Making a muffle furnace for melting and hardening metal with your own hands. Homemade furnace for melting and hardening metal at home Melting furnace at home

For many years people have been smelting metal. Each material has its own melting point, which can only be achieved using special equipment. The first furnaces for melting metal were quite large and were installed exclusively in the workshops of large organizations. Today, a modern induction furnace can be installed in small workshops when setting up production jewelry. It is small, easy to use and highly effective.

Operating principle

Melting unit induction furnace used for heating a wide variety of metals and alloys. The classic design consists of the following elements:

1. Drain pump.
2. Water cooled inductor.
3. Frame made of of stainless steel or aluminum.
4. Contact area.
5. The hearth is made of heat-resistant concrete.
6. Support with hydraulic cylinder and bearing unit.

The operating principle is based on the creation of Foucault eddy induction currents. As a rule, when working household appliances Such currents cause failures, but in this case they are used to heat the charge to the required temperature. Almost all electronics begin to heat up during operation. This negative factor in the use of electricity is used to its full capacity.

Advantages of the device

The induction melting furnace began to be used relatively recently. The famous open-hearth furnaces are installed at production sites, blast furnaces and other types of equipment. Such a furnace for melting metal has the following advantages:

It is this last advantage that determines the spread of induction furnaces in jewelry, since even a small concentration of foreign impurities can negatively affect the result obtained.

Depending on the design features, floor-standing and tabletop induction furnaces are distinguished. Regardless of which option was chosen, there are several basic rules for installation:

The device may become very hot during operation. That is why there should be no flammable or explosive substances nearby. In addition, according to technology fire safety close should a fire shield must be installed.

Only two types of furnaces are widely used: crucible and channel. They have similar advantages and disadvantages, the differences lie only in the method of operation used:

The most popular type of induction furnace is the crucible type. This is due to their high performance and ease of operation. In addition, if necessary, such a design can be made independently.

Homemade versions are quite common. To create them you need:

1. Generator.
2. Crucible.
3. Inductor.

An experienced electrician, if necessary, can make an inductor with his own hands. This structural element is represented by a winding of copper wire. The crucible can be purchased at the store, but a lamp circuit, a self-assembled battery of transistors, or a welding inverter are used as a generator.

Using a welding inverter

An induction furnace for melting metal with your own hands can be created by using a welding inverter as a generator. This option is the most widely used since the efforts made concern only the manufacture of the inductor:

1. Thin-walled copper tube is used as the main material. The recommended diameter is 8-10 cm.
2. The tube is bent according to the desired pattern, which depends on the characteristics of the housing used.
3. There should be a distance of no more than 8 mm between the turns.
4. The inductor is placed in a textolite or graphite housing.

After creating the inductor and placing it in the housing, all that remains is to install the purchased crucible in its place.

Such a circuit is quite complex in execution, it involves the use of resistors, several diodes, transistors of various capacities, a film capacitor, copper wire with two different diameters and throttle rings. Assembly recommendations are as follows:

The created circuit is placed in a textolite or graphite case, which are dielectrics. Scheme, involving the use of transistors, quite difficult to implement. Therefore, you should undertake the manufacture of such a stove only if you have certain work skills.

Lamp stove

IN Lately stoves using lamps are being created less and less often, as they require care when handling. The circuit used is simpler compared to the case of using transistors. Assembly can be carried out in several stages:

The llamas used must be protected from mechanical impact.

Equipment cooling

When creating an induction furnace with your own hands, the biggest problem that arises is cooling. This is due to the following points:

1. During operation, not only the molten metal is heated, but also some elements of the equipment. That is why effective cooling is required for long-term operation.
2. The method based on the use of air flow is characterized by low efficiency. In addition, it is not recommended to install fans near the stove. This is due to the fact that metal elements can influence the eddy currents generated.

Typically, cooling is carried out by supplying water. Creating a water cooling circuit at home is not only difficult, but also economically unprofitable. Industrial versions of the furnace already have a built-in circuit, to which it is enough to connect cold water.

Safety precautions

When using an induction furnace, certain safety precautions must be followed. Basic recommendations:

When installing equipment, you should consider how the charge will be loaded and the molten metal will be extracted. It is recommended to set aside a separate prepared room for installing an induction furnace.

Muffle furnace for melting or quenching metal products- a device that allows home handyman do some work. A simple unit that can work on different types fuel, for self-made It is enough to have the skills to perform metalworking and electric welding work.

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Device and circuit

Device muffle furnace for metal melting consists of:

• in most cases a steel body. For home use It is better to make it from heat-resistant metal or stainless steel. But you can use structural steel. Sheet thickness 1.5-2 mm;
• layer internal thermal insulation. Used for home ovens fireclay brick or other thermal insulation material, withstanding heating temperatures up to 1000 0 - 1200 0;
• the steel body can be covered with an outer layer ceramic tiles or fire bricks;
• electric or gas heating elements. Gas-burners It is better to purchase in specialized stores. An electric oven can be equipped with homemade spirals made of nichrome or fechral. Wire thickness – 1 mm. Fechral wire is cheaper, but it is inferior to nichrome in terms of resistance to aggressive environments and the durability of the spiral;
• system of automatic or manual control of equipment operation. Having installed thermal sensors you can easily manage temperature conditions and time to maintain the set temperature.

Conclusion

Homemade or industrial ovens for hardening metal or melting it - all these structures must ensure safety and comfort in working with heating devices. It’s not difficult to make the design yourself; even a beginner can do it. The main thing is to carefully and responsibly follow all recommendations and rules for performing work.

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If you have a need for annealing metals, creating ceramics, melting non-ferrous materials, etc. precious metals, you can build yourself such a simple oven. Most of these stoves cost a lot of money; according to the author, in his region prices are in the region of $600-12,000 per stove. In our case, the oven cost only $120, not counting the temperature controller. This small oven can produce temperatures around 1100 o C.

The homemade product is easy to assemble, all the parts are not expensive, and they can also be quickly replaced if the stove malfunctions.

Some craftsmen manage to make in such ovens wedding rings, various talismans, brass knuckles and much more.

Materials and tools for homemade work:

Materials:
- bolts and nuts (8x10, 1/4 inch);
- seven fire bricks (they must be soft as they will need to be grooved, dimensions 4 1/2" x 9" x 2 1/2");
- corner for creating a frame;
- a square sheet of metal for the door (the author used aluminum);
- heating element (you can buy ready-made spirals for the oven, or wind your own from nichrome)
- heat-resistant contact screws for fastening the spiral;
- a piece of good cable (must withstand at least 10A).

From the tools:
- hand drill with a suitable attachment for cutting grooves in brick;
- wrench;
- pliers;
- hacksaw;
- drill;
- wire cutters and more.

The process of making a homemade stove:

Step one. Making grooves
First you need to decide how wide the spiral is; depending on this, the depth and width of future grooves in the bricks are determined. Next, you need to draw them on the brick with a pencil. The author’s grooves are shaped like the letter “U”; there are two grooves of this shape in total, that is, they are cut out on two bricks. On the brick that will be located at the back of the stove, you need to make two parallel grooves as in the photo. As a result, after assembling the furnace, the spiral will receive approximately a “U”-shape.

Step two. Installing the heating element
Before installing the heating element, you need to assemble the bricks, deciding on the size of the stove. Most likely, the bricks that go on the floor of the oven will have to be cut, since two such bricks will form too large a bottom. You can cut them with a grinder with a concrete disc, or even with a regular cutting disc.

Well, then you can install the spiral. Most likely, it first needs to be stretched to the desired length. If you wind the spiral yourself, then you need to calculate how long and thick the wire should be; there is a lot of information on the Internet for this.

Well, then you can lay the stove in the groove. To fix the spiral, the author uses metal brackets, for which holes will need to be made in the brick. Special attention You need to pay attention to connecting the spiral to the wire. Here special screws with ceramic washers must be used, and the screws must be longer. Otherwise, the wire insulation will either constantly burn and stink, or it will constantly burn due to the high temperature.

Our people learned to make such contacts from old car spark plugs when the ancient open-coil electric hot plates were used.

Particular attention should be paid to the choice of material from which the spiral is made. It will depend on this Maximum temperature, which the oven can produce. The spiral must withstand high temperature loads. For such purposes, the author chose a NiCr type wire. Most of such wires are designed for temperatures of about 1340 o C. If you require more high temperatures, then you can choose other types of wire that are suitable for this.

Step three. Making the stove frame
To create a frame you will need a corner; you can use steel or aluminum. Four pieces of aluminum form the legs, and two more go to the bottom to support the weight of all the bricks. You can use not two corners, but four, to create the lower support. However, this is not necessary; in the end, the structure is still tightened with bolts and nuts, these bolts hold the bricks down.

In the upper part of the stove you will need to lay two or one and a half bricks, as well as below. Well, you can see in detail how everything is assembled in the photo.

Step four. Making a door
To create a door you will need a sheet of metal; the author used aluminum. First, you need to draw a square or quadrilateral on the sheet, depending on the size and shape of the door. Next, this square needs to be circled, retreating the necessary distance for attaching the refractory material. Well, then cut out pieces in the corners, as seen in the photo.

The car used Kaowool plate as a fireproof material. It needs to be cut to the size of the previously drawn square. Well, then the slab is laid on the sheet, and the remaining edges of the sheet are folded, thereby holding the slab.

That's all, now the door needs to be hingedly attached to the stove with screws and nuts by drilling a couple of holes. As insulating material You can also use other components. You can make a latch for the door, or you can not.

Step five. We supply electricity
To connect the spiral you need to use good wire with a thick core that can withstand at least 10A. Among other things, the oven is connected through a regulator, which will allow you to maintain the temperature in the desired state. You will also need a stove thermometer, which will help you more accurately monitor the temperature in the stove.

Metal melting 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 changes in the crystal lattice of the metal when high-frequency eddy currents pass through it. This process is based on the phenomenon of resonance, in which eddy currents have a maximum value. To cause eddy currents to flow through the molten metal, it is placed in the action area electromagnetic field inductor - coil. It can be in the shape of a spiral, figure eight or trefoil. The shape of the inductor depends on the size and shape of the heated workpiece.
The inductor coil is connected to the source alternating current. In production melting furnaces they use industrial frequency currents of 50 Hz; 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 contour limited magnetic field inductor. Therefore, heating of the conductive elements is possible both inside the coil and on its outside. Therefore, induction furnaces come in two types:
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.

The channel furnace is too large and is designed for industrial volumes of metal smelting. It is used in the smelting of cast iron, aluminum and other non-ferrous metals. The crucible furnace is quite compact; it is used by jewelers and radio amateurs; such a furnace can be assembled with your own hands and used at home.

device
A homemade furnace for melting metals has enough simple design and consists of three main blocks placed in a common body:
alternator high frequency;
inductor - a spiral winding made of copper wire or tube, made by hand;
crucible.

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

Induction furnace and its advantages:

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

A welding inverter can be used as a generator for an induction furnace for melting metal. You can also assemble a generator using the diagrams 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.

Induction furnace with transistors: diagram

There are many in various ways collect induction heater with your own hands.
To assemble the installation yourself, you will need the following parts and materials:
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 wires in enamel insulation Ø1.2 mm;
copper winding wires in enamel insulation Ø2 mm;
two rings from inductors removed from the computer power supply.

* Field-effect transistors are installed on radiators. Since the circuit gets very hot during operation, the radiators 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.
* It is necessary to make two chokes. To make them, you need copper wire with a diameter of 1.2 mm; it is wound on 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.
* Collect the above capacitors 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 according to the diagram. A 12 V, 7.2 A/h battery is used as a power source. The current 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 a heat-resistant material, for example, textolite. The power of the device can be changed by changing the number of turns of the inductor winding and their diameter.

At long work Heater elements may overheat! You can use a fan to cool them.

Induction furnace with lamps

You can assemble a more powerful induction furnace for melting metals with your own hands using electronic tubes. 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 frequency shown is 27.12 MHz.

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

Assembling the device yourself:
1. 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 messed up. The diameter of the inductor should be larger diameter placed inside the crucible by 10 mm.
2. Place the inductor 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.
3. Assemble cascades of lamps according to a circuit with capacitors and chokes. The cascades are connected in parallel.
4. Connect a neon indicator lamp - it will signal that the circuit is ready for operation. The lamp is brought out to the installation body.
5. A tuning capacitor of variable capacitance is included in the circuit; its handle is also brought out to the housing.

Induction furnace - circuit cooling

Industrial smelting plants are equipped with a forced cooling system with water or antifreeze. Performing water cooling at home will require additional expenses, comparable in price to the cost of the metal melting installation itself. Air cooling using a fan is possible, provided the fan is located far enough away. Otherwise, the metal winding and other elements of the fan will serve as an additional circuit for closing eddy currents, which will reduce the efficiency of the installation. Elements of electronic and lamp circuits can also actively heat up. To cool them, heat sinks are provided.

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

An induction 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 generator sets- this is how you can achieve their maximum efficiency.

Homemade ornamental plant, which is shown in the video, is actually a cleverly disguised smelter. This idea will be a real find for those who from time to time work with metal in order to make another craft from aluminum or other metal, but there is not enough space in the workshop or at home to have its own place for each thing.

You will find some inventions for yourself in this Chinese store.

Necessary funds.

In this project, we use equal proportions of sand and gypsum to make a simple melting pot that's powerful enough to melt scrap metal in a second, and nice to look at so you don't have to hide it. This is a mini metal smelter.

First we need large bags of sand and plaster. Both can be bought at a hardware store. We also need a 9 and a half liter metal bucket and a blanket to cover our work area with, because most likely we will get it a little dirty. A two and a half liter bucket can be used as a measuring bucket, but you will soon see that it has a more important purpose.

For our refractory lining we use the following recipe: 4.2 liters of gypsum, 4.2 liters of sand, and 3 liters of water. When the water touches the dry mixture, the countdown begins. We'll have about 15. So let's start mixing everything up. It is very important that all the dry mixture gets wet, getting rid of lumps as quickly as possible.

After a couple of minutes of stirring, the mixture should be fairly runny and roughly the same color. After making sure that there are no lumps left, we proceed to transfusion. Carefully pour the mixture into a metal bucket, being careful not to spill anything. Enough mixture to fill the bucket, leaving about 8cm at the top.

Now we can take a plastic measuring bucket and use it to form the center of the smelter. You can fill it with water to add weight, but sand or rocks will also work. When we push the bucket, the mixture rises, but does not spill out. The mixture has already begun to harden. So let's move the bucket up and down to level it out. You need to hold the bucket in this position for 2-3 minutes, during which time the plaster will harden enough for the bucket to remain in place.

It takes about one hour to fully cure, but the plaster is soft enough to trim. If you dampen a rag and gently rub it over the top, you can smooth out the plaster very nicely and give it a nice texture. Once you're done, leave everything to dry for about an hour.

Melting crucible from a fire extinguisher.

Why not turn that old fire extinguisher into a melting pot? You can tell that it is made of steel because if you put a magnet near it, it will be attracted. This does not happen with aluminum.

Having released the pressure in the cylinder, we unscrew the top valve so that we can easily and safely cut it with a hacksaw, which took less than a minute. For the crucible we will use the bottom part because it is essentially a steel container 8 cm in diameter and 13 cm high. Good size for our homemade mini smelter.

By this time the plaster should be well hardened. Let's pour out the water. Next, use a pair of tongs or something similar to gently pull one side of the bucket toward the center. Now, if you grab it with both hands and twist it a little, the bucket will come loose and be pulled out easily.

We got amazing smooth surface, which makes our homemade smelter look surprisingly professional.

Air supply hole.

All we need is a hole for the air supply and a cover. Let's take care of them. The three and a half inch hole saw attachment works great for this tube. By placing the center of the bit on the top line of the bucket, you can begin to carefully cut through the metal. When we go through the metal, we need to tilt the tool down about 30 cm, which is easy because the plaster has not yet fully hardened and cuts like butter. Now we have a hole that the blower tube fits into perfectly. It will be placed a few centimeters from the bottom.

Blower.

Now, if the crucible fails and the molten metal pours out, in the smelter the metal remains inside and does not flow out through the tube. A leaf blower is very easy to make. First you need to take a 3 cm tube, it will be located next to the hot coals.

You will also need a 3 cm PVC pipe. As you can see, the threaded coupling from one end is screwed onto a metal tube, and the adapter from the other end is simply screwed onto a PVC tube.

Lid.

Let's go even further. Let's make a lid that will help maintain the temperature. We need a pair of 10 cm U-bolts. Place them vertically in a wide bucket filled with half the initial volume of our mixture. After an hour, the plaster will harden and can be easily removed from the bucket. And now the lid for the melting pot is ready.

Pressure relief hole.

You need to make a hole to relieve pressure. it can be done before hardening, but you can drill it with a drill with an 8-centimeter attachment. Once the hole is made, you will have a lid that looks like a huge donut. This design allows you to relieve pressure and melt the metal without even removing the lid.

Conclusion.

If you light a fire, you will see that the inside becomes so hot that the soda can melts in a second and the crucible fills with liquid aluminum. With a mini-smelter like this, we can melt aluminum in our backyard and cast anything we can think of.

Best of all, when you're not smelting scrap, the smelter doesn't take up space or be noticeable. You can insert a potted plant inside and instantly turn it into a piece of decor. This pot-turned smelter is more than it seems. Only make your smelter sustainable, this is extremely important for safety reasons.

By the way, you can try using the melting furnace as forge or even like a barbecue, since it runs on coal, after all.

Now you know how to available materials make a mini smelter that's powerful enough to melt metal in seconds, but nice enough to look at that you don't have to hide it. Translated and voiced by the Science and Technology channel.

Another publication contains more useful information.