Alloy 309/309S (UNS S30900/S30908) austenitic stainless steel is typically used for elevated temperature applications. Its high chromium and nickel content provides comparable corrosion resistance, superior resistance to oxidation, and the retention of a larger fraction of room temperature strength than the common austenitic Alloy 304

Alloy 309/309S/309H(UNS S30900, S30908, S30909) W. Nr. 1.4833

General Properties

Alloy 309 (UNS S30900) is an austenitic stainless steel developed for use in high temperature corrosion resistance applications. The alloy resists oxidation up to 1900°F (1038°C) under non-cyclic conditions. Frequent thermal cycling reduces oxidation resistance to approximately 1850°F (1010°C).

Because of its high chromium and low nickel content, Alloy 309 can be utilized in sulfur containing atmospheres up to 1832°F (1000°C). The alloy is not recommended for use in highly carburizing atmospheres since it exhibits only moderate resistance to carbon absorption. Alloy 309 can be utilized in slightly oxidizing, nitriding, cementing and thermal cycling applications, albeit, the maximum service temperature must be reduced.

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.

309S (UNS S30908) 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.

Alloy 309 can be easily welded and processed by standard shop fabrication practices.

Applications

Furnaces — burners, doors, fans, piping and recuperators

Fluidized Bed Furnaces — grids, piping, wind boxes

Paper Mill Equipment

Petroleum Refining — catalytic recovery systems, recuperators

Power Generation — pulverized coal burners, tube hangers

Thermal Processing — annealing covers and boxes, burners grids, doors, fans, lead pans and neutral salt pots, muffles and retorts, recuperators, walking beams

Waste Treatment — incinerators, rotary kilns and calciners

Chemical Analysis

Weight % (all values are maximum unless a range is otherwise indicated)

Mechanical Properties

Typicals Values at 68°F (20°C)