The common methods to reduce high temperature erosion of magnesium carbon bricks can be summarized as follows:
1. Select high-quality materials with stable composition to improve the material's erosion resistance, thermal shock resistance and structural spalling resistance
Select high-purity and high-quality fused magnesia sand, because it has the advantages of large grains, high density, low chemical activity, high erosion resistance, etc., and can resist the self-destructive reaction with carbon at high temperature, thereby inhibiting the erosion of MgO particles by slag. Secondly, increase the MgO content and reduce impurities, especially limit the SiO2 content, and reduce the silicate phase in the structural components of magnesia carbon bricks, so that side reactions such as the reaction of SiO2 with graphite at high temperature can be reduced and carbon oxidation can be avoided. In addition, increasing the degree of crystallization of MgO crystals can prevent the dissolution caused by the transformation of MgO grain boundaries into liquid phase at high temperature, and prevent further penetration of slag into magnesium refractory carbon bricks. Increasing the purity of graphite can also increase the slag resistance of magnesium carbon bricks, because with the increase of graphite purity, the thermal shock resistance of magnesia carbon fire bricks is improved, and the high temperature flexural strength is also significantly improved. Therefore, graphite with a carbon content greater than 95% is generally used. As the purity of graphite increases, other impurities decrease, and the silicate phase contained is also less. In the alkaline slag, SiO2 will react with the carbon in the magnesia carbon brick to form a decarburization layer, and can also form a low melting phase with magnesium oxide, ferrous oxide, etc. to accelerate the dissolution of magnesia carbon bricks. Finally, adding an appropriate amount of antioxidant to the magnesia carbon brick and selecting a high-quality thermosetting binder can also improve the high-temperature performance of magnesia carbon firebricks.
2. Optimize the composition of smelting slag
For magnesium carbon bricks refractory materials, the MgO content in the slag should be increased as much as possible to make the MgO in the slag reach a saturated state and reduce the dissolution of MgO. Since MgO is an alkaline oxide, increasing the slag alkalinity can reduce the chemical reaction between the slag and magnesium oxide and reduce the chemical erosion of magnesia carbon bricks. Reducing the content of FeO or other elements that may react chemically in the slag can reduce the oxidation of MgO and graphite by the slag;
3. Take external measures
Form a protective layer on the surface of the magnesia carbon brick by external means to prevent the magnesia carbon brick from contacting the slag, and prevent the physical penetration and chemical erosion of high-temperature molten steel/slag into the interior of the refractory material, such as splashing slag to protect the furnace. Magnesium carbon brick refractory materials can also be protected by external fields such as electric fields, magnetic fields, and ultrasonic fields. Among them, the external electric field cathodic protection method is a new technology for studying the resistance of refractory materials to high-temperature erosion of molten steel/slag in recent years, which has attracted widespread attention from scholars.
