Arc characteristics of laser-TIG double-side welding

Based on the experiments of laser-TIG double-side welding (LTDSW) for aluminium alloys, the influence of laser radiation on the arc behaviours of the opposite side was investigated. Generally, with the variation of laser power, there are three typical arc shapes: arc column convergence, arc root constriction and arc expansion. An important point to notice is that the laser keyhole preheating will induce the arc column convergence in the LTDSW. The arc voltage in the LTDSW is lower than that in TIG welding over the entire range of the experimental currents. Moreover, with increasing welding current, the difference in arc voltage between TIG welding and LTDSW is diminished because of the self-stabilisation of the arc burning at high currents. The complex transformation of arc behaviours has a great effect on the arc current density and its stability. The laser generated hot spot or laser induced plasma will have a higher temperature and greater electron density than neighbouring regions, and will offer the line of least resistance or the lowest potential drop. Hence, it is very reasonable that the arc voltage should descend under the influence of laser radiation, and the arc electrons should compress and root to the hot spot or plasma zone.