Induction furnace for melting metal. Induction heating, hardening and induction melting of metals Induction furnace diagram

A DIY induction furnace is great solution for heating various rooms.

In addition to heating induction oven can perform the following functions:

metal melting;
purification of precious metals;
heating metal products, after which they undergo a hardening procedure or other processes.

However, the above functions provide industrial installations, and if you need to heat the house, then a kitchen stove is usually installed, and you can purchase it ready-made or make it yourself. Homemade induction furnace It is created quite simply, and you do not need to spend a lot of time on this process. However, it is important to know not only the rules for forming this structure, but also its other features, so that if necessary, you can carry out repairs or replacement of any main parts on your own.

Operating principle of the equipment

It is important to know the operating features of this type of oven in order to have a good understanding of its operation and parameters. The equipment works due to the fact that with the help of special eddy currents heating of the material is ensured. Such currents are obtained due to special inductor, which is an inductor. It contains several turns of wire of quite significant thickness.

The inductor can heat up due to welding inverter or other equipment. The operating principle of an induction furnace assumes that the inductor is powered from an alternating current network, and a high-frequency generator can also be used for this. The current flowing through the inductor forms variable field, permeating space. If there are any materials in it, then currents are induced on them, ensuring their effective heating.

If a furnace is used to create, then usually the material is water, which heats up. If the equipment is intended for industrial purposes, then the material can be metal, which begins to melt under the influence of current. Thus, the working principle induction cooker It is considered simple and understandable, so creating it on your own is quite simple.

The design of induction furnaces can be different, since two completely different types can be distinguished:

equipment equipped with a magnetic circuit;
ovens without a magnetic core.

In the first case, the inductor is located inside special metal , which begins to melt under the influence of currents. In the second, the inductor is located outside. The scheme of each option has its own specific differences.

Types and characteristics of various induction furnaces

There are several types of induction furnaces, the operating principles of which have certain differences. Some are intended only for industrial work, while others can be used at home, so are often intended for the kitchen, where they provide high-quality heating. Most often, the latest options are formed from a welding inverter, have simple design, due to which they maintenance and repair are simple jobs.

The main types of induction furnaces include:

Vacuum Induction Furnace. In it, melting is carried out in a vacuum, which makes it possible to remove harmful and dangerous impurities from various mixtures. The result is products that completely safe for use, they are of high quality. It should be noted that their repair is considered a complex job, and the creation process itself usually cannot be carried out on its own without specialized equipment and unusual conditions.
Channel design. It is manufactured using ordinary welding transformer , which operates at a frequency of 50 Hz. Here the secondary winding of this device is replaced by a ring-shaped crucible. A video of the creation of such a furnace can be found on the Internet, and its diagram is not considered complicated. Well-designed equipment can be used to melt a large number of non-ferrous metals, and energy consumption is considered low. Repairs are considered specific and complex.
Crucible furnace. The scheme of this design involves the installation of an inductor and a generator, which are the most basic parts of the equipment. To form an inductor, a standard copper tube. However, the required number of turns must be observed, which should not be more than 8, but also less than 10. The circuit of the inductor itself may be different, it may have figure eight shape or other configuration. It should be noted that repairing this equipment is considered a fairly simple job.
Induction oven for heating the room. As a rule, it is intended for the kitchen and is created on the basis of a welding inverter. Typically this setting is used in combination with hot water boiler, which makes it possible to provide heating for each room in the building; in addition, it will be possible to supply hot water to the structure. The principle of operation is that the inductor receives power from a welding inverter. It is believed that the efficiency of this equipment is low, but often it is the only one possible for creating heating in the house.

Read also: Wood stove with high level Efficiency

Furnace Forming Process

You can make an induction stove based on an inverter for your kitchen or other room in the house using your own efforts. To do this, it is recommended not only to study the theoretical part of this process, but also to watch a training video.

To form electromagnetic field, which will be available outside the inductor, it is necessary to use a special coil in which there will be enough a large number of turns. Additionally, you will need to bend the pipe, and this work has certain difficulties, so a more rational solution in this case would be the location straight pipe directly inside the coil, as a result of which it will work as a core.

Typically used metal pipe, however, it is considered a weak coolant, so it can be used instead polymer pipe, inside of which there will be small pieces of metal wire. For a current generator, the use of a standard inverter is considered optimal. Its maintenance and repair are considered simple and clear works, so it will be possible to provide long service life of the equipment.

Thus, to create the design you will need:

polymer pipe;
steel wire;
copper wire;
wire mesh;
the presence of the inverter itself.

Steel wire rod cut into small pieces. One end of the polymer pipe is covered with a mesh, and metal pieces of wire are loaded into the other. The second end is also covered with a mesh. On top of the pipe is created induction winding, what is it used for copper wire. The ends of this winding are well insulated and connected to the output of the inverter. As soon as the device is turned on, an electromagnetic field is created from the coil, which ensures the appearance of eddy currents in the core. This will cause it to heat up, so the water flowing through the pipe will begin to heat up. This creates an ideal design for a kitchen or other room, and its maintenance and repair are considered simple.

It is best to review before starting work training video so as not to make mistakes. After creating the equipment, you can install it in the desired room. It can be intended not only for the furnace, but even for the kitchen. It is important to choose a room where you can easily care for the stove and carry out its repairs.

The very principle of operation of an induction furnace is that heat for melting is obtained from electricity, which is generated by an alternating magnetic field. In such furnaces, energy is converted from electromagnetic, then into electrical and ultimately into heat. How to make an induction furnace with your own hands?

Such furnaces are divided into two types:

Crucible. In such furnaces, the inductor and the core are located inside the metal. This type of furnace is used in industrial smelters for melting copper, aluminum, cast iron, steel, as well as in jewelry factories for melting precious metals.
Duct. In this type of furnace, the inductor and the core are located around the metal.

Compared to boilers or other stoves, induction stoves have a number of advantages:

instantly warm up;
focus energy in a given range;
environmentally friendly device and relative safety;
there is no waste;
huge possibilities for adjusting temperature and capacity;
homogeneity of the metal that is melting.

Induction furnaces are also used for heating. This is a convenient and at the same time silent heating method.

Does not require a special room for the boiler. Scale does not accumulate on the heating element, and for circulation through heating system You can use any liquid, be it oil, water or others. The stove is also durable, as it wears out minimally. As mentioned earlier, it is very environmentally friendly, because there are no harmful emissions into the air, and also meets all fire safety requirements.

Collection of information

A person who understands how to read and understand an electrical diagram will not find it difficult to figure out how to make an induction furnace like this. On the Internet you will see dozens, or even hundreds of options for making various induction furnaces using household trash, for example, from an old microwave or a welding inverter.

Be sure to remember that electricity- a dangerous thing. And to make an induction furnace, you need to have an idea of what heating using induction is. It is advisable to have someone with you who understands at least the basics of electrical engineering or has experience working with electrical equipment.

Principle of operation

The basis of the operation of such a stove is the extraction of heat from an electric current, which produces an alternating magnetic field using an inductor. It turns out that we get heat first from electromagnetic energy, and then from electrical energy. The closedness of the currents that flow through the turns of the inductor (inductor) generates heat and warms the metal from the inside.

Such a stove can have a simplified version and run from a 220V home network. But this requires a rectifier, that is, an adapter.

Furnace structure

The design of an induction device is similar to a transformer. In it, the primary winding is powered by alternating current, and the secondary winding serves as a heated body.

The simplest inductor is considered to be an insulated conductor (shaped like a spiral or core), which is located on the surface of a metal pipe or inside it.

Here are some nodes that work by induction:

inductor;
melting furnace compartment;
a heating element for a heating furnace;
generator;
frame.

An induction furnace is used for melting non-ferrous and ferrous metals. Units of this operating principle are used in the following areas: from the finest jewelry making to large-scale industrial smelting of metals. This article will discuss the features of various induction furnaces.

Induction furnaces for metal melting

Principle of operation

Induction heating is the basis for the operation of the furnace. In other words, electric current creates an electromagnetic field and heat is obtained, which is used on an industrial scale. This law of physics is studied in the last grades secondary school. But the concept of an electric unit and electromagnetic induction boilers should not be confused. Although the basis of work here and there is electricity.

How does this happen

The generator is connected to an alternating current source, which enters it through an inductor located inside. The capacitor is used to create an oscillation circuit, which is based on a constant operating frequency to which the system is tuned. When the voltage in the generator increases to a limit of 200 V, the inductor creates an alternating magnetic field.

The circuit is closed, most often, through a ferromagnetic alloy core. The alternating magnetic field begins to interact with the workpiece material and creates a powerful flow of electrons. After the electrically conductive element enters into inductive action, the system experiences occurrence of residual stress, which in the capacitor contributes to the occurrence of eddy current. Eddy current energy is converted into thermal energy inductor and the desired metal is heated to high melting temperatures.

The heat produced by the inductor is used:

for melting soft and hard metals;
for surface hardening metal parts(for example, a tool);
for thermal treatment of already produced parts;
household needs (heating and cooking).

Brief characteristics of various furnaces

Types of devices

Induction crucible furnaces

It is the most common type of induction heating furnace. Distinctive feature, different from other types is that in it an alternating magnetic field appears in the absence of a standard core. Cylinder shaped crucible located inside the inductor cavity. The furnace, or crucible, is made of a material that perfectly resists fire and is connected to alternating electric current.

Positive aspects

Crucible units include to environmentally friendly heat sources, environment not polluted by metal melting.

There are disadvantages in the operation of crucible furnaces:

during technological processing, slags at low temperatures are used;
The produced lining of crucible furnaces has low resistance to destruction, this is most noticeable during sudden temperature changes.

The existing disadvantages do not pose any particular difficulties; the advantages of a crucible induction unit for melting metal are obvious and have made this type of device popular and in demand among a wide range of consumers.

Channel induction melting furnaces

This type is widely used in the smelting of non-ferrous metals. Effectively used for copper and copper alloys based on brass, cupronickel, bronze. Aluminum, zinc and alloys containing these metals are actively melted in channel units. The widespread use of furnaces of this type is limited due to the inability to provide a fracture-resistant lining on the inner walls of the chamber.

Molten metal in channel induction furnaces undergoes thermal and electrodynamic movement, which ensures constant homogeneity of mixing of alloy components in the furnace bath. Using duct furnaces inductive principle justified in cases where special requirements are imposed on the molten metal and manufactured ingots. The alloys are of high quality in terms of gas saturation coefficient and the presence of organic and synthetic impurities in the metal.

Channel induction furnaces operate like a mixer and are designed to level the composition, maintain a constant process temperature, and select the pouring speed into crystallizers or molds. For each alloy and casting composition, there are parameters for a special charge.

Advantages

the alloy is heated in the lower part, to which there is no air access, which reduces evaporation from the upper surface, heated to a minimum temperature;
channel furnaces are classified as economical induction furnaces, since the melting that occurs is ensured by a low consumption of electrical energy;
the furnace has a high efficiency due to the use of a closed loop magnetic wire;
Constant circulation of molten metal in the furnace accelerates the melting process and promotes uniform mixing of alloy components.

Flaws

the durability of the stone internal lining decreases when high temperatures are used;
the lining is destroyed when melting chemically aggressive alloys of bronze, tin and lead.
when melting contaminated low-grade charge, the channels become clogged;
the surface slag in the bath does not heat up to a high temperature, which does not allow operations to be carried out in the gap between the metal and the shelter and to melt chips and scrap;
channel units do not tolerate interruptions in operation, which forces them to constantly store a significant amount of liquid alloy in the furnace mouth.

Complete removal of molten metal from the furnace leads to its rapid cracking. For the same reason, it is impossible to perform a quick conversion from one alloy to another, you have to make several intermediate melts, called ballast.

Vacuum induction furnaces

This type is widely used for melting high quality steels and heat-resistant nickel, cobalt and iron alloys. The unit successfully copes with the melting of non-ferrous metals. Glass is boiled in vacuum units, parts are treated with high temperature, produce single crystals.

The oven is classified as high frequency generator, located in an inductor isolated from the external environment, passing a high-frequency current. To create a vacuum, air masses are pumped out of it. All operations for introducing additives, loading the charge, and dispensing metal are carried out by automatic mechanisms with electrical or hydraulic control. Alloys with small admixtures of oxygen, hydrogen, nitrogen, and organics are obtained from vacuum furnaces. The result is far superior to open induction ovens.

Heat-resistant steel from vacuum furnaces used in tool and weapons production. Some nickel alloys containing nickel and titanium are chemically active, and it is problematic to obtain them in other types of furnaces. Vacuum furnaces perform metal pouring by rotating the crucible in the internal space of the casing or by rotating the chamber with a fixed furnace. Some models have an opening hole in the bottom to drain metal into an installed container.

Crucible furnaces with transistor converter

Used for limited weight non-ferrous metals. They are mobile, light in weight and can be easily moved from place to place. The furnace package includes a high-voltage transistor universal converter. Allows you to select the power recommended for connecting to the network, and, accordingly, the type of converter that is needed in this case with changing the weight parameters of the alloy.

Transistor Induction Furnace Widely used for metallurgical processing. With its help, parts are heated in blacksmithing and metal objects are hardened. Crucibles in transistor furnaces are made of ceramics or graphite; the former are designed to melt ferromagnetic metals such as cast iron or steel. Graphite is installed to melt brass, copper, silver, bronze and gold. They melt glass and silicon. Aluminum melts well using cast iron or steel crucibles.

What is the lining of induction furnaces

Its purpose is to protect the furnace casing from the destructive effects of high temperatures. A side effect is the preservation of heat, therefore process efficiency increases.

The crucible in the design of an induction furnace is made in one of the following ways:

by the method of excavation in small-volume ovens;
by the printed method from refractory material in the form of masonry;
combined, combining ceramics and a buffer layer between the masonry and the indicator.

The lining is made of quartzite, corundum, graphite, fireclay graphite, magnesite. Additives are added to all these materials to improve the characteristics of the lining, reduce volume changes, improve sintering, and increase the resistance of the layer to aggressive materials.

To select a particular material for lining take into account a number of accompanying conditions, namely, the type of metal, the price and refractory properties of the crucible, the service life of the composition. A properly selected lining composition should provide technical requirements to carry out the process:

obtaining high quality ingots;
the largest amount of full melting without repair work;
safe work of specialists;
stability and continuity of the smelting process;
obtaining quality material when using economical quantity resources;
use of common materials for lining at a low price;
minimal impact on the surrounding space.

The use of induction furnaces allows you to obtain alloys and metals of excellent quality with a minimum content of various impurities and oxygen, which increases their use in complex areas of production.

Induction furnaces are widely used in the metallurgical industry. Such stoves are often made independently. To do this, you need to know their operating principle and design features. The operating principle of such furnaces was known two centuries ago.

Induction furnaces are capable of solving the following problems:

Melting metal.
Heat treatment of metal parts.
Purification of precious metals.

Such functions are available in industrial ovens. For domestic conditions and room heating, there are specially designed stoves.

Operating principle

An induction furnace works by heating materials by using the properties of eddy currents. To create such currents, a special inductor is used, which consists of an inductor with several turns of wire of large cross-section.

An AC power supply is supplied to the inductor. In an inductor alternating current creates a magnetic field that changes with the network frequency and penetrates inner space inductor. When any material is placed in this space, eddy currents arise in it, heating it.

The water in the operating inductor heats up and boils, and the metal begins to melt when the appropriate temperature is reached. Induction furnaces can be roughly divided into types:

Furnaces with magnetic core.
Without magnetic core.

The first type of furnace contains an inductor enclosed in metal, which creates a special effect that increases the density of the magnetic field, so heating is carried out efficiently and quickly. In furnaces without a magnetic core, the inductor is located outside.

Types and features of furnaces

Induction furnaces can be divided into types, which have their own operating characteristics and distinctive features. Some are used for work in industry, others are used in everyday life, for cooking.

Vacuum induction furnaces

This furnace is designed for melting and casting alloys using the induction method. It consists of a sealed chamber in which a crucible induction furnace with a casting mold is located.

In a vacuum, it is possible to ensure perfect metallurgical processes and obtain high-quality castings. Currently, vacuum production has moved to new technological processes from continuous chains in a vacuum environment, which makes it possible to create new products and reduce production costs.

Advantages of vacuum melting

Liquid metal can be kept in a vacuum for a long time.
Increased degassing of metals.
During the smelting process, you can reload the furnace and influence the refining and deoxidation process at any time.
The ability to constantly monitor and adjust the temperature of the alloy and its chemical composition during operation.
High purity of castings.
Fast heating and melting speed.
Increased homogeneity of the alloy due to high-quality mixing.
Any form of raw material.
Environmentally friendly and economical.

The operating principle of a vacuum furnace is that a solid charge is melted in a crucible in a vacuum using a high-frequency inductor and the liquid metal is purified. The vacuum is created by pumping air out. Vacuum melting achieves a large reduction in hydrogen and nitrogen.

Channel induction furnaces

Furnaces with an electromagnetic core (channel) are widely used in foundries for non-ferrous and ferrous metals as holding furnaces and mixers.

1 - Bath
2 - Channel
3 - Magnetic core
4 - Primary coil

An alternating magnetic flux passes through a magnetic circuit, a channel contour in the form of a ring of liquid metal. An electric current is excited in the ring, which heats up the liquid metal. The magnetic flux is generated by the primary winding operating on alternating current.

To enhance the magnetic flux, a closed magnetic circuit is used, which is made of transformer steel. The furnace space is connected by two holes to a channel, so when the furnace is filled with liquid metal, a closed loop is created. The oven will not be able to operate without a closed circuit. In such cases, the circuit resistance is large, and a small current flows in it, which is called current idle move.

Due to overheating of the metal and the action of the magnetic field, which tends to push the metal out of the channel, the liquid metal in the channel is constantly moving. Since the metal in the channel is heated higher than in the furnace bath, the metal constantly rises into the bath, from which metal with a lower temperature comes.

If the metal is drained below the permissible norm, then the liquid metal will be thrown out of the channel by electrodynamic force. As a result, the stove will spontaneously turn off and the electrical circuit will break. To avoid such cases, furnaces leave some metal in liquid form. It's called a swamp.

Channel furnaces are divided into:

Melting furnaces.
Mixers.
Holding ovens.

To accumulate a certain amount of liquid metal, averaging its chemical composition and holding it, mixers are used. The volume of the mixer is calculated to be no less than twice the hourly output of the oven.

Channel furnaces are divided into classes according to the location of the channels:

Vertical.
Horizontal.

According to the shape of the working chamber:

Drum induction furnaces.
Cylindrical induction furnaces.

The drum furnace is made in the form of a welded steel cylinder with two walls at the ends. Drive rollers are used to rotate the oven. To turn the oven, you must turn on the electric motor drive with two speeds and a chain drive. The engine has plate brakes.

There is a siphon on the end walls for pouring metal. There are holes for loading additives and removing slag. There is also a channel for dispensing metal. The channel block consists of a furnace inductor with V-shaped channels made into the lining using templates. During the first melting, these templates melt. The winding and core are cooled by air, the body of the unit is cooled by water.

If the channel furnace has a different shape, then the metal is released by tilting the bath using hydraulic cylinders. Sometimes the metal is squeezed out overpressure gas

Advantages of channel stoves

Low energy consumption due to low heat loss from the bath.
Increased electrical efficiency of the inductor.
Low cost.

Disadvantages of channel furnaces

The difficulty of adjusting the chemical composition of the metal, since the presence of liquid metal left in the furnace creates difficulties when switching from one composition to another.
The low speed of metal movement in the furnace reduces the capabilities of the smelting technology.

Design features

The oven frame is made of low carbon steel sheet with a thickness of 30 to 70 mm. At the bottom of the frame there are windows with attached inductors. The inductor is made in the form of a steel body, a primary coil, a magnetic circuit and a lining. Its body is made detachable, and the parts are isolated from each other by gaskets so that the body parts do not create a closed loop. Otherwise, an eddy current will be created.

The magnetic core is made of 0.5 mm special electrical steel plates. The plates are insulated from each other to reduce losses from eddy currents.

The coil is made of copper conductor with a cross-section depending on the load current and cooling method. With air cooling, the permissible current is 4 amperes per mm 2, with water cooling the permissible current is 20 amperes per mm 2. A screen is installed between the lining and the coil, which is cooled with water. The screen is made of magnetic steel or copper. A fan is installed to remove heat from the coil. To obtain exact dimensions channel, apply the template. It is made in the form of a hollow steel casting. The template is placed in the inductor until it is filled with refractory mass. It is located in the inductor during heating and drying of the lining.

For lining, refractory masses of wet and dry types are used. Wet masses are used in the form of printed or poured materials. Poured concrete is used when the inductor has a complex shape, if it is impossible to compact the mass throughout the entire volume of the inductor.

The inductor is filled with this mass and compacted with vibrators. Dry masses are compacted with high-frequency vibrators, rammed masses are compacted with pneumatic tampers. If cast iron is smelted in a furnace, the lining is made of magnesium oxide. The quality of the lining is determined by the temperature of the cooling water. The most effective method of checking the lining is to check the value of inductive and active resistance. These measurements are carried out using control instruments.

The electrical equipment of the furnace includes:

Transformer.
A battery of capacitors to compensate for electrical energy losses.
Choke for connecting a 1-phase inductor to a 3-phase network.
Control panels.
Power cables.

In order for the furnace to function normally, the power supply is connected to 10 kilovolts, which has 10 voltage steps on the secondary winding to regulate the power of the furnace.

Lining packing materials contain:

48% dry quartz.
1.8% boric acid, sifted through a fine sieve with 0.5 mm mesh.

The lining mass is prepared in dry form using a mixer, and then sifted through a sieve. The prepared mixture should not be stored for more than 15 hours after preparation.

The crucible is lined using compaction with vibrators. Electric vibrators are used for lining large furnaces. Vibrators are immersed into the template space and compact the mass through the walls. When compacting, the vibrator is moved by a crane and rotated vertically.

Crucible induction furnaces

The main components of a crucible furnace are an inductor and a generator. To make an inductor, a copper tube is used in the form of wound 8-10 turns. The shapes of inductors can be of various types.

This type of oven is the most common. There is no core in the furnace design. A common form of oven is a cylinder made of fire-resistant material. The crucible is located in the cavity of the inductor. AC power is supplied to it.

Advantages of crucible furnaces

Energy is released when the material is loaded into the oven, so auxiliary heating elements are not needed.
High homogeneity of multicomponent alloys is achieved.
In the furnace, you can create a reduction or oxidation reaction, regardless of the pressure.
High furnace performance due to increased power density at any frequency.
Interruptions in metal melting do not affect the efficiency of work, since heating does not require a lot of electricity.
Possibility of any settings and simple operation with the possibility of automation.
There is no local overheating, the temperature is equalized throughout the entire volume of the bath.
Fast melting, allowing the creation of high-quality alloys with good homogeneity.
Environmental Safety. External environment is not exposed to any harmful effects from the oven. Melting also does not harm the environment.

Disadvantages of crucible furnaces

Low temperature of the slag used for processing the melt surface.
Low durability of the lining under sudden temperature changes.

Despite the existing disadvantages, crucible induction furnaces have gained great popularity in production and in other areas.

Induction furnaces for space heating

Most often, such a stove is installed in the kitchen. The main part of its design is welding inverter. The furnace design is usually combined with a water heating boiler, which makes it possible to heat all rooms in the building. It is also possible to connect hot water supply to the building.

The operating efficiency of such a device is low, however, such equipment is often used for heating a house.

The design of the heating part of an induction boiler is similar to a transformer. The outer circuit is the windings of a kind of transformer that are connected to the network. The second internal circuit is a heat exchange device. The coolant circulates in it. When power is connected, the coil creates an alternating voltage. As a result, currents are induced inside the heat exchanger, which heat it. The metal heats the coolant, which usually consists of water.

The operation of household induction cookers is based on the same principle, in which cookware made of a special material acts as a secondary circuit. Such a stove is much more economical than conventional stoves due to the absence of heat losses.

The boiler water heater is equipped with control devices that make it possible to maintain the coolant temperature at a certain level.

Heating with electricity is an expensive pleasure. It cannot compete with solid fuel and gas diesel fuel And liquefied gas. One of the methods to reduce costs is to install a heat accumulator, as well as connect the boiler at night, since at night there is often a preferential charge for electricity.

In order to make a decision about installing an induction boiler for your home, you need to get advice from professional heating engineering specialists. An induction boiler has virtually no advantages over a conventional boiler. The disadvantage is the high cost of the equipment. A conventional boiler with heating elements is sold ready for installation, but an induction heater requires additional equipment and settings. Therefore, before purchasing such an induction boiler, it is necessary to make careful economic calculations and planning.

Induction furnace lining

The lining process is necessary to ensure protection of the furnace body from exposure to elevated temperatures. It makes it possible to significantly reduce heat loss and increase the efficiency of metal melting or material heating.

Quartzite, which is a modification of silica, is used for lining. There are certain requirements for lining materials.

Such a material should provide 3 zones of material states:

Monolithic.
Buffer.
Intermediate.

Only the presence of three layers in the coating can protect the furnace casing. The lining is negatively affected by improper placement of the material, poor quality of the material and difficult operating conditions of the furnace.

For melting metal on a small scale, some kind of device is sometimes necessary. This is especially acute in a workshop or in small-scale production. The most efficient furnace at the moment is a metal melting furnace with an electric heater, namely an induction furnace. Due to the peculiarities of its structure, it can be effectively used in blacksmithing and become an indispensable tool in the forge.

Induction furnace structure

The oven consists of 3 elements:

1. Electronic and electrical part.
2. Inductor and crucible.
3. inductor cooling system.

In order to assemble a working furnace for melting metal, it is enough to assemble a working electrical circuit and an inductor cooling system. The simplest version of metal melting is shown in the video below. Melting is carried out in the counter electromagnetic field of the inductor, which interacts with induced electro-eddy currents in the metal, which holds a piece of aluminum in the space of the inductor.

In order to effectively melt metal, large currents and high frequencies of the order of 400-600 Hz are required. The voltage from a regular 220V home socket is sufficient to melt metals. It is only necessary to turn 50 Hz into 400-600 Hz.
Any circuit for creating a Tesla coil is suitable for this.

Tin cans and other scrap are recyclable! How to make a furnace for melting aluminum with your own hands

I liked the following 2 circuits on the GU 80, GU 81(M) lamp the most. And the lamp is powered by an MOT transformer from a microwave oven.

These circuits are intended for a Tesla coil, but they make an excellent induction furnace; instead of the secondary coil L2, it is enough to place a piece of iron in the internal space of the primary winding L1.

The primary coil L1 or inductor consists of a coil of 5-6 turns copper tube, at the ends of which threads are cut to connect the cooling system. For levitation melting, the last turn should be done in the opposite direction.
Capacitor C2 in the first circuit and an identical one in the second sets the frequency of the generator. At a value of 1000 picoFarads, the frequency is about 400 kHz. This capacitor must be a high-frequency ceramic capacitor and designed for high voltage of about 10 kV (KVI-2, KVI-3, K15U-1), other types are not suitable! It's better to use K15U. Capacitors can be connected in parallel. It is also worth taking into account the power for which the capacitors are designed (this is written on their case), take it with a reserve. the other two capacitors KVI-3 and KVI-2 heat up during prolonged operation. All other capacitors are also taken from the KVI-2, KVI-3, K15U-1 series; only the capacitance changes in the characteristics of the capacitors.
Here is a schematic diagram of what should happen. I circled 3 blocks in frames.

The cooling system is made of a pump with a flow of 60 l/min, a radiator from any VAZ car, and I placed a regular home cooling fan opposite the radiator.

Be the first to leave a comment

Masters of their craft: we produce a melting furnace

A smelter is a large or portable structure in which a quantity of non-ferrous metal can be melted. The induction melting furnace is widely known. In production conditions, large quantities of induction melting furnaces are installed in special rooms to melt metal in large quantities. They melt metal from which many parts for motorcycles, cars, and tractors are cast. To melt up to 5 kg of aluminum. you can build your own induction melting furnaces, solid fuel and gas installations. They all work great. How and from what can you make a home melting pot?

We build our own smelting furnace

The installation for melting metal (Fig. 1) is assembled from bricks. It must be fireproof. Fireclay clay is used as a binder. To fire the device with coal, forced air is needed. For this, a special channel must be left in the lower half of the unit for air access. A grate is located under this channel. This is a special cast iron grate on which coal or coke is laid out. The grate can be used from an old stove or purchased at the market or at a hardware store. For strength, some scald the finished structure with a metal belt. The brick can be laid on its edge.

A smelting furnace cannot do without a crucible. You can use a cast iron cauldron instead. You can look for it on the farm. It will be good if it turns out to be enameled. The crucible is installed closer to the burning coke. All that remains is to install a fan as forced air, light the coke and start smelting. The oven is ready with your own hands. It can be used for melting cast iron, copper, bronze, aluminum.

Construction of a tabletop oven

From simple materials you can build gas or electrical devices, which fit perfectly on a table or workbench. To work you will need:

Asbestos has been banned for home use in recent years, so it can be replaced with tiles or cement. The sizes depend on the wishes of the owner. The power of the electrical network and the output voltage of the transformer play a big role here. It is enough to apply a voltage of 25 V to the electrodes. For an industrial transformer used in welding work, this voltage is usually 50-60 V. In this case, the distance between the electrodes must be increased. Much is done by experience. As a result, melting 60-80 g of metal is a good result.

It is better to make electrodes from brushes from a fairly powerful electric motor. They have a very convenient current supply wire. You can grind them yourself. Big problems there should be no problem with searching for material. IN homemade product you need to drill holes on the side with a diameter of 5-6 mm, insert a copper stranded wire about 5 mm thick into them, and carefully hammer in a nail to secure the wire. All that remains is to make a notch with a file, it will help improve contact with the graphite in powder form. The inside of the oven is lined with mica. This is an excellent heat insulator. The outside walls of the oven are reinforced with tiles.

To power the furnace, you can take a transformer that lowers the mains voltage to 52 V. The mains winding is wound with 620 turns of wire Ø1 mm. The step-down winding is wound with a 4.2x2.8 mm wire having fiberglass insulation. Number of turns #8212; 70. The furnace is connected to the transformer with wires with a cross section of 7-8 mm² in good insulation. The finished installation must be turned on for a while so that all organic inclusions burn out. The oven was assembled by hand.

using a scoop or spatula, pour in graphite and make a hole in it;
a material blank is placed in the hole;
precious metals must be placed in a glass ampoule;
tin and aluminum are placed in a separate iron cup;
For alloys, the refractory metal is melted first, then the low-melting metal.

You cannot melt magnesium, zinc, cadmium, or silver contacts in such furnaces.

Cadmium burns out when melted, producing toxic yellow smoke.

When working with the installation, you must follow safety precautions:

Can't be allowed short circuits in the wires.
The power switch must be located near the operator.
Do not leave the device unattended during operation.
Nearby there is always a container filled with water in which the workpieces are cooled.
When melting cast iron and other metals, you must use safety glasses and gloves.

If desired, you can make gas installations. They are well suited for melting small batches of non-ferrous metal. Induction melting furnaces are capable of melting any metal. They can be used as conventional installations for working with non-ferrous and precious metals, as melting and holding furnaces in production. They are suitable for various needs: for heating metals, for making alloys of several metals, for melting cast iron.

You can melt a small piece of iron in a self-assembled induction furnace. This is the most efficient device that operates from a 220V home outlet. The stove is useful in a garage or workshop, where it can simply be placed on a desktop. There is no point in buying it, since an induction furnace can be assembled with your own hands in a couple of hours, if a person knows how to read electrical diagrams. It is not advisable to do without a diagram, because it gives a complete picture of the device and allows you to avoid errors when connecting.

Induction furnace diagram

Induction Furnace Parameters

No comments yet!

How to properly assemble an induction furnace?

To help the repairman

For your review, we offer electrical circuit diagrams for electric stoves for self-repair!

Russian and imported slabs are presented, which have not changed for years.
To view larger, click on the picture.

Main elements and components of the stove: heating element E1 (in the first burner), E2 (in the second burner), E3-E5 (in the oven), switching unit consisting of switches S1-S4, thermal relay F type T-300, indicators HL1 and HL (gas discharge for indicating the operation of the heating element), HL3 (incandescent type for illuminating the oven). The power of each heating element is about 1 kW

To adjust the power and degree of heating of the heating element of the oven, a 4-position switch S1 is used. When its handle is set to the first position, contacts P1-2 and P2-3 are closed. In this case, the following will be connected to the network using a plug: heating element E3 in series with parallel-connected heating elements E2 and E3. The current will flow along the path: lower contact of the plug XP, F, P1-2, E4 and E5, E3, P2-3, upper XP plug contact. Since heating element E3 is connected to heating element E4 and E5 in series, the circuit resistance will be maximum, and the power and degree of heating will be minimal. In addition, the neon indicator HL1 will light up due to the passage of current through the circuit: the lower contact of the XP plug, F, P1-2, E4 and E5, R1, HL1, the upper contact of XP.

Connecting Dream 8 nodes:

In the second position, contacts P1-1, P2-3 are switched on. In this case, the current will flow through the circuit: the lower contact of the XP plug, F, P1-1, E3, P2-3, the upper contact of XP. In this situation, only one E3 heating element will work and the power will be greater due to a decrease in the total resistance at a constant mains voltage of 220V.

In the third position of switch S1, contacts P1-1, P2-2 will close, which will lead to connection to the network only of parallel-connected heating elements E4 and E5. Switch S4 is used to turn on the oven lighting lamp HL3.

5.Electra 1002

H1, H2 - tubular burners, H3 - cast iron burner 200mm, H4 - cast iron burner 145mm, P1, P2 - stepless power regulators, P3, P4 - seven-position power switches, PSh - three-stage oven switch, P5 - blocking switch, L1.... L4 - signal lamps for turning on the burners, L5 - signal lamp for turning on the oven or grill heaters, L6 - signal lamp for reaching the set temperature in the oven, H5, H6 - oven heaters, H7 - grill, T - temperature regulator, B - key switch, L7 – oven lighting lamp, M – gear motor.

6. BURNER SWITCHES Combustion, Нansa, Electra, Lysva:

Nuances of repairing electrical panels Bosch Samsung Electrolux

Replacing a stove burner yourself

Table of contents:

Principle of operation
Induction Furnace Parameters
Features of inductor operation

You can melt a small piece of iron in a self-assembled induction furnace.

How to make a crucible or melting furnace with your own hands

This is the most efficient device that operates from a 220V home outlet. The stove is useful in a garage or workshop, where it can simply be placed on a desktop. There is no point in buying it, since an induction furnace can be assembled with your own hands in a couple of hours, if a person knows how to read electrical diagrams. It is not advisable to do without a diagram, because it gives a complete picture of the device and allows you to avoid errors when connecting.

Working principle of induction furnace

A homemade induction furnace for melting a small amount of metal does not require large dimensions or such a complex device as industrial units. Its operation is based on the generation of current by an alternating magnetic field. The metal is melted in a special piece called a crucible and placed in an inductor. It is a spiral with a small number of turns of a conductor, for example, a copper tube. If the device is used for a short time, the conductor will not overheat. In such cases, it is sufficient to use copper wire.

A special generator launches powerful currents into this spiral (inductor), and an electromagnetic field is created around it. This field in the crucible and in the metal placed in it creates eddy currents. It is they who heat the crucible and melt the metal due to the fact that it absorbs them. It should be noted that the processes occur very quickly if you use a crucible made of non-metal, for example, fireclay, graphite, quartzite. A homemade furnace for melting provides a removable crucible design, that is, metal is placed in it, and after heating or melting it is pulled out of the inductor.

Induction furnace diagram

The high-frequency generator is assembled from 4 electronic tubes (tetrodes), which are connected to each other in parallel. The heating rate of the inductor is controlled by a variable capacitor. Its handle extends outward and allows you to adjust the capacitance of the capacitor. The maximum value will ensure that the piece of metal in the coil is heated to red in just a few seconds.

Induction Furnace Parameters

The effective operation of this device depends on the following parameters:

generator power and frequency,
amount of losses in eddy currents,
the rate of heat loss and the amount of these losses into the surrounding air.

How to select the component parts of the circuit in order to obtain sufficient conditions for melting in the workshop? The generator frequency is preset: it should be 27.12 MHz if the device is assembled with your own hands for use in a home workshop. The coil is made of a thin copper tube or wire, PEV 0.8. It is enough to make no more than 10 turns.

Electronic lamps should be used with high power, for example, 6p3s brand. The scheme also provides for the installation of an additional neon lamp. It will serve as an indicator that the device is ready. The circuit also provides for the use of ceramic capacitors (from 1500V) and chokes. Connection to a home outlet is made through a rectifier.

Externally, a homemade induction furnace looks like this: a generator with all the details of the circuit is attached to a small stand on legs. An inductor (spiral) is connected to it. It should be noted that this option for assembling a homemade melting device is applicable for working with a small volume of metal. An inductor in the form of a spiral is the easiest to make, so for a homemade device it is used in this form.

Features of inductor operation

However, there are many different modifications of the inductor. For example, it can be made in the shape of a figure eight, a trefoil, or any other shape. It should be convenient for placing the material for heat treatment. For example, a flat surface is most easily heated by coils arranged in a snake shape.

In addition, it tends to burn out, and in order to extend the service life of the inductor, it can be insulated with heat-resistant material. For example, pouring a refractory mixture is used. It should be noted that this device is not limited to only copper material wires. You can also use steel wire or michrome. When working with an induction furnace, be aware of its thermal hazards. If accidentally touched, the skin gets severely burned.

Homemade melting crucible electric furnace.

So, a furnace for melting metal. Here I didn’t invent anything much, but simply tried to make a device, if possible from ready-made components and, if possible, without allowing any slack in the manufacturing process.
At the stove top part Let's call it a melting pot, the bottom one is the control unit.
Don't let the white box on the right scare you - this is, in general, an ordinary transformer.
Main parameters of the furnace:
— oven power - 1000 W
- crucible volume - 62 cm3
— maximum temperature - 1200 °C

Melting

Since my goal was not to waste time on experiments with corundum-phosphate binders, but to save time by using ready-made components, I used a ready-made heater from YASAM, as well as a ceramic muffle working in tandem with it.

Heater: fechral, wire diameter 1.5 mm, rods with a diameter of 3 mm are welded to the terminals. Resistance 5 ohms. The presence of a muffle is mandatory, since the wires inside the heater are bare. Heater size Ф60/50х124 mm. Muffle dimensions Ф54.5/34х130 mm. We make a hole in the bottom of the muffle for the elevator rod.
The body of the melter is made of standard stainless steel. pipe 220/200, machined to an acceptable wall thickness. The height was also taken for a reason. Since our lining will be fireclay brick, the height is taken taking into account the three thicknesses of the brick. It's time to post the assembly drawing. In order not to clutter up the page, I will not publish here, but will give links: Part 1, Part 2.
The first drawing does not show the lightweight fireclay washer on which the crucible stands; the height of the washer depends on the crucible used. In the center of the washer there is a hole for the rod. The rod is pointed and in the lower position does not reach the crucible.
As I already wrote, the furnace lining is made of lightweight fireclay bricks ШЛ 0.4 or ШЛ 0.6, standard size No. 5. Its dimensions are 230x115x65 mm. Brick is easy to process with saws and sandpaper. The saw, however, won’t last long :) Processing fireclay bricks. On the right is the original brick :)
For straight cuts - a hacksaw for wood, for curved cuts - a homemade saw made from a hacksaw blade with large teeth, with a reduced (ground) width of the blade.

When manufacturing the lining, one should observe simple rules:
- do not use any mortar to fasten the parts. Everything is dry. It'll break anyway
— parts of the lining should not rest anywhere. There must be slack, gaps
— if you make large parts of the lining from another material, it is better to divide it into smaller parts. It will still split. Therefore, you better do it.

For the thermocouple, we make a hole in the third layer, and in the second and first layers we make a gap between the heater and the lining. The gap is such that the thermocouple is pushed in tightly, as close to the heater as possible. You can use a purchased thermocouple at YASAM, but I use homemade ones. It’s not that I’m sorry for the money (although they are quite expensive there), I just basically leave the junction bare for better thermal contact. Although there is a risk of burning the input circuits of the regulator.

Control block

In the control unit, the lower and top cover equipped with grilles for cooling the heater terminals. Still, the diameter of the leads is 3 mm. In addition, heat radiation through the bottom of the melting pot is also present. There is no need to cool the regulator - 10 watts in total. At the same time, let’s cool the cold ends of the thermocouple. Control unit with temperature controller Termodat-10K2. At the top right is the power switch. At the top left is a crucible lift lever with a lift rod (stainless steel electrode Ф3mm).

Why did I choose Termodat as the regulator? Had an affair with Aries, but after one winter in unheated room, his firmware crashed. The thermodata has already withstood several winters and retained not only the firmware, but also the settings.

Crucible furnace: design options, DIY production

In addition, the body is metal, indestructible. (We should at least take a bottle from the Perm residents for advertising :)
In addition, you can also get a power element from them - Triac Control Unit BUS1-B01. This block is designed to work specifically with Thermodats.
The instructions for Termodat-10K2 are here.

Electric furnace diagram. The thick line shows high-current circuits. They use a wire of at least 6 mm2.

I'll tell you about the transformer later. Now about the control unit. It is turned on by the T1 toggle switch and is protected by a 0.25 A fuse. In addition, a surge filter is provided to power the regulator, which is located in the transformer housing. The TS142-80 triac is used as a power element (1420 volts, 80 amperes, written in CHIP and DIP). I placed the triac on the radiator, but as practice has shown, it hardly heats up. Don't forget to isolate the triac from the case. Either mica or ceramics. Either the triac itself, or assembled with a radiator.

In the photo behind the Thermodat there is a fan power supply. I then added it for the fan, which I placed on the bottom grille. The power supply is the simplest - trans, bridge and capacitor, produces 12 volts. Computer fan.
Heater output. Through the grille there is an outlet in a ceramic tube. To connect to the terminal, I used a cross-drilled bolt.
Inserting a thermocouple into the control unit. If you do not have such a ceramic straw, spit out the required amount in YASAM.

Please note - the installation is made with a regular installation wire, high-current circuits are multi-core of at least 6 mm2, thermocouple ends are directly into the terminal block. The BUS in its factory form does not fit, I had to remove the cover (and who has it easy now? ;). The rest can be seen in the photo.

Transformer.

Despite such a formidable appearance, this device is a regular 1 kW transformer. He just changed several professions before (graphite smelter, welder, etc.) and acquired a housing, an automatic switch, an indicator of the current consumed from the network and other wonderful things.

Of course, you don’t have to fence all this, a simple kilowatt trance under the table is enough. The basis of everything is a transformer made of U-shaped iron. Depending on the need, I rewind it without disassembling or changing the primary.
Why do you need a transformer anyway? The fact is that in order for the heater to work for an acceptable amount of time, the diameter of the wire must be as thick as possible. After analyzing this table, we can draw a disappointing conclusion - the wire should be as thick as possible. And this is no longer 220 volts.

Therefore, you will not find heaters designed for 220 volts in serious devices. Directly, if you connect this heater to the network, the power consumption will be around 9 kW. You will plant a network throughout the house, and such a blow will be fatal for the heater. That's why voltage limiting circuits are used. For me, the most convenient way is to use a transformer.
So, primary: - 1.1 Volts per turn
— Idle current 450 mA
Secondary: - for a load of 5 ohms and a power of 1000 W, the voltage will be 70 Volts
— secondary current 14 A, wire 6 mm2, wire length 28 m.
Of course, this heater will not last forever. But I can replace it by finding a suitable wire and quickly rewinding the secondary.
If you read the instructions for Thermodat, then there is the possibility of limiting the maximum power. But this will not suit us, because we are talking about the average power per heater. In the distributed pulse mode, like ours, the pulses will be all 9 kW and we risk getting a pandemonium with light and music. And on the neighbors too, because the machines in the entrance are also designed for medium power.

For those who don’t like to read instructions for a long time, I’m posting a cheat sheet with coefficients and settings for a specific oven. After setting up the Thermodat, turn on the trance and go ahead.
Due to the inertia of the pointer, the indicator of the current consumed from the network also shows the average power. While the heater is cold, the current will be closer to 5 amperes, as it warms up slightly lower (due to the increase in heater resistance). As it approaches the set point, it will drop almost to zero (PID controller operation).

Load the crucible full with a bronze crowbar and close the lid. The inside of the lid is lined with lightweight fireclay on mortar for fireplaces and stoves. For those who are especially curious (I am one myself), there is a window in the lid covered with mica.

The temperature is over 1000, but the surface of the melting pot has not yet heated up. This indicates the quality of the lining. After 30-40 minutes, the contents of the crucible melted.
After finishing the melting, we press the elevator lever, after which we can already pick up the crucible with a grip. The photo shows a notch in the upper part of the crucible just for a secure grip.

P.S. About the crucibles. YASAM equips its furnaces with graphite crucibles that work with these heaters. If you work with gold and silver, it makes sense to buy them. But I am against these bourgeois excesses. The fact is that stainless pipeФ32/28 miraculously coincides with the diameter of the graphite crucible. You can draw your own conclusion 😉

We insulate the heater leads from the body with ceramic tubes. Ceramic tubes - from fuses, maybe from resistors.

The top row of bricks is flush with the edge of the body. Don't forget the hole for the elevator rod.

Third layer of lining. In this layer we make holes for the heater leads and for the thermocouple (pictured).

Second layer of lining. Cut for the top outlet of the heater.

In induction furnaces, the metal is heated by currents excited in the unalternating field of the inductor. Essentially, induction furnaces are also resistance furnaces, but differ from them in the way they transfer energy to the heated metal. Unlike resistance furnaces, electrical energy in induction furnaces is converted first into electromagnetic energy, then again into electrical energy, and finally into thermal energy.

With induction heating, heat is released directly in the heated metal, so the use of heat is the most complete. From this point of view, these ovens are the most advanced type of electric ovens.

There are two types of induction furnaces: coreless and coreless crucible. In core furnaces, the metal is contained in an annular groove around the inductor, within which the core passes. In crucible furnaces, a crucible with metal is located inside the inductor. It is impossible to use a closed core in this case.

Due to a number of electrodynamic effects that occur in the metal ring around the inductor, the specific power of channel furnaces is limited to certain limits. Therefore, these furnaces are used primarily for melting low-melting non-ferrous metals and only in some cases are used for melting and overheating cast iron in foundries.

The specific power of induction crucible furnaces can be quite high, and the forces arising from the interaction of magnetic furnaces of metal and inductor have a positive effect on the process in these furnaces, promoting metal mixing.

How to assemble an induction furnace - diagrams and instructions

Coreless induction furnaces are used for smelting special, especially low-carbon steels and alloys based on nickel, chromium, iron, and cobalt.

An important advantage of crucible furnaces is their simplicity of design and small dimensions. Thanks to this, they can be completely placed in a vacuum chamber and it is possible to process the metal with vacuum during the melting process. As vacuum steelmaking units, induction crucible furnaces are becoming increasingly widespread in the metallurgy of high-quality steels.

Figure 3. Schematic representation of an induction channel furnace (a) and transformer (b)

Induction furnaces. Melting technology in induction furnaces

INDUCTION CROUCHABLE FURNACES.

Alloys of ferrous and non-ferrous metals and pure metals (cast iron, steel, bronze, brass, copper, aluminum) are smelted in these furnaces. By current frequency: 1) Furnaces with industrial frequency 50 Hz. 2) Mid frequency up to 600 Hz. (up to 2400 Hz also included). 3) High frequency up to 18000 Hz.

Often ind. furnaces operate in pairs (duplex process). In the first furnace the charge is melted, in the second the Me is brought to the desired chemical level. composition or maintain Me at the required temperature until casting. Transfer of Chalk from furnace to furnace can be carried out continuously along a chute using crane buckets or buckets on an electric car. In induction furnaces, the composition of the charge changes; instead of pig iron, lightweight, low-quality materials are used (chips, lightweight scrap metal, waste from own production, i.e. trimmings).

Operating principle The charge, alternating electric current, is loaded into the crucible. the current passing through the inductor (coil) creates a magnetic field, which induces an electromotive force in the metal cage, which causes induced currents, which cause the heating and melting of the chalk. Inside the coil is a crucible made of fireproof material, which protects the inductor from the effects of liquid chalk. The primary winding is an inductor. The secondary winding and at the same time the load is Chalk in a crucible.

The efficiency of the furnace depends on the electrical resistance of Mel and on the frequency of the current. For high efficiency, it is necessary that the diameter of the charge (d crucible) be at least 3.5-7 depths of current penetration into Me-l. Approximate relationships between the crucible capacity and the current frequency for steel and cast iron. The productivity of furnaces is usually 30-40 t/hour for cast iron and steel. With an energy consumption of 500-1000 kWh/ton. For bronze, copper 15-22 t/hour, for aluminum 8-9 t/hour. Most often a cylindrical crucible is used. The magnetic flux created by the inductor passes through closed lines both inside and outside the inductor.

Depending on the method of passing the magnetic flux from the outside, there are: 1) open; 2) shielded; 3) closed oven design

At open design magnetic flux passes through the air, so structural elements (for example, a frame) are made of non-metallic or placed on long distance from the inductor. When shielding, the magnetic flux from steel structures separated by a copper screen. When closed, the magnetic flux passes through radially arranged packages of transformer steel - magnetic cores.

Diagram of an electric induction furnace: 1 - cover, 2 rotation unit, 3 - inductor, 4 - magnetic circuits, 5 - metal structure, 6 - water cooling inlets, 7 - crucible, 8 - platform

The oven turns on. nodes:Inductor, Lining, Frame, Magnetic cores, Cover, Pad, Tilt mechanisms.

Aluminum melting furnace

In addition to its main purpose, the inductor also performs the function of an electrical device that receives the fur. and thermal load from the crucible. In addition, cooling the inductor ensures the removal of heat that arises due to electrical losses, so inductors are made either in the form of a cylindrical single-layer coil, where all turns are arranged in the form of a spiral with a constant angle of inclination, or in the form of a coil in which all turns are laid in a horizontal plane , and the transitions between them are in the form of short inclined sections.

Depending on the brand of Mel and t-p level 3 types of lining are used:

1. Sour(contains > 90% SiO2) withstands 80-100 heats

2. Main(up to 85% MgO) withstands 40-50 heats for small furnaces and up to 20 heats for furnaces with a capacity >1 ton

3. Neutral(based on Al2O3 or CrO2 oxides)

Diagrams of induction melting furnaces: a - crucible, b - channel; 1 - inductor; 2 - molten metal; 3 - crucible; 4 - magnetic core; 5 - hearth stone with a heat release channel.

The padina is made of fireclay bricks for large furnaces or aspocement for small ones. Cover made of structural steel and lined from the inside. Advantages of crucible furnaces:1) Intensive circulation of the melt in the crucible; 2) The ability to create an atmosphere of any type (oxidizing, reducing, neutral) at any pressure; 3) High performance; 4) Possibility of completely draining the chalk from the furnace; 5) Ease of maintenance, possibility of mechanization and automation. Flaws: 1)Relatively low temperature slags aimed at the Mel-la mirror; 2) Relatively low durability of the lining at high temperatures of the melt and in the presence of thermal shifts.

INDUCTION CHANNEL OVEN.

The principle of operation is that an alternating magnetic flux penetrates a closed circuit formed by liquid Chalk and excites a current in this circuit.

The liquid chalk circuit is surrounded by fireproof material, which is baked into a steel body. The space that is filled with liquid chalk has the shape of a curved channel. Working space The stove (bath) is connected to the channel with 2 holes, due to which a closed circuit is formed. During operation of the furnace, liquid Chalk moves in the channel and at the junction with the bath. The movement is caused by overheating of the Mel (in the channel it is 50-100 ºС higher than in the bath), as well as by the influence of the magnetic field.

When all the Chalk is drained from the furnace, the electrical circuit breaks, which is created by the liquid Chalk in the channel. Therefore, in channel furnaces produce partial drainage of liquid chalk. The mass of the “swamp” is determined based on the fact that the mass of the column of liquid Chalk above the channel exceeds the electrodynamic force pushing the Chalk out of the channel.

Channel furnaces are used as a mixer for holding and melting furnaces. The mixer is designed to accumulate a certain mass of Mel and hold Mel at a certain temperature. The mixer capacity is taken to be equal to at least twice the hourly productivity of the melting furnace. Holding ovens are used to pour liquid chalk directly into molds.

Compared with crucible furnaces channel ones have lower capital investments (50-70% of crucible), low specific consumption electricity (higher efficiency). Flaw: Lack of flexibility in regulating the chemical composition.

The main nodes include: Furnace frame; Lining; Inductor; Fur-zm tilt; Electrical equipment; Water cooling system.