3. The furnace shell of box-type resistance furnace box-type melting aluminum crucible resistance furnace is a rectangular structure welded with steel and steel plates. There is a heating chamber made of high-alumina refractory bricks, between the heating chamber and the furnace shell. Insulation bricks are installed and filled with other high-performance insulation materials to reduce heat loss. The heating element processed by the high-resistance alloy into a spiral shape is arranged on the silk tube at the upper part of the heating chamber, and is connected to the power supply of the external circuit through the withdrawal rod. There are two aluminum slags on the side of the furnace wall, one for normal production and the other for low. In order to facilitate the maintenance of the aluminum liquid, the molten aluminum in the furnace can be drained.
Each side of the upper end of the electric furnace is provided with a protective cover shell, and the wiring device of the heating element inside the cover shell is provided for accessing the 380V power supply.
There are two flexible furnace doors at both ends of the furnace for feeding and slagging. The interlocking device on the furnace door can automatically cut off the power when the furnace r7 is opened to ensure safe operation
Each electric furnace is equipped with two thermocouples, which can automatically control and record the working temperature by connecting the compensating wire and the temperature meter that the control rejects. When the temperature is over temperature, it will automatically alarm.
4. Infrared smelting furnace Infrared smelting furnace is mainly used for the melting of non-ferrous alloys such as Al. Cu and its alloys, using silicon platinum rods as heating elements.
Infrared smelting furnace is mainly composed of electric furnace body and electric appliance control. Infrared smelting furnaces are available in both tiltable and pit styles, and are tilt-mounted on the ground with a pouring device. The inner wall of the furnace is coated with infrared paint, which forms infrared radiation after heating to increase the heating efficiency, which is conducive to the homogenization of the temperature field. At the same time, advanced heat-insulating materials are used for the furnace lining. Therefore, the thermal efficiency is high, the metal melts fast, the burning loss is small, and the unit power consumption is also low. Because graphite is used, the contamination of the alloy with Fe and Si impurities is eliminated, thus ensuring the high purity of the alloy.
5. From the induction heating furnace's heating and smelting principle, the power frequency induction furnace does not limit the type or shape of the metal to be smelted. It does not have the problem of smoke emission like the fuel furnace. Therefore, it helps to prevent pollution. It has a series of advantages such as good smelting quality, less metal loss, convenient power control, easy to implement mechanization, automation, and good working conditions. It has been widely used in the metallurgical industry, machinery industry and many other industrial sectors. From the structural point of view, the induction furnace is divided into two types: centered induction furnace and centerless induction furnace. The centerless induction furnace is divided into an industrial frequency non-hearth furnace with an industrial frequency of 6OW directly and a higher-frequency medium-high frequency induction furnace equipped with a frequency conversion device. The centerless induction furnace consists mainly of the hob, induction coil, and mandarin. The basic structure is shown in Figure 4-3.
It is smelted at high temperature. It is usually made of refractories as the furnace lining of the furnace and covered with slag on the surface of the liquid metal to prevent oxidation of the liquid metal and dissolved gas. Furnace lining is divided into acid lining and alkaline lining. The acid lining is composed of fire-resistant private soil and quartz sand. The acid lining is sturdy and cheap. The energy consumption is low and the yield is high. Acid slag is formed in the smelting process, and the sulfur and dephosphorization cannot be maintained. Alkaline lining is made of magnesia, which produces alkaline slag in the smelting process and has certain dephosphorization and desulfurization capabilities.
The centerless induction melting furnace is also called a site induction furnace and is used to smelt copper, aluminum and its alloys. The most important feature is that the molten metal in the citrus a is strongly stirred by electromagnetic stirring. For a furnace with a certain capacity, the greater the input power, the lower the frequency, and the more significant the electromagnetic effect, so the liquid metal in the industrial frequency furnace The intense movements are beneficial to the homogeneity, alloying and temperature homogenization of the molten metal. Conversely, oxygen may also be entrained in the molten metal due to excessive agitation, causing the metal to oxidize, causing metal loss. Considering the above situation, when designing the industrial frequency furnace for non-ferrous metals, it is necessary to carefully select the appropriate input power and the height of the induction coil that can suppress the flow of molten metal. During the smelting process, low temperature smelting should be carried out in order to continuously install the cold material to the specified liquid level.
The commonly used non-center induction furnace, the current frequency is: frequency OH public, intermediate frequency 50-10000H public, high-frequency 10000H public. When the centerless induction furnace is working, the inductor coil outside the lining is equivalent to the primary winding of the transformer, and the metal charge in the lining is equivalent to the secondary winding. When the induction coil is connected to the alternating current, the short circuit connection is caused by the effect of the alternating magnetic field. The metal charge generates a strong induced current. When the current flows, the metal charge is heated and melted to overcome the heat generated by the resistive surface of the metal charge surface.
The centerless induction furnace has the ability to melt the solid charge, while the induction furnace can only superheat the molten iron, but in the power consumption of the superheated iron, the induction furnace is more economical.
6. Power frequency induction furnace Melting furnace The centered induction furnace is characterized by a closed iron core laminated with silicon steel sheets. This electric furnace works according to the principle of a transformer and uses a power frequency power supply without special equipment. In addition, the existing centered induction melting furnaces are almost all made of dark trenches, that is, the buried trenches are hidden and buried in the molten metal, as shown in Figure 4-4.
Industrial frequency induction furnace has become the basic furnace for nonferrous metal smelting and thermal insulation
This type of electric furnace requires liquid metal to fill the gaps at the beginning of smelting and pouring, so as to form a power loop, so it is only suitable for large-scale smelting or thermal insulation of a single metal.
7. Intermediate frequency induction furnace Smelting furnace intermediate frequency induction furnace is mainly composed of furnace frame, induction coil, tilting furnace mechanism, lining, electrical equipment and other parts. This type of electric furnace has features such as fast heating, low metal consumption, and easy and flexible use. In addition, mid-frequency furnaces do not need as many capacitors as the industrial frequency furnace, and their prices may be further reduced.
8. Vacuum induction melting furnace The vacuum induction melting furnace is a centerless induction melting furnace, except that the citrus vortex is installed in a vacuum chamber. During smelting, the vacuum chamber is evacuated and the charge is smelted and poured in a vacuum. This furnace is suitable for vacuum or aerated smelting and vacuum casting of research and production departments as nickel-base, iron-based and drill-base superalloys casting ingots and castings and other precision alloys, etc.
The electric furnace body of this electric furnace is mainly composed of a furnace body composed of a double-layer water wall, an induction coil, and a citrus vortex, etc. The vacuum system is composed of a vacuum unit and an attached deflation, inflation valve and vacuum indicator instrument; The equipment consists of medium frequency or high frequency power equipment and control rejection
The use of vacuum induction melting equipment to smelt metal materials has two main advantages. One is that most of the gases in the material, such as H2' 0: and N:, can be removed to improve the properties of the material. Second, the oxidation loss of the metal material is small. This type of electric furnace began its industrial application in the 1950s. With the development of vacuum technology and the increase in the need for jet engines for high-temperature alloys, this type of electric furnace has achieved considerable development. Although the number of products is small, the capacity of a single unit is large. . At present, there are vacuum-induction melting furnaces with a capacity of 54 tons (steel-it) in the world. Such large-scale electric furnaces usually use semi-continuous operation, which can perform feeding, pouring and ejecting without destroying the vacuum degree of the melting chamber. Figure 4-5
9. Vacuum induction melting Directional solidification furnace Vacuum induction melting Directional solidification furnace is a special type of furnace. The smelting process is the same as that of the vacuum induction smelting furnace, but it completes casting and casting in the smelting chamber to complete the solidification process of the oriented or single crystal casting. It is mainly used for the production of single crystal and oriented superalloy castings
10. Cold citrus disaster induction shell melting furnace cold spot vortex induction shell melting furnace is mainly used for smelting high melting point, high activity metals and their alloys, especially suitable for the smelting of Chin alloys. Because Chinaloy has a high chemical activity, it is very vulnerable to contamination by refractory materials and gap elements in the smelting process.
This furnace was originally made of conductive citrus smelting metal. Due to the skin effect of the induced current, the induced current on the citrus mandarin was too much, affecting the charge absorption. If the citrus vortex is cooled with water, most of the generated heat is carried away by the water and the charge is hard to melt. After improvement, one or more seams were opened in the Cilan Worm, ceramic insulation was added between the seams, the induced current loops in the locus were cut off, and the smelting efficiency of the charge was greatly improved. The device is shown in Figure 4-6.
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