Improving Cleanliness of H13 Steel by Adding Rare Earth Oxide Into Refining Slag With Low Basicity

Molten steel cleanliness is critical for the performance and service life of H13 steel. CeO 2 with a range of 0–20 wt% was added into refining slag to improve the cleanliness of H13 steel in this study. The effects of the amount of added CeO 2 on the oxygen and sulfur contents and inclusion characteristics of molten steel were systematically investigated through high‐temperature experiments, Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and thermodynamic calculations. The optimum result was obtained at 5 wt.% CeO 2 , where the oxygen and sulfur contents decreased to 35 and 45 ppm, respectively, and the average inclusion size was reduced to 2.53 μm. The steel–slag reaction mechanism was analyzed in terms of slag melting behavior, polymerization properties, component activities, crucible corrosion, and the existential form of rare earth. The results indicate that the effect of CeO 2 on H13 steel cleanliness is mainly governed by polymerization properties of the refining slag, steel–slag reaction thermodynamics, and the transformation of CeO 2 into Ce 2 O 3 . Below 5 wt.% CeO 2 , improved polymerization properties and thermodynamic conditions enhance steel cleanliness. At 5–10 wt.%, partial conversion of CeO 2 to Ce 2 O 3 weakens deoxidation and desulfurization. Above 10 wt.%, deterioration of polymerization properties and continuous Ce 2 O 3 formation reduce steel cleanliness.