Patent ID: 8920713

Claim:
A steel for a welded structure, comprising the following composition: by mass %, C at a C content [C] of 0.010 to 0.065%; Si at a Si content [Si] of 0.05 to 0.20%; Mn at a Mn content [Mn] of 1.52 to 2.70%; Ni at a Ni content [Ni] of 0.69% to 1.50%; Ti at a Ti content [Ti] of 0.005 to 0.015%; O at an O content [O] of 0.0010 to 0.0045%; N at a N content [N] of 0.002 to 0.006%; Mg at a Mg content [Mg] of 0.0003 to 0.003%; Ca at a Ca content [Ca] of 0.0003 to 0.003%; and a balance of Fe and unavoidable impurities, wherein, a P content [P] is limited to 0.008% or less, a S content [S] is limited to 0.005% or less, an Al content [Al] is limited to 0.004% or less, a Nb content [Nb] is limited to 0.001% or less, a Cu content [Cu] is limited to 0.03% or less, a V content [V] is limited to 0.020% or less, a Mo content [Mo] is limited to 0.05% or less, and when a steel component parameter P CTOD is defined by a following equation (1), P CTOD =[C]+[V]/3+[Cu]/22+[Ni]/67 and a steel component hardness parameter CeqH is defined by a following equation (2), CeqH=[C]+[Si]/4.16+[Mn]/14.9+[Cu]/12.9+[Ni]/105+1.12[Nb]+[V]/1.82 the P CTOD is 0.065% or less, and the CeqH is 0.196% or less.