Stainless Steel Family Tree
CLASSIFICATION OF STAINLESS STEEL
Stainless steel is classified below based on their chemical compositions and metallurgical structure,
the chemical compositions are classified as Fe-Cr Family, Fe-Cr-Ni Family, the metallurgical structures are classified as Austenite, Ferrite, Martensite, Duplex Family and Precipitation Hardening Stainless Steel Family.
Austenitic Stainless Steel
Their crystal structure is FCC (Face-Centered Cubic) and they can't be hardened by heat treatment and are strengthened by work-hardening. Type 304 (18Cr-8Ni) is a representative austenitic stainless steel.
Austenitic structure is stable from room temperature to high temperature and doesn't have transformation during rolling process.
These alloys are basically non-magnetic in the annealed condition, but may be slightly magnetic when cold machined or worked.
The austenitic types feature adaptability to cold forming, ease of welding, high-temperature service, and, in general, the highest corrosion resistance.
Ferritic Stainless Steel
Their structure is BCC (Body-Centered Cubic) and they can't be hardened significantly by heat treatment.
These alloys are magnetic in all conditions and intermediate in their ability to withstand corrosion.
Martensitic Stainless Steel
These alloys contain from 10% to 18% chromium and are magnetic in all conditions and can be hardened by heat treatment to high strength levels. Type 410 stainless steel is the basic alloy in this grouping.
The martensitic types are the lowest in their ability to withstand corrosion.
Martensitic varieties find major applications in products that must resist atmospheric oxidation, midly corrosive chemicals,
and wet or day corrosion environments.