Studies on Backward Median Current Waveform Control Research in Pulsed MIG Welding

The one-droplet-per-pulse transfer is widely considered to ensure the stability of the welding process in pulsed MIG welding; a peak pulse followed by a median pulse in a square wave pulse can effectively enhance droplet transfer controllability and improve weld appearance. The instantaneous current and voltage waveforms, the probability density distributions of current and voltage, and U-I graphs collected by the waveform wavelet analyzer were used to assess the welding quality and weld bead appearance. The 1.2-mm carbon steel welding wire experiments showed that under the same conditions, using a median waveform could significantly improve the welding quality. If the median current was too small or too large, the influence on the welding process was not obvious, and was only representing an increase of the base current or peak current phase. If the median time was too short, the energy accumulated was not enough to control the droplet transfer; conversely, too much median time led to globular droplet transfer. With a backward median current range of 180A-225A and duration range of 8ms-12ms, all experiments resulted in a nice weld effect.