When nickel (Ni) is added to stainless steel in sufficient quantities, the crystal structure changes from ferrite to austenite, hence the term austenitic stainless steels. The basic composition of austenitic stainless steels is 18% chromium (Cr) and 8% nickel (Ni). Austenitic grades are the most commonly used stainless steels accounting for more than 70% of production (304 is the most commonly specified grade by far).
Basic properties of austenitic stainless steels include:
- Excellent corrosion resistance
- Excellent cleanability and hygienic properties
- Fabricated and formed with ease
- Excellent weldability
- Hardened by cold work, not by heat treatment
- Usually used in the fully annealed condition in which they are essentially non-magnetic
- The ability to handle both extremely low (cryogenic) temperatures and, depending on the load and permissible distortion, higher service temperatures of around 600 degrees Celsius or even higher if scaling resistance is the principal consideration.
Common uses and applications cover an extremely wide scope such as hollowware, builders' hardware, architectural applications, abattoir, beer and beverage production and food processing equipment (which require cleanability and hygienic corrosion resistant properties).