Stainless steels are split into 5 families.

• Ferritic steels
  Iron – Chromium or Iron – Chromium – Molybdenum alloys. They contain no nickel.
  
  
• Martensitic steels
  usually contain 12 to 19 % chromium and their carbon content varies between 0.08 and 1.2 %. They may contain nickel and molybdenum as well as other elements such as copper, titanium or vanadium.
  
  
• Austenitic steels
  the best known and most widely used steels within the stainless steel family. They contain nickel (usually 7 % or more) and, sometimes, additions of molybdenum, titanium or niobium.
  
  
• Austeno-ferritic steels
  are  characterised by a high chromium content (22 % or more) and low nickel content (3.5 to 8 %).
  They are more commonly called "duplex steels".
  
  
• Heat-resisting steels
  are grades often used when resistance to temperatures between 900 and
  1150 °C is required (EN 10095 standard).