2017 Volume 57 Issue 4 Pages 713-722
Based on the ion and molecule coexistence theory (IMCT) and slag-metal equilibrium theory, a thermodynamic model to design the slag compositions balanced with the consumable electrode of G20CrNi2Mo bearing steel during electroslag remelting (ESR) process was developed. With this model, an equilibrium slag system of Al2O3, SiO2, MnO and FeO can be obtained quantitatively, which is favorable to decrease the extent of steel constituents oxidized by the molten slag. In order to validate the reasonability of this model, an industrial experimental with four types of slag systems was carried out in a special steel plant of China. The composition variation of Al, Si, Mn and oxygen corresponds well with deviation of Al2O3, SiO2, MnO and FeO from equilibrium, reflecting the reasonability of this model. This model could also provide some guidance for deoxidation practice during industrial ESR process. It is concluded that large deviation of measured FeO from equilibrium is a key factor leading to the Al-oxidation and oxygen increase. In order to improve the cleanliness of refined ingot, under the premise of one slag system with relatively low CaO content, a feasible means is to strengthen the protecting atmosphere or add strong oxidizer into the slag pool to suppress the FeO-activity to a minimum level, particularly during the last stage of remelting.
