Refractory for arc furnace cover

The structure of arc furnace cover is shown in the figure. Its function is to keep heat and protect the environment to prevent dust from spilling out. The central area of the eAF cover is perforated for electrode insertion and some metallurgical excipients. It does not come into direct contact with molten steel, but it is exposed to intense thermal shock, high temperature, and dust erosion. Low melting point and high ferric oxide refractory materials with electric arc furnace dust cover, generate liquid and promote the electric arc furnace cover on the surface of the refractory material sintering, the sintering layer and the linear change of different sintering layer, produce very big stress at the junction, between sintering and sintering layer caused by cracks, above 2000 ℃ electric arc ray radiation and pull out and insert the cover of electric arc furnace electrode triangle produce strong thermal shock and corrosion, thermal stress produces a lot of further promoting the triangle layered peeling off of the surface of the electrode hole and lower appear, this is the important reason of the electric arc furnace cover.

There are many small electric arc furnaces with ordinary power in Our country, which are used to burning high alumina bricks all the time, and have formed the national standard. The service life of high alumina brick on the cover of ordinary small arc furnace is generally within 60-120 furnace times. The water cooling area of small arc furnace cover is less, which may be one of the reasons why the service life of fired high alumina brick cover is not high. In recent years, with the development of refractory technology, the pattern of firing arc furnace top high alumina brick has been broken, and non-firing high alumina brick and high alumina castable prefabricated parts have appeared. These products significantly increased the service life, some of them reached more than 150 furnaces; At the same time save energy and simple construction, reduce labor intensity. So the furnace cover of high aluminum prefabricated parts occupies the main position gradually. The proportion of high aluminium bricks used is becoming less and less.

With the development of EAF steelmaking technology, the proportion of high-power and ultra-high-power EAF steelmaking increases, and the steelmaking rhythm is accelerated. The eAF cover is subjected to greater intensity of thermal radiation, thermal shock and more dust. Therefore, the service life of fired high aluminum brick is significantly reduced, and it can not meet the requirements any more. Castables and prefabricated parts of corundum, chrome and corundum for the arc furnace cover electrode triangle in this case. High alumina bricks, magnesia bricks and magnesia chrome bricks are generally used for the outer roofing. These new materials are new products developed in recent years and are made of vital refractories. Overseas use of these castable electric furnace cover life up to 200-400 furnace, individual even up to 500 furnace. However, the domestic service life is low, 100-300 furnace times more. There are many reasons for this, such as equipment, operation and product quality. In terms of equipment, the main factors affecting the service life of furnace cover are :(1) ultra-high power conversion of power and arc furnace steelmaking, which improves the intensity of arc light and thermal radiation and radiates to the surface temperature of furnace cover, thus increasing the thermal shock of refractory material and sintering shrinkage of furnace cover surface. The thermal stress and sintering stress were increased and the spalling was aggravated. On the other hand, ultra-high power also leads to more dust spatter, so the erosion of the furnace cover refractory increases; (2) Water-cooled area of furnace cover. In order to solve the problem of low service life of the furnace cover, the water-cooled area of the furnace cover is also increasing, and now it has reached more than 70%. Water cooling reduces the amount of refractory and the temperature of refractory used in the furnace cover, so the service life is improved significantly. It is not easy to be cooled by water around the electrode hole, so the high grade refractory material mentioned above is used. In order to reduce the consumption of graphite electrode and improve the service life of trigonometric refractory materials, the graphite electrode was cooled by water spraying. However, water-jet cooling electrodes are widely used in foreign countries, but there are few domestic users, which is one of the reasons for the high consumption of graphite electrodes and the low service life of refractory materials in the triangle area of furnace cover. In terms of operation, the more times the eAF cover is opened and closed, the more times the thermal shock is generated, the more severe the flaking of refractories is, and the lower the service life is. Besides, the temperature, time and oxygen blowing intensity of steelmaking all have great influence on the service life of furnace cover. The better the thermal shock resistance, the higher the resistance to high temperature and dust, the longer the service life of the refractory.