Steel

According to the classical definition, steel is an alloy of iron (Fe) and carbon (C) which contains less than 2.11% of carbon.
From the point of view of chemistry and thermodynamics, steel is in fact a metastable alloy of iron (Fe) and cementite - iron carbide Fe3C.

The incredible range and flexibility of the properties (with the help of alloying, heat treatment and plastic processing) as well as the relatively low cost of production make it still the most widely used metal material. Steel, for example, can be very soft and as such extremely suitable for deep drawing (making cans, cans, etc.). In contrast, steel can be very hard and brittle, as in martensitic steels used for blades.

The most important alloying element in steel is carbon. It is found in steel in the form of a compound called cementite, Fe3C. The increased mass fraction of carbon makes steel a stronger, but at the same time more brittle material.

The specific weight of steel is almost the same as the specific weight of pure iron and is about 7,850 kg / m2 .

Properties of steel such as hardness, ductility, tensile strength, etc. they can be created and controlled in a very wide range, which makes steel the basic metal construction material. The three basic methods, which - of course - can be combined with each other in order to achieve the desired properties of steel, are:

• alloying,
• heat treatment (annealing, quenching, improvement, etc.) i
• plastic processing (rolling, extraction, etc.).

Nehrđajući čelik ili korozijski postojani čelik je legura željeza i najmanje 12% kroma (moderni nehrđajući čelici sadrže i do 30% kroma). Pored kroma postojanost prema koroziji povećava se dodatkom nikla. Kombinacijom legiranja kromom i niklom razvijeni su čelici tipa 18/8 (18% Cr i 8% Ni) Prokrom (isto što i inoks) sinonimi su i trgovački nazivi za nehrđajući čelik, a odnose se uglavnom na relativno mekane nemagnetične, austenitne čelike koji sadrže nikal.