AISI 309HCb Stainless Steel Plate | 309HCb China steel mill-Direct Supply
What is AISI 309HCb Stainless Steel Plate?
As a professional China steel mill-Direct Supply and stainless steel plate supplier, SHH STEEL is pleased to present AISI 309HCb Stainless Steel Plate.
AISI 309HCb is a specialized high-temperature austenitic stainless steel that combines two important enhancements to the basic 309 composition: controlled higher carbon content for improved high-temperature strength and creep resistance, and niobium (columbium) stabilization for superior resistance to intergranular corrosion after welding. It contains approximately 22–24% chromium and 12–15% nickel, providing excellent oxidation resistance at elevated temperatures.
This dual optimization makes AISI 309HCb particularly suitable for welded high-temperature equipment that operates under load for extended periods, such as furnace components, radiant tubes, heat-treatment fixtures, superheater parts and petrochemical process equipment in oxidizing atmospheres.
SHH STEEL supplies AISI 309HCb 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 309HCb in plate and sheet form across a practical range of thicknesses and surface finishes optimized for elevated-temperature service.
AISI 309HCb is frequently compared with a240 309s, a240 310s, a240 310h, a240 321, a240 347 and a240 304l when selecting materials for demanding 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 309HCb / UNS S30941 | 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 309HCb dual-certified to ASTM A240 / ASME SA240 when required by the project.
Chemical Composition
Typical Chemical Composition of AISI 309HCb:
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.04 – 0.10 |
| 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 |
| Niobium (Nb/Cb) | 10 × C min – 1.10 max |
| Nitrogen (N) | ≤ 0.10 |
| Iron (Fe) | Balance |
AISI 309HCb features two critical alloying controls: higher carbon (0.04–0.10%) for improved high-temperature strength and creep resistance, and intentional niobium addition for stabilization against intergranular corrosion. The niobium combines preferentially with carbon to form stable carbides, protecting the grain boundaries. Combined with high chromium and nickel, the grade delivers outstanding oxidation resistance. SHH STEEL carefully controls both carbon and the niobium-to-carbon ratio to ensure consistent performance.
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 309HCb retains higher strength than low-carbon 309S due to the controlled carbon content, while the niobium stabilization maintains corrosion resistance after welding. For even higher alloy content and oxidation resistance under load, a240 310h may be considered. SHH STEEL supplies material with consistent high-temperature mechanical 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 | Stabilization | High-Temp Strength | Oxidation Resistance | Weldability & IGC | Typical Preference |
|---|---|---|---|---|---|---|
| AISI 309S | ≤ 0.08 | Low carbon | Good | Very Good | Excellent | Welded high-temperature service |
| AISI 309H | 0.04–0.10 | None | Higher | Very Good | Moderate | High-temp strength (non-critical welding) |
| AISI 309HCb | 0.04–0.10 | Niobium | Higher | Very Good | Excellent | High-temp strength + stabilized welding |
| AISI 310S | ≤ 0.08 | Low carbon | Good | Excellent | Excellent | Severe high-temperature service |
| AISI 310H | 0.04–0.10 | None | Higher | Excellent | Good | Maximum high-temp strength + oxidation |
| AISI 347 | ≤ 0.08 | Niobium | Standard | Good | Excellent | Stabilized lower-temp welded service |
AISI 309HCb is selected when both improved high-temperature strength/creep resistance and excellent resistance to intergranular corrosion after welding are required. Compared with a240 309s, it offers higher strength at elevated temperature. For more severe oxidizing environments, SHH STEEL recommends a240 310s or a240 310h. Stabilized grades such as a240 321 or a240 347 are often considered for lower service temperatures.
Corrosion Resistance
AISI 309HCb 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 niobium stabilization ensures good resistance to intergranular corrosion after welding or exposure to the sensitization temperature range, even with the higher carbon content.
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 or a240 310h. In chloride-rich aqueous environments, a240 316l or a240 2205 should be considered.
Weldability
AISI 309HCb has excellent weldability due to niobium stabilization. Matching or appropriate niobium-bearing / 309-type filler metals are recommended. The stabilization effectively prevents intergranular corrosion in the heat-affected zone despite the higher carbon content, making post-weld annealing generally unnecessary for most applications.
SHH STEEL recommends proper welding procedures and post-weld cleaning to achieve optimum high-temperature strength and corrosion performance. This combination of elevated-temperature strength and as-welded corrosion resistance is the main advantage of AISI 309HCb.
Heat Treatment
AISI 309HCb is normally supplied in the solution-annealed condition by SHH STEEL.
Recommended solution annealing temperature range is 1040–1150°C (often toward the higher end), followed by rapid cooling. Proper annealing ensures that niobium is available for effective stabilization and optimizes both high-temperature strength and oxidation resistance. SHH STEEL controls heat treatment to ensure consistent quality for elevated-temperature service under load.
Surface Finishes
| Finish | Description | Typical Use / Keywords |
|---|---|---|
| No.1 | Hot-rolled, annealed and pickled | AISI 309HCb No.1 – most common for industrial high-temp plate |
| 2B | Cold-rolled, annealed, pickled, skin-passed | AISI 309HCb 2B – thinner plates |
| Special | Ground or custom finishes | AISI 309HCb Special – on request |
SHH STEEL regularly supplies AISI 309HCb in No.1 finish, which is the preferred condition for most high-temperature plate applications.
Tolerances
Dimensional tolerances for AISI 309HCb 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
| Grade / Designation | Standard / UNS | Notes |
|---|---|---|
| AISI 309HCb | — | — |
| UNS S30941 | — | Unified Numbering System |
| ASTM A240 Type 309HCb | ASTM A240 | When dual certified |
| Related high-C Nb-stabilized 309 | EN / JIS / GB | Approximate national equivalents |
Related grades for comparison include a240 309s, a240 310s, a240 310h, a240 321, a240 347 and a240 304l.
Applications
AISI 309HCb is selected for welded high-temperature applications requiring both improved strength/creep resistance and resistance to intergranular corrosion. Typical applications of AISI 309HCb include:
| Industry / Sector | Typical Components / Equipment (with keywords) |
|---|---|
| Heat Treatment & Furnaces | AISI 309HCb furnace components, radiant tubes, fixtures, trays |
| Industrial Heating | AISI 309HCb kiln parts, muffles, supports and retorts |
| Power Generation | AISI 309HCb high-temperature ducting and load-bearing parts |
| Petrochemical & Refining | AISI 309HCb furnace linings, process equipment under load |
| Chemical Processing | AISI 309HCb high-temperature vessels and welded components |
| General High-Temperature Service | AISI 309HCb equipment requiring strength + oxidation resistance |
SHH STEEL supplies AISI 309HCb for these demanding elevated-temperature 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 309HCb 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)
- High-carbon niobium-stabilized material optimized for high-temperature strength and welded service
- Flexible dimensions and surface finishes (including AISI 309HCb No.1 and AISI 309HCb 2B)
- Technical support for selection among 309S, 309H, 309HCb, 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 309HCb over AISI 309S or 309H?AISI 309HCb combines the higher carbon of 309H (for improved high-temperature strength and creep resistance) with niobium stabilization (for excellent resistance to intergranular corrosion after welding). SHH STEEL recommends 309HCb when both properties are required.
- How does AISI 309HCb compare with AISI 310H?AISI 310H has higher chromium and nickel contents and offers superior oxidation resistance together with high-temperature strength. SHH STEEL recommends 310H for more severe high-temperature service
- What is the density of AISI 309HCb?Approximately 7.90 g/cm³. SHH STEEL provides material certificates confirming physical and mechanical properties.
Conclusion
AISI 309HCb Stainless Steel Plate is a high-carbon, niobium-stabilized version of the heat-resisting 309 grade. It successfully combines improved high-temperature strength and creep resistance with excellent oxidation resistance and superior resistance to intergranular corrosion after welding. It is an outstanding choice for demanding welded furnace components, radiant tubes, heat-treatment equipment and petrochemical process equipment operating under load in oxidizing atmospheres.
As a professional China steel mill-Direct Supply, SHH STEEL provides high-quality AISI 309HCb Stainless Steel Plate with competitive pricing, full certification and complete technical support.
Contact SHH STEEL today for stock availability, surface finish options (including AISI 309HCb No.1 and AISI 309HCb 2B), or a competitive quotation.
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