Kinetics of Decarburization of Liquid Iron in Ar-CO-CO₂ Atmospheres

Abstract

The present paper deals with a kinetic study of decarburization of liquid iron in Ar-CO-CO₂atmospheres at 1600°C. The study has been especially devoted to determining therate-controlling step at low carbon contents of the melt.
At concentrations of carbon highr than 0.02-0.05 %, the rate of decarburization is controlled primarily by gaseous mass transfer.
At concentrations of carbon lower than 0.02-0.05 %, the rate of decarburization no longer depends on the gas flow rate, if it is higher than 1300cc/min. The rate-co, ntrolling step of decarburization under this condition varies according to the composition of Ar-CO-CO₂.
Chemical reaction becomes important in rate-controlling mechanism as the partial pressure of Ar or CO in the gas mixture increases, while mass transfer of carbon becomes important as the partial pressure of CO₂ increases.
In the range of chemical reaction control, the experimental reasults are explained reasonably by the model based on the simultaneous reactions: CO₂+C←/→2CO, CO₂←/→CO+O, C+O←/→CO.
In the range of mass transfer control, the value of mass transfer coefficient of carbon is the same as that for the decarburization by CO-CO₂ and Ar-CO₂.It is concluded that the mechanism of decarburization by CO-CO₂ and Ar-CO₂, previously studied, can be explained on the basis of the present study.