THEORETICAL INTERPRETATION OF THE DECARBURIZATION MECHANISM IN CONVECTIVE OXYGEN STEELMAKING

The theory of gas absorption is introduced in order to understand the decarburization mechanism theoritically. When the existing decarburization kinetic data are applied to instantaneous reaction regimes of the theory, it can be clearly explained. The decarburization mechanism in convective oxygen steelmaking can be described sufficiently by the overall reaction l/2O2 +C → CO whether decarburization follows a direct or indirect path. The reason for this phenomenon is that the feature of instantaneous reaction remains unchanged by the intensive convection in the liquid phase. The decarburization mechanism depends only on the two stages of carbon concentration. The criterion for transition from a high-carbon to a low-carbon regime is estimated to be C < (ka/kL) ·P O 2. In the high-carbon regime, which shows zeroth-order kinetics with respect to carbon concentration, oxygen absorption into a liquid phase is always considered to be the controlling step, and the controlling parameters are a, kG, and P O 2, among which the most important parameter is the gas/liquid interfacial area, a, in the case of high-speed injection of pure oxygen. In the low-carbon regime, the controlling step is the transport of carbon in molten steel, and first-order kinetics in terms of (kL·a) · C can be approximated. It indicates that if the outer controlling parameter (kL · a) is conserved, the intrinsic change in carbon concentration is more important than the kinetics itself. © 1990 The Minerals, Metals & Material Society.