The roof of an electric arc furnace is typically constructed using high - alumina bricks with an alumina content ranging from 75% to 85%. In comparison to silica bricks, high - alumina bricks offer several distinct advantages. They possess high refractoriness, enabling them to withstand extremely high temperatures without melting or deforming. Additionally, they exhibit good thermal shock resistance, which means they can endure rapid changes in temperature without cracking. Their high compressive strength also ensures that they can withstand the mechanical stresses exerted during the furnace's operation.
Given the abundance of domestic bauxite resources, high - alumina bricks have emerged as the primary refractory material for electric arc furnace roofs. Their service life is approximately 2 - 3 times longer than that of silica brick roofs. However, with the development of large - scale ultra - high - power electric furnaces, the service life of high - alumina bricks has been decreasing. As a result, basic bricks such as fired or unfired magnesia bricks and magnesia chrome bricks are being increasingly used. Moreover, commercial cast refractory preforms can also be hoisted for use. Compared to ordinary masonry furnace roofs, these preforms offer the benefits of convenient construction, good integrity, strong resistance to arc radiation, and the ability to withstand rapid cold and heat changes.
The furnace wall of an electric arc furnace can be divided into three sections: the general furnace wall, the slag line area, and the hot spots near the arc. Generally, magnesia bricks, dolomite bricks, and periclase bricks are the main materials used for constructing the general furnace walls. Some furnaces also employ unburned magnesia alkaline bricks and asphalt - combined magnesia and dolomite ramming materials. For ultra - high - power or special steel smelting electric arc furnaces, magnesia chrome bricks and high - quality magnesia bricks are preferred.
The slag line area and the hot spots near the arc are the weakest links of the furnace wall. Since the overall life of the furnace wall mainly depends on the degree of damage at the hot spots, special attention must be paid to the furnace lining in these areas. In the early days, magnesia chrome bricks were used for masonry in these regions, with a service life of 100 - 250 heats. Nowadays, magnesia carbon bricks are widely used for masonry, which demonstrate excellent high - temperature resistance and slag resistance. As a result, the service life has been significantly improved, reaching more than 300 heats.
To balance the damage to the furnace wall and extend its service life, water - cooled boxes or water - cooled jackets are installed on the furnace wall. The inner surface of the furnace wall is then sprayed with a layer of refractory coating to form a protective slag layer. This effectively reduces the unit consumption of refractory materials, although it does lead to an increase in energy consumption.
The bottom of the furnace and the slope of the embankment together form the melting pool, which is the area where the charge and molten steel are collected. After the furnace bottom lining reacts with molten slag and iron oxide, a metamorphic layer is formed. This layer can become loose due to the reduction of some of its components during the reduction process, and it is often caused by the intrusion of molten steel, leading to floating.
Therefore, the masonry or knotted lining of this part should have several advantages. It should have uniform overall performance, tight masonry, good high - temperature performance, high strength, corrosion resistance, erosion resistance, thermal shock resistance, and volume stability. For the knotted lining, good magnesia or fused magnesia should be selected. During construction, special attention should be paid to the joints of each layer, ensuring that the thickness and density of each layer are consistent. There are working layers and permanent linings beneath the ramming layer. The working layer is usually made of tar - pitch - combined magnesium brick masonry, while magnesia bricks are mostly used for the permanent lining.
At the slag line on the upper part of the embankment slope, due to the severe erosion of the slag, the same or similar lining bricks as those used at the hot spots of the furnace wall are often employed, such as cast magnesia chrome bricks or combined magnesia chrome bricks. Magnesia carbon bricks are also a good choice.
The currently used furnace bottom eccentric tapping method has transformed the furnace body from a tilting type to a fixed type. A tap hole is set at the eccentric position of the furnace bottom to replace the tapping trough. This method offers several advantages, including the elimination of tilting equipment, an expansion of the water - wall area, a reduction in furnace lining damage, an appropriate decrease in tapping temperature, and a shortening of tapping time, all of which contribute to cost reduction.
The eccentric tap hole bricks are pitch - impregnated and fired magnesia bricks. The pipe bricks are made of magnesia carbon bricks with a resin - bonded carbon content of 15%, and the end bricks are magnesia - carbon bricks with a resin - bonded carbon content of 10% - 15%. For 15% Al₂O₃ - C - SiC bricks, to ensure smooth tapping, coarse sand with olivine as the matrix is often used as drainage material.
We are a professional electric furnace manufacturer. For further inquiries, or if you require submerged arc furnaces, electric arc furnaces, ladle refining furnaces, or other melting equipment, please do not hesitate to contact us at susie@aeaxa.com
