Comparison of Welding Residual Stresses of Hybrid Laser-Arc Welding and Submerged Arc Welding in Offshore Steel Structures

In the offshore industry, welding-induced distortion and tensile residual stresses have become a major concern in relation to the structural integrity of a welded structure. Particularly, the continuous increase in size of welded plates and joints needs special attention concerning welding induced residual stresses. These stresses have a negative impact on the integrity of the welded joint as they promote distortion, reduce fatigue life, and contribute to corrosion cracking and premature failure in the weld components. This paper deals with the influence and impact of welding method on the welding induced residual stresses. It is also investigated whether the assumption of residual stresses up to yield strength magnitude are present in welded structures as stated in the design guidelines. The fatigue strength for welded joints is based on this assumption. The two welding methods investigated are hybrid laser-arc welding (HLAW) and submerged arc welding (SAW). Both welding methods are applied for a full penetration butt-weld of 10 mm thick plates made of thermomechanically hot-rolled, low-carbon, fine-grain S355ML grade steel used in offshore steel structures. The welding residual stress state is investigated by means of computational welding mechanics, experiments, and in accordance with existing production procedures to determine the real distribution and magnitude of the residual stresses. The experimental validation of the FE simulations includes temperature and hole-drilling measurements.