Investigation on Slag-Metal-Inclusion Multiphase Reactions During Electroslag Remelting of Die Steel

Experimental and theoretical studies have been carried out to investigate the effects of slag composition on the MgO center dot Al2O3 inclusion in ingot during the electroslag remelting (ESR) process with a focus on developing a mass-transfer model to understand the evolution mechanism of MgO center dot Al2O3 inclusion. H13 die steel was used as the electrode and remelted with two different kinds of slags by using a 30-kg ESR furnace. The inclusion compositions and contents of magnesium, silicon, and aluminum along the axial direction of product ingots were analyzed. On the basis of the unreacted core model as well as the penetration and film theories, the theoretical model developed in this work well elucidates the kinetics of slag-metal-inclusion reactions revealing the mechanism of inclusion evolution during the ESR process. The calculation results obtained from the model agree well with the experimental results. The model indicates that the inclusions of the outer MnS layer, which surrounds the MgO center dot Al2O3 core in the electrode, are disintegrated and removed during the metal film formation process at the tip of the electrode in the ESR furnace. The more CaO there is in the slag, the higher the aluminum and magnesium in the ingot and the lower the silicon. The concentration of MgO in the MgO center dot Al2O3 inclusion increases with the increase of CaO/SiO2 in the slag. The aluminum in the electrode has little effect on the MgO center dot Al2O3 inclusion compositions in the final product ingots.