Resumo Atualmente, no cenário brasileiro de óleo e gás a execução dos processos de soldagem para aços inoxidáveis consiste em sua grande maioria de aplicações manuais, dificultando qualquer aumento de produtividade e repetibilidade dos processos. Portanto, a automação desta etapa permite grandes avanços com resultados mais confiáveis, menores custos relacionados à mão-de-obra e condições de saúde mais favoráveis para os soldadores. Com o objetivo de automatizar a soldagem GTAW em aplicações orbitais, testes experimentais foram realizados em tubos de aço inoxidável 304 L, posicionados na posição 5G de soldagem. As amostras foram soldadas pelo processo GTAW com alimentação dinâmica de arame, utilizando um manipulador robótico em 2 etapas de 180º na progressão vertical descendente. Os parâmetros de soldagem e a condição estável de soldagem obtidos foram discutidos e o comportamento da poça durante a soldagem do passe de raiz foi monitorado por videografia em HDR. Foi possível se alcançar alta velocidade de soldagem no passe de raiz, 50 cm/min com o modo keyhole. O movimento dinâmico do arame contribuiu para alcançar-se grande estabilidade do processo e robustez na soldagem de todos os passes, da raiz ao acabamento. As macrografias e ensaios de raio-x realizados na junta não indicaram a presença de descontinuidades como poros e falta de fusão.

Abstract Currently, in the Brazilian Oil and Gas scenario the execution of welding processes for stainless steel consists mostly of manual applications, rendering hard any increase in productivity and repeatability. Therefore, the automation of this step allows several advances such as more reliable results, lower costs and healthier condition for welders. With the aim of developing automation for GTAW welding of these applications, experimental tests were carried out in a 304L stainless steel pipe laid out at 5G position. The samples were orbitally welded by GTAW with dynamic wire feeding process, using a robotic manipulator in two steps of 180º in vertical down progression. The welding parameters and the stable condition obtained are discussed and the weld pool behavior during the root pass was online monitored by HDR (High Dynamic Range) videography. It was possible to reach high welding speed in the root pass, 50 cm/min in a keyhole mode. The wire dynamic movement contributed to reach great process stability and robustness for all joint passes, from root to finishing. The macrographs and x-ray analysis did not indicate discontinuities as porosity nor lack of fusion.

Abstract: The GTAW process is recognized as a process of high metallurgical quality, being widely used in the pipelines welding, mainly in the root pass. The relative independence between the heat delivered to the melting pool and the amount of material added helps to control the melting of the material and to avoid the appearance of welding discontinuities such as lack of fusion and lack ok penetration. When orbital welding is carried out, mainly in the overhead position, there is a tendency of electrode contamination by the melted wire, reducing process productivity and quality. In this scenario, there are some strands of the GTAW process that aim for increased productivity, reconciled with the already present high metallurgical quality. These includes low and high frequency dynamic wire feeding, preheating wire and tangential wire insertion. The present work deals with the contribution of the high frequency dynamic wire feeding for the increase of robustness in the GTAW process, evidencing through voltage monitoring and high speed filming the formation of regular and uniform drops for the process stability.