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

摘要

A steel plate having excellent resistance to fatigue crack growth and manufacturing method thereof, 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 rate /T cooling-stopping between 1.15×10 -4 ˆ¼2.2×10 -3 , carrying out a Ca treatment, and Ca/S = 1.0-3.0 and (%Ca)×(%S) 0.28‰¤1.0×10 -3 , the optimizing the TMCP process, the finished steel plate has a microstructure which a duplex-phase structure of ferrite + uniformly and dispersedly distributed bainite and has an improved resistance to fatigue crack growth.