Design, preparation, and application of new functional refractories

Every significant technical advancement of the steel industry has depended on the support of refractories used as lining materials in various smelting containers. With the increasing demand for high-quality steels, the precise control of inclusions has become increasingly important. Existing technologies and equipment can effectively reduce the amount and average size of inclusions, but they cannot guarantee the complete removal of large-sized ones. In the steel-making process, refractories in close contact with molten steel are a main source of large-sized non-metallic inclusions; these can become bottlenecks, restricting improvements in steel quality. Based on this problem, the design, preparation, and application of new functional refractories become a critical focus for further development in the steel industry. These refractories are required to possess not only excellent thermo-mechanical properties (i.e., zero or reduced contaminant for the molten steel), but also the ability to remove inclusions with a high melting point in molten steel. However, available refractories are in their primary stages depending on experience, resulting in no breakthroughs in the precise control of inclusions, and even contamination of molten steel. This study focused on two new refractory materials, namely large-sized Al₄SiC₄ with controllable morphology, and Al₂O₃−MgO−CaO (CMA) with a ternary-layer structure. Preliminary experiments show that, with the introduction of the large-sized Al₄SiC₄, oxidation resistance of MgO−C bricks is improved, and the loose structure resulting from the oxidation of carbon-containing materials can be repaired. CMA materials not only possess excellent thermo-mechanical properties and high slag resistance, but also can produce refining slag phases with a low melting point. This can contribute to the floating of inclusions, thus exhibiting the potential for purifying molten steel. These new, functional refractories should offer strong support for the further development of high-quality steels.