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When magnesia carbon bricks come into contact with molten steel and slag, the slag corrodes the magnesia carbon bricks, resulting in poor thermal shock resistance of magnesia carbon bricks, peeling and damage, which prolongs the service life of slag line magnesia carbon bricks and affects LF furnace refining consumption. In order to extend the service life of magnesia carbon bricks, researchers studied the influence of LF furnace slag on the corrosion resistance of magnesia carbon bricks, and discussed ways to extend the life of LF slag line magnesia carbon bricks. The raw materials and process of magnesia carbon brick price experiment were used in the experiment of low iron slag and high iron slag for LF furnace. Magnesium carbon bricks were selected from slag line magnesia carbon bricks MT-14 currently used by Anshan Iron and Steel. After the researchers made the slag line magnesia carbon bricks into crucible samples with an inner diameter of ф60mm×50mm and an outer diameter of ф120mm×100mm, they respectively loaded the LF low iron slag and high iron slag into the prepared crucibles, kept them at 1600℃ for 3h, and used the static crucible method to stop the slag corrosion resistance experiment of magnesia carbon bricks.
They ground two types of LF furnace slag into 200 mesh fine powder, used thermoplastic phenolic resin as a binder, pressed it into a ф6mm×5mm cylindrical sample, placed it on a gasket made of slag line magnesia carbon brick, placed it in the refractoriness tester DRH-III, and observed the wetting angle between the slag and the magnesia carbon brick when the sample reached the hemispherical temperature, so as to characterize the wetting function of the slag on the magnesia carbon brick. Experimental results and analysis of wetting angle detection. According to the wetting angle representation diagram of the two types of LF furnace slag on magnesia carbon brick, the researchers calculated that the wetting angle of the LF slag with less iron on the magnesia carbon brick is 45°, and the wetting angle of the LF slag with more iron on the magnesia carbon brick is 58°. It can be seen that both types of LF furnace slag can wet magnesia carbon bricks, and the wetting phenomenon of the slag with less iron is more obvious, and the corrosion of bricks is more obvious. Therefore, the composition of LF furnace slag can be adjusted within a certain range to increase the wetting angle of the slag on the product, thereby improving the corrosion resistance of magnesia carbon bricks. Analysis of slag corrosion resistance. The SEM morphology of the MgO-C brick crucible corroded by LF slag with less iron and more iron shows that after being corroded by LF slag, a thin slag layer is formed on the surface of the MgO-C brick, and the slag layer of the sample with less iron is relatively clear.
Due to the short corrosion time, the corrosion layer on the surface of the magnesia carbon brick is relatively thin after being corroded by the two slags. At the same time, the flaky graphite on the surface of the magnesia carbon brick in contact with the slag is oxidized, and the matrix is relatively loose. Moreover, the corrosion of the magnesia carbon brick by the low-iron LF slag is significantly stronger than that of the high-iron LF slag, and the corrosion layer is relatively deep. This is because the wetting angle of the low-iron slag to the magnesia carbon brick is relatively small, and the wetting rate of the magnesia carbon brick is fast under opposite conditions, thereby accelerating the melting of the magnesia carbon brick. The researchers further found that the LF slag first wets the surface of the magnesia carbon brick, and then invades the matrix of the magnesia carbon brick along the pores left after the oxidation of the graphite, fills around the magnesia sand particles, and stops chemical corrosion and melting with the magnesia sand particles to generate a low melting point liquid phase containing Ca, Si, and Al, thereby gradually eroding the magnesia sand particles.
It can be inferred that as the reaction time increases, a cementing structure will be formed in the magnesia carbon brick, the magnesia sand particles will be embedded in the liquid phase, and the edges and corners of the magnesia sand particles will be melted by the slag and become smooth, so that the composition and function of the corrosion layer and the original brick layer of the magnesia carbon brick, especially the thermal expansion coefficient, are very different. When subjected to thermal shock and thermal impact during use, the working surface of the magnesia carbon brick will peel off and flake off. Under the condition of LF refining outside the furnace, due to the high refining temperature, the viscosity of the slag is reduced, and the temperature inside the furnace lining is also high, the slag can penetrate deeper into the refractory material to form a thicker reaction layer, which will aggravate the melting loss of the lining of the magnesia carbon brick and cause serious peeling and flake off damage.
Therefore, the influence of LF slag on magnesia carbon bricks is mainly manifested in chemical corrosion and the resulting poor thermal shock resistance, resulting in peeling and damage. Ways to extend the life of magnesia carbon bricks for slag lines In summary, the wetting angle of the two LF furnace slags on magnesia carbon bricks is less than 90°, which is easy to wet the surface of magnesia carbon bricks. When in contact with magnesia carbon bricks, it will accelerate the damage rate of magnesia carbon bricks, and the wetting phenomenon of low-iron LF slag is more obvious. In the corrosion experiment, this phenomenon reduces the corrosion resistance of magnesia carbon bricks in contact with low-iron slag.
In order to extend the slag corrosion resistance life of LF furnace magnesia carbon bricks, we can start from adjusting the composition of slag, increasing the wetting angle of slag to magnesia carbon bricks, forming a stable slag layer on the surface of magnesia carbon bricks, preventing the oxidation of surface graphite, and inhibiting the wetting of slag to the surface of magnesia carbon bricks. Or by optimizing the matrix structure of magnesia carbon bricks, improving the introduction method and amount of graphite in magnesia carbon bricks, and adjusting the ingredient composition of the matrix, the number, size, shape and distribution of pores formed by carbon oxidation in the use process of magnesia carbon bricks are affected, thereby extending the service life of LF slag line magnesia carbon bricks.
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