Do-it-yourself furnace for melting metal at home. Do-it-yourself coal melting furnace

A domestic metal melting furnace can also be used to quickly heat up metal elements, for example, when they are tinned or shaped. The characteristics of the operation of the presented installations can be adjusted to a specific task by changing the parameters of the inductor and the output signal of the generator sets - this way you can achieve their maximum efficiency.

MELTING FURNACE is a foundry furnace with an inductor for melting metal. The advantage is that the melting mass is perfectly mixed to a homogeneous composition if an induction melting furnace is used. Induction technology speeds up the process of melting metal (melting time 45 minutes), such furnaces have good performance! ZAVODRR – melting furnaces for steel, aluminum, copper from professionals!

How are melting furnaces arranged?

Melting furnaces are a working chamber into which the feedstock (charge), materials and materials that intensify the formation of the melt are placed. The chamber is separated from the outer casing by means of a refractory lining, as well as a heat-insulating layer. Depending on the type of energy source used or the heating method (induction method, graphite electrodes, gas burners), the device of the chamber depends, as well as the time and quality of the output material. Let's look at the device of melting furnaces.

- AT arc melting furnaces a device for draining the melt and separating slag masses is located in the lower part of the furnace. Electrodes are placed on top of their number from 1 to 4 pieces. A transformer acts as a power source. The disadvantage of this method may be the sintering of the metal.

– induction melting furnace consists of an inductor, inside of which there is a crucible with a refractory lining. The equipment is equipped with charge loading mechanisms, systems that provide complete discharge of the finished melt, control and adjustment systems. In induction melting furnaces, the metal is poured from the top. Thyristor or transistor converters act as a power source. The quality of the remelted metal in this way is the best, because the induction method is a constant uniform mixing of the charge during melting; The device of melting furnaces depends on their type.

– Gas Melting Furnaces have the simplest and cheapest design. A gas burner is connected to the melting unit in the lower part, which runs on ordinary main gas (methane). Typically, these furnaces are used to remelt metals with a low specific calorific value, such as aluminum or copper.

Melting Furnaces - Benefits

When choosing a melting furnace, you need to know its disadvantages and advantages. The main advantage of gas melting furnaces is the minimum cost of melting metal, because gas is the cheapest energy carrier. Induction melting furnaces provide excellent melt quality at the outlet. Electric arc - to reach the maximum melting temperature, for refractory materials or alloys. All types of furnaces have good process automation and a small amount of harmful atmospheric emissions.

The advantages of using induction furnaces are obvious:

• production technology makes it possible to obtain high-quality melts with a uniform chemical composition,
• it is possible to introduce additional alloying elements,
• furnaces have a high efficiency of about 95%,
• comparatively small waste,
• production technology that is safe for the health of personnel,
• production efficiency achieved by generating a large amount of heat from the metal, which allows less power to be consumed.

The main characteristics of thermal installations are the capacity of the working chamber, which determines the productivity, the type of material for which it is intended to be smelted, and the rated power of the heating element, which sets the maximum operating temperature, as well as the energy intensity of the process.

Paying attention to the characteristics of the equipment when choosing induction furnaces, it is worth paying special attention to the quality of the crucible. On average, the crucible is designed for the number of heats from 20 to 60. The set of the induction furnace, in addition to the crucible, includes:

• frequency converter (transistor or thyristor),
• capacitor banks,
• melting knots,
• water cooled cables,
• cooling systems and control panels.

Management and control over the melting process must be carried out by specially trained personnel.

The heating element of such installations can operate both in industrial and medium frequencies. The advantages of this solution are complete control over oxidative processes, as well as complete draining of the melt. Both acidic and basic materials can be used as lining materials.

Melting furnaces for melting metal are the most demanded equipment for metallurgical enterprises. Induction melting furnaces make the melting process more economical and of higher quality. Depending on the type of metal and the volume of the charge, the process of melting metal in an induction furnace takes on average from 30 minutes to 1.5 hours. Induction furnaces allow for heat treatment of ferrous, non-ferrous and even precious metals.

Steel melting occurs at a temperature of 1500-1600 degrees Celsius. In the smelting process, it is necessary to reduce the content of substances that degrade the quality of steel, such as sulfur, phosphorus and oxygen. The choice of lining depends on the composition of the desired melt. Induction furnaces are ideal for the production of alloy steels. The melting time of steel takes on average about 1 hour.

These ovens operate mainly at industrial frequencies of 50 Hz and are equipped with high-precision automation that allows you to control both temperature and segregation intensity. The amount of waste in them barely reaches 2%, in addition, they are not demanding on the quality of preparation of charge materials.

The melting point of aluminum is 660 degrees Celsius, so it is important that the thyristor converter is not too powerful. An aluminum melting unit should not be used to melt other metals. The use of an induction furnace for melting aluminum and its alloys will make it possible to obtain a homogeneous melt of high quality.

A distinctive feature of such furnaces is the low heating temperature and. as a result, low power consumption. Graphite is common as the main material for the crucible, in addition, to intensify the process, a metal core can also be used, connected to the medium-frequency network through a step-down transformer. The maximum heating temperature, as a rule, does not exceed 750 ºС.

Melting furnaces for copper

Melting copper in an induction furnace takes no more than 40 minutes. The process of obtaining the melt occurs at a temperature of 1000-1300 degrees Celsius. Melting can be done in a vacuum, in a protective gas environment or in an open environment. Due to its high thermal and electrical conductivity and flexibility, copper is widely used in various industries.

In the production of copper melt, it is very important to ensure chemical purity, therefore, furnaces, in some cases, have a sealed working chamber, and induction heating is carried out in a soft mode. There are no significant structural differences from induction furnaces for non-ferrous metals, but the main requirement is the absence of a direct reaction between the crucible material and the melt.

Melting Furnaces - Transistor

Small foundries use transistorized furnaces to melt charge. These ovens use a medium frequency induction heater. Melting of metals is carried out in a graphite crucible. In transistorized furnaces, there is a dynamic circulation of the metal melt inside the crucible, due to which the temperature is equalized throughout the volume of the crucible, which contributes to obtaining a homogeneous chemical composition of the multicomponent alloy. In such furnaces, a quick transition from an alloy of one grade to another is possible.

Transistor induction furnaces are distinguished by versatility and extremely high efficiency, which can reach 99%, instead of the usual copper winding, they use an induction-type heater assembled on a system of interconnected transistors. An advantage is the electrodynamic circulation, which ensures uniform mixing of the melt.

Another type of induction furnaces are installations. In which, to stabilize the heating process and ensure the possibility of its regulation, thyristor frequency converters of current are used, which ensure the formation of an electromagnetic field.

An induction furnace is often used in the field of metallurgy, so this concept is well known to people who are more or less connected with the process of smelting various metals. The device allows you to convert electricity generated by a magnetic field into heat.

Such devices are sold in stores at a fairly high price, but if you have minimal skills in using a soldering iron and can read electronic circuits, then you can try to make an induction furnace with your own hands.

A homemade device is unlikely to be suitable for complex tasks, but it will cope with basic functions. You can assemble the device on the basis of a working welding inverter from transistors, or on lamps. The most productive in this case is the device on the lamps due to the high efficiency.

The principle of operation of the induction furnace

The heating of the metal placed inside the device occurs by the transition of electromagnetic pulses into heat energy. Electromagnetic impulses are produced by a coil with turns of copper wire or pipe.

Scheme of the induction furnace and heating schemes

When the device is connected, an electric current begins to pass through the coil, and an electric field appears around it, changing its direction over time. For the first time, the performance of such an installation was described by James Maxwell.

The object to be heated must be placed inside the coil or close to it. The target object will be pierced by a flux of magnetic induction, and a vortex-type magnetic field will appear inside. Thus, inductive energy will turn into heat.

Varieties

Furnaces on an induction coil are usually divided into two types depending on the type of construction:

• Channel;
• Crucible.

In the first devices, the metal for melting is located in front of the induction coil, and in the furnaces of the second type it is placed inside it.

You can assemble the oven by following the steps below:

1. We bend the copper pipe in the form of a spiral. In total, it is necessary to make about 15 turns, the distance between which should be at least 5 mm. Inside the spiral, a crucible should be freely located, where the smelting process will take place;
2. We make a reliable case for the device, which should not conduct electric current, and must withstand high air temperatures;
3. Chokes and capacitors are assembled according to the scheme indicated above;
4. A neon lamp is connected to the circuit, which will signal that the device is ready for operation;
5. A capacitor is also soldered to adjust the capacitance.

Heating use

Induction furnaces of this type can also be used for space heating. Most often they are used together with a boiler, which additionally produces cold water heating. In fact, designs are used extremely rarely due to the fact that, as a result of electromagnetic energy losses, the efficiency of the device is minimal.

Another drawback is based on the consumption of large amounts of electricity by the device during operation, because the device is classified as economically unprofitable.

System cooling

A self-assembled device must be equipped with a cooling system, since during operation all components will be exposed to high temperatures, the structure may overheat and break. Store-bought ovens are cooled with water or antifreeze.

When choosing a cooler for the home, preference is given to options that are most beneficial for implementation from an economic point of view.

For home ovens, you can try using a conventional blade fan. Pay attention to the fact that the device should not be too close to the oven, as the metal parts of the fan negatively affect the performance of the device, and can also open the vortex flows and reduce the performance of the entire system.

Precautions for using the device

When working with the device, you must adhere to the following rules:

• Some elements of the installation, as well as the metal that melts, are exposed to strong heat, as a result of which there is a risk of getting burned;
• When using a lamp oven, be sure to place it in a closed case, otherwise there is a high probability of electric shock;
• Before working with the device, remove all metal elements and complex electronic devices from the working area of ​​the device. The device should not be used by people who have a pacemaker installed.

The induction type metal melting furnace can be used in tinning and forming metal parts.

A home-made installation is easy to adjust to work in specific conditions by changing some settings. If you follow the indicated schemes when assembling the structure, as well as follow the elementary safety rules, a home-made device will practically not be inferior to store household appliances.

Ancient potters who fired pottery in kilns sometimes found shiny hard pieces with unusual properties at the bottom of the kilns. From the very moment when they began to think about what these wonderful substances were, how they appeared there, and also where they can be used with benefit, metallurgy was born - the craft and art of metal processing.

And the main tool for extracting new extremely useful materials from ore was thermosmelting forges. Their designs have come a long way of development: from primitive disposable clay domes heated by firewood to modern electric furnaces with automatic control of the melting process.

Metal-smelting units are needed not only by the giants of ferrous metallurgy, which use cupolas, blast furnaces, open-hearth furnaces and regenerator converters with a production of several hundred tons per cycle.
Such values ​​are typical for the smelting of iron and steel, which account for up to 90% of the industrial production of all metals.
In non-ferrous metallurgy and secondary processing, the volumes are much smaller. And the world turnover of production of rare earth metals is generally estimated at several kilograms per year.

But the need for smelting of metal products arises not only in its mass production. A significant sector of the metalworking market is occupied by foundry production, where metal-smelting units of relatively small output are required - from several tons to tens of kilograms. And for piece handicraft and arts and crafts production and jewelry, melting machines with a yield of several kilograms are used.

All types of metal-smelting devices can be divided according to the type of energy source for them:

1. Thermal. The heat carrier is flue gas or strongly heated air.
2. Electrical. Various thermal effects of electric current are used:
   • Muffle. Heating of materials placed in a heat-insulated housing with a spiral heating element.
   • resistance. Heating a sample by passing a large current through it.
   • Arc. The high temperature of the electric arc is used.
   • Induction. Melting of metal raw materials by internal heat from the action of eddy currents.
3. Streaming. Exotic plasma and cathode-ray devices.

In-Line Electron Beam Melting Furnace Thermal Open Hearth Furnace Electric Arc Furnace

With small volumes of generation, the most appropriate and economical is the use of electric, in particular, induction melting furnaces(IPP).

The device of induction electric furnaces

In short, their action is based on the phenomenon of Foucault currents - eddy induced currents in a conductor. In most cases, electrical engineers deal with them as a harmful phenomenon.
For example, it is precisely because of them that the cores of transformers are made of steel plates or tape: in a solid piece of metal, these currents can reach significant values, leading to useless energy losses for heating it.

In the induction melting furnace, this phenomenon is put to good use. In fact, it is a kind of transformer, in which the role of a short-circuited secondary winding, and in some cases the core, is played by a melted metal sample. It is metallic - only materials that conduct electricity can be heated in it, while dielectrics will remain cold. The role of the inductor - the primary winding of the transformer is performed by several turns of a thick copper tube rolled into a coil, through which the coolant circulates.

By the way, the extremely popular kitchen hobs with high-frequency induction heating operate on the same principle. A piece of ice placed on them will not even melt, and the set metal utensils will heat up almost instantly.

Design features of induction thermal furnaces

There are two main types of PPIs:

For both types of metal-smelting units, there are no fundamental differences in the type of working raw materials: they successfully melt both ferrous and non-ferrous metals. It is only necessary to select the appropriate operating mode and type of crucible.

Selection Options

Thus, the main criteria for choosing one or another type of thermal furnace are the volume and continuity of production. For a small foundry, for example, in most cases, a crucible electric furnace is suitable, and a channel furnace is suitable for a recycling company.

In addition, among the main parameters of a crucible thermal furnace is the volume of one heat, on the basis of which a specific model should be chosen. Important characteristics are also the maximum operating power and the type of current: single-phase or three-phase.

Choice of mounting location

The placement of the induction furnace in a workshop or workshop should provide a free approach to it for the safe performance of all technological operations in the melting process:

• loading of raw materials;
• manipulations during the working cycle;
• unloading of the finished melt.

The installation site must be provided with the necessary electrical networks with the required operating voltage and number of phases, protective earthing with the possibility of a quick emergency shutdown of the unit. Also, the installation must be provided with a supply of water for cooling.

Desktop structures of small dimensions must nevertheless be installed on strong and reliable individual bases not intended for other operations. Floor units also need to provide a solid reinforced foundation.

It is forbidden to place flammable and explosive materials in the melt discharge area. A fire shield with extinguishing agents must be hung near the location of the stove.

Installation instructions

Industrial thermomelting units are devices with high power consumption. Their installation and wiring must be carried out by qualified specialists. The connection of small units with a load of up to 150 kg can be carried out by a qualified electrician, following the usual rules for electrical installations.

For example, an IPP-35 furnace with a power of 35 kW with a production volume of ferrous metals of 12 kg, and non-ferrous metals - up to 40 has a mass of 140 kg. Accordingly, its installation will consist of the following steps:

1. Selection of a suitable location with a solid base for the hot melt unit and the water-cooled high voltage induction unit with capacitor bank. The location of the unit must comply with all operational requirements and regulations for electrical and fire safety.
2. Providing installation with a water cooling line. The described electric melting furnace does not come with cooling equipment, which must be purchased separately. The best solution for this would be a double circuit closed circuit cooling tower.
3. Protective earth connection.
   

   The operation of any electric melting furnace without grounding is strictly prohibited.

4. Connecting a separate electrical line with a cable, the cross section of which provides the appropriate load. The power shield must also provide the required load with a power margin

For small workshops and home use, mini-furnaces are produced, for example, UPI-60-2, with a power of 2 kW with a crucible volume of 60 cm³ for melting non-ferrous metals: copper, brass, bronze ~ 0.6 kg, silver ~ 0.9 kg, gold ~ 1.2 kg. The weight of the installation itself is 11 kg, dimensions - 40x25x25 cm. Its installation consists in placing it on a metal workbench, connecting flowing water cooling and plugging it into a power outlet.

Technology of use

Before starting work with a crucible electric furnace, it is imperative to check the condition of the crucibles and lining - internal protective thermal insulation. If it is designed for the use of two types of crucibles: ceramic and graphite, it is necessary to choose the appropriate loaded material according to the instructions.

Usually ceramic crucibles are used for ferrous metals, graphite - for non-ferrous.

Operating procedure:

• Insert the crucible inside the inductor and, having loaded the working material, cover it with a heat-insulating cover.
• Turn on water cooling. Many models of electric melting units will not start if there is not the necessary water pressure.

• The melting process in the crucible IPP begins with its inclusion and access to the operating mode. If there is a power regulator, set it to the minimum position before turning it on.
• Slowly raise the power to the working power corresponding to the loaded material.
• After melting the metal, reduce the power to a quarter of the working one to maintain the material in a molten state.
• Before pouring, turn the regulator to a minimum.
• At the end of melting - de-energize the installation. Turn off water cooling after it cools down.

All the time of melting the unit must be under supervision. Any manipulations with the crucibles should be done with tongs and in protective gloves. In the event of a fire, the installation should be immediately de-energized and the flames should be extinguished with a tarpaulin or extinguished with any fire extinguisher other than acid. Filling with water is strictly prohibited.

Advantages of induction furnaces

• High purity of the resulting melt. In other types of metal-melting thermal furnaces, there is usually direct contact of the heat carrier with the material, and, as a result, contamination of the latter. In IPP, heating is produced by absorption of the electromagnetic field of the inductor by the internal structure of the conductive materials. Therefore, such furnaces are ideal for jewelry production.
  

  For thermal furnaces, the main problem is to reduce the content of phosphorus and sulfur in the melts of ferrous metals, which worsen their quality.

• High efficiency of induction-melting devices, reaching up to 98%.
• High melting speed due to the heating of the sample from the inside and, as a result, high productivity of the IPP, especially for small working volumes up to 200 kg.
  

  Heating muffle electric furnace with a load of 5 kg occurs within a few hours, IPP - no more than an hour.

• Devices with a load of up to 200 kg are easy to place, install and operate.

The main disadvantage of electric melting devices, and induction devices are no exception, is the relative high cost of electricity as a coolant. But despite this, the high efficiency and good performance of the IPP largely pay for them during operation.

The video shows an induction furnace during operation.

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

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Device and circuit

The device of a muffle furnace for melting metal consists of:

• in most cases steel case. 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 insulation. For home stoves, fireclay bricks or other heat-insulating material is used that can withstand heating temperatures up to 1000 0 - 1200 0;
• the steel body can be overlaid with an outer layer of ceramic tiles or refractory bricks;
• electric or gas heating elements. Gas burners are best purchased in specialized stores. An electric oven can be equipped with homemade nichrome or fechral spirals. 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 the operation of equipment. By installing thermal sensors, you can easily control the temperature regime and the time to maintain the set temperature.

Conclusion

Home-made or industrial furnaces for hardening metal or melting it - all these designs should ensure safety and comfort in working with heating devices. It is not difficult to make a design on your own, even a beginner can handle it. The main thing is to carefully and responsibly follow all the recommendations and rules for performing work.