Stainless Steel, AusteniticS32109 (321H) Fittings and Flanges

A higher carbon modification of stainless steel 321 which provides greater strength at elevated temperatures.

321H is able to withstand higher temperatures than type 321, due to its elevated carbon levels. While 321H displays the same welding and forming characteristics of type 321, the metal cannot be hardened by heat treatment.

It is utilized in situations where type 321 cannot withstand the high temperatures. Type 321H displays better resistance against creep than both 321 and 304 stainless steels.

321H also shows resistance against acid corrosion in a variety of environments. Lower temperatures provide better resistance, but the metal is able to withstand up to a 10% acid solution, that has been diluted, at elevated temperatures. However, the metal shows very little resistance against chlorine or sulfuric solutions at any given temperature.

Given their similar composition and characteristics, it is possible for stainless steels 321 and 321H to become dually certified.

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Chemical Composition


  • Aircraft exhaust stacks and manifolds
  • Jet engine parts
  • Weld equipment
  • Chemical processing equipment


  • Good low corrosion resistance to low content of hydrochloride and organic acids
  • Very good resistance to raised temperature

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