Alloy 309/309S Stainless Steel

Alloy 309/309S Stainless Steel

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)

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)