Due to the different working environments and service performances of various furnaces in steel production, the requirements for refractory materials are also different.
Refractory materials for AOD furnaces
Since the American Joslin Company invented the AOD molten steel refining method in 1968, it has been rapidly promoted since its application. So far, the AOD molten steel refining method has become the main method for stainless steel refining. However, during the application of the AOD furnace, its application conditions are very harsh, and the lining erosion is relatively serious. Therefore, in order to improve the lining life of the AOD furnace, it is very necessary to select refractory materials with excellent performance. At present, countries around the world mainly use dolomite bricks, magnesia dolomite bricks and magnesia-chrome bricks as refractory materials for the lining of AOD furnaces. Among them, the production process of magnesia-chrome bricks is complicated, and it has the disadvantages of high firing temperature, high energy consumption and high cost. In addition, in the case of high temperature, alkaline medium and oxidizing atmosphere, the Cr3+ in the magnesia-chrome refractory material will be converted into Cr6+ with strong carcinogenicity, which will cause great harm to the human body and the environment. Therefore, magnesia-chrome bricks are gradually replaced by magnesia-calcium materials, and magnesia-calcium refractory materials have become the preferred material for AOD furnace lining refractory materials. Europe has abundant natural dolomite, and its AOD furnace lining generally uses dolomite refractory materials to replace magnesia-chrome bricks. The wall of the cladding uses low-grade asphalt combined with unburned magnesia dolomite bricks or burned magnesia dolomite bricks, and the slag line uses high-temperature burned magnesia dolomite bricks. Although the life of this AOD furnace lining is lower than that of magnesia-chrome brick lining, it can reduce the cost of steelmaking and has obvious economic benefits.
LF furnace refractory
The LF furnace (ladle furnace) refining method developed by Japan Special Steel Company in 1971 is a production technology with arc heating, argon stirring and refined slag as the core. It was originally based on refining special steel. The LF furnace refining method has the characteristics of flexible use and multiple metallurgical functions, so it is widely used in ordinary steel manufacturers. The selection of refractory materials for LF furnaces is mainly based on refined steel types, refining temperature, slag basicity, stability and cost, etc. The service life of the selected lining refractory materials is generally 50~100 furnaces.
RH furnace refractory materials
The RH (molten steel vacuum cycle degassing) process was jointly developed by Ruhrstahl and Heraeus in West Germany, and it has a history of more than 50 years. The RH process has the advantages of low equipment investment, high smelting efficiency and easy operation, which makes it widely used in steelmaking production. At the same time, the RH process also has the characteristics of increasing steel production, improving steel quality, reducing costs and improving economic benefits. Its application in steelmaking production has greatly optimized the steelmaking process. The selection of RH furnace lining refractory materials is determined by its location and the temperature, atmosphere, chemical composition, vacuum degree and other factors. At present, the refractory materials used in domestic RH furnaces are mainly magnesia-chrome bricks. The refractory materials of the lining of the upper trough of the RH furnace are generally not in direct contact with molten steel and slag, and chromium-bonded magnesia-chrome bricks are usually selected; the working layer of the middle trough is in direct contact with molten steel and slag, and will be affected by factors such as erosion of molten steel, erosion of slag and sudden temperature changes. Generally, chromium-bonded magnesia-chrome bricks are selected, and lightweight high-alumina bricks are selected for the insulation layer; the lower trough will be continuously eroded by slag, and high-temperature fired magnesia-chrome bricks are generally selected.
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