STEEL PLATE HAVING EXCELLENT RESISTANCE TO FATIGUE CRACK GROWTH AND ITS MANUFACTURING METHOD

摘要

A good fatigue- and crack growth-resistant steel plate and manufacturing method therefor, wherein the components of the steel plate in weight percentage are: 0.040-0.070% of C, 0.40-0.70% of Si, 1.30-1.60% of Mn, less than or equal to 0.013% of P, less than or equal to 0.003% of S, less than or equal to 0.30% of Cu, less than or equal to 0.30% of Ni, less than or equal to 0.10% of Mo, 0.008-0.018% of Ti, 0.015-0.030% of Nb, less than or equal to 0.0040% of N, 0.0010-0.0040% of Ca, and the balance being Fe and inevitable impurities. By controlling [%C]×[%Si] between 0.022-0.042, {([%C]+3.33[%Nb])×[%Si]}×V cooling velocity/T cold shutdown between 1.15×10 -4~2.2×10 -3, carrying out a Ca treatment, and Ca/S = 1.0-3.0 and (%Ca)×(%S) 0.28=1.0×10 - 3, the TMCP process is optimized, such that the finished steel plate has a microscopic structure of a dual-phase structure of a ferrite + a uniformly and diffusely distributed bainite and the fatigue- and crack growth-resistance is improved.