Effect of Tool Rotational and Welding Speed on Transient Temperature in underwater and Normal Friction Stir Welding using Finite Element Method

Friction Stir Welding is an appropriate method to connect different metals in temperatures below their melting point. In spite of this, the effect of thermal cycles causes the reduction in mechanical strength in different weldment regions. On the other hand, because of necessity of doing welding in submerged conditions like in navy industries it is of great importance to investigate and thermally modeling the submerged Friction Stir Welding. In this paper, finite element modeling of friction stir welding in the air and underwater were performed for Al6061-T6 alloys to control the thermal cycles. In addition to cooling effect, the influence of parameters such as welding speed and rotational speed on the maximum temperature in workpiece was investigated. The model results were then examined by experimental data and a reasonable agreement was observed. Results show that increasing rotational tool speed due to increasing in generating heat flux causes increasing in maximum temperature experienced by workpiece in different regions in both air and underwater welding. However, in underwater welding because of boiling water surrounding the tool, temperature drop is more greater than another one. The difference between maximum temperature in air and underwater welding is high. Reducing welding speed causes increasing the maximum temperature. This is due to reducing cumulative generated heat flux during welding. Increasing temperature during welding in air is more salient than doing welding in underwater. In the other word the effect of welding speed on maximum temperature in welding in air is more than underwater welding.