HIGH TENSILE STEEL EXCELLENT IN TOUGHNESS OF WELDED ZONE AND OFFSHORE STRUCTURE

摘要

A high tensile steel, characterized in that it has a chemical composition, in mass %, that C: 0.01 to 0.10 %, Si: 0.5 % or less, Mn: 0.8 to 1.8 %, P: 0.020 % or less, S: 0.01 % or less, Cu: 0.8 to 1.5 %, Ni: 0.2 to 1.5 %, Al: 0.001 to 0.05 %, N: 0.0030 to 0.0080 %, O: 0.0005 to 0.0035 %, optionally one or two of Ti: 0.005 to 0.03 %, Nb: 0.003 to 0.03 % and Mo: 0.1 to 0.8 %, and the balance: Fe or impurities, with the proviso that N/Al is 0.3 to 3.0. The high tensile steel can be welded at a high heat input and also is excellent in the toughness at a low temperature.