Slag Corrosion Resistance of MgO-C Refractories for Ladle Slag Line

MgO-C refractories are widely used in ladle, converter, electric furnace and other steel-making equipments due to their excellent slag corrosion resistance, which have met the requirements of steel-making industry in a long period. With the development of low carbon metallurgy, the high scrap ratio metallurgy has attracted the attention of steel-making industry due to its remarkable effect of energy saving and CO2 emission reduction. However, the addition of scrap reduces the viscosity of slag, changes the chemical compositions of slag, leads to the increase of corrosion ability, which poses a severe challenge to the slag corrosion resistance of refractories. In addition, low carbon MgO-C refractories are paid attention due to their advantages in low-carbon steel production, saving graphite resources, and reducing energy loss. However, its graphite content is low, resulting in poor slag corrosion resistance compared with traditional high carbon refractories. Therefore, it is urgent to improve the slag corrosion resistance of MgO-C refractories to meet the requirements of steelmaking industry. Slag corrosion resistance of eight typical commercial MgO-C refractories products were tested in laboratory conditions to investigate their corrosion mechanisms and provide reference for subsequent research. The results showed that the slag corrosion resistance of high carbon MgO-C refractories was significantly stronger than that of low carbon MgO-C refractories, and no decarburized layer could be found in corroded high carbon refractories. Enhancing oxidation resistance, reducing apparent porosity, enhancing the proportion of indirect dissolution, and increasing the slag viscosity were effective approaches to improve the slag corrosion resistance of MgO-C refractories. Then, slag corrosion resistance of low carbon MgO-C refractories reinforced with CMA aggregate and SiC was investigated. The CaAl2O4 phase in the CMA aggregate transformed into Al2O3-containing liquid phase, which mixed with the slag and increased the Al2O3 content of the slag. MgAl2O4 spinel was formed at the slag-refractories interface and formed a high-viscosity solid-liquid mixture with liquid slag, promoting the formation of protective slag layer. SiC was potentially suitable additive which enhanced both slag corrosion resistance and oxidation resistance. Furthermore, the slag corrosion resistance of high carbon MgO-C refractories reinforced with sintered MgAl2O4 spinel powder was studied. The results show that the matrix was the weak point of the MgO-C refractories in facing slag corrosion, while aggregates were less affected by the slag. Adding sintered spinel powder enhanced the matrix's slag corrosion resistance and reduced the corrosion rate. The MgAl2O4 spinel powder also formed Mg(Al, Fe)2O4 spinel, which absorbed Fe2+ and Mn2+ in the slag, reducing the slag's penetrability. In the end, a new type of MgO-C refractories product for ladle slag line was developed based on the above works and results, and it showed significant advantages in industrial applications. The average service life of the new MgO-C refractories product reached 102 cycles, with a residual thickness of 120mm, which could meet the requirements of industrial applications.