MIG/MAG – short circuit metal transfer – welding power sources versus arc gases

Abstract

In the MIG/MAG process, the properties of a gas or gaseous mixture are not normally considered in association with the properties of the welding power source to be used. This work is intended to show that this is a scientific and technological weakness that affects some commercial aspects, whether in relation to the power sources or to the gases. By means of fillet weld tests with observation of the resulting appearance, of the verification of its geometry, of the oscillograph reading and of the elaboration of histograms it is shown that the influence of the shielding gas on weld quality is not a simple consequence of the properties of the gas referred to, but inter-dependent on the properties of the source. The relationship between the properties of the gases and the properties of the sources is determined based on the possibility of regulation of the dynamics of the source in a specific, independent way in the phases of the short circuit and of the re-establishment of the arc in metal transfer welding by short circuit. Two gases were used as comparisons: Pure CO₂ and a mix of argon and 25% of CO₂. It is shown that welds of equivalent quality can be obtained with these different gases, depending on the welding power source dynamics.

Keywords:

• metallic transfer
• shielding gases
• welding power sources
• inductance