This paper presents results of theoretical and
experimental investigation of the welding arc in Gas Tungsten Arc Welding
(GTAW) and Gas Metal Arc Welding (GMAW) processes. A theoretical model
consisting in simultaneous resolution of the set of conservation equations
for mass, momentum, energy and current, Ohm's law and Maxwell equation is
used to predict temperatures and current density distribution in argon
welding arcs. A current density profile had to be assumed over the surface
of the cathode as a boundary condition in order to make the theoretical
calculations possible. In stationary GTAW process, this assumption leads to
fair agreement with experimental results reported in literature with maximum
arc temperatures of ~21 000 K. In contrast to the GTAW process, in
GMAW process, the electrode is consumable and non-thermionic, and a
realistic boundary condition of the current density is lacking. For
establishing this crucial boundary condition which is the current density in
the anode melting electrode, an original method is setup to enable the
current density to be determined experimentally. High-speed camera
(3000 images/s) is used to get geometrical dimensions of the welding wire
used as anode. The total area of the melting anode covered by the arc plasma
being determined, the current density at the anode surface can be
calculated. For a 330 A arc, the current density at the melting anode
surface is found to be of 5 × 107 A m-2 for a 1.2 mm
diameter welding electrode.