摘要: Pure magnesia filter and periclase-spinel filter were prepared using porous MgO powder and Al₂O₃ micro-powder as raw materials. The filtration efficiency and purification mechanism of the two sets of filters on molten steel were investigated through steel casting tests. The results show that on the basis of surviving the thermal shock of molten steel, both filters can significantly reduce the number of non-metallic inclusions and total oxygen content of steel, thereby improving the cleanliness of the molten steel. After the thermal shock of molten steel, cracks were found in the microstructure of pure magnesia filter. Via the diffusion of non-metallic inclusions from steel into MgO grains of the filter to form solid solution, the inclusions were adsorbed to the internal and external surfaces of the pure magnesia filter. The number of inclusions was reduced by 62.5%, and the total oxygen content decreased from 0.892 to 0.265 wt.% after filtration, achieving a filtration efficiency of 70.3%. Compared with the pure magnesia filter, no cracks were found in the microstructure of the periclase-spinel filter. The mass transfer rate was accelerated due to the diffusion of inclusions from steel into MgO and MgAl₂O₄ grains of the filter, as well as the higher high-temperature liquid content and smaller pore structure of the filter. More non-metallic inclusions were able to enter the interior of the filter, which made the periclase-spinel filter more capable of adsorbing inclusions from steel and reducing total oxygen content. The periclase-spinel filter reduced the number of inclusions in steel by 84.4% and decreased the total oxygen content of the steel from 0.892 to 0.119 wt.%, with a filtration efficiency of 86.7%, demonstrating excellent comprehensive performance.