Refractory for arc furnace walls
It is worth pointing out that small electric furnace steelmaking still accounts for a considerable proportion in China at present. It USES lower grade refractory materials with low price,resulting in low service life and high single consumption. It mainly USES bituminous magnesia brick, low grade magnesia carbon brick and magnesia filling charge. However, the quality of bitumen bonded magnesia bricks and magnesia carbon bricks should be further improved, and the quality of bitumen bonded products is far from that of similar products in Europe. Our country should raise the technical level in this field. The properties of magnesium carbon brick made of modified asphalt series resin binder are not inferior to that of phenolic resin bonded magnesium carbon brick. The service life of our small arc furnace is no less than 40-120 times. Through the technical transformation of the small electric arc furnace, the improvement of operation level, the reinforcement of furnace protection and the use of high quality refractory materials, many small electric furnace lining life has been increased to more than 150 times, and steel consumption per ton has been reduced to less than 6kg.
For the ultra high power large electric furnace, it can be said that our country was only developed rapidly in the 1990s. High quality magnesia carbon brick for electric furnace wall, especially high quality magnesia carbon brick for slag line and hot spot. Not only so, it is often used to spray and maintain the slag line and other erosive parts, and the lining spraying is the main means to maintain the lining life. Whenever ordered repair, dig and repair some badly damaged parts. In this way, the service life of ultra-high power and large electric furnace lining has reached thousands of furnaces, and the service life of individual DC electric furnace wall has exceeded 2000 furnaces and above. The consumption of magnesium carbon brick lining is as low as 0.2kg per ton of steel, and the consumption of electric furnace refractory material is mainly spraying material. The main material of electric furnace injection material is magnesium material.
The above methods and systems are seldom used in the maintenance of arc lining in China. For small arc furnace, spraying material is rarely used to maintain the lining life. Generally, low-grade bitumen tar magnesia or waste brick is used to patch the lining to 100 furnaces or so, and then it stops to renew. With the increase of the arc furnace, the furnace lining is sprayed, and the furnace lining is maintained to 200-300 times before stopping to replace it with a new one. For the larger modern furnace, the spray maintenance is further strengthened and the service life reaches more than 500 furnaces before stopping to replace the new lining. Therefore, for the maintenance mode of eAF in China, a lot of waste refractory materials are removed, which causes a lot of waste. This aspect deserves research and development, which is of great significance to resource conservation, zero emission and environmental protection.
One point worth explaining is that China generally USES Martin sand for furnace door repair. The slag from the furnace door is often eroded, and the operator is ready to repair it with Martin sand. It is worth pointing out that there are still some steel mills that use chromic anhydride bound Martin sand, which should be discontinued. Because chromic anhydride is 6 valence chromic, it is harmful to human health seriously. For the smelting of some ultra-low carbon steel and stainless steel, the carbon requirements are very high, in order to prevent the increase of carbon, do not use magnesia carbon brick and other refractory, but magnesia brick, magnesia binder or magnesia chromium refractory as lining.