Advances in the GTAW Process - Contribution of Dynamic Feeding in the Robustness of Welding Out-Of-Position

:: Artigo completo

The national energetic development is strongly linked to pipeline’s construction sites, which became strongly dependent of welding processes and its automation. For this purpose, is required research and development focusing in
new processes with higher robustness which ensure great quality to welding joints. One of the biggest problems on orbital welding applications is the variation on forces direction over the weld pool, which changes depending on welding
position. That is evidenced by the necessity to change welding parameters according to weld position, which requires great ability and control of the welder in mechanized welding process. That represents greater tendency to occur welding defects along the weld bead. So, this also involves a reduction in robustness and process repeatability. To this purpose, dynamic wire feeding appears in order to eliminate or mitigate the problems related to emergence of welding defects, leading to improvements like porosity reduction and great weld bead wettability. However, many hypotheses around dynamic wire feeding are commercial statements reported by manufacture companies, without a scientific study. These affirmatives make the process attractive for applications in pipeline orbital welding where applies alloys with difficult weldability. Nevertheless, researches are necessary about the real dynamic wire feeding performance. This work aims to compare the dynamic wire feeding with constant wire feeding, in a multi-pass application inside a groove with filler metal Inconel 625. Tests were carried out in some welding positions as overhead position, vertical ascendant and descendant, using dynamic and constant wire feedings. Through filming of the weld pool and metal transfer it was observed an increase in process robustness using dynamic wire feed, decreasing discontinuities along the weld bead and the risk of electrode contamination. This allowed the application of weld process at three positions using constant current without changes in welding parameters.

RIFFEL, K. C.; SILVA, R. G. N.; DIRENE FILHO, H.; SCHWEDERSKY, M. B.; SILVA, R. H. G.. Advances in the GTAW Process - Contribution of Dynamic Feeding in the Robustness of Welding Out-Of-Position. Brazilian Petroleum, Gas and Biofuels Institute - IBP. Rio Pipeline Conference & Exhibition, Rio de Janeiro, 2017.