Desenvolvimento e avaliação de um sistema para sincronização da alimentação de arame pulsada com a corrente de soldagem no processo TIG

Abstract

Pulsed (dynamic) wire feeding can modify the weld pool, metal transfer and heat input in arc welding processes. However, although some commercial solutions already exploit such technologies, they rely on proprietary feeders and/or torches. Furthermore, studies evaluating wire pulsation synchronized with the welding current remain scarce, which also motivated the development of this thesis. Thus, the objective of this work was to develop and evaluate a device compatible with conventional feeders and torches and with independent adjustment of frequency and amplitude for wire feed pulsation in the TIG process and to investigate the effects of synchronization between wire feed pulsation and current on the resulting deposits. The work methodology was organized into sequential stages. First, a pulsation device was built and characterized based on the cyclic deflection of part of the wire conduit. Next, a working envelope for the TIG process with pulsed wire feeding was established. Synchronization between wire pulsation and current was then implemented based on the electrode-to-wire voltage. The effects of wire pulsation parameters and current mode on bead geometry were subsequently evaluated. Finally, geometric, metallurgical, chemical, and thermal characteristics of the deposits produced. Characterization of the pulsation device demonstrated pulsation amplitudes of 2 to 15 mm at frequencies of up to 25 Hz, with tolerance for different wire materials and diameters. The pulsed feeding modified the bead geometry, being wire pulsation frequency the parameter with the greatest influence and wire stubbing (contact of the wire tip with the base metal at the bottom of the weld pool) the operational limiting factor at low current and high wire feed speed under constant current. The synchronization system achieved latency below 10 ms and enabled stable operation at boundaries previously unviable under constant current with pulsed feeding, thereby expanding the process working envelope. Under pulsed current synchronized with pulsed wire feeding, increasing frequency from 2 to 15 Hz reduced bead width approximately by 20%, penetration by 17%, and dilution by 20%. In the evaluation with the ER2594 wire, synchronization enabled an approximately 30% increase in wire feed speed compared with the limit achieved with constant current and pulsed feeding under an equivalent welding energy. Furthermore, synchronization yielded deposits with larger width and reinforcement, lower penetration and lower dilution, better preservation of Cr and Ni, with no relevant differences in hardness and ferrite/austenite balance. Thus, it is concluded that the developed device, combined with the synchronization strategy, can increase deposition capacity and improve deposit characteristics, opening up prospects for applications such as cladding and additive manufacturing, for instance.