| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel for a welded structure having excellent weld zone CTOD (Crack Tip Opening Displacement) properties. SOLUTION: The steel for a welded structure has a chemical composition in which the parameter A defined by formula (1): A=Ceq+6Nb(mass%) satisfies≤0.355mass%, and, preferably has a componential composition comprising, by mass, 0.03 to 0.15% C,≤0.60% Si, 0.80 to 1.80% Mn,≤0.030% P,≤0.015% S, 0.01 to 0.08% Al, 0.004 to 0.03% Ti, 0.0036 to 0.0070% N, 0.0005 to 0.0030% Ca, and the balance Fe with inevitable impurities, and in which, the weld heat affected zone cooled at 800 to 500°C for a cooling time of≥250 s has a ferrite-pearlite structure free from pearlite bands and a bainite structure of≤5%; in the formula (1), Ceq=C+Si/24+Mn/6+Ni/40+Cr/5+Mo/4+V/14(mass%), and Nb, C, Si, Mn, Ni, Cr, Mo and V are mass% by the contents in the steel. COPYRIGHT: (C)2006,JPO&NCIPI
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