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