309 is a highly alloyed austenitic stainless steel used for its excellent oxidation resistance, high temperature strength and creep resistance. The lower nickel content of CS309 improves resistance to sulphur attack at high temperatures. It is tough and ductile, and can be readily fabricated and machined. 309S is the low-carbon version of CS 309, and is recommended for applications where sensitisation, and subsequent corrosion by high temperature gases or condensates during shutdown may pose a problem.
CS 309 is manufactured to ASTM A 167 and CS 309S to ASTM A240 specifications.
CS 309 / 309S is used exclusively for its high temperature oxidation resistance. It is common for CS 309, 310 and 321 to be used in the same piece of equipment in the various temperature regions.
0.12 BTU/lb-°F (32 – 212°F)
502 J/kg-°K (0 – 100°C)
Modulus of Elasticity
28.5 x 106 psi
Thermal Conductivity 212°F (100°C)
2500 – 2590°F
1480 – 1530°C
30.7 Microhm-in at 68°C
78 Microhm-cm at 20°C