Features of Mechanical Properties and Residual Stress Distribution in Butt Joint of HSB690-SM355 Dissimilar Steel

HSB690 steel is high-performance steel for bridges manufactured by POSCO of Korea through a thermo-mechanical controlled process (TMCP). However, the application of these high-performance steels to the entire structure is challenging in terms of cost. The combination of dissimilar steels can be a good alternative. Welding of HSB690 steel is mainly used for joining dissimilar steel materials. Residual stresses and deformations caused by welding affect the fatigue performance of the structure. In particular, tensile residual stress around welds significantly affects the fatigue and fracture behavior of dissimilar materials by increasing the mean stress. Bridge structures using HSB690 are gradually increasing, but the features of residual stress at the similar or dissimilar welded joint using HSB690 have not been reported. The physical and mechanical properties at each temperature are essential for residual stress analysis. However, the mechanical properties of HSB690 with temperature are not clear yet. Thus, before the residual stress analysis, the mechanical properties of HSB690 were determined by high-temperature tensile tests. Then, the three-dimensional (3D) thermal elastic–plastic finite element (FE) analysis was conducted to assess the residual stresses in the butt-welded member composed of SM355 and HSB690 steel. The residual stresses measured by the strain release method were compared for the precision of the analysis results. Moreover, residual stress analysis in welds composed of the same kind of steel materials was also performed for comparison. As a result of simulations and experimental measurements, in the member welded with dissimilar steels, the SM355 side showed almost similar residual stress distribution compared to corresponding similar steel welds, but the residual stress distribution in the HSB690 side was higher than that of the similar steel welds.