| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel sheet having excellent toughness in the welding heat affected zone even in the case of high heat input welding. SOLUTION: The steel sheet has a composition containing, by mass, 0.01 to 0.15% C, 0.05 to 0.80% Si, 0.5 to 2.0% Mn, 0.01 to 0.08% Al, 0.005 to 0.025% Ti and 0.0020 to 0.0070% N, in which the content of S is 0.0005 to 0.0050%, the content of O is 0.0005 to 0.0040%, and the content of rare earth elements is 0.0020 to 0.0150%, and also, the content of S [S], the content of O [O] and the content of rare earth elements [REM] satisfy 0.4<= [REM]-2.2×[O]}/[S]<=8.0, and the balance iron with inevitable impurities.
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