Efeitos gerais da alimentação pulsada de arame no processo mig/mag com transferência metálica globular

Abstract

The use of pulsed wire feeding has been a field of innovation on both GTAW and GMAW processes. The commercially available equipment, in general, require specific feeders and/or torches to implement such technique. Besides that, a wide comprehension of the phenomena involved in pulsed wire feeding still lacks deeper investigation. In this context, the present work aims to evaluate the effects of pulsed wire feeding on GMAW with globular metal transfer in order to contribute to the scientific background for further development of innovative applications of such technique. Exploratory tests were carried out to assess the effects of pulsing frequency and amplitude on the electric signals. Posteriorly, an analysis of the droplet dynamics on metallic transfer was made through high speed filming for a variety of wire feeding pulsing frequencies and power source on constant current and constant voltage operation modes. Moreover, the geometric characteristics of the weld beads were measured from the transverse sections. It was verified that the mechanical pulse affects the process, the voltage and current oscillograms assume frequencies and amplitudes directly related to the pulse parameters. It was found that, in most cases, pulsation promotes the detachment of smaller and faster droplets, when compared to the conventional case. The pulse frequency of 16 Hz resulted in a more stable and regular transfer. Besides that, it tends to reduce bead width and concentrates the penetration on its center.