| 摘要 |
A steel plate includes a predetermined chemical composition, in which B is controlled to be less than 0.0003 %, and the balance is Fe and incidental impurities. The steel plate also includes precipitates containing Ti, Nb, and Mo and having a mean particle size of 20 nm or less, the relationship [Nb]/([Ti] + [Nb] + [Mo] ‰¥ 0.3 being satisfied, where [Ti] is the Ti content, [Nb] is the Nb content, and [Mo] is the Mo content, thereby providing a thick, high tensile strength steel plate that is suitable for use in steel structures such as marine structures, ships, pressure vessels, and penstocks, has a yield stress (YS) of 460 MPa or greater, and has excellent low-temperature toughness of the heat-affected zone in a multilayer weld (CTOD property) and excellent strength and toughness after Post Weld Heat Treatment (PWHT property). |
