The main alloying elements of these steels are Chromium, Nickel, Manganese and Molybdenum. Nitrogen strongly increases the yield strength. Austenitic steel is often used where particularly high corrosion resistance is required, e.g. in the oil, gas and chemical industries, in sanitary and waste water technology, in the food industry and medical technology, but also in shipbuilding.
Austenitic stainless steels are essentially non-magnetic, have a medium yield strength, high work hardening tendency, high tensile strength, good ductility and excellent toughness even at low temperatures, are easy to weld and can be easily fabricated into complex shapes.
The most important alloying elements of such steels are Cr, Ni, Mn, Mo, C, N. The austenitic, face-centred cubic solid solution structure is achieved by a special balance of the alloying elements. Cr, Mo and others act as ferrite-stabilising elements in this context. Ni, Mn, C, N stabilise the austenitic solid solution. As a rule, a completely austenitic microstructure is aimed for in high-performance steels (super austenites); a small proportion of ferrite can occur in standard steels. This ferrite content makes these grades slightly ferromagnetic.
The corrosion resistance is essentially determined by the Cr and Mo content; the resistance to pitting and crevice corrosion is determined by the pitting corrosion equivalent PREN = %C+3.3%Mo + (16 -30)%N.
The resistance to intergranular corrosion is determined by the free Cr content, i.e. the Cr content not bound in the form of Cr carbides.
Standard steels with Ni contents of 10 to 15% Ni are particularly susceptible to stress corrosion cracking.
Austenitic high-performance steels are designed to be particularly resistant to corrosion under aggressive conditions, e.g. in strong acids, alkalis and chloride-containing media such as brackish water, seawater and brine. These types of steel tend to exhibit higher strength and greater resistance to stress corrosion cracking.
The mechanical strength in the steel group is determined by the alloy content, in particular the N content.
Austenitic Cr-Mn-Ni-Mo-N steels form a subgroup of this steel category. They have a higher initial strength and a more pronounced tendency to work hardening and are often considered a more economical alternative to Cr-Ni-Mo steels.
Austenitic steel is frequently used in the chemical industry, construction, waste water technology, sanitary engineering and the food industry, as well as in shipbuilding and medical technology. Good weldability plays an important role here.
In addition to corrosion resistance, easy cleaning after use also plays a major role in the decision in favour of these materials.