Stainless Steel
Stainless Steel 309S (UNS S30908) — Composition, Properties & Supply
Stainless 309S (UNS S30908) is a 23Cr-13Ni austenitic heat-resistant grade with carbon ≤ 0.08%. It resists oxidation and retains strength below 1000 °C and is widely used for furnace parts, automotive exhaust manifolds and as a buttering layer when joining dissimilar steels (carbon to stainless).
What is the chemical composition of Stainless Steel 309S?
| Element | Symbol | Content (wt%) |
|---|---|---|
| Fe | Fe | Balance |
| Cr | Cr | 22.0–24.0 |
| Ni | Ni | 12.0–15.0 |
| Mn | Mn | ≤ 2.00 |
| Si | Si | ≤ 1.00 |
| C | C | ≤ 0.080 |
| P | P | ≤ 0.045 |
| S | S | ≤ 0.030 |
Values are typical specification limits. Actual heat analysis is reported on the EN 10204 3.1 mill test certificate supplied with each shipment.
What are the mechanical properties of Stainless Steel 309S?
| Property | Value | Note |
|---|---|---|
| Tensile strength | ≥ 515 MPa | Room temperature |
| Yield strength (0.2% offset) | ≥ 205 MPa | Room temperature |
| Elongation | ≥ 40 % | Gauge length 50 mm / 4D |
| Hardness | ≤ 217 HB | Brinell / Rockwell |
What are the physical properties of Stainless Steel 309S?
| Property | Value |
|---|---|
| Density | 7.98 g/cm³ |
| Melting range | 1398–1454 °C |
| Thermal conductivity | 15.6 W/m·K |
| Elastic modulus | 200 GPa |
| Maximum service temperature | 1000 °C (continuous oxidation) |
What are the key characteristics of Stainless Steel 309S?
- 23Cr-13Ni — oxidation resistant to about 1000 °C
- Common buttering layer for dissimilar steel welds (carbon to stainless)
- Good formability and weldability
- Better than 304/310 in sulphidising high-temperature atmospheres
Where is Stainless Steel 309S used?
- Automotive exhaust manifolds and catalyst housings
- Boiler burners and furnace structural parts
- Transition layer in carbon-to-stainless clad plate
- Annealing covers and heat-treat furnace internals
- Cement and glass industry heat-resistant parts
Which standards and specifications cover Stainless Steel 309S?
What product forms are available?
Frequently asked questions
Can 309S filler metal replace 304/316 welding wire?
Not as a direct replacement. 309S's high Cr/Ni tolerates the higher heat input of dissimilar joining (carbon steel to stainless or stainless to heat-resistant steel) and is the preferred buttering and transition layer. When used to weld 304 or 316 base metal, the deposit chemistry far exceeds the parent, producing high residual stress and a different CTE, and the cost is unjustified. For same-grade welds use 308L (for 304 base) or 316L (for 316 base).
Need Stainless Steel 309S bar, tube, plate or forgings?
Send the grade, dimensions, standard and quantity. We answer within 10 minutes on working days and quote within 24 hours, with EN 10204 3.1 certification.
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