A main problem raised by arc welding manufacturing is the determination of the optimal process parameters to ensure weld quality as well as resource efficient and sustainable production. To address this problem a better process understanding is required. In this study thermal magneto hydrodynamic modeling of a welding arc is used to reach a deeper insight into the influence of the composition of the shielding gas on the pressure force and the heat fluxes to a workpiece. The model was implemented in the open source simulation software OpenFOAM. Four different shielding gas mixtures combining argon and carbon dioxide were studied. When increasing the fraction of carbon dioxide the results show a significant increase of the arc velocity and temperature with constriction of the

temperature field, a decrease of the pressure force and a significant increase of the heat

fluxes on the base metal.