Furnace age, also known as furnace lining life, refers to the total number of furnaces made during the intermediate frequency furnace lining from putting into use to replacing a new furnace lining. It is a comprehensive index to measure the production level of intermediate frequency furnace. Therefore, the level of the furnace age not only represents the level of technical equipment, process operation, production management, but also determines the productivity and production cost of the intermediate frequency furnace. Hit the furnace material manufacturers to provide you

       As we all know, medium frequency stoves have the characteristics of small size, light weight, fast heating and high efficiency. Favored by foundry enterprises. Mainly used to melt castings and some precision castings with steel, in recent years it has also been used to melt stainless steel. At the same time, the problem of increasing sulfur and phosphorus can be avoided by melting in medium frequency furnace. The P in the liquid iron is not more than 0.075%, and the S is not more than 0.5%.

The refractory material of intermediate frequency furnace is relatively simple, generally using knotting material; Also useful crucible (i.e., shaped furnace).

1 Correctly select the lining material suitable for smelting

It must be clear to everyone that smelting, especially casting, is inseparable from the lining material, and the chemical composition and physical and chemical characteristics of the lining material have a great impact on the service life of the lining. At present, the chemical properties of commonly used lining materials can be roughly divided into: acidic, alkaline and neutral three categories: according to physical properties can be divided into two categories of amorphous materials and stereotyped materials.

1, the characteristics of the lining material

The chemical composition, physical properties and chemical characteristics of the lining material have a great influence on the service life of the lining. Impurities in refractories can form compounds with low melting point at high temperatures, thereby reducing the refractoriness of refractories. With the increase of the impurity content in the refractory material, its refractoriness will decrease, and the service life of the furnace lining will also decrease with the reduction of refractoriness.

In order to extend the service life of the lining, the purity of the refractory material is theoretically required to be as high as possible. In production practice, high-purity refractory materials are reduced by the reduction of mineral resources, and the price is rising again. In order to make the lining material have a more ideal cost performance and practicality, according to the actual situation of the currently commonly used and ordinary lining refractory material (physical and chemical index), a certain amount of other materials are added to the lining refractory material, so that the lining material can produce new compounds and derivative compounds at high temperature, which can better solve the problem of the refractories of the lining refractory material. That is to say, make full use of existing resources, more development of composite lining materials applied to the actual production of smelting.

Different materials of refractory due to their different physical and chemical properties, their ability to adapt to melting conditions is also different, such as resistance to slag erosion, resistance to acute cooling and thermal performance. Therefore, the service life of the lining varies greatly. Especially when smelting high manganese steel, not only the melting temperature is high, but also the melting conditions are relatively harsh, the corrosion of elements such as Fe, Si, Ai, Mn, C in the liquid steel, CaO, S02, Fe0 in the slag is very serious, which leads to the service life of the furnace lining is greatly reduced.

Taking the smelting of high manganese steel and high carbon steel as an example, the quartz sand lining materials we often use in daily life can not bear this heavy responsibility. Because of the low refractoriness and large volume expansion rate of the quartz acid furnace material, the life of the furnace lining is low when used in steelmaking. However, due to the low cost of quartz sand, it has been applied in melting cast iron, especially in continuous operation (the crucible temperature is maintained at 800~1000 ° C), and its life is as high as more than 100 furnaces. Therefore, almost all the use of quartz lining materials for cast iron, and the use of magnesium, magnesium aluminum, magnesium chromium and other dry knoting materials (that is, we often say basic lining materials) can better solve the problem of low fire resistance of lining materials.

2. Improving the furnace life can not be ignored

2.1 Influence of volume on service life of furnace lining

The static pressure of molten steel on the lining is also different with the size of the furnace. The service life of the lining decreases with the increase of its capacity.

At present, most of the smelting equipment we use is non-vacuum induction furnace. With the increase of furnace capacity, the static pressure of liquid steel on furnace lining wall increases. In general, the static pressure strength of the lining of a 1-ton furnace is 150 kg; the static pressure strength of the lining wall of a 10-ton furnace is 500 kg. It can be seen that the greater the furnace capacity, the greater the static pressure on the furnace wall. Therefore, the liquid steel in the large furnace is easier to penetrate into the lining wall along the capillary channel of the lining refractory, so that the lining is quickly destroyed. As the capacity of the furnace increases, the frequency of the power used decreases. The lower the frequency, the greater the stirring force, and the greater the impact force borne by the furnace lining wall. The electromagnetic stirring force in the liquid steel is inversely proportional to the square root of the frequency of the power supply, and the scouring force borne by the lining wall of the 3-ton furnace is 150 kg. Therefore, as the furnace capacity increases, the erosion force borne by the furnace lining wall also increases.

2.2 Erosion of furnace lining materials by melting temperature.

When the melting temperature is greater than 1700℃, the viscosity of the liquid steel will also drop sharply, the damage speed of the lining will be accelerated, and the life of the lining will be greatly reduced. Therefore, the control of melting temperature will be directly related to the service life of the furnace lining. It can be seen that adding a certain amount of other materials to magnesia refractory can better solve the problem of thermal expansion of pure magnesia lining material.

2.3 Influence of composition of liquid steel on service life of furnace lining

Fe, Si, Ai, Mn, C in liquid steel, and even metal vapor, CO gas, etc., including CaO-related fine SiO2 and FeO in slag along the refractory capillary channels; Infiltrate the interior of the refractory. These infiltrating components are deposited in the capillary channels of refractory materials, resulting in the discontinuity between the physical and chemical properties of the refractory working surface and the original refractory matrix, and cracks, spalling and structural porosity will occur under the sudden change of operating temperature. Strictly speaking, this damage process is much more serious than the dissolution damage process.

2.4 Erosion of furnace slag to lining materials

With the increase of the furnace capacity, the proportion of heat lost on the surface of the liquid steel decreases, the slag temperature is higher than that of the low-capacity furnace, and the flow of the slag is better than that of the low-capacity furnace, so the erosion of the furnace lining is intensified, and the large induction furnace uses the method of mixing steel slag to produce steel, requiring the slag to have good flow in order to adapt to the conditions of steel production. Therefore, the erosion of slag line is serious, which is another reason for the decline of the service life of the furnace lining. Due to the above reasons, the service life of large induction furnace lining is lower than that of small and medium-sized induction furnaces, and the thickness of the crucible lining should be appropriately increased from the point of view of improving the service life of the lining. However, with the increase of furnace lining wall thickness, the resistance value increases, the reactive power loss increases, and the electrical efficiency decreases. Therefore, the thickness of the furnace lining wall is limited to a certain range. Therefore, it is necessary to select a reasonable wall thickness, which has a direct impact on the electrical efficiency and the service life of the furnace lining.

The basicity of the slag should be compatible with the material of the furnace lining. Magnesium lining material can be eroded by high CaO slag and SO2 slag. The amount of CaF in the slag should be controlled. Excessive CaF will erode the basic furnace lining and cause premature corrosion in the slag line area.

Basic slag is suitable for magnesium lining, acid slag is suitable for quartz lining, magnesium aluminum lining can only use weak alkaline or neutral slag. When the basicity of slag is low, the erosion of magnesia lining is more serious, and the life of furnace village is reduced accordingly. On the contrary, when the slag basicity is high, the erosion of the lining is slight, and the life of the lining is relatively improved. When the fluorine ion and metal manganese ion in the slag are high, the erosion of the magnesium lining is also more serious, and the life of the lining is reduced.

The service life of lining is longer than that of non-vacuum melting when slag free melting is performed under vacuum. This proves that slag will reduce the service life of the lining. Therefore, suitable lining materials should be selected according to the properties of slag.

2.5 Influence of knotting density of furnace village on service life of furnace lining

The knotting density of the lining directly affects the service life of the lining. Therefore, the selection of the right lining material only sets the foundation for improving the furnace age, so improving the knotting density of the lining is the key to improve the furnace age.

To get a knotted and dense lining (whether dry or wet), the following points must be done

1, knot the bottom of the furnace: three to four times filling, knot;

2, tying furnace wall: layer by layer, each layer of packing thickness should not be greater than 15 cm;

3, after each layer is knotted, the knotted surface must be shaved, and then the next layer, so that the joint is fully combined, and the fault phenomenon is eliminated from the root. Especially where the bottom meets the wall.

4. Before tying the furnace lining, the site must be carefully and cleanly cleaned. ** Allow the impurities containing iron to be mixed into the lining material, so as to avoid the formation of iron accumulation and coagulative iron phenomenon caused by the lining material mixed with iron debris under the action of potential voltage.

The knotting quality of the lining is directly related to the sintering quality. It is required that the uniform distribution of sand particle size does not produce thickness segregation during knotting, and the sand layer will have high density after knotting. In this way, the probability of cracking after sintering is reduced, which is conducive to improving the service life of the crucible. In the knotting process, the common defects include the phenomenon of low density, uneven and delamination of coarse and fine particle size sand (which is often called particle size segregation). This is especially evident when there is little water or dry knotting.

2.6 Influence of the sintering degree of lining on the service life of lining

The knotting density of the lining directly affects the service life of the furnace village, and the sintering process of the lining determines the key point of the lining strength. Therefore, the sintering of the lining varies from the temperature rise rate in the low temperature zone to. Both the sintering temperature and the holding time have an important effect on the sintering quality of the lining. The escape rate of water vapor during low temperature baking can not be too fast to avoid early cracks in the sand. The source of water in the furnace lining is the water adsorbed by the sand, the crystal water and the water released by the decomposition of the additives, which are all excluded below 800 ° C. So we have to control the rate of warming in this interval. The greater the capacity of the furnace, the lower the heating rate to avoid the rapid escape of water vapor from the sand. Sand of different materials should choose the appropriate sintering temperature and holding time in order to obtain the ideal sintering structure. In high temperature sintering, the sintering structure of the lining is the basis of increasing the service life. Insufficient sintering temperature and insufficient sintering layer thickness will significantly reduce the service life of the lining. In order to obtain long life lining, the ideal sintered structure must be obtained in advance.

2.7 Furnace repair is one of the important measures to improve the furnace life, and the erosion condition of the furnace lining must be checked frequently after opening the furnace. When there is a large crack in the lining, it should be repaired (small cracks do not need to be repaired, it can heal itself at high temperature).

When repairing the furnace, the surface layer of the damaged place should be removed first, washed with 5% boric acid water, and then the same material as the furnace charge is inlaid in the damaged place, and the furnace is fully opened with a rubber hammer, and the furnace top is covered to avoid a sharp drop in the temperature of the furnace lining. The rapid heating and cooling of the lining, especially normalizing, seriously affects the structure of the lining and shortens its service life.

3 Conclusion

1) The improvement of the quality of refractory materials is the basis, and the densification of the lining, the optimization of the steelmaking process, the reduction of the steelmaking temperature, and the timely replenishment of the furnace are the key to improving the furnace life.

2) Reasonable use of appropriate amounts of binders, binders, additives will also improve the overall quality of the lining. For example, adding a certain proportion of high aluminum material to the magnesium lining material makes it generate magnesia-aluminum spinel phase under high temperature, which is also conducive to improving the service life of the lining.

3) Improving the furnace age can reduce production costs, increase output, and reduce the labor intensity of workers. At the same time, it also plays a driving and promoting role in production technology and management.

The above information is provided by the furnace material manufacturer! Welcome to telephone consultation!