Muffle furnaces: principle of operation, application, factory and homemade options. Diy ceramic muffle kiln

A muffle furnace is a heating device consisting of a refractory chamber. The object is placed in a muffle and modified under the influence of high temperatures. You can make a muffle oven with your own hands using an old oven or washing machine.

Muffle furnaces are used for a wide variety of purposes:

for remelting metals;
firing ceramic products;
for leveling deformed surfaces various materials;
evaporation of moisture from the substance;
fast and efficient drying of various products.

Depending on the type of oven, the object can be heated to a temperature of 100 to 2000 degrees. Muffle furnaces most often run on gas or electricity. But you can design a device that will function from the process of burning wood or combustible substances.

The muffle is made of heat-resistant materials that do not allow combustion products to pass to the substance placed in them. In the muffle, processing can take place not only in air. There are muffle furnaces with heating of the material in a vacuum. Gases such as hydrogen, argon, helium or nitrogen can also be used instead of air.

The airtightness of the camera creates a uniform heat effect on the object. The muffle heats up for a long time, and it also requires a lot of energy.

The body of the muffle furnace can be created by yourself or you can use blanks. As a workpiece, you can use an old oven, electric oven or direct heating, refrigerator, washing machine... It is also worth considering that it is necessary to remove all plastic parts, since they are not adapted to high temperatures.

The case can be created by hand. Sheet metal is suitable for this. You should choose a material that is more than two millimeters thick. A rectangular box should be made of it using welding machine.

Sheet metal is suitable for creating the enclosure.

If you want to design a cylindrical muffle furnace, it is worth bending the metal into a radius and weld the seam.

To protect the metal from corrosion, it is advisable to cover the furnace with a special refractory paint. A special thermal insulation layer will improve the properties of the furnace. It serves to reduce heat loss, thereby increasing the heat in the chamber. For the thermal insulation layer, you can use basalt wool, as well as perlite.

Muffle production

In order to independently design a muffle furnace, first of all, it is worth making a refractory chamber. Not every material is suitable for these purposes.
A special chamber can be made of fireclay bricks. It is perfect for both rectangular and cylindrical ovens. True, it is quite difficult to lay out bricks in the form of a cylinder. To do this, you need to cut out the same trapezoid with a grinder. For a small oven, you will need about 7 bricks.

After that, it is worth connecting them together with a wire, and also check that they fit tightly. Irregularities can also be corrected with a grinder. Next, lay the bricks in a row and make several grooves for the wire, which will be a heating element in the future. It is important to make the grooves so that the wire does not touch anywhere. To do this, it is worth placing slopes on one of the bricks. The grooves should be 7-8 millimeters wide, the distance between them should be at least 2 centimeters.

Bricks are connected using heat-resistant glue. You can also use a mixture of clay, fireclay brick powder and quartz sand.

Ordinary clay is also suitable for making a muffle, since a homemade oven will not work with extreme temperatures. Clay needs preliminary processing. From cardboard or plywood, construct a small rectangle that will match in size with the intended muffle chamber. Be sure to calculate by size whether this chamber will fit freely into the furnace body.

The camera mock-up should be covered with clay a few centimeters thick on the outside. The clay should dry within 5 days. After a mandatory action is the firing of the clay structure. It is best to burn the material in a coal furnace, since a temperature of at least 700 degrees is required. If all the conditions are met, you get a fairly strong and fire-resistant chamber.

How to make a heating element?

Wire is used as a heating element. You can use nichrome or fechral. Nichrome wire can withstand up to 1100 degrees. But nichrome can burn out from the slightest contact with air. Fechral can withstand temperatures up to 1300 degrees, while the wire does not deteriorate from the air.
Minimum size wire to be used - 1 millimeter. Depending on the type of muffle chamber, there are different ways of attaching the heating element.

The heating element is fixed to the casing with clay, the distance between each turn should be about 2 millimeters. The bonding layer should also be dried for several days and fired in a charcoal oven.

A heating coil must be installed in the fireclay muffle. You can make it yourself from nichrome or fechral wire. To do this, wind the wire evenly around the cylindrical object. A pencil, thin metal bar, or welding electrode... The diameter of the spiral should be 6 mm.

It is imperative to ensure that the turns do not come into contact with each other, otherwise a short circuit will occur. The spiral must be drawn in special recesses made in fireclay bricks. It is imperative to secure the turns. This can be done with wire or with putty. You can use clay for the putty. Holes are drilled in the body through which it is necessary to bring the ends of the wire. To connect the spiral to the network, you need to use a cable.

A homemade muffle furnace can work not only from electricity, but also under the influence gas burner... Such a heating element can be purchased or made yourself.

To create a gas burner, you need metal pipe 10-15 centimeters long. The pipe diameter should not exceed a few centimeters. Should be done near the edge first through hole for supplying a gas pipe. Also, perpendicular to it, it is necessary to make several one-sided holes. They are required to ignite the device.

The gas tube is made of copper, its diameter does not exceed 0.8 centimeters. Threads are required at both ends of the tube. In the middle of the device, you need to make a small blind hole for the gas to escape. One hole must be closed with a plug, to the other lead gas bottle... When combining the elements of the device, it is imperative to install a valve between the hose and the burner, as it will protect the structure from fire.

Features of assembly of a muffle furnace

The muffle furnace must be properly assembled in order for it to last long. There are a few basic guidelines worth following:

It is definitely worth strengthening the outer part of the structure with metal inserts, since the muffle chamber is quite heavy.
The camera should fit snugly against the insulation of the main body.
If you made the case yourself, you need to make the door from a double sheet of metal, and also be sure to place a layer of insulation on it.
When used as the basis of the old oven, you can neglect the layer of insulation, since it is already provided for by the design of the oven.
For the safe operation of the muffle furnace, it is necessary to connect the heating element to a 20-25 A machine.

A self-made muffle furnace is significantly inferior to industrial devices in terms of heating temperature. It is impossible to remelt metal in it, and it is also difficult to work with glass. But a self-made unit will be quite enough to fire a ceramic product at home. The main thing is not to neglect the installation of protective elements against voltage surges or gas leaks.

A muffle furnace is a special device for heat treatment various materials. Her main feature is the presence of a special compartment, called a muffle, which protects the processed object from direct contact with fuel and combustion products. Such ovens have a wide range of applications.

Purpose of muffle furnaces

Muffle kilns for ceramic firing are used at the final stage of production. They serve to harden finished products, as well as for baking special paint into the surface of ceramic products. The processing technology is quite simple. The product prepared for processing is placed in a muffle made of special refractory materials. Further, the air inside the muffle is heated to the required temperature and maintained at this level until the end of firing. Thermal energy fed to the muffle with heating elements... Muffle furnaces for ceramics often operate from electrical network, since they do not need to heat up to the high temperatures required for metal processing. After the firing procedure, any ceramic product acquires additional hardness and strength, and the hardened color pattern will last for several years without fading or fading.

Laboratory muffle furnaces are used in jewelry manufacturing as well as in food, chemical and medical laboratories. Basic distinctive feature This type of furnace is characterized by high technical equipment, the possibility of prompt replacement of the muffle and almost ideal accuracy of setting the operating parameters. Laboratory equipment is mainly intended for conducting experiments in order to identify ways to improve the quality of a particular product. Therefore, the maximum accuracy of all indicators is imperative. Laboratory furnaces quickly warm up to the desired temperature, are equipped with a timer and provide uniform heating of the air space inside the muffle. Muffle chambers in them are subject to frequent replacement, since it is necessary to work with a variety of raw materials, which requires the use of muffles made of different materials.

Equipment design and operation

Muffle furnaces for metal processing often run on fossil fuels. Their operating temperature is much higher than in electric muffle furnaces. Metal processing involves hardening, burning, normalizing or melting. The processing process is quite costly, therefore only products intended for work in aggressive environments, parts for high-precision mechanical engineering, jewelry, spare parts for medical prostheses are subjected to it. Treated metal resists negative influences much better. environment, has improved specifications... And most importantly, during processing, it is not under the influence of gases released during the combustion of fuel.

The scheme of a muffle furnace looks quite simple. If desired, a simplified version of the device can be assembled at home. The most important part of the design is the working chamber - the muffle. To make it, you must use refractory clay or other heat-resistant material... First you need to assemble the camera the desired shape made of cardboard or plywood. Then Outer layer the resulting structure is covered with clay, and the wall thickness must be at least one centimeter. After the clay has hardened, it must be fired at 900 degrees Celsius. A standard home charcoal oven is suitable for this procedure.

After completing the procedure and cooling the workpiece, it is necessary to wrap the resulting chamber with fechral or nichrome wire, which will later serve as a heating element. On top of the wire, it is necessary to apply another layer of clay, while not forgetting to leave the ends to connect them to the electrical circuit. The firing procedure is repeated again. The body of the future furnace is made of sheet steel with a thickness of 1.5-2 centimeters. A hole is made in the finished case for the output of the contacts. Then the resulting muffle is placed inside the housing and the contacts are connected to the heating element. It is worth very carefully and carefully to carry out work on connecting the electrical circuit, since incorrect connection can cause short circuit... If there is no experience in such matters, it is better to seek help from specialists.

The empty space between the walls of the case and the inner chamber must be filled with asbestos chips. The calculation of the muffle furnace should be done in advance so that during the manufacturing process it does not face the problem of lack of materials. Also, the device can be equipped with additional devices, such as a timer or electronic thermometer for ease of use. That's all, the resulting device can be tested and put into operation. Of course, it is not suitable for operations with metal, but firing ceramics will pull without problems.

How to choose the right oven?

Manufacturers of muffle furnaces are constantly improving their products, as high competition in the market stimulates constant customer satisfaction. In order not to lose your customers and conquer new sales markets, you need to keep up with the times. Moreover, and price policy must be adequate, otherwise the level of sales will be low regardless of the quality of the product. Muffle furnaces EKPS are equipped with multistage systems for adjusting and setting operating modes.

In their manufacture, only modern environmentally friendly materials are used. The furnaces have a two-stage cycle of operation, when at the first stage heating occurs, and at the second stage, the obtained temperature is stabilized. The control unit allows you to memorize the set settings in the event of a power outage. The competitive model, the MIMP muffle furnace, also has all the listed advantages. The main struggle for the domestic market is going on between these two manufacturers. And not a single opponent manages to achieve a decisive advantage. According to user reviews, the products of both companies are at the highest level, which is why they are the leading suppliers in the industry.

Very often users purchase a thermocouple for a muffle furnace. This device is used to measure accurate temperature. Basically, it is necessary when the oven itself does not have a built-in thermometer and does not show the current temperature value. For the safe work of personnel, it will come in handy pull out drobe for a muffle furnace. This is a special element of technical furniture, inside which a working device is placed. It is necessary so that a person does not accidentally burn himself on a device that gets very hot during operation.

The internal temperature of a muffle furnace can be between 400 and 2500 degrees Celsius, so even touching the outer surface can be quite unpleasant. Of the rest additional equipment muffles made of different materials are in great demand. They are used depending on the conditions of work with a particular material.

The price of a muffle furnace depends on its size, operating parameters and functional equipment. The most simple models can be purchased for 20-25 thousand rubles. And devices with high-tech control units, a large working chamber and various operating modes will cost over 1 million rubles. With regard to the purchase of the device on the secondary market, here you can choose good model with good functionality for 100-120 thousand rubles. But it is worthwhile to understand that when buying a product from hand, no one will give a guarantee on it, and in the event of a breakdown, repairs will have to be carried out at their own expense.

The muffle furnace is designed for uniform heating of substances to different temperatures. The muffle present in it protects the heated object from direct impact combustion products.

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There are several criteria for muffle furnaces.

By heating source.
By processing mode.
According to constructive data.

The heating source for the muffle furnace can be gas or electricity.

The processing mode is:

in a normal (air) atmosphere;
in a special gas environment - hydrogen, argon, nitrogen and other gases;
at vacuum pressure.

Structurally, muffle furnaces are divided into furnaces:

top loading;
horizontal filling;
bell-type - the oven will be separated from the hearth;
tube furnaces.

In addition, there are several types of furnaces for thermal performance:

low temperature ovens: 100 - 500 degrees;
ovens with average temperature: 400 - 900 degrees;
high temperature ovens: 400 - 1400 degrees;
furnaces with a very high temperature: up to 1700 - 2000 degrees.

Note. The cost of the muffle furnace is directly proportional to the temperature regime, i.e., the higher the maximum temperature mark, the more expensive the furnace will be.

The advantages of muffle furnaces include the protection of the heated substance from fuel combustion products or vapors of heating elements and its uniform heating throughout the chamber.

In case of failure of the muffle, the design of the furnace allows you to quickly replace it, which greatly facilitates the repair.

The disadvantage is the slow heating rate (although this is not always necessary). It is impossible to produce high-speed heating modes in a muffle furnace. This is because it takes time to heat up the heating muffle. That entails another drawback - additional energy consumption for heating.

The main component of a muffle furnace is a muffle, which is usually made of ceramics. This material is versatile for the manufacture of all kinds of ovens. There are also corundum muffles, but they are used only in a chemical environment.

A heating element in the form of a wire is wound around the muffle and covered with ceramic coating.

Around the muffle there is thermal insulation material and all this is sheathed with a metal case made of a sheet of metal with a thickness of 1.5-2 mm.

Since the heating of the furnace begins around the muffle, it is not possible to reach high temperatures (above 1150 degrees). In this regard, manufacturers have developed a special fibrous material for the production of a muffle, which allows the heating elements to be placed from the inside. This makes it possible to increase the temperature limit of the muffle furnaces. But the disadvantage of the fibrous material is its fragility: under the influence of gas vapors, salts and oils from the heated material, the fiber is destroyed.

Today, high-quality Japanese heating elements are used for high-temperature muffle furnaces, which allow temperatures up to 1750 degrees in the furnace to be reached.

Furnaces fired with gaseous fuels initially have higher temperature ratings.

For a more even heating of the working chamber, some manufacturers integrate ventilation. And for the removal of combustion products, there is an exhaust mechanism that removes smoke and steam from the furnace through the pipe.

To control and regulate the temperature in the oven, an electronic thermostat is used, which is connected to a heater and a thermocouple. The thermostat allows you to control not only the temperature, but also the holding time of the product in the oven. Moreover, these indicators have a very high precision, especially in a laboratory muffle furnace, because the accuracy of the research depends on their value and the result obtained.

Application of muffle furnaces

Muffle furnace found wide use, first of all, as equipment for heat treatment of metals. But, due to its advantages, the muffle furnace (which can be bought in any region of Russia) has greatly expanded its scope, and this:

heat treatment of metals (quenching, tempering, annealing, aging);
firing of ceramic materials - the final stage of ceramic processing;
ashing - transformation into ash of a test substance without combustion for examination;
cremation;
assay analysis - a method for identifying and separating precious metals (gold, silver, platinum) from ore, alloys, finished products;
drying - the separation of moisture in the form of water or other liquid substance from materials;
sterilization of instruments in medicine (dentistry).

Heat treatment of metals can be carried out at home, in laboratory or on an industrial scale. Based on this, there is a whole the lineup muffle furnaces with different volumes of the working chamber, capacities and maximum heating temperature. For personal use, you can buy a muffle furnace for hardening knives; for research, a laboratory muffle furnace is suitable.

For heat treatment of metals and alloys, a muffle furnace must have special characteristics.

First of all, a muffle furnace for metal hardening, tempering and other things must have very good insulating characteristics. Usually they are provided with several layers: refractory bricks, fiber from ceramic material and protective cover from sheet metal... The bottom of the furnace should be equipped with special silicon carbide plates and an additional tray to protect against impacts of heating elements during loading and unloading. And most importantly, an electric muffle furnace must have special heating coils made of high-quality alloy to ensure a sufficiently high heating temperature - up to 1400 degrees.

Laboratory muffle furnace (price depends on power and design features) can be used to heat materials of different compositions.

A muffle kiln for firing ceramics is used in art and pottery workshops. In addition to firing, flasks are heated in it, glass is melted. The muffle furnace for ceramics has a temperature regime of up to 1300 degrees and is equipped with an automatic regulator that allows you to slowly heat and cool products without temperature jumps. Such a smooth transition is also necessary when clay is fired in a muffle furnace.

You can buy a muffle furnace for ceramics directly from the manufacturer, which significantly reduces its cost.

Note. The muffle kiln is often equipped with removable heating elements that can be easily replaced in the event of failure.

A muffle kiln for firing ceramics (the price depends on the size, power, loading method and equipment) can have an internal chamber volume from 1 l to 200 l and even more. The design of the furnace can be round with loading from above, chamber with loading in front, there is bell furnaces... Therefore, a muffle kiln for firing ceramics, which can be bought even for home use, available to the vast field of activity of any master.

To work with precious metals, as well as in dentistry, a small muffle furnace or even a mini muffle furnace, the volume of the working chamber of which is about two liters, is perfect.

When thinking about how much a muffle furnace costs, one should take into account the required characteristics that should be present in it, and choose good manufacturer... Russian-made muffle furnaces received good feedback among consumers and have a good pricing policy.

A wide range of models allows you to choose RF muffle furnaces different designs: horizontal and vertical muffle furnaces with the required loading arrangement, laboratory muffle furnaces (a production base is located in Samara).

The Glow muffle furnace is renowned for its quality. Such a muffle furnace (you can buy it in Moscow immediately with delivery) has received many positive reviews from leading enterprises in various directions.

A muffle furnace (you can buy different models in St. Petersburg) of the Electropribor company has also proven itself well among buyers.

The Belarusian muffle furnace is of good quality (it will not be a problem to buy it in Minsk, since there are many online stores that have such furnaces in their assortment).

Some craftsmen undertake the manufacture of a muffle furnace with their own hands, since they cannot afford a factory muffle furnace (the price of which is still not small). When making a furnace yourself, you need to pay great attention to the implementation of the muffle. For home use, the muffle can be made of refractory clay, forming a working chamber around a cardboard frame. When the clay is dry, the cardboard is removed. Only before further assembly, it is imperative to fire the clay muffle so that it hardens and acquires the required hardness. Further assembly is no different from the factory one.

But there are not so many home-made specialists, most consumers still prefer to buy a muffle furnace, the price is chosen according to their capabilities.

For the majority of people, muffle furnaces are completely useless. At the same time, stoves are necessary for those whose profession or hobby is associated with the manufacture jewelry, firing ceramics or smelting metals. Moreover, muffle furnaces are used in the creation of monocrystals, cupelling, as well as in medicine - for high temperature sterilization.

The cheapest factory models cost about 30,000 rubles, which significantly hits the pocket of home craftsmen. But if you remember school physics courses, in particular, thermodynamics, then it is quite possible to build such a structure with your own hands.

According to the design features of the furnace, there can be:

tubular;
cylindrical;
vertical arrangement;
horizontal arrangement (the simplest option).

Heat treatment can be carried out in air, vacuum or inert gas, but at home only the first option is possible.

Depending on the type of heating element muffle devices there are:

gas;
electric.

Gas appliances are cheaper to operate, but self-production prohibited by law. Electric ones are more expensive, but they have a significant advantage - the ability to accurately adjust the temperature regime.

Important! A homemade muffle furnace can be given any shape and size, made in a style that would fit the overall interior of the house.

What is required in the work

The most convenient to operate is vertical design... To make it you will need:

grinder, circles for metal;
nippers;
welding machine;
nichrome wire, ø1 mm;
steel sheet 2.5 mm thick;
basalt wool;
corners;
fireclay brick;
silicone sealant;
fire-resistant mixture;
respirator, plastic glasses.

Main structural elements

Important! A muffle furnace consumes a lot of electricity. For example, a device capable of heating up to 1000ᵒС needs about 4 kW. The electrical wiring with which the furnace will be connected to the network must withstand heavy loads. You will also need an assault rifle with a 25 A stabilizer.

Important! For this, asbestos cannot be used, since when heated it can release carcinogens.

Manufacturing of the case

From steel sheet a rectangle of appropriate dimensions is cut out, bent into a radius, and the seam is welded by means of a welding machine. The resulting cylinder is covered with fire-resistant paint and as soon as it dries, the bottom is welded to it (a circle cut from the same sheet). The bottom and walls are additionally reinforced with reinforcement. The volume of the cylinder must be calculated in such a way that thermal insulation can be placed in it.

Important! When using, for example, an oven, the bottom must also be reinforced with corners.

Do-it-yourself muffle furnace: instructions for making

Stage one. From the inside, the cylinder is laid out with basalt wool.

Stage two. Thermal insulation is being built, for which, as mentioned earlier, you only need to take fireclay brick... The procedure is as follows: seven bricks must be joined in the body to form a pipe. In the future, it will serve as a working chamber.

The bricks are laid out in a row, while marks are made on each of them, according to which they will be cut. Further, the trimming takes place directly, after which the bricks must be of such a shape that they can be connected into one hollow pipe. To simplify the procedure, the bricks can be numbered. At the end of cutting, the pipe is assembled, pulled together with a wire, and the symmetry of the shape is checked. Adjustments are made if necessary.

Important! Cutting should be done on fresh air, preferably in a ventilated place, not forgetting about the means individual protection(respirator, overalls, glasses).

Stage three. Nichrome wire is twisted into a ø6 mm spiral by winding it onto a base (used electrode, pencil, etc.). Then the brick is removed from the body and placed back in a row.

Stage four. A spiral is applied to the bricks and future grooves are marked. The correctness of the lines is measured building level... As a result, the laid spiral must lead from the bottom to the top of the pipe. Contact of the turns is not allowed, since this can cause a short circuit.

Stage five. To remove the ends of the spiral and connect them to the machine with a stabilizer, three strips cut from ceramic tiles, with made polypropylene and wire channels. These channels will greatly simplify renovation work in future.

Stage six. The finished structure is placed in a steel case. In this case, one brick is placed on the bottom of the case, previously covered with refractory glue. For the output of the ceramic channels, holes are made in the housing in the appropriate places.

Important! The spiral can be turned on only after the structure has dried, otherwise the wire will be damaged.

Stage seven. For the manufacture of the cover, all the same sheet steel is used. A circle is cut to the size of the structure, for a more reliable fixation, fireclay brick (1 pc.) Is attached to it from above. Then the handles, canopy and metal latch are welded. The edges of the lid in contact with the oven walls are covered with a layer of fire-resistant silicone. Silicone is applied only to a previously degreased surface.

Stage seven. Trial run. For complete drying of the structure, it is installed in a warm, well-ventilated place. It is forbidden to use any heating devices as this can lead to cracking of the masonry. After drying, the spirals are connected to an automatic machine with a stabilizer, the heating power and operating temperature are adjusted.

Important! To check the degree of dryness of the masonry, you need to turn on the device at full power and see if it evaporates from work surface steam.

The lid must be tightly closed when operating the oven.

Muffle furnace for ceramics

The image shows a primitive muffle kiln that can be used for firing small pottery.

To make it, you only need a clay flower pot and an electric stove. Half of the fireclay brick is placed on the tile (so that the spiral does not come into contact with the ceramics), the product is placed on it and closed with a pot. A thyristor regulator is used to regulate the power.

Even in daylight, you will notice that soon after turning on the sides of the pot will glow with a dark red light. From this moment, the firing countdown begins, from five to twelve hours, depending on what is fired. If overkill is observed, the power is slightly reduced.

Earthenware barrel oven

You can make a larger oven from a earthenware barrel.

Stage one. First, a small hole is made at the bottom of the barrel with a diamond drill to release the expanded air.

Stage two. Next, you need to make under. For this, a "foundation" of fireclay bricks is assembled on a small sheet of steel and connected with metal corners. Then, grooves for the spiral (no more than three or four) are made in the upper part of the barrel - the heating element of the required power will be laid in them.

Stage three. All that remains is to make the outer sheath of galvanized steel. It is made removable, since it will be put on only after the product is covered with a muffle (barrel). The space between the muffle and the outer shell is filled with asbestos.

The firing procedure is no different from previous version, but the temperature is controlled by a thermocouple. The walls of the keg are thick, while they light up (even without the outer shell), the pottery will already be burnt.

Safety engineering

Only persons who are familiar with the safety precautions for the operation of electrical devices should work with the muffle furnace.
You cannot start work without personal protective equipment - gloves, glasses, special clothing.
The structure can only be switched on with grounding.
Do not start work in the presence of chips, cracks and other structural defects.
The oven must always be supervised.
After switching on, do not touch the heating element (coil).

Despite the numerous advantages, muffle furnaces, especially small ones, are still not widely used among DIYers.

For a more detailed look at the design, watch the video below.

Video - Muffle furnace

If you refer to Explanatory Dictionary Dahl, you will learn that the word "muffle" means a small refractory furnace with thin walls for processing metal, ceramic, porcelain products or parts, protecting them from the effects of combustion products (soot, soot, gas).

Muffle furnace Is such a special design for heating various metals up to a certain temperature, you can buy it in a store or do it yourself.

The muffle is the main space for metal processing and an obstacle for its direct contact with fuel. The main purpose of muffle furnaces is the production of jewelry, the smelting of non-ferrous metals, the firing of ceramic objects, the smelting of various elements from wax, the firing of casting molds, etc.

Muffle furnaces are gas and electric.

They differ in several ways:

- type of construction
- type of heating
- peculiarities protective function
— temperature regime

There are muffle furnaces for moderate, medium, high and ultra-high temperatures.

In moderate heating furnaces, the temperature regime ranges from 100 to 500 degrees Celsius. In medium-temperature ovens - from 400 to 800 degrees. High temperature mode - this indicator is from 400 to 1400 gr., And ultra-high up to 2000 gr.

The type of oven heating is determined by the presence of heating elements. The number of these elements directly depends on the dimensions of the furnace.

Heaters are of two types:

- open
- closed

Open heaters at a sufficiently high speed heat up the structure to the required temperatures, they are easy to change in case of breakdown or malfunction. The main disadvantage of these elements is that they are susceptible to corrosion and the development of harmful substances during thermal incandescence.

Heaters closed type are in the muffle itself, therefore harmful substances do not adversely affect them. But their disadvantage is that the oven warms up rather slowly, and if the element breaks down, the entire heating chamber will have to be replaced.

Closed-type muffle furnace device

The main types of muffles used in stoves are ceramic, ceramic fiber and fibrous. The ceramic muffle furnace is used in a wide variety of industries. ceramics have a high level of thermal conductivity and density, which prevents damage to the muffle under various influences on it.

The use of a ceramic muffle does not provide for a high-speed processing mode due to a long heating and cooling process. Ceramic fiber combines the positive properties of ceramics and fibers: it has the same density level as ceramics, but with such a muffle, the furnace heats up faster and does not require more electrical power.

The ceramic fiber heater reacts more calmly to the harmful influence of the external environment than just a fiber heater.

Fiber muffle is used much less frequently in furnaces for the following reasons:

- requires a lot of electricity
- gives off harmful gases
- very brittle

Where are muffle furnaces used?

1. Annealing, the purpose of which is the formation of a homogeneous structure as a result of heat treatment

2. Hardening
For hardening metal in muffle furnaces, an increase in the cooling rate is used.

3. Vacation
This is the process required to give the material plasticity after the hardening process.

The firing process takes place especially often in muffle furnaces, especially when processing ceramics. If it is necessary to study the material for the presence of various impurities, the method of incineration or ashing is used. Muffle furnaces are widely used in blacksmithing, in laboratories for the determination of precious metals in ores, alloys, ingots, etc.

Ready-made muffle furnaces for home use

Muffle furnace PM-8

Scientists, laboratory assistants in various fields know the PM-8 muffle furnace with a chamber volume of 6.5 liters. The chamber of this furnace is made of heat-resistant ceramics, therefore it is very reliable and durable.

PM-8 is produced in two modifications:

- PM-8K with relay control

- PM-8M with digital control

The price for these muffle furnaces is 20 and 23 thousand rubles, respectively. In the heating mode, the power of such a furnace is about 2.4 kW, i.e. it can be used by plugging it into an ordinary room outlet. The only drawback of the PM-8 is that its door gets very hot.

The Sicron muffle furnace has about the same price as the PM-8. It is good to burn ceramics in it, but this furnace is not suitable for remelting metal.

Stove "SNOL". Such ovens are made by the most different sizes, but you are unlikely to find a price for it cheaper than 30,000 rubles.

The Shenpaz stove has gained a good reputation and feedback from gold dentists.

How to make a muffle furnace with your own hands

Given the increased demand for muffle furnaces and their high cost, many would like to build this structure on their own. It is impossible to make a muffle at home, because it is prohibited by law. But many can assemble an electric muffle stove on their own.

We assemble a furnace with heat treatment of products in air

1. Frame

For the manufacture of the body of the future stove, you can take an oven from an old gas stove or an electric oven, having previously removed all plastic elements from them. Or you can weld the body using a sheet of metal 0.2 cm thick.

2. Thermal insulation

The efficiency of your structure depends on the quality of the thermal insulation layer. For the insulating layer, refractory (chamotte) brick is best suited, which can withstand t up to 1000 degrees.

It is better to use it as the outer layer of the case. Asbestos sheets should not be used because it emits harmful substances when exposed to high temperatures.

3. As heating elements your stove will have spirals wound from nichrome wire. Their thickness must be at least 0.1 cm.

Heating in the muffle furnace chamber

What you need to have to assemble the oven

1.welding machine
2. grinder or angle grinder with cutting wheels
3.Steel sheet 0.2cm thick
4.metal corner
5.refractory brick
6.basalt wool
7.nichrome wire
8.refractory mixture
9.respirator
10.scissors for cutting metal

Stages of work on the manufacture of the stove

1. We make a metal case from iron sheets.

Using the angle grinder, cut out a strip in the shape of a rectangle required size and weld the seam. To this cylinder we weld the bottom, previously cut out of steel in the shape of a circle. The body must be of such a size that an insulating layer is located inside, plus a brick.

2. Take the basalt and lay it inside the case.

3. Now you need to join the bricks in the amount of 7 pieces in the form of a pipe - this is the future heating chamber of your stove.

First, lay out the brick in one row and make a markup, along which you will cut the brick. To make it easier to assemble the pipe, number each brick.

4. When finished cutting, assemble the brick, wrap the pipe with wire. Remember to use a respirator when cutting.

5. In the metal case, lower a brick pipe, and then a layer of thermal insulation.

6. Make wire grooves inside the brick layer.

7. From the wire you have, wind up a spiral (0.6 cm thick), for convenience, you can use, for example, a ballpoint pen.

8. We lay out the bricks in a row, mark the places for the grooves. The wire should be located from bottom to top in a spiral throughout the chamber.

7 bricks with spiral grooves

In order to stick the ends of the wire out and connect them, insert 3 pieces of ceramic tiles between two bricks, in which narrow channels for the wire have already been cut out beforehand.

When connecting spirals, consider 3 power levels:

- the contours of the spirals have a sequential inclusion
- the lower spiral is connected independently of the rest
- parallel connection of two circuits

Be sure to make grounding!

9. Further into the stove body with insulating layer we install the working chamber. In this case, do not forget to put a brick on the bottom of the case and grease it with clay. Drill a hole in the housing for the ceramic channels. Make a lid out of a sheet of steel and fix a refractory brick on it. Weld the handle and latch to this lid and degrease the surface.

Before using a self-assembled muffle furnace, it must be thoroughly dried by turning on the voltage until high level until steam is no longer emitted from the surface.