Gas tungsten arc models including the physics of the cathode layer: remaining issues

Abstract

A recent review pointed out that the existing models for gas tungsten arc coupling the electrode (a cathode) and the plasma are not yet complete enough. Their strength is to predict with good accuracy either the electric potential or the temperature field in the region delimited by the electrode and the workpiece. Their weakness is their poor ability to predict with good accuracy these two fields at once. However, both of these fields are important since they govern the heat flux to the workpiece through current density and temperature gradient. New developments have been made since then. They mainly concern the approaches addressing the electrode sheath (or space charge layer) that suffered from an underestimation of the arc temperature. These new developments are summarized and discussed, the modelling assumptions are examined, and important modelling issues that remain unexplored are underlined.

Multiphysics modelling of Gas Tungsten Arc Welding on ultra-thin-walled titanium tubing

“…Modelling the GTAW arc accurately requires a detailed representation of the cathode (the electrode in DCEN), the plasma column (the highly visible portion of the electric arc) and the cathode layer (the sources of the various electron emissions) [28]. Whilst some issues still remain [29,30], in recent years there have been multiple sophisticated models of the GTAW arc that elucidate the plasma physics involved [31][32][33]. These accurate GTAW arc models enable a understanding of the heat input into the work piece.…”

“…This is before any interaction between the arc plasma and work piece is considered. This modelling approach is achievable with appropriate key assumptions [30], yet adds considerable complexity beyond CWM and WPM. Instead, as shown previously in Figure 2.2, heat input can be simulated in lieu of the physics of heat generation.…”

Investigation of the interaction of dense noble gas plasmas with cold cathodes:III—Arc spot ignition on pure and doped W cathodes

“…One of the most important materials in plasma technology is pure and doped tungsten. Tungsten electrodes are applied, for example, in arc welding [9,10] or in high-intensity discharge (HID) lamps. [11] The formation of arc spots on cold tungsten electrodes of HID lamps plays especially a role when the lamps are ignited.…”

Investigation of the interaction of dense noble gas plasmas with cold cathodes: I—Experimental setup and application to Al, Cu, Ti, and graphite cathodes

“…[ 2 ] Examples for intentionally applied arcs can be found in electric switchgears for low as well as high voltages [ 3,4 ] or in tungsten inert gas welding. [ 5,6 ] Another example is the ignition phase in high‐intensity discharge lamps during which the cold electrodes are heated up onto their stationary operation temperature. [ 7–10 ] Current densities of the order of 10 8 A/m 2 are locally observed within arc roots on cold cathodes initiating the spot, emitter spot—but also the diffuse mode of cathodic arc attachment.…”