On this page 12 sections
What is SS 309S Stainless Steel?
Quick answer
- Definition
- SS 309S is the low-carbon (0.08% max) version of SS 309, the standard flat-product grade for heat-resisting service up to about 1,000 °C.
- Family
- Heat-resisting austenitic stainless steel
- Key strength
- Low carbon for better weldability
- Main forms
- Pipes, Tubes, Plates, Sheets, Coils, Bars
- Typical uses
- Furnace linings, doors and dampers; Annealing covers and heat-treatment boxes; Kiln and cement-plant parts
SS 309S has the same 22–24% chromium and 12–15% nickel as SS 309 but limits carbon to 0.08%. That improves weldability and reduces carbide precipitation during fabrication. It's the grade most often supplied as plate, sheet and coil for furnace and heat-treatment equipment.
SS 309S offers a step up in oxidation resistance from SS 304 and SS 321 at lower cost than SS 310S. Where temperatures are higher, or cyclic heating is severe, SS 310S or 253 MA is usually considered.
Key characteristics
- Low carbon for better weldability
- Oxidation resistance to about 1,000 °C
- Standard grade for furnace plate and sheet
- More economical than SS 310S
What are the specifications and equivalents of SS 309S?
| Product form | Specification / designation | Product page |
|---|---|---|
| Pipes | ASTM A312 / ASME SA312 TP309S (seamless & welded); A358 EFW | SS 309S pipes → |
| Tubes | ASTM A213 TP309S (seamless); A249 / A269 TP309S (welded) | SS 309S tubes → |
| Plates | ASTM A240 / ASME SA240 309S | SS 309S plates → |
| Sheets | ASTM A240 / ASME SA240 309S | SS 309S sheets → |
| Coils | ASTM A240 / ASME SA240 309S | SS 309S coils → |
| Bars | ASTM A276 / A479 309S | SS 309S bars → |
| Fittings | ASTM A403 WP309 / to order | SS 309S fittings → |
| Flanges | ASTM A182 F309H / to order | SS 309S flanges → |
UNS S30908 · EN 1.4833 (cross-reference; limits are similar but not identical)
What is the chemical composition of SS 309S?
| Element | Limit (%) |
|---|---|
| C | 0.08 max |
| Mn | 2.00 max |
| P | 0.045 max |
| S | 0.030 max |
| Si | 0.75 max |
| Cr | 22.0 – 24.0 |
| Ni | 12.0 – 15.0 |
What are the mechanical properties of SS 309S?
| Property | Value |
|---|---|
| Tensile strength | 515 MPa (75 ksi) |
| Yield strength (0.2% offset) | 205 MPa (30 ksi) |
| Elongation | 40% |
| Hardness | 217 HBW / 95 HRB |
Physical properties and service temperature
| Property | Value |
|---|---|
| Density (typical) | 7.9 g/cm³ (7900 kg/m³) |
| Magnetism | Non-magnetic when annealed. |
| Heat treatment | Solution annealed. High-temperature exposure may form sigma phase, which reduces room-temperature toughness. |
| Service temperature | Up to about 1,000 °C continuous in oxidising atmospheres (indicative). |
How is SS 309S welded and fabricated?
Weldable with matching high-alloy fillers; keep heat input moderate to limit hot cracking.
Always follow a qualified welding procedure (for example ASME Section IX) and the filler-metal recommendations for SS 309S. Verify incoming material by PMI and check the mill test certificate against the specification.
Which SS 309S products do we supply?
SS 309S Stainless Steel is available in 8 product forms, from ready stock or mill-sourced to your specification, with EN 10204 3.1 mill test certificates (3.2 with third-party inspection on request).
SS 309S PipesASTM A312 TP309SSpecification & sizes
How it's madeSeamless pipe is pierced from a solid billet and hot-finished or cold-drawn. Welded pipe is formed from strip or plate and welded longitudinally (ERW/HFW, TIG/plasma, EFW, LSAW) or spirally (SAWH). Stainless and nickel-alloy pipe is then solution annealed and pickled. Carbon and alloy steel pipe is supplied as-rolled, normalised, or normalised and tempered according to the specification.
- Specification
- ASTM A312 / ASME SA312 TP309S (seamless & welded); A358 EFW
- Size range
- NPS ⅛" to 48" and larger (DN 6 – DN 1200+), schedules 5S to XXS, single random, double random and cut lengths
- Finish
- Annealed & pickled, bright annealed, mill finish, black, varnished, galvanised or 3LPE / FBE coated (by material)
- Ends
- Plain end (PE), bevelled end (BE, ASME B16.25), threaded (NPT / BSP), grooved
Testing & documents
- Chemical and mechanical (tension, flattening, flare/bend) tests
- Hydrostatic test or non-destructive electric test (UT/ET) on each length
- Dimensional and visual inspection
- Intergranular corrosion (stainless), impact (low-temperature), hardness (sour service) when specified
- PMI and third-party inspection on request
- EN 10204 3.1 certificate; 3.2 with third-party inspection
SS 309S TubesASTM A213 TP309SSpecification & sizes
How it's madeSeamless tubes are hot-extruded or pierced and then cold-drawn or pilgered to size. Welded tubes are formed from strip, welded (TIG/laser/HF), bead-worked and drawn or sized. Heat-exchanger and boiler tubes are annealed after final forming, and U-tubes are bent and stress-relieved as required.
- Specification
- ASTM A213 TP309S (seamless); A249 / A269 TP309S (welded)
- Size range
- OD 3 mm to about 127 mm (¼" to 5") typical, wall 0.5 mm to 12 mm; BWG or mm; straight lengths up to about 30 m, U-bent to drawing
- Finish
- Annealed & pickled, bright annealed (BA), polished (sanitary), cold-drawn
- Ends
- Plain square-cut, deburred; U-bends with stress-relieved bends on request
Testing & documents
- Eddy-current and/or ultrasonic testing on each tube
- Hydrostatic or pneumatic test
- Flattening, flaring and flange tests
- Grain size (H grades), IGC and hardness when specified
- Surface roughness (Ra) for sanitary and instrumentation tube
- EN 10204 3.1 certificate; 3.2 with third-party inspection
SS 309S PlatesASTM A240 309SSpecification & sizes
How it's madeSlabs are hot-rolled on a reversing plate mill (or a Steckel/hot-strip mill for thinner plate), then heat treated (annealed, normalised, or quenched and tempered, depending on material), descaled and pickled or shot-blasted. Plates are cut to size by plasma, oxy-fuel, waterjet or shearing.
- Specification
- ASTM A240 / ASME SA240 309S
- Size range
- Thickness about 3 – 150 mm (and heavier on request), widths 1,000 – 3,000 mm, lengths 2,000 – 12,000 mm; cut-to-size and profile-cut parts
- Finish
- No.1 (hot-rolled, annealed and pickled) for stainless; shot-blasted, mill scale or primed for carbon steel
- Ends
- Mill edge, sheared, plasma or waterjet cut, profile cut to drawing
Testing & documents
- Chemical analysis and tensile tests (per plate or heat)
- Impact tests for low-temperature and pressure-vessel plates
- Ultrasonic testing (e.g. ASTM A435 / A578) when specified
- IGC, HIC and simulated PWHT tests as required
- Flatness and dimensional inspection
- EN 10204 3.1 certificate; 3.2 with third-party inspection
SS 309S SheetsASTM A240 309SSpecification & sizes
How it's madeHot-rolled coil is cold-rolled to final thickness, then annealed and pickled (2B/2D) or bright annealed (BA), temper-passed, and polished or textured as needed. Coils are then levelled and cut into sheets.
- Specification
- ASTM A240 / ASME SA240 309S
- Size range
- Thickness about 0.3 – 6 mm, standard sizes 1,000 × 2,000, 1,219 × 2,438 (4 × 8 ft), 1,250 × 2,500 and 1,500 × 3,000 mm; custom cut lengths
- Finish
- 2B, 2D, BA, No.4 (brushed), HL (hairline), No.8 (mirror), embossed, PVC or laser-film protected
- Ends
- Sheared or slit edges; laser-cut blanks on request
Testing & documents
- Chemical and mechanical tests
- Surface and finish inspection
- Thickness and flatness checks
- Hardness and bend tests as specified
- EN 10204 3.1 certificate; 3.2 with third-party inspection
SS 309S CoilsASTM A240 309SSpecification & sizes
How it's madeHot-rolled coil (HRC) comes from the hot-strip mill. Cold-rolled coil (CRC) is further reduced on a cold mill, then annealed and pickled or bright annealed, and skin-passed. Slitting lines cut master coils into narrow strips to the width you order.
- Specification
- ASTM A240 / ASME SA240 309S
- Size range
- Thickness about 0.3 – 12 mm; widths from narrow slit strip (about 10 mm) to 1,250 / 1,500 / 2,000 mm; coil ID 508 / 610 mm; coil weights to order
- Finish
- No.1 (hot-rolled, annealed, pickled), 2B, 2D, BA, No.4 for stainless; HR black, pickled & oiled, CR for carbon steel
- Ends
- Mill edge or slit edge
Testing & documents
- Chemical and mechanical tests
- Thickness profile and surface inspection
- Hardness and bend tests
- EN 10204 3.1 certificate; 3.2 with third-party inspection
SS 309S BarsASTM A276 / A479 309SSpecification & sizes
How it's madeBillets are hot-rolled or forged to size, then heat treated (annealed, solution treated, or quenched and tempered) and finished by descaling, peeling, turning, cold-drawing or centreless grinding for bright bar with tight tolerance.
- Specification
- ASTM A276 / A479 309S
- Size range
- Round bars about 3 – 500 mm diameter; hex 6 – 100 mm A/F; square and flat sections to order; lengths 3 – 6 m random or cut to size
- Finish
- Black (hot-rolled), peeled, bright drawn, centreless ground and polished (h9 / h11 tolerance)
- Ends
- Saw-cut, chamfered on request
Testing & documents
- Chemical and mechanical tests
- Ultrasonic testing for internal soundness
- Hardness, IGC and impact tests as specified
- Straightness and tolerance checks
- EN 10204 3.1 certificate; 3.2 with third-party inspection
SS 309S FittingsASTM A403 WP309 / to orderSpecification & sizes
How it's madeButt-weld fittings are formed from seamless or welded pipe or plate by hot or cold forming (mandrel bending, hydraulic bulging, pressing), then heat treated, bevelled and finished. Socket-weld and threaded fittings are machined from forgings or bar.
- Specification
- ASTM A403 WP309 / to order
- Size range
- Butt-weld ½" – 48" (larger fabricated to order) in schedules matching the pipe; socket-weld and threaded ⅛" – 4" in Class 2000, 3000, 6000 and 9000
- Finish
- Annealed & pickled, shot-blasted, black painted or galvanised (by material)
- Ends
- Bevelled (butt-weld), socket-weld, threaded NPT/BSP
Testing & documents
- Chemical and mechanical tests of the starting material
- Dimensional inspection to B16.9 / B16.11
- Radiography of welded fittings (seamed WPW/WX)
- Hardness, IGC and impact tests as specified
- EN 10204 3.1 certificate; 3.2 with third-party inspection
SS 309S FlangesASTM A182 F309H / to orderSpecification & sizes
How it's madeFlanges are forged from billets (or cut from plate for some blind and plate flanges), heat treated to the material specification, and machined: bore, face, raised face or ring groove, bolt holes and hub bevel.
- Specification
- ASTM A182 F309H / to order
- Size range
- NPS ½" – 24" (B16.5), 26" – 60" (B16.47 Series A/B); Class 150, 300, 600, 900, 1500, 2500; EN 1092-1 PN 6 – PN 100 on request
- Finish
- Raised face (RF), flat face (FF) or ring-type joint (RTJ); serrated spiral or concentric face finish (typically 3.2 – 6.3 µm Ra)
- Ends
- Weld-neck bevel matched to pipe schedule; socket bore; threaded
Testing & documents
- Chemical and mechanical tests of the forging
- Dimensional inspection to ASME B16.5 / B16.47
- Hardness, impact and IGC tests as specified
- Ultrasonic testing of forgings on request
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Where is SS 309S used?
Typical applications
- Furnace linings, doors and dampers
- Annealing covers and heat-treatment boxes
- Kiln and cement-plant parts
- Thermal-oxidiser components
- Exhaust and flue-gas ducting
What should you specify when buying SS 309S?
- Grade and specification, e.g. ASTM A312 TP309S
- Product form, size and tolerance
- Heat treatment / condition and surface finish
- Quantity, delivery location and required date
- Tests: PMI, hydro/NDT, IGC, impact or hardness as required
- Certificate type (EN 10204 3.1 / 3.2) and third-party inspection
See our RFQ checklist guide and what drives metal prices.
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Frequently asked questions
What is the difference between SS 309 and SS 309S?
Only carbon: SS 309 allows up to 0.20%, SS 309S up to 0.08%. Flat products are usually supplied as SS 309S or dual-certified SS 309/309S.
SS 309S or SS 310S: which is better for furnaces?
SS 310S handles higher temperatures and more severe cycling. SS 309S is more economical for moderately high temperatures.
What is SS 309S used for?
Furnace linings, doors and dampers, Annealing covers and heat-treatment boxes, Kiln and cement-plant parts, Thermal-oxidiser components. It's used across Cement, Heavy Engineering, Power Generation, Petrochemical & Refining.
What is the UNS number of SS 309S?
SS 309S is designated UNS S30908; the closest EN cross-reference is 1.4833.
Which product forms is SS 309S available in?
Pipes, Tubes, Plates, Sheets, Coils, Bars, Fittings, Flanges, to ASTM A312 TP309S, ASTM A213 TP309S, ASTM A240 309S and related specifications.
What is the density of SS 309S?
About 7.9 g/cm³ (7900 kg/m³), used for weight calculations.
Is SS 309S magnetic?
Non-magnetic when annealed.
What temperature can SS 309S withstand?
Up to about 1,000 °C continuous in oxidising atmospheres (indicative).