Constrição e expansão eletromagnética do arco elétrico no processo GTAW aplicada na manufatura aditiva

Abstract

The wire arc additive manufacturing process uses metallic materials to deposit the layers through melting and solidification, and that have proved to be an attractive manufacturing process for medium and large parts due to the high deposition rate and potentially unlimited building size. Among the available heat sources is the GTAW process, where the heat source comes from the electric arc. With reference to the electric arc axis without movement, the longitudinal section is bell-shaped and the cross section is circular. In this research, an electromagnetic device was developed that performs the simultaneous arc' constriction and expansion and was able to change the electric arc cross section from circular to elliptical, and the greater the coil excitation current, the greater the ellipse elongation effect. The device makes it possible to reorient the ellipse and shift it by 90° electrically, without mechanical movement or reassembly, just by inverting the supply to the coils. The electric arc shape was recorded and the geometry of the bead on plate was analyzed, which proved that the change in electric arc shape was reflected in the geometry of the weld bead. When placing the longest length of the ellipse parallel to the welding direction, the greater the penetration and the smaller the width of the weld bead. When placing the longest length of the ellipse perpendicular to the welding direction, the lower the penetration and the greater the width of the bead. The increase in the coil excitation current results in a decrease in the electric arc area, making it possible to increase the current density and increase the heat intensity. This electromagnetic device was applied in additive manufacturing, using the GTAW process with fed wire, an increase in the height of the deposited walls was obtained due to a change in the electric arc shape, added to a higher deposition rate and lower temperature between the layers which resulted in smaller dendritic arm spacings. The electromagnetic device changes the electric arc shape, thereby improving the controllability of the weld pool and making it possible to deposit different bead geometries with greater geometric precision.