Composition of electric arc furnace

The electric arc furnace is a device that uses the arc generated between the electrode tip and the chargeas heat energy to make steel.

The development of electric arc furnace technology is the development of direct current electric arc furnace, furnace bottom gas agitation and furnace bottom tapping based on the use of high power. The electric arc furnace is composed of furnace roof, furnace wall, furnace bottom and tapping trough.

1. Refractory materials for electric arc furnace roof

The roof of the electric arc furnace is generally built with high-alumina bricks, and the alumina content is between 75%-85%. Compared with silica bricks, high-alumina bricks are characterized by high refractoriness, good thermal shock resistance and high compressive strength. Due to the rich domestic bauxite resources, high alumina bricks have become the main refractory material for electric arc furnace roofs, with a life span of about 2-3 times that of silica brick roofs.

With the development of large-scale ultra-high-power electric furnaces, the service life of high alumina bricks is also decreasing, leading to the further use of basic bricks such as fired or unfired magnesia bricks and magnesia chrome bricks. It can also be hoisted with commercial cast refractory preforms. Compared with ordinary masonry furnace roofs, it has the advantages of convenient construction, good integrity, strong resistance to arc radiation, and resistance to rapid cold and heat.

2. Refractory materials for furnace wall

The furnace wall is divided into general furnace wall, slag line area and hot spots near the arc. Generally, the furnace walls are mainly built with magnesia bricks, dolomite bricks and periclase bricks, and there are also unburned magnesia alkaline bricks and asphalt combined with magnesia and dolomite ramming materials. The furnace wall of ultra-high power or special steel smelting electric arc furnace uses 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 damage degree of the hot spot, special attention should be paid to the lining of this part. In the early days, magnesia-chrome bricks were used for masonry, and the life span reached 100-250 heats. Magnesia carbon bricks are now 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 balance the damage of the furnace wall and prolong its life, the furnace wall is also equipped with a water-cooled box or water-cooled jacket. The inner surface is sprayed with a layer of refractory coating to form a protective layer of slag, which can effectively reduce the unit consumption of refractory materials. But the corresponding energy consumption has increased.

3. Refractory materials for furnace bottom

The bottom of the furnace and the slope of the embankment constitute a melting pool, which is the place where the charge and molten steel are collected. When the furnace bottom lining reacts with molten slag and iron oxide to form a metamorphic layer, it can become loose due to the reduction of some of its components during the reduction, which often causes floating due to molten steel intrusion.

Therefore,the masonry or knotted lining of this part should have the advantages of uniform overall performance, tight masonry, good high temperature performance, high strength, corrosion resistance, erosion resistance, thermal shock resistance and stable volume.

Select good magnesia or fused magnesia for the knotted lining. Pay attention to the joints of each layer during construction. The thickness and densityof each layer should be consistent. There are working layers and permanent linings under the ramming layer. The working layer is selected from tar pitch combined with magnesium For brick masonry, magnesia bricks are mostly used for 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 the hot spots of the furnace wall are often used, such as cast magnesia chrome bricks or combined with magnesia chrome bricks. It is better to use magnesia carbon brick.

4. Refractory materials for tapholes

The currently used furnace bottom eccentric tapping method changes the furnace body from a tilting type to a fixed type, and sets a tap hole at the eccentric position of the furnace bottom to replace the tapping trough.

Its advantages are: cancel the tilting equipment, expand the area of the water wall, alleviate the damage of the furnace lining, appropriately reduce the tapping temperature and shorten the tapping time, thereby reducing the cost.

The eccentric taphole 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% ALO-C-SiC bricks, for smooth tapping, coarse sand with olivine as matrix is often used as drainage material.