PROBLEM TO BE SOLVED: To provide a high strength and high toughness steel sheet excellent in weldability even in the case Ti is added more largely than the addition amount of Ti allowable in the ordinary rolling condition and to provide a method for efficiently producing the same steel sheet.;SOLUTION: This high strength and high toughness steel sheet excellent in weldability has a composition satisfying, by mass, 0.01 to 0.15% C, 0.03 to 0.2% Ti, 0.8 to 3.0% Mn and ≤0.6% Si, and in which Ti-containing carbide and/or Ti-containing carbonitride with a particle size of 7 to 50 nm is present by ≥0.1 piece on the average per the area μm2 to be inspected. Further, the addition of prescribed amounts of B, Cu, Ni, Cr, Al, Ca, rare earth metals, Mo, Nb, V, Zr or the like is also effective. Moreover, in the production, rolling reduction of ≥60% is performed in an unrecrystallized γ region.;COPYRIGHT: (C)2001,JPO
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