HIGH-STRENGTH THICK STEEL PLATE FOR STRUCTURAL PURPOSE HAVING EXCELLENT BRITTLE CRACK PROPAGATION PR

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PROBLEM TO BE SOLVED : To provide a high-strength thick steel plate used for a large-sized structure, having excellent brittle crack propagation stopping properties, and having a plate thickness of >50 mm, and to provide its production method. SOLUTION : The high-strength thick steel plate has a texture where the (100) plane X-ray intensity ratio in the central part of the plate thickness is ≥2.0, and also, the (110) plane X-ray intensity ratio in the plate thickness 1/4 is ≥1.5, and has a steel composition comprising, by mass, 0.03 to 0.2% C, 0.03 to 0.5% Si, 0.5 to 2.0% Mn, 0.005 to 0.08% Al, ≤0.03% P, ≤0.01% S and ≤0.0050% N, and, if required, further comprising one or more selected from Ti, Nb, Cu, Ni, Cr, Mo, V, B, Ca and rare earth metals. The steel stock having the above composition is heated at 900 to 1, 200°C, is rolled at a cumulative draft of ≥30% at an Ar3 point or above in the central part of the plate thickness and at a cumulative draft of ≥30% in the temperature range of an Ar3 point or below to an Ar3 point-60°C or above, and is cooled to ≤600°C at a cooling rate of ≥2°C/s. COPYRIGHT : (C)2008, JPO&INPIT