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If you want to melt metal and give it different shape, you will need a furnace that can reach a temperature high enough to melt the metal. You can buy a ready-made oven or make one yourself from a sealed trash can. First, cut the bucket so that it has suitable sizes, and line the inner surface with heat-resistant insulating material. Then cover the lid with insulation and fit it tightly so that it retains heat and excess pressure. Finally, install the heating element and you can melt metal!

Steps

Part 1

Furnace body

Trim using corner grinding machine steel trash can so that its height is 45 centimeters.

• Find a steel trash can that is at least 45 centimeters high and at least 40 centimeters in diameter. If the bucket is taller than 45 centimeters, place a metal cutting wheel on the angle grinder and turn it on. Carefully trim the top edge of the bucket to the desired height.
• When operating an angle grinder, wear safety glasses to protect your eyes from metal shavings.
• Be careful not to cut yourself on the sharp cut edges of the trash can.

1. If you don't have an angle grinder or want to make a smaller oven, you can use a steel bucket with a capacity of 10 liters and a height of about 30 centimeters. Drill a hole in the side wall of the trash can at a distance of 10 centimeters from the bottom. Attach to drill hole saw 2.5 centimeters in diameter and clamp it tightly. Mark the location of the hole on the side of the bucket about 10 centimeters above the bottom. Drill side wall

   • buckets through.
   • Air or other gas will flow into the oven through a side hole.

2. Line the inside of the bucket with a layer of ceramic fiber wool 5 centimeters thick. Ceramic fiber wool has thermal insulation and fire retardant properties and is well suited for homemade stoves. By using utility knife Cut a round piece of ceramic fiber wool the same diameter as the bottom of the trash can. Push this piece into the bucket and press it firmly to the bottom. After this, wrap it tightly with cotton wool. inner side side walls of the trash can.

   • Ceramic fiber wool can be purchased at a hardware store or ordered online.
   • Ceramic fiber wool may cause irritation if it comes into contact with skin. To avoid this, wear long sleeves and work gloves.

   Warning: Cutting ceramic fiber wool produces dust that can be harmful if it gets into your lungs, so be sure to wear a respirator.

   Cut out the cotton where it covers the hole in the trash can. Find the hole you made in the side of the trash can and use a utility knife to cut out the cotton in that area. To do this, run a knife along the edge of the hole. Once you have cut the entire circumference of the wool, pull it out of the hole.

   Spray the cotton wool with hardener and wait 24 hours. A hardener is a chemical compound that activates the ceramic wool particles, causing them to become harder and retain their shape. Pour the hardener into a spray bottle and apply it to the entire surface of the cotton wool. Wait at least 24 hours for the hardener to harden in air and strengthen the layer of cotton wool.

   • The hardener can be ordered online.
   • Label the bottle you used for the hardener so it doesn't get confused with other bottles.
   • Some types of ceramic wool are already treated with a hardener and begin to harden in air. Check the cotton packaging for any instructions regarding this.

3. Apply stove cement to the surface of the wool and allow it to harden completely. Stir the kiln cement with a stick to obtain a homogeneous mixture. After this, apply the cement to the surface of the wool using a paint brush with 5cm bristles. It is necessary to cover the entire surface so that no heat escapes from the oven. Wait at least 24 hours for the cement to cure before using the kiln.

   • Already diluted stove cement can be purchased at a hardware store or ordered online.
   • You can do without kiln cement, but it will help extend the life of the kiln and provide a smooth, clean surface.

   Part 2

   Thermal insulation of the cover

   1. Drill a 5cm diameter vent hole in the lid of the trash can. Take the lid to the bucket you used for the oven body. Attach a 5cm diameter hole saw to the drill and clamp it tightly. Drill a ventilation hole in the lid 7.5–10 centimeters away from the handle.

      • Use a hole saw designed for drilling metal to avoid damaging the tool.
      • Never use a lid that does not have a vent hole, otherwise the increased pressure inside the oven may cause it to explode and be destroyed.

   2. Fill in bottom part cover with a 5 cm layer of ceramic wool. Cut a round piece of ceramic fiber wool 2.5 to 5 centimeters in diameter larger than the underside of the lid. Press the cotton into the bottom of the lid until it presses against the sides and holds firmly in place. Continue adding layers of ceramic wool until it reaches 5 centimeters thick to ensure maximum heat resistance.

      • When working with ceramic wool, wear long sleeves and an N95 or better respirator to prevent irritation and itching.
      • Be sure to read the ceramic wool label and follow all recommended precautions.
      • If the ceramic wool does not stick to the bottom of the lid, you can first spray it with heat-resistant glue. Heat-resistant glue can be purchased at a hardware store or ordered online.

   3. Cut the cotton where it covers the hole in the lid. Turn the lid over with the handle facing up and locate the hole you drilled in it. Slide a utility knife along the edge of the hole and pierce the layer of cotton wool. Cut the cotton along the edge of the hole and remove the cut piece.

      • The hole in the lid should not be covered with cotton wool, otherwise the oven will not have the necessary ventilation.

      Advice: If you have trouble cutting the cotton into the hole with a utility knife, try using a serrated bread knife - it may cut through the cotton more easily.

   4. Apply hardener to the cotton wool and leave it to harden for 24 hours. Pour the hardener into a spray bottle and apply it directly to the ceramic wool at the bottom of the lid. Cover the entire surface of the wool with hardener to ensure it hardens properly. After you apply the hardener to the cotton wool, leave the cover for at least 24 hours in a well-ventilated area to allow it to cure.

      • If you don't have a spray bottle handy, you can apply the hardener using a paint brush.

   5. Apply oven cement to the entire surface of the wool for better thermal insulation. Mix the kiln cement with a stick to form a homogeneous mixture. Using a 5cm brush, apply cement to outer surface cotton wool. Smooth out the cement with a brush and leave it for at least 24 hours to harden.

      • Before applying cement, place a sheet of cardboard or napkins under the lid to avoid staining the work surface.

   Part 3

   A heating element

   1. Place a steel pipe or nozzle through the hole in the oven wall. The type of pipe depends on what you intend to use as a heat source. If you want to heat the stove with charcoal, pass a steel pipe 30 centimeters long and 2.5 centimeters in diameter through the hole. In this case, the pipe should protrude from the inner wall of the furnace by at least 3 centimeters. If you are going to use propane, place the burner inside the stove and thread the end of the valve through the side hole. Position the end of the burner inside the oven so that it points away from the center.

      • A propane burner for furnaces can be ordered online.
      • Do not use a regular steel pipe for propane as this will make it difficult to control the flame.
   2. • You can connect any propane tank to the stove, but keep in mind that smaller tanks will run out of gas faster.

   3. Preheat the oven. If you are using charcoal, fill the bottom of the oven 5–8 centimeters with briquettes and light them with a lighter. Turn the blower on minimum power for the oven to heat up. If you are using propane, open the valves on the tank and burner. Insert a lighter into the middle of the stove and light the propane. Cover the oven with a lid to prevent heat from escaping.

      • Adjust the flame intensity using the valves on the propane tank and burner.
      • Flames may come out of the vent in the lid, so be careful.
      • Typically, coal-fired stoves can reach temperatures of approximately 650°C, while propane can reach temperatures of up to 1250°C.

   4. Melt the metal in a crucible. A crucible is a metal container inside a furnace that contains molten metal. Place the metal you want to melt in the crucible and place it in the center of the furnace using heatproof tongs. Wait until the oven heats the crucible and melts the metal, then remove it with tongs to pour it into the mold.

      • Using such a furnace, you can melt low-melting metals, such as aluminum or brass.

Below is a classification of furnaces for melting aluminum in terms of their design. The figure shows an overview of melting furnaces that are used in aluminum industry.

Classification of melting furnaces for aluminum

Figure - Classification of melting furnaces for aluminum

• 1.00 – reverberatory furnace, stationary
• 1.11 – furnace with charge loading from above
• 1.12 – round oven
• 1.13 – furnace with loading well
• 1.14 – two-chamber oven
• 1.15 – oven with dry hearth
• 1.16 – high-speed melting furnace
• 1.17 – shaft furnace
• 1.21 – reverberatory furnace, tiltable
• 1.22 – tilting cylindrical furnace
• 1.23 – tilting oval oven
• 2.00 – crucible furnace
• 2.11 – gas crucible furnace
• 2.12 – electric crucible resistance furnace
• 2.21 – crucible induction furnace
• 2.22 – channel induction furnace
• 3.00 – rotary oven
• 3.10 – tilting rotary kiln

Three classes of aluminum melting furnaces

Most often, so-called reverberatory (hearth) furnaces are used in the production of secondary aluminum. This type of aluminum melting furnace (1.00) has many modifications. All these modifications, one way or another, adapt the classic reverberatory furnace to special conditions work and special charge.

Crucible furnaces (2.00) are popular, especially in small industries.

Recycled aluminum producers widely use rotary furnaces (3.00) as melting furnaces, especially for processing scrap with a high specific surface area, such as aluminum shavings, as well as highly contaminated aluminum scrap.

The family tree of smelters shown in the figure relates specifically to the production of secondary aluminum. Some aluminum smelting technologies have very limited and specialized applications.

In addition, aftermarket equipment manufacturers use different equipment depending on the purpose of their products and the type of aluminum scrap they use.

Furnaces for secondary aluminum foundry

Recycled aluminum producers are generally divided into two categories. The first category includes industries that produce mainly casting alloys for manufacturers of aluminum castings, as well as aluminum for steel deoxidation. The raw materials for these manufacturers are “old” scrap and production waste from foundries. In English they are called "refiners". These productions, in addition to introducing alloying elements to refine a given alloy, use equipment to clean the aluminum melt and remove unwanted chemical elements and impurities.

Rotary melting furnaces are used by these aluminum scrap processors.

Foundries that produce aluminum castings from recycled cast aluminum widely use crucible furnaces - gas and electric, induction and resistance, both for melting and holding aluminum, and for pouring the aluminum melt into foundry molds.

Furnaces for wrought secondary aluminum

The second category of secondary aluminum producers includes production of wrought aluminum alloys. They use clean and sorted scrap of deformable aluminum alloys as a charge. The products of these secondary aluminum producers are slabs and ingots for rolling and extrusion (pressing). They are called "remelters" in English. These include production facilities, which are divisions of plants for rolling and extruding aluminum products and which mainly process their own technological waste.

These aluminum scrap smelters and foundries mainly use reverberatory (hearth) furnaces - stationary and tilting. Various designs These furnaces meet the requirements of specific industries: in terms of energy efficiency, metal purity, productivity, etc.

The table provides an overview of the application various types furnaces in the aluminum industry. Indices of furnace types - according to the furnace classification scheme in the figure.

Table - Application of furnaces (smelting, holding, holding) in the aluminum industry

Designations: 0 – not used, 1 – used in some cases, 2 – often used, 3 – standard technology, 4 – key technology

Depending on the scale and specifics of production, aluminum alloys are melted in foundries in crucible and reverberatory furnaces operating on electricity, liquid and gaseous fuels. Electric induction furnaces are especially widespread. The structure of some furnaces is shown in Fig. 90 and 91, and specifications them - in the table. 9 and 10.
Melting crucibles are made of cast iron or graphite chamotte. To prevent dissolution, the working surface of cast iron crucibles is painted or lined (coated) with protective materials. Chalk, zinc oxide, refractory clay, talc, colloidal graphite and other substances are added to the paints. Most often, paint is used consisting of 50 parts (by weight) of washed chalk, 50 parts zinc oxide, 5 parts liquid glass, 100 hours of water. The paint is applied to heated (150-200 °C) surfaces. Melting tools are also painted with the same paints. For coating, mixtures of magnesite, asbestos and liquid glass are used. They are applied to the working surface of the crucibles in a layer 10-15 mm thick, dried and calcined at 750-800 °C. In addition to protection against dissolution, coatings significantly (2-3 times) increase the service life of cast iron crucibles.

The lining of industrial frequency induction furnaces is made from high-alumina masses (channel furnaces) or heat-resistant cement (20-25% magnesite; 15-20% liquid glass, 1.5-2.0% sodium silicofluoride; 20-25% fireclay sand; 30- 35% fireclay crushed stone), which do not interact with aluminum melts.

For the lining of reverberatory furnaces, the most rational refractory is magnesite. However, fireclay is still widely used for this purpose, as it is the most accessible and cheap material. To prevent intensive interaction of aluminum melts with the fireclay lining, it is impregnated with a flux containing 23-25% (by weight) Na3AlF6, 20-27% B2O3, and the rest NaCl. This flux is mixed with liquid clay, coated with it on the furnace lining and calcined at 900-950 °C. You can also impregnate the lining with a molten NaCl-AlF3 mixture. During the operation of the furnace, sodium chloride evaporates, and aluminum fluoride forms oxyfluorides with silica, which are not wetted by aluminum melts. Painting the lining with chalk or lime also helps prevent interaction between the metal and fireclay. In cases where the silicon impurity content in the alloy is limited, reverberatory furnaces are lined with zirconium carbide or silicon carbide.

Melting of wrought alloys is carried out in reflective and induction furnaces large capacity (7-30 t). To accelerate the melting of the charge, increase productivity, equalize the temperature and chemical composition In reverberatory furnaces, the melt is circulated using gas-dynamic pumps. IN last years The design of a continuous shaft-tank furnace has been developed, ensuring high productivity. The principal designs of reverberatory furnaces are shown in Fig. 92, and their technical characteristics are in Table 11.


To ensure maximum productivity of melting furnaces, they are installed in conjunction with a mixer (holding furnace). This allows metal to be poured in a closed stream using a siphon, providing minimal oxidation melt and its contamination with suspended non-metallic inclusions. Siphon overflow eliminates the use of buckets and ensures labor safety.

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A homemade melting furnace can be made of graphite, cement, mica or tiles. The dimensions of the furnace depend on the power supply and the transformer output voltage.

The homemade melting furnace heats up gradually, but reaches significant heat. For this design, it is necessary to install a voltage of 25 V on the electrodes. If an industrial transformer is used in the design, then the distance between the electrodes should be 160-180 mm.

The process of making a homemade melting furnace

You can make a melting furnace with your own hands. Its dimensions will be 100x65x50 mm. In this design you can melt 70-80 g of silver or other metal. Such possibilities for a homemade melting device are very good.

Materials and tools:

• brushes from a high power electric motor;
• graphite;
• electrode rods used in arc melting furnaces;
• copper wire;
• nails;
• mica;
• cement tiles;
• brick;
• metal pan;
• carbon graphite powder;
• fine conductive wire;
• transformer;
• file.

To make a melting furnace with your own hands, you can use brushes from a high-power electric motor for the electrodes. They have excellent current carrying wire.

If you cannot purchase such brushes, you can make them yourself from a piece of graphite. You can use an electrode rod, which is used in arc melting furnaces.

On the sides of this rod, you need to make 2 holes with a diameter of 5 mm, then, to add strength, carefully hammer a nail of suitable size into it. To improve contact with graphite powder, use a file to make a mesh cut on the inner surface these electrodes.

Mica is used to make the inner surface of the stove walls. It has a layered structure and therefore can be used as a good heat-insulating screen.

The outside surface of the structure must be covered with cement or asbestos tiles, which have a thickness of 6-8 mm. After installing the walls, they must be tied with copper wire.

A brick should be used as an insulating stand for the device. A metal tray is installed underneath. It should be enameled and have sides on the sides.

Then you need to make carbon graphite powder. It can be made from unnecessary rods. It is better to do the work with a file or hacksaw for metal.

When using a stove, graphite powder gradually burns out, so it needs to be topped up occasionally.

To operate the device, a step-down transformer with a voltage of 25 V is used.

In this case, the network winding of the transformer must have 620 turns copper wire, which has a diameter of 1 mm. In turn, the step-down winding should have 70 turns of copper wire. This wire must have fiberglass insulation and a rectangular cross-section measuring 4.2 x 2.8 mm.

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How to make a transformer?

If you cannot buy a transformer with a high enough power, it can be made from several similar transformers with lower power. They must be designed for the same network voltage.

For this purpose, it is necessary to connect the output windings of these transformers in parallel.

Can be made. To do this you need to prepare L-shaped metal plates having an internal section of 60x32 mm. The network winding of such a transformer is made of enameled wire with a cross-section of 1 mm. It should have 620 turns. In this case, the step-down winding is made of wire having a rectangular cross-section with dimensions of 4.2x2.8 mm. It should have 70 turns.

After installing the furnace, it is connected to the transformer using a copper wire having a thickness of 7-8 mm. The wire must have external insulation so that a short circuit does not occur during operation of the oven.

When the oven is completely ready for use, it must be warmed up well. In this case they should burn out organic matter as part of the structure. During this procedure, the room should be well ventilated.

The device will work without soot. After this, the operation of the furnace is checked. If everything works fine, then you can start operating the device.

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How is metal melted in a furnace?

Metal melting is performed as follows. Using a small spatula (in the center of the stove), you need to make a small hole in the graphite powder, put scrap metal there and bury it.

If the pieces of metal to be melted have different sizes, then first of all lay a large piece. After it melts, add small pieces.

In order to check whether the metal has already melted, you can rock the unit a little. If the powder ripples, it means the metal has melted.

After this, you need to wait until the workpiece has cooled, then turn it over to the other side and melt it again.

This procedure must be repeated several times until the metal takes the shape of a ball. In this case, it is considered that the melting of the metal was performed with high quality.

If you need to melt sawdust or metal shavings of inexpensive metals, you need to pour them into the powder well and perform normal melting.

More expensive or precious metals should be placed in a glass ampoule from under medicines and melt together with this ampoule. In this case, a film of glass is formed on the surface of the molten metal, which can be easily removed by placing it in water.

Metals that melt easily should be placed in iron containers. If it is necessary to make an alloy of various metals, then the metal that melts less readily is put into the furnace first. After it melts, add fusible. For example, to obtain an alloy of copper and tin, you must first put copper into the powder, and then tin. To obtain an alloy of copper and aluminum, first copper is smelted, and then aluminum.

IN this device You can melt metals such as tin, iron, copper, aluminum, nickel, silver, gold. After melting the metal, it is forged. It is forged on an anvil using a hammer. In this case, it is necessary to frequently heat the workpiece over a fire until red-hot, and then hammer it again. After this, the metal is placed in cold water, and then processed again with a hammer until the workpiece acquires the required dimensions.

Under no circumstances should metals such as lead, magnesium, zinc, cadmium, cupronickel be melted, since when they burn out, they form very toxic yellow smoke, which has a detrimental effect on human health. You cannot melt silver contacts from relays and other devices because they contain up to 50% cadmium.

Having built such a stove, you can melt aluminum and bronze without any problems, and if you try hard, you can even melt steel in it. The whole principle of operation of such a furnace comes down to creating an insulated housing that can withstand temperatures up to 2600 degrees Celsius.
As for the dimensions, it is not necessary to strictly observe them; the author made it for himself so that he could melt at least 2 kilograms of aluminum at a time.

The design of the oven is very simple, it consists of a container, a lid, a hole for gas supply, and also has a drain. The insulation here is designed to withstand high temperatures, and special attention is paid to the creation of the cladding, because it must withstand the temperature of the burner flame.

To create the body, you will need either sheet steel thick enough to be welded, or a piece steel pipe. Galvanized steel cannot be used for such purposes, since zinc burns and emits gases that are very harmful to health.

Materials and tools for creating a furnace:
- refractory clay;
- sawdust;
- refractory cement;
- materials for creating the furnace body, lid, etc.;
- welding;
- Bulgarian;
- corner;
- gas supply pipe and burner.

Furnace manufacturing process:

Step one. Making insulation
The author's insulation consists of several layers. One part is designed to retain heat from the oven, and the second part is located inside the oven and can withstand high temperatures from the burner (ceramics).

For such purposes, you will need fireproof clay; it can be purchased in stores specializing in creating ceramics; it is sold in powder form. When purchasing, it is important to ask what temperature this clay can withstand. You will also need sawdust; they are mixed with clay and form a single mass. When the kiln first warms up, the sawdust inside the clay burns out and air chambers form there. Thanks to these chambers, the temperature inside the oven is well maintained.

The components are measured by volume; for such purposes, you can take a coffee jar. First, a dry mixture is made at the rate of one part clay, three parts sawdust. The mixture must be mixed very carefully so that the sawdust is evenly mixed with the clay. Then you can add one part of water to the mixture and mix everything thoroughly again. The mixture should sit for at least 12 hours. During this time, the clay will absorb water well and become plastic, making it very convenient to work with.

Step two. Making the furnace cover
The oven lid is very easy to make. First, a frame is created; in appearance it resembles a motorcycle wheel. Such a frame can be made from a steel plate and a couple of steel rods. The whole thing is bent, cut, and then welded. The author makes a ventilation hole in the center of the lid; for these purposes you will need a can of coffee or other product, it is installed in the center. To prevent the jar from sticking to the clay, you can lubricate it with vegetable oil.

Well, now the frame is installed on flat surface and the insulating material is evenly placed in it. It is important here that the clay completely fills the entire mold, then the lid will be strong and will not burn out. When the clay begins to dry, you can carefully remove the jar from the center, although it is better to wait for the clay to dry completely so as not to damage the lid. It will take a week or ten days to dry.

Step three. Manufacturing the main part of the furnace
At this stage, the author fills the previously made oven frame with insulating material made from clay and sawdust. In the process of forming the inner part, you must remember to leave space for the drain, and also make a hole for the gas supply. How to do inner part ovens, there are several options. For example, you can fill the mold completely and then insert it in the center metal pipe and use it to carefully remove the core. Holes for gas supply and drainage can be made in a similar way.

You can also place a mold in the center of the oven in advance, and then fill the resulting space with insulating material. In both cases, it is important to remember to step back from the bottom so that the kiln has a floor. After shaping, you need to let the clay dry for at least one week.

Step four. Vent Covers
To completely close the oven if necessary, you can make a couple of covers like the author did. These covers are also made from an insulating compound. For molding, you can use coffee cans, canned food, etc.

Step five. External protective layer
To protect the furnace insulation from overheating, you will need to apply a protective layer to it; it must withstand high temperature. For such purposes, the author used refractory cement. Well, then everything is simple, the mixture needs to be mixed with water and then applied evenly by hand to all areas with open insulation. Of course, such cement is quite expensive, but fortunately you need very little of it.

Step six. Drying the oven
If the clay is already dry by eye, this does not mean that it is 100% moisture free. There is quite a lot of water there, but it is a serious enemy. If there is water in the clay when the oven is heating, the resulting steam will lead to the formation of cracks and so on. To completely dry the oven, the author took a number of measures. First, you need to drill a series of holes in the insulator; for these purposes you may need a concrete drill.

Next, the outside of the stove is wrapped with glass wool or other insulation, and an incandescent lamp is lowered into the center. As a result, the walls warm up well and moisture comes out of them. The bulb must be used at least 100W.

Step seven. Attach the lid and apply gas
A mixture of gas and air must enter the oven. You can make the burner yourself or buy a ready-made one.

To attach the cover you will need a corner, an axis, and a piece of pipe. The essence of the design is that, if necessary, the heavy and hot lid can be easily turned to its side. For these purposes, between the lid and top part the oven needs to maintain a gap of a couple of millimeters.

Step eight. Casting Accessories
For casting, you first need a crucible. The author made it from a piece of thick steel pipe. She will need to weld the bottom and also attach long steel handles. Everything here must be very reliable, otherwise if the handle, God forbid, comes off, contact with liquid metal very deplorable.

You will also need to make a pair of blacksmith tongs, a ladle and other accessories. It won't be difficult.