It is low surrender which is superior in resistance weld crack Characteristic and welding thermal effect section tenacity difference in elevation tension thick steel sheet

摘要

PROBLEM TO BE SOLVED: To provide a low-yield ratio high-tensile strength thick steel plate having ≥440 MPa yield strength YS, ≥590 MPa tensile strength TS and ≤80% yield ratio YR which are suitable for building structures and having excellent weld crack resistance and weld heat-affected zone toughness in a super-large heat input welding part and a small heat input multi-pass welding part.;SOLUTION: The steel plate comprises, by mass, 0.07 to 0.09% C, 0.01 to 0.07% Si, 1.0 to 1.6% Mn, ≤0.009% P, 0.0008 to 0.0019% S, 0.20 to 0.60% Mo and 0.005 to 0.060% Al, has one or two or more compositions of 0.05 to 0.60% Cr, 0.005 to 0.030% Nb and 0.005 to 0.080% V and further has compositions of ≤0.0003% B, ≤0.0040% N and satisfying Ceq of 0.40 to 0.47 and Pcm of 0.21 or below.;COPYRIGHT: (C)2012,JPO&INPIT