| 摘要 |
Proposed are a high-tensile strength steel that is excellent in strength and toughness of the base material and also excellent in toughness of the weld heated zone, even if the steel has a large thick, and a method of advantageously manufacturing the steel. Specifically, the high-tensile strength steel has a component composition including, in mass%, C: 0.03 to 0.10%, Si: 0.30% or less, Mn: 1.60 to 2.30%, P: 0.015% or less, S: 0.005% or less, Al: 0.005 to 0.06%, Nb: 0.004 to 0.05%, Ti: 0.005 to 0.02%, N: 0.001 to 0.005%, Ca: 0.0005 to 0.003%, and the balance of Fe and inevitable impurities so that Ca, S, and O satisfy the following expression (1): 0 < Ca - 0.18 + 130 × Ca × 0 / 1.25 / S < 1
wherein, Ca, S, and O represent the respective contents (mass%) of the elements. |
