Advantages of high alumina bricks as refractory materials for furnace roof

October 29, 2018

Advantages of high alumina bricks as refractory materials for furnace roof 

In the early days, the tops of electric furnaces were all made of silicon bricks. Until 1960, silicon bricks were still the most widely used refractory materials for electric furnace roofs. Because silicon brick has many advantages in performance, such as light weight, high temperature strength, low radium rate, high load softening temperature, no shrinkage of reheating, good heat shield stability, and low price, it has long been used as refractory for electric furnace roof. 

The refractory products of the electric furnace roof is required to have a higher softening temperature, and the damage temperature of the silicon brick under the load is close to the melting point of SiO2. There was almost no sign of damage until then. At the same time, under the condition of temperature change for the top of the electric furnace, the thermal expansion and re-heating shrinkage of the furnace top brick are very important when the temperature difference is large, and the thermal stability of the silicon brick at this temperature is good. However, the damage of the lining brick of the electric furnace roof with silicon brick is mainly caused by the slag corrosion and melting flow, and the silicon brick itself reduces the alkalinity of the slag, resulting in the melting of the refractory material in the top of the electric furnace.

With the continuous development of the steel industry, the smelting temperature has increased to the extent that silicon bricks can no longer bear. Therefore, we have to study and try other refractory materials with higher melting point. Among them, high alumina bricks have been widely used.

High alumina bricks have the following advantages over silicon bricks:

(1)High alumina brick is a kind of neutral refractory material, its refractoriness is higher than that of silicon brick by more than 100℃, and it does not melt at a very high temperature, so it is beneficial to strengthen the operation of electric furnace.

(2) High alumina bricks have good corrosion resistance at high temperatures and good corrosion resistance to CaO, especially iron oxide. Therefore, when it meets with CaO and iron oxide, it can produce highly viscous reaction products on the surface of the brick, thereby forming a refractory shell, which prevents the working layer of the brick from being rapidly melted.

(3) High alumina bricks have high thermal stability and thermoplasticity, which have higher resistant to temperature changes and thermal expansion stresses. High alumina bricks have been used for a long time to meet the operating conditions of electric furnace tops with the working temperatures up to 1700℃.