SS309 Stainless Steel
SS309 is a high-chromium, high-nickel austenitic stainless steel developed for elevated-temperature service, offering substantially better oxidation resistance than conventional 18-8 stainless steels.
SS309 Grade Information
SS309, commonly designated AISI Type 309, is an austenitic chromium-nickel stainless steel with higher chromium and nickel contents than SS304. The increased alloy content provides improved resistance to oxidation and scaling at elevated temperatures.
For Spiral Wound Gaskets, SS309 may be considered for metallic winding or compatible ring components where elevated-temperature oxidation resistance is required and the alloy is chemically compatible with the process medium.
| Material specification | ASTM A240 |
|---|---|
| Specified grade / UNS | 309 S30900 |
SS309 Stainless Steel Chemical Composition
ASTM A240 · Grade-specific requirements
| Element / requirement | Value |
|---|---|
| C % | ≤0.20 |
| Mn % | ≤2.00 |
| P % | ≤0.045 |
| S % | ≤0.030 |
| Si % | ≤1.00 |
| Cr % | 22.0–24.0 |
| Ni % | 12.0–15.0 |
| Mo % | — |
| N % | — |
| Cu % | — |
| Other elements | — |
SS309 Stainless Steel Mechanical Properties
ASTM A240 · Grade-specific requirements
| Tensile min (MPa) | Yield min (MPa) | Elongation min (%) | Hardness max |
|---|---|---|---|
| 515 | 205 | 40 | ≤217 HBW |
ASTM A240 Grade Reference
309 S30900
The chemical and mechanical tables on this page use the ASTM A240 requirements for this grade, including the product conditions listed in the standard overview.
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