Influência da corrente, taxa de fusão e tempo de arco aberto na geração de fumos no processo GMAW curto-circuito

Abstract

When it comes to the generation and emission of welding fumes, much is already known about the influence exerted by the regulation parameters, such as welding current, voltage and shielding gas. It is known that, as a rule, the increase in welding current causes an increase in the fume generation rate (FGR). It was identified in the reviewed works the opportunity to advance in the elucidation of the root causes of the current effect on FGR. For that, the present work seeks to increase the understanding of this phenomenon. Therefore, a methodology was proposed through which it would be possible to decouple the influence of the welding current, itself, from the influence of the melting rate on the generation and emission of metallic fumes. It is known, however, that, in GMAW welding, there are obvious restrictions on changing the welding current without changing the melt rate, making necessary an approach that would allow the analysis of the isolated effects of these variables on the generation rate of fumes. With this work, the aim was to contribute to the understanding of the mechanisms of fume formation, establishing practical criteria to provide, eventually, the control, within achievable limits, of the fume generation through the manipulation of welding parameters. In this sense, fume collection tests were carried out under different welding conditions, varying the welding current, keeping the fusion rate constant, and vice versa, for three conditions of average open-arc (arcing) time. The addition of this last variable, allowed to analyze the influence of current and melting rate under different short-circuit transfer regimes. It is possible to admit that, within the appreciable limits of the input variables, the results showed that the welding current exerts a greater influence on the FGR than the melting rate. It is also observed that, in all conditions tested, among the investigated input variables, the average arcing time showed to have the most significant influence on FGR.