Characteristics of magnesia carbon brick as refractory in China

The flake graphite has the following characteristics: 1. The melting point of type graphite is 3850 ℃± 50 ℃ and the boiling point is 4250 ℃. Even after being burned by electric arc, the mass loss and linear expansion coefficient of magnesia carbon brick are very small. The strength of graphite increases with the increase of temperature. At 2000 ℃, the strength of graphite is doubled. 2. Conductivity and thermal conductivity. The conductivity of graphite is twice as high as that of non-metallic minerals. The thermal conductivity is more than that of steel, iron, lead and other metal materials. The thermal conductivity decreases with the increase of temperature. Even at the high temperature, graphite is a hot body. 3. Lubricity. The lubricity of graphite depends on the size of graphite flakes. The larger the scale, the smaller the friction coefficient, the better the lubrication performance. 4. Chemical stability. Graphite has good chemical stability at room temperature. It can resist acid, alkali and organic solvent corrosion. 5. Plasticity. Graphite has good toughness and can be milled into thin sheets. 6. Thermal shock resistance. When graphite is used at high temperature, it can withstand the drastic change of temperature without damage. When the temperature changes suddenly, the volume of graphite changes little and no cracks will occur.

Binder plays the role of connecting matrix and particles. In the actual production and use process, matrix and binder system are two weak links of MgO-C brick.

The requirements of binder for producing magnesia carbon brick are as follows: 1. It has good viscosity and fluidity, and good wettability for magnesia and graphite. 2. The binder can further condense in the heat treatment process, so that the product has higher strength. 3. In the process of heat treatment, the binder will not cause excessive expansion and contraction of the products, so as to avoid cracking of the products. 4. The content of F.C is higher, and the carbon polymer after coking has good high temperature strength.

Generally, the binders used in the production of magnesia carbon brick include coal tar, coal tar, carbon resin, polyol, pitch modified phenolic resin, synthetic phenolic resin, etc.

The excellent performance of MgO-C brick depends on the existence of carbon in the brick. The oxidation of carbon in the process of use easily leads to the deterioration of product structure, which makes the slag invade into the brick along the crevice, erodes the magnesium oxide particles, and reduces the service life of the magnesia carbon brick. At present, the oxidation resistance of magnesia carbon brick is improved by adding antioxidants. According to thermodynamic data and service conditions, the possible condensed phase and vapor pressure of each gas phase can be determined. 2. The ability of each condensed phase to oxygen affinity was compared with the possibility of CO reaction. The microstructure of various tomb bricks was analyzed