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.