Austenitic 309H (UNS S30909) Stainless Steel Plate/Coil
309H (S30909) Austenitic Stainless Steel Plate/Coil: High-Temperature Strength & Oxidation Resistance
Comprehensive datasheet for 309H (UNS S30909) austenitic stainless steel plate and coil. Covers chemical composition, mechanical properties at room and elevated temperatures, physical properties, equivalent grades, and applications in furnaces, heat exchangers, and thermal processing equipment.
Hot rolling, cold rolling, annealing, pickling, welding, forming
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Austenitic 309H Stainless Steel Plate/Coil Introduction
AISI 309H (UNS S30909) is a high-carbon modification of the basic 309 austenitic stainless steel, designed for enhanced high-temperature strength and creep resistance. As an alloy with 22–24% chromium and 12–15% nickel, it offers superior oxidation resistance up to 1900°F (1038°C) under continuous service and excellent sulfidation resistance in many environments. The higher carbon content (0.04–0.10%) compared to 309S promotes greater tensile and creep strength at elevated temperatures, making it ideal for components exposed to thermal cycling and sustained loads at high heat.
- Excellent oxidation resistance and scaling resistance
- Good high-temperature strength and creep-rupture properties
- Resistant to carburization and reducing/oxidizing atmospheres
- Readily welded and fabricated using conventional techniques
- Non-magnetic in the annealed condition, but may become slightly magnetic after cold working
Typical applications include furnace parts, heat exchangers, kiln linings, boiler baffles, and other equipment in the petrochemical, power generation, and heat treatment industries.
Austenitic 309H Stainless Steel Plate/Coil Chemical Composition per ASTM A240 for 309H
The chemical composition is in accordance with ASTM A240/A240M standard for chromium-nickel stainless steel plate, sheet, and strip. All values are maximum unless a range is indicated. The higher carbon content distinguishes 309H from 309 and 309S, providing improved high-temperature strength.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | 0.04–0.10 | Higher carbon for high-temp. strength |
| Manganese (Mn) | ≤ 2.00 | |
| Silicon (Si) | ≤ 1.00 | |
| Phosphorus (P) | ≤ 0.045 | |
| Sulfur (S) | ≤ 0.030 | |
| Chromium (Cr) | 22.0–24.0 | Key element for oxidation resistance |
| Nickel (Ni) | 12.0–15.0 | Stabilizes austenitic structure |
| Iron (Fe) | Balance |
Austenitic 309H Stainless Steel Plate/Coil Thermal and Electrical Physical Properties
Physical properties of 309H (S30909) in the annealed condition at room temperature unless otherwise noted. These are typical values commonly referenced in technical literature and may vary slightly with specific product form and processing. Thermal conductivity and expansion are critical for design in high-temperature applications.
| Property | Typical Value | Unit | Test Condition / Reference |
|---|---|---|---|
| Density (ρ) | 7.9 | g/cm³ | Room temperature |
| Elastic Modulus (E) | 200 | GPa | Room temperature (tension) |
| Shear Modulus (G) | 77 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.27–0.30 | – | Room temperature |
| Thermal Expansion Coefficient (α), 20–100°C | 15.0 | µm/m·K | Mean coefficient |
| Thermal Expansion Coefficient (α), 20–500°C | 17.0 | µm/m·K | Mean coefficient |
| Thermal Expansion Coefficient (α), 20–800°C | 18.0 | µm/m·K | Mean coefficient |
| Thermal Conductivity (λ) at 100°C | 15.6 | W/m·K | |
| Thermal Conductivity (λ) at 500°C | 21.6 | W/m·K | |
| Specific Heat Capacity (cp) | 500 | J/kg·K | Room temperature |
| Electrical Resistivity (ρe) | 0.78 | µΩ·m | Room temperature |
Austenitic 309H Stainless Steel Plate/Coil Mechanical Properties
Mechanical properties as specified in ASTM A240/A240M for 309H plate, sheet, and strip in the solution-annealed condition. These values represent minimum requirements unless noted. Properties may vary with thickness and product form. At elevated temperatures, the alloy retains significant strength, making it suitable for prolonged service above 650°C (1200°F).
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | ≥ 515 | MPa | Ambient |
| Yield Strength (ReH, 0.2% offset) | ≥ 205 | MPa | Ambient |
| Elongation (A) in 50 mm (2 in.) | ≥ 40 | % | Ambient |
| Hardness (Rockwell B) | ≤ 95 | HRB | Ambient |
| Hardness (Brinell) | ≤ 217 | HBW | Ambient |
| Bend Test (bending angle) | 180° | deg | Bend diameter = thickness; no cracks |
Austenitic 309H Stainless Steel Plate/Coil Directly Equivalent Standards and Replaceable Grades
| Country/Region | Standard | Grade/Designation | Remarks |
|---|---|---|---|
| USA | ASTM A240 / ASME SA-240 | UNS S30909 (309H) | Original standard; high carbon content for high-temperature service. |
| European Union | EN 10088-2 / EN 10095 | 1.4833 – X12CrNi23-13 | Carbon range 0.08–0.15% is slightly wider, but fully comparable in corrosion/oxidation resistance and strength. Often cross-referenced for 309H. |
| International (ISO) | ISO 15510 | X12CrNi23-13 | Essentially identical to EN 1.4833. |
| Japan | JIS G4304 / G4305 | SUS 309H (tentative) | The JIS standard does not officially list a '309H'; SUS 309 is closer to 309S. For high-carbon requirements, EN or ASTM grades are typically specified. Verify with supplier. |
| China | GB/T 4237-2015 | 06Cr23Ni13 (0Cr23Ni13) for general, no exact H designation | The Chinese standard 309-type has C ≤0.08%. For higher carbon, special grade such as 16Cr23Ni13 (C 0.12-0.20) may be used but is not a direct equivalent. |
Austenitic 309H Stainless Steel Plate/Coil Application Introduction
309H stainless steel is primarily utilized in high-temperature environments where both oxidation resistance and structural strength are required. It is widely employed in industrial heating, petrochemical processing, and power generation. The alloy can be easily formed, welded, and machined using standard processes, though the higher carbon content requires attention to welding procedures to avoid hot cracking. Post-weld annealing is often recommended to restore full corrosion resistance. Key industries include:
Product Applications: Furnace muffles, retorts, and radiant tubes, Heat exchanger tubing and plates, Boiler baffles and superheater hangers, Kiln linings and burner components, Annealing covers and boxes, Flare tips and stack liners, Conveyor belts and furnace mesh belts
Processed into products: Welded tube-to-tubesheet joints in heat exchangers, Expansion bellows in high-temperature ducting, Thermowell protection tubes, Hangers and supports for superheater elements, Combustion chamber liners, Batch annealing furnace base trays, Pyrolysis reactor internals
Application industries: Petrochemical and Refining, Power Generation (fossil fuel and nuclear), Industrial Furnace Construction, Heat Treatment and Thermal Processing, Waste Incineration, Pulp and Paper (recovery boilers), Mining and Mineral Processing (roasters)
Austenitic 309H Stainless Steel Plate/Coil Grades with Similar Performance
| Country/Region | Standard | Grade/Designation | Remarks |
|---|---|---|---|
| USA | ASTM A240 | 309S (UNS S30908) | Lower carbon (max 0.08). Slightly lower high-temperature strength but excellent oxidation resistance. Often used as a replacement when welding is a concern (less sensitization). |
| USA | ASTM A240 | 310H (UNS S31009) | Higher chromium (24-26%) and nickel (19-22%). Superior oxidation resistance up to 1100°C but more expensive. Can replace 309H in more demanding thermal environments. |
| European Union | EN 10095 | 1.4828 – X15CrNiSi20-12 | Contains silicon for improved scaling resistance. Carbon 0.12–0.20%. Used for similar furnace components, but with slightly different mechanical properties. |
| European Union | EN 10095 | 1.4845 – X12CrNi25-21 | Higher Cr-Ni content comparable to 310S. Superior creep resistance; may be considered where 309H reaches its limit. |
Notes:
Welding: For 309H, use matching filler metals (AWS A5.9 E309H-16 or similar) to maintain high-temperature strength. Preheating is usually not required; interpass temperature should be kept below 150°C. Heat treatment: Annealing at 1038–1121°C (1900–2050°F) followed by water quenching or rapid air cool. Do not use slow cooling as it may induce sensitization and reduce corrosion resistance. Scaling limit: Continuous service up to 1150°C (2100°F) in dry air, but mechanical properties degrade at higher temperatures—use design codes for creep-limited applications. Availability: Standard plate thicknesses from 3/16 in. to 3 in. (4.76 mm to 76.2 mm) and coil gauges from 0.018 in. to 0.250 in. (0.46 mm to 6.35 mm) typically in stock at major distributors.
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