Arc Interruptions in Tandem Pulsed Gas Metal Arc Welding

Abstract

In addition to electromagnetic attraction between the arcs in Tandem Pulsed gas metal arc welding (GMAW), arc interruptions, mostly in the trailing arc at low mean current levels, may also occur, which is a phenomenon not widely discussed in the welding field. These arc interruptions must be avoided, since they also represent interruptions in metal fusion and deposition during the welding process, leading to lack of fusion!penetration and/or deposition flaws, adding cost for repairing operations. To improve the under standing on arc interruptions in Tandem Pulsed GMAW and how the current pulsing syn chronism between the arcs relates to this phenomenon, this work proposes to evaluate the influence of parameters of adjacent arcs (Tandem Pulsed GMAW) and also of a single arc (GTAW-gas tungsten arc welding), but similarly subjected to magnetic deflection, on the occurrence of arc interruptions!extinctions. High-speed filming was used to help understand the interruption!extinction mechanism. In the case of Tandem Pulsed GMAW, the pulses of current of the leading and trailing arcs need to be almost-in-phase to pre vent interruptions in the trailing arc. The distance of 10 mm between the adjacent arcs helped reduce the incidence of trailing arc interruptions, yet keeping a sound weld visual quality. In the case of GTAW, the higher the electrical current flowing through the arcs and the shorter their lengths, the more they resist to the extinction. The trailing arc inter ruptions in Tandem Pulsed GMAW seem to be determined by the deflection and heat in this arc, and their prevention can be achieved by a balance between these two factors, which is reached by synchronized pulsing currents.

Gas Tungsten Arc Welding with Synchronized Magnetic Oscillation

“…These instabilities in the arc may even lead to its extinction, even temporally. Problems with arc instability and interruption in double wire GMAW are mentioned in the literature [7,[9][10][11]. The main reason for this phenomenon is linked to magnetic fields generated by the arcs operating adjacent to each other and the "stiffness" presented by these arcs.…”

Soldagem TIG com Oscilação Magnética Sincronizada

“…Estas instabilidades no arco podem até mesmo levar ao seu apagamento. Problemas com instabilidade e interrupção de arcos em soldagem MIG/MAG Duplo Arame e em soldagem TIG foram relatados na literarura [5][6][7][8]. A principal justificativa para tal fenômeno esta ligada aos campos magnéticos gerados pelos arcos que operam adjacentes um ao outro ou à aplicação de campos magnéticos relativamente elevados e à "rigidez" apresentada por estes arcos.…”

“…Como indicado, alguns testes tiverem instabilidades do arco e não permitiram medições adequadas. Nestes casos, o arco estava tão defletido que começava a se "descolar/desconectar" (inclusive com variação de extensão da deflexão) da chapa de forma muito similar a trabalhos anteriores [6][7][8]. Essas instabilidades reafirmam que arcos com menores correntes de soldagem e/ou comprimentos maiores são menos rígidos mecanicamente (mais fáceis de defletir) e são, ao mesmo tempo, menos rígidos termicamente (mais fáceis de apagar).…”

Arc stability and ablation characteristics in O2, N2, and air environments

“…Arc duration and stability play a key role in the quality and efficiency of arc welding and cutting. In the process of arc welding, the arc duration and stability determine the shape of the weld and then affect the formation and stability of the welding pool [4,5]. In the process of arc cutting, arc duration, and stability directly affects the quality and speed of cutting [6].…”