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Melting furnaces. Induction furnaces for melting metal Homemade mini electric arc furnaces for melting steel

Crucible is a vessel for melting metal. As a rule, conversion metal is melted in crucibles, i.e. already brought to the required degree of quality for casting into a mold or refining (deep purification from impurities). The general line of development of large-scale metallurgy is to reduce the number of processing steps, up to the release of conditioned metal directly from the melting furnace, but in industry crucible melting still retains significant importance, and in handicrafts and jewelry it dominates.

The crucible is not just a fairly heat-resistant vessel. His chemical composition and the design must correspond to the type of metal being melted and the melting mode. This article describes how to make a crucible with your own hands and what conditions it must satisfy for use at home or in a small workshop. For beginner metallurgists, you will first have to touch on the metal smelting process itself, because... The requirements for the crucible are determined mainly by its conditions.

A little about melting

In a deep vacuum, the high-purity metal being melted can be heated exactly to the melting temperature or slightly higher, and kept at it for some time so that tiny, literally a few atoms, crystallite remains melt. Then the metal can be allowed to cool slightly below its melting point - it will remain liquid, like a supersaturated solution without a seed crystal. If we now pour the metal, also in a vacuum, into a mold made of a chemically absolutely inert material, in which a seed crystal of the same metal is placed, then, observing all the subtleties of this technology, we will obtain a single-crystal casting with unique properties.

In amateur conditions, vacuum melting, alas, is not feasible. In order to properly make a crucible for melting metal yourself, you need to take into account a number of features of melting in a non-inert chemical gas environment. The melted metal, firstly, interacts with air, causing part of it to be lost to the formation of oxide, which is especially important when melting scrap precious metals: at its melting temperature (1060 degrees Celsius), even gold noticeably oxidizes. To compensate to some extent for oxidation, the crucible must provide a reducing environment for the melt or be chemically inert if the metal is melted with a clean open flame, see below.

Secondly, so that the metal in the crucible does not freeze until it is brought to the casting mold, so that the remnants of the original crystallites do not spoil the casting, and the melt acquires sufficient fluidity, the metal in the crucible is overheated. For example, the melting point of zinc is 440 degrees, and its foundry temperature is 600. Aluminum, respectively, 660 and 800. Since overheating of the metal after melting takes some time, degassing of the melt also occurs at the same time, this is the third thing.

Recovery

In metallurgy, atomic carbon C, carbon monoxide CO (carbon monoxide) and hydrogen H are used as reducing agents. The latter is most often an accidental guest, because for this purpose it is too active and is absorbed by metals without forming chemical compounds with them, in large quantities, which spoils the casting material. For example, solid platinum at room temperature can absorb up to 800 volumes of hydrogen. A platinum blank in a hydrogen atmosphere literally swells before our eyes, cracks and falls into pieces. If you take them out of the hydrogen chamber and heat them, hydrogen will be released back.

Note: in a similar way, but in smaller quantities, metals absorb/emit other gases, e.g. nitrogen. This is why degassing of the melt is required, see also below.

A noticeable proportion of hydrogen reduction occurs when heated with an open flame. gas burner, upon its contact with a less heated surface. The metal does not deteriorate - the absorbed hydrogen is released and burned later in the smelting process. But, if the crucible material is also prone to gas absorption, it may crack and burst during melting; this must be kept in mind.

CO reduction is noticeable if the metal in the crucible is melted by the open flame of a liquid (gasoline, kerosene, diesel) burner, for the same reasons. Liquid fuel it burns much slower than gas, and its afterburning zone extends several cm from the burner nozzle. Reduction with carbon monoxide is the cleanest from the point of view of the metal: it does not spoil the metal and does not produce by-products with a strong excess of the reducing agent. Therefore, CO reduction is widely used in metallurgy when smelting metal from ore, but no one has yet figured out how to make a crucible furnace (see below), in which oxidation compensation would be completely provided by CO.

Atomic carbon is a reducing agent energetic enough to compensate for oxidation. It is also not difficult to create a reducing environment in a crucible using C: it is enough to introduce free carbon in one or another allotropic modification into the composition of its material or make the entire crucible from a heat-resistant and mechanically sufficiently strong allotrope C; graphite is one of them. When reducing C, there is a danger of carburization of the melt, but graphite releases very little atomic carbon when heated. If you heat the metal in a graphite crucible with a gas flame, then the excess C will immediately find a more “tasty” H for it and the danger of carburization will be reduced to zero. And for other heating methods (see below), you can select the dimensions, configuration of the crucible and the addition of graphite to its material so that there is simply no excess C under any conceivable melting mode. This is a very valuable property of graphite, keep it in mind too.

Note: the coefficient of thermal expansion of graphite TKR is negative, which significantly compensates for the thermal expansion of the crucible, increases its durability and increases its service life. Also valuable quality.

Excerpt

So, it’s clear why the melt in the crucible needs to be overheated and held. Although metal casting is a completely different topic, it still needs to be mentioned here that the melt holding time should be observed quite accurately. Chemically pure metals are almost never used in practice, for example. gold 9999 wears out very quickly; The exception is electrical copper and zinc for galvanizing, the cleaner they are, the better. Most often they use the so-called. eutectic alloys; eg steel is a eutectic of iron and carbon, and duralumin is a complex eutectic of several components. If the melt is allowed to sit, the structure of the eutectic in the casting will change and the finished product will be spoiled. The holding time is especially critical for bronze and brass: they need to be cast immediately, as soon as the play of the melt in the crucible apparently changes and becomes calmer. Remember how the engineer Telegin in A. N. Tolstoy’s “Walking Through Torment” was worried that the bronze would not wear out?

In relation to the manufacture of a homemade crucible, degassing of the melt during exposure is significant in that at this time it (the crucible) experiences significant dynamic loads from bubbles of released gases and/or the play of the melt itself. That is, make the crucible withstand a large amount of thermal deformation and, if recovery is required, a small amount. Its material must also be viscous enough to withstand shock waves from bursting bubbles and shocks from melt jets. It is this circumstance that explains the low durability and reliability of homemade graphite crucibles (see below).

What to make from

Melting crucibles are made (see figure below):

ceramic chemically neutral;
ceramic graphite;
graphite;
cast iron;
steel.

Their comparative characteristics are as follows:

Ceramic neutral - used for melting scrap jewelry while preserving the sample, because with indirect heating (see below), the properties of the metal do not change. You can do it yourself, but it’s a little complicated (see below) and is it worth it? A 50 g gold crucible costs up to 100 rubles in a jewelry store. Suitable for melting without any problems induction furnace(see below), because almost do not absorb the energy of the electromagnetic field (EMF). Resource – 10-30 melts.
Ceramic graphite – suitable for melting any metal; at home up to 1.5-2 kg at a time. To use an induction furnace, its power for the same amount of metal will have to be increased by 1.5-2 times due to the absorption of EMF by conductive graphite. You can do it yourself, see below. Resource – up to 50 or more melts.
Graphite - suitable for melting old, oxidized scrap non-ferrous and precious metals, because create a strong restorative environment. Melting silver with an open gas flame in a graphite crucible makes it possible to almost completely restore the original weight of the oxidized metal. You can’t do it yourself, see below. Resource – more than 100 melts.
Cast iron - used mainly for melting red copper into oxygen-free copper, because actively absorb oxygen. The resource is up to 30 melts, and then the amorphous carbon leaves the cast iron and the crucible degrades.
Steel - a homemade cheap option for melting small quantities of aluminum and magnesium alloys and other chemically inert metals in the melt. Can be used for melting small amounts of lead into fishing weights, etc.

Note: graphite, cast iron and steel crucibles for use in induction furnaces (see below) are completely unsuitable, because completely absorb EMF energy.

About graphite crucibles

Graphite crucibles are made either turned from massive natural graphite (expensive), or sintered at high temperatures from graphite powder (cheaper, but still not very cheap). Hobbyists often try to make “graphite” crucibles from ground graphite with a kaolin binder, etc., but what they end up with is not graphite, but overly graphitized ceramic crucibles - fragile, withstanding no more than 10 melts and spoiling the metal due to excessive release of atomic carbon by finely dispersed graphite . A more or less rational way to use ground graphite in amateur crucible melting is to make a tabletop mini crucible furnace from it for ceramic neutral crucibles, see fig.

Cold welding for assembling this furnace should be used at a temperature of at least 800 degrees - the cheeks, which conduct electricity well, do not heat up above 400 during one melt. Graphite powder will not heat up much more without a crucible, but when the crucible is pressed into it, it will be hot spot over 1000 degrees due to compaction of the powder under the crucible.

If gold is melting, then after the melting is completed and the furnace has cooled, the graphite powder is poured out and shaken, because it gets baked. To melt silver and cupronickel, the powder is removed and shaken after 3-5 melts, so the furnace heats up faster. In any case, to maintain a reducing environment, the furnace is covered with a mica lid during melting.

Heating Methods

If you need to melt more than 150-200 g of metal at a time, then you will need to build a crucible furnace next to the crucible, otherwise it will be very difficult to achieve homogeneity of the melt and high quality casting. The exception is low-melting and easily recoverable lead: up to 20-30 kg of it can be melted at a time at home. A relative exception is zinc for hot galvanizing; its melt in a crucible without a furnace can be up to 2-2.5 kg, but borax must be sprinkled on top of it so that the surface of the melt is completely covered with its fluidized layer. Steel fasteners are thrown into the melt through a layer of borax.

The optimal method in all respects for heating the crucible in a furnace is with gas, pos. 1 in Fig., but a gas crucible furnace is a rather complex structure, although it can easily be made independently. The most suitable crucible for a gas furnace is a graphite ceramic crucible, because its material has fairly high thermal conductivity. If there are particularly high requirements for metal purity, it is better to use a neutral ceramic crucible. When lower for fusible metals - cast iron, as it conducts heat better and thereby saves fuel. Graphite crucibles are placed in a gas furnace only if strong reduction of old oxidized metal is required, and the danger of carburization is insignificant, for example, when melting silver extracted from the earth for refining

For low-melting metals, the electric crucible furnace, pos. 2; it may be the so-called ohmic (with heating by a nichrome spiral) or induction, with heating from an electromagnetic oscillation generator, see below. Only ceramic neutral or, to a limited extent, graphite crucibles are suitable for induction furnaces.

If the crucible contains more than 2-2.5 kg of metal, then according to safety rules the crucible furnace must be made tiltable (item 3), because and 1 kg of melt spilled on the floor is already a big disaster. On the contrary, it is preferable to heat metal in small jewelry crucibles without a furnace, directly with the flame of a burner, pos. 4. In this case, the crucible is held throughout the melting process with a special spring grip, pos. 5 and 6.

Note: silver and its alloys, as well as lead for sinkers, can be melted at home in quantities of up to 15-20 g, using instead of a crucible... a food-grade stainless steel spoon, see fig. on right. For safety, then you need to make gaskets for the jaws of the vice with longitudinal cuts under the handle of the spoon. The flame is exclusively gas; gasoline can burn a spoon.

Electric heating

Ohmic crucible furnaces are mainly used for smelting lead or tin. For more refractory metals, they turn out to be uneconomical, but up to 20 kg of lead can be melted at a time in a home crucible electric furnace; how to make your own electric crucible for melting lead, see for example. video:

Video: electric crucible for melting lead

Melting aluminum in a crucible turns out to be more profitable by induction due to its high electrical conductivity, but this trick no longer works with copper - its temperature and latent heat of fusion are much higher. In the induction melting method, the metal is heated by Foucault eddy currents, for which the crucible with it is placed in an EMF coil made of thick copper wire, powered alternating current from an electromagnetic oscillation generator. How to make a generator with your own hands for inductively heating small amounts of metal, for example, for trinkets, is described in other materials, or, for example, see next. video guide.

Video: DIY induction heating

With an increase in the amount of melted metal, not only does the required power of the generator increase, but its optimal frequency also decreases, this affects the so-called. surface effect (skin effect) in metal. If 100-200 g of aluminum can be melted into EMF from any homemade generator for, then installing 1.5-2 kg of duralumin or magnesium alloy is already a solid structure, see fig. on right. If you intend to work with aluminum, then think carefully - is it worth building something like this? Wouldn't it be easier to use a mini gas furnace for melting small quantities? aluminum alloys, see eg. video clip

Video: mini furnace for melting aluminum

Making crucibles

Now it's time to make your own melting crucible. From the above it is clear that it makes sense to make crucibles with your own hands:

Steel;
Ceramic neutral;
Ceramic graphite.

There is nothing special to say about steel crucibles - they are just a steel vessel with a welded handle. Steel crucibles are used for melting low-melting metals; sometimes - zinc for hot galvanizing with quality up to 3+. Steel crucibles for lead, tin and zinc are only suitable for melting one specific metal, because... after 1-2 melts they themselves are covered with it from the inside.

Ceramic neutral

The composition of the mixture for forming a neutral ceramic crucible is 7 parts of fireclay clay, 1 part of finely ground fireclay (up to the fraction<1,5 мм) и 10 ст. ложек жидкого стекла (силикатного канцелярского клея) на 1 л сухой смеси. Молотый шамот в небольших количествах можно получить из кусков шамотного кирпича, растолченных в фаянсовой ступке (продаються в магазинах хозяйственных, медицинского оборудования и некоторых аптеках). Не жалко денег на крутизну – можно в сувенирном купить агатовую, они более стойкие. Если же вы собираетесь лить металл регулярно и довольно много, или делать тигли на продажу, то, возможно, лучше будет сделать для размола шамота цепную или шариковую мельницу.

Fireclay mill

Finely ground chamotte is part of the raw material for molding both neutral and graphite crucibles, and the quality and durability of the crucible largely depend on it, and crushing chamotte using artisanal methods is very labor-intensive and does not produce a completely good-quality material. The structure of a chain mill for mineral raw materials is shown in Fig. on right. Material – steel. Chains – 4; they are hung crosswise so that they sag horizontally by approx. by 1/3 of the tank diameter. An option instead of chains for 1 broken fireclay brick is 2-3 handfuls of balls from the bearing. New store-bought chains will cost more than chains, but old ones from broken bearings are quite suitable. Any drive: manual, electric. Both chain and ball mills are capable of grinding fireclay into dust like cement; To obtain certain fractions, the mill is stopped earlier. To prevent dust from forming, the mouth of the tank is covered with something during grinding. To grind a brick, simply drop it from a height onto a hard floor and load the resulting pieces into the mill.

Preparing the molding material

Mix dry clay with ground fireclay until completely homogeneous (uniform). The ideal option is to scroll 15-20 times in the same mill; if it is spherical, then you don’t have to throw balls into the tank. Unload the mixed mass and add a little water (1.5-2.5 parts), mixing by hand until it reaches the consistency: clenched in a fist, sticks together into a lump, but does not stick to the skin and is not pressed between the fingers. Add liquid glass, also stirring until completely homogeneous, this is the most labor-intensive step.

Deaeration

Just one remaining air bubble in the ceramic crucible mixture can cause the crucible to burst due to heating. Therefore, you need to knock the air out of the mass. To do this, lay a clean film on the hard floor; newspaper, as some manuals advise, is not necessary - the mass will accumulate from paper fibers.

To knock out the air, the entire lump of mass is thrown forcefully onto the floor many times. Practically - after the bubbles have stopped jumping out of the flopping mass, at least 10 more times.

Storage

For storage, the beaten mass is placed in a glass container with a hermetically sealed lid. In plastic, and especially when wrapped in several layers of film, the mass dries out in a few weeks and cannot be restored, but in glass in a cool place it is stored for more than six months.

Usage

Crucibles from the resulting mass are simply sculpted by hand or molded in a destructible plaster mold or in a collapsible one, as described below. The molded crucible is dried, and, which is absolutely necessary for this mass, after drying it is annealed in a muffle furnace for an hour or two at a temperature of 800 degrees. It is at this temperature that the liquid glass will melt and firmly bind the other components. Below - the crucible will collapse during the first melting; higher – during annealing. This is a very significant drawback of this technology, because Muffle furnace equipment is not cheap or simple, although. The maximum operating temperature of the resulting crucibles is up to 1600 degrees; resource, with high-quality grinding of chamotte - up to 30 melts.

Graphite

Manufacturing technology of graphite crucibles for melting any metals, incl. black scrap, using any heating method, is well described in an article by the author A. Ramir from 2006 (see dendrite-steel.narod.ru/stat-ramir-3.htm). A. Ramir, apparently, is self-taught, but even more credit to him - his products fully correspond to good industrial designs. However, firstly, his article was rewritten many times by rewriters who clearly did not cast metal in their lives. Secondly, you can’t always get to it in a search, and for some reason the drawings are not downloaded, although they seem to be freely distributed. Thirdly, there is something to add to A. Ramir’s materials, no offense to him. One of the rules of technology is that in a good design there is always something to improve. Therefore, we will repeat and supplement the main points of this publication.

Drawings of crucibles from the mentioned article are given in Fig.:

The maximum weight of melted steel is indicated in kg; it must be recalculated for another metal. The main difficulty in this case is the manufacture of the flask - the round shell of the mold. Its inner surface is conical, otherwise the finished crucible cannot be removed after molding, so A. Ramir used turned flasks.

Meanwhile, a flask for any of these forms can be made from a piece of plastic pipe. It is secured in 3 places, at the bottom, in the middle and at the top, with screw clamps, and heated from the inside with a hairdryer. By tightening the clamps, the surface is not completely conical, but the flask will be removed from the crucible. You only need to use worm-drive clamps (see figure on the right) or their homemade analogues. Any other clamp deforms the pipe across. The flask from it will most likely come off the crucible, but it will not last long or will crack during the first melting.

The composition of the mixture used by the author is 7 volume parts of ground fireclay, 3 parts of pottery or oven clay and 1 part of ground graphite. A. Ramir also gives a recipe with 2 parts of graphite, but in terms of reducing power this is clearly too much, and the likelihood of cracking a crucible from a 7:3:1 mixture will be reduced to zero if the fireclay is crushed into dust in a mortar or ground in a mill (see above) .

It is necessary to soak the fireclay brick, as A. Ramir advises, only before crushing it using the artisanal method he described. The dry components are mixed until completely homogeneous in the specified sequence (fireclay, clay, graphite) and mixed with water with continuous stirring until the consistency is as described above. There is no need to knock the air out of this mass, because... it is de-aired during the molding process. The mixture is not stored, so it must be prepared immediately before making the crucible.

To form the inner surface of the crucible, you need to carve a block from hard wood (filled with gray in positions 1-5 of the figure), sand it and, very preferably, walk over it with leather until the surface is completely smooth. In the center of the surface of the block that forms the bottom of the crucible, drill a blind hole and insert a toothpick or, better, a round smooth plastic stick from an ear picker into it. The match that A. Ramir used is not the best option - when pulled out, it often breaks, and as a result the product is damaged.

Note: The use of any lubricants when forming a crucible is unacceptable - they will be absorbed into its material, and the crucible will burst from heating.

The mold is filled with the mixture in layers of 15 mm, and each layer is compacted with a wooden tamper. This is the most critical stage: bubbles and uneven compaction of the mixture are unacceptable. When approx. remains to the top of the flask. 12 mm, the mixture is compacted with an already turned lid with a hole for the rod in the center, pos. 2. The mixture is added in layers of 1-2 mm until the gap between the very tightly pressed lid and the upper edge of the investment box reaches 1-1.5 mm, pos. 3. If the gap is larger, part of the mixture can be taken away. Next, the lid is removed and the rod is carefully pulled out of the block using pliers, the lid is put back and the mold is turned over. A handle is attached to the bottom of the block with self-tapping screws and, carefully turning it back and forth, it is pulled out of the casting.

Note: If the rod is not inserted into the bottom of the block, it will be impossible to remove it without destroying the casting - the vacuum under the block will not work.

The formation of a crucible with a flat bottom (which is 1.2 kg) has its own peculiarities - you can’t just pull it out. Therefore, when the compacted mass rises to the flat top of the block, a circle of toilet or filter paper is placed on it.

Now the hole from the rod and minor defects in the inner surface of the crucible are sealed with the same mass. It must be completely smooth, otherwise the probability of destruction of the crucible during melting is quite high, so after correcting the defects it must be smoothed out. The best way to do this is to line it with toilet paper (item 4), insert a block (item 5), and turn it several times.

All that remains is to remove the flask. To do this, it, together with the crucible, is turned over again into the working (for the crucible) position, a round wooden block is placed and the flask is carefully pulled together, pos. 5 and 6. If the flask is plastic, then its protruding upper edge is slightly bent outward in several places with your fingers; Most likely, the flask will come off like clockwork after this.

And finally, the finished casting is dried. Equipment – kitchen stove with oven. The casting is placed upside down on a baking sheet and placed in the oven. They heat for half an hour on the lowest gas, then another half an hour on medium (the temperature according to the built-in thermometer is about 150 degrees) and another 2 hours on full. After this, turn off the fire and leave the casting in the oven to cool until tomorrow morning. Do not open the oven during the entire drying period!

Before use, the crucible must be checked for hidden cracks. To do this, hold it by the bottom with your fingertips and tap it with your nails in a circle from top to bottom. Every knock should ring. If somewhere it doesn’t ring, it’s a defect, you can’t melt with this. Annealing is not required for a crucible manufactured using this technology. It rings everywhere - you can immediately melt in it.

What for?

A reader interested in home metallurgy “for general development” may have a question: why all this trouble? Not everyone wanders around with a metal detector in the forest after the rain, not everyone is keen on smelting damask steel at home, and not everyone has in mind hundreds of centners of old electronics, from which tens of grams of gold, platinum, and palladium can be extracted.

A muffle furnace for melting or hardening metal products is a device that allows a home craftsman to perform certain work. A simple unit that can operate on different types of fuel; for self-production, it is enough to have the skills to perform plumbing and electric welding work.

Collapse

Device and circuit

The structure of a 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 of internal thermal insulation. For home stoves, fireclay brick or other heat-insulating material is used that can withstand heating temperatures up to 1000 0 - 1200 0;
the steel body can be lined with an outer layer of ceramic tiles or refractory bricks;
electric or gas heating elements. It is better to purchase gas burners 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. By installing thermal sensors, you can easily control the temperature and the time to maintain the set temperature.

Conclusion

Homemade or industrial furnaces for hardening metal or melting it - all these designs should 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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Aluminum alloys have low melting point and good workability details. And there is always a lot of aluminum scrap on the farm.

That's why aluminum is often melted at home to replace non-standard or small parts of mechanisms: a blank is cast, and then processed on a lathe. Sometimes souvenirs and small interior items are made from aluminum with their own hands.

Melting furnace structure

Homemade furnaces for melting aluminum consist of a body - metal cylinder (2), lined with refractory (clamotte with sand or concrete). Inside the mine is charcoal (8), serving as fuel. It is installed crucible (3)- a container in which the metal will melt. The crucible can be a thick tin can, a teapot or any stainless steel container.

At the bottom of the shaft (6) made air injection hole (7) through lattice base (4), which allows you to maintain combustion and regulate the temperature in the furnace.

A hair dryer or a vacuum cleaner pipe is used as a blower. Damper (5) necessary to remove excess air.

For ovens with a capacity of several tens of kilograms, you need cover (1) for quick and uniform heating of the metal. In small ovens you can do without it.

Furnace elements should not deform or melt when heated. Therefore, the use of aluminum bodies, tubes and crucibles is unacceptable. It is best to take steel or cast iron details.

Reference. Also used as fuel for smelting aluminum natural gas or electricity.

How to make a furnace for melting metal?

Creating a small unit that can melt several kilograms of aluminum scrap is not a difficult task. To lay out the stove in the garden you will need following materials:

red bricks - 20-25 pcs.;
high tin can - 1 pc.;
grill grate - 1 pc.;
drying hair dryer - 1 pc.;
piece of pipe, with a diameter suitable for the outlet of the hair dryer - 1 PC.;
roll of electrical tape;
line segment steel wire length 30-50 cm;
coal for ignition (the quantity depends on how much aluminum needs to be melted).

The bricks will appear simultaneously and body and fireproof coating oven, a tin can will act as a crucible. At the top of the can are being done two holes opposite each other, and through them the wire is threaded. It will be possible to lift and remove the crucible with the melt from the furnace. The air will be supplied from the hairdryer turned on in cold air mode. Tape or tape to the outlet of the hair dryer attach a piece of pipe- this will be the air duct.

Such simple circuit The furnace is convenient in that no tools are actually required to create it; everything is done by hand.

Important! Do not use oven elements with zinc coating, because when aluminum is melted, toxic zinc fumes will be released.

Brick well installation plan

Gives his all one row bricks in the form of a rectangular well. The internal dimensions of the hole should be approximately length and width of one brick. On one side two bricks laid out so as to form a corridor for the air duct. The width of the corridor is tube diameter for air supply.
On the laid out row grating is installed. Instead of a grill grate, you can use any metal lid or plate with holes for air supply.
Placed on the grill second row bricks, without any gap for the air duct.

Photo 1. Finished brick well for the melting furnace. The edges are reinforced with metal strips, the air duct opening is visible.

Created air duct. Tape or tape to the hairdryer a piece of pipe is wound. To ensure structural strength, the connection point wrapped in thick paper, and then connects duct tape. Electrical tape is a more elastic material compared to adhesive tape, so it is more convenient to work with. The cold air supply button is also secured with tape on the hairdryer. Ready the mechanism is brought to the bottom row bricks.
In the stove well on the grate coal is poured and melted for ignition. The hair dryer turns on, which activates the combustion process.

Advice. The air supply intensity can be adjusted by changing hair dryer operating mode, and distance between pipe and window for the air duct.

Tin is installed to the top row bricks for the wire threaded into it. Like a pot over a fire, it hangs over the grate.
After lighting the furnace and installing the crucible third row are placed two more bricks so that from a rectangular hole you get a square one. This will fix the can inside the housing and heat up the oven space faster.

After heating the jar into it scrap can be loaded for remelting. A sign that the jar is warming up is its redness.

The principle of the design and operation of such a furnace is very simple and does not cause difficulties. However, it is always worth remembering safety precautions:

work in fire-resistant gloves;
avoid water getting into the melt;
do not use materials containing toxic substances.

Two-can design

Another type of homemade furnace for melting aluminum is a design made of two large cans. One of them serves body, in which a hole is cut for air supply, and bottom of the second jars with holes serves as a divider.

A crucible is installed inside the jars.

Such a device very compact, and small volumes of metal can be melted even in a ventilated garage. However, the design is not resistant or fire resistant, and will only last a few cycles.

Possible problems and their solutions

Carelessly assembled device causes the oven to operate inefficiently and makes it dangerous to use. Here are a few points to pay attention to:

Slots and gaps in a brick building. They can be caused by chips on bricks or loose fit of refractories to each other. Gaps reduce fuel efficiency and reduce combustion intensity and temperature. Aluminum in a crucible may simply not melt.

Therefore, after laying out each row, a visual check is carried out for the presence of holes. Holes covered with a sand-clay mixture or covered with fire-resistant material.

It is recommended to use concrete mortar only in the case of a stationary unit that is not planned to be disassembled. But Asbestos sheets and chips should not be used in places where the stove is heated, because this material is a carcinogen.

Violation of the horizontal level the buildings. Misalignment reduces the stability of the structure and creates conditions for uneven distribution of coal. The result is uneven heating of the crucible and the metal in it.

Laying out each, especially the bottom row of bricks controlled by level. You can also check horizontality placing a jar of water on the grill. On a flat surface, the top edge of the water will be parallel to the edge of the can.

MELTING FURNACE is a device designed for melting a charge of ferrous or non-ferrous metal. The advantages are that the melting mass is perfectly mixed if an induction melting furnace is used for melting metal, due to the action of eddy electric currents. Do you need a melting furnace with good characteristics? ZAVODRR- transistor, thyristor furnaces for copper, cast iron, aluminum, steel for 5 - 5000 kg.

How are melting furnaces constructed?

How do smelting furnaces work? MELTING FURNACES are a good way to melt both ferrous and non-ferrous metals, such as aluminum, steel, cast iron, stainless steel, copper. Induction melting furnaces have a simple design, operate under the force of an electromagnetic field, and are capable of uniformly mixing the metal during melting. Induction furnaces have a lid and a device for draining metal into a casting ladle. The ROSINDUKTOR company offers melting furnaces of transistor or thyristor design with gearboxes and hydraulics.

The advantage of gearbox furnaces is the possibility of manual (emergency) draining of metal; hydraulics is the smooth tilt of the melting unit. Melting furnaces are supplied with one or two melting units, and an inductor is located inside each melting unit. The inductor is made in the form of a copper coil consisting of many turns; the tube can be either round or rectangular in cross-section.

The melting unit is cooled using a chiller or cooling tower. During metal melting, it is necessary to cool two circuits: the reactor (located inside the thyristor converter) and the inductor of the melting unit itself. The melting unit has two versions of the crucible: graphite and lined (made manually from a lined mixture). Graphite crucibles are used for melting non-ferrous metals; for ferrous metals, a lining is used.

Nizhny Novgorod
Chelyabinsk
Krasnoyarsk
Minsk Belarus
Chelyabinsk
Permian
Mound
Chelyabinsk
Moscow
Orenburg
Kazan
Volgograd
Chelyabinsk
Chelyabinsk
Lugansk
Ulyanovsk
Chelyabinsk
Arkhangelsk

Melting furnaces - transistorized

The transistor induction melting furnace is designed for the charge of ferrous and non-ferrous metals. It is produced on the basis of a mid-frequency induction heater, which is assembled using MOSFET transistors and IGBT modules, which allows saving on electricity up to 35%, having a high efficiency of 95%.

Transistor-based induction melting furnaces are suitable for small industrial foundries that need to melt small amounts of metal. The advantages of melting furnaces include their mobility and ease of maintenance, since they use a graphite crucible, which saves time on making the lining and drying it.

The Rosinductor company offers to buy LEGNUM induction melting furnaces (Taiwan); these furnaces are the most popular among Russian buyers. Thyristor induction melting furnaces Legnum are supplied in two modifications: hydraulics and gearbox, the main buyers are medium and large smelting plants with a capacity of 2000 tons/year.

The induction melting furnace is supplied with two melting units; they are installed on a pre-prepared foundation. The main advantages are efficiency, on average 20-30% more economical than any other analogues presented on the Russian market, reliability, modern design and affordable price. Rosinductor supplies induction melting furnaces not only to all regions of RUSSIA, but also to the countries of the former CIS. By contacting our company, be sure that the induction melting furnace you buy is guaranteed to have the best price, quality, reliability and delivery conditions.

The advantage of melting metal in melting furnaces is cost-effectiveness. This is due to the release of a large amount of heat when heating the metal, so the furnaces consume relatively little power. If we make a comparison between transistor and thyristor furnaces, then the former are 25% more economical, but their cost for the same power is noticeably higher. The most common furnaces have a melting temperature of 1650 °C; at this temperature any non-refractory charge can be melted.

During metal melting, the furnace is controlled mechanically or remotely. In both cases, the process must be managed by trained personnel with appropriate permits and approvals. The Rosinductor company performs work on setting up converters, troubleshooting and maintaining smelting equipment in working order.

When choosing a melting furnace, you need to think about the choice of crucible. This determines what metal will melt and how many melts it can withstand. On average, the crucible can withstand from 20 to 60 heats. For a long service life of the crucible, you must use high-quality and reliable materials. The melting time of metal takes no more than 50 minutes in a heated melting furnace, so a furnace of small volume and power can have high productivity.

The delivery set of melting furnaces includes the main elements: thyristor or transistor frequency converter, melting units, capacitor banks, templates, water-cooled cables, control panels, cooling systems.

Induction melting furnace 5 - 5000 kg

Induction melting crucible furnace on 5 - 5000 kg swimming trunks, in a lightweight aluminum alloy body, with TFC and tilt gear. An induction crucible furnace with a thyristor converter is designed for melting ferrous and non-ferrous metals in foundries. The furnace is used to heat molten copper, steel and cast iron. Round-the-clock operation of the furnace is possible if necessary.

Melting furnaces for aluminum

Melting furnaces for aluminum have their own characteristics, because the melting point of aluminum is 660 °C (390 kJ/kg). When choosing a furnace for aluminum, you should know that the thyristor converter should not be powerful, and the melting unit itself differs in size from the unit for steel or copper by 2-3 times. Accordingly, it is not recommended to melt other metals in it.

Aluminum alloys can be melted in furnaces with oil, gas and electric heating, in flame reverberatory furnaces, but the highest quality metal and high speed are obtained when melting in induction melting furnaces, due to the homogeneous composition of the charge, which is perfectly mixed in the induction field.

Melting furnaces for steel

Melting furnaces are heated to their maximum temperature when melting steel, 1500 - 1600 ° C and are accompanied by complex physical and chemical processes. When remelting steel, it is necessary to reduce the content of oxygen, sulfur and phosphorus, which form oxide and sulfide elements, which reduce the quality of steel.

A feature of steel melting in melting furnaces is the use of lining mixtures, in contrast to copper melting, where a graphite crucible is used. Melting furnaces mix the metal well due to the induction field, which evens out the chemical composition of the steel.

The above advantages are excellent for smelting alloy steels, with minimal losses of alloying elements: tungsten - about 2%, manganese, chromium and vanadium - 5 - 10%, silicon - 10 - 15%, taking into account the scarcity and high cost of alloying elements.

Steel melting has the following features and advantages:

The most important castings are melted using the oxidation method, because during the boiling of the metal, all non-metallic inclusions are removed and the phosphorus content is reduced. The composition of the charge is taken from scrap carbon steel or cast iron to obtain an average carbon content of 0.5%;
If you are going to melt steel with a high content of manganese, aluminum, chromium, you need to choose an acid lining, because the durability of the crucible will be twice as high;
Before starting melting, the crucible is filled with metal, but the top should not be filled tightly, this can lead to the formation of arches and, accordingly, waste of metal, since the charge will settle during melting of the lower pieces;
The steel melting time ranges from 50-70 minutes, depending on the heating of the melting unit;
Melting furnaces for steel have high productivity in the production of castings of small mass and size.

Copper, copper alloys, bronze, brass can be melted in all melting furnaces where the temperature is maintained at 1000 - 1300 °C. However, it is preferable to use induction melting furnaces, since one melt in them will not exceed 40 minutes. The copper used in Russia today is not particularly pure. Typically it contains the following impurities: iron, nickel, antimony, arsenic. Copper with an impurity content of 1% is considered pure metal.

The main important quality of the metal is its high electrical and thermal conductivity. This determines the low temperature for melting. Copper smelting temperature is 1084°C. Copper is a fairly flexible metal that is widely used in various technical industries, here are some of its features:

Copper can be melted in an open environment, in a vacuum and in a protective gas environment;
Copper is melted in a vacuum to obtain oxygen-free copper, with the ability to reduce O (Oxygenium) oxygen to almost zero 0.001%;
The main charge when producing oxygen-free copper is 99.95% cathode sheets; before loading the sheets into the furnace, they must be cut, washed and dried from the electrolyte;
The lining of the melting furnace above the metal level is made of magnesite;
To avoid oxidation, smelting is carried out using charcoal, fluxes, glass and other components.

Induction furnace for metal melting

An induction furnace for metal melting heats the metal charge with high frequency currents (HFC) in an induced electromagnetic field under the influence of eddy electric currents. Melting furnaces consume a large amount of electricity, so we offer furnaces not only with a thyristor converter, but also with an economical transistor converter. The furnace uses a lining or a graphite crucible, in both cases they are only enough for 20-40 melts. High melting point allows one metal melt to be performed in 50 minutes.

ZAVODRR- furnaces for melting metals from Russian, Asian and European manufacturers with a crucible capacity from 1 to 10,000 kg. Supply, installation, commissioning and inexpensive maintenance of furnaces.

Let's look at the features of furnaces for melting ferrous, non-ferrous and precious metals:

Aluminum smelting furnace (aluminum smelting in furnaces is carried out at a temperature of 660 °C, boiling point 2400 °C, density 2698 kg/cm³);
Furnace for smelting cast iron (cast iron smelting 1450 - 1520 °C, density 7900 kg/m³);
Copper smelting furnace (copper smelting 1083°C, boiling point 2580°C, density 8920 kg/cm³);
Furnace for gold smelting (gold smelting 1063°C, boiling point 2660°C, density 19320 kg/cm³);
Silver smelting furnaces (silver smelting 960°C, boiling point 2180°C, density 10500 kg/cm³);
Furnace for steel melting (steel melting in furnaces 1450 - 1520 °C, density 7900 kg/m³);
Iron smelting furnace (iron smelting 1539°C, boiling point 2900°C, density 7850 kg/m3);
Furnaces for melting titanium alloys (titanium melting 1680°C, boiling point 3300°C, density 4505 kg/m³);
Furnace for lead smelting (lead smelting in furnaces 327°C, boiling point 1750°C, density 1134 kg/cm³);
Brass smelting furnace (brass smelting in furnaces 880–950 °C. density 8500 kg/m³);
Bronze smelting furnaces (bronze smelting in furnaces, 930–1140 °C 8700 kg/m³).

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 jewelry production. It is small, easy to use and highly effective.

Operating principle

The melting unit of an induction furnace is used to heat a wide variety of metals and alloys. The classic design consists of the following elements:

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

The operating principle is based on the creation of Foucault eddy induction currents. As a rule, such currents cause malfunctions when operating household appliances, 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, blast furnaces and other types of equipment are installed at production sites. 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 fire safety precautions in the vicinity, 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:

Generator.
Crucible.
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:

Thin-walled copper tube is used as the main material. The recommended diameter is 8-10 cm.
The tube is bent according to the desired pattern, which depends on the characteristics of the housing used.
There should be a distance of no more than 8 mm between the turns.
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 to implement; it involves the use of resistors, several diodes, transistors of various capacities, a film capacitor, copper wire with two different diameters and inductor 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

Lately, lamp-based stoves have been created less and less frequently, as they require careful 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:

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.
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.