Research On Arc Appearance And Droplet Transfer Of TIG-MIG Hybrid Welding

TIG welding has stable welding process and can get good weld bead surface, however it is low efficient. MIG welding is high efficient, but the welding process is unstable and its weld bead appearance is bad. Moreover, both TIG and MIG welding will bring weld bead defects such as undercutting and humping when the welding speed is too high, which seriously affect the weld bead quality. TIG-MIG hybrid welding can overcome these shortcomings and play their respective advantages, which is of great research significance. In this paper TIG-MIG hybrid arc is used in the high speed welding of low carbon steel, based on the electrical parameters-high speed photo collection system, TIG-MIG hybrid arc, droplet transfer and weld pool behavior are researched, which lay the foundation for the future theoretical research and engineering application.A TIG-MIG hybrid welding torch fixture is designed and made. High speed electrical parameter collection system is founded based on PCI data acquiration card and current-voltage sensor. A high speed photo acquisition system is built with high speed CMOS camera+filter+near-infrared diode lighting laser. Synchronous acquisition for electrical parameters and high speed photo is realized by software delay method.The characteristics of TIG arc, MIG arc and TIG-MIG hybrid arc are compared, and the variation regularity of TIG-MIG hybrid arc and wire-tungsten distance is analysed. The interaction between TIG arc current, TIG arc voltage, MIG arc current, MIG arc voltage, MIG arc length and wire-tungsten distance is studied. The changing of the current, voltage, arc length is explained by electron emission mechanism and constant wire-feeding GMAW arc length adjustment mechanism.By the analysis of droplet transfer mode and weld bead appearance, the choosing principle of parameters such as TIG arc current, MIG arc current, MIG arc voltage and the wire-tungsten distance for high speed TIG-MIG hybrid welding is determined, in addition, the cross section shape of bead-on-plate weld and butt weld of MIG welding and TIG-MIG hybrid welding are compared.Based on the characteristics of TIG-MIG hybrid arc, droplet transfer and weld pool flow behavior, humping and undercutting suppression mechanism of high speed TIG-MIG hybrid welding is researched, in addition, several humping forming conditions due to inappropriate parameters are studied.