Navigating Weld Sequencing: Effects on Distortion, Residual Stress Distribution, and Microstructural Evolution

This study employs high-fidelity thermo-metallurgical-mechanical simulations to examine the impact of weld sequencing on distortion, residual stresses, and post-weld microstructure in a two-pass single-stiffener T-joint weldment. Four welding sequences were investigated—sequential and tandem (twin torch) welding, both with and without interpass temperature control. The simulations, validated against experimental data, reveal that sequential welding with interpass control produces the highest angular distortion, while single-direction tandem welding results in the lowest. However, a simplified fatigue endurance analysis, incorporating a postulated surface crack, shows that the sequence with the least distortion (tandem welding) yields the shortest fatigue life, while the most distorted weldment (sequential welding) offers the best fatigue performance. This trade-off is driven by the role of solid-state phase transformations (SSPTs), where higher-temperature transformations such as austenite-to-ferrite help reduce distortion, while lower-temperature transformations like austenite-to-bainite or austenite-to-martensite are more effective in reducing residual stresses. These findings highlight the need to balance competing objectives—such as minimising manufacturing distortion and managing residual stresses to enhance structural integrity—when optimising weld sequencing strategies for complex welded assemblies.