CMT + P welding behavior and AE characteristic frequency

To investigate the welding behavior of CMT + P, a PCI data acquisition card, a high-speed camera, an infrared imager, and an acoustic emission collector were used to synchronously monitor the welding process. It was observed that prior to the occurrence of pulsed spray transfer, there was a sudden increase in the welding machine's output current, accompanied by a violent arc light emitted from the tip of the welding wire. Subsequently, the molten droplet fell into the weld bead, increasing the temperature of the molten pool, the output welding current of the welder suddenly increase, the welding machine's output current simultaneously provided energy for the melting of the welding wire and its extension. When the tip of the welding wire made contact with the substrate, a short circuit was formed, resulting in a continuous decrease in the temperature of the molten pool. The AE signal was weak, accompanied by the explosive breakage of the molten droplet due to overheating and shrinkage, completing the short-circuit transfer of the molten droplet. After performing a DFT on the AE signals, process identification of various cycles and stages of CMT + P could be achieved through characteristic frequencies. The result showed that 575 kHz and 415 kHz could be used as characteristic frequencies for the pulsed arc cycle and CMT short-circuit cycle, respectively. It was inferred that 180 kHz was a unique frequency for the pulsed arc, while the frequency of 575 kHz was provided by the base arc, and the frequency at 415 kHz was generated during the instant of CMT short-circuit contact.