Uma contribuição ao conhecimento da física do arco aplicada em soldagem

Abstract

With knowledge of the manufacturing process it is possible to improve their development in a faster and more efficient way. This is also applicable to welding. However, the physics that are involved in welding processes are not well known, because of the difficulty to study them experimentally and by the complexity and interdependence with different factors. Thus, the objective of this work is to investigate some physical phenomena relevant to the welding arc, in order to improve the understanding of fundamentals in this area and to provide conditions for improvement and development of welding processes. Specifically, the effects of the arc heat exchange with the environment, the interaction between hybrid concentric arcs and arc-anode coupling were studied. The observations of these effects in the arc were performed by visual analysis and by its voltage, using the current as the input to the system. In the studies of the effects of the arc heat exchange with the environment was used a pulsed TIG arc in a quasi-adiabatic container and its voltage were compare the voltage a pulsed TIG arc in an open environment, with it was possible to verify that an open arc needs more energy. For the studies of the hybrids arc were used a special torch containing concentric electrodes, with it was possible to create an arc within another and each arc with independent setup, verified that in concentric arcs, although visually could be seen two arcs, them voltage behaves as they were a single one because by changing the energy of one arc leads to a transient interference on both arcs energy before reaching a steady state. In the studies of the arc-anode coupling, was compared a TIG welding conditions on refractory anode (graphite) and non-refractory anode (copper and steel) with both refrigerated. The result shows that metal vapors from non-refractory anode modify the arc-anode coupling and in the non-refractory anode appear several metal vapor generators for arc-anode coupling instead of single area as happens in the refractory anode.