Flake graphite has the following characteristics

1. The melting point of high temperature resistant graphite is 3850 ℃± 50 ℃, and its boiling point is 4250 ℃. Even after being ignited by ultra-high arc, the mass loss and linear expansion coefficient are very small. The strength of graphite increases with the increase of temperature. At 2000 ℃, the strength of graphite doubles

2. Conductivity and thermal conductivity. The conductivity of graphite is twice as high as that of non-metallic ores. The thermal conductivity exceeds that of steel, iron, lead and other metal materials. The thermal conductivity of graphite decreases with the increase of temperature, and even at high temperature, graphite is an insulator.

3 lubricity. The lubricity of graphite depends on the size of graphite flake. The larger the flake, the smaller the friction coefficient and the better the lubricity

4. Chemical stability. Graphite has good chemical stability at room temperature. It is resistant to acid, alkali and organic solvent

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 there is no crack.

Binder plays a 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 for the production of magnesia carbon brick are as follows:,

1. It has certain viscosity and fluidity, and has good wettability for magnesia and graphite

In the process of heat treatment, the binder can further condense to make the products have higher strength

3. During heat treatment, the binder will not cause excessive expansion and contraction of the products, so as to avoid product cracking

The content of 4f. 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 are coal tar, coal tar, special carbon resin, polyol, pitch modified phenolic resin, synthetic phenolic resin, etc.

Antioxidant

The excellent performance of MgO-C brick depends on the existence of carbon in the brick. The oxidation of carbon in the process of its use is easy to cause the deterioration of product structure, so that the slag intrudes into the brick along the gap, erodes the MgO particles, and reduces the service life of MgO-C brick. At present, the main way to improve the oxidation resistance of magnesia carbon brick is to add antioxidants

Principles of antioxidant selection

According to the thermodynamic data and operating conditions, the possible condensed phase and the vapor pressure of each gas phase can be judged

2. Compare the affinity of each condensed phase to oxygen and the possibility of CO reaction.

3. Analysis of the influence of the microstructure of various tombs