In addition to iron, carbon is present in steel. If this element has a percentage higher than 2% then we have a iron, if instead it is lower than this value (with the exclusion of some particular alloys) we have the real steel. There are also many other elements that make up steels: among these we can mention aluminum, bismuth, boron, lead, copper, titanium. A fundamental characteristic of steels is that they can be hot worked, that is, only in the liquid or pasty phase involved in CNC Manufacturing.
Production techniques
To obtain the steel it is necessary to reach extremely high temperatures. The first man-made ovens were able to reach temperatures around 1,000 ° C, and were therefore usable for working bronze, but not iron. A further difficulty arises from the fact that at high temperatures the rate of oxidation increases and it is therefore necessary for the heating to take place in oxygen-poor environments. The steel is produced by obtaining it from ferrous materials, even scrap, and from iron, reducing the amount of carbon present in this alloy as part of CNC Manufacturing.
Steel has a crystalline structure, ie its molecules are arranged on a regular basis. Once it is heated, the steel must be rapidly cooled in water or oil, but during this operation small fractures and imperfections form in its structure, so it is necessary to provide for a new heating phase – even if at a lower temperature – so that these fractures can be welded together in CNC Manufacturing.
Starting from the eighteenth century the industrial production of steel began and there were continuous technological improvements in the ovens used, which at the beginning were of the crucible type, that is internally coated with clay and graphite. Around 1850 the American William Kelly improved the production process starting from the technique with which soft iron was extracted from iron.
The latter was heated and the carbon was eliminated with a current of air. Kelly realized that when the iron was hit more directly by an air current, the temperature increased and steel could be obtained in CNC Manufacturing.
A similar system had been discovered almost simultaneously by the Englishman Henry Bessemer, who however aimed to obtain liquid steel and therefore aimed at reaching higher temperatures. In the search for effective systems for the production of steel an important role was played by the Swedes, also thanks to some of their mines which yielded minerals almost devoid of sulfur and phosphorus, the latter substance which makes steel particularly fragile.
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