Effect of dynamic wire in the GTAW process

Keyhole GTAW with Dynamic Wire Feeding Applied to Orbital Welding of 304L SS Pipes

“…The joint design was a "U" profile as the dimensions shown in Figure 1. The orbital welding process used was the GTAW with dynamic wire feeding, which means a forward and backward movement applied in the wire feeder, as shown previously by Silva et al [5]. In this case the wire's oscillation frequency was around 20 Hz and the hot wire technique was also used.…”

“…The filler wire's speed is also reduced, so the amount of arc's heat transferred to the wire is also lower and more heat is directed to melts the base metal. The dynamic wire feeding and its vibration can mitigating the defects generation, according to metallic transfer behavior discussed in other works [5][6][7]. In the overhead position (from 160º to 180º) the behavior of the liquid material changes again, in this case was necessary to reduce the intensity of the welding current in order to avoid burn through, which would occur if it was kept at the same intensity as the vertical position.…”

“…Each peak oscillation in the voltage corresponds to a forward and backward event. Despite this, as detailed in the literature, it is possible to reach conditions in which the metallic transfer is through bridge mode (wire in constant contact with the molten material), depending on conduit layout, the forward and backward movement is not transferred to the wire's tip [5]. The Figure 5 shows a shortened version of the current and voltage signals behavior (2 seconds for each position) for all positions in the root welding.…”

“…The frontal videography of the keyhole profile hides the filler wire melting in the pool, so an efficient way to verify its regularity is by the welding voltage signal. Silva et al [5] showed that the dynamic feeding promotes an oscillation in the voltage signal due to the wire's movement under the arc. Each peak oscillation in the voltage corresponds to a forward and backward event.…”

“…Over recent years, a new approach of wire feeder has been used in which a forward and backward movement is applied to the feeder by an electromechanical system. This creates a similar behavior in welding wire's tip, increasing the process robustness and smoother metallic transfer [5]. Silva et al [6] called this technique as dynamic wire feed.…”