Research On Arc Beheviour And Metal Transfer Of TIG-MIG Hybrid Arc Welding For Aluminum Alloy

TIG has a stable welding process, however low effic iency. As to MIG, although the welding efficiency is higher, apparent spatter, unstable arc and poor welding appearance usua lly exist during aluminum alloy welding. In order to solve these problems, TIG arc will be introduced to improve MIG welding process. In this paper, arc behavior and TIG- MIG hybrid welding, metal transfer and characteristics of weld appearance are mainly studied.TIG-MIG hybrid Welding test system was developed for the process. In this system,Mitsubishi FX-3U PLC works as controller core and the touch screen operates as man- machine interface, providing control signa l. In addition, a set of current switching circuit is designed, which can control the welding circuit of TIG and MIG or realize alternate work between them. Electric parameter acquisit ion system collected U-I data of the composite arc, while High- speed camera system recorded arc appearance and metal transfer process.The variation regularity of TIG arc voltage, MIG current and other electrical parameters were analyzed. The welding specifications of U-I characteristic curves and scatter diagrams were compared. The results show that,stability influencing law of MIG arc by TIG arc depends on droplet transfer mode. When the process of single MIG corresponds to short circuit transfer or globular transfer, added TIG arc can significantly reduce the electrical parameter fluctuations; when single MIG corresponds to spray transfer, it is difficult for TIG arc to improve MIG arc stability.The process of arc striking for MIG and TIG-MIG was compared. TIG-MIG hybrid welding has better stability because no short circuit occurs when arc striking. Mode, frequency of droplet transfer and droplet size can be changed by introducing TIG arc. TIG arc enables the droplet transfer to alter from short circuit transfer to meso-spray transfer or even globular transfer. When TIG DS RP, with the TIG current increasing, the droplet size decreases slight ly, the transition frequency increases and the droplet deviates from tungsten- side. When TIG DC SP, the rule is contrary.5A06 aluminum alloy plates surfacing experiments were carried out. In the experiment, wire feed speed and welding speed remains constant. The influence of TIG current, MIG weld voltage, TIG polarity and wire- tungsten distance on the weld bead appearance and cross section were studied. When TIG polarity is DC RP, cathode cleaning area behaves more than that of MIG and the weld surface of TIG-MIG appears denser and smoother if appropriate process parameters are selected. Excellent weld bead appearance can be obtained when wire-tungsten distance is between 5mm and 15 mm, provided that wire-tungsten distance matches with suitable tungsten height and shielding gas flow. When TIG polarity is DCSP, joint performance gradually deteriorated. Weld bead has a serious surface happens. Higher surplus height of seam and smaller width of bead happens due to TIG bypass.