Types 309 Stainless Steel and 309S are austenitic chromium-nickel stainless steels that provide excellent corrosion resistance and heat resistance plus good strength at room and elevated temperatures. Type 309S Stainless Steel is identical to Type 309 except for a lower carbon content that minimizes carbide precipitation and improves weldability. They are essentially nonmagnetic as annealed and become lightly magnetic when cold worked.
ASTM A167 (309), ASTM A240 (309S)
furnace parts, heating elements, aircraft and jet engine parts, heat exchangers, sulfite liquor handling equipment, kiln liners, boiler baffles, refinery and chemical processing equipment, and auto exhaust parts
|Carbon||0.20 max.||0.08 max.|
|Manganese||2.00 max.||2.00 max.|
|Sulfur||0.030 max.||0.030 max.|
|Phosphorus||0.045 max.||0.045 max.|
|Silicon||0.75 max.||0.75 max.|
|Chromium||22.0 – 24.0||22.0 – 24.0|
|Nickel||12.0 – 15.0||12.0 – 15.0|
|Type||Yield Strength 0.2% offset (KSI)||Tensile Strength (KSI)||% Elongation (2″ Gauge length)|
|309||30 min.||75 min.||40 min.|
|309S||30 min.||75 min.||40 min.|
|Density (lb./ in^2) @ RT||0.29|
|Modulus of Elasticity in Tension (psi x 10^6)||29.0|
|Specific Heat (BTU/o F/lb.)||32 to 212 oF||0.12|
|Thermal Conductivity (BTU/hr/ft^2/ft)||212oF||9.0|
|Mean Coefficient of Thermal Expansion (in. x 10^-6 per o F)||32 to 212oF||8.3|
|32 to 600oF||9.3|
|32 to 1,000oF||9.6|
|32 to 1,200oF||10.0|
|Electrical Resistivity (micro ohms – cm)||at 70oF||39.8|
|Melting Point Range (oF)||2550 – 2650|
|Oxidation Resistance – Continuous Service(oF)||2000|
|Oxidation Resistance – Intermittent Service(oF)||1800|
These alloys are not hardenable by heat treatment. Anneal at 1900 – 2050°F (1038 – 1121°C), then water quench or rapidly air cool.
Types 309 and 309S Stainless Steels can be roll formed, stamped and drawn readily. In-process annealing is usually required to reduce hardness and increase ductility.
Type 309 is generally considered to have weldability nearly equivalent to the most common alloys of this class, Types 304 and 304L. When a weld filler is needed, AWS E/ER 309 and 310 are most often specified.
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.