Magnesia-calcium-carbon bricks have many excellent properties and are widely used in out-of-furnace refining. However, there are still some problems in the use of magnesia-calcium-carbon bricks.
Magnesia calcium carbon brick
1. High temperature reaction of magnesium oxide and resistance to slag penetration
MgO in the magnesium-calcium-carbon refractory matrix is easy to react with C in the matrix when the temperature reaches 1500°C. The reaction becomes violent when the temperature reaches 1600°C. MgO is reduced to Mg vapor, and C is oxidized to CO gas. Escaping from the adobe makes the adobe seriously weightless, which is one of the important reasons for the damage of Mg-C bricks.
MgO+C→Mg(g)+CO(g)
In addition, during the use of magnesia-calcium-carbon bricks, the SiO2 in the slag first reacts with free CaO to form C2S and C3S, and their formation can increase the viscosity of the slag, making it difficult for molten slag to penetrate further into the magnesia-calcium-carbon bricks. However, the graphite on the surface of the adobe is oxidized, which leads to the decarburization of the surface layer to form voids, which makes the slag further penetrate into the inside of the adobe, and the MgO in the magnesia-calcium sand reacts with the CaO-SiO2 slag to form a MgO-CaO-SiO2 low-melting phase, so MgO is magnesium Calcium carbon bricks are the weak link of anti-slag erosion.
MgO is a relatively weak link in magnesia-calcium-carbon refractories, so it is necessary to reduce the content of MgO in magnesia-calcium-carbon bricks, to a certain extent suppress the weight loss problem caused by the reaction of MgO with C at high temperature; and use CaO to form a continuous phase distribution Magnesia-calcium sand, so that MgO does not react directly with CaO-SiO2 slag.
Generally, when fused magnesia-calcium sand is selected as the raw material of magnesia-calcium sand, a continuous phase is formed relative to the CaO grains of sintered magnesia-calcium sand to wrap the MgO grains, which can protect MgO. And the fused magnesia-calcium sand is denser than the sintered magnesia-calcium sand, which also strengthens the slag penetration resistance of magnesia-calcium bricks. However, the CaO grains of sintered magnesia-calcium sand are covered by MgO grains, which makes it difficult for CaO to come into contact with the air and be hydrated by water vapor in the air. However, fused magnesia-calcium sand just has the disadvantage that CaO is easy to hydrate, and sintering Magnesia-calcium sand is more economical than fused magnesia-calcium sand. Therefore, choosing different types of magnesia-calcium sand raw materials has its own advantages and disadvantages.
Magnesia calcium sand