The use of electrostatic probes to measure the temperature profiles of welding arcs

Abstract

The electrostatic probe is an attractive diagnostic tool for DC welding arcs. The current-voltage characteristic of such a probe in a high-current (100 A), high-pressure (1 bar), DC argon (TIG) welding arc is found to give a very flat ion saturation region. Sheath thicknesses are estimated to be much smaller than 1 μm, ie less than the mean free path, so that conventional collisionless probe theory should be applicable - in contrast to the flame plasmas dealt with by Thomas (1969) and others. By using an Abel inversion technique the measured probe current can be converted to a radial distribution of current. The temperature variation across the arc can then be derived from this current variation. By measuring the radial temperature profile at several points along the length of the arc column, a complete isothermal map of the TIG arc has been obtained which is important for basic calculations of energy transfer.

Problems and issues in laser-arc hybrid welding

“…5 Temperature distribution in the arc column under GTAW conditions for an arc current of 100 A. The temperatures in the arc column were calculated using electrostatic probes 127 6 A typical spectrum of the plasma produced during laser welding of AISI 201 stainless steel using helium shielding gas 131 Ribic et al Peaks containing excited and ionized Fe, Cr and Mn species are observed because of their presence in the plasma. Since the metal vapours are easily ionisable compared to the argon or helium shielding gas, their presence significantly affects the electron density and electron temperature of the laser induced plasma.…”

On the influence of the nozzle length on the arc properties in a cutting torch

“…Also, the shorter nozzle produce a thinner arc (the profile decays abruptly at ≈ 0.7 mm, whereas the corresponding to the larger nozzle at ≈ 0.85 mm). It is worth noting that the abrupt decay at the end of the profiles cannot be taken with confidence as it is an artifact of the Abel inversion technique [11]. The plasma density profiles shown in Fig.…”

Determination of GTA and GMA welding arc temperatures

“…6 This method may be used for the determination of arc temperatures within the temperature range of 7 000 to 16 000 K and at current intensities in excess of 35 A. The method is suitable for the plotting of isotherms of the welding arc ( Fig.…”

“…Models of the welding arc are being constructed with a view to gaining a better insight into the occurring phenomena [1][2][3][4][5] including arc temperature since this is the parameter which influences all of the changes taking place. 6 Investigations into the welding arc temperature lead to a better understanding of its working, The temperature of the welding arc varies from 5 000 to 30 000 K depending on the welding parameters and the type of shielding gas. After the introduction into the arc's plasma of easily ionized atoms of sodium or potassium, a maximum temperature of the order of 6 000 K can be reached.…”