Estudo do desgaste do refratário de MgO-C da linha de escória de panelas de aço

Abstract

This study investigates the performance of magnesia-carbon (MgO-C) refractory materials applied to the slag line of steel ladles, a critical stage in secondary refining during steel production. The main objective was to evaluate the corrosion resistance of these materials against slags typical of the ArcelorMittal Monlevade process, correlating their microstructural characteristics with operational performance. Six commercial samples were analyzed through microstructural characterization (optical microscopy, scanning electron microscopy, and X-ray diffraction), physical tests (bulk density and apparent porosity), and performance tests (oxidation and static/dynamic corrosion). The characterization revealed significant differences among materials, particularly regarding magnesia quality (fused vs. sintered), crystal distribution, impurity content (predominantly calcium oxide and silicon dioxide – CaO and SiO2), and the presence of antioxidant additives. Results showed that materials composed exclusively of fused magnesia (T1, T2, and T5) exhibited superior overall performance, with lower porosity evolution after thermal treatment and higher corrosion resistance. The presence of metallic Si as an antioxidant in samples T3 and T5 contributed to reducing oxidation rates, while materials with sintered magnesia (T4 and T6) displayed greater wear and chemical instability due to lower crystal size and higher impurity levels. Static corrosion tests indicated that acidic slag was more aggressive than basic slag with fluorite addition, with material T5 being the most resistant, followed by T1 and T2. Dynamic tests showed minimal measurable wear, suggesting the need for more representative methods, such as induction furnace tests, to simulate real operating conditions. In conclusion, proper selection of slag-line refractories should consider magnesia purity, crystal size, microstructural distribution, and antioxidant presence, as these factors directly impact service life and operational safety. This work provides technical insights to optimize refractory selection, reduce costs, and enhance process reliability.