Abstract
Oxygen partial pressure of atmospheric gas should be clarified during surface tension measurement of high temperature metallic melts because oxygen is strong surfactant. When the sample evaporates at high temperature, the metal oxide is formed from the chemical reaction between the metal vapor, O2 molecule, and H2O molecule. In this case oxygen partial pressure of the gas would become lower near the melt surface. The oxygen partial pressure of the Ar-5vol.%H2 gas during surface tension measurement of molten iron using electromagnetic levitation was discussed in consideration of the sample evaporation from the point of view of intermolecular collision and thermodynamic equilibrium. The result indicated that the evaporation of Fe sample does not affect the oxygen partial pressure near the sample surface because the consumption of H2O corresponding to the formation of FeO during the collision is quite limited even though O2 and H2O molecules in the gas collide with Fe vapor above around 2080K very frequently.
