Electric furnaces Or laboratory furnace is a device that has a completely insulated chamber with refractory bricks, refractory cement and refractory cotton. This chamber is created by strong elements around or the roof of the device, high temperature up to about 1100 degrees Celsius or 1500 degrees Celsius, which is used to melt some materials and also to take the ashes of some other materials. Equipped with thermostat and thermometer It is digital and has the ability to install a digital timer. The outer body is made of oily sheet with electrostatic paint coating. The accuracy of the display in the temperature range of 200 to 1500 degrees Celsius is about 10 to 15 degrees.
Electric furnaces Electric furnaces produce and melt aluminum in large quantities to avoid oxidation of the melt and to prevent the entry of gases from the combustion of fossil burns and to increase the quality of molten aluminum. Are used. The main mechanism of resistance furnaces is the use of heat from the resistance of rods (electrodes) against the passage of current. Usually Resistance They are made of nichrome (nickel, chromium, iron) and chromium (iron, chromium, aluminum). In the type of plant resistance furnaces that are used with a maximum capacity of 500 kg, the plant is made of gray cast iron and the electrical power of this furnace is usually 40 to 80 kW.
Classification of induction furnaces according to their applications:
As you know induction furnaces in terms of Frequency Work can be divided into three general categories.
1. Frequency 50HZ or MAIN FREQUANCY at times
Sometimes their triple frequency is also mentioned in the same category.
2. Medium frequency, which is from the frequency of about 200HZ to about 10KHZ.
3. High frequency which is from 10KHz to several MHz.
Frequency furnaces The tops that are used as melting furnaces have a laboratory aspect.
50 HZ furnaces :
50HZ furnaces, which are mainly made in the form of plants and ducts, have old technology and low general efficiency, and due to their high turbulence, they are mostly used for melting cast iron, and they are still working in some factories today. These furnaces are mostly only economically justified as cast iron holders and in capacities of several tens of tons and are not recommended as melting furnaces, especially since these furnaces can not be produced in low capacities.
Medium frequency furnaces:
Frequency furnaces that are marketed as series furnaces and parallel furnaces.
As you know, the basis of an induction furnace is the passage of an alternating current through a coil, so-called induction furnace coil, which produces electrical losses inside the core, or in other words, melt.
Energy losses in induction furnaces:
The thermal efficiency of a typical rotary kiln is between 12 and 15%. While the electrical efficiency of a frequency converter panel is about 97% and the general efficiency of an induction furnace is about 75% (5 times that of a rotary furnace).
Most of the heat loss in the melting coil is about 18 to 22 percent. Therefore, the meat of the melting tube and its cross-sectional shape are important parameters that must be considered. About 3% of the losses are in the frequency converter panel and a few percent in the communication lines and internal busbars.
Channel To reduce losses, the level of electric current must be increased, which will increase copper consumption and thus increase prices. Of course, in addition to increasing the flow rate of the coil, adding coil pipe meat has other advantages, such as increasing the mechanical strength of the coil and increasing the resistance of the pipe wall when the melt penetrates, thus reducing the possibility of plant explosion.
Melt rate: The amount of energy consumed per kilogram of induction melting furnace with any technology or any type of raw materials to be made has its own efficiency, the result of which will be evident in the amount of energy consumption per kilogram of melting, so-called It is called Melt rate. This parameter will be one of the tools for comparing different furnaces, which will be mentioned in the discussion of comparing internal and external furnaces.
Applications and benefits:
Today, due to the increasing progress of the country in all fields and also the increasing construction process, the need for steel and its products in the country is expanding day by day.
One of the newest and most modern methods of producing steel ingots is the use of induction melting furnaces. Now many European countries fromInduction furnaces They are used for smelting metals and producing steel.
These furnaces melt scrap metal or metal ingots using electric current and the resulting molten material is produced in the form of steel ingots in the molds after evacuation.
Steel ingots prepared by this method are used in rolling mills to produce various types of rebars, angles, studs. The remarkable thing about induction furnaces is that they have a very high melting speed compared to fossil furnaces (rotary furnaces). Induction furnaces are produced in various capacities from low to high tonnage, which has made this new industry applicable on a workshop scale to factories. Of course, it is worth mentioning that in the case of high-capacity furnaces, continuous steel billet lines can be used. In this method, the production of molten material from induction furnaces is transferred to a continuous casting line and the billet is removed from it in long sizes. The use of induction furnaces has also become widespread due to its high operating speed in the component manufacturing industry. So that many casting and part production units are now replacing old furnaces with induction furnaces, which plays an important and vital role in increasing the profitability of these units. According to the above, it can be concluded that the production of steel ingots and casting parts using induction furnace technology is a safe and profitable way to compensate for the shortage of steel ingots and reduce its imports. Of course, the use of this method is now very fast and widespread, and many investors are inclined to this production method.
Induction furnace is one of the non-contact heating materials. In these furnaces, high or medium frequency current for heating Electrical conductor materials is used. Because this method is non-contact, it does not cause contamination or impurities in the load.
In the past, fossil fuel furnaces were mostly used to melt metals. Environmental pollution, low efficiency, high noise, melt unevenness, inability to melt refractory metals and the like were the problems that these furnaces brought.
In induction melting furnaces, an electric current induced by a magnetic field generates heat, and this heat causes the body (usually metals) to melt. The metal is placed inside a plant around which magnetic coils are wrapped and cooled by a stream of water.
The current in the magnetic coils induces eddy currents in the metal, which cause the metal to heat and melt.
In a metal core induction furnace, it is kept inside a refractory cover surrounded by a coil. In this case the induction melting furnace is similar to one Transformers It works in such a way that the metal acts like a secondary coil in the transformer, and by applying force to the primary coil surrounding the metal, eddy currents are induced and heat is generated.
After melting the metal, stirring and homogenization occur naturally due to the presence of electromagnetic forces and currents. By carefully selecting the frequency and force, the melting rate and homogenization can be controlled
Advantages of induction furnaces compared to other furnaces:
1- Very simple operation due to the existence of a complete electronic control section
2- No pollution and oxidation of the load due to the absence of oxidizing gas and flame
3- Start working quickly and do not need preheating or initial melting
4- High speed of operation in comparison with other furnaces
5- Much higher efficiency compared to fuel furnaces
6- Ability to prepare uniform alloys due to rotation inside the melt
7- Ability to prepare and maintain melts in different capacities
8- Simplicity of feeding and emptying
9- Possibility of precise temperature control
10- Ability to melt scrap
11- Occupy less space than other furnaces
12- No effect on environmental pollution
Different parts of induction furnaces are:
Includes steel frame of furnace, coil, fireproof wall – transformer core, platform (platform)
Induction furnace electrical installations such as choke transformers, capacitors, high pressure switches and control circuit boards can operate for a certain period of time and if they become hotter than a certain limit, they will cause problems, so these installations must be cooled. Electric can be done by fan, air conditioning or air conditioner.
Coils and furnace bodies in bush and couple furnaces, inductor shell, cooling shell and furnace neck must also be cooled in duct furnaces. These parts are generally cooled with water (some small duct furnaces are such. They are designed that all the above parts or part of it is cooled by air) and have special facilities including heat exchangers, pumps, cooling towers, etc., and usually the purpose of cooling facilities is this part.
Plant movement facilities
For large furnaces Hydraulic It is mechanical or hydraulic for small furnaces and includes hydraulic jacks, hydraulic pumps, oil tanks, valves, filters, other hydraulic installations and hydraulic control tables, or manual or motorized gear systems.
Location of the furnace
Includes plant place (furnace pit), foundation, emergency drain hole, electrical, hydraulic and cooling installations and location of control circuit boards, water circuit control panel and hydraulic control table.
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