309S stainless steel is a highly alloyed austenitic stainless steel used for its excellent oxidation resistance, high-temperature strength, and creep resistance. The lower nickel content of Stainless Steel 309, compared to Stainless Steel 310, improves its resistance to hydrogen sulfide (H2S) attack at high temperatures. It is tough and ductile and can be readily fabricated and machined. SS 309S is the low-carbon version, and is recommended for applications where sensitization and subsequent corrosion by high temperature gases or condensates during shutdown may pose a problem. Stainless Steel 309S is used for its high-temperature oxidation resistance and/or resistance to H2S attack for applications such as furnace parts, firebox sheets, high-temperature containers, catalytic converters, and exhaust systems. Excellent oxidation resistance High temperature strength High creep resistance Tough and dectile Readily fabricated and machined Resistant to hydrogen sulfide attack at high temperatures Applications Furnace parts Muffles, Retorts Firebox sheets High temperature containers Catalytic converters Exhaust systems Radiant Tubes Fluidized bed coal combusters Petroleum refineries and steam boilers Thermowells Carbon Saggers Paper Mill Equipment Power boiler tube hangers Anchor bolts Gladd forming equipment Food processing industry Corrosion resistance Types 309 and 309S provide excellent general corrosion resistance. They are more resistant to marine atmospheres than Type 304. They exhibit high resistance to sulfite liquors and are useful for handling nitric acid, nitric-sulfuric acid mixtures, and acetic, citric, and lactic acids. These materials are generally considered heat-resisting alloys. Their destructive scaling temperature is about 2000 °F (1093 °C). They exhibit good scaling resistance in both continuous and intermittent service, but the alloys should not be used above 1800 °F (982 °C) for intermittent service. Formability Types 309 and 309S stainless steels can be roll formed, stamped and drawn readily. In process annealing is sometimes required to reduce hardness and restore ductility. Type 309 is extremely stable and will remain nonmagnetic when cold worked. Its lower elongation makes this grade somewhat more difficult to form than other 300 series austenitic grades. Weldability The austenitic class of stainless steels is generally considered to be weldable by the common fusion and resistance techniques. Special consideration is required to compensate for a higher coefficient of thermal expansion to avoid warping and distortion. Type 309 is generally considered to have weldability. Heattreatment These alloys are not hardenable by heat treatment. Annealing: Anneal at 1900 – 2050 °F (1038 – 1121 °C), then water quench or rapidly air cool.