Thermodynamic Study of the Processes of Oxidation of Fe-C Melt Impurities due to Interaction with the Bubble of the “Neutral Gas – Oxygen” System

Abstract

Modern trends in the improvement of liquid steel production processes are aimed at combining the possibilities of assessment and analysis both by technological indicators and on the basis of analytical thermodynamic calculations. Among the thermodynamic indicators, the Gibbs free energy indicator is especially noted, that allows predicting the possibility of certain chemical transformations occurring.

The present state of the metallurgical industry in order to maintain competitiveness on the market creates the conditions for the relevance of research aimed at the intensification of physico-chemical transformations in slag-metal systems, including at the stage of out of furnace processing of the obtained liquid semi-product. One of the methods of intensification is to increase the mass transfer efficiency in the slag-metal bath. This might be achieved by introducing an additional stirring gas (in particular, the “oxygen-argon” system). In the work, an evaluation of a promising method of steel treatment after tapping into the ladle by means of oxidizing purging through the bottom with a mixture of neutral gas and oxygen was carried out from the point of view of the thermodynamic index of the course of reactions. The analysis was carried out on the example of a 250-ton steel ladle for three possible reaction zones: metal – gas bubble, metal – slag, slag – gas bubble, taking into account the effect of different levels of immersion in a metal bath to account the effect of changing hydrostatic pressure on the course of reactions. It has been confirmed that the increase in hydrostatic pressure during immersion in the bath contributes to the course of reactions, as a result of which the amount of gas produced is less than that involved in the reaction. It was established that when blowing through the bottom with a mixture of gases containing oxygen, with an increase in the depth of the bath, an activation of the reaction of dissolving gaseous oxygen in the melt is observed; reactions in which gaseous oxygen takes part become more active, the possibility of oxidation reactions of phosphorus, silicon, manganese and carbon with the formation of CO₂ increases.