AC-GTAW of aluminium - new perspective for evaluation of role of positive polarity time

Abstract:
Experiments were carried out to determine the effect of the positive polarity time on cathodic cleaning, arc voltage, arc power and weld bead geometry on AC-GTAW of aluminium. Welding current was kept constant in both positive (EP) and negative polarity. During the experiments current and voltage monitoring was performed to further analysis of arc voltage and arc power. There was an increase in the weld depth and fusion areas when longer EP times were used. This behaviour differs from the traditional literature relating to welding processes with non-consumable electrodes. However, this increase occurs from a certain point, when the EP time is >4·0 ms over a total period of 20·0 ms. The use of a minimum EP time was found to be sufficient to perform the oxide removal, yielding weld beads with satisfactory fusion characteristics and minimum wear of the tungsten electrode.