Iron

History and etymology

The name of iron comes from traditional Latin the ferrum : iron; object out of iron; sword; chains.

The first evidence of the use of iron goes back to approximately 4000 av. J. - C., at the Égyptiens and Sumériens. Some objects like points of lances, scraping-knives and ornaments were forged of iron coming from meteorites….

Properties

Physical properties

It is a Métal which, according to the temperature, presents in several forms allotropic S. In the Normal conditions of pressure and temperature, it is a solid Cristal flax of structure Cubique centered (iron α or ferrite); starting from 912 °C, it becomes Cubique with centered faces (iron γ or Austénite). Beyond: 1394 °C, it becomes again Cubique centered (iron δ).

Iron is ferromagnetic: the magnetic moments of the atoms are aligned under the influence of an external magnetic field and preserve their new orientation after the disappearance of this field.

Currents of convection rich in liquid iron in the external layer of the terrestrial core (external core) are supposed to be at the origin of the Terrestrial magnetic field.

Chemical properties

Left with the free Air in the presence of moisture, it corrodes by forming rust FeO. Rust being a porous material, the reaction of oxidation can be propagated to the heart of metal, contrary, for example, with the aluminum, which forms a fine layer of impermeable oxide.

In solution, it presents two principal valences:

Fe 2+ (iron ferrous ) which has a low green color;
Fe 3+ (ferric iron ) which has a color rusts characteristic. Fe 3+ can be reduced by metal copper, for example, reaction at the origin of the process of engraving of the printed circuits by iron perchloride, FeCl.

The Hémoglobine of the Sang, which allows the red globules to transport the Dioxygène, contains iron.

Layers

In nature, the exploitable iron Minerai S are primarily Oxyde S: in particular the Hematite FeO, the Magnetite FeO and the Limonite HFeO.

The magnetic oxide or magnetite FeO is known since Greek Antiquity. It draws its name from the mount Magnetos (the large mount), a Greek mountain particularly rich in this Minéral.

Metallurgy

Extraction

Iron is obtained industrially while reducing by the Carbon monoxide (CO) coming from carbon, the Oxyde S contained in the ore; this can be carried out:

Since the Age of iron and until the 19th century in certain area of the world: by reduction of the ore with Charcoal in a low hearth or low hearth: one obtains, without passing by a liquid phase, a heterogeneous steel and iron mass called " loupe" , " massiot" or " sponge fer". This metal gross weight is formed by more or less incorporating slags (mineral waste of the reduction) and porosities. In order to make metal clean to the development of objects, the " loupe" can be broken and sorted by type of percentage of carbon or more simply be directly compacted with the forging mill. This work, known as of purification, varies according to the areas and from the technical cultures. All in all, its principle consists in evacuating slag and welding the various parts of the metal mass. One speaks about shingling for the stage consisting in hammering hot metal to evacuate slag and about welding to indicate the end of the operation of purification, consisting in carrying out several master keys with the forging mill while folding up and by welding metal onto itself.

It is with the development of the mills and of the hydraulic force, that the technical line of the blast furnace could develop and was essential overall on that of the low-furnace. The principal difference in this process is the reduction of iron oxides at a temperature superior at the melting point of iron. Metal is produced in liquid phase, forming the cast iron. In this case, mineral waste, called slags, is separated from metal.

It is by adding silica to the ore with calcareous gangue or limestone with the ore with siliceous gangue that one passed to the blast furnace: this flux allows the formation of slag, and makes it possible iron to absorb Carbone to make quite liquid cast iron, because its melting point is lower than iron. For a long time the blast furnaces functioned with the Charcoal. The harder coke made it possible to make blast furnaces much higher but producing a less pure cast iron.

To obtain a forgeable metal, the cast iron should be refined. This stage consists in decarbonizing the cast iron to obtain a weaker carbon alloy: iron or steel. There still, the techniques of development of metal out of blast furnace vary according to the areas, of the technical cultures and the products which one wants to obtain.

Currently: the iron oxides (ores) are reduced by carbon monoxide obtained by the reaction of coke and the air in a Haut-fourneau. cast iron liquid and liquid slag are obtained.

The cast iron is transformed into steel with the converter. In this tank, one blows of the oxygen on the cast iron to eliminate the Carbone from it.

Steel and cast iron

The Steel and the cast iron are iron alloys containing a small proportion of carbon in mass, but a proportion much more important of many atoms (55,845 ÷ 12 = 4,65 times more):

the cast iron contains of 11; % with 6,09 % of carbon;
steel contains 0,00025 % with 1,007 % of carbon;
below 0,00025 % of carbon, one speaks about industrial irons.

Various additions make it possible to obtain special steels:

Manganese to improve the wear resistance;
Tungsten for hardness at high temperature;
Silicon to improve the elasticity (used for the Spring S).

The stainless steels are alloys containing of strong proportions of Chrome. One can also add to it Nickel and sometimes Molybdène or Vanadium. For example, covers have an inscription “18/8” or “18/10”, that means that they contain 18 % of chromium and 8 or 10 % of nickel.

Other alloys

There exist other less known alloys:

Intermetallic S Fe-Al;
Fe-Cr-Al.

Use

Iron is largely used in the form of steel in the steel construction.

Metal iron and its oxides are used since decades to fix analogical or numerical information on suitable supports (magnetic bands, audio and video cassettes, Disquette S). The use of these materials from now on is however supplanted by compounds having better a Permittivité, for example in the hard drives.

Iron is also employed in the wire.

in the food

Iron is one of the Rock salt which one finds in the food.

Iron is essential with the transport of the Oxygène and the formation of the red Globules in the Sang. He plays also a part in the manufacture of news cell S, of Hormone S and of Neurotransmetteur S. the iron contained in the plants is less better absorbed by the organization than that contained in food of animal origin. However, the absorption of the iron of the plants is favoured if one consumes it with some Nutriment S, like the Vitamine C.

Symbolic system

iron symbolizes the Solidité (e.g.: the ground pot and the iron pot, the fable of Jean of the Fountain).
the Noces of iron symbolize the 41 years of Mariage in the French folklore.

See too

iron

External bond

File on iron: Iron falls the mask, file Futura-sciences

Be-X-old: Жалеза Simple: Iron Zh-min-nan: Fe (goân-sò͘) Zh-yue: 鐵

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