Directly bonded magnesia-chrome bricks have high temperature resistance, SIO2 erosion resistance and oxidation-reduction resistance, as well as high temperature resistance strength and mechanical stress resistance, and better kiln skin hanging performance. It is widely used in the burning zone of cement kilns. When magnesia chrome bricks are used, under the action of alkali or sulfur, the stable trivalent chromium is converted into hexavalent chromium, which will cause serious harm to the human body. Since the mid-1980s, countries around the world have formulated A series of sanitary standards restrict the use of magnesia chrome bricks. In the 1990s, due to the excellent performance and low price of magnesia-chrome bricks, direct-bonded magnesia-chrome refractory bricks with better performance than magnesia-chrome bricks are being used in many countries and regions, and they are used in working conditions. On the more demanding large-scale precalcining kiln. Aluminum Magnesium Carbon Brick
Magnesium Dolomite Brick
Magnesia dolomite bricks are made by molding raw materials through a binder and then firing them. Magnesia dolomite bricks have the following advantages: chemical stability and affinity for cement clinker; high refractoriness; easy to hang on the kiln; the price is relatively cheap. Therefore, magnesia dolomite bricks are used more in foreign countries, but their comparison Easy to hydrate.
When the temperature in the kiln changes sharply, the magnesia dolomite bricks are prone to structural spalling at the interface between the original brick layer and the reaction layer, so the use of magnesia dolomite bricks in cement kilns with low operating rates is restricted. The roof of the electric furnace is generally built with high-alumina bricks, and the Al2O3 content is between 75% and 85%. Compared with silica bricks, high alumina bricks are characterized by high refractoriness, good heat resistance, good slag resistance and high compressive strength. Because of the good thermal shock resistance and structural integrity, the high-aluminum amorphous material does not need to be made into special-shaped bricks. Generally, ramming materials are used in the center of the small furnace cover and around the electric holes. Due to the abundant bauxite resources in China, high alumina bricks have become the main refractory material for electric furnace roofs, and their service life is about 2 to 3 times that of silica brick roofs. With the development of large-scale ultra-high power electric furnaces, the service life of high alumina bricks has decreased, leading to the further use of basic bricks such as fired or unfired magnesia bricks and magnesia chrome bricks.
Magnesia carbon brick
Due to the low high-temperature strength and self-weight of bricks, in order to prevent the furnace roof from sinking due to deformation, a hanging structure is generally adopted. On the roof of some ultra-high-power electric furnaces, magnesia-chrome bricks are used directly combined with alkaline bricks with good high-temperature strength, which can overcome the deterioration of ordinary alkaline bricks due to large expansion coefficients and absorption of slag dust, resulting in structural cracking or thermal cracking The severe spalling caused by the phenomenon has a service life of 300 heats. Refractory material for furnace wall The furnace wall is divided into general furnace wall, slag line area and hot spots adjacent to the arc. It is not only heavily corroded and scoured by molten steel and molten slag, but also subjected to mechanical impact and rapid cooling when scrap steel is added. More serious is the intense heat radiation from high-temperature arc light, and the molten steel temperature in the hot spot area is 2000°C. Therefore, the furnace wall often undergoes local melting loss. In addition, it is also affected by the agitation of molten steel and molten slag and the atmosphere of different smelting periods, resulting in serious damage to the inner lining, especially for ultra-high power electric furnaces.
Generally, the furnace wall mainly uses magnesia bricks, tar pitch combination and asphalt impregnation to make dolomite bricks and magnesite bricks. There are also magnesia chrome bricks that do not burn iron shell alkaline bricks and asphalt combined with magnesia and dolomite ramming materials. Yes, the battery life is longer. The walls of ultra-high power or special steel smelting electric furnaces are built with magnesia-chrome bricks and high-quality magnesia bricks, and the effect is obvious. The slag line area and hot spots are the weak links of the furnace wall. Because the life of the furnace wall mainly depends on the damage degree of the hot spot, the furnace lining at this spot is particularly valued. Before the 1970s, fused cast magnesia chrome bricks were generally used in this part, directly joined or recombined with magnesia chrome bricks, and the service life reached 100 to 250 heats. After entering the 1980s, magnesia-carbon bricks were widely used for masonry in these parts, showing excellent and slag resistance performance, and the service life was significantly improved. China's high-power electric arc furnace reached more than 300 heats.
