Electric furnace top in more than 20 years ago, in foreign countries, the use of silicon brick as the top material, but in China, generally are high aluminum brick or prefabricated block to do the top.

Because the top of electric arc furnace is affected by the sudden change of temperature, slag injection, gas erosion and thermal radiation, the top refractory materials must have good thermal shock stability, corrosion resistance and high refractories. Firebrick for furnace cover is an evolutionary process of silicon brick, high alumina brick, alkaline brick and amorphous refractory (large prefabricated block). Because of the poor thermal shock resistance of silicon brick, the use of furnace top only about 60 times, in China as early as 20 years ago has not used silicon brick for the top of electric furnace. Alkaline firebrick is also some of its own shortcomings, can not resist the ultra-cold, extremely hot temperature changes under ultra-high power, silicon brick and alkaline brick has been replaced by a high alumina brick, corundum brick, high alumina precast block, castable. In particular, the water-cooled furnace cover only uses refractory materials in the central part of the furnace cover. The use of molded bricks to build the furnace takes time, and the ash joint between bricks and bricks is not strict, which will make the stress distribution uneven and reduce the service life of the top protection.

In recent years, large prefabricated blocks made of high strength castables have been used more than 1000 times to build furnace tops. In China, the top brick is generally made of high aluminum, which is used in 300-400 furnace times. Five to six times longer than silicon bricks, but small stoves are suitable for high alumina bricks and corundum castables.

At present, the number of large prefabricated blocks used on the top of electric furnace in China is increasing, because according to the shape of the top, the electrode hole is set aside for the whole furnace cover, which greatly reduces the complexity of the construction link. And the service life of the first grade high aluminum brick more than 2 times the service life. However, the price of prefabricated integrated top is relatively high. Some small top stoves use high quality aluminum bricks to do top stoves because of financial problems. With the development of amorphous refractory castables, ultra-low cement castables have been successfully applied to electric furnace tops. The use of ultra-low cement castable in the triangle area improves the service life a lot. The whole furnace top is prefabricated, the life of the furnace top has reached 600 times, and the small furnace cover has reached more than 1000 times.

General electric furnace is intermittent production, rapid cooling and rapid heating temperature is frequent, the use of silicon brick furnace top that increases the number of replacement, but also increases the production cost. So the top of the electric furnace is not suitable for the use of silicon brick.