WELDABLE STRUCTURAL STEEL

摘要

The invention discloses a weldable structural steel having good toughness in the weld heat affected zone and good resistance to weld cracking which consists of 0.05 - 0.08% of C, 0.01 - 0.50% of Si, 1.20 - 2.50% of Mn, 0.005 - 0.07% of Nb, 0.005 - 0.030% of Ti, 0.005 - 0.06% of A? and the balance of iron and inevitable impurities whereby C(%) + 10N(%) is not greater than 0.12% and Nb(%) x ¢C(%) + 10N(%)! is not greater than 4x10-3 so that the quantity of the martensite island formed in the weld heat affected zone is restricted to not greater than 15% in terms of the area ratio. The weldable structural steel according to the present invention does not cause brittlement of the weld heat affected zone and exhibits excellent notch toughness at low temperatures even when having been welded with a large welding heat input.