| 摘要 |
PROBLEM TO BE SOLVED: To provide steel which suffers little deterioration in toughness even in superhigh heat input welding and can contribute to the reduction in the operation cost of welding structures. SOLUTION: The steel has a composition containing, by mass, 0.03 to 0.1% C, 0.01 to 0.5% Si, 0.5 to 2% Mn, >0.8 to 2% Cu, 0.005 to 0.025% Ti, 0.002 to 0.008% N, 0.002 to 0.05% sol.Al and <=0.0035% O (oxygen) and the balance Fe with impurities. The occupation ratio of a ferritic structure in the metallic structure is <=50%.
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