Effects of arc interaction on lack-of-fusion and porosity in tandem NG-GMAW of 5083 Al-Mg alloy

The tandem narrow-gap gas metal arc welding (NG-GMAW) is an advanced high efficient technology for joining thick section metals. However, the common defects such as lack-of-fusion (LOF) at groove sidewalls, porosity in weld bead are still hard to be avoided, especially for joining thick section of aluminum alloy. In this study, a pulsed tandem NG-GMAW process was applied to join thick 5083 Al-Mg alloy plates. The LOF and its formation mechanism at varied arc length were investigated by observing the tandem arc interaction behaviors with highspeed photography and by synchronized recording the corresponding welding signals. The results indicate, the arc heat distribution, which is likely influenced by the tandem arc arrangement, is a critical factor to the formation of LOF. However, a properly adjusted arc length can improve the arc interaction and the weld formation. Moreover, a proper arc interaction behavior can change the direction of arc force, which makes contribution to the stirring effect on molten pool. It is beneficial to reduce porosity. The oxygen enriched pores (pore-II) caused by short-circuiting transfer were found when arc length correction coefficient (ALCC) is 15, which needs to be avoided during the welding process.