The raw materials for making magnesia-carbon bricks are high quality sintered magnesia, fused magnesia, graphite, binders and antioxidants.
The periclase particles in magnesia play an aggregate role in refractory bricks. In order to produce high-quality and high-strength magnesia-carbon bricks, magnesia-chrome bricks, magnesia-zirconia bricks need to choose high-purity magnesia (MgO content is as high as possible, CaO/SiO 2 is more than 2, volume density is more than 3.34 g/cm 3, crystallization is well developed, and the porosity of magnesia itself is less than 3%).
Graphite is also the main material of magnesia-carbon bricks. Its fixed carbon content, ash composition, oxidation resistance, particle size, shape, volatile matter and moisture all directly affect the performance and use effect of magnesia-carbon bricks. It is better to choose high purity flake graphite or flake graphite brick with high carbon content (C < 95 - 96%) to ensure the corrosion resistance, peeling resistance, high temperature strength and oxidation resistance of magnesia-carbon brick.
Use of Magnesium Chromium Bricks
The binder used for magnesia-carbon bricks is very important, and its quality largely affects the production and quality of refractory bricks.
There are many kinds of materials that can be used as binders for magnesia-carbon bricks, such as coal tar, coal tar and petroleum asphalt, special carbon resin, polyols, asphalt modified phenolic resin, synthetic resin, etc. Phenolic resin is still a good binder for producing magnesia-carbon bricks because of its high carbon residue rate, good affinity with magnesia and graphite, easy to combine magnesia and graphite, and easy to spread in magnesia and graphite at room temperature.
Due to the use of high-purity graphite in magnesia-carbon bricks, the liquid phase produced in bricks is less, oxygen is easy to penetrate into the bricks to oxidize and decarbonize graphite, and the oxidation resistance of bricks is poor. Therefore, antioxidants such as metal A1, Si, A1-Si, Al-Mg alloy and SiC must be added. They can react with oxygen preferentially to form carbides or oxides, and expand in volume, plug or fill the pores to make bricks dense, thus improving the oxygen resistance of refractory bricks.