On earth it was valued much more than gold. The Soviet historian G. Areshyan studied the influence of iron on the ancient culture of the Mediterranean countries.

He gives the following proportion: 1:160: 1280: 6400. This is the ratio of the cost of copper, silver, gold and iron among the ancient Hittites. As Homer testifies in the Odyssey, the winner of the games arranged by Achilles was rewarded with a piece of gold and a piece of iron.

It was equally necessary for both the warrior and the plowman, and practical need, as you know, is the best engine of production and technical progress.

The term "Iron Age" was introduced into science in the middle of the 19th century. Danish archaeologist K. Yu. Thomsen. "Official" boundaries of this period of human history: from IX-VII centuries. BC e. when iron metallurgy began to develop among many peoples and tribes of Europe and Asia, and until the time when a class society and state arose among these tribes. But if the eras are named according to the main material of the tools, obviously, the Iron Age continues today.

How did our distant ancestors receive? First, the so-called cheese-making method. Cheese kilns were arranged right on the ground, usually on the slopes of ravines and ditches. They looked like pipes. This pipe was filled with charcoal and iron ore. Coal was lit, and the wind blowing into the slope of the ravine kept the coal burning.

Iron ore was reduced, and soft iron was obtained - iron with slag inclusions. Such iron is called welding; it contained some carbon and impurities transferred from the ore. The hammer was forged, pieces of slag fell off, and under the hammer there was iron, pierced with slag threads. Various tools were forged from it.

The age of wrought iron was long, but people of antiquity and the early Middle Ages were also familiar with other iron. The famous Damascus steel (or damask steel) was made in the East back in the time of Aristotle (4th century BC). But the technology of its production, as well as the process of making damask blades, was kept secret for many centuries.

From house to house

The cheese-making process largely depended on the weather: it was necessary that the wind must blow into the “pipe”. The desire to get rid of the vagaries of the weather led to the creation of bellows, which fanned the fire in a raw furnace. With the advent of bellows, there was no longer any need to build raw furnaces on the slopes. A new type of furnace appeared - the so-called wolf pits, which were dug in the ground, and blast furnaces, which towered above the ground. They were made from stones held together with clay. A tube of bellows was inserted into the hole at the base of the domnitsa and the furnace began to be inflated. Coal burned out, and in the hearth of the furnace there was already a cry familiar to us. Usually, in order to pull it out, they broke out several stones at the bottom of the furnace. Then they were laid back in place, the furnace was filled with coal and ore, and everything started all over again.

The word "domnitsa" itself comes from the Slavic word "dmuti", which means "to blow". The words "arrogant" (inflated) and "smoke" come from the same word. In English, a blast furnace is called, like in Russian, a blast furnace. And in French and German, these stoves are called high (Hochofen in German and haut fourneau in French).

Dominica became more and more. The productivity of furs increased; coal burned hotter, and iron was saturated with carbon.

When the cracker was removed from the furnace, molten cast iron was also poured out - iron containing more than 2% carbon and melting at lower temperatures. In solid form, cast iron cannot be forged; it shatters into pieces from one blow with a hammer. Therefore, cast iron, like slag, was initially considered a waste product. The British even called it "pig iron" - pig iron. Only later did metallurgists realize that liquid iron could be poured into molds and various products, such as cannonballs, could be obtained from it.

By the XIV-XV centuries. blast furnaces that produced pig iron quickly entered the industry. Their height reached 3 m or more, they smelted foundry iron, from which not only the cores were poured, but also the cannons themselves.

The real turn from the blast furnace to the blast furnace took place only in the 80s of the 18th century, when one of Demidov's clerks came up with the idea of ​​blowing into the blast furnace not through one nozzle, but through two, placing them on both sides of the hearth. Down and Out trouble started! The number of nozzles, or lances (as they are now called), grew, the blast became more and more uniform, the diameter of the hearth increased, and the productivity of the furnaces increased.

Two more discoveries greatly influenced the development of blast-furnace production. For many years blast furnaces were fueled by charcoal. There was a whole industry dedicated to burning coal from wood. As a result, the forests in England were cut down to such an extent that a special decree was issued by the Queen forbidding the destruction of the forest for the needs of the iron and steel industry. After that, English metallurgy began to decline rapidly. Britain was forced to import pig iron from abroad, mainly from Russia. This continued until the middle of the 18th century, when Abraham Derby found a way to obtain coke from coal, the reserves of which in England are very large. Coke became the main fuel for blast furnaces.

The invention of coke is associated with the legend of Dade Dudley, who allegedly invented coking in the 16th century, long before Derby. But the charcoal manufacturers were afraid for their income and, having agreed, killed the inventor.

In 1829, J. Nilson at the Kleid plant (Scotland) first applied heated air blowing into blast furnaces. This innovation increased the productivity of furnaces and dramatically reduced fuel consumption.

The last significant improvement in the blast furnace process has already taken place today. Its essence is the replacement of part of the coke with cheap natural gas.

What is Bulat

Both damask steel and Damascus steel do not differ in chemical composition from ordinary unalloyed steel. It's iron with carbon. But unlike ordinary carbon steel, damask steel has a very high hardness and elasticity, as well as the ability to give a blade of exceptional sharpness.

The secret of damask steel haunted the metallurgists of many centuries and countries. What only methods and recipes were not offered! Precious stones, ivory were added to iron. The most ingenious (and sometimes the most terrible) "technologies" were invented. One of the oldest tips: for hardening, immerse the blade not in water, but in the body of a muscular slave - so that his strength turns into steel.

In the first half of the last century, the remarkable Russian metallurgist P.P. Anosov managed to reveal the secret of damask steel. He took the purest flash iron and placed it in an open crucible in a charcoal furnace. Iron, melting, was saturated with carbon, covered with slag from crystalline dolomite, sometimes with the addition of pure iron scale. Under this slag, it was very intensively freed from oxygen, sulfur, phosphorus and silicon. But that was only half the battle. It was also necessary to cool the steel as calmly and slowly as possible, so that during the crystallization process, large crystals of a branched structure, the so-called dendrites, could first form. Cooling went right in the hearth, filled with hot coal. This was followed by skillful forging, which should not have disturbed the resulting structure. Another Russian metallurgist, D.K. Chernov, subsequently explained the origin of the unique properties of damask steel, linking them with the structure. Dendrites consist of refractoriness but relatively soft steel, and the space between their "branches" is filled in the process of solidification of the metal with more carbon-saturated, and therefore harder steel. Hence the greater hardness and greater viscosity at the same time. During forging, this steel "hybrid" is not destroyed, its tree structure is preserved, but only from a straight line it turns into a zigzag one. The features of the drawing largely depend on the strength and direction of the blows, on the skill of the blacksmith.

Damascus steel of antiquity is the same damask steel, but later it was called the steel obtained by forge welding from numerous steel wires or strips. The wires were made from steels with different carbon contents, hence the same properties as damask steel. In the Middle Ages, the art of making such steel reached its greatest development. A Japanese blade is known, in the structure of which about 4 million microscopically thin steel threads were found. Naturally, the process of making weapons from Damascus steel is even more laborious than the process of making damask sabers.

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Many millennia ago, the peoples inhabiting different parts of our planet, almost at the same time, became acquainted with native metals. Acquaintance with iron belongs to a later period. Some nations learned to receive it earlier, and some much later. The fact is that native iron is almost never found in nature. It is assumed that the first iron that fell into human hands was of meteoric origin. The first mention of iron occurs about 5 thousand years ago, when it was valued more than native gold, which served as a setting for iron products.

According to historical facts, the tribes living on the territory of modern Armenia were already able to obtain iron at the beginning of the third millennium BC. In Egypt and Ancient Greece, iron was obtained in the second, and in China - in the middle of the 1st millennium BC. e. The small reserves of these states of such native metals as copper and tin served as an impetus for the search for new metals. And in America, rich in the largest deposits of copper, iron began to be mined only with the arrival of Europeans on the continent. African tribes, on the contrary, immediately stepped into the Iron Age, bypassing the Copper Age.

True, the process of extracting iron was much more complicated than copper. The ancient masters had no way to obtain such a high temperature at which iron began to melt. It was only in the first millennium BC that the raw iron reduction method appeared and it was widely used in the manufacture of weapons, tools and various tools, since it was the strongest metal known at that time. Initially, metallic iron was mined from iron ores by heating them with coal in well-ventilated places. Initially, such iron was spongy, brittle and contained a lot of slag. It was noted that metallic iron can be obtained without bringing it to the melting point, only there should be more fuel and it should be of better quality than when smelting copper, but it should be very “hot”. All this required additional melting conditions and a special furnace design.

An important step towards the production of iron was the invention of the forge, which was lined inside with refractory materials, and was open from above. Thanks to this method, iron turned out to be of better quality. Further processing of the metal took place in the forge, where the metal heated in the furnace was treated with hammer blows to get rid of slag, after which iron of satisfactory quality was obtained. Forging for many centuries has become the main type of metal processing, and blacksmithing - an important industry.

It was difficult to use iron in its pure form because of its softness; an alloy of iron with carbon gained practical importance. If iron contained up to 1.7% carbon, steel was obtained, and iron acquired the ability to be hardened. At first, the tool was heated red-hot, and then dipped into water, after which it became very hard with excellent cutting qualities. Very soon, iron, as one of the most accessible and cheap materials, penetrated into all spheres of human activity and made a huge revolution in the history of human development.

Iron alloys

It is more or less well known that the material commonly called iron, even in the simplest case, is an alloy of iron itself, as a chemical element, with carbon. At a carbon concentration of less than 0.3%, a soft ductile refractory metal is obtained, behind which the name of its main ingredient, iron, is assigned. An idea of ​​the iron that our ancestors dealt with can now be obtained by examining the mechanical properties of the nail.

At a carbon concentration greater than 0.3% but less than 2.14%, the alloy is called steel. In its original form, steel resembles iron in its properties, but, unlike it, it can be hardened - with sudden cooling, steel acquires greater hardness - a remarkable advantage, however, almost completely negated by brittleness acquired during the same hardening.

Finally, at a carbon concentration above 2.14%, we get cast iron. Brittle, fusible, well suited for casting, but not amenable to forging, metal.

The first step in the emerging ferrous metallurgy was to obtain iron by reducing it from oxide. The ore was mixed with charcoal and put into the furnace. At the high temperature created by burning coal, carbon began to combine not only with atmospheric oxygen, but also with that which was associated with iron atoms.

After the burning of coal in the furnace, the so-called kritz remained - a lump of substance with an admixture of reduced iron. The kritsa was then reheated and subjected to forging, knocking iron out of the slag. For a long time in iron metallurgy, it was forging that was the main element of the technological process, and, moreover, it was the last thing associated with shaping the product. The material itself was forged.

Steel was made from finished iron by carburizing the latter. At high temperatures and lack of oxygen, carbon, not having time to oxidize, impregnated iron. The more carbon there was, the harder the steel was after hardening.

As you can see, none of the alloys listed above has such a property as elasticity. An iron alloy can acquire this quality only if a clear crystalline structure appears in it, which occurs, for example, in the process of solidification from the melt. The problem of the ancient metallurgists was that they could not melt iron. To do this, you need to heat it up to 1540 degrees, while the technologies of antiquity made it possible to reach temperatures of 1000-1300 degrees. Until the middle of the 19th century, it was considered possible to melt only cast iron to a liquid state, since the fusibility of iron alloys increases with increasing carbon concentration.

Thus, neither iron nor steel by themselves were suitable for making weapons. Tools and tools made of pure iron were too soft, and those made of pure steel were too brittle. Therefore, in order to make, for example, a sword, it was necessary to make a sandwich from two iron plates, between which a steel plate was laid. When sharpening, soft iron was ground and a steel cutting edge appeared.

Such weapons, welded from several layers with different mechanical properties, were called welded. The common disadvantages of this technology were the excessive massiveness and insufficient strength of the products. The welded sword could not spring, as a result of which it inevitably broke or bent when it hit an insurmountable obstacle.

The lack of elasticity did not exhaust the shortcomings of welded weapons. In addition to the shortcomings mentioned, it, for example, could not be properly sharpened. Iron could be given any sharpness (although it was grinded at a terrible speed), but the soft cutting edge of iron was dulled almost instantly. Steel did not want to sharpen - the cutting edge crumbled. There is a complete analogy with pencils here - it is easy to make a soft lead very sharp, but it will become dull immediately, and you won’t bring it to a special sharpness - it will break ten times. So, razors had to be made of iron and re-sharpened daily.

In general, welded weapons did not exceed the sharpness of a table knife. This circumstance alone required to make it massive enough to give satisfactory cutting properties.

The only measure that allowed to achieve a combination of sharpness and hardness within the framework of welding technology was the hardening of the product after its sharpening. This method became applicable if the steel cutting edge was welded simply to an iron butt, and was not enclosed in a “sandwich” of iron. Or, blades could be hardened after sharpening, in which the iron core was bound on the outside with steel.

The disadvantage of this method was that sharpening was possible only once. When a steel blade became serrated and blunted, the entire blade had to be reforged.

Nevertheless, it was the development of welding technology - despite all its shortcomings - that made a real revolution in all spheres of human activity and led to a huge increase in productive forces. Welded guns were quite functional and, moreover, publicly available. It was only with their spread that stone tools were finally supplanted, and the age of metal began.

Iron tools decisively expanded the practical possibilities of man. It became possible, for example, to build houses cut from logs - after all, an iron ax felled a tree not three times like a copper one, but 10 times faster than a stone one. Hewn stone construction also became widespread. Naturally, it was also used in the Bronze Age, but the large consumption of a relatively soft and expensive metal strongly limited such experiments. The possibilities of farmers have also expanded significantly.

For the first time, the peoples of Anatolia learned to process iron. The ancient Greek tradition considered the people of Khalibs to be the discoverer of iron, for whom the stable expression "father of iron" was used in literature, and the name of the people itself comes from the Greek word Χάλυβας ("iron").

The Iron Revolution began at the turn of the 1st millennium BC. e. in Assyria. From the 8th century BC e welded iron quickly began to spread in Europe, in the III century BC. e. displaced bronze in China and Gaul, appeared in Germany in the 2nd century AD, and in the 6th century AD it was already widely used in Scandinavia and among the tribes living on the territory of the future Russia. In Japan, the Iron Age came only in the 8th century AD.

Metallurgists were able to see liquid iron only in the 19th century, however, even at the dawn of iron metallurgy - at the beginning of the 1st millennium BC - Indian craftsmen managed to solve the problem of obtaining elastic steel without melting iron. Such steel was called bulat, but due to the complexity of manufacturing and the lack of necessary materials in most of the world, this steel remained an Indian secret for a long time.

A more technological way to obtain elastic steel, which did not require either especially pure ore, or graphite, or special furnaces, was found in China in the 2nd century AD. Steel was reforged many times, with each forging folding the blank in half, resulting in an excellent weapon material called Damascus, from which, in particular, the famous Japanese katanas were made.

First of all, it must be said that until the 18th century, inclusive, coal was practically not used in metallurgy - due to the high content of impurities harmful to the quality of the product, primarily sulfur. From the 11th century in China and from 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 .

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.

Metal processing

The very first form of organizing the production of iron products were amateur blacksmiths. Ordinary peasants, who, in their free time from cultivating the land, traded in such a craft. The blacksmith of this sort himself found "ore" (a rusty swamp or red sand), burned coal himself, smelted iron himself, forged it himself, processed it himself.

The skill of the master at this stage was naturally limited to forging products of the simplest form. His tools consisted of bellows, a stone hammer and anvil, and a grindstone. Iron tools were made with the help of stone ones.

If there were ore deposits suitable for mining nearby, then the whole village could be engaged in the production of iron, but this was possible only if there was a stable opportunity for profitable marketing of products, which practically could not be in barbarian conditions.

If, for example, for a tribe of 1000 people there were a dozen iron producers, each of whom would build a couple of cheese furnaces in a year, then their labors ensured the concentration of iron products of only about 200 grams per capita. And not in a year, but in general.

This figure, of course, is very approximate, but the fact is that, by producing iron in this way, it has never been possible to fully cover all the needs for the simplest weapons and the most necessary tools at its expense. Axes continued to be made from stone, nails and plows from wood. Metal armor remained inaccessible even to the leaders.

The most primitive tribes of the Britons, Germans and Slavs at the beginning of our era had this level of opportunity. The Balts and Finns fought off the crusaders with stone and bone weapons - and this already turned out to be the XII-XIII centuries. All these peoples, of course, already knew how to make iron, but they could not yet obtain it in the required quantity.

The next stage in the development of ferrous metallurgy was professional blacksmiths, who still smelted metal themselves, but other men were more often sent to extract iron sand and burn coal - in exchange in kind. At this stage, the blacksmith usually already had a hammer assistant and a forge somehow equipped.

With the advent of blacksmiths, the concentration of iron products increased four to five times. Now every peasant household could be provided with a personal knife and axe. The quality of products also increased. Blacksmiths were professionals, as a rule, they knew the technique of welding and could draw wire. In principle, such a craftsman could also get Damascus if he knew how, but the production of Damascus weapons required such an amount of iron that it could not yet be mass-produced.

Iron is a chemical element with atomic number 26 in the periodic system, denoted by the symbol Fe (lat. Ferrum), one of the most common metals in the earth's crust. The simple substance iron is a silvery-white, malleable metal with a high chemical reactivity: iron quickly corrodes at high temperatures or high humidity in air. Iron is rarely found in nature in its pure form. Often used by man to create alloys with other metals and with carbon, it is the main component of steel. The prevalence of iron in the earth's crust (4.65%, 4th place after O, Si, Al) and the combination of specific properties make it the "No. 1 metal" in importance for humans. It is also believed that iron makes up most of the earth's core.

There are several versions of the origin of the Slavic word "iron" (Belarusian zhalez, Bulgarian zhelyazo, Ukrainian zalizo, Polish Żelazo, Slovenian Železo). One of the versions connects this word with the Sanskrit "pity", which means "metal, ore". Another version sees in the word the Slavic root "lez", the same as in the word "blade" (since iron was mainly used to make weapons). There is also a connection between the word "jelly" and the gelatinous consistency of "marsh ore", from which the metal was mined for some time. The name of natural iron carbonate (siderite) comes from lat. sidereus - stellar; indeed, the first iron that fell into the hands of people was of meteoric origin. Perhaps this coincidence is not accidental. In particular, the ancient Greek word sideros for iron and the Latin sidus meaning "star" are likely to have a common origin.

In terms of prevalence in the lithosphere, iron is in 4th place among all elements and in 2nd place after aluminum among metals. Its percentage by mass in the earth's crust is 4.65%. Iron is a part of more than 300 minerals, but only ores with a content of at least 16% iron are of industrial importance: magnetite (magnetic iron ore) - Fe3O4 (72.4% Fe), hematite (iron sheen or red iron ore) - Fe2O3 ( 70% Fe), brown iron ore (goethite, limonite, etc.) with an iron content of up to 66.1% Fe, but more often 30-55%.

Iron has long been widely used in technology, not so much because of its wide distribution in nature, but because of its properties: it is plastic, easily amenable to hot and cold forging, stamping and drawing. However, pure iron has low strength and chemical resistance (it oxidizes in air in the presence of moisture, becoming covered with insoluble brown loose rust). Because of this, in its pure form, iron is practically not used. What we used to call "iron" and "iron" products in everyday life is actually made of cast iron and steel - iron-carbon alloys, sometimes with the addition of other so-called alloying elements that give these alloys special properties.

There was a time when iron on earth was valued much more than gold. 1: 160: 1280: 6400. This is the ratio of the values ​​of copper, silver, gold and iron among the ancient Hittites. As Homer testifies in the Odyssey, the winner of the games arranged by Achilles was rewarded with a piece of gold and a piece of iron.
Iron was equally necessary for both the warrior and the plowman, and practical need, as you know, is the best engine of production and technical progress. The term "Iron Age" was introduced into science in the middle of the 19th century. Danish archaeologist K.Yu. Thomsen. "Official" boundaries of this period of human history: from IX...VII centuries. BC. when iron metallurgy began to develop among many peoples and tribes of Europe and Asia, and until the time when a class society and state arose among these tribes. But if the epochs are named according to the main material of the tools, then, obviously, the Iron Age continues today.

How did our distant ancestors get iron? First, the so-called cheese-making method. Cheese kilns were arranged right on the ground, usually on the slopes of ravines and ditches. They looked like pipes. This pipe was filled with charcoal and iron ore. Coal was lit, and the wind blowing into the slope of the ravine kept the coal burning. Iron ore was reduced, and a soft cry was obtained - iron with slag inclusions. Such iron was called welding; it contained some carbon and impurities transferred from the ore. Critsu was forged. Pieces of slag fell off, and iron remained under the hammer, pierced by slag threads. Various tools were forged from it. The age of wrought iron was long, but people of antiquity and the early Middle Ages were also familiar with other iron. The famous Damascus steel (or damask steel) was made in the East in the time of Aristotle (4th century BC). But the technology of its production, as well as the process of making damask blades, was kept secret.

Both damask steel and Damascus steel do not differ in chemical composition from ordinary unalloyed steel. These are alloys of iron and carbon. But unlike ordinary carbon steel, damask steel has a very high hardness and elasticity, as well as the ability to give a blade of exceptional sharpness.
The secret of damask steel haunted the metallurgists of many centuries and countries. What only methods and recipes were not offered! Gold, silver, precious stones, ivory were added to iron. The most ingenious (and sometimes the most terrible) "technologies" were invented. One of the oldest tips: for hardening, immerse the blade not in water, but in the body of a muscular slave, so that his strength turns into steel.

In the first half of the last century, the remarkable Russian metallurgist P.P. managed to reveal the secret of damask steel. Anosov. He took the purest flash iron and placed it in an open crucible in a charcoal furnace. Iron, melting, was saturated with carbon, covered with slag from crystalline dolomite, sometimes with the addition of pure iron scale. Under this slag, it was very intensively freed from oxygen, sulfur, phosphorus and silicon. But that was only half the battle. It was also necessary to cool the steel as calmly and slowly as possible, so that during the crystallization process, large crystals of a branched structure, the so-called dendrites, could first form. Cooling went right in the hearth, filled with hot coal. This was followed by skillful forging, which was not supposed to break the resulting structure.

Another Russian metallurgist - D.K. Chernov subsequently explained the origin of the unique properties of bulat, linking them to the structure. Dendrites consist of refractory, but relatively soft steel, and the space between their "branches" is filled in the process of solidification of the metal with more carbon-saturated, and therefore harder steel. Hence the greater hardness and greater viscosity at the same time. During forging, this steel "hybrid" is not destroyed, its tree structure is preserved, but only from a straight line it turns into a zigzag one. The features of the drawing largely depend on the strength and direction of the blows, on the skill of the blacksmith.

Damascus steel of antiquity is the same damask steel, but later the so-called steel obtained by forge welding from numerous steel wires or strips. The wires were made from steels with different carbon contents, hence the same properties as damask steel. In the Middle Ages, the art of making such steel reached its greatest development. A Japanese blade is known, in the structure of which about 4 million microscopically thin steel threads were found. Naturally, the process of making weapons from Damascus steel is even more laborious than the process of making damask sabers.

The cheese-making process largely depended on the weather: it was necessary that the wind must blow into the “pipe”. The desire to get rid of the vagaries of the weather led to the creation of bellows, which fanned the fire in a raw furnace. With the advent of bellows, there was no longer any need to build raw furnaces on the slopes. A new type of furnace appeared - the so-called wolf pits, which were dug in the ground, and blast furnaces, which towered above the ground. They were made from stones held together with clay. A tube of bellows was inserted into the hole at the base of the domnitsa and the furnace began to be inflated. Coal burned out, and in the hearth of the furnace there was already a cry familiar to us. Usually, in order to pull it out, they broke out several stones at the bottom of the furnace. Then they were laid back in place, the furnace was filled with coal and ore, and everything started all over again.

When removing the cracker from the furnace, molten cast iron was also poured out - iron containing more than 2% carbon, melting at lower temperatures. In solid form, cast iron cannot be forged; it shatters into pieces from one blow with a hammer. Therefore, cast iron, like slag, was initially considered a waste product. The British even called it "pig iron" - pig iron. Only later did metallurgists realize that liquid iron could be poured into molds and various products, such as cannonballs, could be obtained from it. By the XIV ... XV centuries. blast furnaces, which produced pig iron, firmly entered the industry. Their height reached 3 m more, they smelted foundry iron, from which not only the cores, but also the cannons themselves were poured. The real turn from the blast furnace to the blast furnace took place only in the 80s of the 18th century, when one of Demidov's clerks came up with the idea of ​​blowing into the blast furnace not through one nozzle, but through two, placing them on both sides of the hearth. The number of nozzles, or lances (as they are now called), grew, the blast became more and more uniform, the diameter of the hearth increased, and the productivity of the furnaces increased.

Two more discoveries greatly influenced the development of blast-furnace production. For many years blast furnaces were fueled by charcoal. There was a whole industry dedicated to burning coal from wood. As a result, the forests in England were cut down to such an extent that a special decree was issued by the Queen forbidding the destruction of the forest for the needs of the iron and steel industry. After that, English metallurgy began to decline rapidly. Britain was forced to import pig iron from abroad, mainly from Russia. This continued until the middle of the 18th century, when Abraham Derby found a way to obtain coke from coal, the reserves of which in England are very large. Coke became the main fuel for blast furnaces. In 1829, J. Nilson at the Kleid plant (Scotland) first applied heated air blowing into blast furnaces. This innovation increased the productivity of furnaces and dramatically reduced fuel consumption. The last significant improvement in the blast furnace process has already taken place today. Its essence is the replacement of part of the coke with cheap natural gas.

The process of steel production is essentially reduced to burning out impurities from cast iron, to oxidizing them with atmospheric oxygen. What metallurgists are doing may seem nonsense to an ordinary chemist: first they reduce iron oxide, simultaneously saturating the metal with carbon, silicon, manganese (iron production), and then they try to burn them out. The most annoying thing is that the chemist is absolutely right: metallurgists use an obviously ridiculous method. But they didn't have anything else. The main metallurgical redistribution - the production of steel from cast iron - arose in the 14th century. Steel was then obtained in bloomery forges. Cast iron was placed on a bed of charcoal above the air lance. During the combustion of coal, the cast iron melted and dripped down in drops, passing through a zone richer in oxygen - past the tuyere. Here, iron was partially freed from carbon and almost completely from silicon and manganese. Then it ended up at the bottom of the hearth, covered with a layer of ferruginous slag left over from the previous smelting. The slag gradually oxidized the carbon that was still in the metal, causing the melting point of the metal to rise and it to thicken. The resulting soft ingot was lifted up with a crowbar. In the zone above the tuyere, it was remelted again, while some part of the carbon contained in the iron was oxidized. When, after remelting, a 50 ... 100-kilogram cry was formed at the bottom of the furnace, it was removed from the furnace and immediately sent for forging, the purpose of which was not only to compact the metal, but also to give out liquid slags from it.

The most advanced iron-making unit of the past was the puddling oven, invented by the Englishman Henry Cort at the end of the 18th century. (By the way, he also invented the rolling of shaped iron on rolls with gauges cut into them. A red-hot strip of metal, passing through the gauges, took their shape.). Kort's puddling oven was loaded with cast iron, and its bottom (bottom) and walls were lined with iron ore. They were renewed after each melting. Hot gases from the furnace melted the iron, and then the oxygen in the air and the oxygen contained in the ore oxidized the impurities. The puddler standing by the stove was stirring the bath with an iron stick, on which crystals formed, forming an iron spit, were deposited. After the invention of the puddling furnace, nothing new appeared in this area of ​​ferrous metallurgy for a long time, except for the crucible method for producing high-quality steel developed by the Englishman Gunstman. But the crucibles were inefficient, and the development of industry and transport required more and more steel.

Henry Bessemer in 1856 patented a method for producing steel by blowing air through liquid iron in a converter - a pear-shaped vessel made of sheet iron, lined with quartz refractory from the inside. A refractory bottom with many holes serves to supply the blast. The converter has a device for rotation within 300°. Before starting work, the converter is placed “on its back”, cast iron is poured into it, blast is blown, and only then the converter is placed vertically. Air oxygen oxidizes iron to FeO. The latter dissolves in cast iron and oxidizes carbon, silicon, manganese ... Slags are formed from oxides of iron, manganese and silicon. The taxi process is carried out until the carbon is completely burnt out. Then the converter is again placed "on its back", the blast is turned off, the calculated amount of ferromanganese is introduced into the metal - for deoxidation. This results in high quality steel.
The method of converting pig iron became the first method of mass production of cast steel.

The redistribution in the Bessemer converter, as it turned out later, also had disadvantages. In particular, harmful impurities - sulfur and phosphorus - were removed from cast iron. Therefore, for processing in the converter, mainly cast iron free of sulfur and phosphorus was used. They later learned to get rid of sulfur (partially, of course), by adding manganese-rich "mirror" cast iron to liquid steel, and later ferromanganese. With phosphorus, which was not removed in the blast-furnace process and was not bound by manganese, the situation was more complicated. Some ores, such as Lorraine, which are rich in phosphorus, remained unsuitable for steel production. The solution was found by the English chemist S.D. Thomas, who proposed to bind phosphorus with lime. The Thomas converter, unlike the Bessemer one, was lined with burnt dolomite, not silica. Lime was added to cast iron during blowing. A lime-phosphorous slag was formed, which was easily separated from the steel. Subsequently, this slag was even used as a fertilizer.

The biggest revolution in steelmaking took place in 1865, when father and son Pierre and Emile Martin used a regenerative gas furnace built according to the drawings of W. Siemens to produce steel. In it, thanks to the heating of gas and air, in special chambers with a refractory nozzle, such a high temperature was reached that the steel in the furnace bath no longer passed into a pasty, as in a puddling furnace, but into a liquid state. It could be poured into ladles and molds, made into ingots and rolled into rails, beams, building profiles, sheets... And all this on a huge scale! In addition, it became possible to use the huge quantities of scrap iron accumulated over many years in metallurgical and machine-building plants. The latter circumstance played a very important role in the development of the new process. At the beginning of the XX century. open-hearth furnaces almost completely replaced the Bessemer and Thomas converters, which, although they consumed scrap, were in very small quantities.

Converter production could become a historical rarity, the same as puddling, if not for oxygen blasting. The idea of ​​removing nitrogen from the air, which is not involved in the process, and blowing pig iron with oxygen alone, occurred to many prominent metallurgists of the past; especially in the 19th century. Russian metallurgist D.K. Chernov and the Swede R. Åkerman wrote about it. But at that time oxygen was too expensive. Only in the 30s-40s of the 20th century, when cheap industrial methods for obtaining oxygen from air were introduced, metallurgists were able to use oxygen in steelmaking. Of course, in open-hearth furnaces. Attempts to blow oxygen through the pig iron in the converters were not successful; such a high temperature developed that the bottoms of the apparatus burned through. In the open-hearth furnace, everything was simpler: oxygen was given both to the torch to increase the temperature of the flame, and to the bath (into liquid metal) to burn out impurities. This made it possible to greatly increase the productivity of open-hearth furnaces, but at the same time raised the temperature in them so much that refractories began to melt. Therefore, here too, oxygen was used in moderate amounts.

In 1952, in the Austrian city of Linz, the Fest plant for the first time began to use a new method of steel production - an oxygen-converter. Cast iron was poured into the converter, the bottom of which did not have holes for blowing, it was deaf. Oxygen was supplied to the surface of liquid iron. The burnout of impurities created such a high temperature that the liquid metal had to be cooled by adding iron ore and scrap to the converter. And in fairly large quantities. Converters reappeared in metallurgical plants. The new method of steel production began to spread rapidly in all industrialized countries. Now it is considered one of the most promising in steelmaking. The advantages of the converter are that it takes up less space than an open-hearth furnace, its construction is much cheaper, and its productivity is higher. However, at first, only low-carbon mild steels were smelted in converters. In subsequent years, a process was developed for smelting high-carbon and alloy steels in a converter.

The properties of steels are varied. There are steels designed for a long stay in sea water, steels that can withstand high temperatures and the aggressive action of hot gases, steels from which soft tie wires are made, and steels for making elastic and hard springs. Such a variety of properties results from the variety of steel compositions. So, high-strength ball bearings are made from steel containing 1% carbon and 1.5% chromium; steel containing 18% chromium and 8 ... 9% nickel is the well-known "stainless steel", and turning tools are made from steel containing 18% tungsten, 4% chromium and 1% vanadium. This variety of steel compositions makes them very difficult to smelt. 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. It is known from physics 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.

Steels, especially high-quality ones, turned out to be very sensitive to the content of impurities. Even small amounts of oxygen, nitrogen, hydrogen, sulfur, phosphorus greatly impair their properties - strength, toughness, corrosion resistance. These impurities form non-metallic compounds with iron and other elements contained in the steel, which wedged between the grains of the metal, impair its uniformity and reduce quality. So, with an increased content of oxygen and nitrogen in steels, their strength decreases, hydrogen causes the appearance of flakes - microcracks in the metal, which lead to unexpected destruction of steel parts under load, phosphorus increases the brittleness of steel in the cold, sulfur causes red brittleness - the destruction of steel under load at high temperatures. Metallurgists have been looking for ways to remove these impurities for a long time. After smelting in open-hearth furnaces, converters and electric furnaces, the metal is deoxidized - aluminum, ferrosilicon (an alloy of iron with silicon) or ferromanganese are added to it. These elements actively combine with oxygen, float into the slag and reduce the oxygen content in the steel. But oxygen still remains in the steel, and for high-quality steels, its remaining quantities are too large. It was necessary to find other, more effective ways.

In the 1950s, metallurgists began to evacuate steel on an industrial scale. A ladle with liquid metal is placed in a chamber from which air is pumped out. The metal begins to boil violently and gases are released from it. However, imagine a ladle with 300 tons of steel - how long will it take until it boils completely, and how much will the metal cool during this time. It will immediately become clear to you that this method is suitable only for small amounts of steel. Therefore, other, faster and more efficient vacuuming methods have been developed. Now they are used in all developed countries, and this has improved the quality of steel. In the early 60s, a method of electroslag remelting of steel was developed, which very soon began to be used in many countries. This method is very simple. In a water-cooled metal vessel - a mold - an ingot of metal is placed, which must be purified, and covered with slag of a special composition. Then the ingot is connected to a current source. An electric arc occurs at the end of the ingot, and the metal begins to melt. Liquid steel reacts with slag and is purified not only from oxides, but also from nitrides, phosphides and sulfides. A new ingot, purified from harmful impurities, solidifies in the mold. An alternative method was also used: slags of a special composition for cleaning metal are melted and poured into a ladle, and then metal is released from the furnace into this liquid slag. The slag mixes with the metal and absorbs impurities. This method is fast, efficient and does not require large amounts of electricity.

Obtaining iron directly from the ore, bypassing the blast-furnace process, was engaged in the last century. Then this process was called direct reduction. However, until recently, it has not found wide distribution. Firstly, all proposed methods of direct reduction were inefficient, and secondly, the resulting product - sponge iron - was of poor quality and contaminated with impurities. And yet enthusiasts continued to work in this direction. The situation has changed radically since the widespread use of natural gas in industry. It proved to be an ideal means of recovering iron ore. The main component of natural gas, methane CH4, is decomposed by oxidation in the presence of a catalyst in special devices - reformers according to the reaction 2CH4 + O2 → 2CO + 2H2.

It turns out a mixture of reducing gases - carbon monoxide and hydrogen. This mixture enters the reactor, which is fed with iron ore.
The shapes and designs of reactors are very diverse. Sometimes the reactor is a rotating tube kiln, such as a cement kiln, sometimes a shaft kiln, sometimes a closed retort. This explains the variety of names for direct reduction methods: Midrex, Purofer, Ohalata-i-Lamina, SL-RN, etc. The number of ways has already exceeded two dozen. But their essence is usually the same. Rich iron ore is reduced by a mixture of carbon monoxide and hydrogen. From sponge iron, not only a good ax - a good nail cannot be forged. No matter how rich the original ore is, pure iron will still not come out of it. According to the laws of chemical thermodynamics, it will not even be possible to restore all the iron contained in the ore; some of it will still remain in the product in the form of oxides. Sponge iron turns out to be an almost ideal raw material for electrometallurgy. It contains few harmful impurities and melts well. The benefit of the direct reduction scheme - the electric furnace is its low cost. Direct reduction plants are much cheaper and use less energy than blast furnaces. Direct remelting is not the only way to use sponge iron in ferrous metallurgy. It can also be used as a substitute for scrap metal in open hearth furnaces, converters and electric arc furnaces.

The Iron Age continues. Approximately 9/10 of all metals and alloys used by mankind are iron-based alloys. Iron is smelted in the world about 50 times more than aluminum, not to mention other metals. Plastics? But in our time, they most often play an independent role in various designs, and if, in accordance with tradition, they are trying to introduce them into the rank of “irreplaceable substitutes”, then more often they replace non-ferrous metals, not ferrous ones. Only a few percent of the plastics we consume are replacing steel. Iron-based alloys are universal, technologically advanced, available and cheap in bulk. The raw material base of this metal also does not cause concern: already explored reserves of iron ore would be enough for at least two centuries to come. Iron has long to be the foundation of civilization.