The Deoxidation by Metal-(Acidic or Basic) Slag Reactions

Kinetic study on the deoxidation of steel-II

Abstract

The mechanisms of deoxidation utilizing the potential difference of oxygen between metal and acidic or basic slag and of other accompanying reactions were intended to be solved.
At first oxygen, manganese and silicon transfer rates between iron bath and MnO-FeO-SiO₂ ternary slag saturated with silica were measured. Then the reactions between such slags and iron bath which previously contained manganese and silicon to confirm the existence of quasi-equilibrium states were investigated.
The obtained results were discussed with the unsteady diffusion equations and rate determining steps were worked out by experimental results and calculations.
The conclusions are as follows:
1) The deoxidation rate would be mainly controlled by the transfer rate of oxygen from iron bulk to the interface but the resistance of slag to the diffusion of oxygen could not be neglected.
2) The dissolution rate of manganese oxide might be controlled by the diffusion of manganese from the interface to iron bulk.
3) Addition of lime to those ternary slags increased the dissolution rate of manganese oxide but decreased the deoxidation rate.
4) Quasi-equilibrium states, in other words, minimum or maximum values of some components wefe observed.
For the experiments using basic slags the authors developed lime crucibles utilizing appropriate amount of titanium oxide as binder in order to keep both phases, slag and metal. Because of some failures in making crucibles, attention was mainly paid to the transfer rate of manganese between metal and slag.
According to the obtained results:
1) The deoxidation is a little faster than in case of acidic slag because of difference of slag constitutions.
2) The dissolution rate of manganese oxide would be controlled by the diffusion of manganese ion.
3) Silicon in iron bath increases the dissolution rate of manganese oxide.
4) The rate of elimination of manganese in iron bath by iron oxide of slag could be controlled by the diffusion of manganese in iron bath.
5) Manganese transfer between iron bath and magnesium oxide bearing slag is much slower than in case of lime bearing slag.