309/309S STAINLESS STEEL

309 GENERAL PROPERTIES

Alloys 309 and 309S are austenitic chromium-nickel stainless steels that are often used for higher temperature applications. Due to their high chromium and nickel content, Alloys 309 and 309S are highly corrosion resistant, have outstanding resistance to oxidation, and excellent heat resistance while providing good strength at room and elevated temperatures. The only significant difference between 309 and 309S is the carbon content. Alloy 309S has a much less carbon composition which minimizes carbide precipitation and improves weldability.

Specifications: UNS S30900/S30908

APPLICATIONS:

Alloys 309 and 309S are used exclusively for their high temperature oxidation resistance, excellent high temperature strength, along with their resistance to creep deformation and environmental attack. Some examples include, but are not limited to:

Heating elements
Aircraft and jet engine parts
Heat exchangers
Carburizing annealing products
Sulfite liquor handling equipment
Kiln liners
Boiler baffles
Refinery and chemical processing equipment
Auto exhaust parts

STANDARDS:

ASTM/ASME: UNS S30900/S30908
EURONORM: FeMi35Cr20Cu4Mo2
DIN: 2.4660

309 CORROSION RESISTANCE

Provide excellent corrosion resistance
More resistant to marine atmospheres than Alloy 304
Often used at higher temperatures to take advantage of their oxidation resistance
Have high resistance to sulfite liquors
Generally considered heat resistant alloys
Destructive scaling temperature is approximately 2000^oF
Good scaling resistance with regard to continuous and intermittent service

HIGH TEMPERATURE CORROSION

Alloy 309 resists high temperature corrosion in most in-service conditions. Operating temperatures are as follows:
- Oxidizing conditions (max. sulfur content–2 g/m3)
  - 1922°F (1050°C) continuous service
  - 2012°F (1100°C) peak temperature
- Oxidizing conditions (max. sulfur greater than 2 g/m3)
  - 1742°F (950°C) maximum temperature
- Low oxygen atmosphere (max. sulfur content–2 g/m3)
  - 1832°F (1000°C) maximum temperature
- Nitriding or carburizing atmospheres
  - 1562–1742°F (850–950°C) maximum

The alloy does not perform as well as Alloy 600 (UNS N06600) or Alloy 800 (UNS N08800) in reducing, nitriding or carburizing atmospheres, but it does outperform most heat resistant stainless steels in these conditions.

309 HEAT TREATMENT

Cannot be hardened through heat treatment because the consist solely of austenite at room temperature
Higher tensile and yield strengths that can be obtained through cold working and not followed by full annealing are not stable at the higher temperatures where these alloys are used
Creep properties can be negatively affected by the use of cold worked material at these higher temperatures

FABRICATION

Can be roll formed, stamped, and drawn readily
In process annealing is often required to reduce hardness and increase ductility

WELDABILITY

The austenitic class of stainless steels is generally considered to be weldable
Generally considered to have weldability equivalent to the most common alloys of the austenitic class 304 and 304L
Special consideration is needed to compensate for a higher coefficient of thermal expansion to avoid warping and distortion

309 Chemical Properties:

	C	Mn	Si	P	S	Cr	Ni	Fe
309	max: 0.20	2.0 max	0.75 max	0.045 max	0.03 max	min: 22.0 max: 24.0	min: 12.0 max: 15.0	Balance
309H	min: 0.04 max: 0.10	2.0 max	0.75 max	0.045 max	0.03 max	min: 22.0 max: 24.0	min: 12.0 max: 15.0	Balance

309 Mechanical Properties:

Grade	Tensile Strength ksi (min)	Yield Strength 0.2% ksi (min)	Elongation %	Hardness (Brinell) MAX
309/H	40	30	40	217

309 Physical Properties:

Density lbm/in^3	Thermal Conductivity (BTU/h ft. °F)	Electrical Resistivity (in x 10^-6)	Modulus of Elasticity (psi x 10^6)	Coefficient of Thermal Expansion (in/in)/ °F x 10^-6	Specific Heat (BTU/lb/ °F)	Melting Range (°F)
at 68°F: 0.285	9.0 at 32- 212°F	30.7 at 68°F	28.5	8.28 at 32 – 212°F	0.1200 at 68°F to 212°F	2500-2590

309/309S STAINLESS STEEL

GENERAL PROPERTIES

APPLICATIONS