Magnesium-carbon bricks are made of high melting point alkaline oxide magnesia (melting point 2800 C) and high melting point carbon materials which are difficult to be attacked by slag. Various non-oxide additives are added to the regenerative bricks. A non-burnt carbon composite refractory made of carbon binder. Magnesium-carbon brick is mainly used for lining of converter, alternating current arc furnace, direct current arc furnace, slag line of ladle and other parts. Magnesia chrome brick
As a kind of composite refractory, magnesia-carbon brick effectively utilizes magnesia's strong slag erosion resistance, high thermal conductivity and low expansion of carbon, and compensates for the biggest shortcoming of magnesia's poor spalling resistance.
Its main characteristics are as follows: 1. It has good high temperature resistance, 2 slag resistance, 3 thermal shock resistance, 4 high temperature creep and low temperature creep.
Effect of Raw Materials on Properties of Magnesium Carbon Bricks
The quality of magnesia plays an important role in the performance of magnesia-carbon bricks. How to select magnesia reasonably is the key to produce magnesia-carbon bricks. Magnesia has fused magnesia and sintered magnesia, which have different characteristics. Fused magnesia: large grain, less impurities, less silicate phase, high degree of grain direct bonding, less grain boundaries.
Sintered magnesia: fine grains, relatively more impurities and silicate phase, poor direct bonding degree
For magnesia raw materials, besides chemical composition, high density and large crystallization are also required in the aspect of structure. Therefore, as the quality index of magnesia raw materials for producing magnesia-carbon bricks, the following contents should be considered: 1. The types of impurities in magnesia content (purity) 2, especially the density, pore size and pore morphology of magnesia with C/S and B2O3 content 3, etc. (sintering property).
The purity of magnesia has a great influence on slag resistance of magnesia-carbon bricks. The higher the magnesia content, the less impurities, the lower the degree of silicate phase separation, the higher the direct bonding degree of periclase, the better the slag penetration resistance and the slag melting loss ability. The main juices in magnesia are calcium oxide, silicon dioxide, iron oxide,  If the impurity content is high, especially the boron oxide compound, the fire resistance and high temperature performance of magnesia will be adversely affected.
The main impurities in magnesia are as follows: 1. Reducing the direct bonding degree of periclase 2. Forming low melt 3 ferric oxide with magnesia at high temperature. Silica and other impurities react with carbon before magnesia at 1500-1800 C, leaving pore to make slag resistance of products worse.
For magnesia raw materials, besides the total amount of impurities, the type and relative content of impurities also have a significant impact on the properties of magnesia. Among them, CaO/SiO 2 ratio and B2O 3 content have the most obvious influence. Generally, magnesia refractories require CaO/SiO 2 or more to improve the high temperature stability of magnesia-carbon bricks.
Flake graphite is the main carbon material for preparing magnesia-carbon bricks.