Induction furnace for melting aluminum. How to make an induction heater with your own hands? Advantages over other types of melting furnaces

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 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 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 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 alternating current. 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.

Kinds

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

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 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.

Can be used as an induction furnace generator for metal melting welding inverter. You can also assemble a generator using the diagrams 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 operating from a welding inverter, its housing must be grounded! The outlet and wiring must be rated for the current drawn by the inverter.

The heating system of a private house is based on the operation of a stove 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.

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. To make them, copper wire with a diameter of 1.2 mm is wound around 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 from 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

You can assemble a more powerful induction furnace for melting metals 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 output frequency is 27.12 MHz.

To assemble the circuit you need:

4 electron tubes - tetrodes, 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:

From copper tube perform the inductor 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 10 mm larger than the diameter of the crucible placed inside.
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.
The circuit includes a tuning capacitor variable capacity, its handle is also brought out onto the body.

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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.

Execute air cooling using a fan is possible, provided the fan is located sufficiently remotely. 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 high-voltage elements, so it must be placed in a closed housing to prevent accidental contact with the elements.
The electromagnetic field can affect objects located outside the device body. Therefore, before work, it is better to wear clothes without metal elements and remove complex devices from the operating 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 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.

Note! 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.

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 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.

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, and zinc.

Note! 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.

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 the electrical circuit for making 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.

Note! 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 characteristic that during smelting there is no need to fear electric shock, since there is no need to use 220 V.

Assembly technology

Step 1. The base is assembled - a box made of fireclay bricks 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.

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 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 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.

Note! 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 yourself. 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.

Chief Editor

How to make an induction heater with your own hands?

Electric heaters

Induction heaters work on the principle of “derived 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 cookware, 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 food.

A do-it-yourself induction cooker must be manufactured in compliance with all standards 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 made at home induction cooker, 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 furnace you will need 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 manufacturing 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 radiators from aluminum alloy, 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 an 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 manufacturing process of the electronic generator and coil itself 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, 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. 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 install 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 pipe from of stainless steel with a diameter of 20 mm. 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 sufficient for flow-through heating of liquid with a small circulation of water, to values allowing the 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 stainless pipe, the heated water will rise up, and its place will be taken by a colder liquid.
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 inverter is available welding machine direct current, 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 power supply 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 of homemade induction heating devices, does not always eliminate 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 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 specified in the article, but operate this device permanently not recommended due to imperfections self-made shielding of this device, because of this, the human body may be exposed to harmful electromagnetic radiation that can negatively affect health.

From 75,000 rub.

The table below shows some of the possible configurations and their prices.
Dealer prices are negotiated separately.

Induction melting furnaces SL Made in small batches and to order. This is the most affordable series of stoves with a simple design and high reliability.
Desktop induction melting furnace for melting of non-ferrous metal. Graphite crucibles 0.5 -2 are used. Below is a table with parameters.

The possible range includes the entire line of melting furnaces used in small workshops, in particular in the jewelry industry. Tabletop induction melting furnaces can be manufactured to melt metal weighing up to 2 kg. The name of the furnace reflects its power and the mass of molten metal. For example: SL2200-1 , this means that a 2.2 kW furnace is designed for melting non-ferrous metal weighing 1 kg.

In the "Gallery" section there are photographs of induction furnaces: Gallery.
Cooling systems have been specially designed for tabletop ovens: .
In the "Downloads" section there is a video of an autonomous melting complex with a cooler based on a tabletop furnace: furnace with cooler video.

Tabletop oven tests: youtube:

Download: video of a tabletop induction furnace in operation

Induction melting furnaces SLB are made to order. Customer requirements and working conditions vary greatly. The floor-standing version can be made for crucibles up to 5 kg. Power can reach 12kVA. A cooling system can be installed at the bottom of the furnace. If necessary, a crucible lifting device can be installed. The production time for a floor-standing oven is from two weeks.

In the "Gallery" section you can see photographs of induction furnaces: Gallery.

In the "downloads" section you can download a video of the operation of a floor-standing induction furnace in a foundry: Operation of a floor-standing induction furnace video.

We are happy to help clients in their work. We answer any questions by phone and e-mail, we organize test runs of furnaces, deliver equipment to any region Payment and delivery.

The table shows possible options configurations

options	SL1800-0.5	SL2500-1	SL2500-2	SLB6000-3
Power consumption, VA ( power)	1800	2500	2500	6000
Mass of metal in the crucible, kg ( crucible kg.)
Rated frequency of the circuit current, kHz ( frequency)	70-120	70-120	70-120	70-120
Maximum temperature ( temperature )	1200ºC	1200ºC	1200ºC	1200ºC
Heating time from 20 to 1000 º, min ( heating time )
Inductor cooling water(water cooling)
Supply network (supply)	220 V, 50 Hz	220 V, 50 Hz	220 V, 50 Hz	380 V
Temperature controller ( temperature controller )	Autonics TC4W	Autonics TC4W	Aries TRM10	Aries TRM10
Defence from idle move ( idle protection )
Water flow sensor ( water flow sensor )
Case dimensions )	460 x 240 x 260	460 x 240 x 260	460 x 240 x 260	710 x 600 x 1000
Price, thousand rubles

We can make a stove for a graphite crucible of any size.

Required for ovens water cooling. We manufacture special coolers. With their help, a complete autonomous melting complex is obtained. Coolers for induction furnaces.

You can download the video in "downloads" - stove with cooler video

Furnaces for metal volumes greater than 1 kg are manufactured in floor options in agreement with the customer.

The maximum temperature is determined by the power and thermal insulation of the crucible. For SL series ovens, 1200 degrees is indicated, since the controller cannot measure temperatures higher. In addition, graphite crucibles burn heavily at higher temperatures.
Furnaces can be equipped with "Aries" or "Autonics" temperature controllers. "Aries" controllers are more accurately calibrated by temperature, and "Autonics" have a simpler interface.

Furnaces can be equipped with ceramic crucible lids.

Lids can be purchased separately.

Floor-standing furnaces can be equipped with pedal-driven crucible lifting devices.

It is convenient to use a granulator for melting metals. It is filled with water; the melall must be poured in a thin stream. The result is small granules that are convenient to weigh, mix and use in further production.

Induction melting theory:

There are two possible principles of induction melting of metal. In the first case, the pumping frequency of the inductor is relatively low. The crucible is made of graphite. The energy of the inductor is absorbed both by the crucible and partly by the metal inside the crucible. As a result, the metal melts, heating up from the hot crucible and heating up on its own. In the second option, the crucible is made of non-conducting material. Thus, the inductor induces eddy currents only in the metal itself. This induction heating method requires a higher pump frequency.

In any of the above cases, an electrical transformer is obtained, in the primary circuit of which there is an inductor, and the secondary circuit is the heated object. The matter may still be complicated by the ferromagnetic properties of materials. The complexity lies in the distributed nature of the fields and the change in the properties of ferromagnets when passing through the Curie point. Because of all this, furnaces for non-ferrous metals are fundamentally different from furnaces for steel, nickel, etc.

The main problem with induction melting furnaces is the heating of the inductor. Although currents of hundreds and thousands of amperes flow in it, this is not the main reason for overheating of the inductor. It's all about the radiation of the heated object. For example, if a crucible is inserted into the inductor, then at a high temperature it begins to “glow” in the infrared range. Thus, it begins to strongly heat the inductor. Because you can't do it big gap between the inductor and the crucible, the inductor has to be well cooled. For increasing efficiency stoves need to have a minimum gap and have minimal heat loss from the heated object. Consequently, the entire system (inductor, crucible, thermal insulation, cooling) must be thought out and well balanced in both electrical and thermal parameters. A simple but important idea follows from this: the stove is created for a very specific crucible. If you push a foreign crucible into the inductor of an induction stove, then best case scenario There will simply be poor heating, or at worst, there is a chance of ruining the stove.

Craftsmen who work with metal tend to switch to induction furnaces because of their high quality. In this case, stocks of crucibles from previously used furnaces may remain. In addition, several ovens can be used for different purposes. In this case, it is convenient to have universal crucibles that are suitable for all furnaces. We offer custom-made induction furnaces for different crucible sizes, within the technological limitations of the housing and cooling system.

Our tabletop ovens, manufactured in small batches, use a uniform casing. It allows the use of crucibles with a capacity of up to one kilogram of non-ferrous metal. Structurally, the case is made of two compartments. One contains all the electronics, the other is the working one, it contains the inductor and the thermal insulation system. The inductor compartment has double steel walls to shield radiation. This way there is no need to chalk out a safe zone for the operator on the floor. Saving chalk and paper for sick leave is obvious.

The electrical safety of the stove is determined by the galvanic isolation of the inductor from the network. The inductor is powered by an internal converter through a special pulse transformer. The stove body structurally does not allow the operator to touch any live parts. Transistors inside the stove are used only in insulated housings, which does not allow potential to reach even the internal radiators. The stove power cord contains a ground wire. If there is no grounding in your network, you can connect an external grounding.

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

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

A homemade device is unlikely to be suitable for implementation complex tasks, but will cope with basic functions quite well. The device can be assembled on the basis of a working welding inverter made of transistors, or using lamps. The most productive device is the one based on lamps due to its high efficiency.

Working principle of induction furnace

Heating of the metal placed inside the device occurs by converting electromagnetic pulses into heat energy. Electromagnetic pulses are generated by a coil of copper wire or pipe.

Diagram of an induction furnace and heating circuits

When the device is connected, an electric current begins to flow through the coil, and a electric field changing its direction over time. The functionality of such an installation was first described by James Maxwell.

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

Varieties

Induction coil stoves are usually divided into two types depending on the type of construction:

Duct;
Crucible.

In the first devices, the metal to be melted is located in front of the induction coil, and in the second type of furnace it is placed inside it.

You can assemble the oven by following these steps:

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

Use for heating

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

Another drawback is based on the device’s consumption of large amounts of electricity during operation, which is why the device falls into the category of economically unprofitable.

System cooling

A device assembled independently must be equipped with a cooling system, since during operation all components will be exposed to high temperatures, and the structure may overheat and break. In store-bought ovens, cooling is done with water or antifreeze.

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

For home ovens, you can try using a regular paddle fan. Please note that the device should not be placed too close to the oven, as metal parts Fans negatively affect the performance of the device, and are also capable of breaking vortex flows and reducing the performance of the entire system.

Precautions when using the device

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

Some elements of the installation, as well as the metal that is melting, are subject to intense heat, resulting in a risk of burns;
When using a lamp oven, be sure to place it in a closed case, otherwise there is a high risk of electric shock;
Before working with the device, remove all materials from the operating area of the device. metal elements and complex electronic devices. The device should not be used by people who have a pacemaker.

An induction type metal melting furnace can be used for tinning and forming metal parts.

A homemade installation can be easily adjusted to suit specific conditions by changing some settings. If you adhere to the indicated diagrams when assembling the structure, and also follow basic safety rules, your homemade device will be practically no inferior to store-bought household appliances.

Induction furnaces were invented back in 1887. And three years later the first one appeared industrial development, with which they melted various metals. I would like to note that in those distant years these stoves were a novelty. The thing is that scientists of that time did not quite understand what processes were occurring in it. Today we figured it out. In this article we will be interested in the topic - do-it-yourself induction furnace. How simple is its design, is it possible to assemble this unit at home?

Principle of operation

You need to start assembling by understanding the principle of operation and structure of the device. Let's start with this. Pay attention to the figure above, we will understand it according to it.

The device includes:

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

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

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

Crucible furnace

Varieties

There are two main designs of induction furnaces:

Duct.
Crucible.

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

How it works

Why do you need such a stove at home?

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

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

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

Coil with battery (generator)

Stove components

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

Please note that the turns of the copper tube should not touch each other. Optimal distance there are 5-7 mm between them. The coil itself should not touch the screen. The distance between them is 50 mm.

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

Generator

In principle, making a generator with your own hands is not a problem. But this is only possible if you have sufficient knowledge in radio electronics at the level of an average radio amateur. If you don’t have such knowledge, then forget about the induction stove. The most important thing is that you also need to skillfully operate this device.

If you are faced with the dilemma of choosing a generator circuit, then take one piece of advice - it should not have a hard current spectrum. To make it clearer what we mean we're talking about, we offer the most simple diagram generator for an induction furnace in the photo below.

Generator circuit

Required knowledge

The electromagnetic field affects all living things. An example is microwaved meat. Therefore, it is worth taking care of safety. And it doesn’t matter whether you are assembling the stove and testing it or working on it. There is such an indicator as energy flux density. So it depends on the electromagnetic field. And the higher the frequency of radiation, the worse it is for the human body.

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

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Many people believe that the process of smelting metal requires huge structures, almost factories with big amount personnel. But there is also such a profession as a jeweler and metals such as gold, silver, platinum and others used to make openwork and exquisite jewelry, some of which are rightfully considered true works of art. A jewelry workshop is an enterprise that does not tolerate excessive scale. And the melting process is simply necessary in them. Therefore, an induction furnace for melting metal is necessary here. It is not big, and very effective, and easy to use.

The working principle of an induction furnace is wonderful example, as an undesirable phenomenon is used with increased efficiency. The so-called Foucault eddy induction currents, which usually interfere in any type of electrical engineering, are here aimed only at a positive result.

In order for the metal structure to begin to heat up and then melt, it must be placed under these very Foucault currents, and they are formed in an induction coil, which, by and large, is what the furnace is.

Simply put, everyone knows that while working, any electrical appliance starts to heat up. An induction furnace for melting metal uses this otherwise undesirable effect to its full potential.

Advantages over other types of melting furnaces

Induction furnaces are not the only invention used for melting metals. There are also famous open-hearth furnaces, blast furnaces and other types. However, the stove we are considering has a number of undeniable advantages over all others.

Furnaces operating on the induction principle can be quite compact, and their placement will not cause any difficulties.
High melting speed. If other furnaces for melting metal require several hours just to heat up, an induction furnace copes with this several times faster.
The efficiency is only slightly less than 100%.
In terms of melt purity, the induction furnace confidently takes first place. In other devices, the workpiece prepared for the melt is in direct contact with heating element, which often leads to contamination. Foucault currents heat the workpiece from the inside, affecting the molecular structure of the metal, and no by-products enter it.

This last advantage is essential in jewelry, where the frequency of a material increases its value and uniqueness.

Furnace placement

Compact induction furnace, depending on size, can be floor-standing or tabletop. Whatever option you choose, there are a few basic rules for choosing a place to put it.

Despite the simplicity of handling the stove, it is still an electrical device that requires compliance with safety measures. And the first thing that needs to be taken into account during installation is the presence of the correct power source that matches the device model.
Possibility of high-quality grounding.
Providing the installation with a water supply.
Tabletop ovens require a stable base.
But most importantly, nothing should interfere during work. Even if the melt is not too large in volume and mass, its temperature is more than 1000 degrees and accidentally splashing it out of the mold means causing very severe injury to yourself or someone nearby.

There is nothing to say about the fact that there should be no flammable or, especially, explosive materials near a working induction furnace. But a fire shield within walking distance is absolutely necessary.

Types of induction furnaces

Two types of induction furnaces are widely used: channel and crucible. They differ only in the method of working with them. In all other respects, including advantages, such melting furnaces are very similar. Let's consider each option separately:

Channel furnace. The main advantage of this type is a continuous cycle. You can load a new portion of raw materials and unload already molten metal directly during heating. The only difficulty may arise during startup. The channel through which the liquid metal will be discharged from the furnace must be filled.
Crucible furnace. Unlike the first option, each portion of metal will have to be loaded separately. That's the point. The raw material is placed in a heat-resistant crucible and placed inside the inductor. After the metal has melted, it is drained from the crucible and only then the next portion is loaded. This furnace is ideal for small workshops where large masses of molten raw materials are not required.

The main advantage of both options is the speed of production. However, the crucible furnace wins here too. In addition, it is quite possible to make it with your own hands in almost home conditions.

A homemade induction furnace is not fraught with any difficulties so that it cannot be assembled a common person, at least a little familiar with electrical engineering. It has only three main blocks:

Generator.
Inductor.
Crucible.

The inductor is a copper winding that you can make yourself. You will have to look for the crucible either in the appropriate stores or get it in other ways. And the following can be used as a generator: a welding inverter, a self-assembled transistor or lamp circuit.

Induction furnace on a welding inverter

The simplest and most widespread option. Efforts will have to be expended only on the construction of the inductor. Take a thin-walled copper tube 8-10 cm in diameter and bend it according to the desired pattern. The turns should be spaced at a distance of 5-8 mm, and their number depends on the characteristics and diameter of the inverter. The inductor is fixed in a textolite or graphite case, and a crucible is placed inside the installation.

Transistor induction furnace

In this case, you will have to work not only with your hands, but also with your head. And run around the shops looking for the necessary spare parts. After all, you will need transistors of different capacities, a couple of diodes, resistors, film capacitors, two copper wires of different thicknesses and a couple of inductor rings.

Before assembly, it is necessary to take into account that the resulting circuit will become very hot during operation. Therefore it is necessary to use fairly large radiators.
Capacitors are assembled in parallel into a battery.
Copper wire with a diameter of 1.2 mm is wound onto the throttle rings. Depending on the power, the turns should be from 7 to 15.
A cylindrical object, suitable in diameter to the size of the crucible, is wound with 7-8 turns of copper wire with a diameter of 2 mm. The ends of the wire are left long enough for connection.
According to a special scheme, everything is mounted on the board.
The power source can be a 12-volt battery.
If necessary, you can make a textolite or graphite case.
The power of the device is adjusted by increasing or decreasing the turns of the inductor winding.

Assembling such a device yourself is not easy. And you can take on this work only if you are confident in the correctness of your actions.

Induction furnace with lamps

Unlike a transistor oven, a lamp oven will be much more powerful, which means you will have to handle both it and the circuit more carefully.

4 beam lamps connected in parallel will generate high frequency currents.
Copper wire is bent into a spiral. The distance between the turns is 5 or more millimeters. The coils themselves are 8-16 cm in diameter. The inductor should be of such a size that the crucible can easily fit inside.
The inductor is placed in a housing made of a non-conducting material (textolite, graphite).
You can put a neon indicator lamp on the body.
You can also include a tuning capacitor in the circuit.

Making both circuits requires having some knowledge, which can be obtained, but it is better if a real specialist does it.

Cooling

This question is probably the most difficult of all those that are posed to a person who decides to independently assemble a melting apparatus based on inductive principle. The fact is that it is not recommended to place the fan directly next to the stove. Metal and electrical parts of the cooling device can adversely affect the operation of the stove. A fan located far away may not provide the necessary cooling, which will lead to overheating.

The second option is to carry out water cooling. However, performing it efficiently and correctly at home is not only difficult, but also not financially profitable. In this case, it’s worth thinking about: wouldn’t it be more economical to purchase an industrial version of an induction furnace, produced at a factory, in compliance with all the necessary technologies?

Safety precautions when smelting metal in an induction furnace

There is no need to dwell heavily on this topic, since almost everyone knows the basic safety regulations. We should dwell only on those issues that are unique to this type of equipment.

Let's start with personal safety. When working with an induction furnace, you should be well aware that the temperatures here are very high, and this poses a risk of burns. The device is also electric and requires special attention.
If you bought a finished stove, you should pay attention to the radius of influence of the electromagnetic field. Otherwise, watches, phones, video cameras and other electronic gadgets may begin to malfunction or even break down completely.
Work clothes should be selected with non-metallic fasteners. Their presence, on the contrary, will affect the operation of the furnace.
Particular attention should be paid to the lamp oven in this regard. All high voltage elements must be hidden in the housing.

Of course, such equipment is unlikely to be useful in a city apartment, but radio amateurs who are constantly engaged in tinning and jewelry makers cannot do without an induction stove. For them, this thing is very useful, one might say irreplaceable, and how it helps in their work, it is better to ask them themselves.