Performing higher speeds with dynamic feeding gas tungsten arc welding (GTAW) for pipeline applications

Abstract

Most of pipeline welding still applies manual procedures, which increase production time and is stressful to the welding operator. This happens mainly due to the accurate melt pool control that hand operation enables. It yields high flexibility between material addition and heat source and is therefore adaptable to the welding condition and situation of each moment. This feature is not fully found when mechanized welding with automatic feeding is performed, despite every benefit of welding automation. This renders an optimized parameterization of a complex task. Automatic orbital welding is already a reality, though only applied in large scale in developed countries and/or by few expert companies from developed countries, due to such controllability, repeatability, and robustness difficulties. In this paper, a concept for dynamic wire feeding and respective implementation and analysis are presented. It consists of a low-frequency wire speed oscillation, aiming to decouple wire speed and arc power to a larger extent, which approaches to manual procedure as it guarantees user flexibility, but still keeping the benefits of welding automation. ASTM 139 Grade D tubes were welded under stable processing conditions. The macrographs did not indicate discontinuities such as porosity or lack of fusion, resulting in complete joint penetration. The average welding speed reached was 27.8 cm/min (10.9 in/min), much higher than that found by other authors.

Keyhole GTAW with Dynamic Wire Feeding Applied to Orbital Welding of 304L SS Pipes

“…According to Riffel [7], during the wire's forward movement, it runs through the electric arc's isotherms with higher speed, preventing the formation of large droplets in its tip, which generates a higher robustness for out of position welding. The same technique was applied by Silva et al [8] in a frequency of 1.25 Hz, the objective was joining high-strength steel pipes for the oil and gas industry, the author also showed the possibility of increasing productivity in root pass welding for an automated welding. Silwal and Santangelo [9] using frequencies around 16 Hz, reported a vibration in the filler metal that provided an extra force assisting in the transfer of the wire to the pool.…”

Implementation of a two-stage algorithm for NG-GMAW seam tracking and oscillation width adaptation in pipeline welding

“…In this regard, Zhou et al [7] introduced a laser vision tracking system in automatic pipeline welding. Silva et al [23,24] employed laser sensing techniques to control the trajectory of the welding torch during the root layer weld in pipeline welding, and achieved accurate results compared with the conventional manually controlled system. Studies show that the weld tracking accuracy and real-time performance based on vision sensors are prone to interferences originating from equipment (e.g.…”

On Orbital GTA Root-Pass Welding: Evaluation of AVC Performance, Bevel Geometry Influence and Wire Feed Technique

“…In pipeline construction the tube is fixed and a girth welding procedure is needed. In automated procedures, a robot manipulator moves the arc around the piece, similarly to an orbit, and, according to Silva et al [4], the molten pool behaves distinctly in each position. Silva et al [5] also elucidates that the greatest challenge in orbital welding concerns in keeping the molten pool stable in the different welding positions and, to achieve this, it is common to vary the welding parameters for each position.…”