Four Factors For The Production Of Magnesia Carbon Brick

Magnesia carbon brick is mde of magnesium oxide (melting point 2800 ℃) and carbon material with a high melting point that is difficult to be infiltrated by slags by adding a variety of non-oxide additives. It is mainly used in the converter, AC arc furnace, DC arc furnace lining, ladle slag lines and other parts.

The factors for the production of magnesia carbon brick incldue raw materials, binding agents and additives.

1) Magnesia sand

Magnesia sand should have high purity. Compared to sintered magnesia brick, fused magnesia brick has more complete crystal structure and stable reducing effect on carbon, so the production of magnesai brick turns to fused magnesia bricks. Given the binding state of carbon and infiltration of binding agents, fused magnesia can be mixed with sintered magnesia.

Magnesia carbon brick made of magnesia sand with high MgO content, large periclase particles and a lime-silica ratio of greater than 2 has the best quality.

2) Graphite

Graphite is another raw material for magnesia carbon bricks. it has good basic refractory properties. It contains 85%-98% fixed carbon and 13%-2% ash nd has a relative density of 2.09-2.23 and a melting point of 3640K ( volatile).

There are three reasons for the oxidization of graphite during use:

a. Oxygen in the air

b. Oxides in the slag

c. Oxides in graphite itself

Oxide impurities can react with graphite and make the structure loose, permeability increased and strength reduced, which is the main reason for the damage of magnesia carbon brick. Therefore, graphite with high purity and large flake crystals is mainly used for the production of magnesia carbon brick.

3) Binding agent

Binding agent is important for magnesia carbon brick and other carbon refractory products. Graphite and refractory oxides are not miscible. Thwy rely on binding agents to bond. At high temperature, the binding agent will be carbonized and form carbon bond with graphite. These binding agents are typically phenolic resins, modified bitumen, petroleum cracking by-products. Among them, phenolic resin has the best performance.

4) Additives

During the damaging process of magnesia carbon bricks, the oxidization of graphite is the main reason. The oxidation and carbon loss result in loose structure and weak strenth. In order to improve the oxidation resistance of magnesia carbon bricks, a certain amount of additives are added, including silica powder, alumina powder, FeSi alloy, CaSi alloy, SiC, Si3N4 and B4C. another function of additives is to build a bridge between refractory oxides and graphite and reinforce the binding between refractory oxides and graphite.