How to assemble your own induction furnace for melting metal at home
Metal melting by induction is widely used in different industries: metallurgy, mechanical engineering, jewelry. A simple induction type furnace for melting metal at home can be assembled with your own hands.
Heating and melting of metals in induction furnaces occurs by internal heating and changing the crystal lattice of the metal when high-frequency eddy currents pass through them. This process is based on the phenomenon of resonance, in which the eddy currents have a maximum value.
In order to cause eddy currents flowing through the melting metal, it is placed in the range of action of electromagnetic field of inductor. coil. It may be in the form of a spiral, figure of eight or trefoil. The shape of the inductor depends on the size and shape of the heated workpiece.
The inductor coil is connected to an AC power supply. In production melting furnaces, currents of industrial frequency of 50 Hz are used, for melting of small amounts of metals in jewelry, high-frequency generators are used, as a more effective.
The eddy currents are formed on a loop enclosed by the magnetic field of the inductor. Therefore, heating of current-conducting elements is possible both inside and outside the coil.
Therefore, induction furnaces are of two types: channel-based, in which the capacity for melting metals are channels located around the inductor, and the core is located inside it; crucible-based, they use a special capacity. a crucible made of heat-resistant material, usually removable.
Channel furnace is too large and designed for industrial volumes of metal melting. It is used in smelting cast iron, aluminum and other non-ferrous metals.
The crucible furnace is quite compact, it is used by jewelers, radio amateurs, such a furnace can be assembled with their hands and used at home.
Self-made furnace for melting metals has a fairly simple design and consists of three main blocks, placed in a common housing: an alternator of high frequency; an inductor. a spiral winding of copper wire or a tube, made by hand; a crucible.
The crucible is placed in the inductor, the winding ends are connected to a current source. When the current flows in the coil, an electromagnetic field with a variable vector appears around it. In the magnetic field, eddy currents occur, directed perpendicular to its vector and passing through a closed circuit inside the winding. They pass through the metal placed in the crucible, while heating it to the melting point.
Advantages of the induction furnace:
fast and even heating of the metal immediately after turning on the installation; the direction of heating. only metal, not the entire installation is heated; high melting rate and homogeneity of the melt; no evaporation of alloying components of the metal; the installation is environmentally friendly and safe.
A welding inverter can be used as a generator of induction furnace for melting metal. You can also build a generator with your own hands according to the diagrams below.
Furnace for melting metal on the welding inverter
This design is characterized by simplicity and safety, since all inductors are equipped with internal overload protections. The entire furnace assembly in this case comes down to making the inductor with your own hands.
Execute it usually in the form of a spiral of copper thin-walled tube with a diameter of 8-10 mm. It is bent according to the template of the desired diameter, placing the coils at a distance of 5-8 mm. The number of windings is 7 to 12 depending on the inductor diameter and characteristics. The total resistance of the inductor must be such as not to cause overcurrent in the inverter, otherwise it will be tripped by the internal protection.
The inductor can be fixed in a graphite or textolite case and an crucible can be set inside. It is also possible to place the inductor on a heat-resistant surface. The housing must not conduct current, otherwise eddy currents will flow 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.
Always ground the case of the welding inverter when operated with it! The socket and wiring must be rated for the current consumption of the inverter.
At the heart of the heating system in a private home is the work of the furnace or boiler, high performance and long trouble-free life which depends on the brand and installation of heating devices, as well as the proper installation of chimney.
In this article you will find recommendations for choosing a solid fuel boiler, and in the next one you will get acquainted with the types and rules of chimney installation:
Transistor-Based Induction Furnace: Schematic
There are many different ways to assemble an induction heater with your own hands. A fairly simple and proven circuit of a metal melting furnace is shown in the figure:
To assemble the installation with your own hands, you will need the following parts and materials: two field-effect transistors type IRFZ44V; two diodes UF4007 (you can also use UF4001); a 470 ohm, 1 W resistor (you can take two 0.5 W in series); 250 V film capacitors: 3 pcs capacity 1 uF; 4 pcs capacity 220 nF; 1 pc capacity 470 nF; 1 pc capacity 330 nF; copper wire with enamel insulation Ø1,2 mm; copper wire with enamel insulation Ø2 mm; two rings from chokes taken from computer power supply.
The sequence of assembly with their own hands:
Field-effect transistors are mounted on heat sinks. Since the circuit gets very hot during operation, these heat sinks must be big enough. You can also install them on one heat sink, but then you need to isolate the transistors from the metal with pads and washers of rubber and plastic. Field effect transistors pinout is shown on the picture.
Two chokes must be made. To make them, copper wire with a diameter of 1.2 mm is wound onto rings taken from any computer power supply. These rings are made of powdered ferromagnetic iron. On them wind from 7 to 15 turns of wire, trying to keep the distance between the turns.
Assemble the above capacitors to a battery with a total capacitance of 4.7 µF. Capacitors are connected in parallel.
Winding the inductor with copper wire of 2 mm diameter. Wind 7-8 turns of the winding on a cylindrical object of a suitable diameter for the crucible, leaving the ends long enough to be connected to the circuit. Connect the elements on the board according to the diagram. 12 V, 7.2 A/h rechargeable battery is used as a power source. Current consumption in operation. about 10 A, the battery capacity in this case is enough for about 40 minutes.If necessary, make the furnace body from heat-resistant material, such as textolite.The output of the device can be changed by changing the number of winding turns of the inductor and their diameter.
The heater elements can overheat in continuous operation! A fan can be used for cooling.
Induction heater for melting metal
Tube induction furnace
A more powerful induction furnace for melting metals can be assembled with your own hands on electronic tubes. Schematic diagram of the device is shown in the picture.
To generate high-frequency current, 4 beam lamps connected in parallel are used. Copper tube with diameter of 10 mm is used as inductor. Installation is equipped with a trimmed capacitor for power regulation. The output frequency is 27.12 MHz.
To assemble the circuit we need:
4 tetrode electron tubes, you can use 6L6, 6P3 or G807; 4 chokes of 100 1000 uHg; 4 capacitors of 0.01 uF; neon lamp indicator; trimmer.
To assemble the device with your own hands:
Copper tubes are made into inductors by bending them into a spiral shape. The diameter of the coils is 8-15 cm, the distance between the coils 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 placed inside of the crucible. The inductor is placed in a housing. It can be made of heat-resistant non-conductive material, or of metal, with thermal and electrical insulation from the elements of the circuit. Assemble the tube cascades according to the circuit with capacitors and chokes. Cascades are connected in parallel. Connect a neon indicator lamp. it will signal when the circuit is ready to work. The lamp is led to the housing of the unit. Variable capacity variable capacitor is included in the circuit, and its knob is also placed on the housing.
For all fans of delicacies cooked by cold smoking, we suggest you learn here how to make a smoker with your own hands quickly and easily, and here to see photos and video instructions for making smoke generator for cold smoking.
Industrial melting plants are equipped with forced cooling system with water or antifreeze. The execution of the water cooling in the home will require additional costs, comparable in price to the cost of the installation for melting metal.
Air cooling with a fan can be accomplished if the fan is positioned far enough away. Otherwise, the metal winding and other elements of the fan will serve as an additional circuit for closing the eddy currents, which will reduce the efficiency of the installation.
Components of electronic and lamp circuits may also heat up actively. Heat sinks are provided for their cooling.
Safety measures at work
Main danger when working with home-made machine. danger of getting burnt by heated elements of the machine and molten metal. Lamp circuit includes elements with high voltage, therefore it must be placed in a closed housing, avoiding accidental contact with the elements. Electromagnetic field can affect objects outside the equipment. Therefore, before your work it is better to wear clothes without metal elements, remove sophisticated devices from operating zone: phones, digital cameras.
It is not recommended for people with implanted pacemakers to use the unit!
The furnace for melting metals at home can also be used for rapid heating of metal elements, such as when tinning or molding them. The performance of these units can be adjusted to the specific application by changing the inductor parameters and the generator output. thus maximizing their effectiveness.
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How an induction furnace is built. generator, inductor and crucible
In factory shops you can find channel induction furnaces for melting of non-ferrous and ferrous metals. These units have a very high power, given by the inner magnetic circuit, which increases the density of the electromagnetic field and the temperature in the furnace crucible.
Channel-type induction furnaces for melting non-ferrous and ferrous metals are manufactured on an industrial scale
However, channel designs consume large amounts of energy and take up a lot of space, so in homes and small workshops a unit without a magnetic wire is used. crucible furnace for melting non-ferrous/ferrous metal. Such a design can be assembled even with your own hands, because the crucible unit consists of three main assemblies
A generator that produces alternating current at high frequencies that are necessary to increase the density of the electromagnetic field in the crucible. over, if the diameter of the crucible can be matched to the wavelength of the alternating current frequency, this design will allow to transform up to 75 percent of the electricity consumed by the unit into thermal energy.Inductor. a copper spiral, created on the basis of accurate miscalculation not only of the diameter and number of turns, but also the geometry of the wire used in the process. The inductor circuit must be tuned to amplify the power as a result of resonance with the alternator, or more accurately, with the frequency of the current supply.The crucible. a refractory container in which all melting takes place, initiated by the emergence of eddy currents in the structure of the metal. In this case, the diameter of the crucible and other dimensions of this container are determined strictly by the characteristics of the generator and inductor.
Any radio amateur can assemble such an oven. For this he needs to find the right diagram and stock up on materials and parts. A list of all of these you can find below.
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Instructions for making an induction heater
To carry out the conversion of welding equipment into an induction furnace, you need to prepare consumables and tools. It is also important to prepare drawings and follow the assembly instructions.
A simple product based on a welding inverter
To make a simple but effective heater, you can use a welding inverter. The manufacturing process is simple enough:
- To begin with, you need to take a thick-walled plastic tube.
- At the end of the pipe it is worth to install the distribution and 2 valves, and inside to fill in pieces of steel wire of small diameter and size (5 mm).
- Fasten the upper valve.
- Make 90 turns of copper wire to assemble the inductor.
A welding machine is used as a generator and a tube of wire plays the role of heater. The apparatus is set in alternating current mode with increased frequency.
To make the system work properly, it remains to connect the copper wire to the plus welding value and evaluate the performance of the construction.
In the process of heating, a magnetic field is emitted and the wire is heated by eddy currents. This causes the liquid to boil.
Experimental model of heater with power of 1600 W
To assemble the 1.6 kW experimental equipment it will be necessary to prepare a metal pipe with thick walls. Since the coil can heat any material without much difficulty, you can improve the heater.
The body can be made of a plastic pipe, which has a larger diameter than the heating element. Optimal product length is 1 m and inner cross-section 50-80 mm.
To connect the heater to the equipment, you will need to fix the adapters at the top and bottom of the case. The lower section is closed with a grid, and then a filler of small metal particles is placed inside the enclosure.
The length of the sections can be adjusted individually without much restriction. In this case, the higher the magnetic resistance value of steel, the faster will be the heating.
A copper wire with 1-1.5 mm insulation is suitable for the winding. The use of a thicker wire is not justified, as this will make it more difficult to arrange the coils tightly.
Furnace for heating metal
Because of increased fire safety, the induction method is used in metallurgy. To assemble a heater for processing metal workpieces you can use improvised means. The work to be done will require preparation:
- 12-volt battery.
- Copper winding wire.
- Film capacitors.
- Transistors and diodes.
- PC power supply rings.
The subsequent assembly is done according to these instructions:
- The transistors are placed on the heat sinks. During use, the device heats up a lot, so it is better to prepare large heat sinks.
- Chokes are made. To assemble them, copper wire and PC power supply rings are used. It is important to make sure that the distances between the coils remain identical in each piece.
- The capacitor battery is assembled. The capacity of the power cell should be 4.7 μF.
- The winding is made. The diameter of the copper wire should be 2 mm. You need 8 windings to fit all the parts you want to work with in the internal space.
In the last step, the battery is connected. The current is adjusted during construction of the furnace. It is enough to change the number of coils.
If frequent and intensive use of the equipment is planned, it is better to prepare a power supply of higher power.
In addition, a system of heat extraction and ventilation should be provided, t.к. During operation, the furnace gets very hot.
Using such a unit in a private home will allow you to organize an uninterrupted supply of DHW or space heating. The system consumes a lot of electrical energy, but has a simple circuit of assembly and lack of complexity in maintenance. The upcoming assembly begins with preparation:
- welding inverter.
- Thermal insulator (claydite will do).
- Copper and steel wire.
- A piece of plastic pipe with thick walls.
- Tubing with different diameters.
The first step begins with the construction of the boiler. It can be constructed from 2 tubes of different cross sections, which are inserted into each other with a gap of 20-25 mm.
Next, the ends of the rings are welded and connected to the general heating system. Outlet and inlet pipes are welded into the outer wall.
Then the winding is made, which exactly repeats the shape of the boiler. Altogether we need to make 35-40 turns, observing the equal distance between the coils.
At the last stage the protective body is assembled, which is made of dielectric material, and the inverter apparatus and the heating medium are connected.
Construction of the crucible furnace
Inside is the melting crucible with a drainage tube (“collar”). On the outer sides of the structure, there is an inductor in vertical position. Then comes the layer of thermal insulation, and on top there is a cover. On one of the outer sides there may be a current and cooling water supply. At the bottom there is a device to signal the wear of the crucible.
The melting crucible is one of the most important components of the unit, it determines its operational reliability to a great extent. So the crucible and the other materials used have very strict requirements.
Assembly of the inductor
The heating element for the crucible shoulder at home is usually the inductor. It has a cylindrical shape with a cavity inside. In this cavity, a homemade crucible with metal chips is placed. The inductor is made of refractory material, with a wire winding inside, most often made of copper wire. With the help of a special generator this winding receives current, which creates an electromagnetic field. Which, in turn, creates a eddy current in the crucible and in the metal placed in it. They melt the chips. The inductor itself is assembled from 4 electron tubes in parallel connection. Such an inductor can be plugged into an ordinary wall socket.
There is another option of assembling the inductor with your own hands from an electromagnetic core and two layers of winding. The first layer. 10 turns of copper wire with a thickness of 4 mm, and the second. a single coil, the material for which is a metal plate with a cross section of 155 millimeters. The electromagnetic core is U-shaped and is a set of steel plates. Around the plates is made the first winding, which is placed in an insulated case, the secondary winding connects the core and the metal bars, between which there should be a distance equal to the size of the crucible. All this construction fits into the furnace housing.
So, you get a furnace, in which the inductor is located. Wires go from the inductor to the socket. The crucible is placed in this furnace in such a way that it closes the bars with itself. If it is placed correctly, you will hear a humming sound indicating that voltage is present and melting has begun. If there is no sound, the crucible must be moved using the handle until the circuit is closed.
Equipment of the cooling system
Industrial units for melting metal have special cooling systems using antifreeze or water. To equip these important settings in homemade HFI furnaces will require additional costs, so 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 if they are remote from the oven. Otherwise the metal winding and the fan parts can serve as a loop to close the eddy currents, which significantly reduces the efficiency of the equipment.
Bulb and electronic circuits also tend to heat up vigorously while the unit is in operation. Heat sinks are usually used for cooling them.
Inductors are supplied with power from industrial frequency units at 50 Hz in the factory. And from generators and converters of high, medium and low frequency (individual power sources) inductors work in the home. The most efficient way to assemble high frequency generators. Induction mini-kilns can use currents of different frequencies.
The alternator should not give a hard current spectrum. One of the most popular circuits for the assembly of induction furnaces in the home is recommended generator frequency of 27.12 MHz. Assemble one of these generators from the parts:
- 4 tetrodes (electron tubes) of high power (6p3s brand), with parallel connection;
- 1 neon extra. an indicator of the readiness of the device to work.
What is induction heating and its advantages
The method of non-contact metal heating using current flowing through the conductive materials is called induction heating.
The process uses high frequencies and large values, but to understand all the fine details, it is necessary to consider the functionality of the equipment sequentially. Of the advantages, the following should be highlighted:
- Quality of the final product.
- Traceability through automation.
- The process is energy efficient.
- Efficiency of the induction unit remains at a high level.
This method of melting became known to mankind already 200 years ago, reaching our time, it has been improved and carefully thought out by experts. Therefore, when buying equipment or assembling a furnace yourself, you can safely count on good performance indicators.
Tantalum. 16.67 g/cm³
Tenth in the ranking is a bluish-gray, very hard metal with an ultra-high melting point. Despite its hardness, it is as malleable as gold.
Tantalum is an important component in many modern technologies. In particular, it is used to manufacture capacitors that are used in computer hardware and cell phones.
Industrial smelters are equipped with a forced cooling system using water or antifreeze. Performing water cooling at home will require additional costs, comparable in price to the cost of the unit for melting metal itself.
It is possible to perform air cooling with a fan, provided that the fan is far enough away. Otherwise, the metal winding and other elements of the fan will serve as an additional loop to close the eddy currents, which will reduce the efficiency of the unit.
Elements of electronic and tube circuitry are also capable of actively heating up. Heat sinks are provided to cool them.