Cast Iron Guide: Care and Cooking Tips

Cast iron at home

I read the forum - I still can’t figure out whether anyone has managed to cast cast iron with satisfactory quality, or at least make a part out of it, and not just melt it.
As I understand it, a jew's harp cannot be small (in sizes no more than 50 liters of a propane cylinder), and it does not produce an acceptable quality of metal (suitable for the manufacture of machine tool parts). (I know about further aging). To improve it, an accumulation furnace is used, where liquid metal accumulates, disassembled, and alloys are introduced. Cutting it down doesn't really work. With this type, the option with a harp is no longer necessary? Is it possible to melt cast iron (up to 5 - 10 kg) in a steel crucible from a scrap cylinder, for example on gas burners or coal? If high-quality cast iron scrap is used (for example, pieces of a broken frame from a Soviet machine tool) and melting takes place in a crucible, does this ensure the quality of the extracted product at the output (the mode of heat treatment, casting, cooling and aging is special), at least in a chemical sense - does it burn out? and carbon and alloys? It’s absolutely possible to melt cast iron at home, it’s just that no one needs it separately yet. A cupola furnace cannot be small, it’s true, the network will not support an electric furnace; all that remains is a fiery furnace and melting either in a crucible or on a hearth. In a crucible, the change in cast iron composition will be smaller. You can sculpt crucibles yourself from graphite and fireclay chips, although they are short-lived but cheaper. Read ancient books on smelting, then everything is clearly described, including images of furnaces and smelting modes. Now I’m also curious about this process, I’m starting to gradually go through it.

The correct coating has the appearance of varnish, is hard and does not get wet in water. My experimental frying pan has been in use for six months now, but I deliberately wash it with weak soap and do not lubricate it with oil. I just wipe it and heat it on the burner (the last procedure also allows you to get rid of the smells of the last dish). During this time, the coating on the bottom has been scratched, so in the very near future I will fly it from below, and for now I will use the top as before.

And also, before welding the part, you need to determine the grade of cast iron, at least approximately, in order to more accurately determine the welding method. There are varieties. Cast iron is marked as L1 L2 and so on up to L6, but there are other markings. Here are all the markings I'm familiar with. L1 L2 L3 L4 L5 L6 LR1 LR2 LR3 LR4 LR5 LR6 LR7. LR means cast iron refined with magnesium.

Have a nice day, forum members. I read here about melting cast iron and casting it into blanks or ingots. What about the real details? Please do not send to YouTube. I then noticed a video about “lost wax casting”, but then the factory. , but I’m interested in it being free and angry. I pour colored metal into plaster with sand. But I think at such a high temperature the plaster seems to be destroyed. what to replace it with?

Cast iron is made from an alloy of iron, carbon, silicon and phosphorus. At a temperature of 1400 degrees, the cast iron product is cast using seamless technology in a whole earthen figure, which splits after casting the product. At the end of production, the product is cleaned, minor imperfections that occur during the casting of a cast iron figure are removed to obtain a perfectly clean, rough surface. Several layers of enamel are applied to the outer and inner side of the product, after which the cast iron product is fired at a temperature of 800 degrees for half an hour. Sharp porous enamel allows drops of fat to easily penetrate the small pores of cast iron and create a non-stick coating. This enamel provides the most global heat distribution and uniform cooking of food. The last stage of the industrial cycle is the installation of accessories.

Unambiguously! For multi-storey buildings with central heating, it is recommended to install cast iron radiators. They are not subject to corrosion and retain heat well. Their primary advantage over other radiators is that they do not react to the quality of the coolant. Heating water undergoes water treatment and various reagents are added significantly. Starting from salt and soda, and various additives to soften water. All current radiators react strongly to the lack of water in the system. According to the instructions, it is not recommended to drain water from the system for more than 15 days. And here we drain it for the whole summer season. So there you go! In aluminum, bimetallic and metal radiators, the process of decomposition of the remaining water occurs. This causes wear and tear on the radiators. Cast iron radiators solve all this. They don't react with anything. Therefore, their durability is 50 years or more. Cast iron radiators are immediately available in the current design. Radiators are supplied coated with baked epoxy polyester enamel. They don't feel the need to paint. For example, radiators from KONNER: MODERN, HIT, Retro, etc. The photo shows a MODERN radiator.

Before the main use of cast iron cookware, it is recommended to wash it with hot water and soap, then wipe it dry, and then lubricate the entire surface of the cookware with fat or vegetable oil. After this, bake in the oven for one hour. Current professional cast iron cookware does not require old-fashioned processing; it is already completely ready for use, since it has an internal enamel coating.

Use of material in construction

This section will discuss the classification, marking (grades) and application of cast irons and their alloys.

Features of application

Gray cast iron is used in construction. White is too hard and brittle. It is smelted into malleable iron or steel.

Cast iron has been used in construction since ancient times. Products made from it were of excellent quality if the production technology was strictly followed. Cast iron has always been produced by casting. The manufactured material should not have air pockets, molding lines or cracks.

• In ancient times, supporting structures were made from cast iron, which were assembled piece by piece. First, the structural cast iron elements were cast, and then the bases were connected with fasteners. This method was especially often used in arched structures.
• Cast iron has always been used to make sewer pipes, racks and post bases. Various designer items were made from it for homes.
• Pipes in our houses, heating radiators, taps, water supply valves, fittings - all this is made using cast iron.
• Plumbing products can be partially or completely made from the described material.
• I would especially like to mention cast iron heating radiators. These devices are in high demand. Such heating radiators are durable, have high heat transfer and excellent heat-storing properties. They remain warm and give off heat to the room even an hour after being turned off. Compared to steel radiators, they lose heat twice as fast.
• Today and in the past, grates were made from cast iron. With this strong material it was possible to create various shapes and designs. Interesting patterns and lines made cast iron products truly skillful. Some embankment decorations and palace fences have survived to this day. These works of art were made according to the ideas of famous masters. And cast iron made it possible to bring these ideas to life and preserve them to this day.

There is one caveat. Modern building materials have replaced cast iron. In some products, cast iron has been replaced with plastic. Today, practically no water fittings, sewer pipes, or plumbing fittings are manufactured. However, lids, fences and large sewer pipes are still made from cast iron.

Cast iron fittings

Cast iron

This type of cast iron has become popular due to its low fusibility. It melts even at low melting temperatures and easily fills the mold. Cast iron castings are quite durable and free of bubbles.

If we are talking about high-quality cast iron, then when it changes its state (from liquid to solid) it does not change its volume. This effect is achieved by adding special impurities to cast iron in the form of phosphorus, sulfur, manganese and silicon.

• Due to its low fusibility, cast iron is used to make beautiful building parts in the form of various shapes. Subsequently, these parts are securely fastened with bolted connections.
• In architecture there is no place without cast iron. Decorative cast iron elements can decorate any building and architectural monument.

Forged products

Cast iron is highly valued by blacksmiths. This material lends itself well to forging. This is all connected with the atomic lattice of the material, which has gaps. Making any products from it is as easy as shelling pears for a blacksmith. The following forged products have become a part of our lives:

• Lanterns;
• Stairs;
• Decorative elements;
• Gates;
• Window grilles;
• Front gardens;
• Lantern poles.

Today, parks, offices and urban architecture are decorated with forged lattices, patterns, and applications.

Cast iron is resistant to corrosion. It is durable. And therefore, some cast iron elements have not lost their appearance to this day. It was noted that forged cast-iron stairs (both outside the house and inside), openwork drawings, sculptures, window grilles, gates and street lights look very impressive.

Cast iron staircase

Benefits of use

In construction, cast iron has proven itself due to the following positive aspects:

• Cast iron decorative elements produce a good visual effect.
• Cast iron objects are not subject to corrosion processes.
• Complex cast iron shapes can be produced very quickly.
• Cast iron products have high strength.
• Simple production process.
• Making cast iron products is inexpensive.
• Long service period.

The price of forged products depends on the amount of material used, the complexity of production, speed of execution, and company prices. The price is available to everyone. Everyone can decorate their homes with fashionable elements and grilles.

This video will tell you how cast iron and steel can be used:

DIY coal smelting furnace

The weekend was quite fruitful. I managed to build a smelting furnace with my own hands. It runs on solid fuel (coal, coke) and is capable of melting more than 5 kg of aluminum at a time! Regular readers of my tech blog Dimanjy may notice that I have already made a muffle furnace with my own hands. But it runs on electricity and is designed for melting small volumes of aluminum.

Thanks to the use of solid fuel (coal), I was able to smelt aluminum in my new smelter like a grown-up. Burning coke produces more heat than could be squeezed out of an electric muffle furnace. Not a single home wiring (even in a private house) will allow you to receive so much thermal energy! Undoubtedly, a coal-fired melting furnace is the only option for melting large volumes of aluminum, although for small castings it is more profitable to use an electric muffle furnace. Next, I’ll tell you a little about the process of assembling a melting furnace with your own hands.

Like my first muffle kiln, the new coal kiln is made of fire bricks that are bonded together with fireclay clay. The peculiarity of a coal (or coke) smelting furnace is the need for forced pressurization. For this purpose, I provided a special air channel in the lower part of the oven.

Inside the furnace, above the air channel, there is a so-called grate. This is a special grate, usually made of cast iron, on which fuel is laid out. You can find one at a home stove and fireplace store. In fact, I took it out of the idle home stove.

To improve the structural strength, I lightly scalded my melting furnace with a metal band and secured it through the reinforcement to the outside wall of the garage. Extra strength never hurts, I’m not going to melt sausages in it! In addition, I laid it out with refractory bricks placed on edge - I decided to save bricks and work space. It turns out that the stove is built not even half a brick, but a quarter of a brick.

I coated the outer wall of the smelting furnace with the remains of the fireclay clay. It might affect the strength somehow. Although all this coating subsequently cracked from heating.

In order to reduce the amount of heat loss, and simply not get burned on the melting furnace during its operation, I decided to insulate the furnace. For this I used mineral wool. It doesn't burn. Only her hands still itch! If you use one, you need to wear rubber gloves, safety glasses and a respirator!

Of course, mineral wool cannot simply be left sticking out. In a good way, it needs to be isolated from moisture. Usually, a protective film is also purchased along with such cotton wool. For some reason I completely forgot to take it with me from the garage, so I just built a casing for my melting furnace from galvanized sheet. It is very easy to bend a galvanized sheet if you hit the bend well with the pointed side of a hammer

Aluminum smelting

Making a furnace for melting aluminum with your own hands is a real thing. In industrial production, units with the name - rotary-type ovens - are very expensive.

To understand how to make a furnace for melting aluminum, you need to understand their operating principle. There are several types where non-ferrous metal is melted.

Mini oven

Take a car wheel and bury it in the ground so that the top cut does not protrude outward. A hole is made in the middle for the pipe. One end is passed into the hole, and the other is brought out. A cooler is placed on it to pump air. The smelter is filled with coals and aluminum scrap. Air is supplied and the temperature rises.

Metal tank

You can make a furnace for aluminum from a metal tank. For example, the body of a top-loading washing machine. The interior of the structure is lined with refractory bricks. A pipe for air supply is mounted below. Thus, portable equipment is obtained.

From the bottle

One of the unusual ways in which aluminum is melted. Nichrome wire is wound around the bottle. The surface of the bottle is first lubricated with oil. A mixture of liquid glass and clay is applied on top. Drying is carried out for a week. Then another layer of wire is wound and clay is applied. After 7 days, the bottle is removed and only the heat-resistant shell remains. Voltage is connected to the ends of the wire to glow the nichrome, and raw materials are loaded into the hearth.

Iron casting technology

The technology of cast iron casting was first mastered in China around the 10th century AD; in Europe it was first mentioned in the 14th century as a material for the production of cannons. In Russia, the first “iron casting suitable for making cannons” dates back to the era of Ivan IV Rurikovich. The heyday of the cast iron era came in the 19th and 20th centuries. At this time, bridges and pipelines, lanterns and fences, elements of architectural decor and load-bearing structures of buildings were made from it. In addition, rails, parts of machine tools, and engines were cast from the same material. Separately, it is worth mentioning cast iron cookware, irons and heating appliances.

Cast iron was also the starting component for the production of steel using the open-hearth method. The volume of its production was the most important indicator of the country's economic power and its military potential. With the invention of inexpensive technologies for the production and processing of aluminum and steel alloys, the importance of cast iron as a structural material has noticeably decreased. The widespread development of the production of high-strength plastics and composite materials has finally pushed cast iron from the forefront.

Iron casting process

Cast iron is produced in blast furnaces - huge structures as high as a ten-story building. After the ore is melted and impurities are removed, the cast iron is cast into steel molds - molds. The resulting ingots (pigs) contain cast iron of a certain grade and are ready for further processing. At foundries, various finished products are cast from them.

Iron casting process

The main stages of the iron casting process:

1. Preparing a finished product model
2. Making a mold for casting
3. Melting cast iron pigs
4. Melt casting into molds
5. Removing castings and finishing them

There are several methods for making models and preparing molds

Basic methods of iron casting

Modern industry uses many different methods to produce iron castings. They come down to several basic casting methods:

• into molds made from a clay-sand mixture (the so-called “in-ground” casting)

A model of the finished product is placed inside the mold, completely repeating its shape, but exceeding it in size by the amount of casting shrinkage. The clay-sand mixture is compacted and compacted, ensuring complete adherence to the model. Casting of cast iron into a mold is carried out through specially provided holes - sprues.

• into plaster molds (and from other hardening solutions);
• into shell forms;
• in chill molds (metal protected forms);
• by lost wax models;
• under pressure.
• In a gasified model

Experts distinguish several types of cast iron, depending on the content of certain impurities.

Gray cast iron contains from 2.9% to 3.7% graphite and silicon, has excellent casting properties:

• low melting point
• high melt fluidity
• small shrinkage.

It is a suitable material for machine bodies and mechanisms, pistons and engine cylinder blocks. High fragility precludes the use of the material in parts subject to bending and tension. Casting of gray cast iron is mainly carried out in sand molds and in chill molds.

High-strength cast iron, ductile iron, contains graphite in spherical form. This type of graphite is characterized by high viscosity and malleability, suitable for forging. Pipes, pipeline fittings, critical and highly loaded mechanical parts are cast from it.

Products made from high-strength cast iron are also produced by casting into a gasified model. Cast iron is cast into a mold made from a sand mixture compacted around polystyrene model blocks.

To improve the mechanical properties, high-strength cast iron castings are subjected to heat treatment. Its main stages:

• heating up to 850 °C;
• exposure in a heated state for several hours;
• slow cooling in mineral oil at 350 °C.

Heat treatment increases the homogeneity of the material and relieves internal stresses in the casting, reducing the likelihood of cracks during operation

1.Sand casting

The accuracy of geometric dimensions and surface roughness of castings obtained in sand molds in many cases do not meet the requirements of modern technology.
Sand casting provides low surface quality (below Rz = 320 microns), low accuracy (below 16th grade), is difficult to automate and does not provide satisfactory working conditions. Therefore, special casting methods are developing at a rapid pace: in shell molds, investment casting, chill molding, under pressure, centrifugal and others, which make it possible to obtain castings of increased accuracy, with low surface roughness, minimal allowances for machining, and sometimes completely eliminating it, ensuring high labor productivity, etc.

Iron production

From a number of the main indicators of the country's economic power, the production of cast iron was relegated to a number of secondary ones, but did not lose its importance for the economy.

The leader in pig iron production with an almost tenfold lead is China - 543.748 million tons per year, followed by Japan - 66.943 million tons, Russia - 43.945 million tons and India - 29.646 million tons. China produces more than 50% of the world's pig iron.

Cast iron is produced in blast furnaces, the prepared iron ore is smelted along with additives, and coking coal or natural gas is used as fuel.

The main consumption of pig iron today is as a component for steel smelting. The development of cast iron production is mainly in the direction of increasing its energy efficiency, environmental friendliness and cost reduction.

The unique properties of cast iron - low cost, strength and corrosion resistance - allow the ferrous metal to look confidently into the future.

Slag formation

Thus, we have found out how cast iron is produced. However, when this material is smelted, another product is obtained that is widely used in the national economy. When melting 1 ton of cast iron, 0.6 tons of slag comes out. The fact is that even refined iron ore contains a fairly large amount of clay. Coke also contains ash. To remove these unnecessary elements, among other things, fluxes (calcium and magnesium carbonates) are added to the charge. During the smelting process, they enter into a chemical reaction with various types of impurities, resulting in the formation of slag. It is an aluminosilicate or silicate melt.

The density of slag is less than that of liquid cast iron. Therefore, during the melting process it is located underneath. It is removed periodically through a separate taphole, called a slag taphole. This by-product of iron foundries is used mainly for the production of cement and building blocks as a filler.

Cast iron castings

Cast iron castings come in different sizes - from small parts to multi-meter beds of large machine tools. Their configuration can also be very diverse - from simple bushings to sophisticated cast grilles and gates.

Iron castings are also divided into:

1. by purpose - general and special, such as anti-friction, heat-resistant, etc.
2. according to the structure of the material - ferritic, perritic and mixed
3. According to the type of graphite contained - into spherical, lamellar, flake and vermicular
4. According to carbon content - white, gray and bleached

In metallurgical science, there are other classifications of cast iron castings.

Casting methods

The most modern method is casting using gasified models. This method allows not only casting iron, but also producing steel castings. The method is economical, environmentally friendly and allows for the reuse of mold material.

The method consists of the following steps.

Model preparation

The models are made from pre-foamed and dried polystyrene with a grain size of 0.3-0.9 mm. (depending on the dimensions of the part). The material is blown into molds, baked and cooled.

Casting using gasified models

Lead smelting

An electric furnace for melting lead consists of the following elements:

• A round casing made of stainless steel, inside of which there is insulation. It is attached with brackets to the wall.
• An industrial heating element is supplied from below.
• There is a rotary type valve on top.
• A sensor that is located 3 cm from the bottom.
• There is a temperature regulator on the side.

By setting the regulator to a certain temperature, we warm up the device. The lead inside melts. At the end of the melt, a mold is placed underneath and the valve opens. Molten lead fills the interior of the mold.

Advantages of cast iron

Iron casting differs from castings from other materials in a number of advantages, such as:

• cheapness
• high strength and wear resistance
• high surface quality, minimizing subsequent machining

Characteristics and application of cast iron

It is important to note that when using modern casting methods, not only the casting itself is cheaper, but also the final product. Many industries, which at the end of the 20th century replaced the cast iron parts of their products with steel ones, have returned or are planning to return to the time-tested material at a new stage of its development.

Care

The quality of the final workpiece is affected not only by the alloy and temperature conditions, but also by the shape itself. In the case where the die is in slag or in cracks, this will significantly reduce the quality of the blank. Therefore, before filling the mold, it is necessary to carefully examine it to see if there are any cracks and whether there are foreign objects or impurities. Next, you need to remove old paint, grease, slag, scale, and any dirt that may get into the liquid metal.

After you clean the mold, you need to assemble it, then install the rod and begin the pouring process using a special hole. As a rule, at the factory, chill molds are installed on a conveyor, and they move past a ladle with molten pig iron. Sometimes the molds may be stationary and a bucket will move instead of a conveyor.

Thus, the modern technology of cast iron for the manufacture of various parts has practically remained the same, but it is still in demand and relevant as before. Cast iron retains its position, and the fact that new materials and technologies have appeared has not changed this situation. Demand for it remains stable in many countries.

Iron smelting

The method of obtaining iron from ores is in principle very simple and is based on the reduction of iron oxides with coal. But since molten iron has the ability to dissolve coal, when smelted, the result is not pure iron, but an alloy containing up to 5% carbon and some other impurities, called cast iron.

Iron smelting is carried out in huge blast furnaces, or blast furnaces, lined with refractory bricks and reaching 25 m

height with an internal diameter of about 6
m.
A section of a blast furnace is shown schematically in Fig. 152. Its upper half is called the shaft and ends at the top with a hole - the top, which is closed by a movable funnel - the top gate. The widest part of the blast furnace is called the steam chamber, and the lower part is the forge. Hot air is blown into the furnace through special holes in the forge (tuyere).

The blast furnace is loaded first with coke, and then layer by layer with a mixture of ore with coke and fluxes and coke alone. Combustion and the temperature necessary for smelting cast iron are maintained by blowing heated air into the forge. The latter enters a ring pipe located around the bottom of the furnace, and from it through curved tubes through tuyeres into the hearth. In the forge, coal burns into carbon dioxide, which, rising to the top and passing through a layer of heated coke, turns into carbon monoxide. This carbon monoxide reduces most of the ore, turning back into carbon dioxide.

The process of ore recovery occurs mainly in the upper part of the mine and can be summarized by the following equation:

The individual stages of this process are shown in the form of equations in Fig. 153.

The waste rock contained in the ore interacts with the added fluxes, forming slag.

The released iron is lowered, still in solid form, into the hotter part of the furnace - steam, and here at a temperature of 1200° it melts in contact with coal, partially dissolving it and turning into cast iron. Molten cast iron flows into the lower part of the hearth, and liquid slag collects on the surface of the cast iron, protecting it from oxidation. Cast iron and slag are released as they accumulate through special holes, which are clogged the rest of the time with clay.

The carbon dioxide formed during the reduction of ore, rising to the upper part of the mine, is partially converted back into carbon monoxide. Therefore, blast furnace gases escaping from the hole contain up to 25% carbon monoxide. They are burned in special devices - cowpers, designed to preheat the air blown into the furnace.

Cowpers are tall cylindrical towers made of bricks and having vertical channels inside (Fig. 154). The blast furnace gases entering the cowper, burning in it, heat up the walls of the channels. At the same time, air blown into the blast furnace passes through another cowper, pre-heated in the same way. After some time, air is directed into the first cowper, and the second cowper is heated with blast furnace gases, etc.

The blast furnace operates continuously. As the top layers of ore and coke sink, new portions of the mixture of ore with fluxes and coke are added to the furnace. This mixture, called the charge, is delivered by elevators to the upper platform of the furnace and dumped into a cast-iron funnel, closed at the bottom with a flue gate. When the shutter is lowered, the mixture enters the oven. The operation of the furnace continues day and night for several years until the furnace requires major repairs.

Rice. 153. Progress of the blast furnace process

To evaluate the operation of blast furnaces, the so-called “use factor of the useful volume of the furnace” is used, which is obtained by dividing the volume of the furnace in cubic meters by the daily smelting of the furnace in tons. For example, if the furnace volume is 900 m 3 and the daily smelting is 500 tons,

then the utilization rate of the useful volume is 900/500 = 1.8. Thus, the lower the utilization rate of the useful volume, the greater the productivity of the furnace.

Before the revolution, at Russian factories the utilization rate of the useful volume of blast furnaces was 2.30. Soviet metallurgy, based on the widespread development of advanced working methods, sharply increased the productivity of the blast furnace process, reducing the utilization rate by approximately 3 times.

The use of oxygen to accelerate the process of smelting cast iron in blast furnaces opens up great prospects. When oxygen-enriched air is blown into the blast furnace, preheating it becomes unnecessary, which eliminates the need for complex and bulky cowpers and greatly simplifies the entire metallurgical process. At the same time, blast furnace productivity increases sharply and fuel consumption decreases. A blast furnace operating on oxygen blast produces one and a half times more metal, and requires one-quarter less coke than with ordinary air blast.

Rice. 154. Joint work of the blast furnace and cowpers

Cast iron obtained from blast furnaces contains on average about 93% iron, up to 5% carbon and small amounts of silicon, manganese, phosphorus and sulfur.

1 - blast furnace; 2 - cowper heated by flame; 3 - cowper, heating the air; 4 - blower; 5 - chimney; 6 - gas channel; 7 - smoke channel; 8 - air pipe.

The carbon contained in cast iron can be released from it when solidifying in a free state in the form of graphite or combine with iron to form iron carbide Fe3C, called cementite. Unlike graphite, the softest constituent of cast iron, cementite is the hardest constituent of this alloy. With prolonged heating, to 900° or higher, cementite decomposes into iron and graphite, which occurs especially easily in the presence of silicon. Therefore, cast iron containing a significant amount of silicon (from 2 to 3.5%) has a gray color due to the released graphite. Such cast iron is called gray cast iron; it is not very hard, it molds well, but it is fragile and easily breaks when hit. Gray cast iron is used for casting machine frames, flywheels, sewer pipes, plates, etc.

Cast iron, in which almost all the carbon is contained in the form of cementite, is harder and whiter than gray cast iron, which is why it is called white cast iron; it is characterized by a low silicon content (less than 1%) and a high manganese content (1-1.5%). White cast iron has no direct use and is processed into steel and iron, which differ from cast iron in having lower carbon content and the absence of other impurities (silicon, phosphorus, manganese). A product containing from 0>3 to 2% carbon is called hard steel, and a product containing less than 0.3% carbon is called mild steel or iron.

You are reading an article on the topic Iron smelting

Agglomeration process

In fact, we’ll look at how cast iron is produced below. Now let's talk about how ore is prepared for smelting directly at metallurgical plants.

If ordinary crushed material is used for smelting, the productivity of the blast furnace will drop sharply. The fact is that such a charge has a low degree of gas permeability. Therefore, before loading into the blast furnace, ore must undergo an agglomeration process.

This procedure is carried out in specialized workshops of metallurgical plants and is a process of sintering rock into pieces of a certain size most suitable for smelting cast iron. Adhesion occurs at a high temperature sufficient to easily melt the surface of the charge particles. As a result, the latter simply stick together to form pieces. In this case, the ore is first mixed with coal. As a result of the combustion of the latter, the temperature necessary for obtaining pieces is achieved. The agglomeration process is stimulated by passing air flows through the layer of ore with coal (from top to bottom).

Not only ore can be used to obtain sinter. Sometimes it is also made from small pieces of iron. Its alloy with what substance makes it possible to obtain cast iron will be discussed below. Of course, it is not pig iron that is used to produce this metal. Regular scrap metal is melted down into cast iron.

Device

A homemade furnace for melting metals has a fairly simple design and consists of three main blocks placed in a common body:

The crucible is placed in an inductor, the ends of the winding are connected to a current source. When current flows through the winding, an electromagnetic field with a variable vector appears around it. In a magnetic field, eddy currents arise, directed perpendicular to its vector and passing along a closed loop inside the winding. They pass through the metal placed in the crucible, heating it to the melting point.

Advantages of an induction furnace:

• fast and uniform heating of the metal immediately after turning on the installation;
• direction of heating - only the metal is heated, and not the entire installation;
• high melting speed and melt homogeneity;
• there is no evaporation of metal alloying components;
• The installation is environmentally friendly and safe.

A welding inverter can be used as a generator for an induction furnace for melting metal. You can also assemble a generator using the diagrams below with your own hands.

Furnace for melting metal using a welding inverter

This design is simple and safe, since all inverters are equipped with internal overload protection. The entire assembly of the furnace in this case comes down to making an inductor with your own hands.

It is usually performed in the form of a spiral from a thin-walled copper tube with a diameter of 8-10 mm. It is bent according to a template of the required diameter, placing the turns at a distance of 5-8 mm. The number of turns is from 7 to 12, depending on the diameter and characteristics of the inverter. The total resistance of the inductor must be such as not to cause overcurrent in the inverter, otherwise it will be turned off by the internal protection.

The inductor can be fixed in a housing made of graphite or textolite and a crucible can be installed inside. You can simply place the inductor on a heat-resistant surface. The housing must not conduct current, otherwise eddy currents will pass through it and the power of the installation will decrease. For the same reason, it is not recommended to place foreign objects in the melting zone.

When operating from a welding inverter, its housing must be grounded! The outlet and wiring must be rated for the current drawn by the inverter.

Induction furnace with transistors: diagram

There are many different ways to assemble an induction heater yourself. A fairly simple and proven diagram of a furnace for melting metal is shown in the figure:

To assemble the installation yourself, you will need the following parts and materials:

DIY assembly sequence:

• Field effect transistors are installed on radiators. Since the circuit gets very hot during operation, the radiator must be large enough. You can install them on one radiator, but then you need to isolate the transistors from the metal using gaskets and washers made of rubber and plastic. The pinout of field-effect transistors is shown in the figure.

• It is necessary to make two chokes. To make them, copper wire with a diameter of 1.2 mm is wound around rings removed from the power supply of any computer. These rings are made of powdered ferromagnetic iron. It is necessary to wind from 7 to 15 turns of wire on them, trying to maintain the distance between the turns.

• The capacitors listed above are assembled into a battery with a total capacity of 4.7 μF. The connection of capacitors is parallel.

• The inductor winding is made of copper wire with a diameter of 2 mm. Wrap 7-8 turns of winding around a cylindrical object suitable for the diameter of the crucible, leaving the ends long enough to connect to the circuit.
• Connect the elements on the board in accordance with the diagram. A 12 V, 7.2 A/h battery is used as a power source. The current consumption in operating mode is about 10 A, the battery capacity in this case will last for about 40 minutes. If necessary, the furnace body is made from a heat-resistant material, for example, textolite. The power of the device can be changed by changing the number of turns of the inductor winding and their diameter.

During prolonged operation, the heater elements may overheat! You can use a fan to cool them.

Induction heater for metal melting: video

Induction furnace with lamps

You can assemble a more powerful induction furnace for melting metals with your own hands using electronic tubes. The device diagram is shown in the figure.

To generate high-frequency current, 4 beam lamps connected in parallel are used. A copper tube with a diameter of 10 mm is used as an inductor. The installation is equipped with a tuning capacitor to regulate power. The output frequency is 27.12 MHz.

To assemble the circuit you need:

• 4 vacuum tubes - tetrodes, you can use 6L6, 6P3 or G807;
• 4 chokes at 100...1000 µH;
• 4 capacitors at 0.01 µF;
• neon indicator lamp;
• trimmer capacitor.

Assembling the device yourself:

1. An inductor is made from a copper tube by bending it into a spiral shape. The diameter of the turns is 8-15 cm, the distance between the turns is at least 5 mm. The ends are tinned for soldering to the circuit. The diameter of the inductor should be 10 mm larger than the diameter of the crucible placed inside.
2. The inductor is placed in the housing. It can be made from a heat-resistant, non-conducting material, or from metal, providing thermal and electrical insulation from the circuit elements.
3. Cascades of lamps are assembled according to a circuit with capacitors and chokes. The cascades are connected in parallel.
4. Connect a neon indicator lamp - it will signal that the circuit is ready for operation. The lamp is brought out to the installation body.
5. A variable-capacity tuning capacitor is included in the circuit; its handle is also connected to the housing.

Circuit cooling

Industrial smelting plants are equipped with a forced cooling system using water or antifreeze. Carrying out water cooling at home will require additional costs comparable in price to the cost of the metal melting installation itself.

Air cooling using a fan is possible if the fan is located far enough away. Otherwise, the metal winding and other elements of the fan will serve as an additional circuit for closing eddy currents, which will reduce the efficiency of the installation.

Elements of electronic and lamp circuits can also actively heat up. To cool them, heat sinks are provided.

Main characteristics of brass

Before deciding how to melt brass at home, you need to determine the temperature regime. Copper-based brass alloys in chemical composition are two-component with varying proportions of zinc, and multi-component, containing lead, bismuth and other metals. Knowing the alloy markings, it is easier to determine the exact melting temperature of brass. This data is available in reference tables.

Often you have to use an incomprehensible scrap, it is difficult to determine the grade of metal by color, alloys differ slightly in shades. To melt unmarked scrap, you need to focus on the temperature range of 880–950°C. The less zinc in the composition, the lower the melting point. It is advisable to protect metal, which darkens over time, from oxidation. Such scrap is cleaned to a shine before being melted. The scrap is sprinkled with coal chips. Melting of metal under such a fur coat will proceed faster. It is important to consider that not all alloys have good fluidity; it is sometimes difficult to melt them.

Safety precautions when working

• The main danger when working with a homemade installation is the risk of burns from the heated elements of the installation and molten metal.
• The lamp circuit includes high-voltage elements, so it must be placed in a closed housing to prevent accidental contact with the elements.
• The electromagnetic field can affect objects located outside the device body. Therefore, before work, it is better to wear clothes without metal elements and remove complex devices from the operating area: phones, digital cameras.

It is not recommended to use the device for people with implanted pacemakers!

A furnace for melting metals at home can also be used to quickly heat metal elements, for example, when tinning or forming them. The operating characteristics of the presented installations can be adjusted to a specific task by changing the parameters of the inductor and the output signal of the generating sets - this way you can achieve their maximum efficiency.