Slag erosion of magnesia-carbon brick

The chemical erosion of magnesium-carbon brick by slag is mainly through the dissolution of magnesium-oxide and the oxidation of carbon in the matrix of magnesium-carbon brick, and under the joint action of the following factors, the damage of magnesium-carbon brick is caused

1. Influence of alkalinity: the lower the alkalinity of slag, the more favorable the erosion of magnesia-carbon bricks. If the alkalinity of slag increases, the activity of SiO2 in the slag decreases, which can reduce the oxidation of carbon; at the same time, with the increase of alkalinity, the activity of FeO in slag decreases, relatively slowing the erosion behavior of magnesia-carbon bricks by molten slag;

2. Influence of MgO: Osbom et al. found in the composition analysis of LF slag line that the content of MgO in the hanging slag layer was as high as 30%, and believed that the higher the content of MgO in slag, the slower the erosion of magnesia carbon brick and the higher the alkalinity, which also slowed down the erosion of magnesia carbon brick by slag.

3, the influence of Al2O3: Al2O3 in the slag will reduce the melting point and viscosity of the slag, increase the wettability of the slag and refractory, so that the slag is easier to penetrate from the magnesia grain boundary, so that the cubic magnesite is removed from the magnesia carbon brick matrix.

4, the influence of FeO: First of all, FeO in the slag is easy to oxidize the graphite in the magnesia carbon brick at high temperature, and produce bright white iron beads, forming a decarbonized layer, and secondly, the magnesia carbon brick will react with the FeO in the slag to produce low melting point products.

In the process of repeated heating and cooling of ladle, the magnesium oxide on the surface of refractory material is broken due to the inconsistent thermal expansion rate between the low melting point product of magnesia and magnesite, which leads to the dissolution of the brick. Foreign scholars also believe that the increase of iron content in steel slag is unfavorable to the life of magnesia-carbon brick, first of all, iron FeO accelerates the oxidation of carbon on the surface of magnesia-carbon brick, and secondly, FeO will react with MgO, making the working surface structure of magnesia-carbon brick loose, and under the joint action of these two points, the erosion of magnesia-carbon brick is accelerated.