Arc furnace lining refractories are often in the state of high temperature, slag erosion and quench and quench, the working conditions are extremely harsh. In the melting period and oxidation period of steelmaking, the lining will not be damaged by high temperature, but in the reduction period, the liquid steel temperature is quite high, and by direct arc radiation, the lining is very easy to be damaged. In addition, when the steel charging is finished, the lining temperature suddenly drops, and the charging begins to send electricity, and the temperature gradually rises. This kind of temperature change of rapid cooling and rapid heating is often the direct cause of the lining spalling.
The erosive action of slag on lining determines its composition and fluidity. The higher the content of SiO2 in slag, the more serious the erosion of alkaline lining is. In addition to SiO2, AI203, Fe2O3 and CaF2 in the slag also erode the lining. The fluidity of slag also has an influence on the lining. The slag thinness has a serious scouring effect on the lining and strong ability of reflecting arc, which will increase the thermal load of lining refractory: the slag thickening makes it difficult to heat the molten pool, the physicochemical reaction condition becomes worse, and the high temperature action time of lining (that is, the smelting time) is prolonged. These will accelerate the damage of lining.
In many cases, the damage to the lining is due to the impact of mechanical forces, such as unreasonable cloth, the bottom of the furnace without small scrap protection, charging tank too high. In these cases, the bottom of the furnace may be dented by large pieces of scrap. The mechanical vibration caused by lifting of furnace cover, opening of furnace body and pouring out of furnace is also the cause of damage to furnace lining. In addition, improper charging ratio, incorrect smelting operation, such as oxygen blowing high temperature oxygen flow directly touch the lining, will damage the lining. Therefore, the refractories of masonry arc furnace should have high refractoriness and softening point under load, good thermal stability and slag resistance, sufficient mechanical strength at high temperature and low thermal conductivity, etc. Silicon brick is generally used in laying acid arc furnace, while magnesium brick is used in alkaline arc furnace, but high aluminum brick is mostly used in furnace top. Silicon brick furnace top has been rarely used.