KINETICS OF THE REACTION OF H2O GAS WITH LIQUID-IRON

The rate of the decarburization of carbon-saturated liquid iron by H2O gas between 1673 and 1873 K has been studied under conditions in which the effect of mass transfer is negligible, or a reasonable correction for its effect can be made. The rate was measured for water vapor pressures in the range 0.002 to 0.3 atm and sulfur contents in the metal from 0.005 to 0.5 mass pct. The measured rates are consistent with the rate-controlling reaction being the dissociation of H2O on the surface. Sulfur was found to significantly decrease the rate, and the residual rate phenomenon was observed at high sulfur content. The rate constant for the dissociation of H2O on liquid iron is given by k = k-degrees/1 + K(S)a(S) + k(r) where k-degrees, k(r), K(S), and a(S) are the rate constant for pure iron, residual rate constant, the adsorption coefficient of sulfur, and the activity of sulfur in the metal relative to 1 mass pct in carbon-saturated liquid iron, respectively. The rate constants and adsorption coefficient were determined to be log k-degrees = -4860/T + 0.57 (mol/cm2 s atm) log k(r) = -5350/T - 1.03 (mol/cm2 s atm) log K(S) = 3870/T + 0.51