Backward flowing molten metal in weld pool and its influence on humping bead in high-speed GMAW

The additional electromagnetic force generated by the interaction of external magnetic field and the welding current was applied to suppress the momentum of the backward flowing metal and to prevent the occurrence of humping bead in high speed gas metal arc welding. The vision-based observation was utilized to capture the images of the weld pool and the features of the backward flowing molten metal in the weld pool were extracted and compared under different welding speeds and excitation currents of the magnetic field. The velocity of the backward molten metal flow on the surface of the weld pool was calculated and analyzed by the combination of the visual observation and the tracer particle technique. It was found that the velocity of the backward flow metal are decreased and the humping was disappeared when the external magnetic field was applied.