The furnace wall of the electric furnace is divided into ordinary, slag line and hot spot areas according to the working environment. The life of its refractory materials is affected by the smelting technology. To increase the life of the furnace wall, measures such as improving the quality of refractory materials, strengthening the gunning technology, and strictly controlling the smelting process can be taken.
The furnace wall of an electric furnace can be divided into three parts according to different working environments: the ordinary furnace wall area, the slag line area and the hot spot area.
During the smelting process, the furnace wall of an electric furnace is affected by the radiation of high-temperature arcs and the rapid temperature changes during charging and steel discharge. It is also affected by the direct erosion of molten steel, the chemical erosion of high-temperature slag, the mechanical impact of materials during charging, and the mechanical vibration during tilting. Especially near the slag line area, the erosion of materials is particularly serious.
In a three-phase AC arc furnace, the temperature distribution of each part of the furnace wall is very uneven. The hot spot area corresponding to the three-phase electrode has the highest temperature. In addition to being eroded by slag and molten steel, this area is also directly radiated by the high-temperature arc, so the furnace lining is damaged the fastest. In particular, the slag line area near the electrode is often the weakest link in the furnace wall and is most susceptible to erosion.
In addition, the furnace door and the furnace walls on both sides of the electric furnace are the most vulnerable areas due to erosion by slag and collision by the slag remover, which often becomes the main reason for shutdown.
Factors affecting the service life of refractory materials for electric furnace walls
The service life of refractory materials used in electric furnace walls is often closely related to the smelting technology used by the electric furnace plant. In order to strengthen smelting and reduce the impact of smelting conditions on refractory materials, various companies have adopted the following smelting technologies:
Electric furnace water cooling furnace wall technology:
The water-cooled furnace wall of an electric furnace is usually made of cast steel or steel plates, among which steel plates are mostly used for the walls of large electric furnaces. The size, number and installation position of the cooling wall blocks are determined according to the actual production situation. The purpose is to achieve a relatively balanced service life of each part of the furnace lining material. When in use, a layer of refractory material can be sprayed on the inner surface of the water-cooled wall block for easy hanging or a layer of magnesia carbon bricks can be built on the inner side of the water-cooled wall to protect the water-cooled block.
The use of water-cooled furnace wall technology can form a slag layer on the surface of the furnace wall to reduce the erosion of slag and molten iron on the refractory material of the furnace wall.
The currently installed water-cooled furnace wall accounts for more than 60% of the furnace wall of electric furnaces, which greatly reduces the consumption of refractory materials and saves smelting costs. The typical installation method of the electric furnace cooling plate is shown in Figure 2.
Foam slag technology：The use of water-cooled furnace wall technology can strengthen the smelting operation, but water cooling will inevitably bring about greater heat loss. By spraying carbon and blowing oxygen into the molten pool, or adding a foaming agent into the molten pool to generate a large amount of foam, the long arc generated by the increased voltage can be covered, which can speed up the heating of the electric furnace, improve the heat transfer efficiency of the arc to the molten pool, and reduce power consumption.
Since the arc is buried in the slag, the heat radiation of the arc to the furnace wall and the furnace cover can be significantly reduced, and long arc operation can be used during the smelting process, which can not only achieve rapid dephosphorization but also increase the life of the furnace lining, improve thermal efficiency, shorten the smelting cycle, and reduce power consumption and electrode consumption.
Oxygen-fuel melting technology：By using a flux oxygen burner and spraying fuel and oxygen into the molten pool, the cold spots in the furnace can be eliminated, so that the entire furnace can melt synchronously. At the same time, the total heat input into the furnace can be increased, and power consumption can be reduced, the consumption of electrodes and refractory materials can be reduced, and the smelting cycle can be shortened.
Oxygen-coal injection technology：Using the high-temperature flame generated by the combustion of coal and oxygen as an auxiliary heat source during the melting period of the electric furnace can increase the heat in the furnace, reduce electrode heating and operation, and increase the service life of the furnace lining.
The furnace wall of the electric furnace is divided into three parts according to the use conditions：The main furnace wall, slag line and hot spots. Since the working conditions and service life of the three parts are different, most of them use the comprehensive furnace lining method to achieve balanced erosion of the entire furnace lining.
Technical measures to increase the life of electric furnace wall
1) Further improve the quality of refractory furnace lining. Using large crystal magnesia sand to make magnesia carbon bricks helps to improve the corrosion resistance and oxidation resistance of magnesia carbon bricks. Using high-purity flaky large crystal graphite as the carbon source of magnesia carbon bricks can significantly improve the corrosion resistance and oxidation resistance of magnesia carbon bricks and increase the service life of furnace linings.
Adding an appropriate amount of antioxidant can prevent the oxidation of carbon in magnesia carbon bricks. At the same time, after the oxidation of antioxidants, some can generate new substances with high melting points with magnesia sand or directly generate substances with high melting points, which can block pores and improve the corrosion resistance of materials. Vacuum oil immersion is adopted for magnesia carbon bricks. Vacuum oil immersion can close the pores of magnesia carbon bricks, reduce the porosity after carbonization, and improve the corrosion resistance of materials. Using asphalt and resin composite binders, a mosaic bonding mode can be formed in the material, the carbon bonding fracture toughness can be enhanced, and the oxidation resistance of magnesia carbon bricks can be improved.
(2) Strengthen the gunning technology of furnace wall. The use of appropriate gunning technology can extend the service life of furnace lining materials and reduce smelting costs. Commonly used binders for gunning materials are silicates, phosphates and various magnesium salts. Since the gunning materials combined with phosphates have strong adhesion strength, they have a long service life.
(3) Strictly control the smelting process. Strictly controlling the smelting process can not only produce qualified products and reduce waste, but also is extremely beneficial to the oxidation and maintenance of the furnace lining, and can also greatly save costs.
Strictly controlling the smelting process is mainly to make good foam slag. The shielding effect of foam slag not only improves the thermal efficiency of the electric furnace, but also effectively protects the furnace wall from the radiation of arc light, which can greatly reduce the consumption of refractory materials.
