# An Investigation into the Behavior of Cathode and Anode Spots in a Welding Discharge
## 3 Results
### Arc Discharge Stage
At the very edge of the sample, the anode spot has a plasma torch, which is directed parallel to the surface of the sample, and the arc column deviates (Figure 12b). Further, as the welding arc lengthened and closed on the substrate of the table, the anode spot continued to exist and also deviated to the side (Figure 12d). After switching off the current at the cathode, the cathode spot with a plasma torch continued to function (Figure 12e). Figure 11: Visualization of the inertia effect of emission processes in a stationary burning welding arc: (**a**)—anode spot under current load; (**b**)—turn off the current; (**c**)—anode spots under current load; (**d**)—arc switched off, no electric current. Figure 10: Visualization of the anode spot in the welding arc in motion 3.5 mm/s, I = 50 A, V = 12.5 V; (**a**) 2 s, (**b**) 5 s, (**c**) 9 s, (**d**) 12 s, (**e**) 15 s, (**f**) 18 s.  
Figures 13 and 14 show anode spots that form a round melt spot on the surface of the molten metal. We see that round-shaped anode spots have formed on the surface of the molten metal. In Figure 13a, the burning time of the welding arc was 5 s; this did not prevent a large volume of the welding bath from forming on the surface, which was formed by round-shaped anode spots. Next, we see Figure 13b-d, where the arc burning time increases and the spots on the surface of the bath do not disappear. Simultaneously, the current and voltage waveforms do not show any spikes. Figure 14 shows the shape of the anode spot with the location of the spots along the circumference and with one central spot, similar to a wheel with spokes. During the experiments, we found that at the moment of ignition, a brightly glowing central region appears in the discharge. After 100-250 ms, a less bright second area appears, surrounding the first. A third, dark area, poorly reflecting light, is located along the edge of the spot. Comparing the size of the anode spot in the autographed photo shows that the maximum dimensions in the photo are comparable to the size of the bottom of the shallow edges of the well. As the discharge develops and the current increases, the central region oscillates in the direction of increasing and decreasing size, with particularly noticeable fluctuations on materials with low thermal conductivity. When the current increases to 10-25 A, it rebuilds the spot, expands the central area to the \"limit\", and transforms into a ring of individual spots (Figures 13c and 14). Figure 12: Visualization of the inertia effect of emission processes in a moving burning welding arc (mode: in motion 3.5 mm/s, I = 50 A, U = 12.5 V): (**a**)—well pool along the edge of the sample; (**b**)—formation of a network of anode spots; (**c**)—contraction of the spot network into one large anode spot; (**d**)—division of the welding arc into anode and cathode string modes (**e**)—switching off the current, the anode and cathode spots continue to exist. Moreover, the size of the spots is approximately equal to the central spot at the time of ignition. After several tens of milliseconds, the ring disappears, and one spot in the center or only one of the spots in the area of the ring begins to glow. Similar changes are taking place in the second area. As the discharge current decreases, the size of the rings and spots also decreases. The process of crushing the anode spot begins earlier, the greater the current strength, with an increase in current on materials with a low boiling point and thermal  
Figure 14: Anode spot with peripheral binding: (**a**) original photo, (**b**) the processed photo using a brightness gradient filter. Figure 13: Anode spots on the surface of molten metal (**a**) 5 s; (**b**) 7 s; (**c**) 9 s; (**d**) 12 s (mode-I = 20 A, U = 10.5 V). conductivity. The size of the second region increases with increasing current and duration of the discharge: the greater the thermal conductivity coefficient, the lower the melting point of the anode material.