The Research Of Alternative Current Pulse Gas Metal Arc Welding Technology In Aluminum Alloys

The alternative current pulse gas arc metal welding (AC-P-MIG) will be more and more applied in lightweight aluminum alloy welding in automobile industry, because of its low welding heat input and high wire melting rate which can solve the burn through problem in sheet plate welding and improve the welding efficiency. This article made a research in the arc behavior and droplet transfer in aluminum alloy AC Pulse MIG welding by the high-speed video photography system and synchronous data acquisition system based on Lab View; established a droplet heat balance model to study the wire melting rate and droplet temperature; we also did some experiments in the 0.5 to 3 millimeter aluminum lap-joint welding to study the appearance of weld.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 the EP polarity the shape of the arc is a typical "bell jar" and its size and brightness becomes the largest during the pulse stage. The droplet grows rapidly in EN stage and transfers in a falling stage of EP. By controlling the pulse stage current and time, a stable one pulse one drop transfer process forms.The research calculated the electrode arc heat and resistant heat coefficients based on the wire melting rate mathematical model which established by the droplet heat balance model. Through the experiment data fitting method, we also calculated the electrode arc heat and resistant heat coefficients. We deduced and calculated the droplet heat content and temperature, and made a discussion in the factors which will affect the AC Pulse MIG wire melting rate. The research shows:the electrode arc heat and resistant heat coefficients have a good matching relationship between the calculated and fitted value; when at a constant welding current, the wire melting rate in AC Pulse MIG welding is higher that the DC Pulse MIG welding, and with the EN% increasing, the AC Pulse MIG wire melting rate increases; while under the same welding wire, the droplet heat content and temperature values in DC-P-MIG welding are higher than the values in AC Pulse MIG welding, and as the EN% increased, the droplet heat content and temperature values decrease in AC Pulse MIG welding; the AC Pulse MIG wire melting rate is influenced by the cathode & anode voltage drops and arc behavior in EN/EP polarity. The appearance of weld in the AC Pulse MIG welding in aluminum alloys sheet research shows:when at a constant wire feed speed and welding speed, the penetration depth and bead width decrease while the reinforcement becomes high as the EN% increase; accordingly, the AC Pulse MIG welding technology can solve the burn through problem in welding thin sheet joints and can improve the gap bridging ability in lap joints; what's more, the technology can also improve the welding speed and welding bead quality; the black smoke in aluminum alloy welding is affected by the wire types and welding methods, the AC Pulse MIG welding technology combined with the aluminum welding wire can dramatically reduce the production of black smoke after welding.