| 摘要 |
PROBLEM TO BE SOLVED: To provide high tensile strength steel for welding which has excellent toughness in an ultrahigh heat input, weld heat affected zone, and to provide a production method thereof. SOLUTION: The high tensile strength steel for welding having excellent toughness in an ultrahigh heat input, weld heat affected zone has a composition containing, by mass, 0.04 to 0.2% C, 0.02 to 0.4% Si, 0.6 to 2% Mn,≤0.02% P, 0.001 to 0.008% S, 0.0005 to 0.01% Al, 0.005 to 0.025% Ti, 0.0005 to 0.01% Ca, 0.0001 to 0.01% Mg, 0.002 to 0.008% N and 0.0005 to 0.008% O, and the balance Fe with inevitable impurities. The particles of TiN with a particle diameter of 0.01 to 0.5μm and including Mg-containing oxides are present by≥10,000 pieces/mm<SP>2</SP>, and the particles of Mn sulfide with a particle diameter of 0.1 to 10μm and including 1 to 49 atomic % Ca are contained by 10 to 400 pieces/mm<SP>2</SP>. COPYRIGHT: (C)2004,JPO
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