Stainless steel
Stainless steel types
- Martensitic steel
- Austenitic steel
- High temperature steel
Description
Stainless steel are alloys with an iron, chromium and carbon base, possibly containing other elements such as Ni – Mo – Si – etc., whose main characteristic is resistance to corrosion.
These steels are mainly used in the chemical, petrochemical, food and paper manufacturing industries, the pharmaceutical, biomedical and transport sectors, off-shore structures, household appliances, building and construction applications, street furniture, cutlery and the production of pans.
Properties
The main feature of this steel family is its resistance to wet corrosion, also known as electrochemical corrosion. Another important feature of stainless steels is their resistance to oxidation at high temperatures, which is why these steels are often used in environments with high temperatures, such as furnaces or ovens for heat treatments.
These properties depend on a phenomenon known as passivation, which consists in the formation of an invisible film of chromium oxide on the surface of stainless steels. This acts as a barrier, preventing oxidation from progressing, and avoiding the onset of corrosion.
The essential condition needed in order for this protective layer to form is a quantity of chromium of at least 10.5% and the carbon content must be less than or equal to 1.2%, as defined by the EN 10088-1 standard.
Stainless steel types
The families of stainless steels are divided according to their microstructure at room temperature:
- Austenitic stainless steels
- Ferritic stainless steels
- Martensitic stainless steels
- Austenitic-ferritic stainless steels, also known as Duplex steels
The only exceptions are precipitation hardening stainless steels, which include both martensitic, austenitic and semi-austenitic steels