Comment on `Ignition of a welding arc during a short-circuit of melted electrodes'

Abstract

Hajossy et al (1999 J. Phys. D: Appl. Phys. 32 1058) alleged that the break of a short circuit is preceded by the ignition of an arc because they estimated the relative field strength to be high enough for this to occur. This assertion has proven inconsistent with measured data. In particular, the typical sudden change from progressively rising to sharply dropping voltage contrasts with the alleged gradual commutation, but rather points to a detonation across the isthmus. Concerning the confinement of metal vapour due to inertia, the comment refers to Hess (1991 J. Phys. D: Appl. Phys. 24 36-40). There are several substantiated reasons why the minimal diameter of the bridge and also the voltage, required for a bypassing ignition, are actually larger than the values estimated by Hajossy et al, and why the bridge does not simply vanish. Somewhat misleading observations are blamed for the fallacies. The established wire explosion model of re-ignition is certainly valid, even in general. For that reason, there is no hope that the alleged premature ignition could be used for avoidance of the spatter-causing explosion.