HIGH TENSILE STEEL SHEET EXCELLENT IN GAS CUTTING CRACK RESISTANCE AND LARGE HEAT INPUT WELD ZONE TOUGHNESS

摘要

PROBLEM TO BE SOLVED: To provide a high tensile steel having sheet thickness of 50 mm or more and tensile strength of 780 MPa to 930 MPa, excellent in crack property during gas cutting and capable of handling high heat input welding.SOLUTION: There is provided a high tensile steel sheet excellent in crack resistance during gas cutting and toughness during large heat input welding and having tensile strength of 780 MPa, having a predetermined components and satisfying (1) formula in a range of 0.45% to 0.65% and (2) formula in the range of 1% to 2% at the same time. Ceq=C+Si/24+Mn/6+Ni/40+Cr/5+Mo/4+V/14 (1). (Cu+Ni)-(Cr+Mo+5*V+10*Nb) (2), where each element symbol expresses mass%.