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).
Corrosion Resistance
Wet Corrosion
Alloy 309 is not designed for service in wet corrosive environments. The high carbon content, which is present to enhance creep properties, has a detrimental effect on aqueous corrosion resistance. The alloy is prone to intergranular corrosion after long term exposure at high temperatures. However, due to its high chromium content (23%), Alloy 309 is more corrosion resistant than most heat resistant alloys.
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
Chemical Analysis
Weight % (all values are maximum unless a range is otherwise indicated)
Element | 309 | 309S | 309H |
---|---|---|---|
Chromium | 22.0 min.-24.0 max. | 22.0 min.-24.0 max. | 22.0 min.-24.0 max. |
Nickel | 12.0 min.-15.0 max. | 12.0 min.-15.0 max. | 12.0 min.-15.0 max. |
Carbon | 0.20 | 0.08 | 0.04 min.-0.10 max. |
Manganese | 2.00 | 2.00 | 2.00 |
Phosphorus | 0.045 | 0.045 | 0.045 |
Sulfer | 0.030 | 0.030 | 0.030 |
Silicon | 0.75 | 0.75 | 0.75 |
Iron | Balance | Balance | Balance |
Physical Properties
Density
0.285 lbs/in3
7.89 g/cm3
Specific Heat
0.12 BTU/lb-°F (32 – 212°F)
502 J/kg-°K (0 – 100°C)
Modulus of Elasticity
28.5 x 106 psi
193 GPa
Thermal Conductivity 212°F (100°C)
9.0 BTU/hr/ft2/ft/°F
15.6 W/m-°K
Melting Range
2500 – 2590°F
1480 – 1530°C
Electrical Resistivity
30.7 Microhm-in at 68°C
78 Microhm-cm at 20°C
Mechanical Properties
Typical Values at 68°F (20°C)
Yield Strength 0.2% Offset | Ultimate Tensile Strength | Elongation in 2 in. | Hardness | ||
---|---|---|---|---|---|
psi (min.) | (MPa) | psi (min.) | (MPa) | % (min.) | (max.) |
45,000 | 310 | 85,000 | 586 | 50 | 202 (HBN) |