High frequency furnace for melting metal. Diagram and principle of operation of an induction furnace. Video

Induction heaters can be divided into industrial and household. One of the main methods of generating heat for melting metal in the metallurgical industry is induction furnaces. Devices operating on the induction principle are complex electrical equipment and are sold in a wide range.

Induction technology is the basis of such devices from our everyday life as microwaves, electric ovens, induction cookers, hot water boilers, furnace heating system. Kitchen stoves with the induction operating principle are convenient, practical and economical, but require the use of special utensils.

The most common stoves in everyday life are those using the induction principle of operation for heating rooms. Options for such heating are boiler installations or autonomous units. Induction furnaces are indispensable in jewelry making and small workshops. small size for melting metal.

Advantages of Melting

Induction heating is direct, non-contact and its principle allows the generated heat to be used with maximum efficiency. The efficiency factor (efficiency) when using this method tends to 90%. During the melting process, thermal and electrodynamic movement of the liquid metal occurs, which contributes to uniform temperature throughout the entire volume of the homogeneous material.

Technological potential of such devices creates advantages:

performance – can be used immediately after switching on;
high speed of the melting process;
possibility of adjusting the melt temperature;
zonal and focused energy orientation;
uniformity of molten metal;
no waste from alloying elements;
environmental cleanliness and safety.

Benefits of heating

Scheme

To a master who can read electrical circuits, it is quite possible to make a heating furnace or an induction melting furnace with your own hands. Feasibility of installation homemade unit Each master must determine for himself. It is also necessary to have a good understanding of the potential danger from poorly executed such structures.

To create a working furnace without ready-made scheme must have understanding of the basics of physics induction heating. Without certain knowledge, it is not possible to design and install such an electrical device. Device design consists of development, design, and diagramming.

For those smart owners who need a safe induction furnace, the circuit is especially important, as it combines all the best practices of a home craftsman. Such popular devices as induction furnaces have a variety of assembly schemes, where craftsmen have the opportunity to choose:

oven containers;
operating frequency;
lining method.

Characteristics

When creating an induction melting furnace with your own hands, you need to consider certain specifications , affecting the melting rate of the metal:

generator power;
pulse frequency;
losses due to eddy flows;
hysteresis losses;
heat transfer intensity (cooling).

Principle of operation

The basis of the induction furnace is to obtain heat from the electricity generated alternating electromagnetic field(EMF) inductor (inductor). That is, electromagnetic energy is converted into vortex electrical energy, and then into thermal energy.

Eddy currents closed inside bodies release thermal energy, which heats the metal from the inside. Multi-stage energy conversion does not reduce the efficiency of the furnace. Because of simple principle jobs and opportunities self-assembly schemes increase the profitability of using such devices.

These efficient devices V simplified version and with reduced dimensions they operate from a standard 220V network, but a rectifier is required. In such devices, only electrically conductive materials can be heated and melted.

Design

An induction device is a kind of transformer in which powered from a source alternating current inductor - primary winding, the heated body is the secondary winding.

The simplest low-frequency heating inductor can be considered an insulated conductor (straight core or spiral) located on the surface or inside a metal pipe.

Main components of the device, working on the principle of induction, consider:

Power from the generator launches powerful currents of varying frequencies into an inductor, which creates an electromagnetic field. This field is a source of eddy currents, which are absorbed by the metal and melt it.

Heating system

When installing homemade induction heaters in a heating system, craftsmen often use inexpensive models of welding inverters (DC-AC voltage converters). The energy consumption of the inverter is high, so for permanent job such systems you need a cable with a cross section of 4–6 mm2 instead of the usual 2.5 mm2.

Such heating systems must be closed and automatically controlled. Also, for operational safety, a pump is required for forced circulation coolant, devices for removing air trapped in the system, pressure gauge. The heater must be located at least 1 m from the ceiling and floor, and at least 30 cm from walls and furniture.

Generator

The inductors receive power from the industrial frequency setting of 50 Hz in the factory. And from generators and converters of high, medium and low frequencies (individual power supplies), inductors work in everyday life. It is most effective to involve high-frequency generators in the assembly. Can be used in mini induction ovens currents of different frequencies.

The alternator should not produce a hard current spectrum. According to one of the most popular schemes for assembling induction furnaces in domestic conditions, a generator frequency of 27.12 MHz is recommended. One of these generators is assembled from the following parts:

4 tetrodes (electron tubes) of high power (6p3s brand), with parallel connection;
1 additional neon light - indicator that the device is ready for operation.

Inductor

Various modifications of the inductor can be presented in the shape of a trefoil, a figure of eight, and other options. The center of the assembly is an electrically conductive graphite or metal blank, around which the conductor is wound.

Good up to high temperatures graphite brushes heat up(melting furnaces) and nichrome spiral ( heating device). The easiest way to make an inductor is in the form of a spiral, the internal diameter of which is 80–150 mm. The material for the heating coil of the conductor is also often a copper tube or PEV 0.8 wire.

The number of turns of the heating coil must be at least 8–10. The required distance between turns is 5–7 mm, and the diameter of the copper tube is usually 10 mm. The minimum gap between the inductor and other parts of the device must be at least 50 mm.

Kinds

Distinguish types of induction furnaces with your own hands:

channel - the molten metal is located in a groove around the inductor core;
crucible - the metal is located in a removable crucible inside the inductor.

In large industries, channel furnaces operate from industrial frequency devices, and crucible furnaces operate at industrial, medium and high frequencies. In the metallurgical industry, crucible type furnaces are used for smelting:

cast iron;
become;
copper;
magnesium;
aluminum;
precious metals.

Channel type induction furnaces are used in smelting:

cast iron;
various non-ferrous metals and their alloys.

Duct

Induction oven channel type must have when warming up electrically conductive body in the heat generation zone. During the initial startup of such a furnace, molten metal is poured into the melting zone or a prepared metal template is inserted. Upon completion of metal smelting, the raw materials are not completely drained, leaving a “swamp” for the next smelting.

Crucible

Crucible induction furnaces are the most popular among craftsmen because they are easy to use. A crucible is a special removable container placed in an inductor along with metal for subsequent heating or melting. The crucible can be made of ceramics, steel, graphite and many other materials. It differs from the channel type in the absence of a core.

Cooling

Increases the efficiency of the melting furnace in industrial environments and in domestic small factory-made appliances cooling. In case of short-term work and low power homemade device You can do without this function.

Perform the cooling task yourself home handyman does not seem possible. Scale on copper may lead to loss of functionality of the device, so regular replacement of the inductor will be required.

In industrial conditions, water cooling is used, using antifreeze, and is also combined with air cooling. Forced air cooling in home-made household appliances is unacceptable, since the fan can draw EMF onto itself, which will lead to overheating of the fan housing and a decrease in the efficiency of the stove.

Safety

When working with the oven, you should beware of thermal burns and take into account the high fire danger device. While the devices are operating, they must not be moved. You need to be especially prudent when installing heating stoves in residential premises.

EMF affects and heats the entire surrounding space, and this feature is closely related to the power and frequency of the device’s radiation. Powerful industrial devices can affect metal parts next to you, on people’s fabrics, on objects in their pockets.

The possible impact of such devices on people with implanted pacemakers during operation must be taken into account. When purchasing devices with an induction operating principle, you must carefully read the operating instructions.

MELTING FURNACE is a device designed for melting a charge of ferrous or non-ferrous metal. The advantages are that the melting mass is perfectly mixed if an induction melting furnace is used for melting metal, due to the action of eddy electric currents. You need a melting furnace with good characteristics? ZAVODRR- transistor, thyristor furnaces for copper, cast iron, aluminum, steel for 5 - 5000 kg.

How are melting furnaces constructed?

How do smelting furnaces work? MELTING FURNACES are a good way to melt both ferrous and non-ferrous metals, such as aluminum, steel, cast iron, stainless steel, copper. Induction melting furnaces have a simple design, operate under the force of an electromagnetic field, and are capable of uniformly mixing the metal during melting. Induction furnaces have a lid and a device for draining metal into a casting ladle. The ROSINDUKTOR company offers melting furnaces of transistor or thyristor design with gearboxes and hydraulics.

The advantage of gearbox furnaces is the possibility of manual (emergency) draining of metal; hydraulics is the smooth tilt of the melting unit. Melting furnaces are supplied with one or two melting units, and an inductor is located inside each melting unit. The inductor is made in the form of a copper coil consisting of many turns; the tube can be either round or rectangular in cross-section.

The melting unit is cooled using a chiller or cooling tower. During metal melting, it is necessary to cool two circuits: the reactor (located inside the thyristor converter) and the inductor of the melting unit itself. The melting unit has two versions of the crucible: graphite and lined (made manually from a lined mixture). Graphite crucibles are used for melting non-ferrous metals; for ferrous metals, a lining is used.

Nizhny Novgorod
Chelyabinsk
Krasnoyarsk
Minsk Belarus
Chelyabinsk
Permian
Mound
Chelyabinsk
Moscow
Orenburg
Kazan
Volgograd
Chelyabinsk
Chelyabinsk
Lugansk
Ulyanovsk
Chelyabinsk
Arkhangelsk

Melting furnaces - transistorized

The transistor induction melting furnace is designed for the mixture of ferrous and non-ferrous metals. It is produced on the basis of mid-frequency induction heater, which is assembled using MOSFET transistors and IGBT modules, which allows you to save up to 35% on electricity, having a high efficiency of 95%.

Transistor based induction melting furnaces are suitable for small industrial foundries that need to remelt a small amount of metal The advantages of melting furnaces include their mobility and ease of maintenance, since they use a graphite crucible, which saves time on making the lining and drying it.

The Rosinductor company offers to buy LEGNUM induction melting furnaces (Taiwan); these furnaces are the most popular among Russian buyers. Thyristor induction melting furnaces Legnum are supplied in two modifications: hydraulics and gearbox, the main buyers are medium and large smelting plants with a capacity of 2000 tons/year.

The induction melting furnace is supplied with two melting units; they are installed on a pre-prepared foundation. The main advantages are efficiency, on average 20-30% more economical than any other analogues presented on the Russian market, reliability, modern design And affordable price. Rosinductor supplies induction melting furnaces not only to all regions of RUSSIA, but also to the countries of the former CIS. By contacting our company, rest assured that the induction melting furnace you buy is guaranteed best price, quality, reliability and delivery conditions.

The advantage of melting metal in melting furnaces is cost-effectiveness. This is due to the release of a large amount of heat when heating the metal, so the furnaces consume relatively little power. If we make a comparison between transistor and thyristor furnaces, then the former are 25% more economical, but their cost for the same power is noticeably higher. The most common furnaces have a melting temperature of 1650 °C; at this temperature any non-refractory charge can be melted.

During metal melting, the furnace is controlled mechanically or remotely. In both cases, the process must be managed by trained personnel with appropriate permits and approvals. The Rosinductor company performs work on setting up converters, troubleshooting and maintaining smelting equipment in working order.

When choosing a melting furnace, you need to think about the choice of crucible. This determines what metal will melt and how many melts it can withstand. On average, the crucible can withstand from 20 to 60 heats. For a long service life of the crucible, you must use high-quality and reliable materials. The melting time of metal takes no more than 50 minutes in a heated melting furnace, so a furnace of small volume and power can have high performance.

The delivery set of melting furnaces includes the main elements: thyristor or transistor frequency converter, melting units, capacitor banks, templates, water-cooled cables, control panels, cooling systems.

Induction melting furnace 5 - 5000 kg

Induction melting crucible furnace on 5 - 5000 kg swimming trunks, in a lightweight aluminum alloy body, with TFC and tilt gear. An induction crucible furnace with a thyristor converter is designed for melting ferrous and non-ferrous metals in foundries. The furnace is used to heat molten copper, steel and cast iron. Round-the-clock operation of the furnace is possible if necessary.

Melting furnaces for aluminum

Melting furnaces for aluminum have their own characteristics, because the melting point of aluminum is 660 °C (390 kJ/kg). When choosing a furnace for aluminum, you should know that the thyristor converter should not be powerful, and the melting unit itself differs in size from the unit for steel or copper by 2-3 times. Accordingly, it is not recommended to melt other metals in it.

Melt aluminum alloys possible in furnaces with oil, gas and electric heating, in flame reverberatory furnaces, but the highest quality metal and high speed are obtained when melting in induction melting furnaces, due to the homogeneous composition of the charge, which mixes well in the induction field.

Melting furnaces for steel

Melting furnaces are heated to their maximum temperature when melting steel, 1500 - 1600 ° C and are accompanied by complex physical and chemical processes. When remelting steel, it is necessary to reduce the content of oxygen, sulfur and phosphorus, which form oxide and sulfide elements, which reduce the quality of steel.

A feature of steel melting in melting furnaces is the use of lining mixtures, in contrast to copper melting, where a graphite crucible is used. Melting furnaces mix metal well due to the induction field, which evens out chemical composition become.

The above advantages are excellent for smelting alloy steels, with minimal losses of alloying elements: tungsten - about 2%, manganese, chromium and vanadium - 5 - 10%, silicon - 10 - 15%, taking into account the scarcity and high cost of alloying elements.

Steel melting has the following features and advantages:

The most important castings are melted using the oxidation method, because during the boiling of the metal, all non-metallic inclusions are removed and the phosphorus content is reduced. The composition of the charge is taken from scrap carbon steel or cast iron to obtain an average carbon content of 0.5%;
If you are going to melt steel with a high content of manganese, aluminum, chromium, you need to choose an acid lining, because the durability of the crucible will be twice as high;
Before starting melting, the crucible is filled with metal, but the top should not be filled tightly, this can lead to the formation of arches and, accordingly, waste of metal, since the charge will settle during melting of the lower pieces;
The steel melting time ranges from 50-70 minutes, depending on the heating of the melting unit;
Melting furnaces for steel have high productivity in the production of castings of small mass and size.

Copper, copper alloys, bronze, brass can be melted in all melting furnaces where the temperature is maintained at 1000 - 1300 °C. However, it is preferable to use induction melting furnaces, since one melt in them will not exceed 40 minutes. The copper used in Russia today is not particularly pure. Typically it contains the following impurities: iron, nickel, antimony, arsenic. Copper with an impurity content of 1% is considered pure metal.

The main important quality of the metal is its high electrical and thermal conductivity. This determines the low temperature for melting. Copper smelting temperature is 1084°C. Copper is a fairly flexible metal that is widely used in various technical industries; here are some of its features:

Copper can be melted in an open environment, in a vacuum and in a protective gas environment;
Copper is melted in a vacuum to obtain oxygen-free copper, with the ability to reduce O (Oxygenium) oxygen to almost zero 0.001%;
The main charge when producing oxygen-free copper is 99.95% cathode sheets; before loading the sheets into the furnace, they must be cut, washed and dried from the electrolyte;
The lining of the melting furnace above the metal level is made of magnesite;
To avoid oxidation, smelting is carried out using charcoal, fluxes, glass and other components.

Induction furnace for metal melting

An induction furnace for metal melting heats the metal charge with high frequency currents (HFC) in an induced electromagnetic field under the influence of eddy electric currents. Melting furnaces consume a large amount of electricity, so we offer furnaces not only with a thyristor converter, but also with an economical transistor converter. The furnace uses a lining or a graphite crucible, in both cases they are only enough for 20-40 melts. Heat melting, allows you to produce one metal melt in 50 minutes.

ZAVODRR- furnaces for melting metals from Russian, Asian and European manufacturers with a crucible capacity from 1 to 10,000 kg. Supply, installation, commissioning and inexpensive maintenance of furnaces.

Let's look at the features of furnaces for melting ferrous, non-ferrous and precious metals:

Aluminum smelting furnace (aluminum smelting in furnaces is carried out at a temperature of 660 °C, boiling point 2400 °C, density 2698 kg/cm³);
Furnace for smelting cast iron (cast iron smelting 1450 - 1520 °C, density 7900 kg/m³);
Copper smelting furnace (copper smelting 1083°C, boiling point 2580°C, density 8920 kg/cm³);
Furnace for gold smelting (gold smelting 1063°C, boiling point 2660°C, density 19320 kg/cm³);
Silver smelting furnaces (silver smelting 960°C, boiling point 2180°C, density 10500 kg/cm³);
Furnace for steel melting (steel melting in furnaces 1450 - 1520 °C, density 7900 kg/m³);
Iron smelting furnace (iron smelting 1539°C, boiling point 2900°C, density 7850 kg/m3);
Furnaces for melting titanium alloys (titanium melting 1680°C, boiling point 3300°C, density 4505 kg/m³);
Furnace for lead smelting (lead smelting in furnaces 327°C, boiling point 1750°C, density 1134 kg/cm³);
Brass smelting furnace (brass smelting in furnaces 880–950 °C. density 8500 kg/m³);
Bronze smelting furnaces (bronze smelting in furnaces, 930–1140 °C 8700 kg/m³).

The plate is the key element household appliances, which is impossible to do without in any kitchen.

And if earlier housewives’ assistants were electric and, now induction stoves are gaining popularity. And this is justified, because they have a lot of undeniable advantages: fire safety, efficiency, high speed heating and cooking.
Induction ovens - the most modern household appliances for the kitchen

Working principle of induction furnace

The induction oven appeared on the household appliances market in the 80s of the last century, but the invention was treated with distrust due to the high cost and unclear operating principle. Only after restaurateurs began to use induction hob and felt its advantages, housewives who wanted to simplify and speed up cooking took advantage of their example.

The operating principle of induction cookers is based on the use of magnetic field energy. There is a glass-ceramic copper coil underneath, when passing through the turns of which the electric current is converted into induction. When a cookware with a magnetic bottom is placed on a burner, the current acts on the electrons of its ferromagnetic material, causing them to move. As a result of this process, heat is released, due to which the cookware heats up and the contents in it enter the cooking stage.

To cook on an induction hob you need special cookware

Induction is fundamentally different from electric and gas in the following aspects:

Heating the coating. In traditional stoves, the burner heats up first and then transfers the heat to the cookware sitting on it. Induction heating involves heating the bottom of a frying pan or pan directly. Glass ceramic panel At the same time, it heats up from the dishes, and after removing them cools down for 5 minutes.
Efficiency. Induction electric stoves have an efficiency of 90% due to the fact that energy is not wasted on heating the burner, but acts on the bottom of the pan.
Energy saving. The temperature adjustment of the induction furnace occurs almost instantly, which leads to rational energy consumption.
Safety. When the stove is operating, the panel itself does not heat up, so you don’t have to worry about getting burned.

Features of cooking

Housewives often deliberately refuse to purchase electric induction stoves because they are afraid of difficulties when turning on and cooking. In fact, there is nothing difficult about turning on an induction cooker.

After connecting the device to the power source, a signal will sound indicating the possibility of turning on hob. Each zone has a power regulator and a customizable timer.

Unusual design induction cooker

How to cook on an induction hob is described in detail in the instructions for its use. There are marked temperature conditions and power parameters required for a specific cooking process of a particular dish. For example, boiling water occurs at levels 7-9, extinguishing - 5 or 6.

Types of slabs

The household appliances market offers ovens of varying functionality and cost. Users can purchase both inexpensive induction cookers for the kitchen and multifunctional systems installed in cafes and restaurants.

The main types of this equipment include:

compact tabletop induction cookers with one or more burners;
built-in appliances or separate hobs;
combined stoves - combine elements operating on the principle of magnetic induction and electric heating burners.

Combined induction-gas stove

When choosing a stove based on magnetic field energy, you should pay attention to the power capabilities and the number of modes. Intensive heating function allows you to cook food faster .

Infrared sensors monitor maximum heating bottom of the pan and prevent food from burning: in my opinion, this function is necessary in the appliance.

It’s also worth thinking about the shape of the burner: it can be flat or recessed. The possibility of using dishes with different bottoms will depend on this. Multifunctional devices, such as induction cookers with an oven and a large number of burners, will allow you to cook several dishes at the same time.

Specifications

Depending on the type and cost, electric induction furnaces have the following technical characteristics:

maximum heating temperature is 60 degrees Celsius;
power ranges from 50-3500 W;
the number of adjustment modes varies from 12 to 20 depending on the type of device;
devices are equipped with a touch panel;
the heating element operates on the basis of induction;
The device is equipped with a timer.

Like any equipment, this one is not immune to breakdowns, but finding spare parts for induction cookers is not difficult. In addition, people who understand the laws of physics can easily make an induction cooker with their own hands. However, remember that you should take on this business only if you have the necessary knowledge and experience.

Selecting cookware for an induction cooker

Many housewives are sure that they will have to buy all the cookware for the induction cooker again, since the existing one will not fit. This is not entirely true.

To put an induction hob into operation, you must use cookware that has ferromagnetic properties. Checking this is quite simple: you need to attach a magnet to the bottom. If it sticks, the pan is suitable for use on the stovetop.

Iron, enameled and cast iron pans have ferromagnetic properties. Glass, ceramic, porcelain and copper containers are not suitable for ovens that use magnetic field energy.

If there are no suitable pots and pans available, choosing cookware for induction cookers will not be difficult if you use a few tips:

bottom induction cookware must have a diameter of at least 12 cm to ensure optimal area contact with the surface of the stove;
the thickness of the bottom of a grill pan for an induction cooker or other container must be at least 2 and no more than 6 mm;
the bottom surface should be smooth, without bends;
The symbol on the cookware for induction cookers, which looks like a horizontal spiral and indicates the use of ferromagnetic material, can help in choosing the right container.

There are many companies producing pots, frying pans, stewpans, fryers and even Turks for induction cookers. Therefore, buying them will not be difficult.

WATCH THE VIDEO

If it is not possible to purchase a full set of special cookware, you can use an adapter for an induction cooker. It is a disk 2-3 mm thick with different diameters depending on the size of the pots and pans. The principle of operation is as follows: the coil transfers heat to the adapter for the induction cooker, which, in turn, heats the cookware standing on it. When using such a device, it is not necessary to buy a special kettle for an induction cooker; you can easily use your favorite ceramic one.

An induction furnace is a heating device where the induction method is used to melt steel, copper and other metals (the metal is heated by currents excited by a non-alternating field of the inductor). Some consider resistance heating devices to be one of the types, but the difference is method of energy transfer heated metal. First, electrical energy becomes electromagnetic, then electrical again, and only at the very end it turns into thermal energy. Induction stoves are considered the most perfect from all gas and electric (steel-smelting, mini-stoves), thanks to its heating method. With induction, heat is generated within the metal itself, and the use of thermal energy is most efficient.

Induction furnaces are divided into two types:

with core (duct);
without core (crucible).

The latter are considered more modern and useful ( heating devices with a core, due to their design, are limited in power). The transition from channel to crucible furnaces began in early 1900s. At the moment they are widely used in industry.

These types are quite popular electrical appliances, such as muffle melting furnace, steel melting furnace and arc steel melting furnace. The former are very effective and safe to use. There is a large assortment of muffle furnaces of this type on the shelves. The invention of the steel-smelting furnace played a very important role in metallurgy. With its help, it became possible to heat any materials.

However, at the moment, steel smelting is more often carried out using a heating structure such as, it uses the thermal effect for melting, and it is more convenient and practical.
You can make many simple heating structures with your own hands. For example, it is very popular. If you decide to build a mini heating structure with your own hands, you need to know its structure. There are many types of induction furnaces, but we will describe only a few of them. If necessary, you can use the necessary diagrams, drawings and video recordings.

Induction Furnace Components

For the simplest designs, there are only two main parts: an inductor and a generator. However, you can add something of your own, improve the unit, using the necessary circuits.
Inductor
The heating coil is the most important component. Absolutely the entire operation of the heating structure depends on it. For homemade stoves with low power it is permissible to use an inductor made of a bare copper tube with a diameter of 10 mm. The inner diameter of the inductor should be not less than 80 mm. and no more than 150 mm., number of turns – 8-10. It is necessary to take into account that the turns should not touch, so the distance between them should be 5-7 mm. Also, no part of the inductor should touch its shield.
Generator
The second most important component of the furnace is the alternating current generator. When choosing a generator circuit, you should do everything possible avoid drawings, giving a hard current spectrum. As something that does NOT need to be chosen, we present a popular circuit based on a thyristor switch.

Crucible furnace structure

Inside there is a melting crucible with a drain sock (“ collar“). On the outer sides of the structure, an inductor is located in a vertical position. Next comes a layer of thermal insulation, and at the top is a lid. There may be an inlet on one of the external sides current and cooling water. At the bottom there is a device for signaling crucible wear.

The melting crucible is one of the most important components of the unit; it greatly determines its operational reliability. Therefore, very stringent requirements are placed on the crucible and other materials used.

How to make an induction oven

First you need to assemble a generator for the inductor. Here you will need the K174XA11 circuit. The transformer should be wound on a mini-ring with a diameter of 2 centimeters. The entire winding is made with a wire with a diameter of 0.4 centimeters and should be 30 turns. The primary winding is characterized by the presence exactly 22 turns of wire with a diameter of 1 millimeter, and the secondary must contain only 2-3 turns the same wire, but already folded four times. The inductor must be made of 3 mm. wires with a diameter of 11 mm. There should be exactly 6 turns. To adjust the resonance, it is best to set it to normal or mini led.

The most advanced type of heating is one in which heat is created directly in the heated body. This method of heating is very well carried out by passing through the body electric current. However, direct inclusion of a heated body in an electrical circuit is not always possible for technical and practical reasons.

In these cases perfect view heating can be carried out using induction heating, in which heat is also created in the heated body itself, which eliminates unnecessary, usually large, energy consumption in the walls of the furnace or in other heating elements. Therefore, despite the relatively low efficiency of generating currents of high and high frequencies, the overall efficiency of induction heating is often higher than.

The induction method also allows for rapid heating of non-metallic bodies evenly throughout their entire thickness. The poor thermal conductivity of such bodies excludes the possibility of their rapid heating inner layers in the usual way, i.e. by supplying heat from outside. With the induction method, heat is generated equally in both the outer layers and the inner ones, and there may even be a danger of overheating of the latter if this is not done necessary thermal insulation outer layers.

Especially valuable property induction heating is the possibility of a very high concentration of energy in the heated body, which is easily amenable to precise dosage. It is only possible to obtain the same order of energy density, however, this method of heating is difficult to control.

The features and well-known advantages of induction heating have created wide possibilities for its use in many industries. In addition, it allows you to create new types of structures that are not feasible at all. in the usual ways heat treatment.

Physical process

In induction furnaces and devices, heat in an electrically conductive heated body is released by currents induced in it by an alternating electromagnetic field. Thus, direct heating takes place here.

Induction heating of metals is based on two physical laws: and the Joule-Lenz law. Metal bodies (blanks, parts, etc.) are placed in, which excites a vortex in them. The induced emf is determined by the rate of change of the magnetic flux. Under the influence of induced emf, eddy currents (closed inside the bodies) flow in bodies, releasing heat. This EMF creates in the metal, thermal energy, released by these currents, causes the metal to heat up. Induction heating is direct and non-contact. It allows you to reach temperatures sufficient to melt the most refractory metals and alloys.

Intense induction heating is possible only in electromagnetic fields of high intensity and frequency, which create special devices- inductors. The inductors are powered from a 50 Hz network (industrial frequency settings) or from individual power sources - generators and converters of medium and high frequencies.

The simplest inductor for low frequency indirect induction heating devices is an insulated conductor (elongated or coiled) placed inside a metal pipe or placed on its surface. When current flows through the inductor conductor, heaters are induced in the pipe. Heat from the pipe (it can also be a crucible, container) is transferred to the heated medium (water flowing through the pipe, air, etc.).

Induction heating and hardening of metals

The most widely used is direct induction heating of metals at medium and high frequencies. For this purpose, specially designed inductors are used. The inductor emits , which falls on the heated body and is damped in it. The energy of the absorbed wave is converted into heat in the body. The heating efficiency is higher, the closer the type of emitted electromagnetic wave(flat, cylindrical, etc.) to the shape of the body. Therefore, flat inductors are used to heat flat bodies, and cylindrical (solenoid) inductors are used to heat cylindrical workpieces. In general, they may have complex shape, due to the need to concentrate electromagnetic energy in the desired direction.

A feature of inductive energy input is the ability to regulate the spatial location of the flow zone.

First, eddy currents flow within the area covered by the inductor. Only that part of the body that is in magnetic connection with the inductor is heated, regardless of the overall dimensions of the body.

Secondly, the depth of the eddy current circulation zone and, consequently, the energy release zone depends, among other factors, on the frequency of the inductor current (increases at low frequencies and decreases with increasing frequency).

The efficiency of energy transfer from the inductor to the heated current depends on the size of the gap between them and increases as it decreases.

Induction heating is used for surface hardening of steel products, through heating for plastic deformation (forging, stamping, pressing, etc.), melting of metals, heat treatment (annealing, tempering, normalizing, hardening), welding, surfacing, and soldering of metals.

Indirect induction heating is used for heating technological equipment(pipelines, containers, etc.), heating liquid media, drying coatings, materials (for example, wood). The most important parameter induction heating installations - frequency. For each process (surface hardening, through heating) there is an optimal frequency range that provides the best technological and economic performance. For induction heating, frequencies from 50Hz to 5MHz are used.

Advantages of induction heating

1) The transfer of electrical energy directly to the heated body allows direct heating of conductor materials. At the same time, the heating rate increases compared to indirect installations, in which the product is heated only from the surface.

2) The transfer of electrical energy directly to the heated body does not require contact devices. This is convenient in conditions of automated production line production, when using vacuum and protective equipment.

3) Due to the phenomenon of surface effect, maximum power is released in the surface layer of the heated product. Therefore, induction heating during hardening provides rapid heating of the surface layer of the product. This makes it possible to obtain a high hardness of the surface of the part with a relatively viscous core. The process of surface induction hardening is faster and more economical than other methods of surface hardening of a product.

4) Induction heating in most cases allows to increase productivity and improve working conditions.

Induction melting furnaces

An induction furnace or device can be considered as a kind of transformer, in which the primary winding (inductor) is connected to an alternating current source, and the heated body itself serves as the secondary winding.

The working process of induction melting furnaces is characterized by electrodynamic and thermal movement of liquid metal in a bath or crucible, which contributes to obtaining a metal of homogeneous composition and its uniform temperature throughout the entire volume, as well as low metal waste (several times less than in arc furnaces).

Induction melting furnaces are used in the production of castings, including shaped ones, from steel, cast iron, non-ferrous metals and alloys.

Induction melting furnaces can be divided into industrial frequency channel furnaces and industrial, medium and high frequency crucible furnaces.

A channel induction furnace is a transformer, usually of industrial frequency (50 Hz). The secondary winding of the transformer is a coil of molten metal. The metal is enclosed in a refractory annular channel.

The main magnetic flux induces an EMF in the channel metal, the EMF creates a current, the current heats the metal, therefore, an induction channel furnace is similar to a transformer operating in short circuit mode.

The inductors of channel furnaces are made of a longitudinal copper tube, it is water-cooled, the channel part of the hearth stone is cooled by a fan or from a centralized air system.

Induction channel furnaces are designed for continuous operation with rare transitions from one grade of metal to another. Channel induction furnaces are mainly used for melting aluminum and its alloys, as well as copper and some of its alloys. Other series of furnaces are specialized as mixers for holding and superheating liquid cast iron, non-ferrous metals and alloys before pouring into molds.

The operation of an induction crucible furnace is based on the absorption of electromagnetic energy from a conductive charge. The cage is placed inside a cylindrical coil - an inductor. From an electrical point of view, an induction crucible furnace is a short-circuited air transformer whose secondary winding is a conductive charge.

Induction crucible furnaces are used primarily for melting metals for shaped castings in batch mode, and also, regardless of the operating mode, for melting some alloys, such as bronze, which have a detrimental effect on the lining of channel furnaces.