The interaction between molten iron and refractory is of great significance to understand the damage of refractory in steelmaking processes. In this work, the interactions between the molten iron and three kinds of magnesia aggregates: No. 1 containing CaZrO3-ZrO2 intergranular phase (mainly CaZrO3), No. 2 containing ZrO2-MgAl2O4 intergranular phase (mainly ZrO2) and No. 3 fused magnesia, were studied by the sessile drop method at 1823 K under two kinds of oxygen partial pressures of PO2 ≈ 1.87 × 10−1 Pa and PO2 ≈ 1.87 × 10−3 Pa. It was found that the interaction mechanism between molten iron and substrate was almost the same under the two oxygen partial pressures. No. 2 substrate had a larger interacted area with molten iron due to its physical properties and chemical composition and more amount of slag was formed between them. The oxygen was easy to be released from the closed pores in No. 2 substrate so that the molten iron on No. 2 substrate had higher oxygen content, resulting in the decreases of the contact angle and the surface tension of molten iron. Accordingly, No. 2 substrate was penetrated most seriously. The intergranular phase of No. 1 substrate was more resistant to FeO corrosion than that of No. 2 substrate. The FeO penetration into No. 3 substrate was mainly along the grain boundary. The larger bulk density and grain size of No. 3 substrate could reduce the FeO penetration.
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