In this paper, the experimental examination of the oxide fluxes influence on penetration depth in GTAW welding was done. The effect of oxide fluxes based on nano and micro titanium-dioxide particles on austenitic stainless-steel welding was studied. It was shown that nano particles are more effective than micro particles, as well as that the mixture of the two results in the highest penetration. The basic mechanism that influences the increase in penetration depth is the reversal of Marangoni convection. That means, the melt of the weld metal flows from the edges to the center and towards the depth of the base material, instead of from the center to the edges, resulting in a narrower weld of the higher penetration.