| 摘要 |
PROBLEM TO BE SOLVED: To provide weld metal having sufficient fracture toughness although the hardness (Hv) of the weld metal in a welded joint is 220 or less, even in the welding of a steel plate which has high strength and is thicker than 50 mm. SOLUTION: A single-electrode or dual-electrode electrogas welding method which is excellent in brittle fracture initiation resistance characteristics of a weld zone. In the method, a steel material having a thickness of 50 to 80 mm and a yield strength of 470N/mm<SP>2</SP>or higher is subjected to vertical position welding by using a flux cored wire for the single electrode or either one of the dual-electrodes. The welding wire contains, as average chemical composition, by mass%, 0.01-0.10% C, 0.05-0.3% Ti, 0.01-0.03% B, and N limited to 0.01% or less, and further one or both of 0.05-0.25% Al and 0.05-0.30% Mg, 0.1-0.75% in total of slag former comprising one or more of CaF<SB>2</SB>, LiF, CaCO<SB>3</SB>and LiCO<SB>3</SB>, and the balance being Fe and unavoidable impurities. COPYRIGHT: (C)2006,JPO&NCIPI
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