| 摘要 |
The steel plate of the invention is a high-tension steel plate that has a tensile strength of 1100 MPa or more and is excellent in base metal toughness and HAZ toughness and preferably in abrasion resistance. The steel plate satisfies a predetermined requirement of components in the steel. The Ceq (IIW) represented by the following equation ranges from 0.40 to 0.45 both inclusive: Ceq(IIW)=[C]+{⅙×[Mn]}+{⅕×([Cr]+[Mo]+[V])}+{ 1/15+([Cu]+[Ni])} in which each parenthesis-symbol [ ] means the content by percentage of an element in the parentheses. Oxide grains having a maximum diameter of 2 μm or less are present in a number density of 200/mm2 or more in the steel. The steel is composed of 29% or more by volume of martensite microstructure, and bainite microstructure as the balance. |
