309/309S/309H Stainless Steel Plate – High-Temperature Corrosion-Resistant Alloy
Sandmeyer Steel Company stocks Alloy 309/309S heat resistant stainless steel plate in thicknesses from 3/16″ through 3″.
Available thicknesses for Alloy 309/309S:
| 3/16" | 1/4" | 5/16" | 3/8" | 1/2" | 5/8" | 3/4" | 1" |
| 4.8mm | 6.3mm | 7.9mm | 9.5mm | 12.7mm | 15.9mm | 19mm | 25.4mm |
| 1 1/4" | 1 1/2" | 1 5/8" | 1 3/4" | 2" | 2 1/2" | 3" | |
| 31.8mm | 38.1mm | 41.3mm | 44.5mm | 50.8mm | 63.5mm | 76.2mm |
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.
Specification Sheet Overview
for Alloy 309/309S/309H (UNS S30900, S30908, S30909)
W. Nr. 1.4833:
General Properties
Alloy 309 (UNS S30900) is an austenitic stainless steel developed for use in high temperature corrosion resistance applications. The alloy resists oxidation up to 1900°F (1038°C) under non-cyclic conditions. Frequent thermal cycling reduces oxidation resistance to approximately 1850°F (1010°C).
Because of its high chromium and low nickel content, Alloy 309 can be utilized in sulfur containing atmospheres up to 1832°F (1000°C). The alloy is not recommended for use in highly carburizing atmospheres since it exhibits only moderate resistance to carbon absorption. Alloy 309 can be utilized in slightly oxidizing, nitriding, cementing and thermal cycling applications, albeit, the maximum service temperature must be reduced.
When heated between 1202 – 1742°F (650 – 950°C) the alloy is subject to sigma phase precipitation. A solution annealing treatment at 2012 – 2102°F (1100 – 1150°C) will restore a degree of toughness.
309S (UNS S30908) is the low carbon version of the alloy. It is utilized for ease of fabrication. 309H (UNS S30909) is a high carbon modification developed for enhanced creep resistance. In most instances the grain size and carbon content of the plate can meet both the 309S and 309H requirements.
Alloy 309 can be easily welded and processed by standard shop fabrication practices.
Applications
- Furnaces — burners, doors, fans, piping and recuperators
- Fluidized Bed Furnaces — grids, piping, wind boxes
- Paper Mill Equipment
- Petroleum Refining — catalytic recovery systems, recuperators
- Power Generation — pulverized coal burners, tube hangers
- Thermal Processing — annealing covers and boxes, burners grids, doors, fans, lead pans and neutral salt pots, muffles and retorts, recuperators, walking beams
- Waste Treatment — incinerators, rotary kilns and calciners
Corrosion Resistance
Wet Corrosion
Alloy 309 is not designed for service in wet corrosive environments. The high carbon content, which is present to enhance creep properties, has a detrimental effect on aqueous corrosion resistance. The alloy is prone to intergranular corrosion after long term exposure at high temperatures. However, due to its high chromium content (23%), Alloy 309 is more corrosion resistant than most heat resistant alloys.
High Temperature Corrosion
Alloy 309 resists high temperature corrosion in most in-service conditions. Operating temperatures are as follows:
Oxidizing conditions (max. sulfur content – 2 g/m3)
1922°F (1050°C) continuous service
2012°F (1100°C) peak temperature
Oxidizing conditions (max. sulfur greater than 2 g/m3)
1742°F (950°C) maximum temperature
Low oxygen atmosphere (max. sulfur content – 2 g/m3)
1832°F (1000°C) maximum temperature
Nitriding or carburizing atmospheres
1562 –1742°F (850 – 950°C) maximum
The alloy does not perform as well as Alloy 600 (UNS N06600) or Alloy 800 (UNS N08800) in reducing, nitriding or carburizing atmospheres, but it does outperform most heat resistant stainless steels in these conditions.
Creep Properties
Typical Creep Properties
| °C | °F | 1000 H | 10000 H | 100000 H | 1000 H | 10000 H | 100000 H |
| 600 | 1112 | 120 | 80 | 40 | 190 | 120 | 65 |
| 700 | 1292 | 50 | 25 | 20 | 75 | 36 | 16 |
| 800 | 1472 | 20 | 10 | 8 | 35 | 18 | 7.5 |
| 900 | 1652 | 8 | 4 | 3 | 15 | 8.5 | 3 |
| 1000 | 1832 | 4 | 2.5 | 1.5 | 8 | 4 | 1.5 |
Chemical Analysis
Weight % (all values are maximum unless a range is otherwise indicated)
| Element | 309 | 309S | 309H |
|---|---|---|---|
| Chromium | 22.0 min.-24.0 max. | 22.0 min.-24.0 max. | 22.0 min.-24.0 max. |
| Nickel | 12.0 min.-15.0 max. | 12.0 min.-15.0 max. | 12.0 min.-15.0 max. |
| Carbon | 0.20 | 0.08 | 0.04 min.-0.10 max. |
| Manganese | 2.00 | 2.00 | 2.00 |
| Phosphorus | 0.045 | 0.045 | 0.045 |
| Sulfer | 0.030 | 0.030 | 0.030 |
| Silicon | 0.75 | 0.75 | 0.75 |
| Iron | Balance | Balance | Balance |
Density
0.285 lbs/in3
7.89 g/cm3
Specific Heat
0.12 BTU/lb-°F (32 – 212°F)
502 J/kg-°K (0 – 100°C)
Modulus of Elasticity
28.5 x 106 psi
193 GPa
Thermal Conductivity 212°F (100°C)
9.0 BTU/hr/ft2/ft/°F
15.6 W/m-°K
Melting Range
2500 – 2590°F
1480 – 1530°C
Electrical Resistivity
30.7 Microhm-in at 68°C
78 Microhm-cm at 20°C
Fabrication Data
Alloy 309 can be easily welded and processed by standard shop fabrication practices.
Hot Forming
Heat uniformly at 1742 – 2192°F (950 – 1200°C). After hot forming a final anneal at 1832 – 2101°F (1000 – 1150°C) followed by rapid quenching is recommended.
Cold Forming
The alloy is quite ductile and forms in a manner very similar to 316. Cold forming of pieces with long-term exposure to high temperatures is not recommended since the alloy is subject to carbide precipitation and sigma phase precipitants.
Welding
Alloy 309 can be readily welded by most standard processes including TIG, PLASMA, MIG, SMAW, SAW and FCAW.
Alloy 309/309S/309H Stainless Steel – Frequently Asked Questions
1. What are the primary differences between Alloy 309, 309S, and 309H stainless steels?
Alloy 309/309S (UNS S30900/S30908) is an austenitic stainless steel designed for high-temperature corrosion resistance. Alloy 309S is the low-carbon version, which enhances weldability and reduces the risk of carbide precipitation during welding. Alloy 309H (UNS S30909) has a higher carbon content, providing improved creep resistance at elevated temperatures. In most instances the grain size and carbon content of the plate can meet both the 309S and 309H requirements.
2. What is the maximum operating temperature for Alloy 309/309S/309H?
These alloys resist oxidation up to 1900°F (1038°C) under non-cyclic conditions. However, frequent thermal cycling reduces oxidation resistance to approximately 1850°F (1010°C).
3. In which applications are Alloy 309/309S/309H commonly used?
These alloys are typically used in high-temperature environments such as furnaces (burners, doors, fans, piping, recuperators), fluidized bed furnaces (grids, piping, wind boxes), paper mill equipment, petroleum refining (catalytic recovery systems, recuperators), power generation (pulverized coal burners, tube hangers), thermal processing (annealing covers and boxes, burner grids, doors, fans, lead pans, neutral salt pots, muffles, retorts, recuperators, walking beams), and waste treatment (incinerators, rotary kilns, calciners).
4. How does Alloy 309/309S/309H perform in corrosive environments?
These alloys offer superior resistance to oxidation and corrosion in high-temperature environments. However, they are not recommended for use in highly carburizing atmospheres due to moderate resistance to carbon absorption. They can be utilized in slightly oxidizing, nitriding, cementing, and thermal cycling applications, albeit with reduced maximum service temperatures.
5. Can Alloy 309/309S/309H be welded?
Yes, these alloys can be easily welded and processed by standard shop fabrication practices. For applications requiring the best corrosion resistance after welding, the low-carbon 309S variant is preferred to minimize carbide precipitation.
6. What standards and specifications apply to Alloy 309/309S/309H?
These alloys conform to several industry standards, including
• ASTM A240
• ASME SA240
• AMS 5523
7. What are the physical properties of Alloy 309/309S/309H?
Typical physical properties include:
• Density: 0.285 lbs/in³ (7.89 g/cm³)
• Modulus of Elasticity: 28.5 x 10⁶ psi (193 GPa)
• Melting Range: 2500–2590°F (1480–1530°C)
• Specific Heat: 0.12 BTU/lb-°F (32–212°F) 502 J/kg-°K (0 – 100°C)
• Thermal Conductivity at 212°F (100°C): 9.0 BTU/hr/ft²/ft/°F (15.6 W/m-K)
• Electrical Resistivity: 30.7 Microhm-in at 68°F (78 microhm-cm at 20°C)
8. What are the chemical compositions of Alloy 309, 309S, and 309H?
The typical chemical compositions are:
• Chromium: 22.0 min.-24.0 max
• Nickel: 12.0 min.-15.0 max.
• Carbon: 0.20% max (309), 0.08% max (309S), 0.04–0.10% (309H)
• Manganese: 2.00
• Phosphorus: 0.045
• Sulfur: 0.030
• Silicon: 0.75%
• Iron: Balance
9. What standards apply to Alloy 309/309S/309H stainless steel?
• ASTM……..A 240
• ASME……..SA 240
• AMS……….5523
10. What thicknesses of Alloy 309/309S/309H plate does Sandmeyer Steel stock?
Sandmeyer Steel stocks Alloy 309/309S/309H stainless steel plate in thicknesses ranging from 3/16″ (4.8 mm) through 3″ (76.2 mm), with custom cutting available to meet project needs.