Nitronic 50® stainless steel, also known as UNS S20910 and XM-19, is an austenitic stainless steel with a blend of strength and corrosion resistance that is better than Stainless Steels 316, 316/316L, 317, and 317/317L. In fact, XM-19 has twice the yield strength at room temperature compared to Stainless Steels 316/316L and 317/317L. Additionally, it has good mechanical properties at elevated and sub-zero temperatures. Other characteristics that set XM-19 apart from other grades of stainless steel are that it does not become magnetic when severely cold worked and it has outstanding corrosion resistance in harsh environments such as marine applications.
XM-19 is composed of between 20% and 23% chromium, 11% to 13% nickel, 4% to 6% manganese, and 1.5% to 3% molybdenum, with the balance being iron. Also found in XM-19 are trace amounts of carbon, silicon, sulfur, phosphorus, nitrogen, columbium (or niobium) and vanadium. As noted previously, it is much stronger than Stainless Steels 316/316L and 317/317L; however, the same fabrication equipment and procedures used for the Stainless Steel 300 grades can be utilized for XM-19. In addition, the same cooling techniques used for Stainless Steels 316/316L and 317/317L can be utilized for XM-19.
XM-19 can be a confusing alloy to work with, as there are three different types of conditions used for numerous applications. The three conditions are annealed, as-rolled and high strength. As-rolled is a term used by the mill to state the fact that it is a “rolled” material. All conditions of XM-19 are first rolled. Both the annealed condition and the as-rolled condition are rolled at the same temperature. To acquire XM-19 annealed, the material would first be rolled, followed by either a mill or local annealing process which lowers the tensile and yield properties resulting in a more workable material. On the other hand, transforming XM-19 into the high strength condition can only be done at the mill after the original rolling process, which is done at a lower temperature than annealed and as-rolled material to further help increase the properties. Then high strength material is rolled a second time and later cold worked, which again increases the physical properties of the material even more.