The Definition of Stainless Steel
Stainless steel is a low carbon steel which contains chromium; it is this addition of chromium that gives plain steel its unique stain and corrosion resisting properties. The chromium in the steel allows the formation of a rough, invisible, corrosion resisting chromium oxide film on the steel surface. If the material is damaged either mechanically or chemically, the film heals itself (providing that oxygen is present). With the addition of chromium and other elements such as molybdenum, nickel and nitrogen, the steel takes on increased corrosion resistance and other properties.
The Classes of Stainless Steel
Stainless steels are generally grouped into 5 different classes. Each is identified by the alloying elements which affect their microstructure and for which each is named.
- Martensitic stainless steels
- Ferritic stainless steels
- Austenitic stainless steels
- Duplex (ferritic-austenitic) stainless steels
- Precipitation-Hardening (PH) stainless steels