Iron ore. How is iron (steel) obtained and from what is it made? How to smelt iron from ore

Processes direct receipt iron from ores

Under the processes of direct production of iron is understood such chemical, electrochemical or chemical-thermal processes that make it possible to obtain directly from the ore, bypassing the blast furnace, metallic iron in the form of a sponge, cracker or liquid metal.

Such processes are carried out without consuming metallurgical coke, fluxes, electricity (for preparation compressed air), and also allow you to get a very pure metal.

Methods for the direct production of iron have been known for a long time. More than 70 different methods have been tried, but only a few have been implemented and, moreover, on a small industrial scale.

In recent years, interest in this problem has grown, which is associated, in addition to replacing coke with other fuels, with the development of methods for deep enrichment of ores, providing not only a high iron content in concentrates (70 ... 72%), but also its almost complete release from sulfur and phosphorus. .

Obtaining sponge iron in shaft furnaces.

The process diagram is shown in fig. 2.1.

Rice. 2.1. Scheme of a plant for the direct reduction of iron from ores and the production of metallized pellets

Upon receipt of sponge iron, the mined ore is enriched and pellets are obtained. The pellets from the hopper 1 through the screen 2 enter the box 10 of the charging machine and from there into the shaft furnace 9 operating on the principle of countercurrent. The spill from the pellets enters the hopper 3 with a briquetting press and in the form of pellets again enters the screen 2 . To reduce iron from pellets, a mixture of natural and blast-furnace gases is fed into the furnace through pipeline 8, subjected to conversion in the installation 7, as a result of which the mixture decomposes into hydrogen and carbon monoxide. In the reduction zone of the furnace C, a temperature of 1000 ... 1100 0 C is created, at which iron ore in pellets is reduced to solid sponge iron. The iron content in the pellets reaches 90...95%. For cooling iron pellets through pipeline 6 to the cooling zone 0 furnaces supply air. Cooled pellets 5 are delivered to conveyor 4 and fed to steel smelting in electric furnaces.

Recovery of iron in a fluidized bed.

Fine-grained ore or concentrate is placed on a grate through which hydrogen or other reducing gas is supplied at a pressure of 1.5 MPa. Under the pressure of hydrogen, the ore particles are in suspension, making continuous movement and forming a "boiling", "pseudo-liquefied" layer. The fluidized bed ensures good contact of the reducing gas with iron oxide particles. Hydrogen consumption per ton of recovered powder is 600...650 m 3 .

Preparation of sponge iron in crucible capsules.

Silicon carbide capsules with a diameter of 500 mm and a height of 1500 mm are used. The charge is loaded in concentric layers. The inside of the capsule is filled with a reducing agent - crushed solid fuel and limestone (10...15%) to remove sulfur. The second layer is recoverable crushed ore or concentrate, mill scale, then another concentric layer of reducing agent and limestone. The capsules mounted on trolleys slowly move in a tunnel oven up to 140 m long, where they are heated, held at 1200 0 C and cooled for 100 hours.

Reduced iron is obtained in the form of thick-walled pipes, they are cleaned, crushed and crushed, obtaining iron powder with an iron content of up to 99%, carbon - 0.1 ... 0.2%.

Steel production

Process essence

Become- iron-carbon alloys containing almost 1.5% carbon, with a higher content, the hardness and brittleness of steels increase significantly and they are not widely used.

The main raw materials for steel production are pig iron and scrap steel(scrap).

Iron is oxidized primarily when iron reacts with oxygen in steelmaking furnaces:

Simultaneously with iron, silicon, phosphorus, manganese and carbon are oxidized. The iron oxide formed at high temperatures gives up its oxygen to more active impurities in cast iron, oxidizing them.

Steelmaking processes are carried out in three stages.

The first stage is the melting of the charge and heating of the liquid metal bath.

The temperature of the metal is relatively low, intense oxidation of iron, the formation of iron oxide and the oxidation of impurities: silicon, manganese and phosphorus.

The most important task of the stage is the removal of phosphorus. For this, it is desirable to conduct melting in the main furnace, where the slag contains. Phosphoric anhydride forms an unstable compound with iron oxide. Calcium oxide is a stronger base than iron oxide, therefore, at low temperatures, it binds and converts it into slag:

To remove phosphorus, a low temperature of the bath of metal and slag, a sufficient content in the slag are required. To increase the content in the slag and accelerate the oxidation of impurities, iron ore and scale are added to the furnace, inducing iron slag. As phosphorus is removed from the metal into the slag, the phosphorus content in the slag increases. Therefore, it is necessary to remove this slag from the metal mirror and replace it with a new one with fresh additives.

The second stage - the boiling of the metal bath - begins as it warms up to higher temperatures.

With an increase in temperature, the oxidation reaction of carbon proceeds more intensively, which occurs with the absorption of heat:

To oxidize carbon, a small amount of ore, scale is introduced into the metal, or oxygen is blown in.

When iron oxide reacts with carbon, bubbles of carbon monoxide are released from the liquid metal, causing a "bath boil". During “boiling”, the carbon content in the metal is reduced to the required level, the temperature is evened out over the volume of the bath, non-metallic inclusions adhering to the emerging bubbles, as well as gases penetrating into the bubbles, are partially removed. All this helps to improve the quality of the metal. Therefore, this stage is the main one in the steelmaking process.

Conditions are also created for the removal of sulfur. Sulfur in steel is in the form of sulfide (), which also dissolves in the main slag. The higher the temperature, the more iron sulfide dissolves in the slag and interacts with calcium oxide:

The resulting compound dissolves in the slag but does not dissolve in the iron, so the sulfur is removed to the slag.

The third stage, steel deoxidation, consists in the reduction of iron oxide dissolved in the liquid metal.

During melting, an increase in the oxygen content in the metal is necessary for the oxidation of impurities, but in finished steel, oxygen is a harmful impurity, since it reduces mechanical properties steel, especially at high temperatures.

Steel is deoxidized in two ways: precipitating and diffusion.

Precipitating deoxidation is carried out by introducing into liquid steel soluble deoxidizers (ferromanganese, ferrosilicon, aluminum) containing elements that have a greater affinity for oxygen than iron.

As a result of deoxidation, iron is reduced and oxides are formed: , which have a lower density than steel and are removed to the slag.

Diffusion deoxidation is carried out by deoxidation of the slag. Ferromanganese, ferrosilicon and aluminum in crushed form are loaded onto the surface of the slag. Deoxidizers, reducing iron oxide, reduce its content in the slag. Consequently, the iron oxide dissolved in the steel turns into slag. The oxides formed during this process remain in the slag, and the reduced iron passes into steel, while the content of non-metallic inclusions in the steel decreases and its quality increases.

Depending on the degree of deoxidation, steels are smelted:

a) calm

b) boiling

c) semi-calm.

Quiet steel is obtained by complete deoxidation in the furnace and ladle.

Boiling steel is not completely deoxidized in the furnace. Its deoxidation continues in the mold during the solidification of the ingot, due to the interaction of iron oxide and carbon:

The resulting carbon monoxide is released from the steel, helping to remove nitrogen and hydrogen from the steel, gases are released in the form of bubbles, causing it to boil. Boiling steel does not contain non-metallic inclusions, therefore it has good ductility.

Semi-calm steel has an intermediate deoxidation between calm and boiling. Partly it is deoxidized in the furnace and in the ladle, and partly in the mold, due to the interaction of iron oxide and carbon contained in the steel.

Alloying of steel is carried out by introducing ferroalloys or pure metals into required quantity into melt. Alloying elements, in which the affinity for oxygen is less than that of iron (), do not oxidize during melting and casting, so they are introduced at any time during melting. Alloying elements that have a greater affinity for oxygen than iron ( ), is introduced into the metal after deoxidation or simultaneously with it at the end of the melt, and sometimes into the ladle.

Steel smelting methods

Cast iron is converted into steel in metallurgical units of various operating principles: open-hearth furnaces, oxygen converters, electric furnaces.

Steel production in open hearth furnaces

Open-hearth process (1864-1865, France). In the period up to the seventies, it was the main method of steel production. The method is characterized by a relatively low productivity, the possibility of using secondary metal - steel scrap. The capacity of the furnace is 200...900 tons. The method makes it possible to obtain high-quality steel.

The open-hearth furnace (Fig. 2.2.) according to the device and principle of operation is a flame reflective regenerative furnace. Gaseous gas is burned in the melting chamber

fuel or oil. The high temperature for obtaining steel in the molten state is provided by the heat recovery of the furnace gases.

A modern open-hearth furnace is a horizontally elongated chamber made of refractory bricks. The working melting space is limited from below by a hearth 12, from above by a vault 11 , and from the sides of the front 5 and back 10 walls. The hearth has the shape of a bath with slopes towards the furnace walls. In the front wall there are loading windows 4 for supplying the charge and flux, and in the back wall there is an opening 9 for the release of finished steel.

Fig.2.2. Scheme of an open-hearth furnace

The characteristic of the working space is the area of ​​the hearth of the furnace, which is calculated at the level of the thresholds of the loading windows. Furnace heads 2 are located at both ends of the melting space, which serve to mix the fuel with air and supply this mixture to the melting space. Natural gas and oil are used as fuel.

For heating air and gas when operating on low-calorie gas, the furnace has two regenerators 1.

Regenerator - a chamber in which a nozzle is placed - a refractory brick laid out in a cage, designed to heat air and gases.

The exhaust gases from the furnace have a temperature of 1500 ... 1600 0 C. Getting into the regenerator, the gases heat the packing to a temperature of 1250 0 C. Air is supplied through one of the regenerators, which, passing through the packing, heats up to 1200 0 C and enters the furnace head, where it mixes with fuel, a torch 7 is formed at the outlet of the head, directed to the charge 6.

Exhaust gases pass through the opposite head (left), cleaning devices (slag tanks), which serve to separate slag and dust particles from the gas, and are sent to the second regenerator.

The cooled gases leave the furnace through the chimney 8.

After the nozzles of the right regenerator are cooled, the valves are switched, and the gas flow in the furnace changes direction.

The temperature of the flame torch reaches 1800 0 C. The torch heats working space furnaces and charge. The torch contributes to the oxidation of charge impurities during melting.

The duration of melting is 3…6 hours, for large furnaces - up to 12 hours. The finished melt is discharged through a hole located in the rear wall at the lower level of the hearth. The hole is tightly clogged with low-caking refractory materials, which are knocked out when the melt is released. The furnaces run continuously until they stop for overhaul- 400 ... 600 melts.

Depending on the composition of the charge used in smelting, there are varieties of the open-hearth process:

- scrap-process, in which the charge consists of steel scrap (scrap) and 25 ... 45% pig pig iron, the process is used at plants where there are no blast furnaces, but there is a lot of scrap metal.

- scrap-ore process, in which the charge consists of liquid iron (55 ... 75%), scrap and iron ore, the process is used at metallurgical plants with blast furnaces.

The lining of the furnace can be basic and acidic. If in the process of melting steel, basic oxides predominate in the slag, then the process is called main open-hearth process, and if sour - sour.

The largest amount of steel is produced by the scrap-ore process in open-hearth furnaces with a basic lining.

Iron ore and limestone are loaded into the furnace, and after heating, scrap is fed. After heating the scrap, liquid iron is poured into the furnace. During the melting period due to oxides of ore and scrap iron impurities are intensively oxidized: silicon, phosphorus, manganese and, partially, carbon. The oxides form a slag with a high content of iron and manganese oxides (iron slag). After that, a period of “boiling” of the bath is carried out: iron ore is loaded into the furnace and the bath is purged with oxygen supplied through pipes 3. At this time, the supply of fuel and air to the furnace is turned off and the slag is removed.

To remove sulfur, new slag is introduced by applying lime to the metal mirror with the addition of bauxite to reduce the viscosity of the slag. The content in the slag increases and decreases.

During the “boiling” period, carbon is intensively oxidized, so the mixture must contain an excess of carbon. On this stage the metal is brought to the specified chemical composition, gases and non-metallic inclusions are removed from it.

Then the metal is deoxidized in two stages. First, deoxidation proceeds by oxidizing the carbon of the metal, while simultaneously supplying deoxidizers - ferromanganese, ferrosilicon, aluminum - into the bath. The final deoxidation with aluminum and ferrosilicon is carried out in the ladle, when the steel is tapped from the furnace. After the selection of control samples, the steel is released into the ladle.

In the main open-hearth furnaces, carbon structural steels, low- and medium-alloyed (manganese, chromium) steels are smelted, except for high-alloy steels and alloys, which are obtained in melting electric furnaces.

High-quality steels are smelted in acid open-hearth furnaces. A mixture with a low content of sulfur and phosphorus is used.

The main technical and economic indicators of steel production in open-hearth furnaces are:

· productivity of the furnace - steel removal from 1 m 2 of hearth area per day (t / m 2 per day), averages 10 t / m 2; R

· fuel consumption per 1 ton of steel being smelted, averages 80 kg/t.

With the enlargement of furnaces, their economic efficiency increases.

Steel production in oxygen converters.

BOF process - steel smelting from liquid iron in a converter with a main lining and oxygen blowing through a water-cooled tuyere.

The first experiments in 1933-1934 - Brain.

IN industrial scale- in 1952-1953 at the factories in Linz and Donawitz (Austria) - was called the LD process. At present, the method is the main one in mass production become.

The oxygen converter is a pear-shaped vessel made of steel sheet, lined with a main brick.

Converter capacity - 130 ... 350 tons of liquid iron. During operation, the converter can rotate 360 ​​0 to load scrap, pour iron, drain steel and slag.

The charge materials of the oxygen-converter process are liquid pig iron, steel scrap (not more than 30%), lime for slag guidance, iron ore, as well as bauxite and fluorspar for slag liquefaction.

Subsequence technological operations when smelting steel in oxygen converters is shown in fig. 2.3.

Fig.2.3. The sequence of technological operations in steelmaking in oxygen converters

After the next melting of steel, the outlet hole is sealed with a refractory mass and the lining is inspected and repaired.

Before melting, the converter is tilted, scrap rice is loaded with the help of filling machines. (2.3.a), cast iron is poured at a temperature of 1250 ... 1400 0 C (Fig. 2.3.b).

After that, the converter is turned to working position(Fig. 2.3.c), a cooled tuyere is inserted inside and oxygen is supplied through it at a pressure of 0.9 ... 1.4 MPa. Lime, bauxite, and iron ore are loaded simultaneously with the start of blowing. Oxygen penetrates the metal, causes it to circulate in the converter and mix with the slag. A temperature of 2400 0 C develops under the tuyere. Iron is oxidized in the zone of contact between the oxygen jet and the metal. Iron oxide dissolves in slag and metal, enriching the metal with oxygen. Dissolved oxygen oxidizes silicon, manganese, carbon in the metal, and their content decreases. The metal is heated by the heat released during oxidation.

Phosphorus is removed at the beginning of the bath purging with oxygen, when its temperature is low (the phosphorus content in cast iron should not exceed 0.15%). With an increased content of phosphorus, to remove it, it is necessary to drain the slag and introduce a new one, which reduces the performance of the converter.

Sulfur is removed during the entire melt (the sulfur content in cast iron should be up to 0.07%).

The oxygen supply is terminated when the carbon content in the metal corresponds to the specified value. After that, the converter is turned and the steel is released into the ladle (Fig. 2.3.d), where it is deoxidized by the precipitation method with ferromanganese, ferrosilicon and aluminum, then the slag is drained (Fig. 2.3.e).

In oxygen converters, steels with various carbon contents, boiling and calm, as well as low-alloy steels are smelted. Alloying elements in molten form are introduced into the ladle before steel is tapped into it.

Iron technology in antiquity

In order to get iron from ore, you first need to get a bloom. For this, oxidized iron ore was first used, which most often occurs near the surface. After the discovery of its properties, such deposits were quickly depleted as a result of their intensive development.

Swamp ores are much more widespread. They were formed in the Subatlantic period, when, in the process of swamping, iron ore settled to the bottom of reservoirs. Throughout the Middle Ages, ferrous metallurgy used swamp ores. They were even paid duties. The production of iron from ore in a relatively large amount became possible after the invention of the cheese forge. This name appeared after the invention of blasting with heated air in blast furnaces. In ancient times, metallurgists fed raw (cold) air into the furnace. At a temperature of 900 o using carbon dioxide, which takes away oxygen from iron oxide, the iron is reduced from the ore and a dough or a shapeless porous piece impregnated with slag is obtained - kritsa. To carry out this process, charcoal was needed as a source of carbon dioxide. The kritz was then forged in order to remove slag from it. The raw-blowing method, sometimes called iron melting, is uneconomical, but for a long time it remained the only and unchanged method for producing ferrous metal.

At first, iron was smelted in ordinary pits closed from above, later they began to build clay furnaces. Crushed ore and coal were loaded into the working space of the furnace in layers, all this was set on fire, and air was injected through the nozzle holes with special (leather) bellows. Rock settles into slag at a temperature of 1300-1400 o , at which steel-iron is obtained, containing from 0.3 to 1.2%. carbon. As it cools, it becomes very hard. To obtain cast iron - fusible iron with a carbon content of 1.5-5% - a more complex hearth design with a large working space is needed. At the same time, the melting point of iron turned out to be lower, and it partially flowed out of the hearth along with the slag. When it cooled, it became brittle, and at first it was thrown away, but then they learned to use it. To get malleable iron from cast iron, carbon must be removed from it.

Technology for creating iron alloys

The first device for obtaining iron from ore was a disposable cheese-blast furnace. With a huge number of shortcomings, for a long time it was the only way to get metal from ore.

Ancient people lived richly and happily for a long time - stone axes were made from jasper, and malachite was burned to obtain copper, but all good things tend to end. One of the reasons for the collapse of the ancient civilization of the Mediterranean was the depletion of mineral resources. Gold ran out not in the treasury, but in the bowels, tin ran out even on the Tin Islands. Although copper is still mined in Sinai and Cyprus, the deposits that are being developed now were not available to the Romans. Among other things, the ore suitable for raw-material processing has also run out. There was just too much lead.

However, the barbarian tribes that settled Europe, which had become ownerless, did not know for a long time that its bowels were depleted by their predecessors. Given the huge drop in the volume of metal production, those resources that the Romans disdained were enough for a long time. Later, metallurgy began to revive primarily in Germany and the Czech Republic - that is, where the Romans did not reach with picks and wheelbarrows.

higher level of development ferrous metallurgy were permanent high ovens called shtukofen in Europe. It really was a tall furnace - with a four-meter pipe to enhance traction. The gizmo bellows were pumped by several people, and sometimes by a water engine. Shtukofen had doors through which the chick was extracted once a day.

Shtukofen were invented in India at the beginning of the first millennium BC. At the beginning of our era, they came to China, and in the 7th century, along with the "Arabic" numerals, the Arabs borrowed this technology from India. At the end of the 13th century, shukofen began to appear in Germany and the Czech Republic (and even before that they were in southern Spain) and spread throughout Europe over the next century.

The performance of the shukofen was incomparably higher than that of a cheese-blast furnace - it produced up to 250 kg of iron per day, and the melting temperature in it turned out to be sufficient to carburize part of the iron to the state of cast iron. However, when the furnace was stopped, the stucco cast iron solidified at its bottom, mixing with slags, and then they knew how to clean the metal from slags only by forging, but cast iron did not succumb to it. It had to be thrown away.

Sometimes, however, they tried to find some use for stucco cast iron. For example, the ancient Indians cast coffins from dirty iron, and the Turks at the beginning of the 19th century cast cannonballs. It is difficult to judge how coffins, but the kernels were obtained from it - so-so.

Cannonballs were cast from ferruginous slag in Europe as early as the end of the 16th century. Roads were made from cast stone blocks. Buildings with foundations made of cast slag blocks are still preserved in Nizhny Tagil.

Metallurgists have long noticed the relationship between the melting point and the yield of the product - the higher it was, the greater part of the iron contained in the ore could be recovered. Therefore, sooner or later, they came up with the idea to force the shtukofen by preheating the air and increasing the height of the pipe. In the middle of the 15th century, a new type of furnace appeared in Europe - blauofen, which immediately presented the steelmakers with an unpleasant surprise.

The higher melting temperature did significantly increase the yield of iron from the ore, but it also increased the proportion of iron carburized to the state of cast iron. Now it is no longer 10%, as in shtukofen, but 30% of the output was cast iron - “pig iron”, not suitable for any business. As a result, the gain often did not pay for the modernization.

Blauofen cast iron, like stucco iron, solidified at the bottom of the furnace, mixing with slag. He came out somewhat better, since he himself was larger, therefore, the relative content of slags came out less, but continued to be of little use for casting. Cast iron obtained from blauofen turned out to be already quite strong, but still remained very heterogeneous - only simple and rough objects came out of it - sledgehammers, anvils. Cannonballs were already well out.

In addition, if only iron could be obtained in raw-blast furnaces, which was then carburized, then in shtukofen and blauofen, the outer layers of the bloom turned out to be made of steel. There was even more steel in the blauofen kritz than iron. On the one hand, it seemed good, but, now, it turned out to be very difficult to separate steel and iron. The carbon content became difficult to control. Only long forging could achieve uniformity of its distribution.

At one time, faced with these difficulties, the Indians did not move on, but engaged in a subtle improvement in technology and came to obtain damask steel. But, the Indians at that time were not interested in the quantity, but in the quality of the product. Europeans, experimenting with cast iron, soon discovered a conversion process that raises iron metallurgy to a qualitatively new level.

The next stage in the development of metallurgy was the appearance of blast furnaces. By increasing the size, preheating the air and mechanical blast, in such a furnace, all the iron from the ore was turned into pig iron, which was melted and periodically released outside. Production became continuous - the furnace worked around the clock and did not cool down. During the day, she gave out up to one and a half tons of cast iron. It was much easier to distill cast iron into iron in the furnaces than to knock it out of the cracker, although forging was still required - but now slags were already knocked out of iron, and not iron from slags.

Blast furnaces were first used at the turn of the XV-XVI centuries in Europe. In the Middle East and India, this technology appeared only in the 19th century (largely, probably because the water engine was not used due to the characteristic water shortage in the Middle East). The presence of blast furnaces in Europe allowed it to overtake Turkey in the 16th century, if not in terms of the quality of the metal, then in terms of the shaft. This had an undoubted influence on the outcome of the struggle, especially when it turned out that cannons could be cast from cast iron.

WITH early XVII century, Sweden became the European forge, producing half of the iron in Europe. In the middle of the 18th century, its role in this regard began to decline rapidly in connection with another invention - the use of coal in metallurgy.

First of all, it must be said that until the 18th century inclusive coal in metallurgy, it was practically not used - due to the high content of impurities harmful to the quality of the product, primarily sulfur. Since the 17th century in England, coal, however, began to be used in puddling furnaces for annealing cast iron, but this made it possible to achieve only a small saving in charcoal - most of the fuel was spent on smelting, where it was impossible to exclude contact between coal and ore.

Among many metallurgical professions At that time, perhaps the most difficult profession was the puddler. Puddling was the main method of obtaining iron for almost the entire 19th century. It was a very difficult and laborious process. The work under him went like this: Ingots of pig iron were loaded onto the hearth of the fiery furnace; they were melted down. As carbon and other impurities burned out of the metal, the melting point of the metal increased and crystals of quite pure iron began to “freeze out” from the liquid melt. A lump of sticky pasty mass was collected on the bottom of the oven. The puddling workers began the operation of rolling up the bloom with the help of an iron crowbar. Stirring a mass of metal with a crowbar, they tried to collect a lump, or kritsa, of iron around the crowbar. Such a lump weighed up to 50 - 80 kg or more. The kritsa was pulled out of the furnace and fed immediately under the hammer - for forging in order to remove slag particles and compact the metal.

They learned to eliminate sulfur by coking in England in 1735, after which the opportunity to use large reserves of coal for iron smelting. But outside of England, this technology spread only in the XIX century.

The consumption of fuel in metallurgy was already enormous at that time - the blast furnace devoured a cartload of coal per hour. Charcoal has become a strategic resource. It was the abundance of wood in Sweden itself and Finland, which belongs to it, that allowed the Swedes to expand production on such a scale. The British, who had fewer forests (and even those were reserved for the needs of the fleet), were forced to buy iron in Sweden until they learned how to use coal.

Electric and induction methods of iron smelting

The variety of steel compositions makes their smelting very difficult. Indeed, in an open-hearth furnace and a converter, the atmosphere is oxidizing, and elements such as chromium are easily oxidized and turn into slag, i.e. are lost. This means that in order to obtain steel with a chromium content of 18%, much more chromium must be fed into the furnace than 180 kg per ton of steel. Chrome is an expensive metal. How to find a way out of this situation?

A way out was found at the beginning of the 20th century. For metal smelting, it was proposed to use the heat of an electric arc. Scrap metal was loaded into a circular furnace, cast iron was poured and carbon or graphite electrodes were lowered. Between them and the metal in the furnace (“bath”) an electric arc with a temperature of about 4000 ° C occurred. The metal melted easily and quickly. And in such a closed electric furnace, you can create any atmosphere - oxidizing, reducing or completely neutral. In other words, valuable items can be prevented from burning out. This is how the metallurgy of high-quality steels was created.

Later, another method of electric melting was proposed - induction. From physics it is known that if a metal conductor is placed in a coil through which a high-frequency current passes, then a current is induced in it and the conductor heats up. This heat is enough to melt the metal in a certain time. The induction furnace consists of a crucible with a spiral embedded in the lining. A high-frequency current is passed through the spiral, and the metal in the crucible is melted. In such a furnace, you can also create any atmosphere.

In electric arc furnaces, the melting process usually takes place in several stages. First, unnecessary impurities are burned out of the metal, oxidizing them (oxidation period). Then, slag containing oxides of these elements is removed (downloaded) from the furnace, and ferroalloys are loaded - iron alloys with elements that need to be introduced into the metal. The furnace is closed and melting is continued without air access (recovery period). As a result, the steel is saturated with the required elements in a given amount. The finished metal is released into a ladle and poured.

Chemical reactions in the production of iron

In modern industry, iron is obtained from iron ore, mainly from hematite (Fe 2 O 3) and magnetite (Fe 3 O 4).

There are various ways to extract iron from ores. The most common is the domain process.

The first stage of production is the reduction of iron with carbon in a blast furnace at a temperature of 2000 °C. In a blast furnace, carbon in the form of coke, iron ore in the form of sinter or pellets, and flux (eg limestone) are fed from above and are met by a stream of injected hot air from below.

In the furnace, the carbon of the coke is oxidized to carbon monoxide (carbon monoxide) by atmospheric oxygen:

2C + O 2 → 2CO.

In its turn, carbon monoxide recovers iron from ore:

3CO + Fe 2 O 3 → 2Fe + 3CO 2.

The flux is added to extract unwanted impurities from the ore, primarily silicates such as quartz (silicon dioxide). A typical flux contains limestone (calcium carbonate) and dolomite (magnesium carbonate). Other fluxes are used against other impurities.

Flux action: calcium carbonate under the action of heat decomposes to calcium oxide (quicklime):

CaCO 3 → CaO + CO 2.

Calcium oxide combines with silicon dioxide to form slag:

CaO + SiO 2 → CaSiO 3.

Slag, unlike silicon dioxide, is melted in a furnace. Lighter than iron, the slag floats on the surface and can be drained separately from the metal. The slag is then used in construction and agriculture. The molten iron obtained in a blast furnace contains quite a lot of carbon (cast iron). Except when cast iron is used directly, it requires further processing.

Excess carbon and other impurities (sulphur, phosphorus) are removed from cast iron by oxidation in open-hearth furnaces or in converters. Electric furnaces are also used for smelting alloyed steels.

In addition to the blast furnace process, the process of direct production of iron is common. In this case, pre-crushed ore is mixed with special clay to form pellets. The pellets are roasted and treated in a shaft furnace with hot methane conversion products containing hydrogen. Hydrogen easily reduces iron, while there is no contamination of iron with impurities such as sulfur and phosphorus - common impurities in coal. Iron is obtained in solid form, and then melted down in electric furnaces.

Chemically pure iron is obtained by electrolysis of solutions of its salts.

First, let me tell you about the quarry itself. Lebedinsky GOK - is the largest Russian enterprise for the extraction and processing of iron ore and has the world's largest open pit for the extraction of iron ore. The plant and quarry are located in the Belgorod region, between the cities of Stary Oskol and Gubkin.

View of the quarry from above. It is really huge and growing every day. The depth of the Lebedinsky GOK quarry is 250 m from sea level or 450 m from the surface of the earth (and the diameter is 4 by 5 kilometers), groundwater constantly seeps into it, and if it were not for the operation of the pumps, it would be filled to the very top in a month. It is twice listed in the Guinness Book of Records as the largest quarry for the extraction of non-combustible minerals.

A little official information: Lebedinsky GOK is part of the Metalloinvest concern and is the leading iron ore producer in Russia. In 2011, the share of concentrate production by the plant in the total annual production of iron ore concentrate and sinter ore in Russia amounted to 21%.

A lot of all kinds of equipment work in the quarry, but the most noticeable of course are the multi-ton Belaz and Caterpillar dump trucks.

In a year, both plants included in the company (Lebedinsky and Mikhailovsky GOK) produce about 40 million tons of iron ore in the form of concentrate and sinter ore (this is not the volume of production, but already enriched ore, that is, separated from waste rock). Thus, it turns out that on average, about 110 thousand tons of enriched iron ore are produced per day at two mining and processing plants.

This kid transports up to 220 tons (!) of iron ore at a time.

The excavator gives a signal and he carefully backs up. Just a few buckets and the giant's body is filled. The excavator once again gives a signal and the dump truck drives off.

Belazs with a carrying capacity of 160 and 220 tons were recently purchased (until now, the load capacity of dump trucks in quarries was no more than 136 tons), and Hitachi excavators with a bucket capacity of 23 cubic meters are expected to arrive. (Currently, the maximum bucket capacity of mining shovels is 12 cubic meters).

"Belaz" and "Caterpillar" alternate. By the way, an imported dump truck transports only 180 tons. Dump trucks of such a large carrying capacity are new equipment that is currently being supplied to mining and processing plants as part of Metalloinvest's investment program to improve the efficiency of the mining and transport complex.

Interesting texture of the stones, pay attention. If I'm not mistaken, quartzite is on the left, iron is mined from such ore. The quarry is full of not only iron ore, but also various minerals. They are generally not of interest for further processing on an industrial scale. Today, chalk is obtained from waste rock, and crushed stone is also made for construction purposes.

Beautiful pebbles, I can’t say for sure what kind of mineral, can someone tell me?

Every day, 133 units of the main mining equipment (30 heavy dump trucks, 38 excavators, 20 burstanks, 45 traction units) operate in the open pit of Lebedinsky GOK.

I certainly hoped to see spectacular explosions, but even if they took place on this day, I still would not have been able to penetrate the territory of the quarry. Such an explosion is done once every three weeks. All equipment, according to safety standards (and there are a lot of them), is removed from the quarry before that.

Lebedinsky GOK and Mikhailovsky GOK are the two largest iron ore mining and processing plants in Russia in terms of output. Metalloinvest has the world's second largest explored iron ore reserves - about 14.6 billion tons of international classification JORC, which guarantees about 150 years of operating life at current production levels. So the residents of Stary Oskol and Gubkin will be provided with jobs for a long time.

You probably noticed from the previous photos that the weather was not good, it was raining, and there was fog in the quarry. Closer to departure, he dissipated a little, but still not much. Pulled out the photo as much as possible. The size of the quarry is certainly impressive.

Right in the middle of the quarry is a mountain with waste rock, around which all the ore containing iron was mined. Soon it is planned to blow it up in parts and take it out of the quarry.

Iron ore is loaded right there into trains, into special reinforced wagons that take ore out of the quarry, they are called dump cars, their carrying capacity is 105 tons.

Geological layers by which one can study the history of the development of the Earth.

Giant machines from the height of the observation deck seem no more than an ant.

Then the ore is transported to the plant, where the waste rock is separated by magnetic separation: the ore is crushed finely, then sent to a magnetic drum (separator), to which, in accordance with the laws of physics, all iron sticks, and not iron is washed off with water. After that, pellets and hot briquetted iron (HBI) are made from the obtained iron ore concentrate, which is then used for steel smelting.
Hot briquetted iron (HBI) is one of the types of direct reduced iron (DRI). A material with a high (>90%) iron content obtained by a technology other than blast furnace. Used as a raw material for steel production. High-quality (with a small amount of harmful impurities) substitute for cast iron, scrap metal.

Unlike pig iron, no coal coke is used in the production of HBI. The production process of briquetted iron is based on the processing of iron ore raw materials (pellets) at high temperatures, most often by means of natural gas.

You can’t just go inside the HBI plant, because the process of baking hot-briquetted pies takes place at a temperature of about 900 degrees, and I didn’t plan to sunbathe in Stary Oskol).

Lebedinsky GOK is the only HBI producer in Russia and the CIS. The plant started the production of this type of product in 2001 by launching a shop for the production of HBI (CHBI-1) using HYL-III technology with a capacity of 1.0 million tons per year. In 2007, LGOK completed the construction of the second stage of the HBI production plant (CHBI-2) using MIDREX technology with a production capacity of 1.4 million tons per year. Currently productive capacity LGOK is 2.4 million tons of HBI per year.

After the quarry, we visited the Oskol Electrometallurgical Plant (OEMK), which is part of the Metallurgical segment of the company. In one of the workshops of the plant, such steel billets are produced. Their length can reach from 4 to 12 meters, depending on the wishes of customers.

See a sheaf of sparks? In that place, a bar of steel is cut off.

An interesting machine with a bucket, called a bucket wagon, slag is poured into it during the production process.

In the adjacent workshop of OEMK, steel bars of different diameters, which have been rolled in another workshop, are turned and polished. By the way, this plant is the seventh largest enterprise in Russia for the production of steel and steel products. In 2011, the share of steel production at OEMK amounted to 5% of the total volume of steel produced in Russia, the share of rolled products also amounted to 5%.

OEMK uses advanced technologies, including direct reduction of iron and electric arc melting, which ensures the production of high quality metal with a reduced content of impurities.

The main consumers of OEMK steel products in Russian market are enterprises of the automotive, machine-building, pipe, hardware and bearing industries.

OEMK steel products are exported to Germany, France, USA, Italy, Norway, Turkey, Egypt and many other countries.

The plant has mastered the production of long products for the manufacture of products used by the world's leading automakers, such as Peugeot, Mercedes, Ford, Renault, Volkswagen. Bearings for these same foreign cars are made from some products.

By the way, this is not the first time I notice women - crane operators in such industries.

At this plant, almost sterile cleanliness, not typical for such industries.

Like neatly folded steel bars.

At the request of the customer, a sticker is glued to each product.

The heat number and steel grade code are stamped on the sticker.

The opposite end can be marked with paint, and for each package to finished goods tags are attached with the contract number, country of destination, steel grade, heat number, size in millimeters, supplier name and package weight.

These products are the standards by which the equipment for precision rolling is adjusted.

And this machine can scan the product and identify microcracks and defects before the metal gets to the customer.

The company takes safety very seriously.

All water used in the production is purified by the most recently installed state-of-the-art equipment.

This is a cleaning unit. Wastewater plant. After processing, it is cleaner than in the river where it is dumped.

Technical water, almost distilled. Like any process water you can’t drink it, but you can try it once, it’s not dangerous to health.

The next day we went to Zheleznogorsk, located in the Kursk region. It is there that the Mikhailovsky GOK is located. The photo shows the complex of roasting machine No. 3 under construction. Here pellets will be produced.

450 million dollars will be invested in its construction. The enterprise will be built and put into operation in 2014.

This is the layout of the plant.

Then we went to the quarry of the Mikhailovsky GOK. The depth of the MGOK quarry is more than 350 meters from the earth's surface, and its size is 3 by 7 kilometers. There are actually three quarries on its territory, this can be seen in the satellite image. One large and two smaller. In about 3-5 years, the quarry will grow so much that it will become one big single one, and possibly catch up with the Lebedinsky quarry in size.

The quarry employs 49 dump trucks, 54 traction units, 21 diesel locomotives, 72 excavators, 17 drilling rigs, 28 bulldozers and 7 motor graders.

Otherwise, ore mining at MGOK does not differ from LGOK.

This time we still managed to get to the plant, where iron ore concentrate is converted into final product- pellets..
Pellets are lumps of crushed ore concentrate. Semi-finished product of metallurgical production of iron. It is a product of enrichment of iron-bearing ores by special concentrating methods. It is used in blast-furnace production to produce pig iron.

For the production of pellets, iron ore concentrate is used. To remove mineral impurities, the original (raw) ore is finely crushed and enriched in various ways.

The process of making pellets is often referred to as "pelletizing". The mixture, that is, a mixture of finely divided concentrates of iron-containing minerals, flux (additives that regulate the composition of the product), and hardening additives (usually bentonite clay), is moistened and pelletized in rotating bowls (granulators) or pelletizing drums. They are the most in the picture.

Let's get closer.

As a result of pelletizing, close to spherical particles with a diameter of 5÷30 mm are obtained.

Quite interesting to watch the process.

The pellets are then guided along the belt into the firing chamber.

They are dried and fired at temperatures of 1200 ÷ 1300 ° C on special installations - firing machines. Roasting machines (usually conveyor type) are a conveyor of firing carts (pallets) that move along rails.

But in the picture - a concentrate, which will soon fall into the drums.

In the upper part of the roasting machine, above the roasting carts, a heating hearth is located, in which gaseous, solid or liquid fuels are burned and a heat carrier is formed for drying, heating and roasting pellets. There are roasting machines with pellet cooling directly on the machine and with an external cooler. Unfortunately, we did not see this process.

Roasted pellets acquire high mechanical strength. Roasting removes a significant part of the sulfurous contaminants. This is what the finished product looks like.

Despite the fact that the equipment has been in service since Soviet times, the process is automated and does not require a large number of personnel to control it.

Known to mankind was of cosmic origin, or, more precisely, meteoric. As an instrumental material, it began to be used approximately 4 thousand years BC. The technology of metal smelting appeared several times and was lost as a result of wars and unrest, but, according to historians, the Hittites were the first to master smelting.

It is worth noting that we are talking about iron alloys with a small amount of impurities. Chemically pure metal became possible to obtain only with the advent of modern technologies. This article will tell you in detail about the features of metal production by direct reduction, bloomery, spongy, raw iron, hot briquetted iron, we will touch on the manufacture of chlorine and pure substances.

To begin with, it is worth considering the method of producing iron from iron ore. Iron is a very common element. In terms of content in the earth's crust, metal ranks 4th among all elements and 2nd among metals. In the lithosphere, iron is usually present in the form of silicates. Its highest content is noted in basic and ultrabasic rocks.

Almost all mountain ores contain some fraction of iron. However, only those rocks are developed in which the proportion of the element has industrial value. But even in this case, the amount of minerals suitable for mining is more than large.

• First of all, this iron ore- red (hematite), magnetic (magnetite) and brown (limonite). These are complex iron oxides with an element content of 70–74%. Brown iron ore is more common in weathering crusts, where it forms the so-called "iron hats" up to several hundred meters thick. The rest are mainly of sedimentary origin.
• Very common iron sulfide- pyrite or sulfur pyrites, however, it is not considered iron ore and is used to produce sulfuric acid.
• Siderite- iron carbonate, includes up to 35%, it is an ore with an average content of the element.
• Marcasite- includes up to 46.6%.
• mispikel- compound with arsenic and sulfur, contains up to 34.3% iron.
• Lellingite- includes only 27.2% of the element and is considered poor ore.

Mineral rocks are classified according to the proportion of iron in this way:

• rich- with a metal content of more than 57%, with a silica content of less than 8–10%, and an admixture of sulfur and phosphorus of less than 0.15%. Such ores are not enriched, they are immediately sent to production;
• medium grade ore contains at least 35% of the substance and needs to be enriched;
• poor iron ores must contain at least 26%, and are also enriched before being sent to the workshop.

The general technological cycle for the production of iron in the form of cast iron, steel and rolled products is discussed in this video:

Mining

There are several methods for extracting ore. Apply the one that finds the most cost-effective.

• Open development method or career. Designed for shallow occurrence of mineral rock. For mining, a quarry is dug up to a depth of 500 m and a width depending on the thickness of the deposit. The iron ore is extracted from the quarry and transported by vehicles designed to carry heavy loads. As a rule, rich ore is mined in this way, so there is no need to enrich it.
• Mine- when the rock occurs at a depth of 600–900 m, mines are drilled. Such a development is much more dangerous, since it is associated with explosive underground work: the discovered layers are blown up, and then the collected ore is transported upward. For all its danger, this method is considered more effective.
• Hydro mining- in this case, wells are drilled to a certain depth. Pipes are lowered into the mine and water is supplied under very high pressure. The water jet crushes the rock, and then the iron ore is lifted to the surface. Borehole hydroextraction is not widespread, as it requires high costs.

Iron production technologies

All metals and alloys are divided into non-ferrous (like, etc.) and black. The latter include cast iron and steel. Ferrous metallurgy accounts for 95% of all metallurgical processes.

Despite the incredible variety of steels produced, there are not so many manufacturing technologies. In addition, iron and steel are not exactly 2 different products, pig iron is an obligatory preliminary stage in obtaining steel.

Product classification

Both cast iron and steel are classified as iron alloys, where carbon acts as an alloying component. Its share is small, but it gives the metal a very high hardness and some brittleness. Cast iron, because it contains more carbon, is more brittle than steel. It is less plastic, but has better heat capacity and resistance to internal pressure.

Pig iron is obtained by blast-furnace smelting. There are 3 types:

• gray or cast- obtained by slow cooling. The alloy contains from 1.7 to 4.2% carbon. Gray cast iron it is well processed with mechanical tools, perfectly fills the molds, so it is used for the production of injection molded products;
• white- or refining, obtained by rapid cooling. The share of carbon is up to 4.5%. May include additional impurities, graphite, manganese. White cast iron is hard and brittle and is mainly used for steelmaking;
• malleable- includes from 2 to 2.2% carbon. It is made from white cast iron by long-term heating of castings and slow long-term cooling.

Steel can include no more than 2% carbon, it is obtained in 3 main ways. But in any case, the essence of steelmaking comes down to annealing unwanted impurities of silicon, manganese, sulfur, and so on. In addition, if alloy steel is obtained, then additional ingredients are introduced during the manufacturing process.

By purpose, steel is divided into 4 groups:

• construction- used in the form of rental without heat treatment. This is a material for the construction of bridges, frames, the manufacture of wagons, and so on;
• engineering- structural, belongs to the category of carbon steel, includes no more than 0.75% carbon and no more than 1.1% manganese. Used to produce a variety of machine parts;
• instrumental- also carbonaceous, but with a low manganese content - no more than 0.4%. A variety of tools are produced from it, in particular, metal-cutting;
• special purpose steel- this group includes all alloys with special properties: heat-resistant steel, stainless steel, acid-resistant and so on.

preliminary stage

Even rich ore must be prepared before smelting iron - freed from waste rock.

• Agglomeration method– the ore is crushed, ground and poured together with coke onto the belt of the sintering machine. The ribbon passes through the burners, where the coke ignites under the influence of temperature. In this case, the ore is sintered, and sulfur and other impurities burn out. The resulting agglomerate is fed into the bunker bowls, where it is cooled with water and blown with an air stream.
• Magnetic separation method- the ore is crushed and fed to the magnetic separator, since iron has the ability to be magnetized, the minerals remain in the separator when washed with water, and the waste rock is washed out. Then, pellets and hot briquetted iron are made from the resulting concentrate. The latter can be used for the preparation of steel, bypassing the stage of obtaining cast iron.

This video will tell you in detail about the production of iron:

Iron smelting

Cast iron is smelted from ore in a blast furnace:

• charge is prepared - sinter, pellets, coke, limestone, dolomite and so on. The composition depends on the type of cast iron;
• the charge is loaded into the blast furnace by a skip hoist. The temperature in the furnace is 1600 C, hot air is supplied from below;
• at this temperature, the iron begins to melt, and the coke burns. In this case, iron is reduced: first, carbon monoxide is obtained during the combustion of coal. Carbon monoxide reacts with iron oxide to produce pure metal and carbon dioxide;
• flux - limestone, dolomite, is added to the mixture to transfer unwanted impurities into a form that is easier to eliminate. For example, silicon oxides do not melt at such a low temperature and it is impossible to separate them from iron. But when interacting with calcium oxide, obtained by the decomposition of limestone, quartz turns into calcium silicate. The latter melts at this temperature. It is lighter than cast iron and stays floating on the surface. It is quite simple to separate it - the slag is periodically released through tapholes;
• liquid iron and slag flow into the ladles through different channels.

The resulting pig iron in ladles is transported to the steel shop or to the casting machine, where pig iron ingots are obtained.

steel smelting

The transformation of cast iron into steel is done in 3 ways. In the process of smelting, excess carbon, unwanted impurities are burned out, and the necessary components are added - when cooking special steels, for example.

• Open-hearth is the most popular production method, as it provides high quality steel. Molten or hard iron with the addition of ore or scrap is fed into an open-hearth furnace and melted. The temperature is about 2000 C, maintained by the combustion of gaseous fuel. The essence of the process is to burn out carbon and other impurities from iron. The necessary additives, if we are talking about alloyed steel, are added at the end of the smelting. finished product poured into ladles or into ingots in molds.

• Oxygen-envelope method - or Bessemer. Features higher performance. The technology includes blowing compressed air through the thickness of cast iron at a pressure of 26 kg/sq. see At the same time, carbon burns out, and cast iron becomes steel. The reaction is exothermic, so that the temperature rises to 1600 C. To improve the quality of the product, a mixture of air with oxygen or even pure oxygen is blown through the cast iron.
• The electrosmelting method is considered the most effective. Most often it is used to obtain multi-alloyed steels, since the smelting technology in this case excludes the ingress of unnecessary impurities from air or gas. The maximum temperature in the iron production furnace is reached - about 2200 C due to the electric arc.

Direct Receive

Since 1970, the method of direct reduction of iron has also been used. The method makes it possible to bypass the costly stage of producing cast iron in the presence of coke. The first installations of this kind did not differ in productivity, but today the method has become quite well-known: it turned out that natural gas can be used as a reducing agent.

The raw material for recovery is pellets. They are loaded into a shaft furnace, heated and purged with a gas conversion product - carbon monoxide, ammonia, but mostly hydrogen. The reaction takes place at a temperature of 1000 C, while hydrogen reduces iron from oxide.

We will talk about manufacturers of traditional (not chlorine, etc.) iron in the world below.

Notable Manufacturers

The largest share of iron ore deposits is in Russia and Brazil - 18%, Australia - 14%, and Ukraine - 11%. The largest exporters are Australia, Brazil and India. The peak of the cost of iron was observed in 2011, when a ton of metal was estimated at $180. By 2016, the price had fallen to $35 per ton.

The largest iron producers include the following companies:

• Vale S. A. is a Brazilian mining company, the largest producer of iron and;
• BHP Billiton is an Australian company. Its main direction is oil and gas production. But at the same time, it is also the largest supplier of copper and iron;
• Rio Tinto Group is an Australian-British concern. Rio Tinto Group mines and produces gold, iron, diamonds and uranium;
• Fortescue Metals Group is another Australian mining and iron company;
• In Russia, the largest producer is Evrazholding, a metallurgical and mining company. Metallinvest and MMK are also known on the world market;
• Metinivest Holding LLC is a Ukrainian mining and metallurgical company.

The prevalence of iron is high, the method of extraction is quite simple, and smelting is ultimately an economically profitable process. Together with the physical characteristics, the production provides iron with the role of the main structural material.

Making ferric chloride is shown in this video:

The production of iron in Rus' has been known since time immemorial. As a result of archaeological excavations in the areas adjacent to Novgorod, Vladimir, Yaroslavl, Pskov, Smolensk, Ryazan, Murom, Tula, Kiev, Vyshgorod, Pereyaslavl, Vzhishch, as well as in the area of ​​Lake Ladoga and in other places, hundreds of places with the remains of melting pots were found , raw furnaces, the so-called "wolf pits" and the corresponding tools for the production of ancient metallurgy. In one of the wolf pits, dug out for iron smelting, near the village of Podmokly in the southern part of the Moscow coal basin, a coin was found dated 189 of the Muslim era, which corresponds to the beginning of the 9th century of modern chronology. This means that in Rus' they knew how to smelt iron back in those distant, deeply pre-Christian times.

The names of the Russian people literally scream to us about the prevalence of metallurgy throughout the territory of ancient Rus': Kuznetsov, Kovalev, Koval, Kovalenko, Kovalchuk. In terms of prevalence, Russian "metallurgical" surnames, perhaps, compete even with the archetypal English John Smith (who, in fact blacksmith, that is, the same blacksmith).

However, the path of any sword or cannon barrel always began much earlier. metallurgical furnace and, especially, forges. Any metal is primarily a fuel (coal or coke for its smelting), and secondarily a raw material for its production.

Here I must immediately place emphasis. Why is fuel the first priority, while iron ore itself is so boldly relegated by me to the background? It's all about the logistics of transporting the ore and fuel needed to produce iron in the Middle Ages.

After all, the main, and the most high-quality fuel for the smelting of medieval, bloomery iron, was charcoal.
Even now, in the modern enlightened age, the task of obtaining high-quality charcoal is by no means as simple as it seems at first glance.
The highest quality charcoal is obtained only from a very limited number of wood species - from all fairly rare and slowly growing hardwood species (oak, hornbeam, beech) and from the archetypal Russian birch.
Already from conifers - pine or spruce, charcoal is much more fragile and with a large yield of fines and coal dust, and trying to get good charcoal from soft-leaved aspen or alder is almost unrealistic - the yield of good one falls almost twice compared to oak.

In the event that there were not enough forests in the territory where iron deposits were found, or the forests in the area were destroyed by previous generations of metallurgists, various ersatz substitutes had to be invented.
For example, in Central Asia, despite high-quality iron ore deposits, it was tight with the forest, which is why instead of charcoal it was necessary to use the following innovative fuel:

If someone does not understand - this is cow dung. You can horse, mutton, goat or donkey - it does not play a special role. Kizyak was kneaded with hands into flat cakes (something like this), and then laid out to dry in the sun.
Of course, in such a situation, it was not necessary to talk about the "constancy of the composition" of the fuel, and the temperature of the flame from the combustion of such a "composite fuel" was much lower than that of high-quality charcoal.

Another, much more technologically advanced replacement for charcoal appeared in the world much later. It is, of course, about coke on which all modern ferrous metallurgy is now based.
The history of the "invention" of coke is only two hundred years old. After all, it was the coke oven battery in which "coal burned itself out" that was the first, most powerful volley of the industrial revolution. It was she, the coke oven battery, and not the oil rig, who created that "world of coal and steam" that we now love to remember in books, films and anime about steampunk.

Long before the Industrial Revolution, England was already exploiting rich deposits of hard coal, which, however, was used almost exclusively for heating houses. The smelting of ore in England was carried out, as in many places in the world, only on charcoal. This was due to an unpleasant fact, characteristic of most coals - they contain in their composition considerable amounts of phosphorus and sulfur, which are very harmful to the iron obtained in the furnace.

However, Great Britain is an island. And, ultimately, the growing needs of English metallurgy, based on charcoal, surpassed all the possibilities of English forests. English Robin Hoods had nowhere to hide- an increase in iron smelting has brought to naught almost all the forests of foggy Albion. This eventually became a brake on iron production, as smelting required a huge amount of wood: for the processing of one ton of ore - almost 40 cubic meters of wood raw materials.
In connection with the increasing production of iron, there was a threat of complete destruction of forests. The country was forced to import metal from abroad, mainly from Russia and Sweden. Attempts to use fossil coal for iron smelting were unsuccessful for a long time, for the reason indicated above.
It was not until 1735 that the breeder Abraham Derby, after many years of experience, found a way to smelt iron using coking coal. It was a victory. But before this victory at the beginning of the 9th century AD, there were still more than 900 years.

So, carry firewood (or even ready-made charcoal) to iron does not work simply because of the logistics of the process - fuel is needed by mass 4-5 times more than the mass of ore, and even more by volume - at least ten times. It is easier to bring iron to fuel.

Fuel in Ancient Rus' is, and in abundance. And what about the Russian platform with iron?
But with iron there are questions.
quality iron ore not on the Russian Plain.

I immediately catch screams: “What about the Kursk magnetic anomaly? The highest quality magnetic iron ore in the world!
Yes, one of the highest quality in the world. Opened in 1931. The depth of occurrence is from 200 to 600 meters. The task is clearly not for the technologies that were at the disposal of the ancient Slavs in the 9th century AD. It all looks beautiful now, but for that time the picture of a modern iron ore quarry is like a trip to Alpha Centauri for modern humanity. In theory it's possible, but in practice it's not.

As a result, in the 9th century in Rus', it is necessary to make a choice from something included in this list of all the iron ores currently used by mankind:

Magnetic iron ore - more than 70% Fe in the form magnetite Fe3O4 (example: the Kursk magnetic anomaly just described by us)
- red iron ore - 55-60% Fe in the form hematite Fe2O3 (example: again the Kursk magnetic anomaly or the Krivoy Rog basin)
- brown iron ore (limonite) - 35-55% Fe in the form mixtures of hydroxides ferric iron Fe2O3-3H2O and Fe2O3-H2O (example: ruined by Ukraine Kerch deposit).
- spar iron ore - up to 40% Fe in the form carbonate FeCO3 (example: Bakal deposit)

Magnetite and hematite lie deep on the Russian platform; there is no feldspar iron ore on it at all.
Remains brown iron ore (limonite).
The raw material, to put it mildly, is worthless - just look at the concentration of iron in it, but the joke is that it is on the territory of the then Rus' almost everywhere. In addition, this "almost everywhere" miraculously turns out to be in close proximity to the then source of high-quality coal fuel - the mighty forests of the Russian Plain.

This, of course, is about peat bogs and limonite, which is often called swamp iron.
In addition to marsh iron, a similar genesis has meadow and lake iron. However, as you will see later, it was most profitable to dig such iron in a swamp.

To understand the breadth of the distribution of the actual production of this local resource in Rus', it is enough, as in the case of "metallurgical families", simply to open any geographical map and look at the names of Russian, Ukrainian, Belarusian or Lithuanian villages.
And immediately you will be struck by a huge number of toponyms with the words Guta, Buda, Ruda. Here are their meanings:

Guta: glass factory
Ore: swamp iron mining
Buda: the extraction of potash from plant ash.

You will find such villages everywhere - in a wide belt in the Polesye swamps - from Brest to Sumy. There were plenty of sources of "bog ore" in Rus'. "Swamp iron" is generally formed almost everywhere where there is a transition from oxygen-containing soils to an anoxic layer (exactly at the junction of these two layers).
In swamps, this border is simply located, unlike other types of terrain, very close to the surface, so there iron nodules can be literally dug with a shovel, only removing thin layer swamp vegetation.

This is how swamp iron looks unpretentious (bog iron) .
But it was it that saved Rus'.

Bog iron deposits themselves are classic placers.
Placers are usually much smaller deposits than ore bodies, their total volume rarely exceeds tens of thousands of tons (while ore deposits can contain millions and billions of tons of ore), but the mining of placers is usually much simpler than mining an ore body.
The placer can usually be developed almost with bare hands and with minimal crushing of the rock, since placers usually occur in already destroyed, sedimentary rocks.
This is generally a widespread practice: first placers are mined - then ores.
And - for all metals, minerals or compounds.

By the way, "wooden tin" (which I wrote about in the series about the Bronze Age Catastrophe) is also a placer.

However, it cannot be said that the mining of placers of swamp iron was a simple task.

Swamp iron was mined in three main ways.

The first one was that in the summer, bottom silt was scooped from rafts on swamp lakes and on rivers flowing from swamps. The raft was held in one place by a pole (one person) and another person pulled mud from the bottom with a scoop. The advantages of this method are simplicity, and low physical exertion on workers.
The disadvantages are a large amount of useless labor, since not only was waste rock scooped up with swamp iron, but in addition, large amounts of water had to be raised up along with silt. In addition, with a scoop it is difficult to choose the soil to a great depth.

The second way. In winter, in places where the channels froze to the bottom, ice was cut first, and then the bottom sediment containing bog iron was also cut down. The advantages of this method: the ability to select a large layer containing bog iron. Disadvantages: it is physically difficult to gouge ice and frozen ground. Mining is possible only to the depth of freezing.

The third method was the most common. On the shore near the channels or marsh lakes, a log house was assembled, as for a well, only large, for example, 4 by 4 meters. Then, inside the log house, they began to dig out, first, the covering layer of waste rock, gradually deepening the log house. Then the rock containing bog iron was also selected. Log rolls were added as the log house deepened.
Constantly flowing water was periodically scooped out. It was possible, of course, to simply dig without strengthening the walls with logs, but in the event of a very likely shedding of the eroded soil and workers falling asleep in the pit, it would hardly have been possible to save anyone - people would quickly choke and drown. Advantages of this method: the ability to select the entire layer containing bog iron, and lower labor costs compared to the second method. In addition, even before the start of mining, it was possible to approximately determine the quality of the raw materials being mined (“the local inhabitants also judge the goodness of the ore by the kind of trees growing on it; thus, the one found under birch and aspen is considered the best, because iron is softer from it, and in places where spruce grows, it is tougher and stronger").
Disadvantages: you have to work in the water all the time.

In general, the ancient Russian miners had a hard time. Now, of course, reenactors around the world are doing field trips and even digging holes in drier and more accessible places where you can easily get some swamp ore:

Children of reenactors are happy. In the 9th century, everything was, I think, different.

However, in order to understand the situation in Rus' in the 9th-12th centuries, one must understand scale of the fishery that was organized by our ancestors on such an overwhelmed resource as swamp placers.

After all, if the process of digging silt in the swamps itself did not leave behind any traces that can be traced through the centuries, then the subsequent processing of marsh iron left traces in the cultural layer, and even what!

After all, for the cheese-making process, which at that time was used in ancient Russian metallurgy and produced high-iron slag, it was necessary very rich iron ore. And limonite, as we remember, is a poor ore.
To obtain a good concentrate of limonite, it was necessary to pre-enrich the mined ores, both marsh and meadow. Therefore, ancient Russian metallurgists necessarily enriched swamp iron ores going into smelting.

The beneficiation operation was a very important technological condition for the production of iron in raw furnaces.
Later studies, through the analysis of historical monuments, revealed the following methods of ore dressing:

1) drying (weathering, within a month);
2) firing;
3) crushing;
4) washing;
5) screening.

Obtaining highly concentrated ore could not be limited to only one or two operations, but required systematic processing by all the indicated methods. An archaeologically well-known operation is the roasting of ore.
As you understand, firing also required high-quality fuel (charcoal), and also in considerable quantities.

During archaeological exploration near the village of Lasuny on the coast of the Gulf of Finland, a pile of burnt ore was discovered in one of the pits. For all operations of ore dressing, very simple equipment is required: for crushing ore - a wooden block and a mortar, and for sifting and washing - a wooden sieve (net of rods).
The disadvantage of burning swamp ore in fires and pits was the incomplete removal of water from it when burning large pieces and large losses when burning small pieces.

IN modern production, of course, enrichment is much simpler - finely crushed ore is mixed with the same ground coke and fed into an apparatus similar to a large meat grinder. The auger feeds a mixture of ore and coke onto a grate with holes no larger than 8 mm. Squeezing out through the holes, such a homogeneous mixture enters the flame, while the coke burns out, melting the ore, and in addition, sulfur is burned out of the ore, thus simultaneously desulphurizing the raw material.

After all, marsh iron, like coal, contains harmful impurities - sulfur and phosphorus. It was possible, of course, to find raw materials containing little phosphorus (well, relatively little - in the ore iron it is still always less than in the swamp). But to find swamp iron containing little of both phosphorus and sulfur was almost impossible. Therefore, in addition to the whole industry of mining swamp iron, an equally large-scale industry of its enrichment arose.

To understand the scope of this action, I will give one example: during excavations in Old Ryazan in 16 out of 19 urban dwellings traces of "home" cooking of iron in pots in an ordinary furnace were found.
Western European traveler Yakov Reitenfels, having visited Muscovy in 1670, wrote that "the country of the Muscovites is a living source of bread and metal."

So, in a bare place, with nothing under them but poor forest soils with stunted birch trees and peat bogs, suddenly our ancestors found a “gold mine” literally under their feet. And even though it was not a vein, but a placer and not gold, but iron, the situation did not change from this.

A country that is only just emerging has received its place in the world and a civilizational path that will lead it to the cannons of Balaklava, to the T-Z4 tank and to the Topol-M ICBM.
Resources. Job. Production. Weapon.

Because having resources - you inevitably come to arms. Or - someone else comes for your resources.
The Iron Age began in Rus'.
Century - or rather - the millennium of Russian weapons.

A millennium in which the sword will rise - and fall again, after another enemy is defeated and thrown away from birch forests and peat bogs.

And the enemies were not long in coming.
Indeed, in the 10th century, the Iron Age arms race was already gaining momentum.