Reactions occurring during steelmaking and refining do not reach thermodynamic equilibrium due to kinetic limitations. To take these into consideration, an effective equilibrium reaction zone (EERZ) model has been implemented into Thermo-Calc. This model assumes local equilibrium at phase interfaces, such as the interface between liquid steel and slag, but allows for the fact that thermal and composition gradients in the phases are present. The kinetics of the reactions are therefore limited by the mass and heat transfer to and from the reaction interface.
This figure, which was produced using the Process Metallurgy Module in Thermo-Calc, shows a comparison of predicted inclusion composition with the experimental data for a ladle refining process of a Ti-stabilized ultra-low carbon steel published by Graham and Irons.