Influence of the Post-Weld Treatment Process on the Deformation and Stresses of Structural Steel T-Joints

This paper presents the results of research on the influence of the post-weld treatment process on deformation and residual stresses in structural steel welded joints. For this purpose, T-joints were welded with 135 (MAG) methods from the following five steel grades: S235JR, S355J2+N, S460NL, S690QL and S960QL, maintaining a similar linear energy of the welding process. The welded joints in the post-weld heat treatment (stress relieving annealing) and High-Frequency Mechanical Impact (HFMI) condition were then measured for flatness and straightness deviations of the sheets to determine the effect of the post-weld treatment on their deformation. Based on the results of laser tracker tests, it was confirmed that HFMI processing effectively reduces the level of deformation, achieving better results than traditional post-weld heat treatment (PWHT). In symmetry, to determine the effect of post-weld machining on the level and distribution of stresses, a three-dimensional numerical model was made, and a numerical analysis was performed using the FEM method for the selected material variant (S355). The results of the numerical analyses confirmed that HFMI reduces stress in welded joints, although it is less effective in this respect than heat treatment process used.