| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength steel plate having excellent material uniformity in the steel plate by reducing variation in hardness in the plate-thickness direction and the plate-width direction of the steel plate, and a method for producing the same. <P>SOLUTION: The high-strength and high-toughness thick steel plate contains, in mass%, 0.04-0.2% of C, 0.01-0.5% of Si, and 0.5-2.5% of Mn, with the balance comprising Fe and unavoidable impurities, wherein a chemical symbol for an element represents mass% of each element, and has carbon equivalent Ceq represented by formula (1) of 0.50 or less, wherein a metal structure is a structure comprising ferrite, bainite, and martensite, and the martensite in a surface layer part of the steel plate has a volume fraction of 15% or less, and variation in hardness in the plate-thickness direction is ΔHV of 50 or less in terms of Vickers hardness. <P>COPYRIGHT: (C)2013,JPO&INPIT |
