Written by admin on 04/24/2010 – 5:22 pm
Summary
SX 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.
SX 309S is the low-carbon version of SX 309, and is recommended for applications where sensitisation, and subsequent corrosion by high temperature gases or condensates during shutdown may pose a problem.
SX 309 309S is manufactured to ASTM A 167 and SX 309S to ASTM A240 specifications.
Typical Applications
SX 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 980oC
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 1 150-1 200oC
Finishing temperature 1 000oC
Note: Soaking times to ensure uniformity of temperature are up to 12 times that required for mild and carbon steels.
