Metal transfer characteristics of aluminum alloy variable polarity high-frequency pulsed gas metal arc welding

The aluminum (Al) alloy variable polarity high-frequency pulsed gas metal arc welding (VPHFP-GMAW) method is developed to combine the advantages of VP welding and HFP welding. The effects of HFP frequency and amplitude on metal transfer are investigated using the droplet force model and high-speed camera images. The experimental results demonstrated that superimposing HFP current on VP pulsed current promoted droplet detachment. As the frequency and amplitude of the superimposed HFP current increase, the metal transfer type transitions from one-drop per pulse (ODPP) to two-drop per pulse (TDPP). When the transfer type remains unchanged, droplet detachment occurs earlier. Under the ODPP transfer type, the earliest detachment occurs within 1–2 ms after entering the electrode positive (EP) peak phase. Under the TDPP transfer type, the earliest detachment times are 1–2 ms and 10–11 ms. The detached droplets exhibit elliptical morphology. In addition, as the HFP frequency and amplitude increase, both minor and major axis lengths of the first droplet decrease, while the overall size of the second droplet increases.