Refractory Materials Used In the Lining of Electrical Arc Furnaces

Steel smelting in an electrical arc furnace (EAF) is a complex high temperature process in which the temperature is high, up to 1700-1800℃, the atmosphere changes a lot and the smelting circle is short.

The refractory materials used in the EAF lining are subjected to high temperature, molten slag corrosion and thermal shock. The condition is very hash. During the melting and oxidization process, the lining will not be damaged, but during the reducing process, the lining is easy to be damaged due to high temperature molten steel and the direct radiation from the arc. Besides, when steel is discharged and new charge is loaded, the temperature will suddenly drop and then gradually rise when heating starts. The thermal shock is the direct reason for the spalling of the lining. 

 

Corrosion by slags to the lining is up to its composition and mobility. The higher the SiO2 content in the slags is, the more serious the damage to the lining is. In addition to SiO2, Al2O3, Fe2O3 and CaF2 can also damage the lining. The mobility can also affect the lining. The scouring action of slags and the ability to reflect the arc can increase the thermal load of refractory materials. Slags can make heating difficult and the physical and chemical reaction conditions worse and expand the smelting time. All these can accelerate the lining damage.

 

In most cases, the damage of the lining is caused by the mechanical impact, such as unreasonable material arrangement, no small piece of steel scrap protection in the bottom and too high feed tank. In these cases, the bottom can be smashed into pits large pieces of steel scraps. Mechanical vibrations caused by the lifting of the cover, starting and discharging of the furnace and tilting the furnace can also damage the lining. Besides, the improper proportion of materials and the incorrect operation of smelting are also reasons for the damage of the lining. 

 

Therefore, refractory materials used in the EAF should be of high refractoriness and refractoriness under load, good thermal stability and slag resistance, high mechanical strength at high temperature and low thermal conductivity. Silica bricks are always used in the acid EAF and magnesia bricks are used in the alkali EAF. But the roof is always built with high alumina bricks. Silica bricks are seldom used in the roof.