Austenitic stainless steels are the most common stainless steels.
The austenitic group covers a wide range of steels with great variations in properties. Corrosion resistance is normally the most important of these.
The steels can be divided into the following sub-groups:
- Austenitic without molybdenum (e.g. 304 and 304L)
- Austenitic with molybdenum (e.g. 316, 316L, 317L and 904L)
- Stabilized austenitic (e.g. 321, 321H and 316Ti)
- Fully austenitic with high molybdenum and nitrogen (e.g. 254 SMO® and 1.4565)
- Heat and creep resistant (e.g. 321H, 253 MA® and 310S)
Austenitic stainless steels with and without molybdenum have an austenitic (γ) microstructure with, possibly, a low content of delta-ferrite (α). The main alloying elements are chromium (17 – 20%) and nickel (8 – 13%). These grades have a low carbon content (typically below 0.04%) in order to prevent the formation of chromium carbides when exposed to temperatures exceeding 400°C. The addition of molybdenum (2 – 3%) increases resistance to pitting corrosion.
Stabilized austenitic stainless steels have an addition of titanium or niobium in proportion to the amount of carbon and nitrogen (typically min. 10 × C). This stabilization prevents the precipitation of chromium carbides when exposed to temperatures exceeding 400°C. Furthermore, the stabilized steels display good strength and creep resistance up to about 600°C.
Fully austenitic stainless steels are typically highly alloyed with chromium (20 – 25%), nickel (18 – 35%), molybdenum (2 – 7%) and nitrogen (up to 0.4%). The austenitic structure is stabilized by the addition of austenite forming elements such as carbon, nickel, manganese, nitrogen and
For more information and details about corrosion resistance, weldability and mechanical properties take a look at our Stainless Steel Handbook.