Numerical Investigation of the Effect of the Cathode Geometry on the Characteristics of an Electric Arc

Abstract

The effect of the cathode geometry on the characteristics of an electric arc is treated. It is found that the characteristics of plasma in discharges with cathodes of different geometry (cone, sphere, cylinder) are almost the same on condition of equality of the areas of current-conducting surfaces. It is assumed that a ring-shaped arc discharge may be realized in the case of axisymmetric arc spot on the external side surface of a cylindrical cathode.

Dimensionless representation of the column characteristics and weld pool interactions for a DC argon arc

“…More recently, the mathematical models of electric arcs in welding have evolved and now they are more specialised to describe specific unsolved topics in the electric arc such as a detailed description of the cathodic and anodic regions that do not meet the Local Thermodynamic Equilibrium condition that prevails in the arc column [8]. Besides, specific issues in welding have been studied such as the depression of the weld pool [9, 10], the effect of the type of material and geometry of the electrodes [11, 12], the effect of the cover gas composition and mixture of gases [13, 14], and the formation of droplets in consumable electrodes [15], among other issues. However, due to the high complexity of the arc physics, these numerical models have not been used yet to summarise the knowledge generated by the models in the form of simple equations or simple graphs to be used in practice by welders.…”

Generalized representation of arc shape, arc column characteristics and arc-weld pool interactions for DC electric arcs burning in monoatomic gases

“…It was found that the arc shape depends exclusively on the current and the shielding gas and not on the arc length. Thus, both the axial and radial distances are presented in dimensionless form by (1) dividing each coordinate by the cathode spot radius R c , which depends on the current (See equations (1)), and (2) multiplying by Pr 0.85 , where Pr is the Prandtl number of each gas evaluated at its respective isotherm boundary (e.g. 10 000 K in Ar).…”

“…Nowadays, numerous numerical models and experimental trials try to describe the complex phenomena present in a DC electric arc used for arc welding. From the great diversity of research works studying the electric arcs, there are those focused in the material and shape of the electrodes [1,2], shielding gases [3,4], weld pool depression [5,6], and metallic vapor formation [7,8], among many other subjects. These works have helped to gain significant insights into the physical phenomena and contribute to technological advances in arc welding processes.…”