How to choose an induction oven. Induction furnace principle for melting various metals Furnace inductor

Induction furnaces are widely used in the metallurgical industry. Such ovens are often made independently. To do this, you need to know their principle of operation and design features... The principle of operation of such furnaces was known two centuries ago.

Induction ovens are capable of solving the following tasks:

Metal melting.
Heat treatment of metal parts.
Precious metal cleaning.

These functions are found in industrial ovens. For living conditions and heating the premises, there are ovens of a special design.

Operating principle

Work induction furnace consists in heating materials by using the properties of eddy currents. To create such currents, a special inductor is used, which consists of an inductor with several turns of wire of a large cross-section.

An AC power supply is connected to the inductor. In the inductor, the alternating current creates a magnetic field that changes with the mains frequency and penetrates the inner space of the inductor. When any material is placed in this space, eddy currents arise in it, which heat it up.

The water in a working inductor heats up and boils, and the metal begins to melt when the appropriate temperature is reached. Induction furnaces can be conditionally divided into types:

Furnaces with a magnetic core.
Without magnetic circuit.

The first type of furnace contains an inductor enclosed in metal, which creates a special effect that increases the density magnetic field, therefore, heating is carried out efficiently and quickly. In furnaces without a magnetic core, the inductor is located outside.

Types and features of ovens

Induction ovens can be divided into types, which have their own characteristics of work and distinctive features. Some are used for work in industry, others are used in everyday life, for cooking.

Vacuum induction furnaces

Such a furnace is designed for melting and casting alloys by the induction method. It consists of a sealed chamber in which a crucible induction furnace with a casting mold is located.

In a vacuum, perfect metallurgical processes can be ensured, and high-quality castings can be obtained. Currently, vacuum production has switched to new technological processes from continuous chains in a vacuum environment, which makes it possible to create new products and reduce production costs.

Advantages of vacuum melting

Liquid metal can be kept in vacuum for a long time.
Increased degassing of metals.
During the smelting process, it is possible to recharge the furnace and influence the refining and deoxidation process at any time.
The ability to continuously monitor and adjust the temperature of the alloy and its chemical composition during work.
High purity of castings.
Fast heating and melting speed.
Increased homogeneity of the alloy due to good mixing.
Any form of raw material.
Environmental friendliness and efficiency.

The principle of operation of a vacuum furnace is that a solid charge is melted in a crucible in a vacuum using a high-frequency inductor and the liquid metal is purified. The vacuum is created by pumping out air with pumps. In vacuum melting, a large reduction in hydrogen and nitrogen is achieved.

Channel induction furnaces

Furnaces with an electromagnetic core (duct) are widely used in foundry for non-ferrous and ferrous metals as holding furnaces, mixers.

1 - Bath
2 - Channel
3 - Magnetic circuit
4 - Primary coil

The alternating magnetic flux passes through the magnetic circuit, the channel contour in the form of a ring of liquid metal. An electric current is excited in the ring, which heats up the liquid metal. The magnetic flux is generated by the primary winding powered by alternating current.

To enhance the magnetic flux, a closed magnetic circuit is used, which is made of transformer steel. The space of the furnace is connected by two holes with a channel, therefore, when the furnace is filled with liquid metal, a closed loop is created. The oven will not be able to work without a closed loop. In such cases, the resistance of the circuit is large, and a small current flows in it, which is called the no-load current.

Due to the overheating of the metal and the action of the magnetic field, which tends to push the metal out of the channel, the liquid metal in the channel is constantly moving. Since the metal in the channel is heated higher than in the furnace bath, the metal constantly rises into the bath, from which metal with a lower temperature comes out.

If the metal is drained below the permissible rate, then the liquid metal will be ejected from the channel by electrodynamic force. As a result, the stove will turn off spontaneously and the electrical circuit will break. To avoid such cases, furnaces leave some of the metal in liquid form. It is called a swamp.

Channel furnaces are divided into:

Melting furnaces.
Mixers.
Distribution ovens.

Mixers are used to accumulate a certain amount of liquid metal, averaging its chemical composition and aging. The volume of the mixer is calculated to be at least twice the hourly output of the furnace.

Channel furnaces are divided into classes according to the location of the channels:

Vertical.
Horizontal.

By the shape of the working chamber:

Drum induction furnaces.
Cylindrical induction furnaces.

The rotary kiln is made in the form of a steel welded cylinder with two walls at the ends. Drive rollers are used to rotate the furnace. To rotate the oven, you need to turn on the drive of the electric motor with two speeds and a chain drive. The engine has disc brakes.

The end walls have a siphon for pouring metal. There are holes for loading additives and removing slags. There is also a channel for dispensing metal. The channel block consists of a furnace inductor with V-shaped channels made in the lining using templates. At the first melt, these templates melt. The winding and core are air cooled, the block body is water cooled.

If the channel furnace has a different shape, then the metal is dispensed by tilting the bath with hydraulic cylinders. Sometimes the metal is squeezed out by excess gas pressure.

Advantages of channel furnaces

Low energy consumption due to low heat loss in the bath.
Increased electrical efficiency of the inductor.
Low cost.

Disadvantages of channel furnaces

The complexity of adjusting the chemical composition of the metal, since the presence of the left liquid metal in the furnace creates difficulties in the transition from one composition to another.
The low speed of metal movement in the furnace reduces the possibilities of the melting technology.

Design features

The furnace frame is made of low carbon sheet steel with a thickness of 30 to 70 mm. At the bottom of the frame there are windows with connected inductors. The inductor is made in the form of a steel body, a primary coil, a magnetic circuit and a lining. Its body is made split, and the parts are insulated with gaskets so that parts of the body do not create a closed loop. Otherwise, an eddy current will be generated.

The magnetic circuit is made of 0.5 mm special electrical steel plates. The plates are insulated with each other to reduce eddy current losses.

The coil is made from a copper conductor with a cross-section depending on the load current and the cooling method. Air cooled permissible current 4 amperes per mm 2, when cooled with water, the allowable current is 20 amperes per mm 2. A screen is mounted between the lining and the coil, which is cooled by water. The screen is made of magnetic steel or copper. To remove heat from the coil, a fan is mounted. A template is used to get the exact dimensions of the channel. It is made in the form of a hollow steel casting. The template is placed in the inductor until it is filled with a refractory mass. It is located in the inductor during the heating and drying of the lining.

For lining, wet and dry refractory masses are used. Wet masses are used in the form of ramming or filling materials. Poured concrete is used with a complex shape of the inductor, if it is impossible to compact the mass over the entire volume of the inductor.

The inductor is filled with such a mass and compacted with vibrators. Dry masses are compacted with high-frequency vibrators, rammed masses are compacted with pneumatic rammers. If cast iron is smelted in the furnace, then the lining is made of magnesium oxide. The quality of the lining is determined by the temperature of the cooling water. Most effective method lining check is a check on the value of inductive and active resistance. These measurements are carried out using control devices.

The electrical equipment of the furnace includes:

Transformer.
A bank of capacitors to compensate for electrical energy losses.
Choke for connecting a 1-phase inductor to a 3-phase network.
Control panels.
Power cables.

In order for the oven to function normally, it is connected to the power supply for 10 kilovolts, which has 10 voltage steps on the secondary winding to adjust the power of the oven.

Lining stuffing materials contain:

48% dry quartz.
1.8% boric acid, sifted through a fine sieve with cells of 0.5 mm.

The mass for the lining is prepared dry using a mixer and subsequent sieving through a sieve. The prepared mixture should not be stored for more than 15 hours after preparation.

The crucible is lined with vibrators. Electric vibrators are used for lining large furnaces. The vibrators are immersed in the space of the template and compact the mass through the walls. When compacting, the vibrator is moved by a crane and rotated vertically.

Crucible induction furnaces

The main components of the crucible furnace are the inductor and the generator. For the manufacture of the inductor, a copper tube is used in the form of wound 8-10 turns. The forms of inductors can be made of various types.

This type of oven is the most common. There is no core in the furnace design. A common form of a furnace is a fire-resistant cylinder. The crucible is located in the inductor cavity. It is supplied with AC power.

Advantages of crucible furnaces

Energy is released when material is fed into the furnace, so no auxiliary heating elements are needed.
High homogeneity of multicomponent alloys is achieved.
In the furnace, you can create a reduction, oxidation reaction, regardless of the pressure.
High productivity of the furnaces due to the increased power density at all frequencies.
Interruptions in the melting of the metal do not affect the efficiency of the work, since it does not require a lot of electricity to heat up.
Possibility of any settings and simple operation with the possibility of automation.
There are no local overheating, the temperature is equalized throughout the entire volume of the bath.
Fast melting to create quality alloys with good uniformity.
Environmental Safety. The external environment is not exposed to any harmful effects ovens. Melting also does not harm nature.

Disadvantages of crucible furnaces

Low temperature of slags used for processing the mirror of the melt.
Low lining durability at sharp temperature changes.

Despite the existing disadvantages, crucible induction furnaces have become very popular in production and in other areas.

Induction ovens for space heating

Most often, such an oven is installed in the kitchen. In its design, the main part is a welding inverter. The design of the stove is usually combined with a water heating boiler, which makes it possible to heat all rooms in the building. It is also possible to connect the feed hot water into the building.

The efficiency of such a device is small, however, often such equipment is still used to heat a house.

The design of the heating part of an induction boiler is similar to a transformer. The outer loop is a kind of transformer windings that are connected to the network. The second internal circuit is a heat exchange device. The coolant circulates in it. When the power is connected, the coil creates a variable. As a result, currents are induced inside the heat exchanger, which heat it up. The metal heats the heating medium, which usually consists of water.

The work of household induction cookers is based on the same principle, in which dishes made of special material act as a secondary circuit. Such a stove is much more economical. conventional slabs due to the absence of heat losses.

The boiler water heater is equipped with control devices that make it possible to maintain the coolant temperature at a certain level.

Heating with electricity is an expensive pleasure. It cannot compete with solid fuel and gas diesel fuel and liquefied gas. One of the methods to reduce costs is the installation of a heat accumulator, as well as connecting the boiler at night, since at night there is usually a preferential charge for electricity.

In order to decide on the installation of an induction boiler for your home, you need to consult a professional heating engineer. An induction boiler has practically no advantages over a conventional boiler. The disadvantage is the high cost of the equipment. A conventional boiler with heating elements is sold ready for installation, and an induction heater requires additional equipment and settings. Therefore, before purchasing such an induction boiler, it is necessary to make a careful economic calculation and planning.

Lining of induction furnaces

The lining process is necessary to ensure that the furnace body is protected from the effects of elevated temperatures. It makes it possible to significantly reduce heat loss, increase the efficiency of metal melting or material heating.

For lining, quartzite is used, which is a modification of silica. Some requirements are imposed on lining materials.

Such material should provide 3 zones of material states:

Monolithic.
Buffer.
Intermediate.

Only the presence of three layers in the coating is able to protect the oven casing. The lining is adversely affected by improper material placement, poor material quality and harsh furnace conditions.

Heating and melting of metals in induction furnaces occurs due to internal heating and changes in the crystalline ...

How to assemble an induction furnace for melting metal at home with your own hands

Smelting of metal by induction is widely used in various industries: metallurgy, mechanical engineering, jewelry. A simple induction-type furnace for melting metal at home can be assembled by hand.

Operating principle

Heating and melting of metals in induction furnaces occurs due to internal heating and changes in the crystal lattice of the metal when high-frequency eddy currents pass through them. This process is based on the phenomenon of resonance, in which eddy currents have a maximum value.

To cause the flow of eddy currents through the molten metal, it is placed in the zone of action of the electromagnetic field of the inductor - the coil. It can be in the form of a spiral, figure eight or trefoil. The shape of the inductor depends on the size and shape of the workpiece to be heated.

The inductor coil is connected to an AC power source. In industrial smelting furnaces, currents of industrial frequency of 50 Hz are used; for melting small volumes of metals in jewelry, high-frequency generators are used, as they are more efficient.

Views

Eddy currents are closed in a circuit limited by the magnetic field of the inductor. Therefore, the heating of current-carrying elements is possible both inside the coil and from the outside.

channel, in which the capacity for melting metals are channels located around the inductor, and a core is located inside it;
crucible, they use a special container - a crucible made of heat-resistant material, usually removable.

Channel oven too large and designed for industrial volumes of metal melting. It is used in the smelting of cast iron, aluminum and other non-ferrous metals.

Crucible furnace quite compact, it is used by jewelers, radio amateurs, such a stove can be assembled with your own hands and used at home.

Device

high frequency alternating current generator;
inductor - a spiral winding made of copper wire or tube, made by hand;
crucible.

The crucible is placed in an inductor, the ends of the winding are connected to a current source. When current flows through the winding, an electromagnetic field with a variable vector arises around it. Eddy currents arise in a magnetic field, directed perpendicular to its vector and passing along a closed loop inside the winding. They pass through the metal placed in the crucible, while heating it to the melting point.

Advantages of an induction furnace:

fast and uniform heating of the metal immediately after turning on the unit;
direction of heating - only metal is heated, and not the entire installation;
high melting rate and melt homogeneity;
there is no evaporation of alloying metal components;
the installation is environmentally friendly and safe.

A welding inverter can be used as a generator of an induction furnace for melting metal. You can also assemble the generator according to the diagrams below with your own hands.

Furnace for melting metal on a welding inverter

This design is simple and safe as all inverters are equipped with internal overload protection. In this case, the entire assembly of the furnace comes down to making an inductor with your own hands.

It is usually performed in the form of a spiral from a thin-walled copper tube with a diameter of 8-10 mm. It is folded according to a template required diameter, placing the turns at a distance of 5-8 mm. The number of turns is from 7 to 12, depending on the diameter and characteristics of the inverter. The total resistance of the inductor must be such that it does not cause overcurrent in the inverter, otherwise it will be tripped by the internal protection.

The inductor can be fixed in a graphite or PCB housing and installed inside the crucible. You can simply place the inductor on a heat-resistant surface. The case must not conduct current, otherwise the eddy current circuit will pass through it, and the power of the installation will decrease. For the same reason, it is not recommended to place foreign objects in the melting zone.

When operating from a welding inverter, its housing must be grounded! The outlet and wiring must be rated for the current draw of the inverter.

The heating system of a private house is based on the operation of a furnace or boiler, high performance and a long uninterrupted service life of which depends both on the brand and installation of the heating devices themselves, and on correct installation chimney.

Transistor induction furnace: circuit

There are many different ways assemble an induction heater with your own hands. A fairly simple and proven scheme of a metal melting furnace is shown in the figure:

two field-effect transistors of the IRFZ44V type;
two UF4007 diodes (UF4001 can also be used);
resistor 470 Ohm, 1 W (you can take two 0.5 W connected in series);
film capacitors for 250 V: 3 pieces with a capacity of 1 μF; 4 pieces - 220 nF; 1 piece - 470 nF; 1 piece - 330 nF;
copper winding wire in enamel insulation Ø1.2 mm;
copper winding wire in enamel insulation Ø2 mm;
two rings from the chokes removed from the computer power supply.

DIY assembly sequence:

Field-effect transistors are installed on radiators. Since the circuit gets very hot during operation, the radiator must be large enough. You can install them on one radiator, but then you need to isolate the transistors from the metal using gaskets and washers made of rubber and plastic. The pinout of the field-effect transistors is shown in the figure.

It is necessary to make two chokes. For their manufacture, copper wire with a diameter of 1.2 mm is wound on rings removed from the power supply unit of any computer. These rings are composed of powdered ferromagnetic iron. It is necessary to wind from 7 to 15 turns of wire on them, trying to maintain the distance between the turns.

Collect the above capacitors into a battery with a total capacity of 4.7 μF. The capacitors are connected in parallel.

The winding of the inductor is made of copper wire with a diameter of 2 mm. 7-8 winding turns are wound on a cylindrical object suitable for the diameter of the crucible, leaving sufficiently long ends for connection to the circuit.
Connect the elements on the board in accordance with the diagram. A 12 V, 7.2 A / h battery is used as a power source. The current consumption in the operating mode is about 10 A, the battery capacity in this case will be enough for about 40 minutes. If necessary, the furnace body is made of heat-resistant material, for example, PCB. The power of the device can be changed by changing the number of turns of the inductor winding and their diameter.

During continuous operation, the heater elements may overheat! A fan can be used to cool them.

Induction heater for melting metal: video

Lamp induction oven

A more powerful induction furnace for melting metals can be assembled with your own hands on electronic tubes. The diagram of the device is shown in the figure.

To generate high-frequency current, 4 beam lamps connected in parallel are used. A copper tube with a diameter of 10 mm is used as an inductor. The unit is equipped with a trimmer capacitor for power regulation. The issued frequency is 27.12 MHz.

To assemble the circuit you need:

4 electronic tubes - tetrodes, you can use 6L6, 6P3 or G807;
4 chokes for 100 ... 1000 μH;
4 capacitors at 0.01 μF;
neon indicator lamp;
trimmer capacitor.

DIY assembly of the device:

An inductor is made of a copper tube, bending it in the form of a spiral. The diameter of the loops is 8-15 cm, the distance between the loops is at least 5 mm. The ends are tinned for soldering to the circuit. The diameter of the inductor must be larger diameter placed inside the crucible by 10 mm.
Place the inductor in the housing. It can be made of a heat-resistant, non-conductive material, or of metal, providing thermal and electrical insulation from the circuit elements.
Cascades of lamps are assembled according to the scheme with capacitors and chokes. The cascades are connected in parallel.
A neon indicator lamp is connected - it will signal that the circuit is ready for operation. The lamp is brought out to the body of the installation.
The circuit includes a variable capacitor trimmer, its handle is also brought out to the case.

For all lovers of cold-smoked delicacies, we suggest learning here how to quickly and easily make a smokehouse with your own hands, and here you can get acquainted with the photo and video instructions for making a smoke generator for cold smoking.

Cooling circuit

Industrial melting plants are equipped with a forced cooling system based on water or antifreeze. Performing water cooling at home will require additional costs, comparable in price to the cost of the metal smelter itself.

Air cooling with a fan is possible if the fan is located sufficiently far away. Otherwise, the metal winding and other elements of the fan will serve as an additional circuit for closing eddy currents, which will reduce the efficiency of the unit.

Elements of electronic and lamp circuits are also capable of actively heating up. To cool them, heat sinks are provided.

Safety measures at work

The main danger when working with a home-made installation is the risk of burns from heated elements of the installation and molten metal.
The lamp circuit includes high voltage elements, therefore it must be placed in a closed case, excluding accidental touching the elements.
The electromagnetic field is capable of affecting objects outside the device case. Therefore, before work, it is better to put on clothes without metal elements, remove complex devices from the coverage area: phones, digital cameras.

The home melting furnace can also be used to quickly heat metal elements, for example, when tinning or molding them. The characteristics of the presented installations can be tailored to a specific task by changing the parameters of the inductor and the output signal of the generating sets - this way you can achieve their maximum efficiency.

Induction furnaces are used for smelting metals and differ in that they are heated by means of an electric current. Excitation of the current occurs in the inductor, or rather in the non-alternating field.

In such constructions, energy is converted several times (in this sequence):

into electromagnetic;
electric;
heat.

Such ovens allow using heat with maximum efficiency, which is not surprising, because they are the most advanced of all existing models that run on electricity.

Note! Induction structures are of two types - with or without a core. In the first case, the metal is placed in a tubular groove, which is located around the inductor. The core is located in the inductor itself. The second option is called crucible, since in it the metal with the crucible is already inside the indicator. Of course, there can be no question of any core in this case.

Today's article will discuss howDIY induction furnace.

Pros and cons of induction designs

Among the many advantages, the following are worth highlighting:

ecological cleanliness and safety;
increased homogeneity of the melt due to the active movement of the metal;
fast response - the oven can be used almost immediately after switching on;
zone and focused direction of energy;
high melting rate;
no waste from alloying substances;
the ability to adjust the temperature;
numerous technical possibilities.

But there are also disadvantages.

The slag is heated by the metal, as a result of which it has a low temperature.
If the slag is cold, then it is very difficult to remove phosphorus and sulfur from the metal.
The magnetic field is dissipated between the coil and the molten metal, so a reduction in the thickness of the lining will be required. This will soon lead to the fact that the lining itself will fail.

Video - Induction oven

Industrial application

Both designs are used in the smelting of iron, aluminum, steel, magnesium, copper and precious metals. The useful volume of such structures can be as small as several kilograms or several hundred tons.

Industrial furnaces are divided into several types.

Medium frequency designs are commonly used in mechanical engineering and metallurgy. With their help, steel is melted, and when using graphite crucibles and non-ferrous metals.
Power frequency structures are used in iron smelting.
Resistance structures are intended for melting aluminum, aluminum alloys, zinc.

Note! It was the induction technology that formed the basis of the more popular devices - microwave ovens.

Domestic use

For obvious reasons, induction smelting furnaces are rarely used in the home. But the technology described in the article is found in almost all modern houses and apartments. These are the microwave ovens mentioned above, and induction cookers, and electric ovens.

Consider, for example, slabs. They heat the cookware by means of induction eddy currents, as a result of which heating occurs almost instantly. It is characteristic that it is impossible to turn on a hotplate without dishes on it.

The efficiency of induction cookers reaches 90%. For comparison: for electric stoves, it is about 55-65%, and for gas - no more than 30-50%. But in fairness, it should be noted that for the operation of the described stoves, special dishes are required.

Homemade induction furnace

Not so long ago, domestic radio amateurs clearly demonstrated that an induction furnace can be made by oneself. Today there are many different schemes and manufacturing technologies, we have cited only the most popular of them, which means that they are the most effective and easy to carry out.

High Frequency Generator Induction Furnace

Below is an electrical diagram for making a homemade device from a high-frequency (27.22 megahertz) generator.

In addition to the generator, assembly will require four high power light bulbs and a heavy duty light bulb for the ready-to-operate indicator.

Note! The main difference between a furnace made according to this scheme is the condenser handle - in this case, it is located outside.

In addition, the metal in the coil (inductor) will melt in the device of the smallest power.

When manufacturing, it is necessary to remember some important points that affect the speed of metal reign. This is:

power;
frequency;
eddy losses;
heat transfer intensity;
hysteresis loss.

The device will be powered from a standard 220 V mains, but with a pre-installed rectifier. If the furnace is intended for heating a room, then it is recommended to use a nichrome spiral, and if for melting, then graphite brushes. Let's get acquainted with each of the designs in more detail.

Video - Construction from a welding inverter

The essence of the design is as follows: a pair of graphite brushes is installed, and powdered granite is poured between them, after which the connection to the step-down transformer is carried out. It is characteristic that when smelting, you can not be afraid of an electric shock, since there is no need to use 220 V.

Assembly technology

Step 1. The base is assembled - a box of fireclay bricks measuring 10x10x18 cm, laid on refractory tiles.

Step 2. The box is finished with asbestos board. After wetting with water, the material softens, which allows you to give it any shape. If desired, the structure can be wrapped with steel wire.

Note! The dimensions of the box may vary depending on the power of the transformer.

Step 3. The best option for a graphite furnace is a transformer from a welding machine with a power of 0.63 kW. If the transformer is rated at 380 V, then it can be rewound, although many experienced electricians claim that you can leave it as it is

Step 4. The transformer is wrapped in thin aluminum - so the structure will not get very hot during operation.

Step 5. Graphite brushes are installed, a clay substrate is installed on the bottom of the box - so the molten metal will not spread.

The main advantage of such a furnace is heat which is even suitable for melting platinum or palladium. But among the minuses is the rapid heating of the transformer, a small volume (no more than 10 g can be melted at a time). For this reason, a different design will be required for melting large volumes.

So, for smelting large volumes of metal, a furnace with nichrome wire will be required. The principle of operation of the structure is quite simple: an electric current is supplied to a nichrome spiral, which heats up and melts the metal. There are many different formulas for calculating the length of a wire on the Web, but they are all, in principle, the same.

Step 1. For the spiral, ø0.3 mm nichrome is used with a length of about 11 m.

Step 2. The wire must be wound. To do this, you need a straight copper tube ø5 mm - the spiral is wound on it.

Step 3. A small ceramic pipe ø1.6 cm and 15 cm long is used as a crucible. One end of the pipe is plugged with an asbestos thread - so the molten metal will not flow out.

Step 4. After checking the functionality and the spiral is laid around the pipe. In this case, the same asbestos thread is placed between the turns - it will prevent short circuits and limit the access of oxygen.

Step 5. The finished coil is placed in a high power lamp socket. These cartridges are usually ceramic and sized to fit.

The advantages of this design:

high productivity (up to 30 g at one run);
fast heating (about five minutes) and long cooling;
ease of use - it is convenient to pour metal into molds;
prompt replacement of the coil in case of burnout.

But, of course, there are also disadvantages:

nichrome burns out, especially if the spiral is poorly insulated;
insecurity - the device is connected to a 220 V power supply.

Note! You cannot add metal to the stove if the previous portion has already been melted there. Otherwise, all the material will fly around the room, moreover, it can injure the eyes.

As a conclusion

As you can see, an induction furnace can still be made on your own. But to be frank, the described design (like everything available on the Internet) is not really an oven, but a Kukhtetsky laboratory inverter. It is simply impossible to assemble a full-fledged induction structure at home.

Chief Editor

How to make a DIY induction heater?

Electric heaters

Induction heaters work according to the principle of “generating current from magnetism”. In a special coil, a high-power alternating magnetic field is generated, which generates eddy currents in a closed conductor.

A closed conductor in induction cookers is metal cookware, which is heated by eddy electric currents. In general, the principle of operation of such devices is not complicated, and if you have a little knowledge in physics and electrics, it will not be difficult to assemble an induction heater with your own hands.

The following devices can be made independently:

Devices for heating the coolant in the heating boiler.
Mini ovens for melting metals.
Slabs for cooking food.

An induction cooker with your own hands must be made in compliance with all the rules and regulations for the operation of these devices. If an electromagnetic radiation hazardous to humans is emitted outside the body in lateral directions, then it is strictly prohibited to use such a device.

In addition, a great difficulty in designing a stove is the selection of material for the base of the hob, which must meet the following requirements:

Ideal to conduct electromagnetic radiation.
Not conductive.
Withstand high temperature load.

In household induction hobs, expensive ceramics are used; when making an induction hob at home, it is quite difficult to find a worthy alternative to such a material. Therefore, to begin with, you should design something simpler, for example, an induction furnace for hardening metals.

Manufacturing instruction

Figure 1. Electrical diagram induction heating body

Figure 2. Device.

Figure 3. Schematic diagram of a simple induction heater

To make a furnace, you will need the following materials and tools:

soldering iron;
solder;
textolite board.
mini drill.
radioelements.
thermal paste.
chemical reagents for etching the board.

Additional materials and their features:

For making a coil, which will emit the alternating magnetic field necessary for heating, it is necessary to prepare a piece of copper tube with a diameter of 8 mm and a length of 800 mm.
Powerful power transistors are the most expensive part of a homemade induction machine. To install the frequency generator circuit, you need to prepare 2 such elements. For these purposes, transistors of the following brands are suitable: IRFP-150; IRFP-260; IRFP-460. In the manufacture of the circuit, 2 identical of the listed field-effect transistors are used.
For the manufacture of an oscillatory circuit you will need ceramic capacitors with a capacity of 0.1 mF and an operating voltage of 1600 V. In order for a high-power alternating current to form in the coil, 7 such capacitors are required.
When operating such an induction device, field-effect transistors will get very hot and if radiators made of aluminum alloy are not connected to them, then after a few seconds of operation at maximum power, these elements will fail. Transistors should be placed on heat sinks through a thin layer of thermal paste, otherwise the efficiency of such cooling will be minimal.
Diodes that are used in an induction heater must be ultra-fast. Most suitable for this circuit, diodes: MUR-460; UF-4007; HER - 307.
Resistors used in circuit 3: 10 kOhm with a power of 0.25 W - 2 pcs. and 440 ohms with a power of 2 watts. Zener Diodes: 2 pcs. with an operating voltage of 15 V. The power of the zener diodes must be at least 2 W. The choke for connection to the power terminals of the coil is used with induction.
To power the entire device, you will need a power supply unit with a capacity of up to 500 watts. and voltage 12 - 40 V. You can power this device from a car battery, but you will not be able to get the highest power readings at this voltage.

The process of manufacturing an electronic generator and a coil itself takes a little time and is carried out in the following sequence:

Copper pipe a spiral with a diameter of 4 cm is made. To make a spiral, a copper tube should be screwed onto a rod with a flat surface with a diameter of 4 cm. The spiral should have 7 turns, which should not touch. Mounting rings are soldered to the 2 ends of the tube for connecting to the radiators of the transistor.
The printed circuit board is manufactured according to the scheme. If it is possible to supply polypropylene capacitors, then due to the fact that such elements have minimal losses and stable operation at large amplitudes of voltage fluctuations, the device will work much more stable. The capacitors in the circuit are installed in parallel, forming an oscillatory circuit with the copper coil.
Metal heating occurs inside the coil after the circuit is connected to a power supply or battery. When heating the metal, it is necessary to ensure that there is no short circuit of the spring windings. If the heated metal touches 2 turns of the coil at the same time, then the transistors fail instantly.

When conducting experiments on heating and quenching metals, inside the induction coil, the temperature can be significant and is 100 degrees Celsius. This heating effect can be used to heat domestic water or to heat a home.
Heater circuit discussed above (Figure 3), at maximum load, it is capable of providing radiation of magnetic energy inside the coil equal to 500 W. This power is not enough to heat a large volume of water, and the structure induction coil high power will require the manufacture of a circuit in which it will be necessary to use very expensive radioelements.
A budget solution for the organization of induction heating of liquid, is the use of several devices described above, arranged in series. In this case, the spirals should be in one line and not have a common metal conductor.
As a heat exchangera stainless steel pipe with a diameter of 20 mm is used. Several induction coils are "strung" onto the pipe, so that the heat exchanger is in the middle of the coil and does not come into contact with its coils. With the simultaneous switching on of 4 such devices, the heating power will be about 2 kW, which is already enough for instantaneous heating of the liquid with a small circulation of water, up to values that allow the use of this structure in the supply of warm water to a small house.
If you connect such a heating element with a well-insulated tank, which will be located above the heater, the result will be a boiler system in which the liquid will be heated inside the stainless pipe, the heated water will rise up, and a colder liquid will take its place.
If the area of the house is significant, then the number of induction coils can be increased to 10 pieces.
The power of such a boiler can be easily adjusted. by disabling or enabling spirals. The more sections that are simultaneously switched on, the more the power of the heating device operating in this way will be.
To power such a module, you will need a powerful power supply. If a DC inverter welding machine is available, then a voltage converter of the required power can be made from it.
Due to the fact that the system operates on a constant electric current, which does not exceed 40 V, the operation of such a device is relatively safe, the main thing is to provide a fuse box in the generator power circuit, which in the event of a short circuit will de-energize the system, thereby excluding the possibility of a fire.
Thus, you can organize "free" heating of the house., provided that it is installed to power induction devices rechargeable batteries, which will be charged by the energy of the sun and wind.
Batteries should be combined in sections of 2, connected in series. As a result, the supply voltage with such a connection will be at least 24 V., which will ensure the operation of the boiler at high power. In addition, a series connection will reduce the current in the circuit and increase the battery life.

Exploitation homemade devices induction heating, does not always allow to exclude the spread of electromagnetic radiation harmful to humans, therefore the induction boiler should be installed in non-residential premises and shielded with galvanized steel.
Mandatory when working with electricity the safety regulations must be followed and, especially this applies to AC networks with a voltage of 220 V.
As an experiment you can make a hob for cooking according to the scheme indicated in the article, but it is not recommended to operate this device constantly due to imperfections self-made shielding this device, because of this, the human body may be exposed to harmful electromagnetic radiation, which can adversely affect health.

An induction furnace is a furnace that is used to melt non-ferrous (bronze, aluminum, copper, gold and others) and ferrous (cast iron, steel and other) metals due to the operation of an inductor. In the field of its inductor, a current is produced, it heats the metal and brings it to a molten state.

Collapse

First, an electromagnetic field will act on it, then an electric current, and then it will go through the thermal stage. Simple construction such an oven device can be assembled independently from various improvised means.

Principle of operation

Such a furnace device is an electrical transformer with a secondary short-circuited winding. The principle of operation of an induction furnace is as follows:

with the help of a generator, an alternating current is created in the inductor;
an inductor with a capacitor creates an oscillatory circuit, it is tuned to the operating frequency;
in the case of using a self-oscillating generator, the capacitor is excluded from the device circuit, and in this case, the inductor's own capacity reserve is used;
the magnetic field created by the inductor can exist in free space or be closed using an individual ferromagnetic core;
the magnetic field acts on the metal workpiece or charge located in the inductor and forms a magnetic flux;
according to Maxwell's equations, it induces a secondary current in the workpiece;
with a solid and massive magnetic flux, the generated current is closed in the workpiece and a Foucault current or eddy current is created;
after the formation of such a current, the Joule-Lenz law comes into effect, and the energy obtained with the help of an inductor and a magnetic field heats the metal blank or charge.

Despite the multi-stage operation, the induction furnace device can provide up to 100% efficiency in vacuum or air. If a medium with magnetic permeability, then this indicator will increase, in the case of a medium made of a non-ideal dielectric, it will fall.

Device

The furnace in question is a kind of transformer, but only there is no secondary winding in it, it is replaced by a metal sample placed in the inductor. It will conduct current, but dielectrics do not heat up in this process, they remain cold.

The design of induction crucible furnaces includes an inductor, which consists of several turns of a copper tube, coiled in the form of a coil, and a cooling liquid is constantly moving inside it. Also, the inductor contains a crucible, which can be made of graphite, steel and other materials.

In addition to the inductor, a magnetic core and a hearth stone are installed in the furnace, all of which are enclosed in the furnace body. It includes:

In models of high-power ovens, the bath casing is usually made quite rigid, so there is no frame in such a device. The fixing of the casing must be able to withstand heavy loads when the entire oven is tilted. The frame is most often made from shaped beams made of steel.

The crucible induction furnace for melting metal is installed on the foundation, into which the supports are mounted, the pins of the tilt mechanism of the device rest on their bearings.

The bath casing is made of metal sheets, on which stiffeners are welded for strength.

The casing for the induction unit is used as a connecting link between the furnace transformer and the hearth stone. To reduce current losses, it is made of two halves, between which an insulating gasket is provided.

The halves are tightened by bolts, washers and bushings. Such a casing is made cast or welded; when choosing a material for it, preference is given to non-magnetic alloys. The two-chamber induction steelmaking furnace comes with a common casing for the bath and for the induction unit.

In small ovens that do not have water cooling, there is a ventilation unit, it helps to remove excess heat from the unit. Even if a water-cooled inductor is installed, it is necessary to ventilate the opening, near the hearth stone, so that it does not overheat.

In modern furnaces, there is not only a water-cooled inductor, but also water-cooled shells. Fans powered by a drive motor can be installed on the furnace frame. With a significant mass of such a device, the ventilation device is installed near the oven. If an induction furnace for steel production comes with a removable version of induction units, then each of them has its own fan.

Separately, it is worth noting the tilt mechanism, which for small furnaces comes with a manual drive, and for large ones it is equipped with a hydraulic drive located at the drain spout. Whatever the tilt mechanism is installed, it must ensure that the entire contents of the bathroom are completely drained.

Power calculation

Since the induction method of melting steel is less costly than similar methods based on the use of fuel oil, coal and other energy sources, the calculation of the induction furnace begins with calculating the power of the unit.

The power of an induction furnace is divided into active and useful, each of which has its own formula.

As initial data, you need to know:

the capacity of the furnace, in the case considered for the example, it is equal to 8 tons;
unit power (its maximum value is taken) - 1300 kW;
current frequency - 50 Hz;
furnace plant productivity - 6 tons per hour.

It is also required to take into account the metal or alloy being melted: according to the condition, it is zinc. This is important point, the heat balance of melting cast iron in an induction furnace, as well as other alloys of its own.

Net power transmitted to liquid metal:

Ppol = Wtheor × t × P,
Wtheor - specific energy consumption, it is theoretical, and shows metal overheating by 1 0 С;
P is the productivity of the furnace plant, t / h;
t is the overheating temperature of the alloy or metal billet in the furnace bath, 0 С
Ppol = 0.298 × 800 × 5.5 = 1430.4 kW.

Active power:

P = Rpol / Yuterm,
Рпол - taken from the previous formula, kW;
Yutherm - the efficiency of a casting furnace, its limits are from 0.7 to 0.85, on average they are taken as 0.76.
P = 1311.2 / 0.76 = 1892.1 kW, the value is rounded to 1900 kW.

At the final stage, the power of the inductor is calculated:

Rind = P / N,
P is the active power of the kiln installation, kW;
N is the number of inductors provided on the furnace.
Rind = 1900/2 = 950 kW.

The power consumption of an induction furnace when melting steel depends on its performance and the type of inductor.

Species and subspecies

Induction ovens are divided into two main types:

In addition to this separation, induction furnaces are compressor, vacuum, open and gas-filled.

DIY induction ovens

Among the available common methods for creating such aggregates, one can find step by step guide how to make an induction furnace from a welding inverter, with a nichrome spiral or graphite brushes, we will give their features.

High frequency generator set

It is performed taking into account the design power of the unit, eddy losses and hysteresis leaks. The structure will be powered from a regular 220 V network, but using a rectifier. This type of furnace can come with graphite brushes or nichrome spiral.

To create a furnace you will need:

two diodes UF4007;
film capacitors;
field-effect transistors in the amount of two pieces;
470 ohm resistor;
two throttle rings, they can be removed from the old computer system engineer;
copper wire cross-section Ø 2 mm.

A soldering iron and pliers are used as tools.

Here is a diagram for an induction furnace:

Induction portable melting furnaces of this type are created in the following sequence:

The transistors are located on the heat sinks. Due to the fact that in the process of melting the metal, the circuit of the device heats up quickly, the radiator for it must be selected with large parameters. It is permissible to install several transistors on one generator, but in this case they must be isolated from metal using gaskets made of plastic and rubber.
Two chokes are made. For them, two rings previously removed from the computer are taken, copper wire is wrapped around them, the number of turns is limited from 7 to 15.
Capacitors are combined with each other into a battery so that the output is a capacity of 4.7 μF, their connection is carried out in parallel.
Copper wire is twisted around the inductor, its diameter should be 2 mm. The inner diameter of the winding must match the size of the crucible used for the furnace. In total, 7-8 turns are made and long ends are left so that they can be connected to the circuit.
A 12 V battery is connected to the assembled circuit as a source; it lasts for about 40 minutes of furnace operation.

If necessary, the body is made of a material with high heat resistance. If an induction melting furnace is made from a welding inverter, then a protective case must be required, but it must be grounded.

Graphite brush design

Such a furnace is used to smelt any metal and alloys.

To create a device, you need to prepare:

graphite brushes;
powder granite;
transformer;
fireclay brick;
steel wire;
thin aluminum.

The assembly technology of the structure is as follows:

Device with nichrome spiral

Such a device is used for smelting large volumes of metal.

The following are used as consumables for arranging a homemade stove:

nichrome;
asbestos thread;
a piece of ceramic pipe.

After connecting all the components of the furnace according to the scheme, its work is as follows: after applying an electric current to the nichrome spiral, it transfers heat to the metal and melts it.

The creation of such a furnace is carried out in the following sequence:

This design is characterized by high performance, it cools down for a long time and heats up quickly. But it must be borne in mind that if the spiral is poorly insulated, it will quickly burn out.

Prices for ready-made induction furnaces

Homemade furnace designs will cost much cheaper than purchased ones, but they cannot be created in large volumes, therefore, ready-made options for mass production of the melt cannot be dispensed with.

Prices for induction furnaces for melting metal depend on their capacity and configuration.

Model	Characteristics and features	Price, rubles
INDUTHERM MU-200	The furnace supports 16 temperature programs, the maximum heating temperature is 1400 ° C, the mode is controlled with a type S thermocouple. The unit produces a power of 3.5 kW.	820 thous.
INDUTHERM MU-900	The furnace operates on a 380 V power supply, temperature control is carried out using a type S thermocouple and can reach up to 1500 ° C. Power - 15 kW.	1.7 million
UPI-60-2	This mini induction melting furnace can be used to melt non-ferrous and precious metals. The blanks are loaded into a graphite crucible and heated according to the principle of a transformer.	125 thous.
IST-1 / 0.8 M5	The furnace inductor is a basket in which a magnetic circuit is built in together with a coil. Unit 1 ton.	1.7 million
UI-25P	The furnace device is designed for a load of 20 kg, it is equipped with a reduction gear inclination of the melting unit. The oven comes with a block of capacitor banks. Installation power - 25 kW. Maximum heating t - 1600 0С.	470 thous.
UI-0.50T-400	The unit is designed for a load of 500 kg, the highest power of the installation is 525 kW, the voltage for it must be at least 380V, the maximum operating t - 1850 0С.	900 thous.
ST 10	The stove of the Italian company is equipped with a digital thermostat, SMD technology is built into the control panel, which is distinguished by its speed. The universal unit can operate with different capacities from 1 to 3 kg, for this it does not need to be readjusted. It is intended for precious metals, its maximum temperature is 1250 ° C.	1 million
ST 12	Static induction furnace with digital thermostat. It can be supplemented with a vacuum casting chamber, which makes it possible to cast directly next to the installation. The control is carried out using the touch panel. The maximum temperature is 1250 ° C.	1050 thous.
IChT-10TN	The furnace is designed for a load of 10 tons, a rather voluminous unit, for its installation it is necessary to allocate a closed workshop room.	8.9 million

Conclusion

It is exciting to make an induction furnace on your own, but this is fraught with some restrictions and unknown consequences, since you need to rely on the laws of physics and chemistry, and whoever is not strong in this will not be able to carry out the process safely. For frequent use of such an installation, it is better to choose suitable option from the above.

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Nowadays, furnaces with an induction system are widely used in the process of smelting 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 basic, 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 which the electrical stage, and then the thermal stage. The temperature that the stove emits is applied practically without residue, therefore this solution is the best among all others. Many people may be interested in the made stove. Next, we will talk about the possibilities of implementing such a solution.

Types of metal melting furnaces

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

Basic principles

The smelting furnace in this case operates on the basis of the phenomenon of magnetic induction. And there are several components here. The inductor is the most important component of this device. It is a coil, in which the conductors are not ordinary wires, but copper tubes. This requirement is set by the very design of the melting furnaces. The current that flows in the inductor generates a magnetic field that affects the crucible, inside which the metal is located. In this case, the material is assigned the role of a secondary transformer winding, 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 oven and increase its efficiency? This is an important question that has an answer. The use of currents of increased frequency 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 characteristics that 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, while also providing an energy focusing function. For use, parameters such as capacity, operating frequency and lining method are available, as well as temperature control 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 disadvantage of such equipment is the difficulty in cleaning it. Since the heating of the slag occurs exclusively due to the heat generated by the metal, this temperature is not enough to ensure its full use. The high temperature difference between the metal and the slag does not make the waste disposal process as simple as possible. As another disadvantage, it is customary to distinguish a gap, due to which it is always required to reduce the thickness of the lining. Due to such actions, after a while, it may turn out to be malfunctioning.

Industrial use of induction furnaces

In industry, crucible and channel induction furnaces are most often found. In the first, any metals are smelted in arbitrary quantities. Tanks for metal in such options can hold up to several tons of metal. Of course, in this case, it is impossible to make induction melting furnaces with your own hands. Channel furnaces are designed for smelting non-ferrous metals different types as well as cast iron.

This topic is often of interest to fans of radio engineering and radio technology. Now it is becoming clear that creating induction furnaces with your own hands is quite realistic, and very many have succeeded in doing this. However, to create such equipment, it is required to implement the operation of an electrical circuit that 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, signaling that the system is ready for use.

In this case, the handle of the AC capacitor is not located 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 create 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 the melting rate in this case may be affected by one or more of the factors listed below:

Pulse frequency;

Hysteresis losses;

Generating power;

Period of heat release outside;

Eddy current losses.

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 will get a network of about 220 V.

Domestic use of ovens

In everyday life, such devices are rarely used, 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 induction currents in induction cookers allows you to cook a huge variety of dishes. Since they take very little time to warm up, the burner cannot be turned on if nothing is on it. However, special cookware is required to use such special and useful cookers.

Build process

A do-it-yourself induction coil 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 steel, graphite and others. In such a device, you can 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 powered by 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 units: a melting bath and an induction unit, which includes a hearth stone, an inductor and a magnetic core. A channel furnace differs from a crucible furnace in that electromagnetic energy is converted into thermal energy in a 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 expand in the furnace. When the melting is completed, the metal is not completely drained away, but a "swamp" remains, designed to fill the heat release channel for future start-up. If an induction furnace is going to do it yourself, then to facilitate the replacement of the hearth stone for the equipment, it is made detachable.

Furnace components

So, if you are interested in a do-it-yourself mini induction oven, then it is important to know that its main element is the heating coil. In the case of a 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. The parts of the inductor should not come into contact with its shield, the minimum gap should be 50 mm.

If you are going to do an induction oven with your own hands, then you should know that on an industrial scale, water or antifreeze is involved in cooling the inductors. In the case of low power and short-term operation of the created device, you can do without cooling. But during operation, the inductor heats up a lot, and the 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 must not be used, since the fan housing located close to the coil will "attract" the EMF to itself, which will lead to overheating and a drop in the furnace efficiency.

Generator

When assembling an induction furnace with your own hands, the circuit assumes the use of such an important element as 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 generator circuit should be such that it does not give a hard current spectrum.

Using induction ovens

This type of equipment has become widespread in areas such as foundry, where the metal has already been cleaned and needs to be given some specific shape. You can also get some alloys. In the jewelry industry, they also became widespread. The simple principle of operation and the possibility of assembling an induction furnace with your own hands allow you 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 option will be optimal.

For smelting metal on a small scale, some kind of device is sometimes needed. This is especially acute in the workshop or in small production. The most effective at the moment is a furnace for melting metal with an electric heater, namely induction. Due to the peculiarity of its structure, it can be effectively used in blacksmithing and become an irreplaceable tool in the forge.

Induction furnace device

The oven consists of 3 elements:

1. Electronic and electrical part.
2. Inductor and crucible.
3. inductor cooling system.

In order to assemble an operating furnace for melting metal, it is enough to assemble a working electrical circuit and a cooling system for the inductor. The simplest way to melt metal is shown in the video below. Melting is carried out in the oncoming electromagnetic field of the inductor, which interacts with the induced electric-eddy currents in the metal, which keeps the piece of aluminum in the space of the inductor.

In order to effectively melt the metal, currents of large magnitude and high frequency of the order of 400-600 Hz are required. The voltage from an ordinary 220V home outlet has sufficient data to melt metals. It is only necessary to turn 50 Hz into 400-600 Hz.
For this, any scheme for creating a Tesla coil is suitable. I liked the following 2 schemes most on the GU 80, GU 81 (M) lamp. And powering the lamp with an ILO transformer from a microwave.

These circuits are designed for a Tesla coil, but the induction furnace turns out to be excellent from them, it is enough to place a piece of iron in the inner space of the primary winding L1 instead of the secondary coil L2.

The primary coil L1 or the inductor consists of a copper tube rolled into 5-6 turns, at the ends of which a thread is cut to connect the cooling system. For levitation melting, the last turn should be done in the opposite direction.
Capacitor C2 in the first circuit and identical to it in the second one sets the frequency of the generator. With a value of 1000 picoFarad, the frequency is about 400 kHz. This capacitor must necessarily be a high-frequency ceramic and rated for a high voltage of about 10 kV (KVI-2, KVI-3, K15U-1), other types are not suitable! Better to put K15U. Capacitors can be connected in parallel. It is also worth considering the power for which the capacitors are designed (this is written on the case for them), take with a margin. the other two capacitors KVI-3 and KVI-2 heat up during long-term operation. All other capacitors are also taken from the KVI-2, KVI-3, K15U-1 series, only the capacitance changes in the characteristics of the capacitors.
As a result, it is schematically what should happen. I circled 3 blocks in frames.

The cooling system is made of a pump with a flow of 60 l / min, a radiator from any VAZ car, and I put a cooling fan in front of a normal home radiator.

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