抄録
In order to study the kinetics of reaction between atmosphere and molten iron, we investigated the rate and mechanism of oxygen dissolution from H2O-Ar atmospheres into molten iron. Results are as follows:
The mechanism of reaction is supposed to occur in three steps. At first, H2O molecules from the atmosphere diffuse on the gas/molten iron interface, and the diffusion rate equation may be expected to be dm/dt=DmFM (PH2O-PH2Oi) /δG (1). At the gas/molten iron interface, the chemical equilibrium, H2O (g) =H2 (g) +O, is always attained. At the last step, O diffuses from the surface of molten iron into the core, and the corresponding equation may be dm/dt =DLFρ ([O] i- [O]) /VδL (3). When Eq. (1) is larger than Eq. (3), O is accumulated on the surface of molten iron and an oxide layer forms.
On the basis of the kinetic theory of gas molecules, it was confirmed that the chemical reaction between H2O and Fe hardly proceeded in a gaseous phase of the lack of Fe vapor, and it was supposed that the chemical reaction took place only at the gas/molten iron interface.
Experimental data seem to show that the rate determining step of the reaction is the diffusion of H2O through the diffusion layer in the gaseous phase at the gas/molten iron interface in cases where no oxide laye-rs appear at the surface of molten iron. In these cases, the rate of reaction is approximately proportional to the partial pressure of H2O in atmosphere. When an oxide layer appears on the surface of molten iron, the reaction becomes one of gas/slag/molten iron and the rate determining step is the transport of O from the surface of molten iron into the core.
