Do you know the type of magnesia most suitable for producing magnesia carbon brick?
The main raw materials for producing magnesia carbon brick are: magnesia, graphite, phenolic resin; In addition, there are some auxiliary additives such as: aluminum powder, silicon powder, silicon carbide, high temperature asphalt powder and so on. Magnesia carbon brick production is the proportion of the raw materials with the appropriate combination of process, according to the demand of the use of different environment and different prices can design all kinds of different formulations, and is particularly important to choose the appropriate raw materials, below in magnesite, for example, discussed how to choose the most appropriate use of magnesia magnesia carbon brick production.
The classification of magnesia is mainly divided into two types according to the production process of magnesia: one is electrofused magnesia; The second is sintered magnesia.
Electrofused magnesite is made of high-quality magnesite through melting and crystallization in an electric arc furnace. The sintered magnesite is mainly made of coal or natural gas, and the magnesite is calcined at 1550~1800℃.
These two kinds of magnesia have their own advantages, such as high purity of electrofused magnesia, large grain size, high porosity density, strong slag resistance, but high production cost. Compared with electrofused magnesia, sintered magnesia has smaller grain size, larger porosity and lower density, but its production cost is lower.
According to the actual raw materials used by the enterprise, there are generally the following kinds of magnesia suitable for the production of magnesia carbon brick:
Large crystalline magnesia
Large crystalline electrofused magnesia is mainly made from light burned magnesia with a high purity content of 91-92%, which is fused by electric arc furnace and kept warm. The product appearance is generally white transparent, as the impurity content of some slightly different gray or pale yellow, with high purity, crystal particles is large, high density, good slag resistance and thermal shock stability is strong, is one of the important raw materials used to make high temperature electrical insulation materials, is also making high-grade magnesia brick, magnesia carbon brick, etc all kinds of high-grade refractory materials important raw materials. It is also widely used in metallurgy industry, chemical industry, national defense research, aerospace and so on.
Ordinary fused magnesia
Ordinary electrofused magnesia enterprises referred to as electrofused magnesia, it is mainly selected 47% of the content of magnesite ore, after the arc furnace melting, insulation and made. Electrofused magnesia has large grain size, high density, low porosity and good slag resistance. Used to do high temperature electrical insulation materials, but also to make high-grade magnesia brick, magnesia carbon brick and other high-grade refractory materials. Its main use is in refractory materials.
High purity magnesia (high purity ball)
High purity magnesite is a kind of magnesite with higher purity, which is first lightly burned, then finely pressed into balls and calcined in ultra-high temperature vertical kiln. It is the main raw material for producing magnesia brick, magnesia carbon brick, casting products and various amorphous refractory materials.
Basic is suitable for production of magnesia carbon brick magnesia above several, including large crystal sinter and magnesium content is in commonly 97%, average fused magnesia, magnesium content is in commonly 96%, high purity magnesia, magnesium content is in commonly 96.5%, so the content of magnesia can be used to produce magnesium carbon brick, magnesite taste lower would be easy to cause the product quality problem, magnesia chosen is not the same as the quality of the products also have very big distinction.
The content of magnesium oxide is only one factor when selecting magnesia, and the density of magnesia is also an extremely important factor. Under the premise of the same production process, the higher the content of magnesia, the smaller the porosity and the higher the density should be theoretically, as shown in FIG. 2, FIG. 3 and FIG. 4. However, driven by economic interests, some cases are not so, so we must pay attention to the choice of magnesia, in addition to the content of magnesium oxide, but also to see the density of magnesia, especially for the purchase of granular material manufacturers is particularly important.
Fuel costs for production of magnesia is one of the most important cost of fused magnesia and sintered magnesia are so, so now a lot of manufacturers to reduce production costs, greatly reduce the fused and sintering time, so that to reduce the energy consumption, thus will bring about many negative effects, the most prominent is the raw material is owed to burn, for magnesite, owe to burn in magnesia small grain size, density is not up to standard, broken after fine powder.
When magnesia carbon brick first appeared, magnesia carbon brick was mostly produced by sintered magnesia in foreign countries. However, it was found that magnesia and graphite had the following reactions at high temperature:
The study shows that the reaction starts from 1600℃, and the reaction speed increases as the temperature increases. Is the process of graphite oxide, one of the main reasons for loss of magnesia carbon brick, magnesia carbon brick damage is first and foremost in the slag in various oxide and environment under the action of O2, CO2, etc, make the working face, graphite oxidation decarburization of forming loose layer, and infiltration of the molten slag osteoporosis and magnesia reaction to generate low melting of the decarburization layer of the lower strength of magnesia carbon brick to accelerate damage. Impurities such as SiO2 and Fe2O3 in magnesia can accelerate the whole reaction process, so we hope that the lower the impurities are, the better.
Table 1 typical values of magnesia chemical indexes
Compared with sintered magnesia, electrofused magnesia has larger grain size, better density, lower porosity and better slag resistance. In addition, the higher the content of magnesium oxide, the lower the quality of the corresponding harmful impurities, especially silicon dioxide, the lower the content of silicon dioxide, the lower the temperature of the product generated in the silicate low molten matter is less, less molten matter, the probability of reaction with graphite is lower, the performance of the product will be better. The larger the grain, the higher the direct bonding degree of the product, the less the grain boundary liquid phase, to avoid slag from the grain boundary liquid phase began to erode the product.
Therefore, with the development of magnesia carbon brick, in order to improve the performance of the product, the production of magnesia carbon brick began to use electrofused magnesia. However, due to the high density of electrofused magnesia, low porosity and poor wettability of the binder, sintered magnesia can make up for this problem, so it is sometimes used in combination with sintered magnesia. Due to the bad market situation in recent years, sintered magnesia occupies an increasing share in the production of magnesia carbon brick.
According to the application results of magnesia carbon brick in steel mills, the field application effect of magnesia carbon brick is relatively good is generally made of magnesia with high content of magnesia, high density, large crystal particle and high ratio of calcium to silicon