| 摘要 |
<p>A high tensile strength steel sheet with excellent high speed weldability is provided to form beads with wide width even at a high arc welding speed of 100 cm/min or above. A steel sheet comprises, by mass percent, 0.20 to 2% of Si, and 1 to 2.5% of Mn, a total mass of Si and Mn being 1.5% or more, and further comprises 0.002% or less(exclusive of 0%) of O, 0.02 to 0.25% of C, 0.1% or less(exclusive of 0%) of P, 0.05% or less(exclusive of 0%) of S, 0.02 to 0.2% of Al, and 0.0015 to 0.015% of N. The steel sheet has an inner oxide layer with a thickness of 5 mum or thinner that exists in a surface layer thereof. The steel sheet further comprises at least one element selected from 0.03 to 2% of Cr, 0.03 to 1% of Mo, and 0.0003 to 0.005% of B. The steel sheet further comprises at least one element selected from 0.005 to 0.1% of Nb, 0.005 to 0.3% of Ti, 0.005 to 0.5% of V, and 0.005 to 0.5% of W. The steel sheet further comprises 0.03 to 0.5% of Cu. The steel sheet further comprises at least one of 0.0005 to 0.005% of Ca and 0.0005 to 0.005% of REM(rare earth elements). The steel sheet further comprises 0.0005 to 0.005% of Zr and Mg in total. The steel sheet further comprises 0.03 to 1% of Co. The steel sheet further comprises 0.015 to 0.5% of Ni.</p> |
