Compositional Optimization of ESR Slags for H13 Steel Containing Ce and Mg

Ce and Mg elements are vulnerable to burn off during the electro-slag remelting (ESR) process. To address this challenge, eight CaF2-based ESR slags with varying Ce2O3, MgO, CaO, and Al2O3 contents were designed and evaluated for their ability to retain Ce and Mg when contacted with H13 steel containing high amounts of these elements at 1600 & DEG;C using a tube furnace. The hemispherical temperature and viscosity of these slags were also measured. Ce and Mg contents in the liquid steel decreased rapidly with the extension of reaction time. The final Ce content at 60 minutes was sensitive to Ce2O3, Al2O3, and CaO contents in the slag, while the final Mg content was sensitive to MgO and Al2O3 contents. The final Ce and Mg contents were within the range of 5 to 44 and 21 to 59 ppm, respectively. Both measured Ce/O mass ratio and thermodynamical results reveal that soluble Ce content in equilibrium with slags is extremely low. Thermodynamic calculations indicate that when CaO content exceeds 7.5 wt pct, the equilibrium Ce and Mg contents are determined by Al2O3 in the slag, and otherwise by SiO2. To produce H13 steel containing Ce and Mg, the recommended ESR slag composition is CaF2-10 to 30 wt pct Ce2O3-10 wt pct MgO-20 wt pct CaO.