Secondary arc striking during short circuit transfer of GMAW

Short circuit transfer process of conventional GMAW is generally believed that only the first arc striking is formed. However, a new phenomenon was found that the secondary arc striking occurred at the short circuit transfer, but not only the first arc striking, by observing the high-speed photographic images in the GMAW process. The results showed that when the droplet necking was broken, the high-temperature metal vapor with a certain concentration was formed between the end of the wire and the dropped droplet, which led to a transient arc burning. This arc along with the melting droplet gradually dropped and then disappeared in the melting zone, while the protecting gas acted as the medium and then the secondary arc striking happened. This arc striking was the arc striking stage during the conventional short-circuiting transfer process. The current waveform showed that two short circuit current waveforms appeared in the vicinity of the melt necking. The first waveform was the conventional short circuit peak current, while the secondary waveform was caused by the temporary arc-striking induced by the metal vapor.