Brass is an alloy based on copper and zinc. Various parts are made from it - bolts, screws, fasteners, parts for electrical tools, microcircuits and others. If necessary, brass can be melted in a special furnace to make the desired part from the melt. But what is the melting point of brass? Can it be melted at home? And what should a metallurgist remember when working with this alloy? These issues will be discussed in the article.
Useful video
Watch the video, which shows how to start making a muffle furnace: what materials and tools are required, what needs to be done first, and what actions are not recommended.
Making the lid
- Cut a circle out of steel, identical in diameter to the already fully assembled structure.
- Place fireclay bricks on top of the glue - it will provide sufficient sealing.
Weld handles on the sides to make it convenient to lift and remove the lid, and a latch for closing.
Cover the edges with fireproof silicone; before doing this, be sure to degrease the surface (even White Spirit will do).
Let us remind you that when the oven is operating, it must be closed. Excessive air ingress will lead to rapid wear of nichrome.
Do-it-yourself aluminum furnace - easy!
The desire to have a small melting furnace at home is easily feasible and does not require large investments, knowledge or time to build. You can independently build a unit with a capacity of up to 10 kg of molten metal and make souvenirs, accessories or blanks for small aluminum parts. The temperature reached in a home furnace allows you to melt most aluminum alloys in a short time (several tens of minutes depending on the volume of scrap).
Of course, the quality of the resulting metal differs from industrial grade. Aluminum melted at home contains an increased amount of oxide films, contaminants, and is less stable in chemical composition. But it will still be suitable for use at home.
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%. More details
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.
Recipes
| Ingredients | Process | Result |
| Gold bar, Silver bar | 22 | |
| Energy: 1,600 | ||
| Time: 5 sec | ||
| Voltage: 16 / |
| Energy: 2,400 |
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| Energy: 1,600 |
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| Energy: 3,200 |
| Time: 10 sec |
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Types and purpose
Tunnel-type furnaces vary greatly in their structure and functional purpose. There are bulky brick structures for firing bricks, rotating clinker cement kilns, made in the form of a huge metal pipe.
There are also compact steel ovens for confectionery and bakery products, powerful energy-intensive installations for the heat treatment of steel, as well as small units for ceramics and earthenware.
Brick and cement firing
Tunnel-type heating units are most widely used in the production of building materials - bricks and cement. The clinker rotary kiln for cement production consists of huge pipes, up to 230 meters long, open at the ends and rotating at a speed of 1 - 1.5 revolutions per minute. The stove is installed at a slight inclination to the horizon of 3 - 4 degrees. In such a device there are 6 zones, such as:
- Raw material drying sector (moisture evaporator).
- Heating sector.
- Decarbonization area.
- Sintering area.
- Exothermic zone.
- Raw material cooling zone.
The cement sintering process occurs after raw materials are loaded into the raised part, and fuel is supplied from the lower part in the form of a mixture of air and fuel. The finished product is poured into a special refrigeration device.
Tunnel brick kilns consist of a gallery with a trolley, hand cart or conveyor belt. The walls and roof of such a unit are made of refractory fireclay bricks. Heated air enters from below or above, and gas and smoke removal occurs in the opposite direction.
The amount of heat supplied and cooled air removed is regulated using a system of special dampers or dampers. The raw brick is first heated, then fired, and then cooled. The temperature when firing brick products inside the main chamber of the installation can reach 900 degrees Celsius. After this, the cart with bricks is sent to the drying chamber, which operates on the heated gases coming out of the oven. It is structurally combined with the stove.
Firing ceramic products
To make ceramic products, devices similar to brick tunnel kilns are used. The size of such structures is smaller, which is due to the small volumes of production of ceramic and clay products. The very principle of operation of such kilns is similar to the process of firing and drying bricks.
In the metallurgical industry
In the heat treatment of steels and alloys, tunnel furnaces are used to anneal and heat metal parts before other coating processes. Also in such units, insulators are hardened for the needs of electrical production.
Production of bakery products
In bakery production, metal tunnel ovens are used, made in the form of an elongated box and equipped with a conveyor feed of the baked product. Inside such a unit there is a burner, a steam humidifier, a conveyor belt, an exhaust system, as well as mechanisms for regulating the heat supply to different sections of the oven.
Their sizes range from 10 to 25 meters, they are used in bakeries; it is not economically profitable to use such installations in home mini-bakeries. They operate on natural gas or electric energy, as the safest types of fuel for the food industry. Fuel oil installations are used much less frequently.
Baking confectionery
Confectionery tunnel installations are almost completely similar to bakery ovens, with the difference that they have smaller dimensions and more accurate baking temperature conditions. Confectionery products use different creams, which requires precise adjustment of the temperature inside the oven, as well as less processing time.
Brass grades and applications
The brand of brass and its scope of application depend on the composition. For example, tombak, which belongs to the class of wrought brasses, which contains more than 95% copper, can easily combine with steel, forming a bimetal with it. This compound is used in the manufacture of insignia and various objects of art and interior design - figurines, frames, candlesticks .
LO grade brass is used for the manufacture of condenser tubes used in various heating equipment, for example, gas boilers, autoclaves, and bellows.
The LS brand is used to create parts for watch mechanisms, adapters and connecting bushings. Printing matrices are also made from it.
LMC - is found in old Soviet coins with denominations up to 5 kopecks, fittings, nuts and bolts, and its subtype with the prefix “A” is found in parts of river and sea vessels.
Brass, marked LA or LZhM (and its subtypes), is also used for the construction of sea ships and aircraft, various electrical machines and bearings. Very common in parts for various chemical equipment.
Types and conditions of processing of raw materials
The main methods of processing materials in a homemade chamber are:
- Firing ceramics
- Hardening of metal products
- Melting of non-ferrous metals
Firing ceramics
The process of obtaining finished ceramic products involves firing blanks from raw clay and then covering them with glaze. At home, a do-it-yourself muffle furnace can fire several pieces of dishes and other crafts at once
In heat treatment, it is important to maintain an even heating regime for the chamber. Theoretically, it is impossible to indicate the exact time frame for processing a material at a certain temperature - this is achieved practically
Clay materials placed in a home muffle furnace for firing are divided into 3 groups:
Porcelain
The dried clay is subjected to heat treatment in two stages. Primary firing is carried out in the range from 800 0 C to 1000 0 C. The clay gains strength and becomes porous. Then it is dipped into a container with glaze. Repeated firing is carried out at different temperatures, depending on the purpose:
- natural porcelain - 1400 0 C
- dining room - 1350 0 C
- plumbing parts - 1250 0 C
Faience
The use of refractory raw materials during firing practically does not form a liquid phase. To mature the shard of the product, it is processed at a temperature of 1200 - 1250 0 C. Repeated heat treatment with the applied glaze is carried out at a temperature of 900 - 1000 0 C. If it is necessary to apply painting, then for the third time they return to the primary level of the temperature regime.
Majolica
Red refractory clays are used. Heat treatment requires precise adherence to the heating regime. When heated to 950 0 C, loose, fragile products are obtained. When heated to 1050 0 C, the raw material is sintered into an unusable, dense glassy mass. To accurately maintain a heating level of 1000 0 C, it is necessary to build a thermocouple into the chamber with the oven connected to a digital display.
The repeated processing of glazed materials is carried out at a temperature of 900 - 950 degrees.
Hardening of cutting metal products
Hardening the cutting surfaces of steel tools by heat treatment is called metal hardening. Hardening of metal products has been done by people since ancient times. The essence of the process is to roast the metal until a change in the structure of the crystal lattice is obtained (polymorphic transformation).
The metal is brought to a red-hot state in a heating chamber at a temperature of 750–850 0 C. It should be noted that some grades of steel are hardened under higher heating conditions, ranging from 1250 to 1300 degrees. Then the hardening furnace is emptied of hot products, which are then subjected to rapid cooling in an oil environment or in water. In this way, the hardness of the metal is increased.
This process is important for hardening the cutting surfaces of steel tools (knives, drills, chisels, milling cutters, etc.). Quenching (tempering) is best done in an oil environment. When hot metal is released into water, its surface is covered with a mass of steam bubbles, which slows down the process.
As a rule, finished tools or workpieces made of stainless steel are subjected to hardening. These products usually do not require a large volume quenching chamber, so a fuse muffle furnace is best suited for this purpose. A description of the creation of such a design will be given below.
Melting of non-ferrous metals
A muffle furnace is convenient to use for melting non-ferrous metals, but this does not apply to tin and lead. Their melting point is so low that it is enough to use a gas burner on a household stove.
In order to melt metals such as copper, bronze and brass, you will need a heating container. A liquid mass of metal is obtained in a crucible, which is then poured into special molds. Home craftsmen create various decorative elements for lamps, furniture, figurines and many other crafts.
Melting temperature of non-ferrous metals:
- copper - 1080 0
- bronze (depending on brand) - from 930 0 to 1140 0
- brass ranging from 880 to 950 degrees
Melting furnaces - main characteristics
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.
Making an electric muffle furnace with your own hands
Consider the construction of a small muffle furnace. The device will be connected to a network with a voltage of 220 V.
Selection of materials
Materials for making the device are available in hardware stores and electrical departments. To create a muffle furnace you will need:
- sheet steel 2-3 mm thick (2 sq. m);
- rolled steel with a “corner” section (3 m);
- heat-insulating material (basalt wool);
- fireclay bricks, 12 pieces;
- mortar (5-7 kg);
- chromel-alumel thermocouple;
- ceramic tube for thermocouple;
- nichrome spiral;
- fiberglass tubes for insulating the leads of the spiral and thermocouple.
When choosing materials, they are guided by their quality: heat resistance, ability to withstand rapid heating and cooling. In order for the muffle to serve for a long time, you should not take a brick that has been in use for several years.
Preparing tools
To prepare mortar paste, you will need a ten-liter bucket and a stirrer. When mixing the solution, use a respirator. For installation you will need the following construction tools and equipment:
- welding machine;
- electric drill;
- Bulgarian;
- set of pobedit and metal drills;
- stove maker's tools: hammer-pick, trowel, small spatula, measuring tape;
- electrician's tools: pliers, wire cutters, round nose pliers, metal ruler, regular and Phillips screwdriver.
Step-by-step instruction
The workflow includes the following steps.
- Mark and cut the steel sheet. Cut out the casing parts and door parts.
- Weld the casing and door.
- The hinges for the door and the lock are welded to the body.
- A solution is made from the mortar (according to the instructions on the package).
- A model of the furnace is made from bricks, determining where the spiral will be laid.
- In the bricks, grooves are made with a drill for laying the spiral. For work use a pobedit drill.
- The corner profile is cut with a grinder and a frame for bricks is welded from it.
- A muffle of bricks is placed in the frame (on a mortar mortar).
- The masonry is dried for 3-4 days.
- A nichrome spiral is placed in the grooves in the walls of the muffle. After drilling a hole in the bricks, bring the contacts out.
- A ceramic tube and fiberglass protection are placed on the thermocouple.
- A hole is made in the muffle using a Pobedit drill for the thermocouple and it is inserted into the chamber.
- The contact points are coated with mortar solution.
- The muffle is dried for 1-2 days.
- A layer of mineral wool is placed on the back wall of the casing.
- A muffle is installed in the casing. It is placed on a metal grid-stand so that the heavy stove does not compress the layer of cotton wool underneath it.
- Using a metal drill, holes are drilled in the casing and the contacts of the spiral and thermocouple are brought out.
- The gap between the muffle and the casing is tightly filled with basalt wool.
- A layer of basalt wool is placed in the door and secured with nichrome wire.
- The door is installed on the casing and a lock is installed.
- Cut out a piece of fireclay brick to fit the door. During firing, it is placed in a muffle in front of the door.
Important! To prevent the spiral from falling out of the grooves made in the brick, it is strengthened in several places with mortar solution
Tools
The tool kit should consist of:
- tape measure and square;
- Bulgarians;
- welding machine with a set of electrodes with a diameter of 3 mm;
- cutting wheels for metal;
- file;
- hammer, pliers.
You also need to take care in advance about personal protective equipment during welding work:
- protective mask;
- workwear made of dense material;
- closed shoes;
- rubber (dielectric) gloves.
Scope of application: space heating
In everyday life, the induction heater circuit was implemented for heating boilers and stoves. The former have gained especially great popularity and recognition among users due to the absence of heating elements, which reduce performance in boilers with a different operating principle, and detachable connections, which saves on maintenance of induction heating systems.
In practice, several options are used where different types of inductors are used:
- electronically controlled heaters to create currents of the desired type in the coil;
- vortex induction heaters.
Electrical circuit of an induction heater
Varieties and distinctive features
In order to be able to create a high-quality stove with your own hands, it is worth understanding what types it is divided into, taking into account the fuel and energy consumed, namely:
- gas;
- electric.
This separation allows the use of various energy sources, which allow heating the space inside the created structure. At the same time, a stove with installed elements for electric heating is more popular. This allows you to control the temperature inside the structure if it is necessary to process certain raw materials.
A modern muffle furnace has its own characteristics in design and resulting production capabilities, namely:
- in the resulting design and volumes of internal space;
- methods and methods of heating the internal space of the furnace;
- use of special protective formulas and functions;
- operating temperature parameters.
Depending on the temperature obtained, all furnaces are divided into three types:
- moderate temperature ovens, with parameters of 100-500 degrees Celsius;
- medium ovens, with temperatures of 400-800 degrees Celsius;
- high-temperature oven, with parameters 400-1400 degrees Celsius;
- ultra-high temperature stoves, they heat up to 2000 degrees Celsius.
Materials and elements for work
Muffle furnace for melting aluminum with your own hands or hardening steel parts - we prepare a full set of materials for production. We will need:
- fireclay brick;
- thermal insulation;
- sheet metal or any available material. If you have an old safe with a layer of sand on the inside, you're in luck. Such a stove will last a long time and will save on the outer layer of thermal insulation;
- refractory clay, sand or ready-made mixture for bricklaying. To seal cracks and voids, you can purchase a fire-resistant sealant or use a solution;
- electrical cable, ceramic insulators, automatic connection in the panel.
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.
Operating rules
A do-it-yourself electric oven must be operated in a room with a reliable ventilation system. The electrical wiring must be in good working order, its energy capabilities allow it to withstand the load from this electrical appliance, eliminating the risk of a short circuit.
In addition, there are a number of rules that must be followed:
- Do not connect the device to the power supply system without sufficient water in the device.
- Before the first fire and periodically during operation, measure the resistance from the network, which should not exceed 3 - 5 ohms.
- To prevent damage to the heating elements due to scale, you need to fill the device with water softened with vinegar or citric acid.
- Once every six months, the stones are moved into the electric furnace and cleaned of dust and cracked elements.
- If in winter the bathhouse is not heated regularly, then after each visit to the bathhouse the water from the stove must be drained, since it can expand when freezing and break the connecting seams of the body.
DIY muffle furnace for firing ceramics
23.10.201616:13
In order for clay masterpieces to be used in everyday life and serve you for a long time, they must be properly fired. And in this matter you cannot do without a good stove and a competent approach. Today there are many professional ovens; they differ not only in their size and capacity, the quality of firing, but also in their ease of use. If you want to purchase a proven muffle furnace, contact us - Keramistam.ru, we will tell you everything in detail, show you, and tell you which one is right for you. And if you are confident in your abilities and have a burning desire to make a stove with your own hands, then in this article we will try to describe in detail this difficult but interesting process. Let's start with the fact that there are different types of muffle furnaces: gas and electric. Today we will talk about how to make an electric oven yourself. For this you will need:
- Fireclay bricks and ceramic slabs for muffles.
- Sheet steel for the furnace body.
- Fireproof, heat-insulating materials for filling voids.
- And also heating element.
The muffle can be made from different materials:
Ceramic. The temperature transition between the chamber and the heating element is reduced
This is very important for ceramics, since it cools more slowly than other materials, so if you do not pay due attention to the muffle, the furnace will be unsuitable for use. Ceramic fiber muffle. Fiber benefits: oven heats up quickly
Disadvantages - the material is fragile and at high temperatures, harmful substances can be released.
Another important point. Furnaces differ in the type of loading (pot, bell and horizontal). Today we will look at how to make a horizontal loading oven. It is necessary to weld the body from sheet steel. Or use an old refrigerator or gas stove. The inside of the body must be finished with basalt wool, a layer of at least 10 mm. We recommend gluing the boards using silicone sealant. The next step is laying the refractory. The masonry is assembled from fireclay bricks, in which special cuts are provided in advance for the further installation of the heating element. We start the laying from the bottom, then we assemble the walls, and at the end we lay out the top part. To make the structure even stronger, cement can be added to the masonry mixture. Approximately 20%. Additional reinforcement can be done using a metal corner. The oven door is also made of fireclay bricks. In the areas where the door meets, treat the muffle with a release agent, such as grease. We recommend making a closed heater, as it ensures safety in terms of the release of toxic gases. As a heater we will install spirals made of nichrome and fechral wire 6 mm in diameter
It is important to calculate the required wire length, since the heating temperature will depend on the current strength. Well, the final step is assembling the entire structure.
You need to lay a sheet of asbestos on the bottom of the body and make a fireproof fill of fireclay clay. The muffle is installed one brick at a time. Coat the joints with fire-resistant masonry mortar. Important! The camera must be placed strictly in the center of the body. the space between the chamber and the housing must be filled with heat-insulating materials. It is important to provide holes in the housing for the leads of the heating elements, into which ceramic insulators will be installed to prevent short circuits. Well, the final step: fill the entire remaining space with refractory mortar and dry thoroughly. The oven is ready!
Making a muffle furnace with your own hands is not an easy task. And the quality of firing will directly depend on the careful study of each element separately and the furnace as a whole. If you like to experiment and are confident in your engineering abilities, then go for it, the necessary materials and components - spirals, bricks, cotton wool, thermocouple and more can be purchased at the Keramistam.ru store. Or come to us immediately for a ready-made and proven option, we will always help and guide you in the right choice. , Welte, Rohde and others who have proven themselves in the furnace business are ready to begin hot and responsible work. Photo:
Installation Requirements
The safest place to place an electric furnace is the corner closest to the front door. You can also install it in the center, but be sure to comply with the following requirements:
- the presence of a gap between the hot surfaces of the stove and the walls of the steam room;
- Highly flammable surfaces are protected with a special screen;
- protective fences have been installed with a gap between them and the stove measuring 7 cm or more, which will help to avoid severe burns on the skin in case of accidental contact;
- There should be an inlet for the ventilation system behind the stove. It should be through and located at a height of 7 - 10 cm from the floor level. The size of the hole depends on the power of the oven, on average its diameter is 15 - 25 cm;
- a massive support for such a heating device is not needed, however, several layers of fireclay bricks still need to be placed under the installation of the product. A thick sheet of metal with a backing made of heat-insulating material, for example, slabs of extruded polystyrene foam or fiberglass wool, is also suitable for these purposes;
- for a small electric furnace, it is enough to place an asbestos-cement slab or ceramic products on the floor.
Original mini furnace for melting aluminum
I would like to tell you about another interesting device that you can assemble with your own hands.
Melting furnace from a bottle
This is a rather original way to create a mini-stove. A glass bottle with a suitable diameter is lubricated with oil and then wrapped with a bandage. The next layer is clay mixed with liquid glass. After drying, the surface is wrapped with nichrome wire and again covered with a clay mixture. After final drying, the glass is removed, and the edges of the wire are connected to the electrical network.
Melting furnaces - thyristor - LEGNUM (Taiwan)
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. More details
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. More details
Stove made of earthenware barrel
You can also make a larger stove from a faience 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 do under. To do this, a “foundation” of fireclay bricks is assembled on a small sheet of steel and connected with metal corners. Then, in the upper part of the barrel, grooves are made for the spiral (no more than three or four) - the heating element of the required power will be placed in them.
Stage three. All that remains is to make the outer shell of galvanized steel. It is made removable, since it will be put on only after covering the product with a muffle (barrel). The space between the muffle and the outer shell is filled with asbestos.
The firing procedure is no different from the previous version, but the temperature is adjusted using a thermocouple. The walls of the barrel are thick; by the time they light up (even without the outer shell), the ceramic product will already be burnt.
Classification of muffle furnaces
Based on the type of heating elements, muffle furnaces are divided into:
- electrical;
- gas.
By purpose they are divided into:
- for metal melting;
- for firing ceramics;
- for melting glass;
- for hardening metal;
There are also industrial and homemade muffle furnaces.
Industrial muffle furnace with automation
But it is impossible to make gas-powered stoves at home, although gas is cheaper than electricity, since such experiments are prohibited by law. Electric oven control provides convenient temperature control.
According to their design type, muffle furnaces are divided into:
- horizontal (the simplest);
- vertical or potted type;
- bell-shaped;
- tubular.
Heating can be carried out in air, in a vacuum or in a gas environment. At home, it is only possible to design a furnace with heat treatment of products in an air environment.
When you make a muffle furnace yourself, you can give it the desired shape and volume, and decorate it in a style suitable for the interior.
Main parts of the structure
- The outer part of the furnace, the shell (body). It is convenient to use a disused gas stove, or rather an oven from it or an electric stove, as a body for a future muffle furnace. To use them, all plastic parts are dismantled. In cases where it is not possible to use such housing options, it is welded from sheet metal (thickness of at least two millimeters).
- Thermal insulation layer. This part of the design is extremely important. The efficiency of the furnace and the heat loss it will incur depend on its quality. The inner layer of thermal insulation is a fireproof (fireclay) brick that can withstand temperatures up to one thousand degrees.
- The outer layer, which reduces heat loss to the surrounding space, is laid from perlite or basalt wool. Asbestos is unsafe to use; when it is heated, carcinogenic substances are released into the atmosphere.
- Elements that directly heat the workspace. The heating elements inside the muffle furnace are spirals twisted from nichrome or fechral wire. Thickness 1 mm. Nichrome (nickel-chrome) wire is very ductile and resistant to corrosion.
- Fechral (aluminium, chrome, iron) wire is somewhat cheaper due to the absence of aluminum in the composition and also has the necessary properties for its use in a muffle furnace.
List of materials and tools for assembling the structure
- grinder (machine for grinding and cutting materials) with cutting wheels for metal;
- welding machine;
- sheet steel >2mm thick;
- metal corners;
- fireclay fire-resistant brick;
- fireproof mixture;
- heat-resistant silicone;
- basalt thermal insulator (cotton wool, density 200 kg/m3) or perlite;
- safety glasses and respirator;
- nichrome (fechral) wire with a cross section of 1 mm;
- wire cutters or metal scissors.
Manufacturing of 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 will need the following tools:
- angle grinder (grinder) and 1-2 wheels;
- electric arc welding and electrodes;
- metalworking tools, including wire cutters;
- 2mm nichrome wire.
and materials:
- 2.5 mm steel sheet or used oven body;
- corner;
- fittings;
- basalt wool;
- refractory fireclay brick;
- fireproof mortar;
- silicone sealant.
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 bricks or other heat-insulating material that can withstand heating temperatures of up to 10,000 - 12,000 are used;
- 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.
Possible difficulties and problems when creating a furnace
When manufacturing a device, difficulties arise with the selection of material and installation of a temperature control system. Incorrectly selected materials lead to rapid destruction of the muffle. Thus, some craftsmen, to save money, use low-quality bricks and clay-sand mortar instead of fireclay. This leads to cracks in the muffle and heat loss.
The cracked muffle is temporarily sealed with a solution of fireclay clay. The camera needs to be removed and replaced with a new one.
If the furnace is connected to the network without a thermostat, the temperature in the muffle is not controlled. This leads to damage to products that require firing at a given temperature. To solve the problem, you should purchase a thermostat and electrical equipment, assemble a control unit and connect it to the heating elements of the muffle.
About the future design
Construction of a homemade electric stove for a sauna
The simplest model of an electric stove consists of a box-shaped body, inside of which there is a tank with a door on the neck for adding water and several heating elements welded together. Stones are laid on top and between them. When heated, the stones release thermal energy into the steam room, raising the temperature in it to the optimal level.
For metal structural elements, stainless steel is used, which does not corrode in water, does not burn out under high temperatures and does not emit harmful substances.
If possible, the device is controlled by an electronic remote control, which should be located outside the steam room. It is connected to the furnace heating unit with an electric cable.
The heating system is activated by turning on the timer. The maximum permissible heating level for heating elements is 650ºС. If the temperature drops to 600ºC, the sensor is triggered and the “Heating” light comes on. The stones are heated when the timer is in standby mode.
As soon as the top layer of stones heats up to 550ºC, the timer is triggered and the light turns on in the “Ready” position.
Stones can also be placed on top of the body above the heating elements on a metal grid welded from reinforcement and during bath procedures, water them or herb infusion to create steam.
Possible problems when creating a furnace
When manufacturing a device, difficulties arise with the selection of material and installation of a temperature control system.
Incorrectly selected materials lead to rapid destruction of the muffle.
Thus, some craftsmen, to save money, use low-quality bricks and clay-sand mortar instead of fireclay. This leads to cracks in the muffle and heat loss.
The cracked muffle is temporarily sealed with a solution of fireclay clay. The camera needs to be removed and replaced with a new one.
If the furnace is connected to the network without a thermostat, the temperature in the muffle is not controlled. This leads to damage to products that require firing at a given temperature.
To solve the problem, you should purchase a thermostat and electrical equipment, assemble a control unit and connect it to the heating elements of the muffle.
For ease of assembly, it is better to make it with removable front and back covers that are secured with screws. A door is attached to the front cover on a hinge, which should open horizontally. A ceramic element is installed on the door using two bolts through asbestos gaskets, and the gaps are sealed with clay.
The ends of the nichrome wire are brought out to the back cover of the case. Ceramic insulating “beads” must be strung on both terminals. The wire is attached to the pin connector. Such connectors, as well as insulating “beads,” can be taken from old electrical appliances. A standard cord with a plug will be attached to the connector for connection to the electrical network.
All free space between the heating elements and the housing should be tightly filled with asbestos chips. In addition, the design of the furnace must provide a grounding terminal.
For ease of work, two small holes need to be made in the heating chamber: one on the back wall with a diameter of 10 mm - for installing a thermocouple, the other on the door with a diameter of 18-20 m - to observe the interior of the furnace during operation. Both openings must be equipped with closing metal curtains.
A lining plate made of thin stainless steel 0.5–0.8 mm should be placed at the bottom of the working chamber.
The oven is designed for 220 V AC. Heats up to a maximum temperature of 950 degrees within an hour. The weight of the stove is about 10 kg.
Lining and arrangement of the firebox
The very concept of a muffle furnace implies the presence of a muffle - an internal heat-resistant capsule that covers the heating circuit spiral, protecting it from small debris and scale. The muffle, as a rule, is removable in furnaces, which allows for repair and replacement of heating elements.
The main difficulty is to manufacture the muffle and the heating assembly body at the same time. To do this, you will need two types of heat-resistant ceramics: one for making the body with grooves, the other for the thin-walled muffle. For a ceramic base, it is better to use a mixture of refractory clay with an aluminum oxide content of at least 30%. The clay should be diluted with excess water and left to swell for a day, after which the settled water should be removed from above and only the swollen sediment should be left.
The ceramic body of the heater is massive, so it cannot be made from a pure binder; a filler is needed. Glass fiber, dry quartz sand or crushed fireclay are good options for the latter. The total clay content in the solution should not be less than 50% by volume; as a result, the mixture acquires the consistency of a viscous plastic paste. If the composition turns out to be more liquid, excess moisture is removed by adding small portions of building gypsum immediately before use.
Fireclay powderThe heater body is made on a three-dimensional corrugated cardboard template, the dimensions of which should be 15–20 mm larger than the planned dimensions of the firebox on each side. First, you need to wind a cord or silicone hose of the appropriate diameter onto the template, forming the required number of grooves for the spiral. After this, the template with the cord must be covered with clay on all sides, avoiding the formation of voids and achieving a wall thickness of at least 40 mm. The addition of alabaster helps the piece maintain its shape before firing. Carefully remove the cardboard insert from the dried ceramic body and pull the cord out of the grooves.
For the lining of the firebox, ceramics made from higher quality kaolin are used. Enriched clay of the KFN-2 brand is optimal; as a filler it is better to use crushed fireclay of high purity with a content of about 20–25% by volume of dry components. The mixture is mixed as described above and used to form the internal lining.
To ensure that the muffle can then be easily separated, spirals are inserted into the ceramic body in advance. Then the inner surface is covered with scraps of newsprint according to the papier-mâché principle. You should get at least 8–10 layers, while the inner surface should contain as few irregularities as possible. After the paper has dried, a refractory lining compound is applied to the inside. It is better to do this in several passes, giving time for excess moisture to evaporate; as a result, the muffle wall should reach a thickness of 15–20 mm. In this state, the entire assembly dries for several days until the plasticity is completely lost and a ringing sound appears when tapped.
After drying, primary firing is carried out - voltage is applied to the spiral and the hot product is kept for 4-6 hours. During the firing process, fechral passes the crystallization threshold and, becoming more fragile, takes the form of channels. The clay in the ceramic liner and muffle is baked and vitrified, becoming resistant to cyclic temperature changes. Well, the paper and glue residues simply burn out, forming a minimum technological gap for easy removal and installation of the muffle.
With this manufacturing method, you can use some tricks. For example, forming a ceramic body on a cone-shaped template to make it easier to remove the muffle. It would also be a good idea to extend the front part of the assembly, where there are no heaters, or place a small coil at the bottom of the chamber. Several copies of the muffles themselves can be made at once for one furnace.
Preparing fire bricks
The main and very first step towards creating a muffle furnace is preparing refractory bricks with chamfers in the right place for better fit of the joints during assembly. To do this, take a solution of fireclay clay and pour it into special molds.
It is important to note that:
- Six or seven (optional) refractory brick blanks must be very carefully adjusted at the joints to ensure a muffle without cracks. Next, you need to press all the bricks together with chamfers and fix them in this position with a special tie. It can be made from a metal tape 2-3 cm wide. At the ends of the tie it is necessary to provide devices that tension the tape. After assembly, you will get a six or seven-sided muffle design.
- Then, you need to make several transverse cuts in each refractory brick blank. They will house a heating element in the form of a spiral. The grooves are made with an abrasive saw. In one workpiece the grooves are made with an inclination, and in the rest - horizontal. The distance between the grooves is at least 2 cm, and the configuration must match the diameter of the electric spiral placed in them.
Assembling and pouring the frame
Having assembled the muffle into one whole, you can begin to manufacture the frame (casing). To do this, you need to select a metal pipe of the required diameter. In this case, there must be a gap of at least 150 mm between the bricks and the frame for better insulation and reduction of heat loss from the electric furnace. If there is no ready-made pipe, the casing can be made independently from galvanized sheet steel.
The assembly of the muffle and the furnace casing must be performed in the following order:
- Place the fireproof structure on a level surface.
- In two boards made of plank, thick plywood or chipboard, cut holes corresponding to the diameter of the stove casing.
- Insert the lower part of the casing into one shield, and the upper end of the pipe into the second.
- The shields must be fastened so that they do not slide along the smooth metal surface. This will prevent deformation of the sheet metal and accidental movement from its place during further work.
- Then a solution of heat-resistant and heat-insulating material is carefully poured into the space between the muffle brick and the casing.
Assembling and checking the oven
Assembly begins with the manufacture of the muffle furnace bottom, which can be made as a separate structure. This will make it easier to transport the stove in parts to the place of its use.
- A cylinder with a diameter equal to the dimensions of the casing and a height of 25-30 cm is made from a galvanized sheet. Legs made of a pipe or profile metal with a cross-section of 2 cm are attached to it to eliminate fire hazards.
- You need to make holes at the bottom end of the workpiece and weave a wire mesh through them. It will be a holding element for the poured and hardened solution made of heat-resistant material. The lid of the muffle furnace is made in the same way, in which it is necessary to provide a technological hole for ventilation.
- In the grooves of the muffle, lay a spiral of the required diameter, length and cross-section of the wire, so that the turns do not touch. Exit the ends of the wire through ceramic tubes. All that remains is to connect the electrical wires and test the resulting structure.
That's all for now, see you in the next lesson.
