Flake graphite has the following characteristics: taphole repair material

1. The melting point of high temperature resistant graphite is 3850 ℃± 50 ℃ the boiling point is 4250 ℃. Even if the price of magnesia carbon brick is burned by ultra-high arc, the quality loss is very small, the coefficient of linear expansion is also very small. The strength of medium grade magnesia graphite increases with the increase of temperature, the strength of graphite is doubled at 2000 ℃

2. Conductivity 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 other metal materials. The thermal conductivity decreases with the increase of temperature. Even at very high temperature, graphite is an insulator.

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 organic solvent corrosion

5. Plasticity. Graphite has good toughness 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 no cracks will occur.

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

Taphole repair material

The requirements of binder for producing magnesia carbon brick are as follows,

1. It has a certain viscosity fluidity at room temperature, has good wettability for magnesia 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 cause excessive expansion contraction of the products, so as to avoid cracking of the products

4. C content should be high, the carbon polymer after coking has good high temperature strength

Generally, the binders used in the production of MgO-C brick include 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 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, reduces the service life of the magnesia carbon brick. At present, the oxidation resistance of magnesia carbon brick is improved by adding antioxidants

Principles of selecting antioxidants

1. Determine the possible condensed phase vapor pressure of each gas phase according to the thermodynamic data service conditions

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

3. Analyze the influence of various reactions on the microstructure of brick