Electrical characteristics of the oxyfuel flame while cutting steel

Abstract

We present the first published record of electrical phenomena in the oxyfuel cutting torch flame while cutting a steel work piece. Measurements of the voltage-current characteristic between the torch and the work piece demonstrate three piecewise-linear regimes in the ±10 V range. Flame resistance measurements in the ohmic regime are studied using three candidate excitation signals while varying fuel/oxygen ratio, feed rate, and standoff distance. Electrical characteristics are also observed during successful and unsuccessful pierce and loss-of-cut events. The flame’s electrical resistance is found to be 2.8 kΩ per mm of length; a factor of 3 smaller than the same conditions without cutting oxygen. We present an argument that the drastic increase in plasma conductivity is due to an abundance of electrons produced at the work piece. We draw preliminary conclusions about the potential applicability of these measurements for the in-process detection of standoff, pierce success, and loss-of-cut events.