On the Rate of Decarburization of Molten Iron with 1-120-Ar Atmosphere

Studies on the kinetics of gas-molten iron reactions-III

Abstract

In the early paper of this series, the authors gave the rate equation for the dissolution of oxygen from I-I20-Ar atmosphere into molten iron, assuming that a gaseous diffusion layer exists above the gas-molten iron interface as well as metal phase-diffusion layer generally supposed. Here, as an example of gas-molten iron reactions, the authors measured the decarburization of molten Fe-C alloy with H20-Ar atmosphere and tried to apply the previous result under a similar assumption to this reaction.Modifying the rate equation in previous paper for the present reaction, we obtain
-d%C/dt=1200D_mFP_H2O/Vρδ_G……(7)
which holds until an oxide film appears on the surface of molten iron.
In the same range, experimental data showed that the rate of decarburization is independent of the carbon concentration in liquid iron and that Eq.7 is in good agreement with the results.Activation energy of this reaction was found to be 5.5+3 kcal/ mole.On the other hand, the activation energy of diffusion coefficient, Dm, is 1.8 kcal/mole and that of 1/σG is supposed to be about 1 kcal/mole on the basis of the kinetic theory of gas molecules and hydrodynamics.Accordingly, the activation energy of this reaction calculated from Eq. 7 is expected to become only several kcal/mole, and this value agreed approximately with experimental results.Several investigators have found some larger values for the activation energy of decarburization reaction with atmospheres.However, if any suitable corrections for the rate of decarburization with crucibles were done, the values would become smaller ones of the same order as the present result.