WELDED JOINT EXCELLENT IN FATIGUE STRENGTH, MAG WELDING METHOD FOR HOT ROLLED STEEL SHEET, MIG WELDING METHOD FOR HOT ROLLED STEEL SHEET, AND FLUX-CORED WIRE

摘要

PROBLEM TO BE SOLVED: To provide a welded joint which can actualize an excellent fatigue strength of 250 MPa or more, a MAG welding method for a hot rolled steel sheet, a MIG welding method for a hot rolled steel sheet, and a flux-cored wire for MIG welding.;SOLUTION: In a welded joint 1, a position where the hardness shows a minimum value is apart from a molten steel line 6 toward a base material 2 side by 0.3 mm or more, the ferrite fraction in the structure of the position is 50-90%, the remnant is martensite and/or bainite, in the ferrite, deposits whose grain size is 10 nm or less, and containing V, Ti and/or Nb are present at 10 piece/μm² or more, and the ferrite fraction in the structure of a welding metal 3 is 30% or less.;COPYRIGHT: (C)2014,JPO&INPIT