Avaliação das potencialidades da soldagem TIG com alta corrente aplicada em união de chapas sobrepostas

Abstract

The necessity of enhancing productivity safely, ensuring quality, lower environmental impacts and costs creates the need towards new studies to be conducted and contributes to improving processes of welding. The crescent lack of qualified labor is an important factor to justify the development of automation. The TIG welding of high current without additional materials is presented as a technique of high potential to meet these requirements. However, it hasn't been totally spread over the industrial sector. Therefore, the aim of this research is to evaluate potentials and limitations of this technique in order to join overlapping plates. To that extent, it was initially carried out a study to evaluate the capacity of enhancing penetration of TIG process by the usage of high current considering the effect of the current level, welding speed, pulsating current usage, and the presence of hydrogen as a shielding gas. In this stage, a methodology was also used to separate the active and non-active energy forms on the determination of welding potentials for different parametric combinations when using current pulsed, as well as analyzing the weight of plots in the melted area. Secondly, it was studied the effect of electrode refrigeration on TIG arc constriction through the manufacture of an especial torch. Lastly, it was conducted a parameterization study of TIG welding under high current on horizontal fillet welding of thin overlapping plates. It was noticed an increase of penetration capacity with the application of the current pulse. Although a relation was found between pulse and the decrease of active power rating attributed to impedance, it was not possible to evidence the effect of this factor over the transference of heat to a plate. The usage of more forced refrigeration on the electrode showed to be able to concentrate the arc and increase penetration although it was not in a significant form. It was possible to raise the operational band of welding speed at a rate of 70% when working with mixtures of air and H2 instead of the pure air protection, maintaining the same union geometry and torch positioning. The proposal of a particular torch positioning in consideration of fillet welding has shown to be effective and, at the same time, tolerable to some variation of the torch angle. Hence, it was accomplished welding speed up to 60 cm/min for (2+2 mm) and (3+3 mm) overlapped joints welding.