Modelling of electromagnetic processes in system ‘welding arc–evaporating anode’ Part 2 – model of arc column and anode metal

Abstract

A mathematical model of electromagnetic processes occurring in the 'arc column-anode regionevaporating anode' system is suggested. Electric charge transfer processes in the multicomponent plasma of the electric arc and in the bulk of the metallic anode are described using the Ohm's law and charge conservation law generalised for a case of discontinuity of the electric field potential at the boundary between the arc plasma and the anode surface. A procedure was developed for finding the numerical solution of the stated problem by the shock capturing method, allowing modelling of the electromagnetic processes in the 'welding arc-evaporating anode' system in the presence of a reverse potential jump in the anode region (negative anode drop). Results of modelling of the said processes for gas metal arc and plasma transferred arc welding of steel in an inert gas (Ar) atmosphere are given.

Numerical simulation of arc and droplet transfer in pulsed GMAW of mild steel in argon

“…the current path and the attachment of the arc at the wire electrode, dramatically change with increasing vaporization rates [12]. Krivtsun et al [13] present a complex model of the electric charge transfer in the anode region of an evaporating anode and couple it with a simplified arc model in which the changes in the electrode shapes are omitted as well [14]. In accordance to [11,12], it becomes evident that the arc attachment at the wire electrode is essentially determined by the metal vaporization.…”

“…Furthermore, we consider the temperature-dependant surface tension for the system argon-iron determined by Siewert et al [7] whose values are much higher (1.6 to 1.8 Nm) than the constant value of 1.2 Nm used in previously numerical models [8][9][10][11][12][13][14][15][16].…”

“…This effect could be illustrated calculating the current path in terms of a relative current by Eq. (1) [14]. By integration of the axial component of the current density j y (x; y) from the axis of rotation A (0, y) to the respective point of view P (x, y) within a plane in the arc at the axial position y, the current between the axis and the specific point can be calculated.…”

Synthesis and generalisation of welding fundamentals to design new welding technologies: Status, challenges and a promising approach

“…The Marangoni, evaporation, radiation and convection boundary conditions require information from the temperature fields (14 and 15). The boundary condition of heat from the arc also depends on physics at the anode spot (16). The anode spot boundary condition for Maxwell's equations also depends on the amount of metal vapours in the arc (17).…”

“…A mechanism involving surface oxides has also been reported 14. The anode spot is the least understood aspect of the electrode in GMAW, and there is no agreement on what equations to use to represent it, even in the absence of oxides 10, 11, 15, 16. Volumetric energy inputs in the melt from joule heating and frictional heating are typically neglected.…”