Temperature dependence of surface tension of molten iron under reducing gas atmosphere

Abstract

Surface tension of molten iron was measured under Ar-He-5vol.%H2 gas by oscillating droplet method using electromagnetic levitation furnace in consideration of the temperature dependence of oxygen partial pressure, Po 2, of the gas. For comparison, the measurement was carried under Ar-He atmosphere to fix the Po2 of the inlet gas at 10 -2Pa. The surface tension was successfully measured over a wide temperature range of about 780K including undercooling condition. When Po 2 is fixed at 10-2 Pa, the surface tension increased and then decreased with increasing temperature like a boomerang shape. When the measurement was carried out under the H2-containing gas atmosphere, the temperature dependence of the surface tension shows unique kink at around 1810K instead of liner relationship due to competition between the temperature dependence of the Po2 and that of the equilibrium constant of oxygen adsorption reaction. The relationship between the calculated lnKad with respect to inverse temperature using Szyszkowski model was different between the atmospheric gases.