Good Oxidation Resistance Magnesia Carbon Refractory Brick for LadleMagnesia carbon brick production process 1.Selection of raw materials The raw materials for the production of MgO-C bricks are mainly magnesia. The technical requirements are high purity, few impurities, complete particle crystal development, uniform texture, low porosity and high volume density. Magnesia is divided into fused magnesia and sintered magnesia, but gradually replacing part of the sintered magnesia with fused magnesia can significantly improve the corrosion resistance. The carbon raw material generally uses natural flake graphite. It has no eutectic relationship with oxides such as MgO and does not form low-melting materials. It has high thermal conductivity, small elastic modulus, low thermal expansion coefficient, and is non-wetting. Binder is the key material for the production of MgO-C bricks. Its technical requirements: (1) The wetting angle for carbon materials is small and the affinity is good; (2) The residual carbon rate is high; (3) The impurities and moisture content are low. Commonly used binding agents include phenolic resin, modified phenolic resin and tar asphalt. Nowadays, most MgO-C bricks are produced using synthetic phenolic resin. Admixtures mainly include unit metals and multi-element metal powders such as Al, Mg, Si, Al-Mg, Al-Si, Al-Mg-Ca, carbon pure substances and complex alkalized substances such as B4C, Al8BC7, Al4SiC4, ZrB₂, MgB, CaB6 and other borides. 2.Proportion 5-1(3-1)mm magnesia 50~60%, <1mm magnesia 10%, <0.074mm magnesia + graphite + additives 30~40%, resin 5% (extra). 3. Practice The feeding sequence is generally magnesia particles - binder - graphite - magnesia fine powder and mixed fine powder of additives. And it is best to do it in a kneading equipment with a heating device, so that the resin has good flow properties and can achieve uniform distribution. 4. Forming When using a hydraulic press to produce MgO-C bricks, the pressure is generally required to reach 115~200MPa. The number of pressurization times cannot be less than 15 times. 5.Heat treatment MgO-C bricks are generally processed at a temperature of 200~250℃. The heating system is: 50~60℃, because the resin softens, it should be kept warm; 100~110℃, a large amount of solvent is discharged, so it should be kept warm; 200 or 250℃, in order to make the reaction Completely, should be kept warm. It is not difficult to see that the production of MgO-C bricks from raw materials to processes has reached its limit. Therefore, the improvement of the performance of existing MgO-C bricks will be slow and very limited. In addition, resources are limited. Since graphite is easily oxidized, the high-temperature reaction between magnesium chloride and graphite always exists, especially in a vacuum metallurgical environment. The redox reaction of MgO-C bricks and the redox reaction of oxide inclusions and carbon are determined by the nature of the material. The ease of oxidation of graphite is the dominant aspect that determines this nature. Therefore, artificial modification of graphite is an effective way to solve this problem. Only in this way can the chemical compatibility conditions of MgO-C bricks be further improved, thereby promoting the development of MgO-C bricks.
