Alloy 309/309S (UNS S30900/S30908) austenitic stainless steel is typically used for elevated temperature applications. Its high chromium and nickel content provides comparable corrosion resistance, superior resistance to oxidation, and the retention of a larger fraction of room temperature strength than the common austenitic Alloy 304.
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 SX309 improves resistance to sulphur attack at high temperature. It is tough and ductile, and can be readily fabricated and machined. 309S is the low-carbon version of 309, and is recommended for applications where sensitisation, and subsequent corrosion by high temperature gases or condensates during shutdown may pose a problem.309 is manufactured to ASTM A 167 and 309S to ASTM A240 specifications.
Grade 309 Stainless Steel is used often for higher temperature applications. While its oxidation resistance surpasses that of alloy 310, its resistance to corrosion is equivalent to that of alloy 310. Alloy 309 is highly weldable and cold formable, although it does require stronger forming machines and continuously increasing pressure. Typical machining methods are used for stainless steel grade 309, but it is tougher and does tend to harden more quickly. Like 310 Stainless Steel, Grade 309 Stainless Steel has a high chromium and nickel content which grants excellent resistance to aqueous corrosion.
General Properties
Chemical Composition
Physical Properties
Heat Treatment/Annealing
Fabrication Characteristics
Application
Welding
Other Forms of Degradation
Aqueous Corrosion Resistance
Typical Short-Term Mechanical Properties
Elevated Temperature Oxidation Resistance
309 Technical Data
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 SX309 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 309, and is recommended for applications where sensitisation, and subsequent corrosion by high temperature gases or condensates during shutdown may pose a problem.
309 is manufactured to ASTM A 167 and 309S to ASTM A240 specifications.
Typical Applications
309 / 309S is used exclusively for its high temperature oxidation resistance. It is common for SX 309, 310 and 321 to be used in the same piece of equipment in the various temperature regions.
Chemical Composition (ASTM A240)
| SX |
C |
Mn |
P |
S |
Si |
Cr |
Ni |
309
309S |
0.20 max
0.08 max |
2.00
max |
0.045
max |
0.030
max |
1.00
max |
22.0 -
24.0 |
12.0 -
15.0 |
Typical Properties in the Annealed Condition
The properties quoted in this publication are typical of mill production and unless indicated should not be regarded as guaranteed minimum values for specification purposes.
1. Mechanical Properties at Room Temperature
| |
SX 309 |
SX 309S |
| |
TYPICAL |
MIN |
TYPICAL |
MIN |
| Tensile Stength MPa |
560 |
515 |
540 |
515 |
| Proof Stress (0.2% Offset) MPa |
285 |
205 |
280 |
205 |
Elongation
(Percent in 50 mm) |
54 |
40 |
54 |
40 |
| Hardness (Brinell) |
164 |
|
159 |
|
| Endurance (fatigue) limit MPa |
260 |
|
260 |
|
2. Properties at Elevated Temperatures
The values quoted are those for SX 309
Short Time Elevated Temperature Tensile Stress
| Temperature |
oC |
550 |
650 |
750 |
850 |
950 |
1 050 |
| Tensile Stress |
MPa |
440 |
360 |
240 |
150 |
70 |
30 |
Creep Data
Stress to develop a creep rate of 1% in the time indicated at the temperature indicated.
| Time |
TemperatureoC |
550 |
600 |
650 |
700 |
750 |
800 |
10 000 h
100 000 h |
Stress MPa
Stress MPa |
100
75 |
80
50 |
60
30 |
30
20 |
25
10 |
10
5 |
Creep Rupture Stress
| Time |
Temperature oC |
600 |
700 |
800 |
900 |
1 000 |
1 000 h
10 000 h
100 000 h |
Stress MPa
Stress MPa
Stress MPa |
180
150
100 |
90
50
40 |
35
30
20 |
20
10
5 |
5
2
- |
Maximum Recommended Service
Temperature
(Oxidising Conditions)
Continuous 1 100oC
Intermittent 980
Thermal Processing
1. Annealing. Heat between 1 050oC and 1 150oC and water quench. This treatment ensures that all carbides are in solution.
2. Stress Relieving 250-400oC for 1 hour.
3. Hot Working
Initial forging and pressure 1150-1 200oC
Finishing temperature 1000oC
Note: Soaking times to ensure uniformity of temperature are up to 12 times that required for mild and carbon steels.
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