How to make a melting furnace

Device for melting furnace

Homemade furnaces for melting aluminum consist of a metal cylinder body (2), lined with refractory (chamotte with sand or concrete). Inside the crucible there is charcoal (8), which serves as fuel. The crucible (3) is the vessel in which the metal will melt. The crucible can be a thick tin, a kettle, or any stainless steel vessel.

At the bottom of the shaft (6) there is an opening for blowing air (7) through the grate base (4), which allows you to maintain combustion and regulate the temperature in the oven.

A blow dryer or a vacuum cleaner tube is used as a blower. A damper (5) is necessary to exhaust the excess air.

Furnaces with a capacity of several tens of kilograms need a cover (1) for rapid and even heating of the metal. In small ovens you can do without it.

Kiln parts must not warp or melt when heated. Therefore the use of aluminum shells, tubes, and crucibles is unacceptable. It is best to use steel or cast iron parts to build the structure.

Information:. As fuel for melting aluminum also use natural gas or electricity.

The device of muffle furnace for melting metal consists of:

  • in most cases of steel housing. For home use it is better to make it of heat-resistant metal or stainless steel. But you can use structural steel. Sheet thickness 1.5-2 mm;
  • a layer of internal heat insulation. For home furnaces, use chamotte brick or other insulating material that can withstand heating temperatures up to 1000 0 1200 0 ;
  • steel casing can be encased with an outer layer of ceramic tiles or refractory bricks;
  • electric or gas heating elements. It is best to buy gas torches in specialized stores. Electric furnaces can be equipped with homemade nichrome or fechral spirals. Wire thickness of 1 mm. Fechral wire is cheaper, but it is inferior to nichrome in terms of resistance to corrosive environments and the longevity of the coil;
  • by an automatic or manual control system. By installing thermal sensors you can easily control the temperature mode and time of maintaining the set temperature.

How it works

Heating and melting of metals in induction furnaces occur due to internal heating and lattice change of the metal when high-frequency eddy currents pass through them. This process is based on the phenomenon of resonance, at which the eddy currents have a maximum value.

To induce eddy currents through the metal to be melted, the metal is placed in the range of action of the electromagnetic field of the inductor-coil. It can 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 alternating current source. Production melting furnaces use industrial frequency currents of 50 Hz, for melting small amounts of metals in jewelry use high-frequency generators, as more efficient.

Eddy currents are closed on a loop, limited 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 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 own hands and used at home.

How to melt iron at home (10 grams)

it is necessary to look at what temperature autonomous gas burners Rothenberger develop, maybe they will do, we have them on sale in Obi. About the arc. I dabbled once, but the voltage was 12V at a current of about 10A. A drop of iron melted so that it melted into the glass, but something more massive can not be heated. too large temperature gradient will be at the edges barely red, and the electrodes will evaporate and boil. unless you build an electrolyzer and heat it with a hydrogen flame, but you need to specify the temperature. Iron? Fe? Or any other metal? Lead, tin, please. Iron, no way. Other temperatures are needed.

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Iron melts at 1539C, you can try to set the house on fire and throw a piece of iron into the heat may melt

With an acetylene-oxygen torch (used at construction sites). or build an HFI.

It is more interesting to melt iron with thermite :-)) It is done like this: You take aluminum powder (if you have “silver paint”. use it) and mix it with potassium permangonate (manganese, it is a good oxidizer) 1:1. Combustion temperature will be enough even to melt the pan. This mixture is lit with a good load of match powder or better, you can not ignite it with a match. This thing burns very powerfully, so take care about safety, do the experience outside, do not stand next to it (the column of sparks and fire will be more than a meter). Actually, when thermite is used for welding rails, for example, they mix iron oxide with aluminum, which is reduced to pure iron by melting and then flows out and welds the rails. But I understand you need to melt a certain piece of iron? Then my recipe is just right. And the New Year is coming up, you can melt the iron and make fireworks at the same time :-)))))))

Domestic uses for ovens

At home, such devices are used quite rarely, although similar technology can be found in heating systems. They can be seen in the form of microwave ovens, electric ovens, and induction stoves. In the environment of new technologies, this development has found wide application. For example, the use of eddy current in induction stoves allows a huge variety of dishes to be prepared. Since they require very little time to heat up, the burner can not be turned on if there is nothing on it. However, the use of such special and useful stoves requires special cookware.

Purpose and classification

The metal melting furnace is a furnace that has been used in blacksmithing for many years. However, the low efficiency index determined the fact that it was not used in the production of products made of the alloy in question in industry. There is the following classification:

  • By body type: open and closed. Open has a fully open top. Closed version has a closed top.
  • By place of installation: stationary and personal forge.

Closed type furnace

Open type burner

How To Make The Metal Foundry. Steel Melting Furnace

For the removal of combustion gaseous products, a special pipe is created if the work is carried out indoors. The open type has no pipe, because the combustion products go without their removal.

Assembling the furnace yourself

On the Internet and magazines there are many technologies and schematic descriptions of this process, but when choosing is worth settling on a single model, the most effective in the work, as well as affordable and easy to perform.

Homemade melting furnaces have a fairly simple design and usually consist of only three main parts, placed in a strong case. These include:

  • An element that generates an alternating current of high frequency;
  • A spiral-shaped piece created from a copper tube or thick wire, called an inductor
  • A crucible. a container in which calcination or smelting will be carried out, made of refractory material.

Of course, such equipment is not often used in the home, because not all masters need such units. But the technology found in these devices is present in appliances that many people deal with almost every day. This can include microwave ovens, electric ovens and induction stoves. All kinds of equipment can be made with one’s own hands according to the schemes, if one has the necessary knowledge and skills.

In this video you will learn what this stove consists of

Heating in such a technique is carried out thanks to induction eddy currents. Temperature increase is instantaneous, unlike other devices of similar purpose.

For example, induction stoves have an efficiency of 90%, while gas and electric stoves can not boast of this value, it is only 30-40% and 55-65%, respectively. However, HFI stoves have a disadvantage: you have to prepare a special dish to operate them.

Transistor design

There are many different schemes for assembling induction melting stoves at home. A simple and proven stove made of field-effect transistors is assembled quite easily, many craftsmen familiar with the basics of radio engineering will cope with its construction according to the scheme shown in the figure. To create a setup, you need to prepare the following materials and parts:

  • two IRFZ44V transistors;
  • copper wires (for winding) in enamel insulation, 1.2 and 2 mm thick (one piece each);
  • two rings from the chokes, you can take them off the power supply of an old computer;
  • One 470 ohm resistor for 1 watt (two 0.5 watt resistors in series can be connected);
  • two diodes UF4007 (easily replaceable with model UF4001);
  • one 250 watt film capacitor, with the capacity of 330 nF, four with 220 nF, three with 1 uF, and one with 470 nF.
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assembling according to the schematic drawing, it is also recommended to refer to the step-by-step instruction, this will save you from errors and damage elements. Creation of an induction melting furnace with your own hands is made according to the following algorithm:

  • The transistors are placed on fairly large heat sinks. The point is that circuits can get very hot during operation, so it is so important to choose the right size parts. All the transistors can also be placed on one radiator, but in this case you have to insulate them, ridding them of contact with the metal. Washers and gaskets made of plastic and rubber will help. The correct pinout of the transistors is shown on the picture.
  • Then proceed to make the chokes, they need two pieces. To do this, take a copper wire of 1.2 millimeters in diameter and wind the rings taken from the power supply with it. These elements include ferromagnetic iron in powder form, so you need to make at least 7-15 turns, leaving a small distance between them.
  • The obtained modules are assembled into one battery with a capacity of 4.6 uF, and the capacitors are connected in parallel.
  • Copper wire 2 mm thick is used for winding the inductor. It is wrapped 7-8 times around any object of cylindrical shape, its diameter must correspond to the size of the crucible. The excess wire is cut off, but quite long ends are left: they will be needed for connection to other parts.
  • Connect all the elements on the board, as shown in the picture.

We recommend that you use a 12-volt, 7.2-Ah battery as a power source. The amount of current consumption during operation will be equal to 10 A, such source is enough for about 30-50 minutes.

If necessary, you can construct a housing for the unit, for this purpose using only heat-resistant materials such as textolite. The power of the machine can be adjusted, for which it is sufficient to change the number of wire windings on the inductor and their diameter.

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

With graphite brushes

The main element of this design is assembled from graphite brushes, the space between which is filled with granite, ground to a powder state. The completed module is then connected to a step-down transformer. When working with this kind of equipment you can not fear the electric shock, because it does not feel the need to use 220 volts.

Technology for making an inductor furnace from graphite brushes

  • First collect the body, for this refractory (chamotte) brick 10 × 10 × 18 cm is placed on a tile that can withstand high temperatures. The finished box is wrapped with asbestos cardboard. To give this material the necessary shape, it is enough to moisten it with a small amount of water. The size of the base is directly related to the power of the transformer used in the design. If desired, the box can be covered with steel wire.
  • A 0.063 kW transformer, taken from a welding machine, is an excellent option for graphite stoves. If it is designed for 380 V, you can subject it to winding for safety reasons, although many experienced radio technicians believe that this procedure can be abandoned without any risk. However, it is recommended to wrap the transformer with thin aluminum, so that the finished unit will not heat up during operation.
  • At the bottom of the box, a clay pad is placed, so that the liquid metal does not flow, and then graphite brushes and granite sand are placed in the box.
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The main advantage of such devices is considered a high melting temperature, which can change the aggregate state of even palladium and platinum. The disadvantages are that the transformer heats up too quickly and the furnace area is too small to melt more than 10 grams of metal at a time. Therefore, every craftsman should understand that if the device is going to process large volumes, it is better to make a furnace of a different design.

It is not recommended to melt brass in such furnaces. This material is characterized by high m zinc, which begins to burn at high temperatures and forms a caustic, very harmful smoke to the body.

make, melting, furnace

A bulb-based appliance

A powerful smelting furnace can be assembled from electronic light bulbs. As you can see in the diagram, in order to get a high-frequency current it is necessary to connect the beam lamps in parallel. Instead of the inductor, this device uses a copper tube with a diameter of 10 mm. Also the design is equipped with a trimmer capacitor to be able to adjust the power of the furnace. To assemble it, you need to prepare:

  • Four lamps (tetrodes) L6, 6P3 or G807;
  • tuning capacitor;
  • 4 chokes of 100-1000 μH;
  • neon indicator bulb;
  • four capacitors of 0.01 μF.

To begin with, the copper tube is given a spiral shape. this will be the inductor of the device. The distance between the coils should be not less than 5 mm, and their diameter should be 8-15 cm. The ends of the coil are machined to attach it to the circuit. The thickness of the inductor should be 10 mm greater than the crucible (it is placed inside).

The finished part is placed in the housing. For its manufacture, you should use a material that provides electrical and thermal insulation of the stuffing of the device. Then, from the lamps, chokes and capacitors assemble Cascade, as shown in the figure, the latter are connected in a straight line.

Now it’s time to connect the neon indicator, which is needed for the craftsman to know when the device is ready to work. This bulb is led to the body of the furnace together with the handle of the capacitor of variable capacity.

Melting device for aluminum and copper

Smelting metals are brittle. It is important to follow the schemes for working with this type of metal.

DIY Metal Melting Furnace at Home l Homemade Metal Foundry l

So, for example, to melt copper or aluminum, the muffle furnace must heat up to 1083 Celsius, and to melt bronze 930 Celsius.

These materials have the highest melting temperatures of all fusible materials.

So, the conclusion is inescapable: to work with fusible metals, you need a furnace that heats up to 1100 degrees maximum.

Nuance! For large castings, a hearth is installed when working with fusible metals. And you can melt the metal in a bowl with a spout (crucible). This is the easiest way to shape them afterwards.

Steps in processing fusible materials

  • Hardening the pouring furnace at 600 degrees.
  • Immersion of the mold.
  • Heating the temperature up to 900 degrees.
  • Time the mold in the furnace for 120 minutes.
  • Remove the mold and cool to 500 degrees.
  • Lightly fusible material is placed in the mold.
make, melting, furnace

Insulated refractory bricks

We started with 10 insulated refractory bricks. There are several different types, so be sure to use “soft” fire bricks, such as these large white. They have better insulating properties than “hard” refractory bricks, which are smaller, sand-colored bricks.

make, melting, furnace

You can use “hard” bricks if you really want to, but since their function is mostly structural, they conduct a lot of heat, and it will take a very long time for the casting furnace to heat up to temperature, if at all, since there will be a lot of heat loss through the brick surface.

We arranged the bricks so that we had a simple crucible box, allowing us to load them from the top.

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