Alloy 309 and Alloy 309S are heat resistant varieties of stainless steel used in high temperature service. You can find 309 and 309S steel pipe and products in incinerators, furnaces, burners, kilns, annealing and carburizing boxes, combustion chambers, salt pots, thermo wells, gas turbines, retorts, flairs and equipment to handle sulfite liquor.
Properties
Alloy 309 and 309S is best known for high temperature service. This alloy works well up to 2000 °F, especially if oxidation resistance is required. 309 and 310 stainless steel are premier high temperature performers among the common stainless grades available from our stock. High nickel and chromium content and a coarse grain structure result in:
• Improved resistance to cyclic oxidation
• Increased resistance to sulfidation
• Better high temperature strength
• Improved resistance to intergranular corrosion
309S (UNS S30908) stainless steel is the low carbon version of the alloy. It is utilized for ease of fabrication.
309H (UNS S30909) is a high carbon modification developed for enhanced creep resistance. It most instances the grain size and carbon content of the plate can meet both the 309S and 309H requirements. When heated between 1202 – 1742°F (650 – 950°C) the alloy is subject to sigma phase precipitation. A solution annealing treatment at 2012 – 2102°F (1100 – 1150°C) will restore a degree of toughness. Alloy 309 can be easily welded and processed by standard shop fabrication practices.