Real Time Monitoring of Cold Metal Transfer (CMT) Welding Process

International audienceThe CMT welding process was investigated in this work. The transfer of Al-4043filler metal during welding was visualized using a high-speed camera with a greenlaser as an illumination source. Three phases were identified during the transfercycle. A hot phase during which a molten droplet is formed on the end of the wireelectrode under a high current. A cold phase corresponds to the move of the wiretoward the weld pool. The contact between the droplet and the weld pool createsa short circuit during which the material transfer is initiated and the arcing currentreduced. After a set time (in the middle of the short circuit phase), the wire isretracted mechanically to contribute to the droplet detachment without increasingin current welding. The effect of the current waveform on the metal transfer isinvestigated too. The reduction in the hot phase duration of the current waveformdecreases the volume of liquid drops at the wire tip and allows to increase theshort-circuit frequency, inducing a similar or higher deposit rate