Key Feature

The High-Temperature Workhorse Piping Solution. Optimized chromium-nickel balance provides excellent oxidation resistance at 800-1100°C, bridging the gap between 304 and 310S for piping applications.

The most cost-effective high-temperature stainless steel pipe for many industrial heating applications.

Common Designations

UNS S30900 (309), S30908 (309S)
AISI 309, 309S
ASTM A312 TP309/309S (Seamless/Welded)
EN 1.4828 (309), 1.4833 (309S)
JIS SUS309, SUS309S

ASTM A312 is the primary specification for high-temperature pressure pipe.

Chemical Composition (Typical wt.%)

C: ≤0.20 (309), ≤0.08 (309S)Cr: 22.0 - 24.0Ni: 12.0 - 15.0Mn: ≤ 2.00
Si: ≤ 1.00
P: ≤ 0.045
S: ≤ 0.030

Higher Cr than 304 (22-24% vs 18-20%); lower Ni than 310S (12-15% vs 19-22%).

Mechanical Properties

Tensile Strength: ≥ 515 MPa
Yield Strength: ≥ 205 MPa
Elongation: ≥ 40%
Hardness: ≤ 217 HB

Similar room-temperature properties to 304, but superior high-temperature strength.

Elevated Temperature Properties

Continuous Service: Up to 1150°C
Intermittent Service: Up to 1100°C
Oxidation Resistance: Excellent up to 1050°C
Creep Strength: Good up to 950°C

Better than 304 above 800°C; slightly lower maximum temperature than 310S.

Physical Properties

Density: 7.98 g/cm³
Melting Range: 1400 - 1450 °C
Thermal Expansion: 16.0 × 10⁻⁶/K (20-100°C)
Thermal Conductivity: 14.9 W/m·K (100°C)
Non-magnetic when annealed

Similar physical properties to other high-temperature austenitic grades.

Corrosion Resistance

Excellent oxidation resistance at high temperatures. Good general corrosion resistance comparable to 304. Moderate chloride resistance.

Not designed for marine or severe chloride environments; excels in oxidizing high-temperature environments.

Welding Characteristics

Good weldability with standard methods
309S preferred for welded structures
Possible sensitization with 309 grade
Post-weld annealing recommended for 309

309S eliminates sensitization concerns in welded piping systems.

Pressure Ratings

Schedule 10S/40S: Standard process piping
Schedule 80S/160: High temperature service
ASME B31.3 compliant for elevated temps

Designed for high-temperature pressure applications per piping codes.

Temperature-Pressure Ratings

At 800°C: ~25% of room temp strength
At 900°C: ~15% of room temp strength
At 1000°C: ~8% of room temp strength

Significant strength reduction at high temperatures requires proper design.

Key Standards

ASTM A312 TP309/309S: Seamless & Welded Pipe
ASTM A358 TP309/309S: EFW Pipe
ASTM A213 TP309/309S: Boiler Tubes
EN 10216-5: Seamless Pressure Tubes
ASME SA312: Code Construction

Recognized in international pressure piping standards.

Common Applications

• Furnace Piping: Radiant tubes, burner pipes, furnace exhaust systems
• Heat Treatment Equipment: Annealing line piping, carburizing systems
• Thermal Processing: Kiln piping, pyrolysis systems, calciner tubes
• Power Generation: Boiler components, superheater supports, ducting
• Chemical Processing: High-temperature reactor piping, reformer systems
• Food Service: Oven exhaust piping, fryer exhaust systems
• Automotive: Exhaust system components, turbocharger piping

Ideal for piping systems operating continuously between 800-1100°C.