Dynamic molten pool behavior of pulsed gas tungsten arc welding with filler wire in horizontal position and its characterization based on arc voltage

Abstract

To explore the dynamic behavior of molten pool and to find the electric characteristic signals reflecting the weld penetration states and degree for the fixed-point wire-filled pulsed gas tungsten arc welding (GTAW-P) of thin pipes in 2G position, molten pool images from different directions and arc voltage were sensed. During a peak current period, critical penetration occurred, with the molten pool behavior that the topside molten pool height collapsed sharply and was approximately 0.5 mm, and then rose to approximately 1.5 mm during the next base current period. With the increase in backside molten pool width, the oscillation amplitude and frequency of topside molten pool during the base current period increased and decreased, respectively. The oscillation amplitude reached the maximum when over penetration occurred. Such molten pool behaviors could be extracted from the arc voltage signals. The change in average peak voltage (ΔU⁎) could reflect the occurrence of critical penetration. The average base voltage (Ub¯) and the fluctuation of base voltage (ΔUb) increased linearly with the increase in backside molten pool width, which are reliable characteristic signals for the weld penetration degree. The effects of wire filling and base current on the dynamic molten pool behavior and characteristic signals were investigated. Experimental results showed when the base current is 10 A ̶15 A, Ub¯ and ΔUb can effectively characterize the weld penetration degree.