Heat Intensity and Current Density Distributions at the Anode of High Current, Inert Gas Arcs

Abstract

Heat transfer intensity and current density distributions at the anode of high current arcs in predominantly inert gas atmospheres were determined experimentally. Measurements were made for stable, axially symmetric arcs having a small diameter refractory metal cathode and a plane, cooled copper anode. The experimental method consisted of splitting the anode, measuring the heat flux and the current to one of the sections as a function of arc position relative to the splitting plane, and calculating therefrom the distribution functions. The work encompassed the effects of gas pressure (195–790 mm Hg), cathode geometry and material (tungsten and W-1% ThO2), electrode separation (1.6–12.7 mm), arc current (100–300 amp), gas composition (argon, helium, and diatomic gas-argon mixtures), and localized constriction of the plasma column. Peak heat transfer intensities ranged from 1.0 to 20 kw/cm2 and peak current densities from 100 to 2500 amp/cm2. The heat and current distribution curves were of similar shape and were generally sharper than Gaussian. The heat distributions were partially resolved according to transfer mechanism. An upper limit was set on the average kinetic energy of electrons arriving on axis at the anode. This was used to specify limits on gas heat transfer intensities for certain conditions. The space charge sheath at the anode was estimated to be 10−4 to 10−3 cm thick at the arc axis.

Protection characteristics of a Faraday cage compromised by lightning burnthrough.

“…Figures 38 and 39 show the split probe. This type of probe was used in welding arcs by Nestor [10]. As the arc moves over the probe surface across the cut the current distribution on the two halves of the probe vary, and this information can be used to construct the current profile.…”

“…This design was based on a papers by Olsen and Nestor who employed it to examine the extent of a steady argon arc driven by currents ranging from 200 to 800 amps [26], [27], [10]. They used water-cooled, thin copper electrodes to measure the amount of current on each side of the split between two "D" electrodes and from that data backed out the radius of the plasma.…”

“…Other materials can also be considered (copper was used before in the split probes [10]). The thermal diffusivity is…”

Using Solid State Calorimetry for Measuring Gas Metal Arc Welding Efficiency

“…by (Tsai andEagar, 1985 andLu andKou, 1988). The authors used a calorimeter consisting of a split hollow water cooled copper Dee-anode (split-anode), developed by (Nestor, 1962). Current and voltage in autogenous gas tungsten arc welding (GTAW) and their affect on energy distribution and process efficiency were investigated.…”

Investigation on Temperature Distribution in SAW Weld Using 2D Mesh Model

“…[5] Research into the actual heat intensity distribution in welding arcs on a water-cooled copper anodemade, it is possible to determine the effect of distributed heat source on the weld geometry. [7] The assumptions in Rosenthal's analysis retained, including absence of weld pool convection, material properties variations, and latent heat of phase transformation other than the assumption to consider welding arc as a point heat source. Nevertheless, solutions considering welding arc as a distributed heat source were able to get rid of much of the experimental variations or deviations in the close environment of weld pool.…”