In the previous steelmaking process, researchers mostly considered the production process, constantly improved the process, controlled the number of inclusions and how to effectively remove inclusions, but always ignored the impact of refractory materials in steelmaking. Refractory materials are in direct contact with molten steel, resulting in researchers always finding more or less inclusions in the molten steel no matter how they improved the process, and the resulting steel products were crude steel. The reason is that in the process of contact with molten steel, refractory materials are constantly eroded and penetrated by molten steel, causing structural damage. Finally, refractory materials enter the molten steel in the form of inclusions, reducing the content of inclusions in the molten steel, causing adverse effects and reducing the quality of steel.
The damage of refractory materials is mainly caused by slag erosion at the slag line, thermomechanical spalling and erosion of refractory materials by molten steel. The damage of refractory materials will inevitably have an adverse effect on the quality of steel. Over the years, workers in the steel industry have continuously conducted in-depth research on the slag resistance and thermal shock stability of refractory materials and have achieved remarkable results.
Four kinds of magnesium-aluminum spinel powder with different Al2O3 contents were used as raw materials, and pulp waste liquid was used as a binder. After being mixed and pressed into shape, the mixture was dried and heat-treated at 1600℃ for 3h. Then, the experiment was carried out at 1600℃. Ladle slag was used as the erosion medium in the experiment. The experiment lasted for three hours. After the experiment, the samples were processed and analyzed under a scanning electron microscope to observe the changes in the microstructure of the samples after erosion. The experiment found that the samples showed different laws in terms of slag erosion resistance and slag penetration resistance. The factor affecting the changes was the content of alumina in magnesium-aluminum spinel. When the content of alumina in spinel decreased, the sample’s ability to resist slag penetration gradually weakened, and the sample’s ability to resist slag erosion gradually increased. In the erosion test, the generated new phases of magnesium-iron solid solution phase and magnesium-iron spinel can prevent further penetration and erosion of slag, protect the original layer of refractory materials, and extend the service life of refractory materials.
The corrosion mechanism of magnesia carbon bricks was analyzed with the help of magnesia carbon bricks used on-site in steel plants. By comparing the use of magnesia carbon bricks in the slag line of the refining ladle using methods such as microstructural analysis, reaction thermodynamics analysis, energy spectrum analysis, and material wettability, the study found that there are differences in the corrosion and damage mechanisms of magnesia carbon bricks. This is mainly caused by differences in the temperature of the molten steel and molten slag that the magnesia carbon bricks contact and their own structures. In areas with higher temperatures, the impact is more serious. The wettability of magnesia carbon bricks in the slag increases, thereby fully increasing the internal structure of the slag and magnesia carbon bricks. The increase in contact area leads to an increase in the dissolution rate of magnesia carbon bricks, which in turn leads to an increase in the corrosion and damage of magnesia carbon bricks. The formation of a decarburized layer in magnesia carbon bricks is the main factor that directly leads to the increase in wettability.
With fused white corundum, graphite and silicon powder as the main raw materials, Sialon combined with Al2O3-C material was in situ generated at 1450℃ for 4 hours in a nitrogen atmosphere, and the anti-slag experiment was carried out at 1600℃ using the static crucible method. The microstructure and composition of the material after slag corrosion were analyzed by XRD and SEM-EDS. The results show that the penetration of slag is mainly along the edge of the corundum particles. With the deepening of penetration, the CaO content decreases continuously. The products generated after high-temperature nitridation of Al2O3-C material are oxidized and dissolved in the slag, which can reduce the erosion and penetration of the slag.
When studying the law of direct interaction between molten steel and refractory materials, we can refer to the erosion and damage mechanism of high-temperature slag and refractory materials. However, the reaction between molten steel and refractory materials is more direct and obvious. The interaction is mainly controlled by several factors. The first is the structure and strength of the material itself. The greater the strength, the stronger its stability. The second is the surface tension between the refractory material and the molten steel.
The erosion of molten steel on refractory materials and the chemical reactions occurring in the penetration and contact parts of refractory materials are all interactions between molten steel and refractory materials. These interactions will eventually cause the refractory materials to peel off and enter the molten steel. Not only the quality of steel is affected, but also the refractory materials are damaged, which restricts the service life of refractory materials.
However, there has been no breakthrough in the erosion of molten steel. Many scholars only study the interaction between molten steel and refractory materials from a static perspective, which is very different from the actual steelmaking process. Therefore, studying the erosion and damage of molten steel on refractory materials is a difficult problem that needs to be solved urgently.
