AISI 309S Stainless Steel Plate | 309S China steel mill-Direct Supply
What is AISI 309S Stainless Steel Plate?
As a professional China steel mill-Direct Supply and stainless steel plate supplier, SHH STEEL is pleased to present AISI 309S Stainless Steel Plate.
AISI 309S (UNS S30908) is the low-carbon variant of the heat-resisting austenitic stainless steel AISI 309. It contains approximately 22–24% chromium and 12–15% nickel, providing excellent resistance to oxidation and scaling at elevated temperatures. The carbon content is limited to a maximum of 0.08%, which significantly improves resistance to intergranular corrosion after welding compared with standard 309.
This combination makes AISI 309S the preferred choice for welded high-temperature equipment such as furnace components, radiant tubes, heat-treatment fixtures, kiln parts and petrochemical process equipment operating in oxidizing atmospheres.
SHH STEEL supplies AISI 309S as true China steel mill-Direct Supply, sourcing directly from major Chinese stainless steel mills. This model delivers competitive mill pricing, consistent quality, complete heat traceability and reliable delivery. SHH STEEL offers AISI 309S in plate and sheet form across a practical range of thicknesses and surface finishes suitable for elevated-temperature service.
AISI 309S is frequently compared with a240 309, a240 310s, a240 310h, a240 304, a240 304l and a240 321 when selecting materials for high-temperature welded applications. SHH STEEL provides technical support to help customers choose the most appropriate grade.
Material Specification
| Specification Element | Requirement | SHH STEEL Compliance |
|---|---|---|
| Grade | AISI 309S / UNS S30908 | Confirmed |
| Related Standards | ASTM A240, ASME SA240, related high-temperature specs | Available |
| Product Form | Plate, Sheet | Available |
| Delivery Condition | Solution Annealed | Standard |
| Thickness Range | 1 mm – 80 mm (thicker available on request) | Custom sizes supported |
| Width | Up to 2000–3000 mm | Available |
| Length | Up to 12000 mm or cut-to-length | Available |
| Surface Finish | No.1, 2B, and others on request | Available |
| Certification | EN 10204 3.1 / Mill Test Certificate | Available |
SHH STEEL can supply AISI 309S dual-certified to ASTM A240 / ASME SA240 when required by the project.
Chemical Composition
Typical Chemical Composition of AISI 309S (UNS S30908):
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.08 |
| Silicon (Si) | ≤ 1.00 |
| Manganese (Mn) | ≤ 2.00 |
| Phosphorus (P) | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 |
| Chromium (Cr) | 22.00 – 24.00 |
| Nickel (Ni) | 12.00 – 15.00 |
| Nitrogen (N) | ≤ 0.10 |
| Iron (Fe) | Balance |
The low carbon content (≤ 0.08%) is the key difference from standard AISI 309. Combined with high chromium (22–24%) and nickel (12–15%), it delivers excellent high-temperature oxidation resistance together with improved weldability and resistance to intergranular corrosion. SHH STEEL carefully controls composition to ensure reliable performance in welded high-temperature service.
Mechanical Properties
Annealed Condition (typical values)
| Property | Value |
|---|---|
| Tensile Strength | ≥ 515 MPa (75 ksi) |
| Yield Strength (0.2%) | ≥ 205 MPa (30 ksi) |
| Elongation (in 50 mm) | ≥ 40% |
| Hardness | ≤ 217 HB |
At elevated temperatures, AISI 309S retains useful strength and outstanding oxidation resistance. For applications requiring higher creep strength, related grades such as a240 310h may be considered. SHH STEEL supplies material with consistent high-temperature properties.
Physical Properties Density is approximately 7.90 g/cm³. The grade is non-magnetic in the annealed condition. Melting range is approximately 1400–1450°C.
Material Comparison
| Grade | Carbon | Cr (%) | Ni (%) | Weldability & IGC | Oxidation Resistance | Typical Preference |
|---|---|---|---|---|---|---|
| AISI 309 | ≤ 0.20 | 22–24 | 12–15 | Moderate | Very Good | Non-welded high-temp service |
| AISI 309S | ≤ 0.08 | 22–24 | 12–15 | Excellent | Very Good | Welded high-temperature service |
| AISI 310S | ≤ 0.08 | 24–26 | 19–22 | Excellent | Excellent | Severe high-temperature service |
| AISI 310H | 0.04–0.10 | 24–26 | 19–22 | Good | Excellent | High-temp strength + oxidation |
| AISI 304 | ≤ 0.08 | 18–20 | 8–10.5 | Good | Good | General purpose |
| AISI 321 | ≤ 0.08 | 17–19 | 9–12 | Good (stabilized) | Good | Stabilized high-temp welded service |
AISI 309S is the preferred grade for welded constructions requiring excellent high-temperature oxidation resistance. Compared with standard 309, the low carbon content provides superior resistance to intergranular corrosion after welding. For more severe high-temperature service, SHH STEEL recommends a240 310s or a240 310h. When stabilization against intergranular corrosion is the priority at moderately high temperatures, a240 321 is often selected.
Corrosion Resistance
AISI 309S provides excellent resistance to oxidation and scaling in air and oxidizing atmospheres at elevated temperatures up to approximately 1000–1100°C in continuous service (depending on conditions). The low carbon content also gives it good resistance to intergranular corrosion after welding.
At room temperature it offers good resistance to atmospheric corrosion and many mild chemical environments. In sulfur-containing or highly carburizing atmospheres, performance may be limited. For the most demanding high-temperature oxidizing service, SHH STEEL recommends a240 310s. In chloride-rich aqueous environments, a240 316l or a240 2205 should be considered.
Weldability
AISI 309S has excellent weldability due to its low carbon content. Matching or 309L filler metals are commonly used. The reduced carbon minimizes the risk of intergranular corrosion in the as-welded condition, making post-weld annealing generally unnecessary for most applications.
SHH STEEL recommends proper welding procedures and post-weld cleaning to achieve optimum high-temperature and corrosion performance. This outstanding as-welded behavior is the main reason AISI 309S is preferred over standard 309 for fabricated high-temperature equipment.
Heat Treatment
AISI 309S is normally supplied in the solution-annealed condition by SHH STEEL.
Recommended solution annealing temperature range is 1040–1150°C, followed by rapid cooling. Proper annealing optimizes both room-temperature ductility and high-temperature oxidation resistance. SHH STEEL controls heat treatment to ensure consistent quality for elevated-temperature service.
Surface Finishes
| Finish | Description | Typical Use / Keywords |
|---|---|---|
| No.1 | Hot-rolled, annealed and pickled | AISI 309S No.1 – most common for industrial high-temp plate |
| 2B | Cold-rolled, annealed, pickled, skin-passed | AISI 309S 2B – thinner plates |
| Special | Ground or custom finishes | AISI 309S Special – on request |
SHH STEEL regularly supplies AISI 309S in No.1 finish, which is the preferred condition for most high-temperature plate applications.
Tolerances
Dimensional tolerances for AISI 309S Stainless Steel Plate supplied by SHH STEEL generally conform to ASTM A480 practices.
Typical available size range is thickness 1 mm – 80 mm, width up to 2000–3000 mm, and length up to 12000 mm or cut-to-length. SHH STEEL provides precise dimensional control and can support tighter tolerances when required.
Equivalent Material Grades
Applications
AISI 309S is selected for welded constructions requiring excellent high-temperature oxidation resistance. Typical applications of AISI 309S include:
| Industry / Sector | Typical Components / Equipment (with keywords) |
|---|---|
| Heat Treatment & Furnaces | AISI 309S furnace components, radiant tubes, fixtures, trays |
| Industrial Heating | AISI 309S kiln parts, muffles, supports and retorts |
| Power Generation | AISI 309S high-temperature ducting and structural parts |
| Petrochemical & Refining | AISI 309S furnace linings, process equipment and welded parts |
| Chemical Processing | AISI 309S high-temperature vessels and welded components |
| General High-Temperature Service | AISI 309S equipment operating in oxidizing atmospheres |
SHH STEEL supplies AISI 309S for these elevated-temperature welded applications with consistent quality. For related industry solutions, see our energy industry, petrochemical industry and equipment manufacturing pages. Supporting services include steel cutting services and steel welding services.
Why Choose SHH STEEL
SHH STEEL is a China steel mill-Direct Supply specializing in stainless steel plate and sheet. By working directly with major Chinese stainless steel mills, SHH STEEL supplies AISI 309S with the following advantages:
- Genuine China steel mill-Direct Supply pricing
- Consistent quality and complete heat traceability
- Full Mill Test Certificates (EN 10204 3.1)
- Low-carbon material optimized for welded high-temperature service
- Flexible dimensions and surface finishes (including AISI 309S No.1 and AISI 309S 2B)
- Technical support for selection among 309, 309S, 310S, 310H and related grades
- Value-added services including steel cutting services, steel welding services and worldwide shipping service
For more information about our company and full product range, please visit China steel Mill Agent-SHH STEEL.
FAQ
- What is the main advantage of AISI 309S over standard AISI 309?The low carbon content (≤ 0.08%) provides significantly better resistance to intergranular corrosion after welding while retaining excellent high-temperature oxidation resistance. SHH STEEL recommends 309S for most welded high-temperature applications.
- How does AISI 309S compare with AISI 310S?AISI 310S has higher chromium and nickel contents and offers superior oxidation resistance for more severe high-temperature service. SHH STEEL recommends 310S when maximum performance is required.
- What is the density of AISI 309S?Approximately 7.90 g/cm³. SHH STEEL provides material certificates confirming physical and mechanical properties.
Conclusion
AISI 309S Stainless Steel Plate is the low-carbon version of the high-chromium, high-nickel heat-resisting grade 309. It combines excellent high-temperature oxidation resistance with improved weldability and superior resistance to intergranular corrosion, making it the preferred material for welded furnace components, radiant tubes, heat-treatment equipment and petrochemical process equipment operating in oxidizing atmospheres.
As a professional China steel mill-Direct Supply, SHH STEEL provides high-quality AISI 309S Stainless Steel Plate with competitive pricing, full certification and complete technical support.
Contact SHH STEEL today for stock availability, surface finish options (including AISI 309S No.1 and AISI 309S 2B), or a competitive quotation.
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