The production process of magnesia carbon bricks is not complicated, but to produce high-quality products, each process link must be strictly monitored, among which mixing, molding, heat treatment (drying) are particularly important in production.
01 Crushing Crushing is the process of processing large pieces of material into ideal particle size materials. It is an indispensable process in the production of refractory materials. Although it is simple, it is very important. It has an important impact on the stability of product quality. At the same time, the crushing equipment has high power consumption, high wear and tear, and high maintenance rate, so the maintenance cost is high. Pay attention to crushing, stabilize product quality, save energy and reduce consumption. The purpose of crushing in the production of magnesite carbon bricks is mainly to prepare raw materials of various particle sizes. Increase the specific surface area of the material and destroy the material lattice to make it defective, thereby accelerating the physical and chemical reaction rate of the material.
02 Batching (weighing) Batching is the process of combining different raw materials and different particle components according to the product formula design. The batching method varies according to the type and state of the raw materials. The weight batching method is usually used in the production of magnesia carbon bricks because the weight batching method has high accuracy and generally does not exceed 2%. Commonly used weight batching equipment includes manual weighing scales, automatic weighing scales, weighing cars, etc. The corresponding equipment is selected according to the requirements and automatic control level.
03 Preparation of mud (mixing, mixing)
The purpose of mixing is to make the material composition uniform and to maximize the contact surface between different materials. The mixing of refractory materials is a method of homogenizing materials accompanied by extrusion, kneading, and exhausting. Like any mixing of powders, the mixing of refractory materials is also carried out step by step, and the mixing process is more complicated due to the different components, particle sizes, binders and admixtures of the materials. There are many types of magnesia carbon fire bricks. The formula is different according to the different parts of their use. The main changes are the quality of magnesia sand, the amount of graphite added, and the type and amount of additives. For example, in the slag line of the ladle, in order to improve the slag resistance and thermal shock stability of magnesia carbon bricks, the quality and amount of graphite added must be increased. If the carbon content is less than 10%, a continuous carbon network cannot be formed inside the magnesia carbon brick, and the characteristics of carbon cannot be fully exerted, affecting the slag resistance and thermal shock resistance of the magnesia carbon brick. If the carbon content is too high, it will not only bring difficulties to the production of magnesia carbon firebricks, but also make magnesia carbon refractory bricks easy to oxidize. Therefore, the carbon content in mgoc bricks is generally controlled between 10% and 20%. In order to make the magnesia sand particles evenly wrapped with graphite, the mixing process is generally carried out in the following steps: first, the granular material, then the resin, then the graphite, and finally the fine powder and various additives. Graphite has a small density, is easy to float, and the amount added is large, so it is not suitable for mixing, and the amount of additives added is very small, so if you want to mix the whole material evenly, you must stir it for a long time and at high intensity. However, the binder will evaporate and dry during the mixing process. If the time is too long, the graphite and fine powder wrapped on the particles will fall off, so the mixing time must be controlled.
04 Molding
There are many different molding methods for refractory materials. Magnesium carbon bricks are semi-dry pressed. Semi-dry molding is not very strict on the requirements of mud materials, and the process is simple. During the pressurization process, due to the low moisture content of the mud, high pressure must be used to force the particles to be tightly combined. Under the action of external force, the particles are rearranged, the gas is discharged, the particles are combined and then strength is generated to form a green body with a certain shape. The most important factor in semi-dry molding is the external pressure. Within a certain pressure range, the size of the external pressure directly determines the various properties of the magnesia carbon brick. With the increase of pressure, the density of the green body increases, the porosity decreases, and the strength increases. Magnesium carbon bricks with excellent performance have one thing in common, that is, magnesium carbon bricks have a large volume density and low porosity. Magnesium carbon bricks with an open porosity of less than 4% have a very low erosion rate. The purpose of molding is to densify the organizational structure of magnesium carbon bricks. Since magnesium carbon brick molding adopts a semi-dry method, it must be molded under high pressure. Since the clay used for molding is small in particle size and has a high graphite content, the molding must be strictly operated in accordance with the regulations, otherwise cracks or layer cracks are likely to occur. It should be light first and heavy later, pressurize multiple times, light hammer exhausts slowly, heavy hammer maintains pressure and lifts slowly. If conditions permit, a vacuum air brick press can be used. The mud in the mold cavity is vacuumed before pressurization, and there is no need to exhaust when pressurizing. In this way, even if the speed of light hammer pressurization is accelerated, it will hardly cause cracks or delamination of magnesia carbon bricks. It is especially useful for products such as high carbon magnesiumcarbon bricks that are prone to delamination.
05 Heat treatment (drying)
The heat treatment of magnesia carbon fire bricks, usually the factory calls this process drying. In fact, drying is not accurate enough here, because drying generally refers to the process of discharging the water contained in the product. In addition to the discharge of water, the heat treatment process of magnesia carbon firebricks is also accompanied by a series of physical and chemical changes, so we call this process heat treatment. The heat treatment temperature of magnesia carbon refractory bricks has a direct impact on the performance of mgoc bricks. The heat treatment process of magnesia carbon firebricks is actually the process of curing phenolic resin. The heat treatment temperature and heat treatment time directly determine whether the phenolic resin is completely cured. Within a certain range, the time for the resin to be completely cured is inversely proportional to the curing temperature, but it is not a linear relationship. Experimental studies have shown that the density of bricks can only be achieved when they are heat treated within a certain temperature range. If the heat treatment temperature is lower than this temperature range, the density of magnesia carbon bricks will decrease, but if it is higher than this range, the density of magnesia c bricks will decrease rapidly. Repeated studies have shown that the more reasonable temperature range is 200℃~250℃.
