Correlation analysis of current, molten pool, and weld formation in double-pulsed variable polarity TIG welding

Double pulsed variable polarity tungsten inert gas (DP-VPTIG) welding is an emerging high-efficiency technology for joining medium-thick aluminum alloys . Elucidating the interrelationships among current parameters, molten pool dynamic morphology, and weld formation is critical to welding process optimization and online control. Herein, an orthogonal welding experiment was conducted using key welding current parameters as design variables. Dynamic morphological features of molten pool were quantitatively extracted by a proposed image processing method . The response models among current parameters, molten pool morphology, and weld formation were established and analyzed based on Gaussian process regression. Obtained results reveal that there is a significant positive impact of arc energy on keyhole depth. Furthermore, a strong linear relationship between keyhole depth and penetration degree was observed. With the increasing keyhole depth, the weld penetration degree increases. While the correlation between the width of molten pool and penetration degree is insignificant. There is a minimum keyhole depth that ensures efficient transfer of arc heat into the bottom of molten pool, and thus enables deep penetration welding. This work provides theoretical foundations for the optimization and online control of DP-VPTIG welding processes. • Extracting precisely the dynamic morphology of the molten pool and keyhole features • Quantifying the relationship among current parameters, molten pool morphology and weld profile • There exists a critical keyhole depth ensuring the deep penetration welding