Thermodynamic Constraints and Prospects for Intensified Steel Deoxidation

The thermodynamic constraints of steel deoxidation are discussed based on calculated [%Me]–[%O] diagrams for different deoxidizing elements in pure Fe and five examples of steel grades, highlighting the influence of alloying on the equilibria. The role of deoxidation product oxides is considered with special emphasis on the activity of SiO₂ and the possibility of utilizing slags with a very low a_SiO2 to amplify the deoxidizing power of silicon. This effect was verified for SiCr spring steel and 18Cr8Ni stainless steel. The results indicate a strong reduction in equilibrium oxygen content. Different means for industrial implementation of this principle are discussed. The conventional steel/slag equilibration via gas stirring is tested in practice. As potentially more efficient methods, slag powder injection (argon, lance) and cored wire injection combined with argon bubbling are studied. In such treatments, specific tailored slag additives can be used for divergent steel grades to optimize steel cleanliness and inclusion engineering.