Low yield ratio high tensile strength steel sheet excellent in weld heat affected zone toughness and method for producing the same

摘要

PROBLEM TO BE SOLVED: To provide a low yield ratio high tensile steel sheet excellent in heat affected zone toughness.;SOLUTION: There is provided the low yield ratio high tensile steel sheet excellent in heat affected zone toughness containing, by mass%, C:0.06 to 0.09%, Si:0.07% or less, Mn:1.0 to 1.6%, P:0.006% or less, S:0.003% or less, Mo:0.20 to 0.45%, Al:0.005 to 0.060%, Nb:0.005 to 0.030%, Ti:0.005 to 0.020%, further N:0.0020% to 0.0040%, Cu:0.05% or less, Ni:0.05% or less, B:0.0003% or less, having carbon equivalent Ceq of 0.40 to 0.47% and weld crack sensitivity Pcm of 0.21% or less, and containing the balance Fe with inevitable impurities.;COPYRIGHT: (C)2015,JPO&INPIT