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 understanding on arc interruptions in Tandem Pulsed GMAW and how the current pulsing synchronism 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 prevent 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 interruptions 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.