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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Iron. History of invention and production
Directory / The history of technology, technology, objects around us Free native iron in the earth's crust, unlike copper, is almost never found. But it is part of many minerals and is much more widespread than non-ferrous metals. In ancient times, it could be mined literally everywhere - from lacustrine, swampy, meadow and other ores. However, compared to copper metallurgy, iron metallurgy is a rather complex process. Iron melts at 1539 degrees. Such a high temperature was completely inaccessible to the ancient masters. Therefore, iron entered the everyday life of man much later than copper. Its widespread use as a material for the manufacture of weapons and tools began only in the 1st millennium BC, when the raw iron recovery method became known (however, some peoples learned iron metallurgy much earlier; for example, the tribes that inhabited the territory of modern Armenia , knew how to get iron from ores already at the beginning of the 3rd millennium BC). The most common iron ores (magnetic iron ore, red iron ore and brown iron ore) are either a compound of iron and oxygen (iron oxide) or iron oxide hydrate. In order to isolate metallic iron from these compounds, it is necessary to reduce it - that is, to take away oxygen from it.
Of course, the ancient masters had no idea about the complex chemical processes that occurred during the reduction of iron. However, observing the "smelting" of the ore, they eventually established several important patterns, which formed the basis of the simplest methods of iron production. First of all, our ancestors noticed that in order to obtain iron, it is not at all necessary to bring it to a melting point. Metallic iron can also be obtained at much lower temperatures, but there must be more fuel than in the smelting of copper, and this fuel must be of better quality. It is also necessary that the fire be as "hot" as possible. All this required a special arrangement of the furnace and melting conditions.
As a rule, starting to "melt" iron, the craftsmen first dug a round hole, the walls of which were covered with a thick layer of clay from the inside. From the outside, an opening for air injection was brought to this pit. Then, over the rounded lower part, the upper one was built in the form of a cone. Charcoal was used as fuel. It was poured into the very bottom of the furnace - into the pit. On top of it, a charge was laid in layers - crushed ore and coal. A thick layer of coal was poured on the very top. After the fuel was ignited below, a strong heating of the ore began. In this case, there was a chemical reaction of carbon (coal) oxidation and iron reduction. In the form of tiny petals, doughy iron, which was three times heavier than slag, fell down and settled in the lower part of the furnace.
As a result, at the bottom of the pit, a lump of soft welded iron was collected - kritz, weighing from 1 to 8 kg. It consisted of soft metal with voids filled with hard slags. When the "melting" was over, the furnace was broken and the kritsa was taken out of it. Further processing took place in the forge, where the kritsa was again heated in a forge and worked with hammer blows to remove slag. In iron metallurgy, forging became the main type of metal processing for many centuries, and blacksmithing became the most important branch of production. Only after forging did iron acquire satisfactory qualities. Pure iron, however, cannot be used because of its softness. Only an alloy of iron and carbon was of economic importance. If the resulting metal contained from 0 to 3% carbon, steel was obtained, that is, iron, which acquired a new property - the ability to be hardened. To do this, the tool was heated red-hot and then cooled in water. After hardening, it became very hard and acquired excellent cutting qualities. With a natural influx of air, the temperature in the furnace did not rise above 1000 degrees. Already in antiquity, it was noticed that more iron and better quality can be obtained from the same ore if air is artificially pumped into the furnace with the help of bellows. Furs were made from skins, equipped with muzzles and set in motion by hand. With the help of nozzles and bellows, raw, unheated air was injected into the furnace, from where the name of the whole process came from. However, even with this method, the temperature could only rise to 1200 degrees, and no more than half of the iron contained in it was extracted from the ore. Being a widely available and cheap material, iron very soon penetrated all branches of production, everyday life and military affairs and made a revolution in all spheres of life. An iron ax and a plow with an iron plowshare made it possible to master agriculture for those peoples who had previously been completely inaccessible to it. Only after the spread of iron did agriculture become the most important branch of production among most peoples. Iron gave the craftsman tools of such hardness and sharpness that neither stone nor bronze could resist. They were the basis on which other crafts began to develop rapidly. These major shifts put an end to primitive society. It was replaced by a more developed - class society. Author: Ryzhov K.V.
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