Arc character and droplet transfer of pulsed ultrasonic wave-assisted GMAW

Pulsed ultrasonic wave is employed to interfere the GMAW process, and the new method is named as pulsed ultrasonic wave-assisted GMAW (PU-GMAW). A controllable periodic ultrasonic resonant field has been established in the arc space, and the periodic ultrasonic radiation force was used to improve the arc energy density and to promote the droplet transfer. It was found that compared with GMAW, under the action of 6 Hz pulsed ultrasound, the arc shape was changed to conical shape, and the arc length was compressed to 53%. The diameter of the droplet decreased from 1.83 mm of GMAW to 1.3 mm of 6 Hz PU-GMAW, and the droplet diameter reduced 29%. The retaining time of the droplet at the end of the wire decreased and the flying velocity increased obviously, which induced the transition frequency of 6 Hz PU-GMAW reach to 285 Hz and that is two times of conventional GMAW. The pulsed ultrasound also has deep influence on the weld formation. The aspect ratio of the welding seam increases from 0.19 (GMAW) to 0.27 (6 Hz PU-GMAW), and the increasing rate is up to 37%. It has been ascribed that under the action of the ultrasound, the arc energy density increased and the heat is easily to be transferred to the bottom of the molten pool.