| 摘要 |
A thick-walled, high tensile strength steel plate with excellent low-temperature toughness of multilayer welds (CTOD characteristics and Charpy impact of weld bonds), and a manufacturing method thereof are provided. This high tensile strength plate has a component composition that contains C, Si, Mn, P, S, Al, Cu, Ni, Nb, Ti, N, O, etc., in specific amounts in mass%, wherein the Ceq, defined by formula (1), is 0.520% or less, the Ti/N ratio is 1.50-4.00, a parameter expression comprising specific elements is fulfilled in order to control the sulfide morphology and the degree of center segregation in the steel, the remainder comprises Fe and unavoidable impurities, and wherein the hardness of the center segregation area in the steel plate is specified. Ceq = [C] + [Mn]/6 + ([Cu]+[Ni])/15 + ([Cr]+[Mo]+[V])/5 ... (1) |
