In this study, a 1400 MPa-grade ultra-high-strength steel thin-plate butt-welded joint was selected as the research object, and the joint was fabricated using the metal inert gas (MIG) welding process with ER307Si filler wire. Residual stress distributions were measured via the hole-drilling method, while micro-hardness was assessed using a micro-hardness tester. Simultaneously, both transverse shrinkage and angular distortion of the welded joint were experimentally determined. According to the hardness distribution of the joint, a thermal-metallurgical-mechanical finite element model was developed based on SYSWELD software platform. This model incorporates solid-state phase transformations (SSPT) and softening effect in the HAZ, as well as strain hardening and annealing behaviors in the weld metal. The temperature field, residual stress distribution, and welding deformation of single-pass butt-welded joint were simulated by the developed computational method. The simulation results were validated against experimental measurements, confirming the accuracy and reliability of the proposed computational approach. Furthermore, based on the numerical results, the influence mechanisms of SSPT and material softening on residual stress and deformation were analyzed. The findings indicate that SSPT exhibits considerable influences on the magnitude and distribution of welding residual stress. It reduces the peak longitudinal residual stress from 1620 MPa to 1350 MPa and increases the peak transverse residual stress from 350 MPa to 402 MPa. The results also manifest that the softening effect further reduces the peak longitudinal residual stress by 300 MPa, while exhibits minor effect on transverse residual stress. However, the results show that neither the SSPT nor the softening effect presents obvious affect on welding deformation.
Mao et al. (2026) studied this question.