Otimização do processo de soldagem robotizada tandem GMAW do aço ASTM A572 G50

Abstract

The tandem welding process employs double wire feed in a single torch, providing increased deposition rate and consequent reduction in process times. However, the process complexity increases because the correct combination of parameters is essential to avoid the occurrence of interference between the electric arcs and defects, such as inadequate geometry, accentuated base metal casting, which results in failures under service conditions. The understanding of the TANDEM process and the optimization of the cycle times are the motivations of this work, having as a proposal to analyze the presence of defects and the changes in the microstructure and the mechanical strength through the variation of the modes of metallic transfer, angulation of the welding torch and consequent heat input variation. For all parameter variations, ASTM A572 G50 structural steel test pieces welded with ER70S-6 welding wire have been fabricated using robotic welding stations from a Multinational Company. The volume of the weldments has been the same in all variations of parameters, allowing a comparative analysis of the quality of the joint and presence of defects. The probability of occurrence of defects has been analyzed by the high-frequency acquisition of the values of current, voltage and wire feed speed, while the penetration profile and the dimension of the heat affected zone have been examined through macrographs. The analysis of the microstructure of the molten and heat affected areas has been carried out using an optical microscope, while for the determination of the strength, Vickers micro hardness profiles have been obtained. After different test conditions, the best combination of parameters was found, where the master wire was parameterized in continuous current and the slave wire with pulsed metallic transfer, obtaining a 19,3% higher displacement speed of the robot and no occurrence of anomalies in electrical arcs.