Transient development of weld pool in Pulsed Current GTAW of Lap joint: The effect of the duty cycle

This study investigates the influence of the duty cycle, with two different torch angles, on the transient development of the weld pool during pulsed current gas tungsten arc welding (PC-GTAW) in lap joints of thin aluminum sheets. A numerical model was developed to accurately evaluate the heat flux, current density, and gas shear stress generated by the arc plasma. These parameters were then used in another model to forecast the weld pool geometry with three pulsed current duty cycles: 20%, 50%, and 80%. Analyses were conducted using torch angles of 20o and 45o. Torch angles significantly affected the arc and weld pool characteristics. Variation in heat flux distribution was observed with the 20° torch yielding higher heat flux on the horizontal surface compared to the vertical, whereas the 45° torch showed slightly high heat flux on the horizontal surface, contrary to symmetry expectations. Results indicate that welding with a 20° torch produced a deeper and wider weld compared to the 45° torch. The 20° torch produced full penetration under the direct current condition, whereas a 45° torch led to partial penetration and asymmetric pool formation due to the joint geometry. Duty cycle also affected the weld pool. At a 20% duty cycle, the weld pool got sufficient time to solidify during each pulse cycle, while at 80% duty cycle, a continuous liquid pool was maintained. Increasing the duty cycle from 20 to 80% developed larger pool sizes for both torch positions. The numerical model was validated with macrostructural images obtained from real experiments giving good agreement between the two. The findings highlight complex interactions between arc plasma dynamics, duty cycle ratios, and weld pool characteristics in PC-GTAW, offering insights for optimizing welding parameters to minimize distortion in thin aluminum sheets in future studies.