AISI 347H Stainless Steel Plate | 347H China steel mill-Direct Supply
What is AISI 347H Stainless Steel?
As a professional China steel mill-Direct Supply and stainless steel plate supplier, SHH STEEL is pleased to present AISI 347H Stainless Steel Plate.
AISI 347H (UNS S34709) is the high-carbon variant of the niobium-stabilized austenitic stainless steel 347. It contains approximately 17–19% chromium and 9–13% nickel, with carbon intentionally controlled in the range of 0.04–0.10% and niobium added for stabilization. The higher carbon content significantly improves high-temperature strength and creep resistance compared with standard 347, while the niobium stabilization maintains excellent resistance to intergranular corrosion after welding or exposure to the sensitization temperature range.
In addition to the controlled carbon content, AISI 347H is typically produced with a controlled grain size (ASTM No. 6 or coarser) to further enhance long-term creep performance. The grade is particularly suitable for long-term elevated-temperature service under load, such as heat exchangers, furnace components, superheater parts, expansion joints and chemical process equipment operating in the 500–900°C range.
SHH STEEL supplies AISI 347H 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 347H in plate and sheet form across a practical range of thicknesses and surface finishes optimized for high-temperature service.
AISI 347H is frequently compared with a240 347, a240 321, a240 321h, a240 304, a240 316ti and a240 310h when selecting materials for elevated-temperature applications. SHH STEEL provides technical support to help customers choose the most appropriate grade.
Material Specification
| Specification Element | Requirement | SHH STEEL Compliance |
|---|---|---|
| Grade | AISI 347H / UNS S34709 | 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 347H dual-certified to ASTM A240 / ASME SA240 when required by the project.
Chemical Composition
Typical Chemical Composition of AISI 347H (UNS S34709):
| 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) | 17.00 – 19.00 |
| Nickel (Ni) | 9.00 – 13.00 |
| Niobium (Nb/Cb) | 8 × C min – 1.00 max |
| Nitrogen (N) | ≤ 0.10 |
| Iron (Fe) | Balance |
The controlled higher carbon content (0.04–0.10%) combined with niobium stabilization is the defining feature of AISI 347H. Higher carbon improves high-temperature strength and creep resistance, while niobium prevents intergranular corrosion. SHH STEEL carefully controls both carbon and the niobium-to-carbon ratio to meet the requirements of elevated-temperature service under load.
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 |
| Grain Size | ASTM No. 6 or coarser |
For H grades such as AISI 347H, ASTM A240 requires a controlled grain size of ASTM No. 6 or coarser. This coarser grain structure is essential for optimizing long-term creep resistance at elevated temperatures. SHH STEEL ensures that AISI 347H plates meet the specified grain size requirements in addition to the mechanical property limits.
At elevated temperatures, AISI 347H retains higher strength than standard 347 due to the controlled carbon content and appropriate grain size. SHH STEEL supplies material with consistent high-temperature mechanical properties and verified grain size.
Physical Properties
Density is approximately 7.90–8.00 g/cm³. The grade is non-magnetic in the annealed condition. Melting range is approximately 1400–1425°C.
Material Comparison
| Grade | Carbon | Stabilization | Grain Size Control | High-Temp Strength | Intergranular Corrosion Resistance | Typical Preference |
|---|---|---|---|---|---|---|
| AISI 347 | ≤ 0.08 | Niobium | Not mandatory | Good | Excellent | Stabilized high-temp welded service |
| AISI 347H | 0.04–0.10 | Niobium | ASTM No. 6 or coarser | Higher | Excellent | High-temp strength + Nb stabilization |
| AISI 321 | ≤ 0.08 | Titanium | Not mandatory | Good | Excellent | Ti-stabilized high-temp service |
| AISI 321H | 0.04–0.10 | Titanium | ASTM No. 6 or coarser | Higher | Excellent | High-temp strength + Ti stabilization |
| AISI 304H | 0.04–0.10 | None | ASTM No. 6 or coarser | Higher | Moderate | High-temp strength (no stabilization) |
| AISI 310H | 0.04–0.10 | None | ASTM No. 6 or coarser | Higher | Moderate | Severe high-temp oxidation |
AISI 347H is selected when improved high-temperature strength and creep resistance are required in addition to niobium stabilization against intergranular corrosion. Compared with standard a240 347, it offers higher strength at elevated temperature. For titanium stabilization, SHH STEEL also supplies a240 321 and related H grades. For severe oxidizing service, a240 310h may be preferred.
Corrosion Resistance
AISI 347H offers good resistance to atmospheric corrosion, fresh water and many mild to moderate chemical environments, similar to standard 347. The niobium stabilization provides excellent resistance to intergranular corrosion after welding or exposure to the sensitization temperature range, even with the higher carbon content.
In chloride-containing environments, AISI 347H can be susceptible to pitting and stress corrosion cracking. For improved pitting resistance, SHH STEEL recommends a240 316l or a240 316ti. For severe high-temperature oxidizing service, a240 310s or a240 310h is preferred.
Weldability
AISI 347H can be welded by standard fusion welding methods. Matching or 347H-type filler metals are preferred to maintain high-temperature strength and stabilization in the weld metal. Due to the higher carbon content, proper welding procedures are important.
The niobium stabilization helps protect against intergranular corrosion in the heat-affected zone. Post-weld solution annealing may be recommended for critical high-temperature service. SHH STEEL recommends controlled welding parameters and post-weld cleaning for optimum performance.
Heat Treatment
AISI 347H is normally supplied in the solution-annealed condition by SHH STEEL.
Recommended solution annealing temperature range is 1050–1150°C (often toward the higher end), followed by rapid cooling. Proper annealing is important to dissolve carbides, achieve the required grain size, ensure effective niobium stabilization, and optimize both room-temperature and elevated-temperature properties. SHH STEEL controls heat treatment to ensure consistent performance and compliance with grain size requirements for high-temperature applications under load.
Surface Finishes
| Finish | Description | Typical Use / Keywords |
|---|---|---|
| No.1 | Hot-rolled, annealed and pickled | AISI 347H No.1 – most common for industrial high-temp plate |
| 2B | Cold-rolled, annealed, pickled, skin-passed | AISI 347H 2B – thinner plates |
| Special | Ground or custom finishes | AISI 347H Special – on request |
SHH STEEL regularly supplies AISI 347H in No.1 finish, which is the preferred condition for most high-temperature plate applications.
Tolerances
Dimensional tolerances for AISI 347H 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 / Region | Notes |
|---|---|---|
| AISI 347H | — | — |
| UNS S34709 | Unified Numbering System | — |
| ASTM A240 Type 347H | ASTM A240 | When dual certified |
| 1.4550 related (high C) | EN (Europe) | Closest European grades |
| SUS347 related | JIS (Japan) | Japanese related grades |
| 07Cr18Ni11Nb related | GB/T (China) | Chinese related high-C grades |
| Related 347 / 321H / 321 | Multiple | Standard / Ti-stabilized variants |
Related grades for comparison include a240 347, a240 321, a240 304, a240 316ti, a240 316l and a240 310h.
Applications
AISI 347H is selected for applications requiring both improved high-temperature strength/creep resistance and resistance to intergranular corrosion. Typical applications of AISI 347H include:
| Industry / Sector | Typical Components / Equipment (with keywords) |
|---|---|
| Heat Exchangers & Boilers | AISI 347H heat exchanger components, tubesheets and shells |
| Furnace & Heat Treatment | AISI 347H furnace components, fixtures and supports |
| Power Generation | AISI 347H high-temperature ducting and load-bearing parts |
| Chemical & Process Industry | AISI 347H process equipment operating at elevated temperature |
| Expansion Joints & Bellows | AISI 347H expansion joints requiring strength + stabilization |
| Exhaust Systems | AISI 347H high-temperature exhaust components |
| General High-Temperature Service | AISI 347H equipment under load in the sensitization range |
SHH STEEL supplies AISI 347H for these elevated-temperature applications with consistent quality and verified grain size. 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 347H 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 with controlled grain size (ASTM No. 6 or coarser) for optimized creep resistance
- Flexible dimensions and surface finishes (including AISI 347H No.1 and AISI 347H 2B)
- Technical support for selection among 347, 347H, 321, 321H and high-temperature 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 347H over AISI 347?The controlled higher carbon content (0.04–0.10%) and required grain size of ASTM No. 6 or coarser provide improved high-temperature strength and better creep resistance, while retaining niobium stabilization. SHH STEEL recommends 347H when long-term strength under load at elevated temperature is important.
- Why is grain size controlled for AISI 347H?A coarser grain size (ASTM No. 6 or coarser) improves long-term creep resistance at high temperatures. SHH STEEL ensures compliance with this requirement for all AISI 347H plates.
- How does AISI 347H compare with AISI 321H?Both are high-carbon stabilized grades. 347H uses niobium, while 321H uses titanium. Performance is similar in many applications. SHH STEEL can supply both and help select the better option based on specific requirements.
- Is AISI 347H magnetic?Non-magnetic in the annealed condition. SHH STEEL supplies fully annealed material as standard.
- What is the density of AISI 347H?Approximately 7.90–8.00 g/cm³. SHH STEEL provides material certificates confirming physical and mechanical properties, including grain size.
- Can AISI 347H be used in chloride environments?It has limited resistance to pitting in chlorides. For better performance, SHH STEEL recommends molybdenum-bearing grades such as 316L or 316Ti.
- Does SHH STEEL supply dual-certified ASTM A240 / AISI 347H material?Yes, SHH STEEL commonly supplies dual-certified material upon request.
Conclusion
AISI 347H Stainless Steel Plate is the high-carbon, niobium-stabilized version of the classic 347 grade. It combines improved high-temperature strength and creep resistance (supported by controlled carbon content and grain size of ASTM No. 6 or coarser) with excellent resistance to intergranular corrosion after welding. It is an outstanding choice for heat exchangers, furnace components, expansion joints and other applications requiring long-term performance under load at elevated temperatures.
As a professional China steel mill-Direct Supply, SHH STEEL provides high-quality AISI 347H Stainless Steel Plate with competitive pricing, full certification, verified grain size and complete technical support.
Contact SHH STEEL today for stock availability, surface finish options (including AISI 347H No.1 and AISI 347H 2B), or a competitive quotation.
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