Effects of Filler Wire Intervention on Gas Tungsten Arc: Part II - Dynamic Behaviors of Liquid Droplets

In gas tungsten arc welding (GTAW), the filler wire increases the deposition efficiency and influences the welding stability. Its interactions with the gas tungsten arc (GTA) are significant to better understand the welding process and to monitor and control weld quality. In view of this, the first part of the work, Effects of Filler Wire Intervention on Gas Tungsten Arc: Part I — Mechanism, explained the interaction mechanisms between the filler wire and the gas tungsten arc based on the proposed arc-sensing method of detecting probe voltage (i.e., the voltage signal between the filler wire and the tungsten electrode/workpiece). In this second part of the work, experiments were designed to make the filler wire melt in different areas of the arc to study the dynamic behaviors of the droplet and its effect on the arc. Typical metal transfer modes are discussed, and droplet oscillation is geometrically characterized through image processing and then analyzed in the time domain and time-frequency domain. The results show that the liquid droplet affects the arc through its transfer to the weld pool, its oscillation, and occupying the arc space. Information about these dynamic behaviors can be easily reflected in the probe voltage, which would be a valuable signal to monitor the process stability in GTAW with filler wire. This work shows the potential of the proposed sensing method for monitoring and controlling weld quality in all welding positions, GTA-based additive manufacturing, etc.