Effect of the arc velocity on the cathode erosion rate in argon-nitrogen mixtures

Abstract

Erosion measurements on a copper cathode are reported. The 100 A arc, driven by a magnetic field, runs continuously for up to 30 min between two concentric cylindrical electrodes. Argon-nitrogen gas mixtures in various proportions are blown through the electrode gap. The erosion rate in argon is drastically reduced by the addition of only 1% nitrogen and is further reduced as the nitrogen content increases in the gas mixtures. The decrease in erosion rate is found to be correlated to an increase in arc velocity.

Erosion of the Cold Electrode as an Ablation Process in Unsteady Arc Spotsa

“…With an effective enthalpy of h ef = 130 MJkg −1 , we obtained in Fig. 1b a rather good agreement of the continuous model to the experimental data 11. The difference between these g 0 and h ef values and those presented in this paper may be explained by the difference in the plasma gas composition and in the material of electrodes 11.…”

“…1b a rather good agreement of the continuous model to the experimental data 11. The difference between these g 0 and h ef values and those presented in this paper may be explained by the difference in the plasma gas composition and in the material of electrodes 11. The authors in 11 used pure electrolytic copper as cathode material and argon‐nitrogen mixtures as the plasma‐forming gas.…”

“…Fig. 1b presents a qualitative comparison (qualitative, because the authors did not measure the temperature of the cathode) between the continuous thermophysical model described herein and the Szente's et al experiments 11. The temperature regime of the experiment was evaluated by matching the theoretical curve with the experimental point in the transition region of the descending branch of the curve to the horizontal one.…”

“…Full square points have experimentally correlated conditions: same magnetic field B , same gas and water cooling flow rates. Open square points: random experimental conditions; (b) Comparison between the theoretical specific erosion rate g for the continuous model and the experimental data taken from 11 versus the arc spot velocity v ; (c) Comparison between EDM experimental data taken from 12 and predicted step‐wise model on the influence of the duration of the pulsed discharge on the erosion of steel cathode.…”

Electrode Phenomena in Plasma Torches

“…For a given current, the velocity of the attachment movement is the principal factor determining cathode erosion. Szente et al [1987a, 1987b] found for a magnetically driven 100A arc between two concentric tubular copper electrodes a relationship for the velocity dependence of the erosion rate…”