As a result, the furnace slag and slag will be damaged, which will lead to the poor service life of the brick. In order to prolong the service life of MgO-C brick, the influence of LF slag on the corrosion resistance of MgO-C brick was studied, and the way to prolong the service life of MgO-C brick for LF slag line was discussed.

Experimental materials and process

Low iron slag and high iron slag used in LF furnace are selected in the experiment, and their composition is shown in the attached table. The magnesia carbon brick mt-14 of slag line currently used in Angang is selected.

After the magnesia carbon brick of slag line was made into crucible with inner diameter of Φ 60mm × 50mm and outer diameter of ф 120mm × 100mm, lf low iron slag and high iron slag were respectively put into the prepared crucible, and the slag corrosion resistance of magnesia carbon brick was tested by static crucible method at 1600 ℃ for 3 h. They grind two kinds of LF furnace slag into 200 mesh fine powder, press it into a Φ 6 mm × 5 mm cylindrical sample with thermoplastic phenolic resin as binder, put it on the gasket made of magnesia carbon brick of slag line, put it in the refractory detector drh-iii, observe the wetting angle of slag and magnesia carbon brick when the sample reaches the hemispherical temperature, so as to characterize the wettability of slag to magnesia carbon brick.

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Experimental results and analysis

Wetting angle detection. According to the diagram of wetting angle of two kinds of LF slags to MgO-C brick, the researcher calculates that the wetting angle of LF slag with less iron is 45 ° and that of LF slag with more iron is 58 ° to MgO-C brick. It can be seen that the two kinds of slag of LF furnace can wet the magnesia carbon brick, and the slag with less iron has more obvious wetting phenomenon and more obvious erosion on brick. Therefore, the slag composition of LF furnace can be adjusted in a certain range to increase the wetting angle of slag on products, so as to improve the corrosion resistance of magnesia carbon brick.

Analysis of slag erosion resistance. The SEM morphology of the magnesia carbon brick crucible corroded by the LF slag with less and more iron shows that a thin slag layer is formed on the surface of the magnesia carbon brick after being eroded by the LF slag, and the slag layer of the sample with less iron is relatively obvious. Due to the short erosion time, the erosion layer on the surface of MgO-C brick is thin after being eroded by two kinds of slag. At the same time, the flake graphite on the surface of MgO-C brick in contact with molten slag is oxidized and the matrix is loose. Moreover, the corrosion of low iron LF slag on magnesia carbon brick is obviously stronger than that of high iron LF slag, and the erosion layer is relatively deep. The reason is that the wetting angle of low iron slag on MgO-C brick is relatively small, and the wetting rate is fast under the same conditions, which accelerates the melting corrosion of MgO-C brick.

The researchers further found that LF slag first wetted the surface of MgO-C brick, then infiltrated into the matrix of MgO-C brick along the pores left by graphite oxidation, filled around the magnesia particles, and carried out chemical erosion with magnesia particles to form low melting point liquid phase containing Ca, Si and Al, thus gradually eating away the magnesia particles. It can be inferred that with the extension of reaction time, the cemented structure will be formed, the magnesia particles will be embedded in the liquid phase, and the edges and corners of magnesia particles will be eroded by molten slag and become smooth, so that the composition and properties of the eroded layer and the original layer of the magnesia carbon brick, especially the coefficient of thermal expansion, are greatly different. Under the condition of LF secondary refining, due to the high refining temperature, the viscosity of the slag decreases, and the inner temperature of the lining is also high, the slag can penetrate into the deeper part of the refractory and form a thicker reaction layer, which will aggravate the melting loss of the magnesia carbon brick lining, Severe spalling and flaking damage occurred. Therefore, the influence of LF slag on MgO-C brick is mainly manifested by chemical erosion and thermal shock, which leads to spalling damage.

Ways to prolong the service life of magnesia carbon brick for slag line

To sum up, the wetting angle of the two kinds of LF slags to MgO-C Bricks is less than 90 ° and it is easy to wet the surface of MgO-C Bricks. When contacting with MgO-C Bricks, the damage rate of MgO-C Bricks will be accelerated, and the wetting phenomenon of LF slag with low iron is more obvious. In the erosion experiment, the corrosion resistance of MgO-C brick in contact with low iron slag is reduced.

In order to prolong the anti slag corrosion life of Mg-C brick in LF furnace, a stable slag layer can be formed on the surface of MgO-C brick by adjusting the composition of slag and increasing the wetting angle of slag to prevent the oxidation of surface graphite and inhibit the wetting of slag on the surface of MgO-C brick, or by optimizing the matrix structure of MgO-C brick, the introduction form and amount of graphite in MgO-C brick can be improved and the base can be adjusted Therefore, the quantity, size, shape and distribution of pores formed by carbon oxidation in the process of using magnesia carbon brick will be affected by the composition of raw material, and the service life of magnesia carbon brick in LF slag line will be prolonged.