The production process of high quality magnesia carbon bricks

1. Selection of raw materials

The raw materials for the production of magnesia carbon bricks are mainly magnesia, and its technical requirements are high purity, few impurities, complete grain crystal development, uniform texture, low porosity, and high bulk density. Magnesia is divided into fused magnesia and sintered magnesia, but gradually replacing part of sintered magnesia with fused magnesia can significantly improve the corrosion resistance. The carbon raw material is generally made of natural flake graphite. It has no eutectic relationship with oxides such as MgO and does not form low-melting substances. Its thermal conductivity is large, the elastic modulus is small, the thermal expansion coefficient is low, and it has the characteristics of non-wetting. Binder is the key material for the production of magnesia carbon bricks. Its technical requirements: 

(1) Small wetting angle to carbon materials, good affinity; 

(2)High residual carbon rate; 

(3) Fewer impurities and moisture content. Commonly used binders are phenolic resin, modified phenolic resin, and tar pitch. 

At present, most of the production of magnesia carbon bricks uses synthetic phenolic resin. The admixtures mainly include Al, Mg, Si, Al-Mg, Al-Si, Al-Mg-Ca, and other unit metals and multi-element metal powders, B4C, Al8BC7, Al4SiC4, and other pure carbon and composite alkali compounds, ZrB₂, MgB, CaB6, and other borides.

2. Mixing

The feeding sequence is generally magnesia particles - binder - graphite - mixed fine powder of magnesia fine powder and additives. And it is best to carry out the mixing equipment with a heating device so that the resin has good fluidity and can achieve the purpose of uniform distribution.

4. Molding

When using a hydraulic press to produce magnesia carbon bricks, it is generally required to reach a pressure of 115~200MPa. The number of times of pressure should not be less than 15 times.

5. Heat treatment

Magnesia carbon bricks are generally treated at a temperature of 200~250°C. The heating system is 50~60°C, because the resin softens, it should be kept warm; 100~110°C, a large amount of solvent is discharged, and it should be kept warm; 200 or 250°C, in order to make the reaction Completely, should be insulated.

It is not difficult to see that the production of magnesia-carbon bricks has entered a limited state from raw materials to processes. 

The redox reaction of magnesia-carbon bricks and the redox reaction of oxide inclusions and carbon are determined by the nature of the material. The easy oxidation of graphite is the dominant aspect that determines this nature. Therefore, artificial modification of graphite is an effective way to solve this problem. Only in this way can the chemical compatibility conditions of magnesia carbon bricks be further improved, thereby promoting the development of magnesia carbon bricks.