Gas influence on the arc shape in MIG-MAG welding

Composition of the applied shielding gas has a strong influence on physical properties of the
plasma and parameters of the welding process. In particular, increase of the percentage of carbon dioxide
in argon results in an increase of the transition current value while changing from the globular to spray
mode of metal transfer during the welding process. In order to explain this phenomenon, the MIG/MAG
welding arc plasma was investigated for different mixtures of argon and carbon dioxide in the shielding
gas. Applying a fast camera, recording distribution of spectral lines of the plasma components, we noticed
some phenomena not described yet in the literature. Especially, there is a limit in the percentage of relative
concentration CO2/Ar beyond which the arc shape is significantly modified.
PACS. 52.50.Dg Plasma sources – 52.50.Nr Plasma heating by DC fields; ohmic heating, arcs – 52.70.-m
Plasma diagnostic techniques and instrumentation – 52.77.-j Plasma applications