| 摘要 |
Provided is a thick steel plate that, despite thickness of 100 mm or greater, has exceptional strength and toughness in the central thickness portion. The present invention is a thick steel plate having thickness of 100 mm or greater and yield strength of at least 620 MPa, characterized by containing prescribed amounts of C, Si, Mn, P, S, Cr, Ni, Al, N, B, and O, the remainder being Fe and unavoidable impurities; having a component composition the carbon equivalent CeqIIW of which is 0.65 or above; and having a structure in which the maximum value of prior ? grain size, expressed as equivalent circle diameter, in the central thickness portion is 150 µm or smaller, and the total area ratio of martensite and bainite in the central thickness portion is 80% or greater. |
