STUDIES ON THE DECARBURIZATION REACTION OF MOLTEN Fe-C ALLOYS (II)
Effect of the Oxygen Pressure on the Velocity of Decarburization Reaction with Oxygen Gas
1954 Volume 40 Issue 10 Pages 973-979
Details
1954 Volume 40 Issue 10 Pages 973-979
In order to study the effect of the oxygen pressure on the decarburization reaction, Fe-C alloys containining about 1-4% carbon were melted and decarburized with the oxygen gas stream, which had previously been prepared to show a partial pressure between 20 and 760mm Hg by mixing pure oxygen gas (or pure nitrogen) into air, the rate of the carbon removal being measured by flow method. In this case the equation of the rection rate was simplified as follows:
The carbon contents measured at every time interval into this equation being introduced, the values of the specific constant, k0, were estimated for various oxygen pressures with the result of which the relation between k0 and po2 was found as
Besides this, in case of lower carbon contents up to 1%, each value was found to be constant at higher oxygen pressures above 300mm Hg, where the oxygen contents on the surface of molten iron, could be presumed as predominant over those of carbon. In order to determine where the reaction occurred, the reaction rate was measured by varying the area of interface between gaseous and liquid phases. In consequence, it was found linearly proportional to that area, the reaction being shown to take place on the interface. The oxygen contents, dissoved in molten iron during the process of this reaction, were analysed in the samples killed with aluminum and were found to have no proportionality to the partial pressure of oxygen in gaseous phase, and to show the characteristic values corresponding to carbon contents. According to the results stated above, the reaction mechanism of this sort was presumed as follows:
(1) The oxygen molecule dissociated on being adsorbed at the gas-metal interface, and then its atom was dissolved into the surface layer to participate in the reaction.(2) The oxygen which participated in this reaction must be in equilibrium with that in the gaseous phase at a given pressure.
When the pressure of carbon monoxide produced in the reaction became considerable as compared with the oxygen pressure, this reaction was found to be retarded by the former gas.
