Microstructures and Properties of HR800CP Multiphase High Strength Steel Welded Joints

HR800 CP multiphase high strength steel was welded with laser welding and 80%Ar+20%CO₂gas-shield welding（MAG）with CHW-60 C welding wire.Microstructures and mechanical properties of the joints were studied.The result shows that,the microstructure of the weld center and the heat affected zone withlaser weldingare martensitic and bainite,the hardness of the weld center and the heat affected zone is higher than that of the base metal,there is no cracking along the weld seam while the bending degreeis 180°,the tensile strength of the joint is 799 MPa,which is lower than the base metal,because the pit on laser welding seam.For MAG welding,the microstructure of weld center are acicular ferrite and massive ferrite,while the coarse grain zone is comprised of lath martensitic and bainite.Bainite dominates the normalizing region,there is relatively soft area near the fusion line,and the tensile strength of the joint is 755 MPa,which is lower than the base metal too.