Numerical study on the effect of vacuum on oxygen transfer in electroslag remelting process

Abstract

With increasing demands for high quality and ultra-low oxygen grade steel, the electroslag remelting process carried out under vacuum has been developed. A transient model coupling the magnetohydrodynamic flow, heat transfer and species transport was proposed to study the effect of vacuum on oxygen transfer during the electroslag remelting process. A reaction kinetic model was established to predict the mass transfer rates caused by the interfacial reactions. The predicted result agrees well with the experimental data. The oxygen is produced at the slag-metal interface due to the decomposition of Al2O3. The oxygen transfer is primarily achieved at the electrode-slag interface (ESI) and droplet-slag interface (DSI). The carbon deoxidization, which mainly occurs at DSI weakens the oxygen transfer from slag to steel, and can be promoted by lower pressure. The oxygen contents remelted under 101.325 kPa, 10 kPa and 1 kPa are 19.2 ppm, 15.5 ppm and 13.1 ppm, respectively. A low vacuum degree (no less than 10 kPa) is recommended regarding the stability of molten slag. The oxygen content increases from 14.3 ppm to 19.2 ppm with the carbon content ranging from 0.6% to 0.15%. The carbon deoxidization cannot occur when the carbon content is less than 0.15%.