Magnesia carbon brick is made of dead burned magnesia or fused magnesia and carbon material (mainly crystallized graphite) as raw materials, resin as binder to prepare pressure, after heat treatment. In order to improve the oxidation resistance, metal or other anti oxidants are often added to the magnesia carbon brick.
Among all the commonly used refractory oxides, MgO has the highest melting point, and MgO can form high melting point compounds or solid solutions with many oxides or slag components, and the low melting point temperature of binary system formed by MgO and some oxides is also very high. Therefore, the first choice of refractories for steelmaking should be magnesia refractories containing MgO.
With the development of iron and steel smelting, most of the magnesia refractories used are magnesia composite materials, such as magnesia carbon brick, magnesia calcium carbon brick, magnesia calcium brick, magnesia aluminum pointed stone brick, magnesia chrome brick, etc.
The application history of magnesia refractories is very long, but the coefficient of thermal expansion of magnesia brick is large, and it is easy to peel off. Magnesia carbon brick is developed by adding graphite on the basis of magnesia brick. Because the coefficient of thermal expansion of graphite is small and it is not easy to be wetted by slag, it can improve the spalling resistance of MGC brick, slow down the penetration of slag into the brick and improve its corrosion resistance.
At present, MgO-C brick has been widely used in steelmaking furnace and ladle. Some people attribute the role of carbon in preventing slag penetration to the following reasons:
(1) The wetting angle between carbon and slag is very large, so it can not be infiltrated by slag;
(2) The iron oxide in the slag is reduced to metal, which makes the slag viscosity increase.
In China and Japan, except for special cases, resin bonded magnesia carbon brick with carbon content of 12% ~ 20% is generally used. In Europe, most of the magnesia carbon bricks combined with asphalt are used, and the carbon content is generally about 10%. Low carbon magnesia carbon brick generally refers to a kind of material with total carbon content less than 8%, which is composed of magnesia and graphite by organic bond.
