HIGH TENSILE STRENGTH STEEL PLATE HAVING EXCELLENT BASE METAL TOUGHNESS AND HAZ TOUGHNESS

PROBLEM TO BE SOLVED: To provide a high tensile strength steel plate having excellent base metal toughness and HAZ toughness, and preferably having wear resistance as well even in the case of a high strength steel plate having a tensile strength of 1,100 MPa or higher.SOLUTION: The high tensile strength steel plate satisfies prescribed components in steel, in which Ceq(IIW) expressed by the following formula satisfies the range of 0.40 to 0.45, and oxides with the maximum diameter of 2 μm or lower are present by 200 pieces/mmor higher, and its structure includes a martensitic structure by 29 vol.% or higher, and the balance bainitic structure. Formula: Ceq(IIW)=[C]+{1/6×[Mn]}+{1/5×(Cr]+[Mo]+[V])}+{1/15×([Cu]+[Ni])}; in the formula, [] denotes the contents of the elements in the steel.