Features of magnesia carbon brick

There are two kinds of brick-making methods for magnesia-carbon bricks: fired oil-impregnated magnesia-carbon bricks and unburned magnesia-carbon bricks. The former brick-making process is more complicated and is rarely used. Here, only the characteristics of the brick-making process of unburned magnesia-carbon bricks are briefly described. Burnt magnesia brick

Preparation of mud. The choice of particle critical size is important during breeding. Refinement of aggregate particles can reduce open porosity and enhance antioxidant capacity. However, the small aggregate particles will increase the closed pores and reduce the bulk density. In addition, fine-grained MgO aggregates are easy to react with graphite, and it is generally considered that the particle size of 1 mm is suitable. Under the condition of high pressure molding equipment, the particles of magnesia tend to be micronized. The pressure of molding equipment in my country is low. In order to increase the density of refractory bricks, many manufacturers use particle diameters of more than 5mm.

The quality and quantity of graphite added to the ingredients are critical. Generally speaking, increasing the graphite content in the refractory brick will improve the slag resistance and thermal shock stability of the refractory brick, but the strength and oxidation resistance will decrease. If the network skeleton cannot be formed in the refractory brick, the advantages of carbon cannot be effectively exerted. Therefore, the carbon content is more suitable in the range of 10-20%.

During the mixing process, in order to make the graphite evenly surround the magnesia particles, the feeding sequence should be: magnesia particles → binder → graphite → magnesia fine powder and additive powder. Due to the large graphite content, low density and very small amount of additives, it takes a long time to mix evenly, but if the mixing time is too long, the graphite and fine powder around the magnesia particles will easily fall off, so the mixing time should be appropriate.

The molding of magnesia-carbon bricks is an important factor to densify the structure of the refractory bricks: due to the large amount of graphite in the mud and the small critical particles of the aggregates, it is advisable to use high-pressure molding and strictly follow the operation of light first and then heavy, and multiple pressurization operations. Suppressed regularly to avoid forming cracks. The operating procedures of vacuuming, exhausting and pressurizing are adopted. In addition, the surface of the high-pressure molded brick is very smooth, and it is easy to slide during transportation and construction, so the molded brick should be impregnated or coated with a 0.1-2mm thick thermosetting resin to form a resin film to prevent sliding. This treatment is generally referred to as anti-slip treatment.

The formed magnesia-carbon bricks must be hardened before they can be used, and the temperature of hardening has a great influence on the performance of refractory bricks. Studies have shown that the hardening treatment at 200-250 °C is more suitable, and the bulk density of bricks and the reduction of porosity are all good. When the temperature is higher than 250 °C and lower than 200 °C, the hardening treatment will have adverse effects. Strictly ascend and control the air. Usually at 50-60 ℃, due to the softening of the resin, it should be properly kept warm; at 100-110 ℃, due to the large amount of solvent discharged, it should be kept warm; at 200-250 ℃, in order to make the reaction complete, it should also be properly kept warm.