| 摘要 |
A high-strength steel sheet which can exhibit excellent HIC resistance performance and fracture resistance performance even when the steel sheet is thick, has a chemical composition comprising, in mass%, 0.02-0.07% of C, 0.05-0.50% of Si, 1.10-1.60% of Mn, 0.015% or less of P, 0.0030% or less of S, 0.005-0.030% of Nb, 0.005-0.020% of Ti, 0.005-0.060% of Al, 0.0005-0.0060% of Ca, 0.0015-0.0070% of N, at least one element selected from Cu, Ni, Cr and Mo in the total amount of 0.1-1.5% exclusive and a remainder made up by Fe and impurities, has a steel texture composed of 10% by area or more of bainite and a remainder made up by ferrite and pearlite, and an Nb segregation degree of less than 1.6 and an Mn segregation degree of less than 1.4 as measured in a thick center part of the steel sheet. |
