Steel is a deformable (ductile) iron alloy with carbon (2%) and other elements, which must contain at least 45% of the iron in alloy of iron with carbon and alloying elements (alloyed, high-alloy steel).
Among the physical properties of steel the most important are the true density, melting point, specific heat, thermal conductivity, coefficient of thermal expansion. Melting point is temperature at which steel turns from solid to liquid. The melting point of iron is 1535 ° C, but it changes with the introduction of of carbon and other elements in it. For example, iron with carbon content of 4.3% is melted
at about 1130 ° C. (Smith, 2006)
The mechanical properties of steels are characterized by a tensile strength, elongation, hardness and toughness. Hardness is the ability to resist indentation of more solid materials, like a diamond cone or steel ball. Impact strength is the property to resist the dynamic (shock) loads, and its value is determined by the amount of work required to fracture the specimen to the steel pendulum. (Smith, 2006)
Among the chemical properties of steel the most important is corrosion resistance, which characterizes the ability of steel to resist the destructive effect of the environment. Technological properties of steels show its ability to handle pressure, machining, casting, welding, etc. (Smith, 2006)
Steel production process goes in the Furnace from iron and metallic waste and scrap iron, containing iron oxides, which are a source of oxygen. Smelting is carried out at higher temperatures, possibly to accelerate melting of solid raw materials. In this case the iron is partially oxidized:
2Fe + O2 = 2FeO + Q. The resulting iron oxide (II) FeO oxidizes silicon, manganese, phosphorus and carbon that are in the iron:
Si +2 FeO = SiO2 + 2 Fe + Q
Mn + FeO = MnO + Fe + Q
2P + 5FeO = P2O5 + 5Fe + Q
C + FeO = CO + Fe ”“ Q (Bugayev et al., 2001)
In order to complete oxidation reactions in the melt, it is necessary to add the so-called deoxidizers -ferromanganese, ferrosilicon and aluminum. (Bugayev et al., 2001)
History
Steel has entered into human life relatively late, and the first partial application got the iron. The first iron bridge was built in 1779 on the Severn River in England, but this was special case, as the steel industry was underdeveloped, the possibility of iron use was very limited, and methods of elements alloying were not developed. But development of construction and machine building required new material, which could radically change the appearance of building and raise it to a new level. In 1780 was created a method of obtaining of welding steel, which at the beginning of the XIX century was placed on an industrial basis. In the late 18th century in England was born the idea of industrial production of profiled steel. Later steel production began un France (in 1845) and gradually the process was covered by state standards. By the 1819-1820 were released corners, T-and Z-shaped elements of varying lengths. (Hyde, 1977)
In modern metallurgy steel is smelt mainly of iron and steel scrap. The main types of units for its smelting are open-hearth furnace, basic oxygen furnace, electric furnace. The most progressive today is the oxygen-converter method of steel production. At the same now are being developed new and promising ways to produce steel: the direct recovery of steel from ore, electrolysis, ESR, etc.