AISI 348H Stainless Steel Plate | 348H China steel mill-Direct Supply
What is AISI 348H Stainless Steel ?
As a professional China steel mill-Direct Supply and stainless steel plate supplier, SHH STEEL is pleased to present AISI 348H Stainless Steel Plate.
AISI 348H is the high-carbon variant of the niobium-stabilized, low-cobalt austenitic stainless steel 348. It contains approximately 17–19% chromium and 9–13% nickel, with carbon intentionally controlled in the range of 0.04–0.10%, niobium for stabilization, and restricted cobalt and tantalum content. The higher carbon content significantly improves high-temperature strength and creep resistance compared with standard 348, while niobium maintains excellent resistance to intergranular corrosion after welding or exposure to the sensitization temperature range.
In addition to the controlled carbon content, AISI 348H is typically produced with a controlled grain size (ASTM No. 6 or coarser) to further enhance long-term creep performance. The restricted cobalt content makes the grade suitable for nuclear applications where minimized induced radioactivity is required, combined with elevated-temperature strength.
SHH STEEL supplies AISI 348H 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 348H in plate and sheet form across a practical range of thicknesses and surface finishes optimized for high-temperature and specialized service.
AISI 348H is frequently compared with a240 348, a240 347, a240 347h, a240 321, a240 321h and a240 310h when selecting materials for elevated-temperature or nuclear-related applications. SHH STEEL provides technical support to help customers choose the most appropriate grade.
Material Specification
| Specification Element | Requirement | SHH STEEL Compliance |
|---|---|---|
| Grade | AISI 348H / UNS S34809 | Confirmed |
| Related Standards | ASTM A240, ASME SA240, related nuclear / high-temp 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 348H dual-certified to ASTM A240 / ASME SA240 when required by the project.
Chemical Composition
Typical Chemical Composition of AISI 348H:
| 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 |
| Cobalt (Co) | ≤ 0.20 (controlled) |
| Tantalum (Ta) | Restricted |
| Nitrogen (N) | ≤ 0.10 |
| Iron (Fe) | Balance |
AISI 348H features controlled higher carbon (0.04–0.10%) for improved high-temperature strength and creep resistance, niobium stabilization for intergranular corrosion resistance, and restricted cobalt/tantalum content for nuclear suitability. SHH STEEL carefully controls all these elements to meet the combined requirements of elevated-temperature performance and specialized compositional limits.
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 348H, a controlled grain size of ASTM No. 6 or coarser is required or preferred to optimize long-term creep resistance at elevated temperatures. SHH STEEL ensures that AISI 348H plates meet the specified grain size requirements in addition to the mechanical property limits.
At elevated temperatures, AISI 348H retains higher strength than standard 348 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 | Special Control | High-Temp Strength | Typical Preference |
|---|---|---|---|---|---|
| AISI 348 | ≤ 0.08 | Niobium | Low Co / Ta | Good | Nuclear + Nb-stabilized service |
| AISI 348H | 0.04–0.10 | Niobium | Low Co / Ta | Higher | Nuclear + high-temp strength |
| AISI 347 | ≤ 0.08 | Niobium | — | Good | Nb-stabilized high-temp service |
| AISI 347H | 0.04–0.10 | Niobium | — | Higher | High-temp strength + Nb stabilization |
| AISI 321H | 0.04–0.10 | Titanium | — | Higher | High-temp strength + Ti stabilization |
| AISI 310H | 0.04–0.10 | None | — | Higher | Severe high-temp oxidation |
AISI 348H is selected when improved high-temperature strength and creep resistance are required together with niobium stabilization and controlled low cobalt content. Compared with standard a240 348, it offers higher strength at elevated temperature. For general (non-nuclear) high-temperature stabilized service, SHH STEEL also supplies a240 347 and a240 347h.
Corrosion Resistance
AISI 348H offers good resistance to atmospheric corrosion, fresh water and many mild to moderate chemical environments, similar to standard 348 and 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 348H 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 348H can be welded by standard fusion welding methods. Matching or 347H/348H-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 or nuclear service. SHH STEEL recommends controlled welding parameters and post-weld cleaning for optimum performance.
Heat Treatment
AISI 348H 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.
Surface Finishes
| Finish | Description | Typical Use / Keywords |
|---|---|---|
| No.1 | Hot-rolled, annealed and pickled | AISI 348H No.1 – most common for industrial high-temp plate |
| 2B | Cold-rolled, annealed, pickled, skin-passed | AISI 348H 2B – thinner plates |
| Special | Ground or custom finishes | AISI 348H Special – on request |
SHH STEEL regularly supplies AISI 348H in No.1 finish, which is the preferred condition for most high-temperature plate applications.
Tolerances
Dimensional tolerances for AISI 348H 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 348H | — | — |
| UNS S34809 | Unified Numbering System | — |
| ASTM A240 Type 348H | ASTM A240 | When dual certified |
| Related high-C Nb-stabilized + low Co | EN / JIS / GB | Approximate national equivalents |
| Related 348 / 347H / 321H | Multiple | Standard / related H-grade variants |
Related grades for comparison include a240 348, a240 347, a240 347h, a240 321, a240 321h and a240 310h.
Applications
AISI 348H is selected for applications requiring both improved high-temperature strength/creep resistance and controlled low cobalt content. Typical applications of AISI 348H include:
| Industry / Sector | Typical Components / Equipment (with keywords) |
|---|---|
| Nuclear Industry | AISI 348H components requiring low cobalt and high-temp strength |
| Heat Exchangers & Boilers | AISI 348H heat exchanger components, tubesheets and shells |
| Power Generation | AISI 348H high-temperature ducting and load-bearing parts |
| Chemical & Process Industry | AISI 348H process equipment operating at elevated temperature |
| Furnace & Heat Treatment | AISI 348H furnace components, fixtures and supports |
| Expansion Joints | AISI 348H expansion joints requiring strength + stabilization |
| General High-Temperature Service | AISI 348H equipment under load in the sensitization range |
SHH STEEL supplies AISI 348H for these specialized 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 348H 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 low-cobalt material with controlled grain size for optimized creep resistance
- Flexible dimensions and surface finishes (including AISI 348H No.1 and AISI 348H 2B)
- Technical support for selection among 348, 348H, 347, 347H 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 348H over AISI 348?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 and low-cobalt control. SHH STEEL recommends 348H when long-term strength under load at elevated temperature is important in nuclear or specialized service.
- Why is grain size controlled for AISI 348H?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 348H plates.
- How does AISI 348H compare with AISI 347H?Both are high-carbon niobium-stabilized grades. 348H has additional restrictions on cobalt and tantalum for nuclear suitability. SHH STEEL can supply both and help select the appropriate grade based on project requirements.
- Is AISI 348H magnetic?Non-magnetic in the annealed condition. SHH STEEL supplies fully annealed material as standard.
- What is the density of AISI 348H?Approximately 7.90–8.00 g/cm³. SHH STEEL provides material certificates confirming physical and mechanical properties, including grain size.
- Can AISI 348H 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 348H material?Yes, SHH STEEL commonly supplies dual-certified material upon request.
Conclusion
AISI 348H Stainless Steel Plate is the high-carbon, niobium-stabilized, low-cobalt version of the 348 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 and suitability for nuclear applications. It is an outstanding choice for specialized high-temperature service requiring both elevated strength and controlled cobalt content.
As a professional China steel mill-Direct Supply, SHH STEEL provides high-quality AISI 348H 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 348H No.1 and AISI 348H 2B), or a competitive quotation.
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