An electric arc furnace is a device that uses the arc generated between the electrode end and the charge as heat energy to make steel. The development of electric arc furnace technology is based on the use of high power to develop DC electric arc furnaces, furnace bottom gas supply mixing and furnace bottom tapping. The electric arc furnace consists of a furnace roof, furnace walls, furnace bottom and tapping trough.
1. Refractory materials for electric arc furnace top
The top of electric arc furnaces is generally constructed of high-aluminum bricks, with an alumina content between 75% and 85%. Compared with silica bricks, high-alumina bricks are characterized by high refractoriness, good thermal shock resistance, and high compressive strength. Due to the abundant bauxite resources in China, high alumina bricks have become the main refractory material used in electric arc furnace roofs, and their service life is about 2-3 times that of silica brick roofs.
2. Refractory materials for furnace walls
The furnace wall is divided into general furnace wall, slag line area and hot spots near the arc. Generally, furnace walls are mainly built with magnesia bricks, dolomite bricks and periclase bricks. Some also use unburned magnesia alkaline bricks and asphalt combined with magnesite and dolomite ramming materials. The walls of electric arc furnaces for ultra-high power or special steel smelting are built with magnesia-chrome bricks and high-quality magnesia bricks.
The slag line area and hot spots are the weak links of the furnace wall. Since the life of the furnace wall mainly depends on the degree of damage to the hot spot, special attention should be paid to the furnace lining in this area. Nowadays, magnesia carbon bricks are widely used for masonry, which can show excellent high temperature resistance and slag resistance. The service life is significantly improved, reaching more than 300 heats.
In order to even out the damage to the furnace wall and extend its service life, the furnace wall is also built with a water-cooling box or water-cooling jacket. The inner surface is sprayed with a layer of refractory paint to form a protective layer with slag, which can effectively reduce the unit consumption of refractory materials. However, the corresponding energy consumption has increased.
3. Refractory materials for furnace bottom
The knotted lining should be made of good magnesia or fused magnesia. During construction, pay attention to the connection and interlocking of each layer. The thickness and density of each layer should be consistent. There is a working layer and permanent lining under the ramming layer. The working layer should be made of tar asphalt combined with magnesium. For brick construction, the permanent lining is mostly made of magnesia bricks. In the slag line at the upper part of the embankment, due to severe slag erosion, lining bricks that are the same or similar to the hot spots of the furnace wall are often used, such as cast magnesia chrome bricks or combined magnesia chromium bricks. It is better to use magnesia carbon bricks.
4. Refractory materials for tapholes
The currently used tapping method with an eccentric taphole on the furnace bottom changes the furnace body from a tilting type to a fixed type, and sets a taphole at the eccentric position of the furnace bottom instead of a tapping trough. Its advantages are: eliminating the tilting equipment, expanding the water wall area, mitigating furnace lining damage, appropriately lowering the tapping temperature and shortening the tapping time, thereby reducing costs. The eccentric taphole bricks are asphalt-impregnated fired magnesia bricks, the pipe bricks are 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%. 15% ALO-C-SiC bricks, in order to smooth the steel tapping, often use olivine-based coarse sand as the drainage material.
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