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- this is such a special design for heating various metals 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 production jewelry, smelting of non-ferrous metals, firing ceramics, smelting various elements from wax, firing casting molds, etc.
Muffle furnaces are gas and electric.
They differ in several ways:
- type of construction
- type of heating
- features of the 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 with a sufficiently high speed heat up the structure to 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 rather than negatively influencing 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 positive properties ceramics and fibers: has the same density level as ceramics, but with this muffle the furnace heats up faster and does not require more electrical power.
On the harmful effect external environment The ceramic fiber heater responds more quietly than the fiber heater alone.
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 be coiled 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 oven1.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 of the 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 between two bricks ceramic tiles, in which narrow channels for the wire have already been cut out in advance.
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.
The very term "muffle furnace" for most people does not mean anything. No, this is not another variation heating appliances allowing you to save on fuel. This is a device designed for firing ceramics, smelting metals, cupelling, creating single crystals, etc. In medicine, they are used to disinfect instruments.
Despite its compact size, a household unit will cost 35-48 thousand rubles, which is quite expensive for making hand-made and ceramics. Therefore, many are looking for how to make a muffle furnace with their own hands. We propose to arm yourself with a number of tools, recall the school physics course in thermodynamics and start manufacturing.
Varieties of muffle furnaces
By design features, the devices are divided into:
- tubular or cylindrical;
- horizontal or vertical.
By the type of heat treatment composition:
- air;
- vacuum;
- based on inert gas.
Only an air muffle furnace can be made at home, therefore it is about it that will be discussed in the article.
By the features of the thermoelectric heater:
- gas;
- electrical.
Of course, a gas stove will bypass in operation 3-4 times cheaper than an electric one, due to fuel economy, but such a stove, firstly, is prohibited by law to manufacture and use, and secondly, it is technically extremely difficult to make a muffle stove with your own hands using gas.
At the expense of simple materials the stove can be made in any convenient form, including one that ideally suits the interior of the room.
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Manufacturing the device
In this case, we will tell you how to make a vertical muffle furnace for firing ceramics with your own hands.
To do this, you need the following tools:
- angle grinder (grinder) and 1-2 circles;
- electric arc welding and electrodes;
- locksmith tools, including wire cutters;
- 2mm nichrome wire.
and materials:
- 2.5 mm steel sheet or used oven body;
- corner;
- fittings;
- basalt wool;
- refractory fireclay bricks;
- refractory mortar;
- silicone sealant.
Essential elements
Frame
The body is ideal as a base for a homemade muffle furnace for fusing or cupelling. electric oven or a miracle stove, since all the necessary insulation is already provided in it. All you need to do is remove or remove all plastic parts.
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If it was not possible to find such an oven, the body can be welded from a sheet previously cut into blanks. Weld all the sidewalls, clean the seams with a metal brush or grinder and cover with a primer.
The manufacture of a case from sheets, although a little more complicated, allows you to make the design that is suitable in size for a specific room.
A heating element
A key component of the device, since it is on it that the temperature in the oven and the heating rate depend. You will also need to make a thermostat for a muffle furnace with your own hands, or purchase a ready-made one. A nichrome wire will act as a heating element, the diameter of which is selected depending on the maximum temperature. The minimum and most consumable diameter is 1.5-2 mm.
Nichrome on a standard spiral can withstand 1100 degrees, but it is necessary to exclude the ingress of air, otherwise it will burn out. Fechral is best suited for a muffle furnace - its working temperature 1300 degrees, and it is "friendly" with the air.
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Any electric muffle furnace, even the smallest one, made by hand, when heated to 1000 degrees, spends about 4 kW. Check all wiring and set the auto-stabilizer to 25A before use.
Thermal insulation
The most important aspect of work, which is responsible for the integrity and efficiency of the entire structure. Inside the muffle furnace, fireclay bricks are installed on fire-resistant glue. To the size of the oven, it is cut off with a grinder. Basalt wool is used on top.
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Some forums for the manufacture of muffle furnaces recommend using asbestos for masonry. This is really a fire-resistant material, but already at a temperature of 650 degrees + it begins to release carcinogens.
Making a homemade muffle furnace
The first point can be skipped for those who use an old oven as a body.
How to make a case
Cut out a rectangle of the required size from the sheet, bent into a cylinder and weld a seam. Next, cut out a circle of the corresponding diameter from the same sheet and weld it to the cylinder. You get a semblance metal barrel, the sides and bottom of which should be reinforced with fittings and corners.
The volume of the barrel is calculated in such a way that there is enough space for both insulation (cotton wool and bricks) and for the materials to be fired.
The body can also be rectangular - the shape does not in any way affect the quality of the furnace and the efficiency of heating. In the video, you will see how to make a rectangular muffle furnace with your own hands from similar materials.
Video 1 DIY muffle furnace with a description
Thermal insulation of the oven
- Basalt (stone) wool is laid out along the perimeter of the structure.
Why is this type of mineral wool chosen? For several reasons:
- incombustibility - it is even used as a barrier to open fire. Cotton wool can withstand temperatures up to 1114 degrees, after which it begins to melt, but not burn;
- natural constituents - basalt, from which cotton wool is made, absolutely natural material, therefore, even when heated, it does not emit any harmful substances, unlike, for example, cotton wool made from slags;
- minimum thermal conductivity, which is only 0.032-0.048 W / m / K, which is even less than that of expanded polystyrene.
Cotton wool is attached to the body with special ceramic buttons
- This is followed by thermal insulation with fireclay bricks. This material is required, since it consists of 75% refractory clay and will not burst during the operation of the furnace.
Take 7 bricks, number them for convenience, make up like a pipe. Next, cut the ends with a grinder so that the pipe is as round as possible.
When the bricks are cut and assembled, wire them together and check how symmetrical the structure is.
- You make a 6 mm spiral from nichrome wire, for which you wind it on any round object of a suitable diameter, you can even use a pencil.
Please note that the oven can only be operated if the temperature is continuously monitored. Otherwise, it's just an expensive but very dangerous toy. The only one real option a sensor of such high temperatures (over 1000 degrees) is a thermocouple. You do not need to look for platinum for this, this option is quite suitable:
- iron-constantan, 53 mV / deg, thermo EMF;
- nickel-iron, 34 mV / deg., thermo EMF.
- Unscrew the bricks and cut into inside at a slight angle with a grinder, spiral furrows. Check their evenness with a level and position them so that the turns go from the very bottom to the top. It is strictly forbidden to allow contact of the turns - there will be a circuit closure. After cutting the grooves, insert the spiral and reassemble the entire structure.
- Remove the ends of the spiral and connect them to a 25 A machine.
- Now take the previously prepared steel cylinder, put fireclay bricks on the bottom of it, cut so as to completely cover the entire bottom, fill them with refractory glue. Next, place the assembled thermal structure and also fill the space between the barrel and the structure with a refractory compound.
Photo 12 The finished structure is placed in a steel case
You can turn it on only when the whole structure is completely dry. 3-5 days after production, turn on the device for full power, but do not close the lid - if evaporation begins somewhere, disconnect and leave for another day.
Cover making
- Cut a circle out of steel that is identical in diameter to the already fully assembled structure.
- On top of the glue "plant" fireclay brick - it will provide sufficient sealing.
- Weld on the sides of the handles so that it is convenient to lift and remove the lid and latch for closing.
- Cover the edge with fireproof silicone, before that the surface must be degreased (even White Spirit will do).
As a reminder, when the oven is running, it must be closed. Excessive air ingress will lead to rapid wear of the nichrome.
The simplest muffle furnace for ceramics
To make such a simple device, you only need an ordinary electric stove, a clay pot and a piece of fireclay brick.
- Place a piece of brick on the stove so that the ceramic to be fired does not touch the spiral on the tile and cover it with a pot. Adjust the power with a thermostat.
- Now you watch the pot - as soon as a red light starts to shine through its walls, you time the firing time. As a rule, it is 10-12 hours.
Safety engineering
- You can work with the stove only if there is grounding.
- It is forbidden to start work if there are chips or cracks on the body.
- It is forbidden to touch the device during operation.
- It is strictly forbidden to touch a working spiral.
- The oven requires constant supervision during operation.
Despite the relative simplicity of manufacture, such a device is not very common among home craftsmen. This is due to the high costs of electricity. Someone thinks that it is possible to make a muffle stove on wood too - well, if you can find a piece of wood with a calorific value of 14,000 kcal / kg, then yes, it will. Although it is still better to use forge- it was in such conditions that the first such oven in history was invented.
If you still have questions on how to make a muffle furnace with your own hands, watch the video instruction.
Video 2 DIY muffle furnace
A muffle furnace is primarily used for the heat treatment of a variety of things. It is used for melting, quenching and firing of metal, glass, wax and even ceramic materials. Due to the versatility of such a unit, a sufficiently wide temperature range of up to 1000ºC is provided.
If you need to have such a unit in your arsenal, it is quite possible to make it yourself, since the prices for muffle furnace devices in stores are quite high. Self assembly such a unit is fast enough, especially if you prepare necessary materials and tools.
Muffle furnace - main varieties
By the type of elements used to heat muffle furnaces, their classified into the following types:
- powered by electricity;
- using gas for heating.
Immediately I would like to note that it will not be possible to build a muffle furnace operating on gas with your own hands. First of all, because such home experiments are punishable by law. But the electric analogue of the furnace is available for homemade production to everyone who wishes. Wherein by design such devices are divided into the following types:
- horizontal muffle furnace as in the photo;
- vertical or pot firing device;
- bell furnace, an example of which is shown in the photo;
- tubular system.
I would like to note that for a do-it-yourself construction, the design of a muffle furnace is suitable, in which the heat treatment of materials takes place in an air environment. In turn, devices operating in a vacuum are manufactured only in the factory.
Before building such a device, you need to understand the principle of its operation. First, you need to decide on what fuel the muffle furnace will operate: coal, electricity, gas or wood... At the same time, it is easiest to make an electrical device with your own hands, consisting of a heating chamber and high-quality thermal insulation.
Heat in such a furnace is accumulated thanks to refractory bricks, and heat treatment of materials takes place in the main chamber - a muffle. For making a stove at home, any ready-made refractory form or one made by hand from fireclay bricks or heat-resistant clay is suitable as a muffle.
It is very important to understand that the temperature at which the chamber of the muffle furnace begins to melt must be higher than that of the materials processed in the unit. In this case, you can do it yourself build a small oven for melting and firing various materials in small quantities.
Structural components of a muffle furnace
For the case of such a device, the old gas stove, more precisely, her oven or its electrical counterpart. To make the old oven suitable for further use, all parts made of plastic are removed from it. If finished structure for the body of the house was not found, then it is welded from metal sheets 3 mm thick.
Equally important is heat-insulating part a muffle furnace, the quality of which determines the efficiency and heat loss of such a device. Red heat-resistant brick is used as an internal thermal insulation layer, which can withstand high temperatures up to several thousand degrees.
For additional thermal insulation that reduces heat loss along the outer layer, lay perlite or basalt wool... It is not recommended to use asbestos materials, since carcinogenic substances are released during their heating.
As heating elements inside such a device, spirals are used, for the manufacture of which they take nichrome or fechral wire 1 mm thick. At the same time, nichrome material, or, more precisely, a wire made of nickel and chromium, is quite ductile and does not corrode.
Features and varieties of muffles
For the manufacture of a muffle can be used different materials, while most often use ceramics or ceramic fiber.
Assembly material and tool
In order to assemble a furnace for firing ceramics with your own hands, you will need availability of the following materials and equipment:
- electric grinder;
- fireclay red brick;
- electric welding;
- finished body made of metal or sheet steel;
- metal corners;
- heat-insulating non-combustible materials;
- ready-made heating coil or nichrome wire.
First you need to decide on the body of the device, on the dimensions of which the size of the main chamber of the furnace will depend. This is relevant for old oven or buckets. If the body is welded from sheet metal, then its dimensions are adjusted after the construction of the muffle.
Also, the working chamber for firing is manufactured from fireclay clay or ceramic pipe with an average diameter. Therefore, the very process of assembling a muffle stove with your own hands has certain nuances.
- A fireclay brick muffle as in the photo is connected in a circle. To do this, the brick is cut with a grinder until the necessary bevels are formed. After that, a groove is cut in each brick to accommodate the spiral. At the same time, on all bricks, it is cut horizontally, and on one with a slope, which ensures the displacement of the spiral at a lower level.
- If the body is made from an oven, which is lined with refractory bricks, the masonry is made with a mortar based on clay, chamotte powder and sand. In this case, the seams of the masonry should not exceed 5 mm. After the masonry dries out, grooves are made in it for laying the spiral. I would like to note that the groove width should correspond to the thickness of the spiral, and the distance between adjacent elements should be 20 mm.
Heating coil fabrication and assembly
Nichrome wire 1 mm thick is wound on a steel rod with a smooth base. In this case, the diameter of the spiral should not exceed 6 mm... It is also important to ensure that adjacent turns do not come into contact during winding. The finished spiral is placed in the grooves cut in the fireclay brick.
I would like to note in order to prevent the spiral from falling out during heating, they make it putty with a thin layer of heat-resistant clay or attach it in several places with wire. If a ceramic pipe is used as a muffle, then the spiral is wound on the outside.
To complete the assembly of a do-it-yourself muffle kiln, it remains do a row simple work that everyone can do.
- A brick or ceramic working chamber is housed in a steel casing at the bottom of which the heat insulating material.
- On the outside, the furnace bottom is reinforced with steel corners. This is due to the fact that the weight of the brick is quite large. There must be a gap of up to 40 mm between the walls of the muffle and the main body, in which the insulation material is placed.
- The furnace cover is made of 2 layers of steel and heat-insulating material inside.
For convenience, it is advisable to fix the handle to open the main chamber of the muffle furnace.
How to properly dry a finished muffle furnace
Dry the finished muffle furnace with your own hands need gradually in a well-ventilated place.
- Drying time of the structure is from 5 days to several weeks.
- In the case of intensive forced drying, the clay used in the manufacture of the oven will crack and such a device cannot be used.
- To check the quality of drying, the muffle furnace is switched on to a minimum and if there is no moisture evaporation, then the device is completely dry.
It is important to remember that it is imperative to follow all safety rules when manufacturing and using such a high-temperature device.
Mini muffle furnace
For miniature works as a finished muffle furnace, as in the photo, use resistor low power up to 150 W... The diameter of the 150 W resistance is approximately 3.8 cm. The size is approximate, since the diameter of the electro-porcelain tube is determined individually by each factory.
The resistance value of a 150 W wirewound resistor at 220 volts is 350 ohms. In this case, the weak points of the use of resistance as a muffle are considered to be contact clamps made of brass, which require additional heat removal, for which copper strips of 2 mm thickness are used.
After attaching the heatsink, which serves as legs, to the terminals of the wirewound resistor connect wires, supply, power, and heat sinks are insulated with several layers of non-combustible, insulating material, which is further impregnated with heat-resistant varnish.
At the last stage, a shell made of the finest sheet steel is put on the muffle. At the edges, the shell is bent inward at a right angle so as not to damage the insulation on the legs. In this case, a full flanging inward is not needed, so the insulating material will be qualitatively retained in the shell. This completes the mini-muffle stove.
A muffle furnace is a chamber device with a horizontal discharge system, which is an essential criterion for the owner's safety during use. In certain cases, a mine version may be required, in which the muffle is made deaf and located vertically - this will not only significantly reduce the production time, but also allow heating objects without direct contact with air. In any case, the heating system, the chamber and the thermocouple, which controls the maintenance of the required temperature, remain the key elements of heating the furnace.
History of origin
V late XVII- the beginning of the XVIII centuries. French coachman Jeanto began to invent the steering linkage, which received his name, but he did not succeed in starting practical tests, because the axes of the prototypes were constantly breaking. Jeanto, who was sure that the invention would bring him huge profits, was completely desperate, because the carriages put on his axle were constantly overturning right during the trip. However, the matter made significant progress when a Russian nobleman visited Zhanto's workshop, wishing to order, by order of Peter the Great, a luxurious carriage from the best European craftsman as a gift to the khan from Bukhara.
Having tried the product for strength, the nobleman advised Zhanto to first perform cementing in a muffle with horns cattle, crushed into powder, and only then proceed to hardening. Thanks to this method, the steel had to remain viscous on the inside, and on the outside it had to be covered with a hard hardened crust, which would last for many years before being worn out.
Despite the fact that the muffle kiln for firing ceramics has changed significantly over the past time, it continues to maintain its basic characteristics. A muffle is a container that is resistant to high temperatures and has an impermeable structure. In it, the part undergoes the necessary heat treatment due to the fact that it completely isolates it from external influences, while ensuring uniform heating from all sides.
Over time, the requirements for the quality of heat treatment increased significantly, which made it possible already in early XIX century to begin the mass use of furnaces on an industrial scale. To date, even a low-temperature muffle furnace has appeared, in which the elements undergo a hot curing procedure.
Application today
- Safe remelting of valuable metals to avoid impurities in their structure and prevent direct interaction with the flame.
- Artificial aging of metals.
- Firing ceramics.
- Getting a flat surface.
- Drying of materials with high degree thermal conductivity.
- Burning objects to the state of mineral components, for example, during body cremation.
The muffle furnace is also used for growing single crystals and high temperature processing medical equipment... Thanks to this, it is possible to destroy all harmful bacteria without damaging the tools themselves.
Is it better to make or buy?
If you want to create a device such as a muffle furnace with your own hands, be prepared for the volume of the muffle to not exceed 7 liters, and the work itself will be lengthy and time-consuming. Before starting work, make your choice suitable model which you will be guided by. They differ:
- Heating temperature - from 100 to 2000 ° C.
- Design.
- Processing mode.
- Heating type.
The undisputed sales leader is the PM-8 and PM-10 muffle furnaces - the muffle chamber does not exceed 6.5 liters. It is her prototype that most people choose for their own handicraft, because the main material used in the work is only heat-resistant ceramics.
It is produced in several versions, K and M, differing only in that the latter has digital control. The cost starts from 1 thousand dollars, while you can buy much more cheap option whose design will function as well as if you bought it from the store.
Despite the fact that this muffle furnace has excellent data, one significant drawback still exists - it is the door. It gets significantly hot during work, which is why the owner often gets burns.
How to start creating?
When starting the manufacture of such a structure as a muffle furnace with your own hands for the first time, it is best to give preference to a structure that will be used for minor work. You can significantly reduce the cost of the product by creating a small hole in back wall muffle. It will be enough if you are not going to use a design such as a muffle furnace on an industrial scale.
First of all, decide on which fuel - gas or electricity - the muffle furnace will work. The price for a gas device will start at $ 1,000, however electrical system much easier to manage. In addition, you will need to purchase a high-quality temperature sensor (thermocouple) that monitors the degree of heating up to 1300 degrees. Mounting the sensor to the oven can be made of soft steel wire, carefully twisting it with pliers so that the ends do not touch each other.
For safety reasons, it is better not to try to make a muffle on your own, because if the design is incorrect, the product will simply lose its value after processing. It is best to purchase ceramic chemical glassware from a laboratory equipment store for the required type of discharge.
Secondary appointment
The muffle furnace allows you to quickly remove moisture from the material. In this case, it does not matter at all whether it is ordinary water or a liquid element. chemical composition in the material. In addition, small structures are very convenient to use when carrying out cupelling ( laboratory experiments), easily melting lead with gold or silver by oxidizing the structure with oxygen in the air to isolate precious metals in their pure form.
When choosing a muffle furnace, it is better to give preference to well-known manufacturers who guarantee the quality of the product, which also provides high firing rates.
The muffle furnace is designed for uniform heating of substances up to different temperatures... The muffle present in it protects the heated object from direct exposure to combustion products.
Navigation:
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 a heat-insulating material and all this is sheathed with a metal casing 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 fibrous material is its fragility: under the action 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 accuracy, especially in a laboratory muffle furnace, because the accuracy of the research depends on their value and the result obtained.
Application of muffle furnaces
The muffle furnace is widely used, 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 - 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. They are usually provided with several layers: refractory bricks, ceramic fiber and sheet metal sheathing. 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 ceramic muffle furnace has temperature regime 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 firing muffle furnace is often equipped with removable heating elements, which can be easily replaced in case 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 the top, chamber with loading in front, there are bell-type 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.
For working 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... Muffle furnaces Russian production 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), received a lot positive feedback from leading enterprises in various directions.
Muffle furnace (you can buy in St. different models) of the company Elektropribor has also established 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.