Do-it-yourself induction hardening installation diagram. Melting metal at home in an electric induction furnace. Assembling a vortex induction heater

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 suit specific task, changing the parameters of the inductor and the output signal generator sets- this is how you can achieve their maximum efficiency.

Induction furnaces were invented back in 1887. And within three years the first industrial development appeared, with the help of which various metals were smelted. 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, or 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 induction furnaces:

• Duct.
• Crucible.

We won’t describe them all here. distinctive features. Just note that the duct option is a design that is similar to welding machine. In addition, in order to melt metal in such furnaces, it was necessary to leave a little melt, without which the process simply 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 enough a large number of Soviet electrical and electronic devices, which 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. The optimal distance between them is 5-7 mm. 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. In order to make it clearer what we are 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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A home induction furnace can handle melting relatively small portions of metal. However, such a forge does not need either a chimney or bellows pumping air into the smelting zone. And the entire structure of such a furnace can be placed on desk. Therefore, heating using electrical induction is the optimal way to melt metals at home. And in this article we will look at the designs and assembly diagrams of such stoves.

How does an induction furnace work - generator, inductor and crucible

In factory workshops you can find channel induction furnaces for melting non-ferrous and ferrous metals. These installations have very high power, set by an internal magnetic circuit, which increases the density of the electromagnetic field and the temperature in the furnace crucible.

However, channel structures consume large portions of energy and take up a lot of space, so at home and in small workshops an installation without a magnetic circuit is used - a crucible furnace for melting non-ferrous/ferrous metals. You can even assemble such a structure with your own hands, because the crucible installation consists of three main components:

• A generator that produces alternating current at high frequencies, which are necessary to increase the density of the electromagnetic field in the crucible. Moreover, if the diameter of the crucible can be compared with the wavelength of the alternating current frequency, then this design will make it possible to transform up to 75 percent of the electricity consumed by the installation into thermal energy.
• The inductor is a copper spiral created based on an accurate calculation of not only the diameter and number of turns, but also the geometry of the wire used in this process. The inductor circuit must be configured to amplify power as a result of resonance with the generator, or more precisely with the frequency of the supply current.
• The crucible is a refractory container in which all the melting work takes place, initiated by the occurrence of eddy currents in the metal structure. In this case, the diameter of the crucible and other dimensions of this container are determined strictly according to the characteristics of the generator and inductor.

Any radio amateur can assemble such a stove. To do this he needs to find correct scheme and stock up on materials and parts. You can find a list of all this below in the text.

What stoves are assembled from - selecting materials and parts

The design of a homemade crucible furnace is based on the simplest laboratory Kukhtetsky inverter. The circuit diagram of this transistor installation is as follows:

Based on this diagram, you can assemble an induction furnace using the following components:

• two transistors - preferably field-effect type and brand IRFZ44V;
• copper wire with a diameter of 2 millimeters;
• two diodes of the UF4001 brand, even better - UF4007;
• two throttle rings - they can be removed from the old desktop power supply;
• three capacitors with a capacity of 1 μF each;
• four capacitors with a capacity of 220 nF each;
• one capacitor with a capacity of 470 nF;
• one capacitor with a capacity of 330 nF;
• one 1 watt resistor (or 2 resistors of 0.5 watt each), designed for a resistance of 470 ohms;
• copper wire with a diameter of 1.2 millimeters.

Additionally, you'll need a couple of heatsinks - these can be removed from old motherboards or CPU coolers, and accumulator battery with a capacity of at least 7200 mAh from an old source uninterruptible power supply at 12 V. Well, in this case, a crucible container is actually not needed - bar metal will melt in the furnace, which can be held by the cold end.

Step-by-step instructions for assembly - simple operations

Print out and hang the drawing of Kukhtetsky’s laboratory inverter above your desk. After this, arrange all the radio components by type and brand and heat up the soldering iron. Attach two transistors to the radiators. And if you will be working with the stove for more than 10-15 minutes at a time, attach computer coolers to the radiators, connecting them to a working power supply. The pinout diagram for transistors from the IRFZ44V series is as follows:

Take 1.2 millimeter copper wire and wrap it around ferrite rings, making 9-10 turns. As a result, you will get chokes. The distance between the turns is determined by the diameter of the ring, based on the uniformity of the pitch. In principle, everything can be done “by eye”, varying the number of turns in the range from 7 to 15 revolutions. Assemble a battery of capacitors by connecting all parts in parallel. As a result, you should have a 4.7 uF battery.

Now make an inductor using 2mm copper wire. The diameter of the turns in this case can be equal to the diameter of a porcelain crucible or 8-10 centimeters. The number of turns should not exceed 7-8 pieces. If during testing the furnace power seems insufficient to you, redesign the inductor by changing the diameter and number of turns. Therefore, in the first couple of stages, it is better to make the inductor contacts not soldered, but detachable. Next, assemble all the elements on a PCB board, based on the drawing of Kukhtetsky’s laboratory inverter. And connect a 7200 mAh battery to the power contacts. That's all.

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

Induction furnaces are divided into two types:

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

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

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

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

Read also: How to make a clay kiln

Induction Furnace Components

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

Crucible furnace structure

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

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

How to make an induction oven

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