Stainless Steel 309 (UNS S30900)
Stainless Steel 309 is a highly alloyed austenitic material designed for excellent oxidation resistance and high strength at elevated temperatures. With a significantly higher Chromium (22-24%) and Nickel (12-15%) content than the 304 series, Type 309 is engineered to withstand continuous exposure to temperatures up to 1900° F (1038° C). It is often chosen for its ability to resist "scaling" and maintain its mechanical integrity in thermal environments that would cause standard stainless steels to degrade.
At Aries Alloys, we supply Stainless Steel 309 to the furnace and heat-treating industries. Our material is selected for its stable metallurgical structure and its capacity to perform in both oxidizing and slightly carburizing atmospheres.
High-Temperature Performance Features
- Superior Scaling Resistance: Provides exceptional protection against oxidation in continuous service up to 1900° F and intermittent service up to 1850° F.
- High-Heat Strength: Maintains higher creep and tensile strength at elevated temperatures than Type 304 or 316.
- Corrosion Versatility: While designed for heat, it also offers excellent resistance to marine environments and sulfate liquors.
- Stability in Thermal Cycling: Resists the damaging effects of repeated heating and cooling cycles better than lower-alloyed stainless steels.
- Good Fabricability: Despite its high alloy content, it can be easily welded and formed using standard commercial methods.
Technical Profile & Composition
The Chromium-Nickel Advantage:
The secret to Type 309’s heat resistance is its high Chromium content, which forms a dense, protective oxide scale on the surface. The elevated Nickel content ensures the material remains austenitic and ductile, providing the toughness required for structural components in high-heat zones.
Mechanical & Physical Data:
- Density: 8.00 g/cm^3
- Non-Magnetic: Remains non-magnetic in the annealed condition and generally stays non-magnetic after cold working.
- Thermal Expansion: Low thermal expansion rates help prevent warping in furnace applications.
- Note on Service: For applications requiring even higher heat resistance or resistance to carburization, the low-carbon 309S or the more robust 310 series may be considered.
Primary Industrial Use Cases
Aries Alloys provides Stainless Steel 309 for critical heat-intensive applications:
- Furnace Components: Baffles, burner parts, muffle liners, and firebox sheets.
- Petrochemical Refineries: Catalytic recovery systems, flare tips, and thermowells.
- Power Generation: Coal pulverizer parts and boiler tube supports.
- Waste Incineration: Grates, ducting, and structural supports exposed to high-heat combustion.
- Heat Exchangers: Specialized tubing and plates for high-temperature fluid transfer.
Product Availability at Aries Alloys
We stock and supply Stainless Steel 309 in several formats complying with ASTM A240 and A167:
- Sheets & Plates: Available in various gauges for the fabrication of furnace linings and heat shields.
- Round & Hex Bars: High-strength rods for machining hangers, bolts, and supports.
- Seamless & Welded Tubes: For use in radiant tubes and high-temperature process piping.
- Custom Forgings: Flanges and specialized blocks for high-heat connectivity.