Microstructure and residual stress deformation of FAB submerged arc welding joints of high-strength steel sheets for ships

The finite element software was used to simulate the FAB submerged arc welding process of high strength steel sheets. The macroscopic test, metallographic examination, hardness test and X-ray residual stress test were carried out on the welded joints of the test plate. The results show that the FAB submerged arc welding simulation specimen showed the phenomenon of central concave and transverse shrinkage, and the maximum concave and shrinkage were 0.61 mm and 0.52 mm, respectively. The macroscopic forming of the welded joint was good. The width of the coarse grain zone on the surface was about 1 mm, and the grain size of the microstructure was increased. The width of the fine grain zone and the incomplete recrystallization zone was about 1.5 mm, which was mainly composed of fine ferrite and pearlite banded structure. The dislocation density of the structure decreased and the hardness decreased slightly. The distribution characteristics of welding residual stress showed that there was a large tensile stress in the central area of the weld, and its value decreased along both sides of the weld, while the heat affected zone was dominated by compressive stress. The maximum tensile stress in the weld zone reached 187 MPa, while the maximum compressive stress in the heat affected zone was −180 MPa, both of which were significantly lower than the yield strength limit of the material.