About 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 304.
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. It most instances the grain size and carbon content of the plate can meet both the 309S and 309H requirements.
309 can be easily welded and processed by standard shop fabrication practices.
Product Form
Sheet / strip 125ksi: AMS 5501
Sheet /strip (ann): AMS 5501
Sheet / strip (ann): AMS 5513
Seamless tube: AMS 5560
1/4Hd Seamless/welded: AMS 5560
1/8Hd Seamless/welded: AMS 5564
Welded tube: AMS 5565
Seamless/welded tube: AMS 5566, AMS 5567, AMS 5569
Welded tube: AMS 5575
(304) Bar / Forgings: AMS 5639
(304L) Bar / Forgings:AMS 5647
Chemical Composition
| Weight% | C | P | Si | Ni | Mn | S | Cr | Fe | Mo | Cu |
| Alloy 309 | 0.08 max | 0.040 max | 1 max | 12-15 | 2 max | 0.030 max | 22-24 | Bal | 0.75 max | 0.75 max |
Property
| 0.2% Offset Yield Strength | Ultimate Tensile Strength | Elongation in 2” | Hardness | ||
| Psi(min) | Mpa | Psi(min) | Mpa | % | HBN (max) |
| 45,000 | 310 | 85,000 | 586 | 50 | 202 |
Application
Heating elements
Aircraft and jet engine parts
Heat exchangers
Carburizing annealing products
Sulfite liquor handling equipment
Kiln liners
Boiler baffles
Refinery and chemical processing equipment
Auto exhaust parts
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