Type 309 (UNS S30900)
Type 309 is a high temperature chromium nickel austenitic stainless steel that resists oxidation at temperatures up to 1900˚F in dry air at constant temperature. Under thermal cycling conditions this grade resists oxidation up to a temperature of approximately 1850˚F. Type 309 has good sulfidation resistance but low resistance to carburization and should not be used in highly carburizing atmospheres. Type 309 is non-magnetic in the annealed and cold worked conditions and is as resistant to corrosion as Type 304/304L.