Do-it-yourself induction furnace: operating principle, design and parameters, use for heating. Induction furnaces: operating principles, drawings, how to make it yourself A simple do-it-yourself induction furnace according to the diagram

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

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

Metal smelting by induction is widely used in various industries: metallurgy, mechanical engineering, jewelry. You can assemble a simple induction furnace for melting metal at home with your own hands.

Operating principle

Heating and melting of metals in induction furnaces occurs due to internal heating and change crystal lattice 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 eddy currents to flow through the molten metal, it is placed in the area of electricity. magnetic field inductor - coil. It can be in the shape of a spiral, figure eight or trefoil. The shape of the inductor depends on the size and shape of the heated workpiece.

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

Species

Eddy currents are closed along a circuit limited by the magnetic field of the inductor. Therefore, heating of the conductive elements is possible both inside the coil and on its outside.

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

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

Device

simple design

alternator high frequency;
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 appears around it. In a magnetic field, eddy currents arise, directed perpendicular to its vector and passing along a closed loop inside the winding. They pass through the metal placed in the crucible, heating it to the melting point.

Advantages of an induction furnace:

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

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

Furnace for melting metal using a welding inverter

This design is simple and safe, since all inverters are equipped with internal overload protection. The entire assembly of the furnace in this case 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 bent 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 as not to cause overcurrent in the inverter, otherwise it will be turned off by the internal protection.

The inductor can be fixed in a housing made of graphite or textolite and a crucible can be installed inside. You can simply place the inductor on a heat-resistant surface. The housing must not conduct current, otherwise eddy currents 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 working from welding inverter its body must be grounded! The outlet and wiring must be rated for the current drawn by the inverter.

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

Induction furnace with transistors: diagram

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

two field-effect transistors type IRFZ44V;
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 inductors 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 field-effect transistors is shown in the figure.

It is necessary to make two chokes. For their manufacture copper wire 1.2 mm in diameter are wound onto rings removed from the power supply of any computer. These rings are made 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.

The capacitors listed above are assembled into a battery with a total capacity of 4.7 μF. The connection of capacitors is parallel.

The inductor winding is made of copper wire with a diameter of 2 mm. Wrap 7-8 turns of winding around a cylindrical object suitable for the diameter of the crucible, leaving the ends long enough to connect 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 operating mode is about 10 A, the battery capacity in this case will last for about 40 minutes. If necessary, the furnace body is made of a heat-resistant material, for example, textolite. The power of the device can be changed by changing the number of turns of the inductor winding and their diameter.

During prolonged operation, the heater elements may overheat! You can use a fan to cool them.

Induction heater for metal melting: video

Induction furnace with lamps

A more powerful induction furnace for melting metals can be assembled with your own hands using electronic tubes. The device diagram 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 installation is equipped with a tuning capacitor to regulate power. The issued frequency is 27.12 MHz.

To assemble the circuit you need:

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

Assembling the device yourself:

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

For all lovers of delicacies prepared using the cold smoking method, we suggest you learn here how to quickly and easily make a smokehouse with your own hands, and here you can get acquainted with photos and video instructions for making a smoke generator for cold smoking.

Circuit cooling

Industrial smelting plants are equipped with a forced cooling system using water or antifreeze. Carrying out water cooling at home will require additional costs comparable in price to the cost of the metal melting installation itself.

Air cooling using a fan is possible if the fan is located far enough 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 installation.

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

Safety precautions when working

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

A furnace for melting metals at home can also be used to quickly heat metal elements, for example, when tinning or forming them. The operating characteristics of the presented installations can be adjusted 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 They are used for smelting metals and are distinguished by the fact that they are heated by electric current. The current is excited in the inductor, or more precisely in a constant field.

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

into electromagnetic;
electrical;
thermal

Such stoves allow you to use heat with maximum efficiency, which is not surprising, because they are the most perfect of all existing models powered by electricity.

Pay attention! Induction designs come in two types - with or without a core. In the first case, the metal is placed in a tubular trough, which is located around the inductor. The core is located in the inductor itself. The second option is called crucible, because in it the metal and the crucible are already inside the indicator. Of course, not about any core in in this case there is no question.

In today's article we will talk about how to makeDIY induction oven.

Pros and cons of induction designs

Among the many advantages, the following are worth highlighting:

environmental cleanliness and safety;
increased homogeneity of the melt due to active movement of metal;
speed – the oven can be used almost immediately after switching on;
zonal and focused energy orientation;
high melting rate;
no fumes from alloying substances;
possibility of temperature adjustment;
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 melting metal, so a reduction in the thickness of the lining will be required. This will soon lead to the lining itself failing.

Video – Induction oven

Industrial Application

Both design options are used in the smelting of cast iron, aluminum, steel, magnesium, copper and precious metals. The useful volume of such structures can range from several kilograms to several hundred tons.

Furnaces industrial purposes 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, non-ferrous metals are melted.
Industrial frequency designs are used in iron smelting.
Resistance structures are intended for melting aluminum, aluminum alloys, zinc.

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

Household use

Due to obvious reasons, an induction furnace for melting is not often used in everyday life. But the technology described in the article is found in almost all modern houses and apartments. These include the above-mentioned microwave ovens, induction cookers, and electric ovens.

Consider, for example, slabs. They heat the dishes due to induction eddy currents, as a result of which heating occurs almost instantly. It is typical that it is impossible to turn on a burner that has no cookware on it.

Efficiency induction cookers reaches 90%. For comparison: for electric stoves it is approximately 55-65%, and for gas stoves it is no more than 30-50%. But in fairness, it is worth noting that special utensils are required to operate the described stoves.

Homemade induction furnace

Not long ago, domestic radio amateurs clearly demonstrated that you can make an induction furnace yourself. Today there are a lot various schemes and manufacturing technologies, we have listed only the most popular of them, which means the most effective and easy to implement.

Induction furnace made from high frequency generator

Below is 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 lamp for the readiness indicator.

Pay attention! The main difference between a stove made according to this scheme is the condenser handle - in this case it is located outside.

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

When making it is necessary to remember some important points, affecting the speed of metal control. This:

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

The device will be powered from a standard 220 V network, 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 take a closer look at each of the designs.

Video - Construction of a welding inverter

The essence of the design is as follows: a pair of graphite brushes is installed, and granite powder is poured between them, after which the connection is made to the step-down transformer. It is typical that during smelting there is no need to worry about electric shock, since there is no need to use 220 V.

Assembly technology

Step 1. The base is assembled - a fireclay brick box measuring 10x10x18 cm, laid on fire-resistant tiles.

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

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

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

Step 4. The transformer is wrapped with thin aluminum - this way the structure will not get too hot during operation.

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

The main advantage of such a furnace is high temperature, which is even suitable for smelting platinum or palladium. But among the disadvantages are the rapid heating of the transformer, small volume (no more than 10 g can be smelted at a time). For this reason, a different design will be required for larger volume melts.

So, to smelt large volumes of metal you will need a furnace with nichrome wire. The operating principle of the design is quite simple: electric current fed to a nichrome spiral, which heats up and melts the metal. There are a lot of different formulas on the Internet for calculating the length of a wire, but they are all, in principle, the same.

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

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

Step 3. Use a small crucible as a crucible. ceramic pipeø1.6 cm and 15 cm long. One end of the pipe is plugged with asbestos thread - this way the molten metal will not leak out.

Step 4. After checking the functionality, 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. Such cartridges are usually ceramic and have the required size.

Advantages of this design:

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

But there are, of course, disadvantages:

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

Pay attention! You cannot add metal to the stove if the previous portion has already been melted there. Otherwise, all the material will scatter throughout the room, moreover, it can injure your eyes.

As a conclusion

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

editor-in-chief

How to make an induction heater with your own hands?

Electric heaters

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

The closed conductor in induction cookers is a metal pan, which is heated by eddy electric currents. In general, the operating principle of such devices is not complicated, and if you have a little knowledge of physics and electrical engineering, assembling an induction heater with your own hands will not be difficult.

The following devices can be made independently:

Devices for heating the coolant in a heating boiler.
Mini ovens for melting metals.
Plates for cooking.

A do-it-yourself induction cooker must be made in compliance with all the rules and regulations for the operation of these devices. If electromagnetic radiation dangerous to humans is emitted outside the housing in lateral directions, then the use of such a device is strictly prohibited.

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

Ideally conduct electromagnetic radiation.
Not a conductive material.
Withstand high temperature load.

In household cookers induction surfaces Expensive ceramics are used when making an induction cooker at home; finding a worthy alternative to such material is quite difficult. Therefore, first you should design something simpler, for example, an induction furnace for hardening metals.

Manufacturing instructions

Figure 1. Electrical circuit of an induction heater

Figure 2. Device.

Figure 3. Schematic of a simple induction heater

To make a stove 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 installation. To install the frequency generator circuit, you need to prepare 2 such elements. Transistors of the following brands are suitable for these purposes: IRFP-150; IRFP-260; IRFP-460. When making 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 high-power alternating current to form in the coil, 7 such capacitors will be required.
When operating such an induction device, field-effect transistors will get very hot and if aluminum alloy radiators are not attached to them, then after just a few seconds of operation at maximum power, these elements will fail. Transistors should be placed on heat sinks through thin layer thermal paste, otherwise the effectiveness of such cooling will be minimal.
Diodes, which are used in induction heater, must be ultra-fast acting. The most suitable diodes for this circuit are: MUR-460; UF-4007; HER – 307.
Resistors used in circuit 3: 10 kOhm power 0.25 W – 2 pcs. and 440 Ohm power - 2 W. Zener diodes: 2 pcs. with an operating voltage of 15 V. The power of the zener diodes must be at least 2 W. A choke for connecting to the power terminals of the coil is used with induction.
To power the entire device you will need a power supply with a power of up to 500 W. and voltage 12 - 40 V. You can power this device from a car battery, but you won’t be able to get the highest power readings at this voltage.

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

From copper pipe a spiral with a diameter of 4 cm is made. To make a spiral, screw a copper tube onto a rod with flat surface 4 cm in diameter. The spiral must have 7 turns, which should not touch. Fastening rings are soldered to the 2 ends of the tube for connection to the transistor radiators.
The printed circuit board is made according to the diagram. 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 operate much more stable. The capacitors in the circuit are installed in parallel to form an oscillating circuit with a copper coil.
Heating the metal occurs inside the coil after the circuit is connected to the power supply or battery. When heating the metal, it is necessary to ensure that there is no short circuit in the spring windings. If you touch 2 turns of the coil at the same time with heated metal, the transistors will fail instantly.

When conducting experiments on heating and hardening of metals, inside the induction coil the temperature can be significant and amounts to 100 degrees Celsius. This thermal heating effect can be used to heat water for household needs or for heating a house.
Diagram of the heater discussed above (Figure 3), at maximum load 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 construction of a high-power induction coil will require the manufacture of a circuit in which it will be necessary to use very expensive radio elements.
Budget solution for organizing induction heating of liquids, is the use of several devices described above, located in series. In this case, the spirals must be on the same 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 spirals are “strung” onto the pipe, so that the heat exchanger is in the middle of the spiral and does not come into contact with its turns. When 4 such devices are turned on simultaneously, the heating power will be about 2 kW, which is already enough for flow heating liquid with a small circulation of water, to values allowing use this design in supply warm water small house.
If you connect such a heating element to 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 a stainless pipe, the heated water will rise upward, 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 turning off or turning on the spirals. The more sections that are turned on at the same time, the greater the power of the heating device operating in this way.
To power such a module you will need a powerful power supply. If you have an inverter welding machine available DC, then a voltage converter of the required power can be made from it.
Due to the fact that the system operates on 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 block in the generator power circuit, which in the event of a short circuit will de-energize the system, thereby eliminating the possibility of a fire.
You can organize “free” home heating in this way., subject to installation for powering induction devices batteries, which will be charged using solar and wind energy.
The batteries should be combined into 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 boiler operates at high power. In addition, a series connection will reduce the current in the circuit and increase the service life of the batteries.

Operation homemade devices induction heating, does not always eliminate the spread of electromagnetic radiation harmful to humans, so the induction boiler should be installed in a non-residential area and shielded with galvanized steel.
Mandatory when working with electricity safety regulations must be followed and, especially for 220 V AC networks.
As an experiment can be made hob for cooking according to the scheme specified in the article, but it is not recommended to use this device constantly due to imperfections self-made shielding of this device, because of this, the human body may be exposed to harmful electromagnetic radiation that can adversely affect health.

Metal smelting by induction is actively used in various industries, such as mechanical engineering, metallurgical and jewelry production. The material is heated under the influence of electric current, which allows the heat to be used with maximum efficiency. Large factories have special industrial units for this, while at home you can assemble a simple and small induction furnace with your own hands.

Such furnaces are popular in production

Self-assembly of the stove

There are many technologies and schematic descriptions of this process presented on the Internet and magazines, but when choosing, it is worth choosing one model that is most effective in operation, as well as affordable and easy to implement.

Homemade melting furnaces have a fairly simple design and usually consist of only three main parts housed in a sturdy casing. These include:

element generating high frequency alternating current;
a spiral-shaped part created from a copper tube or thick wire, called an inductor;
crucible - a container in which calcination or melting will be carried out, made of refractory material.

Of course, such equipment is not often used in everyday life, because not all craftsmen need such units. But the technologies found in these devices are present in household appliances, which many people deal with almost every day. This includes microwaves, electric ovens and induction cookers. You can make various equipment using diagrams with your own hands if you have the necessary knowledge and skills.

In this video you will learn what this oven consists of

Heating in this technique is carried out thanks to induction eddy currents. The temperature rise occurs instantly, unlike other devices of a similar purpose.

For example, induction cookers have an efficiency of 90%, but gas and electric cookers cannot boast of this value; it is only 30-40% and 55-65%, respectively. However, HDTV cookers have a drawback: to use them you will have to prepare special dishes.

Transistor design

There are many different assembly schemes induction smelters at home. A simple and proven furnace made from field-effect transistors is quite easy to assemble; many craftsmen familiar with the basics of radio engineering can handle its manufacture according to the diagram shown in the figure. To create an installation You need to prepare the following materials and parts:

two IRFZ44V transistors;
copper wires (for winding) in enamel insulation, 1.2 and 2 mm thick (one piece each);
two rings from chokes, they can be removed from the power supply of an old computer;
one 470 Ohm resistor per 1 W (you can connect two 0.5 W each in series);
two UF4007 diodes (can easily be replaced with the UF4001 model);
250 W film capacitors - one piece with a capacity of 330 nF, four - 220 nF, three - 1 µF, 1 piece - 470 nF.

Before assembling such a stove, do not forget about the tools

Assembly takes place according to the schematic drawing; it is also recommended to check step by step instructions, this will protect you from errors and damage to elements. Creating an induction melting furnace with your own hands is carried out according to the following algorithm:

Transistors are placed on fairly large heatsinks. The fact is that circuits can get very hot during operation, which is why it is so important to select parts of the appropriate size. All transistors can be placed on one radiator, but in this case you will have to insulate them, preventing them from coming into contact with metal. Washers and gaskets made of plastic and rubber will help with this. The correct pinout of transistors is shown in the picture.
Then they start making chokes; you will need two of them. To do this, take copper wire 1.2 millimeters in diameter and wrap it around rings taken from the power supply. These elements contain ferromagnetic iron in powder form, so it is necessary to make at least 7-15 turns, leaving a small distance between them.
The resulting modules are assembled into one battery with a capacity of 4.6 μF, and the capacitors are connected in parallel.
Copper wire 2 mm thick is used to wind the inductor. It is wrapped 7-8 times around any object. cylindrical, its diameter must correspond to the size of the crucible. The excess wire is cut off, but rather long ends are left: they will be needed for connecting to other parts.
All elements are connected on the board, as shown in the figure.

If necessary, you can build a housing for the unit; for this purpose, only heat-resistant materials, such as textolite, are used. The power of the device can be adjusted, for which it is enough to change the number of turns of wire on the inductor and their diameter.

There are several variations of the induction furnace that can be assembled

With graphite brushes

The main element of this design is assembled from graphite brushes, the space between which is filled with granite, crushed to a powder state. Then the finished module is connected to a step-down transformer. When working with such equipment, you do not have to worry about electric shock, since it does not need to use 220 volts.

Manufacturing technology of an induction furnace from graphite brushes:

First, the body is assembled; for this, fire-resistant (fireclay) bricks measuring 10 × 10 × 18 cm are laid on tiles that can withstand high temperatures. The finished box is wrapped in asbestos cardboard. To give this material the desired shape, it is enough to moisten it with a small amount of water. The size of the base directly depends on the power of the transformer used in the design. If desired, the box can be covered with steel wire.
An excellent option for graphite furnaces would be a 0.063 kW transformer taken from a welding machine. If it is designed for 380 V, then for safety reasons it can be subjected to winding, although many experienced radio technicians believe that this procedure can be abandoned without any risk. However, it is recommended to wrap the transformer with thin aluminum so that the finished device does not heat up during operation.
A clay substrate is placed at the bottom of the box so that the liquid metal does not spread, after which graphite brushes and granite sand are placed in the box.

The main advantage of such devices is the high melting point, which can change physical state even palladium and platinum. The disadvantages include the transformer heating up too quickly, as well as the small furnace area, which will not allow smelting more than 10 g of metal at a time. Therefore, every master should understand that if the device is assembled to process large volumes, then it is better to make a furnace of a different design.

Lamp-based device

A powerful melting stove can be assembled from electronic light bulbs. As can be seen in the diagram, to obtain high-frequency current, beam lamps must be connected in parallel. Instead of an inductor, this device uses a copper tube with a diameter of 10 mm. The design is also equipped with a tuning capacitor in order to be able to regulate the power of the furnace. For assembly you need to prepare:

four lamps (tetrodes) L6, 6P3 or G807;
trimmer capacitor;
4 chokes at 100-1000 µH;
neon indicator light;
four 0.01 µF capacitors.

To begin with, the copper tube is shaped into a spiral - this will be the inductor of the device. In this case, a distance of at least 5 mm is left between the turns, and their diameter should be 8-15 cm. The ends of the spiral are processed for attachment to the circuit. The thickness of the resulting inductor should be 10 mm greater than that of the crucible (it is placed inside).

The finished part is placed in the housing. For its manufacture, you should use a material that will provide electrical and thermal insulation for the filling of the device. Then a cascade is assembled from lamps, chokes and capacitors, as shown in the figure, the latter being connected in a straight line.

It's time to connect the neon indicator: it is needed so that the master can find out when the device is ready for work. This light bulb is connected to the furnace body along with the handle of the variable capacitor.

Cooling system equipment

Industrial units for metal melting are equipped with special systems cooling with antifreeze or water. For equipment of these important installations in homemade HDTV stoves you will need additional costs, because of which the assembly can significantly hit the wallet. Therefore, it is better to provide a household unit with a cheaper system consisting of fans.

Air cooling with these devices is possible when they are located remotely from the furnace. Otherwise, the metal windings and fan parts can serve as a loop for short-circuiting eddy currents, which will significantly reduce the efficiency of the equipment.

Lamp and electronic circuits also tend to actively heat up during operation of the unit. Heat sinks are usually used to cool them.

Terms of use

For experienced radio technicians, assembling an induction furnace according to the diagrams with your own hands may seem like an easy task, so the device will be ready quite quickly, and the master will want to try his creation in action. It is worth remembering that when working with a homemade installation, it is important to follow safety precautions and not forget about the main threats that may arise during operation of an inertial furnace:

Liquid metal and heating elements devices can cause severe burns.
Lamp circuits consist of high-voltage parts, so during assembly of the unit they must be placed in a closed box, thus eliminating the possibility of accidental touching of these elements.
The electromagnetic field can influence even those things that are outside the installation box. Therefore, before turning on the device, you need to remove all complex technical devices, such as mobile phones, digital cameras, MP3 players, and remove all metal jewelry. People with pacemakers are also at risk: they should never use such equipment.

These furnaces can be used not only for melting, but also for rapid heating metal objects during forming and tinning. By changing the output signal of the installation and the parameters of the inductor, you can configure the device for a specific task.

For melting small volumes of iron, homemade stoves are used; these effective devices can operate from ordinary sockets. The device does not take up much space, it can be placed on a desktop in a workshop or garage. If a person knows how to read simple electrical diagrams, then he does not need to purchase such equipment in a store, because he can assemble a small stove with his own hands in just a few hours.

Radio amateurs have long discovered that they can make induction furnaces for melting metal with their own hands. These simple circuits will help you make a HDTV installation for home use. However, it would be more correct to call all the described designs “Kukhtetsky’s laboratory inverters,” since it is simply impossible to independently assemble a full-fledged stove of this type.

The induction furnace can be used to melt a small amount of metal, separate and purify precious metals, to heat metal products for the purpose of hardening or tempering.

In addition, such stoves are proposed to be used for heating the home. Induction furnaces are commercially available, but it is more interesting and cheaper to make such a furnace yourself.

The operating principle of an induction furnace is based on heating the material using eddy currents.

To obtain such currents, a so-called inductor is used, which is an inductor coil containing only a few turns of thick wire.

The inductor is powered by a 50 Hz alternating current network (sometimes through a step-down transformer) or from a high-frequency generator.

The alternating current flowing through the inductor generates an alternating magnetic field that permeates space. If there is any material in this space, then currents will be induced in it, which will begin to heat this material. If this material is water, then its temperature will increase, and if it is metal, then after a while it will begin to melt.

There are two types of induction furnaces:

furnaces with magnetic core;
ovens without a magnetic core.

The fundamental difference between these two types of furnaces is that in the first case the inductor is located inside the melting metal, and in the second - outside. The presence of a magnetic circuit increases the density of the magnetic field penetrating the metal placed in the crucible, which facilitates its heating.

An example of an induction furnace with a magnetic core is a channel induction furnace. The circuit of such a furnace includes a closed magnetic circuit made of transformer steel, on which the primary winding is located - an inductor and a ring-shaped crucible in which the material for melting is located. The crucible is made of heat-resistant dielectric. Such an installation is powered from an alternating current network with a frequency of 50 Hz or a generator with an increased frequency of 400 Hz.

Such furnaces are used for melting duralumin, non-ferrous metals or producing high-quality cast iron.

Crucible furnaces that do not have a magnetic core are more common. The absence of a magnetic circuit in the furnace leads to the fact that the magnetic field created by industrial frequency currents is strongly dissipated in the surrounding space. And in order to increase the magnetic field density in a dielectric crucible with material to be melted, it is necessary to use higher frequencies. It is believed that if the inductor circuit is tuned to resonance with the frequency of the supply voltage, and the diameter of the crucible is commensurate with the resonance wavelength, then up to 75% of the energy of the electromagnetic field can be concentrated in the crucible area.

Induction furnace manufacturing diagram

As studies have shown, to ensure efficient melting of metals in a crucible furnace, it is desirable that the frequency of the voltage supplying the inductor exceeds the resonant frequency by 2-3 times. That is, such a furnace operates at the second or third frequency harmonic. In addition, when operating at such higher frequencies, the alloy is better mixed, which improves its quality. A mode using even higher frequencies (fifth or sixth harmonics) can be used for surface carburization or hardening of metal, which is associated with the appearance of a skin effect, that is, the displacement of a high-frequency electromagnetic field to the surface of the workpiece.

Conclusions on the section:

There are two options for an induction furnace - with a magnetic core and without a magnetic core.
The channel furnace, which belongs to the first version of the furnaces, is more complex in design, but can be powered directly from a 50 Hz network or a high-frequency network of 400 Hz.
The crucible furnace, which belongs to the furnaces of the second type, is simpler in design, but requires a high-frequency generator to power the inductor.

If the oven is heating device For practical needs, a fireplace is needed for decoration and comfort. , as well as an example of ordering a fireplace with an arch.

Read about how to choose the right electric heating boiler.

And here you will learn how automation for gas heating boilers works. Boilers by installation method and types of energy-dependent systems.

Designs and parameters of induction furnaces

Duct

One of the options for making an induction furnace with your own hands is a channel one.

To make it, you can use ordinary welding transformer, operating at a frequency of 50 Hz.

In this case, the secondary winding of the transformer must be replaced with a ring crucible.

In such a furnace you can melt up to 300-400 g of non-ferrous metals, and it will consume 2-3 kW of power. Such a furnace will have high efficiency and will allow the smelting of high quality metal.

The main difficulty in making a channel induction furnace with your own hands is purchasing a suitable crucible.

To make the crucible, a material with high dielectric properties and high strength must be used. Such as electroporcelain. But such material is not easy to find, and even more difficult to process at home.

Crucible

The most important elements of an induction crucible furnace are:

inductor;
power supply generator.

As an inductor for crucible furnaces with a power of up to 3 kW, you can use a copper tube or wire with a diameter of 10 mm or a copper busbar with a cross-section of 10 mm². The diameter of the inductor can be about 100 mm. The number of turns is from 8 to 10.

In this case, there are many modifications of the inductor. For example, it can be made in the form of a figure eight, trefoil or other shape.

During operation, the inductor usually becomes very hot. In industrial designs, the inductor uses water cooling of the turns.

At home, using this method is difficult, but the inductor can work normally for 20-30 minutes, which is quite enough for home work.

However, this mode of operation of the inductor causes the appearance of scale on its surface, which sharply reduces the efficiency of the furnace. Therefore, from time to time the inductor has to be replaced with a new one. To protect against overheating, some experts suggest covering the inductor with a heat-resistant material.

High frequency alternator - other essential element induction type crucible furnace. Several types of such generators can be considered:

transistor generator;
thyristor generator;
generator using MOS transistors.

The simplest alternating current generator for powering an inductor is a self-excited generator, the circuit of which has one KT825 type transistor, two resistors and a coil feedback. Such a generator can generate power up to 300 W, and the generator power is adjusted by changing the DC voltage of the power source. The power source must provide a current of up to 25 A.

The thyristor generator proposed for the crucible furnace includes in the circuit a T122-10-12 type thyristor, a KN102E dinistor, a number of diodes and pulse transformer. The thyristor operates in pulse mode.

DIY induction furnace

Such ultra-high-frequency radiation can negatively affect human health. In accordance with Russian safety standards, it is allowed to work with high-frequency vibrations at an electromagnetic energy flux density of no more than 1-30 mW/m². For this generator, as calculations have shown, this radiation at a distance of 2.5 m from the source reaches 1.5 W/m². This value is unacceptable.

The MOSFET oscillator circuit includes four MOSFET transistors of the IRF520 and IRFP450 types and is a push-pull oscillator with independent excitation and an inductor connected in a bridge circuit. An IR2153 type microcircuit is used as a master oscillator. To cool the transistors, a radiator of at least 400 cm² and airflow are required.
This generator can provide power up to 1 kW and vary the oscillation frequency from 10 kHz to 10 MHz. Thanks to this, a furnace using a generator of this type can operate in both melting and surface heating modes.

Bake long burning can work on one bookmark from 10 to 20 hours. During manufacturing, it is necessary to take into account the design features so that it produces maximum heat at minimum costs energy. Read about how to properly assemble the oven on our website.

You might be interested in learning about gas garage heaters. What it should be like to ensure warmth and safety, read the material.

Use for heating

To heat a home, stoves of this type are usually used in conjunction with a hot water boiler.

One of the options for a homemade induction-type water heating boiler is a design that heats a pipe with flowing water using an inductor, powered from the network using an HF welding inverter.

However, as analysis of such systems shows, due to large losses of electromagnetic field energy in the dielectric tube, the efficiency similar systems extremely low. In addition, heating a home requires very large number electricity, which makes such heating economically unprofitable.

From this section we can draw conclusions:

Most acceptable option A self-made induction furnace is a crucible version with a power generator using MOS transistors.
Using a homemade induction furnace to heat a home is not economically profitable. In this case, it is better to purchase a factory system.

Features of operation

An important issue when using an induction oven is safety.

As mentioned above, crucible-type furnaces use high-frequency power sources.

Therefore, when operating an induction furnace, the inductor must be positioned vertically; before turning on the furnace, a grounded shield must be put on the inductor. When the furnace is turned on, it is necessary to observe the processes occurring in the crucible from a distance, and after completing the work, immediately turn it off.

When operating a home-made induction furnace, you must:

Take measures to protect the oven user from possible high frequency radiation.
Take into account the possibility of burns from the inductor.

When working with a stove, thermal hazards must also be taken into account. Touching the skin with a hot inductor can cause severe burns.

Induction furnaces are used for smelting metals and are distinguished by the fact that heating in them occurs through electric current. The current is excited in the inductor, or more precisely in a constant field.

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

into electromagnetic;
electrical;
thermal

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

Pay attention! Induction designs come in two types - with or without a core. In the first case, the metal is placed in a tubular trough, which is located around the inductor. The core is located in the inductor itself. The second option is called crucible, because in it the metal and the crucible are already inside the indicator. Of course, there can be no talk of any core in this case.

In today's article we will talk about how to makeDIY induction oven.

Among the many advantages, the following are worth highlighting:

environmental cleanliness and safety;
increased homogeneity of the melt due to active movement of metal;
speed – the oven can be used almost immediately after switching on;
zonal and focused energy orientation;
high melting rate;
no fumes from alloying substances;
possibility of temperature adjustment;
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 melting metal, so a reduction in the thickness of the lining will be required. This will soon lead to the lining itself failing.

Video – Induction oven

Industrial Application

Both designs are used in the smelting of cast iron, aluminum, steel, magnesium, copper and precious metals. The useful volume of such structures can range from several kilograms to 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, non-ferrous metals are melted.
Industrial frequency designs are used in iron smelting.
Resistance structures are intended for melting aluminum, aluminum alloys, and zinc.

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

Household use

The efficiency of induction cookers reaches 90%. For comparison: for electric stoves it is approximately 55-65%, and for gas stoves it is no more than 30-50%. But in fairness, it is worth noting that special utensils are required to operate the described stoves.

Homemade induction furnace

Not long ago, domestic radio amateurs clearly demonstrated that you can make an induction furnace yourself. Today there are a lot of different schemes and manufacturing technologies, but we have presented only the most popular of them, which means the most effective and easy to implement.

Induction furnace made from high frequency generator

Below is an electrical circuit 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 lamp for the readiness indicator.

Pay attention! The main difference between a stove made according to this scheme is the condenser handle - in this case it is located outside.

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

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

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

Video - Construction of a welding inverter

The essence of the design is as follows: a pair of graphite brushes is installed, and granite powder is poured between them, after which the connection is made to the step-down transformer. It is typical that during smelting there is no need to worry about electric shock, since there is no need to use 220 V.

Assembly technology

Step 1. The base is assembled - a fireclay brick box measuring 10x10x18 cm, laid on fire-resistant tiles.

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

Pay attention! 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 designed for 380 V, then it can be rewound, although many experienced electricians claim that you can leave everything as is

Step 4. The transformer is wrapped with thin aluminum - this way the structure will not get too hot during operation.

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

The main advantage of such a furnace is its high temperature, which is even suitable for smelting platinum or palladium. But among the disadvantages are the rapid heating of the transformer, small volume (no more than 10 g can be smelted at a time). For this reason, a different design will be required for larger volume melts.

So, to smelt large volumes of metal you will need a furnace with nichrome wire. The operating principle of the design is quite simple: electric current is supplied to a nichrome spiral, which heats up and melts the metal. There are a lot of different formulas on the Internet for calculating the length of a wire, but they are all, in principle, the same.

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

Step 2. The wire must be wound. To do this, you will 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 asbestos thread - this way the molten metal will not flow out.

Step 5. The finished coil is placed in a high power lamp socket. Such cartridges are usually ceramic and have the required size.

Advantages of this design:

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

But there are, of course, disadvantages:

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

Pay attention! You cannot add metal to the stove if the previous portion has already been melted there. Otherwise, all the material will scatter throughout the room, moreover, it can injure your eyes.