Ultimate capacity of as-welded and post-weld treated ultra-high-strength steel fillet weld joints at room and arctic temperatures

Abstract Post-weld treatments (PWTs) are well known to improve the fatigue strength of weldments by reducing stress concentrations and introducing beneficial compressive residual stresses at the weld toes. In addition, alterations in material microstructure and surface quality caused by PWTs can affect fatigue properties in some cases. TIG dressing and HFMI treatment increased significantly fatigue strength whereas laser dressing featured only minor effects in present study. However, less attention has been given to investigating the effect of PWTs on the static strength of welded joints, especially at low temperatures and in structural steels, which are sensitive to heat-related workshop processes. In this study, experimental static tensile tests were performed at room (+ 20 °C) and arctic (− 40 °C) temperatures on as-welded, burr-ground, HFMI-treated, TIG-dressed, and laser-dressed non-load-carrying filled weld joints made of direct-quenched ultra-high-strength steel (UHSS). The results of the tensile tests and their accompanying digital image correlation measurements show that PWTs can have a noticeable effect on the load-carrying and deformation capacity of UHSS fillet weld joints, as well as at failure locations in weldments, depending on the alterations in joint geometry and microstructure caused by the applied PWT method. Furthermore, the behavior of as-welded and post-weld-treated UHSS fillet weld joints was similar at room and low ambient temperatures under quasi-static loading.