This study aims to investigate the complex welding residual stress of high-strength steel thick plate with multi-pass welding, and examines the influence of such stress on the fracture behavior of welded joints.

Taking 75 mm thick Q690 high-strength steel thick plate as the research object, multi-pass butt welding and a corresponding welding experiment are carried out, and the longitudinal residual stress on the middle cross section is then measured by the contour method after cooling. Based on effective thermal elastic-plastic FE computation, properties such as the thermal cycle and microstructure evolution during the multi-pass welding of thick steel plate are represented. The uniaxial tension test and GTN damage model are combined to obtain the parameters of GTN model for Q690 high-strength steel plate, which are then used to examine the fracture behavior and stress-strain curves of the base metal and welded joint specimens.

The predicted shape of the weld pool and the content of the metallographic phase show good agreement with the measured data. After considering the solid phase transformation during welding and initial stress due to rolling, the longitudinal and transverse residual stresses are in good agreement with the measured results. Moreover, the fracture behavior of the welded joints is also investigated while considering welding micro defects and transverse residual stress, and the mechanical mechanism of welding residual stress is clarified.

The results of this study can provide valuable references for the evaluation of the residual stress and fracture behavior of welded joints in high-strength steel thick plate .