Effect of Refractory Crucibles on Inclusions in Ce-Containing High-Aluminum Steel

Abstract

With the advancement of aerospace, military and related industries, there is a persistent escalation in the performance requirements for steel. According to the actual smelting conditions, this study focuses on Ce-containing high-aluminum steel and various refractories as its research subjects. A combination of laboratory experiments and thermodynamic calculations is employed to investigate and compare the evolution mechanism of oxide inclusions in molten steel. The use of Al₂O₃ refractory results in an increase in [Al] content, whereas both MgO refractory and MgO–MgO·Al₂O₃ refractory lead to a decrease in [Al] content. Additionally, following the utilization of MgO refractory and MgO–MgO·Al₂O₃ refractory, the molten steel exhibits the higher [Ce] content than when Al₂O₃ refractory are employed (t = 30 minutes). Before the introduction of Ce element, the principal oxide inclusions in Al₂O₃ refractory and MgO-containing refractory are Al₂O₃ and MgO·Al₂O₃ inclusion, respectively. After adding cerium-aluminum alloy, [Ce] in the molten steel replaces the element of Al in the Al₂O₃ inclusion, transforming into CeAlO₃, while [Ce] replaces the Mg element in the MgO·Al₂O₃ inclusion, evolving into Ce–Mg–Al–O, which further reacts to form CeAlO₃ and Ce₂O₂S. Over time, the number density of inclusions first increases then gradually diminishes with various refractories. MgO refractory minimizes the number density of inclusions to 53.05 mm⁻². Moreover, the number of small size inclusions in MgO–MgO·Al₂O₃ refractories is the largest, and inclusions less than 3 μm account for 78.63 pct of the total number.