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Magnesia carbon bricks have two methods of making bricks: fired oil-impregnated magnesia carbon bricks and non-burned magnesia carbon bricks. The electric brick magnesia carbon brick furnace is converted to magnesia carbon brick. The brick making process of the former is relatively complicated, and it is rarely used. The magnesia carbon brick used for ladle will only briefly describe the brick making process characteristics of non-burning magnesia carbon brick.
Preparation of mud. For magnesia carbon brick manufacturers, the choice of the critical size of the particles during breeding is important. The aggregate particles are refined to reduce the open porosity and enhance the oxidation resistance. However, if the aggregate particles are small, the closed pores will increase and the bulk density will decrease. Further, the fine-grained MgO aggregate is easily reacted with graphite, and it is generally considered that the particle diameter of 1 mm is preferable. Under conditions of high pressure molding equipment, the particles of magnesia tend to be fine. The pressure of molding equipment in China is relatively low. In order to increase the density of refractory bricks, many manufacturers use particle diameters of more than 5 mm.
The quality and quantity of graphite added to the ingredients is critical. In general, increasing the graphite content of the refractory bricks will increase the slag resistance and thermal shock resistance of the refractory bricks, but the strength and oxidation resistance will be reduced. If the carbon content of the magnesia carbon bricks is too small (<10%), If the network skeleton cannot be formed in the refractory brick, the advantage of carbon cannot be effectively exerted. Therefore, the carbon content is suitable in the range of 10-20%.
In the mixing process, in order to uniformly surround the graphite around the magnesia particles, the order of addition should be: magnesia particles → binder → graphite → magnesia powder and additive powder. Since the graphite content is large, the density is small, and the amount of the additive is very small, it takes a long time to mix uniformly, but the mixing time is too long and the graphite and fine powder around the magnesia particles are easily detached, so the mixing time is appropriate.
The molding of magnesia carbon brick is an important factor to densify the structure of refractory brick: due to the large amount of graphite in the mud, the critical particles of the aggregate are small, so it is better to use high pressure molding and strictly follow the light and heavy weight, multiple pressurization operation. The procedure is suppressed to avoid forming cracks. The operating procedure of vacuuming and exhausting pressure is adopted. In addition, the surface of the high-pressure formed brick is very smooth, and it is easy to slide during handling and construction. Therefore, the formed brick should be impregnated or coated with a thermosetting resin of 0.1 to 2 mm to form a resin film to prevent sliding. This treatment is generally referred to as an anti-slip treatment.
The formed magnesia carbon brick must be hardened before it can be used, and the hardening treatment has a great influence on the performance of the refractory brick. It has been proved by research that the hardening treatment at 200-250 °C is suitable, and there are women in ensuring the bulk density of the brick and reducing the porosity. When the temperature is higher than 250 °C and lower than 200 °C, the hardening treatment will have adverse effects. It is necessary to strictly raise the air. Usually at 50-60 ° C, due to resin softening, should be properly insulated; at 100-110 ° C, due to a large amount of solvent discharge, should be insulated; live at 200-250 ° C, in order to make the reaction is complete, should also be properly insulated.