Interfacial kinetics of nitrogen with molten iron containing sulfur

Abstract

The effect of sulfur on the interfacial reaction rates of nitrogen dissolution into molten iron has been investigated at 1823 K using an isotope-exchange technique. In addition, surface activities of the vacant sites and the sites occupied by sulfur have been proposed to predict the interfacial reaction rates and to clarify the rate-determining step of nitrogen dissolution into molten iron using the sulfur adsorption that had been obtained in our previous study. It was found that the experimental results were in good accordance with the predicted values for adsorbed N2 dissociation control rather than those for N2 adsorption control in the low sulfur activity region, yielding that the dissociation of nitrogen molecule into atoms at the surface is the rate-determining step of the interfacial reaction of nitrogen dissolution into molten iron. However, with increasing sulfur content, the experimental results showed higher values than the predicted ones assuming that reactions only occur at vacant sites. In the high sulfur content region, it was considered that reactions at occupied sites might occur. Accordingly, the total interfacial reaction rate constant (mol/cm2 sec atm) of nitrogen dissolution could be expressed as k=6.2×10-5 av2+4.0×10-7 aθ2+7.0×10-6 avaθ.