Austenitic stainless steels are non-magnetic and cannot be hardened by heat treatment Austenitic stainless steel is a type of steel alloy which is composed of iron, carbon, chromium, nickel, and other minor alloys. Austenitic steels can be divided into two groups: 300 series and 200 series. 300 series steels contain at least 8% nickel whereas 200 series steels replace portions of that nickel with cheaper alloys such as nitrogen or manganese. Austenitic is best known for its corrosion resistance which is why they are often used for stainless steel applications. Making up more than 70% of steel production, they are also one of the most commonly used stainless steels, with grade 304 being by far the most preferred type.