Kinetics of Oxygen Refining Process for Ferromanganese Alloys

Abstract

The present analysis of the experimental data by Yamamoto et al. permitted to determine the rate controlling mechanisms for the decarburization and evaporative manganese loss concurrently taking place during the oxygen refining process of ferromanganese melt.
When oxygen is supplied by a top lance blowing mode, the decarburization reaction takes place by three different mechanisms in sequence. The chemical reaction at the melt-gas interface controls the rate of decarburization during the first period, the rate of oxygen supply through the boundary layer in gas during the second period, and the mass transfer rate of carbon in melt during the third period when the carbon content is less than 2 mass%.
Manganese is lost primarily by evaporative reaction, but its dynamics are affected by the prevailing excess oxygen after accounting for CO formation. The excess oxygen and manganese vapor establish counter-current flux and form MnO mist at some distance away from the metal-gas interface. This creates two diffusion boundary layers, one for the flux of manganese vapor adjacent to the melt-gas interface and the other for the flux of excess oxygen in the gas phase. When the vapor pressure of manganese at the metal-gas interface is low, the rate of manganese vapor loss is controlled by the flux of excess oxygen. Otherwise, it is determined by the flux of manganese vapor.