Abstract: The variation in arc behavior, stability and control of droplet transfer in ACPMIG welding were studied by data acquisition system and high speed video photography system. The research reveals that the arc in EN polarity moves around the droplet and climbs up to the wire end, as a result of this behavior the wire melting rate increases, while in EP polarity the shape of arc is a typical “bell jar” and its size and brightness become the largest during the pulse stage. The droplet grows rapidly in EN stage and transfers in falling stage of EP. The alternative transformation between EN polarity and EP polarity is beneficial to the reduction in both plasma arc flow power and welding pool arc force. By controlling the EN ratio, a rapidly wire melting rate and shallow penetration appear; by controlling the pulse stage current and time, a stable one pulse one drop transfer process forms.

Key words: alternative current pulse metal inert gas(MIG) welding, electrical current and voltage, arc behavior, droplet transfer