Enhancement of fatigue performance of thin HSLA steel laser-welded butt joints

Abstract Welding thin sheets of high-strength steel presents significant challenges, especially due to the pronounced softening effect in the heat-affected zone, which can lead to a substantial reduction in the joint’s load-bearing capacity. While laser welding mitigates this issue, improper weld geometry can lead to a reduction in fatigue performance. Such geometric imperfections may arise from inadequate fixturing, poor edge preparation, or suboptimal alignment during the welding process. Therefore, this study investigates the potential for enhancing the fatigue performance of laser-welded butt joints in 3-mm-thick high-strength S960MC steel by applying laser dressing and filler metal. Fatigue testing revealed that all weld configurations, evaluated using the nominal stress approach, met the fatigue limits specified in design codes. Laser dressing demonstrated significant benefits, leading to a notable improvement in fatigue strength compared to the as-welded variant. In contrast, the configuration with filler metal showed no substantial enhancement. These findings underscore the potential of laser dressing as an effective technique for improving the fatigue performance of laser-welded joints in demanding applications.