Key Feature

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

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

Common Designations

UNS S30900 (309), S30908 (309S)
AISI 309, 309S
ASTM A276 (Stainless Steel Bars)
ASTM A479 (Bars for Pressure Vessels)
EN 1.4828 (309), 1.4833 (309S)
JIS SUS309, SUS309S

ASTM A276 is the primary specification for high-temperature bar applications.

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
Machinability: 40% of B1112 steel

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.

Available Forms

Rounds: 6mm - 200mm diameter
Squares: 6mm - 100mm
Hexagons: 6mm - 75mm
Flats: Various sizes
Billets: For forging applications

Available in sizes suitable for high-temperature component manufacturing.

Surface Conditions

Hot Rolled: Black bar
Cold Drawn: Bright finish
Centerless Ground: Precision ground
Polished: For specific applications
Peeled: Improved surface for machining

Various surface finishes available for different application requirements.

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.

Machining Characteristics

• More difficult to machine than 304
• Higher tool wear due to alloy content
• Good chip control• Surface finish achievable with proper techniques
• Requires rigid setups

Higher alloy content increases machining difficulty compared to 304.

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 assemblies.

High-Temperature Strength

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 considerations.

Key Standards

ASTM A276 309/309S: Stainless Steel Bars
ASTM A479 309/309S: Bars for Pressure Vessels
ASTM A484: General Requirements
EN 10088-3: Stainless Steel Bars
JIS G4303: Stainless Steel Bars
ASME SA479: Code Construction

Recognized in international standards for high-temperature applications.

Common Applications

• Heat Treatment Fixtures: Baskets, trays, hangers, furnace components
• Furnace Parts: Radiant tubes, retorts, muffles, burner parts
• Thermal Processing: Kiln furniture, pyrolysis components, calciner parts
• Power Generation: Boiler components, superheater supports, ducting parts
• Chemical Processing: High-temperature reactor parts, reformer components
• Automotive: Exhaust system components, turbocharger parts
• Food Service: Oven components, fryer parts, high-temperature processing equipment

Ideal for bar stock applications operating continuously between 800-1100°C.