| 摘要 |
PROBLEM TO BE SOLVED: To provide a non-tempered high tensile strength thick steel plate having a yield strength of ≥885 MPa, to which Ni and Mo are not added, whose alloy cost is low, and in which a tempering stage is omitted in an off line, and to provide a method for producing the same.SOLUTION: The thick steel plate is composed of a steel containing 0.08 to 0.11% C, 0.03 to 0.20% Si, 1.85 to 2.5% Mn, ≤0.012% P, ≤0.005% S, 0.003 to 0.05% Nb, 0.003 to 0.030% Ti, 0.0003 to 0.0030% B, 0.01 to 0.1% Al, ≤0.0050% N, and the balance Fe with inevitable impurities, and has a microstructure being a mixed structure composed of martensite and lower bainite, and in which the total area ratio of both the structures is ≥95%, and the steel plate is produced by regulating cooling conditions after hot rolling. |
