Behavior of the plasma characteristic and droplet transfer in CO_2 laser-GMAW-P hybrid welding

摘要

The plasma behavior and metal transfer in CO_2 laser+GMAW-P hybrid welding have been investigated. A 650 nm laser, in conjunction with the shadow graph technique, is used to observe the metal transfer process. The effect of the mutual distance and laser power on the metal transfer has been discussed. The results indicate that the laser-induced plasma plume have a significant impact to the arc shape, resistance, electrode melting, droplet formation, detachment, and impingement onto the workpiece. The laser-induced plasma changes the conductive path and forces affecting on the droplet. High laser power and short distance between laser beam and arc (DLA) reduce the pulse base time (PB) of the voltage of phase, increase the droplet detachment time (PD) and the pulse current time (PP) of the voltage of phase, and it also lead to an upward and inward force near the bottom of the droplet. As a consequence, the droplet formation time is increased, and eventually an off-axis droplet phenomenon is deduced. The vapor jet force induced by the the keyhole plasma acts on the droplet as a retention force; this force decreases when the DLA becomes larger and increases when the laser power becomes higher. The observation may help in understanding the weld characteristics with respect to variation in mutual distance and laser power which may be beneficial in using the main process parameters to produce desired weld quality.