| 摘要 |
PROBLEM TO BE SOLVED: To provide a welded joint combining excellent corrosion resistance and high weld zone fatigue strength to steel structures including bridges and steel towers in coastal areas and areas in which salt damage such as the scattering of snow melting salt is feared. SOLUTION: A steel having a compsn. contg., by weight, 0.02 to 0.20% C, 0.1 to <1.6% Si, 0.3 to 2.0% Mn, 0.3 to 1.5% Cu, 1.0 to 5.5% Ni, >0.03 to 0.20% Ti, 0.005 to 0.070% Al and 0.002 to 0.01% N, satisfying 0.30<=Ceq(%)<=0.65 [where, Ceq(%)=C+Mn/6+(Cu+Ni)/15+(Mo+V)/5+Nb/3], and the balance Fe with inevitable impurities, and, in which, among the inevitable impurities, the content of P is adjusted to <=0.030%, S to <=0.01% and Cr to <=0.1% is used as a base material, and the bainitic fractional ratio in the weld heat- affected structure is >=60%.
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