Assessment of the impact of shielding gas flow rate on residual stresses in GMAW-deposited weld beads using LCR wave technique

Welding is a widely employed manufacturing process in the industry for permanently joining pieces. Particularly in fusion welding processes, the high temperatures generate residual stresses upon process completion, rendering the welded and thermally affected region highly susceptible to failures. This occurs because such residual stresses overlay externally applied stresses. Therefore, precise determination of residual stresses in the welded joint becomes fundamental to assessing the actual forces borne by the component and ensuring its operational safety, thus averting unforeseen failures. It is pertinent to point out that welding parameters influence not only the quality and properties of the weld beads but also the magnitude of residual stresses. Among the various process-influencing parameters, the shielding gas flow rate has received minimal attention in the literature, remaining unexplored in terms of its overall impact. To address this gap, this study evaluated the impact of shielding gas flow rate on residual stresses in AWS ER70S-6 weld beads deposited on DIN EN 10025-2 S275JR steel plates. The investigation utilized Gas Metal Arc Welding (GMAW) and the non-destructive ultrasonic method of Longitudinal Critically Refracted (L _CR ) waves for stress measurement. Weld beads were deposited via robotic operation, using shielding gas flow rates of 12, 15, and 20 l/min, while keeping other welding parameters constant. Longitudinal profiles of residual stress distribution were obtained for each specimen. The results revealed a significant impact of gas flow rate on the residual stress profile in the weld beads, with the highest values observed for the specimen welded with a gas flow rate of 15 l/min. This study strongly emphasizes the critical importance of evaluating the influence of operational parameters in the welding process on residual stresses in the welded joint, considering their significant impact on the structural integrity of the joined components.