HIGH-STRENGTH THICK STEEL PLATE HAVING EXCELLENT ARREST PROPERTY IN 45 DEGREE DIRECTION TO ROLLING DIRECTION AND METHOD FOR PRODUCING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a high-strength thick steel plate having excellent arrest properties in a 45° direction to the rolling direction.;SOLUTION: Disclosed is a high-strength thick steel plate having a chemical composition comprising 0.01 to 0.12% C, ≤0.50% Si, 0.4 to 2% Mn, ≤0.05% P, ≤0.008% S, 0.002 to 0.05% Al, ≤0.01% N and 0.003 to 0.1% Nb, and the balance Fe with impurities, which satisfies [C+(Mn/6)+(Cu/15)+(Ni/15)+(Cr/5)+(Mo/5)+(V/5)]: 0.32 to 0.40%, and, in the central part of the plate thickness, the fraction of a ferritic structure of ≥80% and effective crystal grain size of ≤25 μm are satisfied, and further, the arithmetic average value of the total of the X-ray intensity ratios of the (321) face, the (211) face and the (110) face in the 45° direction at the 1/4 position of the plate thickness and the total of the X-ray intensity ratios of the (321) face, the (211) face and the (110) face in the 45° direction at the central part of the plate thickness is ≤3.3; wherein, the effective crystal grains denote the crystal grains in the case the grain boundary having an orientation difference of ≥15° is defined as a crystal grain boundary using an EBSP (Electron Back Scattering Pattern) process.;COPYRIGHT: (C)2010,JPO&INPIT