Induction furnaces were invented as early as 1887. And three years later, the first industrial development used to melt various metals. I would like to note that in those distant years these furnaces were a curiosity. The thing is that scientists of that time did not quite understand what processes were taking place in it. Got it figured out today. In this article, we will be interested in the topic - do-it-yourself induction furnace. How simple is its design, is it possible to assemble this unit at home?

Principle of operation

It is necessary to start the assembly, having understood the principle of operation and the device device. Let's start with this. Pay attention to the picture above, we will understand it.

The device includes:

• Generator G, which creates an alternating current.
• Capacitor C, together with coil L, creates an oscillatory circuit, which provides the installation with a high temperature.
  

  Attention! Some designs use a so-called self-oscillating generator. This makes it possible to remove the capacitor from the circuit.

• The coil in the surrounding space forms a magnetic field in which there is a voltage, indicated in our figure by the letter "H". The magnetic field itself exists in free space, and can be closed through a ferromagnetic core.
• It also acts on the mixture (W), in which it creates a magnetic flux (F). By the way, instead of the charge, some workpiece can be installed.
• The magnetic flux induces a secondary voltage of 12 V. But this only happens if W is an electrically conductive element.
• If the heated workpiece is large and solid, then the so-called Foucault current begins to act inside it. It is of the vortex type.
• In this case, eddy currents are transmitted from the generator through a magnetic field thermal energy thereby heating the workpiece.

The electromagnetic field is quite wide. And even the multi-stage energy conversion that is present in homemade induction furnaces has maximum efficiency– up to 100%.

crucible furnace

Varieties

There are two main designs induction furnaces:

• Channel.
• Crucible.

We won't list them all here. distinctive features. Just note that the channel variant is a design that is similar to welding machine. In addition, in order to melt metal in such furnaces, it was necessary to leave a little melt, without which the process simply did not work. The second option is an advanced scheme that uses technology without residual melt. That is, the crucible is simply installed directly into the inductor.

How it works

Why do you need such an oven at home?

In general, the question is quite interesting. Let's look at this situation. There is enough a large number of Soviet electrical and electronic devices that used gold or silver contacts. These metals can be removed different ways. One of them is an induction stove.

That is, you take the contacts, put them in a narrow and long crucible, which you install in the inductor. After 15-20 minutes, reducing the power, cooling the apparatus and breaking the crucible, you will get a rod, at the end of which you will find a gold or silver tip. Cut it off and take it to a pawnshop.

Although it should be noted that with this homemade unit can be carried out various processes with metals. For example, you can harden or leave.

Coil with battery (generator)

Stove components

In the "Operating principle" section, we have already mentioned all parts of the induction furnace. And if everything is clear with the generator, then the inductor (coil) should be dealt with. A copper tube is suitable for it. If you are assembling a device with a power of 3 kW, then you will need a tube with a diameter of 10 mm. The coil itself is twisted with a diameter of 80-150 mm, with a number of turns from 8 to 10.

Please note that the threads copper tube should not touch each other. Optimal Distance between them 5-7 mm. The coil itself must not touch the screen. The distance between them is 50 mm.

Typically, industrial induction furnaces have a cooling unit. It is impossible to do this at home. But for a unit with a power of 3 kW, work up to half an hour does not threaten anything. True, over time, copper scale will form on the tube, which reduces the efficiency of the device. So periodically the coil will have to be changed.

Generator

In principle, making a generator with your own hands is not a problem. But this is only possible if you have sufficient knowledge in radio electronics at the level of an average radio amateur. If there is no such knowledge, then forget about the induction stove. The most important thing is that you also need to be able to operate this device skillfully.

If you are faced with the dilemma of choosing a generator circuit, then take one piece of advice - it should not have a hard current spectrum. In order to make it clearer what is at stake, we offer the most a simple circuit generator for the induction furnace in the photo below.

Generator circuit

Required knowledge

The electromagnetic field acts on all living things. An example is meat in the microwave. Therefore, it is worth taking care of security. And it doesn't matter if you assemble the stove and test it or work on it. There is such an indicator as the energy flux density. So it depends on the electromagnetic field. And the higher the frequency of radiation, the worse the human body.

Many countries have adopted safety measures that take energy density into account. There are developed limits. This is 1-30 mW per 1 m² of the human body. These indicators are valid if exposure occurs no more than one hour a day. By the way, the installed galvanized screen reduces the density of the ceiling by 50 times.

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The very principle of operation of the induction furnace is that the heat for melting is obtained from electricity, which is generated by alternating magnetic field. In such furnaces, energy is converted from electromagnetic, then to electrical and, ultimately, to heat. How is an induction furnace made by hand?

Such furnaces are divided into two types:

1. Crucible. In such furnaces, the inductor and core are inside the metal. This type of furnace is used in industrial foundries, for melting copper, aluminum, cast iron, steel, as well as in jewelry factories for melting precious metals.
2. Channel. In this type of furnace, the inductor and core are located around the metal.

Compared to boilers or other stoves, induction stoves have several advantages:

• warm up instantly.
• focus energy in a given range;
• environmentally friendly device and relative safety;
• there is no fumes;
• huge possibilities for adjusting temperature and capacity;
• homogeneity of the metal that is being melted.

Induction furnaces are also used for heating. This is a convenient and at the same time silent heating method.

Does not require a special room for the boiler. Scale does not accumulate on the heating element, and any liquid can be used for circulation through the heating system, be it oil, water, and others. Also, the oven is durable, as it wears out minimally. As mentioned earlier, it is very environmentally friendly, because there are no harmful emissions into the air, and it also meets all fire safety requirements.

Collection of information

For a person who understands how to read and understand an electrical circuit, it will not be difficult to figure out how to make such an induction furnace. On the Internet, you will see dozens or even hundreds of options for making various induction stoves using household junk, for example, from an old microwave or welding inverter.

Be sure to remember that electricity- a dangerous thing. And for the manufacture of an induction furnace, you need to have an idea of ​​\u200b\u200bwhat heating using induction is. It is advisable that you have a person with you who understands at least the basics of electrical engineering well or has experience working with electrical equipment.

Principle of operation

The basis of the operation of such a stove is the extraction of heat from an electric current, which produces an alternating magnetic field using an inductor. It turns out that we get heat first from electromagnetic energy, and then from electrical energy. The closed nature of the currents that flow through the turns of the inductor (inductor) generates heat and heats the metal from the inside.

Such a stove can work, have a simplified version and operate from a 220V home network. But this requires a rectifier, that is, an adapter.

Furnace device

The design of an induction device is similar to a transformer. In it, the primary winding is powered by alternating current, and the secondary serves as a heated body.

The simplest inductor is an insulated conductor (having the form of a spiral or core), which is located on the surface metal pipe or inside it.

Here are some knots that work by induction:

• inductor;
• compartment for melting furnace;
• heating element for heating furnace;
• generator;
• frame.

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

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

The most common stoves in everyday life are those with an induction principle of operation for space heating. Options for such heating are boiler plants or autonomous units. Small-sized induction furnaces for metal melting are indispensable in jewelry and small workshops.

Advantages of melting

Induction heating is direct, non-contact and its principle makes it possible to use the generated heat with maximum efficiency. The coefficient of performance (COP) when using this method tends to 90%. During the melting process, there is a thermal and electrodynamic movement of the liquid metal, which contributes to a uniform temperature throughout the volume of a homogeneous material.

The technological potential of such devices creates benefits:

• performance - immediately after switching on, you can use;
• high speed of the melting process;
• the ability to adjust the temperature of the melt;
• zone and focused orientation of energy;
• homogeneity of the molten metal;
• lack of waste from alloying elements;
• environmental cleanliness and safety.

Heating Benefits

Scheme

A craftsman who can read electrical circuits is quite capable of making a heating furnace or an induction melting furnace with his own hands. The feasibility of installing a home-made unit, each master must determine for himself. It is also necessary to be well aware of the potential danger from illiterately executed such structures.

To create a workable furnace without finished scheme must have understanding of the basics of physics induction heating. Without certain knowledge, it is not possible to design and mount such an electrical appliance. Device design consists of development, design, diagramming.

For those reasonable owners who need a safe induction furnace, the scheme is especially important, as it combines all the achievements of a home craftsman. Such popular devices as induction furnaces have a variety of assembly schemes, where craftsmen have a choice:

• furnace capacity;
• operating frequency;
• lining method.

Specifications

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

• generator power;
• pulse frequency;
• eddy current losses;
• hysteresis losses;
• heat transfer rate (cooling).

Principle of operation

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

Closed inside the bodies (eddy currents) emit thermal energy, which heats the metal from the inside. Multi-stage energy conversion does not reduce the efficiency of the furnace. Due to the simple principle of operation and the possibility self assembly according to the schemes, the profitability of using such devices increases.

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

Design

The induction device is a kind of transformer in which the AC power 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.

The main nodes of the device, working on the principle of induction, consider:

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

Heating system

When installing homemade induction heaters in the heating system, craftsmen often use inexpensive models welding inverters (DC-to-AC converters). The energy consumption of the inverter is large, therefore, for the continuous operation of such systems a cable with a cross section of 4–6 mm2 is required instead of the usual 2.5 mm2.

Such heating systems must be closed and controlled automatically. Also, for safe operation, a pump is needed for forced circulation coolant, devices for removing air that has entered the system, a pressure gauge. The heater must be at a distance of at least 1 m from the ceiling and floor, and at least 30 cm from walls and furniture.

Generator

Plant powered industrial frequency at 50 Hz, inductors are obtained in the factory. And from generators and converters of high, medium and low frequencies (individual power supplies), inductors work in everyday life. The most effective involvement in the assembly of high-frequency generators. In induction mini-furnaces can be used currents of different frequencies.

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

• 4 tetrodes (electronic tubes) of high power (brand 6p3s), with parallel connection;
• 1 neon additional - indicator of readiness of the device for work.

Inductor

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

Before high temperatures Okay heated graphite brushes(melting furnaces) and nichrome spiral (heater). The easiest way is to make an inductor in the form of a spiral, the inner diameter of which is 80–150 mm. The material for the heating snake 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 do it yourself:

• channel - the melted metal is located in the chute around the inductor core;
• crucible - the metal is in a removable crucible inside the inductor.

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

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

The channel type of induction furnaces is used for smelting:

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

ducted

A channel-type induction furnace must have, during its heating, conductive body in the heat dissipation zone. During the initial start-up of such a furnace, molten metal is poured into the melting zone or a prepared metal template is inserted. Upon completion of the melting of the metal, the raw materials are not completely drained, leaving a "swamp" for the next melting.

Crucible

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

Cooling

Increases the efficiency of the smelter in industrial environments and in domestic small prefabricated appliances cooling. In case of short work and low power homemade device you can do without this function.

Complete the cooling task by yourself home master does not seem possible. Dross on copper can lead to loss of operability of the device, therefore, regular replacement of the inductor will be required.

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

Safety

When working with the oven, beware of thermal burns and take into account the high fire hazard device. When the devices are in operation, they must not be moved. Particular care must be taken when installing heating stoves in residential premises.

EMF affects and heats up the entire surrounding space, and this feature is closely related to the power and frequency of the radiation of the device. Powerful industrial devices can affect metal parts near them, people's tissues, objects in clothing pockets.

It is necessary to take into account the possible impact of such devices during work on people with implanted pacemakers. When buying devices with an induction principle of operation, you must carefully read the operating instructions.

buy ovens from induction system widely used in the process of melting metals. The current produced in the field of the inductor contributes to the heating of the substance, and this feature of such devices is not only the main, but also the most important. Processing leads to the fact that the substance undergoes several transformations. The first stage of transformation is the electromagnetic stage, after it the electrical stage, and then the thermal stage. The temperature emitted by the stove is applied almost without a trace, so this solution is the best among all others. Many may be interested in the stove made. Next, we will talk about the possibilities of implementing such a solution.

Types of furnaces for melting metals

This type of equipment can be divided into main categories. At the first, the heart channel acts as a base, and the metal is placed in such furnaces in an annular way around the inductor. The second category has no such element. This type is called a crucible, and the metal is placed inside the inductor itself. In this case, it is technically impossible to use a closed core.

Basic principles

The melting furnace in this case works on the basis of the phenomenon of magnetic induction. And there are several components. The inductor is the most important component of this device. It is a coil, the conductors in which are not ordinary wires, but copper tubes. This requirement is set by the design of melting furnaces. The current that passes in the inductor generates a magnetic field that affects the crucible, inside of which the metal is located. In this case, the role of the secondary transformer winding is assigned to the material, that is, a current passes through it, heating it. This is how melting is carried out, even if an induction furnace is made by hand. How to build this type of furnace and increase its efficiency? This is an important question that has an answer. The use of increased frequency currents can significantly increase the degree of equipment efficiency. For this, it is appropriate to use special power supplies.

Features of induction furnaces

This type of equipment has certain characteristic features, which are both advantages and disadvantages.

Since the distribution of the metal must be uniform, the resulting material is characterized by a good homogeneous mass. This type of furnace works by transporting energy through zones, and the function of focusing energy is also provided. Parameters such as capacity, operating frequency and lining method are available for use, as well as regulation of the temperature at which the metal melts, which greatly facilitates the workflow. The existing technological potential of the furnace creates a high melting rate, the devices are environmentally friendly, completely safe for humans and ready to work at any time.

The most noticeable drawback of such equipment is the difficulty of cleaning it. Since the heating of the slag occurs solely due to the heat released by the metal, this temperature is not enough to ensure its full use. The high temperature difference between the metal and the slag makes it impossible to make the process of waste disposal as simple as possible. As another drawback, it is customary to highlight the gap, due to which it is always necessary to reduce the thickness of the lining. Due to such actions, after a while it may turn out to be faulty.

The use of induction furnaces on an industrial scale

In industry, crucible and channel induction furnaces are most common. In the first, any metals are smelted in arbitrary quantities. Tanks for metal in such variants are able to fit up to several tons of metal. Of course, do-it-yourself induction melting furnaces in this case cannot be done. Channel furnaces are designed for smelting non-ferrous metals different types as well as cast iron.

Fans of radio engineering and radio technologies are often interested in this topic. Now it becomes clear that creating induction furnaces with your own hands is quite realistic, and a lot of people managed to do it. However, to create such equipment, it is necessary to implement the action electrical circuit, which would contain the prescribed actions of the furnace itself. Such solutions require the involvement of those capable of producing wave oscillations. A simple do-it-yourself induction furnace according to the scheme can be built using four electronic lamps in combination with one neon one, signaling that the system is ready to go.

In this case, the AC capacitor handle is not placed inside the instrument. Thanks to this, a do-it-yourself induction furnace can be created. The device diagram describes in detail the location of each individual element. You can make sure that the device is powerful enough if you use a screwdriver, which should reach a red-hot state in just a few seconds.

Peculiarities

If you are creating an induction furnace with your own hands, the principle of operation and assembly of which is studied and carried out according to the appropriate scheme, you should know that one or more of the factors listed below can affect the melting rate in this case:

Pulse frequency;

Hysteresis losses;

Generator power;

The period of heat release to the outside;

Losses associated with the occurrence of eddy currents.

If you are going to do an induction oven with your own hands, then when using lamps, you need to remember that their power should be distributed so that four pieces are enough. When using a rectifier, you get a network of approximately 220 V.

Domestic use of stoves

In everyday life, such devices are used quite rarely, although such technologies can be found in heating systems. They can be seen in the form of microwave ovens and In the environment of new technologies, this development has found wide application. For example, the use of eddy induced currents in induction cookers allows you to cook a wide variety of dishes. Since they take very little time to warm up, the burner cannot be turned on if there is nothing on it. However, special cookware is required to use such special and useful stoves.

Assembly process

Do-it-yourself induction consists of an inductor, which is a solenoid made from a water-cooled copper tube and a crucible, which can be made from ceramic materials, and sometimes from steel, graphite and others. In such a device, it is possible to smelt cast iron, steel, precious metals, aluminum, copper, magnesium. Do-it-yourself induction furnaces are made with a crucible capacity from a couple of kilograms to several tons. They can be vacuum, gas-filled, open and compressor. Furnaces are fed with currents of high, medium and low frequency.

So, if you are interested in a do-it-yourself induction furnace, the scheme involves the use of such basic components: a melting bath and an induction unit, which includes a hearth stone, an inductor and a magnetic core. The channel furnace differs from the crucible in that the electromagnetic energy is converted into heat in the heat release channel, in which there must always be an electrically conductive body. To make the initial start-up of a channel furnace, molten metal is poured into it or a template is inserted from a material that can be cracked down in the furnace. When the melt is completed, the metal is not completely drained, but a "swamp" is left, designed to fill the heat release channel for future start-ups. If you are going to do-it-yourself induction furnace, then to facilitate the replacement of the hearth stone for equipment, it is made detachable.

Furnace components

So, if you are interested in a do-it-yourself induction mini-oven, then it is important to know that its main element is a heating coil. When homemade version it is enough to use an inductor made of a bare copper tube, the diameter of which is 10 mm. For the inductor, an inner diameter of 80-150 mm is used, and the number of turns is 8-10. It is important that the turns do not touch, and the distance between them is 5-7 mm. Parts of the inductor must not come into contact with its screen, the minimum clearance must be 50 mm.

If you are going to do-it-yourself induction furnace, then you should know that water or antifreeze is used to cool the inductors on an industrial scale. In the case of low power and short operation of the created device, it is possible to do without cooling. But during operation, the inductor gets very hot, and scale on copper can not only drastically reduce the efficiency of the device, but also lead to a complete loss of its performance. It is impossible to make an inductor with cooling on your own, so it will need to be replaced regularly. Forced air cooling should not be used, as the case of a fan placed close to the coil will “attract” EMF to itself, which will lead to overheating and a decrease in the efficiency of the furnace.

Generator

When a do-it-yourself induction furnace is assembled, the scheme involves the use of such important element like an alternator. You should not try to make a stove if you do not know the basics of radio electronics at least at the level of an average radio amateur. The choice of the oscillator circuit must be such that it does not give a hard current spectrum.

Use of induction furnaces

This type of equipment has become widespread in areas such as foundries, where the metal has already been cleaned and needs to be given a specific shape. You can also get some alloys. In jewelry production, they also became widespread. The simple principle of operation and the possibility of assembling an induction furnace with your own hands make it possible to increase the profitability of its use. For this area, devices with a crucible capacity of up to 5 kilograms can be used. For small industries this would be the best option.

The induction furnace is often used in the field of metallurgy, so this concept is well known to people who are to some extent connected with the process of smelting various metals. The device allows you to convert electricity generated by a magnetic field into heat.

Such devices are sold in stores at a fairly high price, but if you have minimal skills in using a soldering iron and can read electronic circuits, then you can try to make an induction furnace with your own hands.

A homemade device is unlikely to be suitable for complex tasks, but it will cope with basic functions. You can assemble the device on the basis of a working welding inverter from transistors, or on lamps. The most productive in this case is the device on the lamps due to the high efficiency.

The principle of operation of the induction furnace

The heating of the metal placed inside the device occurs by the transition of electromagnetic pulses into heat energy. Electromagnetic impulses are produced by a coil with turns of copper wire or pipe.

Scheme of the induction furnace and heating schemes

When the device is connected, an electric current begins to pass through the coil, and around it appears electric field changing direction over time. For the first time, the performance of such an installation was described by James Maxwell.

The object to be heated must be placed inside the coil or close to it. The target object will be pierced by a flux of magnetic induction, and a vortex-type magnetic field will appear inside. Thus, inductive energy will turn into heat.

Varieties

Furnaces on an induction coil are usually divided into two types depending on the type of construction:

• Channel;
• Crucible.

In the first devices, the metal for melting is located in front of the induction coil, and in the furnaces of the second type it is placed inside it.

You can assemble the oven by following the steps below:

1. We bend the copper pipe in the form of a spiral. In total, it is necessary to make about 15 turns, the distance between which should be at least 5 mm. Inside the spiral, a crucible should be freely located, where the smelting process will take place;
2. We make a reliable case for the device, which should not conduct electric current, and must withstand high air temperatures;
3. Chokes and capacitors are assembled according to the scheme indicated above;
4. A neon lamp is connected to the circuit, which will signal that the device is ready for operation;
5. A capacitor is also soldered to adjust the capacitance.

Heating use

Induction furnaces of this type can also be used for space heating. Most often they are used together with a boiler, which additionally produces heating. cold water. In fact, designs are used extremely rarely due to the fact that, as a result of electromagnetic energy losses, the efficiency of the device is minimal.

Another drawback is based on the consumption of large amounts of electricity by the device during operation, because the device is classified as economically unprofitable.

System cooling

A self-assembled device must be equipped with a cooling system, since during operation all components will be exposed to high temperatures, the structure may overheat and break. Store-bought ovens are cooled with water or antifreeze.

When choosing a cooler for the home, preference is given to options that are most beneficial for implementation from an economic point of view.

For home ovens, you can try using a conventional blade fan. Pay attention to the fact that the device should not be too close to the oven, as the metal parts of the fan negatively affect the performance of the device, and can also open the vortex flows and reduce the performance of the entire system.

Precautions for using the device

When working with the device, you must adhere to the following rules:

• Some elements of the installation, as well as the metal that melts, are exposed to strong heat, as a result of which there is a risk of getting burned;
• When using a lamp oven, be sure to place it in closed case, otherwise there is a high probability of electric shock;
• Before working with the device, remove all metal elements and complex electronic devices from the working area of ​​the device. The device should not be used by people who have a pacemaker installed.

The induction type metal melting furnace can be used in tinning and forming metal parts.

A home-made installation is easy to adjust to work in specific conditions by changing some settings. If you follow the indicated schemes when assembling the structure, as well as follow the elementary safety rules, homemade device practically will not be inferior to store household appliances.