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Steel designates all metallic alloys, whose main part is iron and which are plastic transformable by Schmieden or rollers.
According to the classical definition steel is an iron carbon alloy, which contains less than 2.06% (mass) carbon. Also the DIN EN 10020, after the steel of materials, follows this definition whose proportion at iron is larger than the every other element, its carbon content generally smaller than 2 Gew. - % C are.
With higher portions of carbon one speaks of cast irons, here is present carbon in the form of graphite.
At present there are however some groups of steel, in which carbon is no more alloying constituent. An example of it are IF-steel, in whose iron matrix no carbon is interstitially stored.
Steel is to most used metallic materials. By alloyage with carbon and other elements in combination with warm and its characteristics for a broad range of application can be adapted to thermalmechanical treatment (simultaneous of thermal treatment with plastic shaping).
The steel can be manufactured for example very softly and for it excellently ductile, as for instance the tinplate of cans. In contrast to this it can be manufactured very hard and but inflexibly, as for instance martensitic steel for measurer (cutlery steel). Modern developments aim at it to manufacture the steel at the same time firmly and duktil (ductile) as contribution for lightweight construction of machines.
The most important alloying element in the steel is carbon. It is present either elementarily or as connection (Zementit=Fe3C). The meaning of carbon in the steel results from its influence on the steel characteristics and phase conversions.
Generally steel with higher carbon portion becomes more firmly, in addition, more inflexibly. From alloyage with carbon different phases result as a function of the concentration and the ambient temperature: Austenite, ferrite, pearlite, Ledeburit and primary, secondary and tertiary cementite. By accelerated cooling of austenite, in carbon, can the further phases as fine (ex Sorbit) and feinststreifiger pearlite (ex Troostit) is solved as well as more nadeliger/granular Bainit ("intermediate stage") and more substantially/nadeliger martensite and/or Hardenit to develop (see also to hardnesses (steel)).
The phase composition of steel is described for the equilibrium with the iron carbide diagram.
The density of steel and/or iron amounts to approximately 7.85 10 kg/m the elastic module approx. 210 kN/mm
Steel knows intended characteristics (hardness, ductility, notched-bar impact-strength"Â…) assume. The three fundamental methods for the change of the steel characteristics are:
According to DIN EN 10020 becomes between the two main grades
differentiated. The Kurznamen of the steel are fixed in the DIN EN 10027. Today approx. 2500 different steel grades are manufactured.
The steel plant materials are divided according to the alloying elements, the structural constituents and the mechanical characteristics in groups.
As a function of the alloy content divided into:
Unalloyed steel is divided into steel plant materials, which are not intended for a thermal treatment, and into steel for a thermal treatment.
(The content of all alloying elements except carbon amounts to < 5%)
Low-alloy steel has similar in principle characteristics as unalloyed steel. Technically importantly their substantially better suitability is for the influence of the mechanical characteristics by thermal treatment and with special alloy combinations also the increased heat resistance.
(The content one of the alloying elements amounts to at least 5%)
Highly alloyed steel is necessary for special characteristics. or special physical characteristics can be produced only by highly alloyed steel
Further important characteristics for the user are the areas of application and ranges of application of the steel. Therefore also a marking is meaningful, out of which this can be taken:
see: Steelmaking
Although iron already found since the antique one, to the beginning of the Eisenzeit 1400 v. Christ use became the first well-known production of steel in Europe only 1742 by Benjamin Huntsmann accomplished. The traditional production of a Samuraischwerts in the Middle Ages in Japan was with the enormous difficulty connected that that carbon content during the treatment became ever smaller and under the carbon content of modern steel remained anyway clear.
The material steel and the increase of its production accompanied over approximately 130 years directly with the world-economical development into the present. In some economic sectors (e.g. Shipbuilding) represented the steel production the only growth border. The technical technisch-industrielle revolution of the second half 19. Century and caused themselves the enormous increase of the steel production mutually. That Paris Eiffelturm symbolizes this time period as enormous structural steelwork. The steel production of a national economy was regarded long time even as measure for its efficiency.
Before and after the Second World War the steel played the main role with the production of armaments, in particular from tanks. Of Germany Norway campaign because of the Swedish iron ore one undertook, and the allied ones wanted to inundate the Ruhr district, at that time the largest geographical weapon producer of Europe, by means of purposeful dam failures.
In the post-war period in Europe the Coal and Steel Community was created, in order to hold the steel production under control. From this connection the European union developed in several steps.
Although the earth's crust not covered to five per cent from iron, which most important raw material for steel, exists, at present the requirements of raw materials of the industry. Beginning in 2. Half-year 2003 shows up a dramatically changed raw material situation, which was caused particularly by the strongly rising steel need of the national economies in the People's Republic of China, India and Brazil. For some years alone the steel production grows in China annually by more than the present total production of Germany. Suddenly the production of the ore mines was not sufficient, which were handling capacities of the ore ports exhausted, and also not more enough ships for ore transport were available. Similar developments resulted for coke, which is needed for the pig iron production, and for scrap iron as secondary raw material for the steelmaking.
The consequences from this development were underestimated by the large steel manufacturers of the industrialized countries, so that the current requirements of raw materials cannot be covered. Consequently the prices for raw materials and steel products multiplied. At present steel is limited and expensive.
It is not a change of trend in view, the steel production and the requirements of raw materials will continue to rise, although the growth rate sinks by national interferences at present. The need of iron ore could be covered by opening new extraction areas.
Except the steel industry also concrete and aluminum are affected by this phenomenon. A cause for the high petroleum price is likewise the risen requirements of raw materials of the developing countries.
Steel stands in particular in the automobile industry in direct competition with materials with smaller specific weight, like aluminum, magnesium, plastics and GRP components materials. Since these materials are less firm however throughout than steel, the weight advantage can by purposeful using of high-strength steel and constructional measures (thinner sheet metal with recesses however for it Sicken) become balanced.
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