A lot of welding fumes are generated due to the evaporation of magnesium during welding aluminium alloys using Al–Mg welding wires. Fume formation is mainly evaluated by two methods. An average formation rate can be calculated by collecting the fumes formed during a constant welding period. The other one is carried out by observing the droplet with a high speed video. However, these two methods become invalid in quantitatively evaluating the evaporation rate of magnesium in peak or background period during pulsed metal inert gas arc welding. In this paper, a novel method was developed to evaluate the evaporation rate and flux of magnesium in the peak period. First, a robot welding system was used to produce a series of droplets by shutting down the peak current at different times in the peak period. Second, the magnesium contents of these droplets were analysed. Finally, the evaporation rate and flux of magnesium in the peak period were calculated.
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