The Surface Tension of Liquid Iron Containing Nitrogen and Oxygen

The surface tension liquid of Fe–N, Fe–O and Fe–N–O alloys was measured with sessile drop method at 1 823 K. The effect of nitrogen, oxygen and coexistent nitrogen and oxygen on the surface tension of liquid iron was investigated. The results show that both nitrogen and oxygen are surface-active elements in the liquid iron. The surface tension of liquid iron decreased with increasing nitrogen and oxygen contents. The surface-active nature of nitrogen decreases with increasing of oxygen content. The variation of surface tension with the activity of the surface-active elements was obtained as follows: Fe–N alloy: σ=1930–267 ln(1+45aN), [O]=20–30 mass ppm Fe–N alloy: σ=1990–318ln(1+130ao), PN2=3.1×10–5atm Fe–O–N alloy: σ=1990–318ln(1+130ao)–(282–7636ao–83152ao2) ln(1+45aN)