| 摘要 |
PROBLEM TO BE SOLVED: To provide steel for welding structures which has excellent low temperature toughness in a welded joint by high heat input welding of >=400 kJ/cm such as electro-gas arc welding. SOLUTION: The steel has a composition containing, by mass, 0.04 to 0.12% C, 0.01 to 0.5% Si, 0.5 to 2% Mn, 0.04 to 0.08% sol.Al, 0.0005 to 0.003% B, 0.001 to 0.01% S, 0.04 to 0.08% sol.Al, 0.004 to 0.007% N and 0.001 to 0.005% O, and, if required, containing one or more kinds selected from the group consisting of Cu, Ni, Cr, Mo, V and Nb, and further containing Al2 O3 precipitates having a diameter of an equivalent circle of 0.5 to 3μm, and further satisfying 0.9×1.3B<=N<=1.2×1.3B; wherein B is contents (%).
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