.03 to 0.18% C, 0.03 to 0.50% Si, 0.40 to 2.0% Mn, ≤0.02% P, 0.02 to 0.20% S, 0.005 to 0.070% Al, 0.005 to 0.030% Ti, 0.0005 to 0.0050% Ca and 0.0005 to 0.0070% N, and further contains one or two kinds of metals selected from 0.0005 to 0.0050% Mg, 0.0005 to 0.0050% rare earth metals, and the balance Fe with inevitable impurities. The steel also contains particles having a diameter of the equivalent circle of 0.005 to 2.0 μm and containing, by mass, 3 to 60% S by 5×103 to 1×106 pieces/mm2.