THE RELATION OF CARBON OXYGEN REACTION AT METAL/SLAG INTERFACE WITH CERTAIN OXYGEN PARTIAL PRESSURE IN GAS PHASE

摘要

The carbon-oxygen reaction at the metal/slag interface exists in the whole steelmaking process from the beginning of melting to the end of refining. This reaction is important since it governs decarburization, desulphurization, dephospherization and degassing in steelmaking. A systematic experiment has been done in our lab for studying the carbon-oxygen reaction at slag/metal interface in an open system. The experiment results showed that, if the oxygen partial pressure in the gas phase is very low and the electronic conductivity of slag can be neglected, the reduction rate of FeO dissolved in the calcium silicate slag by carbon in metal will get slower as the carbon content is getting smaller and the reduction rate finally will completely stop at the carbon content decreasing to 2%. This phenomenon may be called as "composition barrier" of carbon-oxygen reaction at slag/metal interface. When oxygen partial pressure increases, this reduction rate will increase either. However, this "composition barrier" of 2% [C] will be still there. On the other hand, if an external electrode was introduced to connect the metal phase and slag, the situation will change. The "composition barrier" will be broken and the reaction will continue to proceed to the end of reaction thermodynamically. Besides the reduction rate is also increasing with the increase of oxygen partial pressure in the gas phase. This experiment result means that, it will be significant to increase oxygen partial pressure only when the external conductor exists. Based on our experiments a model of carbon-oxygen reaction has been proposed, which can explain all these phenomena. The implicates of this new theory to some new potential technology in steelmaking have also been discussed