Study on the welding joint microstructure and mechanical properties of 800 MPa grade high stress steel

The welding of 800 MPa grade high stress steel with good resistance to welding crack was carried out by SMAW and GMAW. The microstructure analysis and mechanical properties of the welded joint were finished. The results show that under the two welding methods, the weld structure is mainly covered with interwoven lath martensite and lath bainite, as well as a certain amount of acicular ferrite, between the lath is some residual austenite, and the oxidative inclusions were obviously found in SMAW weld Macroscopic metallographic; The welding joints obtained by the two welding methods have similar hardness distribution, the tensile strength is equivalent, and both are broken in the base material, but the side bending test pieces of SMAW appeared 0.5 mm cracking; The impact toughness of the SMAW joint is lower than that of the GMAW joint at −50 ℃. The SMAW fracture is composed of the quasi-dissociation of the facies and a small number of dimples, which belongs to the ductile-brittle fracture. And the GMAW fracture is composed of small and deep dimples, belonging to the typical ductile fracture.