ASTM A240 Type 348H Stainless Steel Sheet & Plate
What is ASTM A240 Type 348H Stainless Steel Sheet and Plate?
As a professional stainless steel supplier, SHH STEEL is pleased to present ASTM A240 Type 348H Stainless Steel Sheet and Plate. Also known as UNS S34809, this high-carbon version of Type 348 is specifically developed for continuous elevated-temperature applications where enhanced creep resistance and controlled low tantalum content are required.
Type 348H combines niobium-tantalum stabilization with a controlled higher carbon content (0.04–0.10%) and a mandatory grain size of ASTM No. 7 or coarser. The low maximum tantalum content differentiates it from standard Type 347H. These features significantly improve high-temperature strength and long-term creep performance while maintaining excellent resistance to intergranular corrosion. SHH STEEL supplies ASTM A240 Type 348H in both sheet and plate forms, covering thicknesses from 0.5 mm to 100 mm, with widths up to 2500 mm and lengths up to 12000 mm. Custom sizes and surface finishes are available.
The material is typically delivered in the solution-annealed condition with full Mill Test Certificates (EN 10204 3.1), including grain size results. Whether for thin sheet fabrication or heavy plate applications, SHH STEEL provides consistent quality for demanding high-temperature and specialized projects worldwide.
ASTM A240 Type 348H Material Specification
ASTM A240 Type 348H stainless steel sheet and plate are manufactured in accordance with ASTM A240/A240M and ASME SA-240. This specification covers chromium-nickel-niobium-tantalum stainless steel plate, sheet and strip for pressure vessels and general applications, including high-temperature service.
| Specification Element | Requirement | SHH STEEL Compliance |
|---|---|---|
| Primary Standard | ASTM A240 / ASME SA-240 Type 348H | Full compliance |
| Product Form | Sheet and Plate | Both available |
| Thickness Range | 0.5 mm – 100 mm | Custom sizes available |
| Width / Length | Up to 2500 mm / 12000 mm | Custom fabrication supported |
| Surface Finish | 2B, No.1, BA, HL | Multiple options |
| Heat Treatment Condition | Solution Annealed | Standard supply condition |
| Grain Size Requirement | ASTM No. 7 or coarser | Mandatory for Type 348H |
| Certification | EN 10204 3.1 / 3.2 | Available |
Chemical Composition
The chemical composition of ASTM A240 Type 348H is designed to provide enhanced high-temperature strength through controlled carbon content, niobium-tantalum stabilization and limited tantalum.
| Element | Content (%) | Standard Limit | Role |
|---|---|---|---|
| Carbon (C) | 0.04 – 0.10 | 0.04 – 0.10 | Improves high-temperature creep strength |
| Manganese (Mn) | ≤ 2.00 | 2.00 max | Deoxidation and strength |
| Phosphorus (P) | ≤ 0.045 | 0.045 max | Impurity control |
| Sulfur (S) | ≤ 0.030 | 0.030 max | Cleanliness |
| Silicon (Si) | ≤ 0.75 | 0.75 max | Deoxidation |
| Chromium (Cr) | 17.00 – 19.00 | 17.00 – 19.00 | Corrosion and oxidation resistance |
| Nickel (Ni) | 9.00 – 13.00 | 9.00 – 13.00 | Austenite stability and toughness |
| Niobium (Nb) + Tantalum (Ta) | 8×C min – 1.00 max | 8×C min – 1.00 max | Stabilization against intergranular corrosion |
| Tantalum (Ta) | ≤ 0.10 | 0.10 max | Controlled low tantalum content |
| Nitrogen (N) | ≤ 0.10 | 0.10 max | Strength contribution |
Mechanical Properties
In the solution-annealed condition, ASTM A240 Type 348H provides good room-temperature properties and superior high-temperature performance.
| Property | Value | Test Method |
|---|---|---|
| Tensile Strength | ≥ 515 MPa (75 ksi) | ASTM A370 |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (30 ksi) | ASTM A370 |
| Elongation in 50 mm | ≥ 40% | ASTM A370 |
| Hardness | ≤ 217 HB / ≤ 95 HRB | ASTM E10/E18 |
| Density | 8.00 g/cm³ | — |
| Grain Size | ASTM No. 7 or coarser | ASTM E112 |
Delivery Conditions
SHH STEEL supplies ASTM A240 Type 348H primarily in the solution-annealed and pickled condition. Detailed capabilities by surface finish are as follows:
2B Finish (Cold-rolled, annealed, pickled and skin-passed)
- Typical thickness range: 0.5 mm – 6.0 mm (most common 0.8 mm – 3.0 mm)
- Maximum width: up to 1500–2000 mm depending on thickness
- Preferred for applications requiring a smooth surface and good flatness.
No.1 Finish (Hot-rolled, annealed and pickled)
- Typical thickness range: 3.0 mm – 100 mm (most common 4.0 mm – 50 mm)
- Maximum width: up to 2000–2500 mm
- Standard finish for heavy plates used in high-temperature equipment and structural components.
Other Finishes
- BA (Bright Annealed): Available in thinner gauges
- HL (Hairline): Available on request
Protective PVC film can be applied on one or both sides. Precision cutting (plasma, laser or waterjet) and closer dimensional tolerances are available upon request.
Tolerances
Dimensional tolerances for ASTM A240 Type 348H sheet and plate follow ASTM A480/A480M.
- Thickness tolerances vary by product form and thickness. Cold-rolled sheet has tighter controls, while hot-rolled plate follows standard allowable deviations.
- Width tolerance is typically +6 mm / 0 mm.
- Length tolerance for cut-to-length material is normally +10 mm / 0 mm.
- Flatness is controlled according to ASTM A480; improved flatness can be supplied for precision fabrication.
- Edge conditions include mill edge, slit edge, sheared edge or plasma/laser cut edge according to customer preference.
Tighter tolerances can be arranged for special projects.
Weldability
ASTM A240 Type 348H can be welded using standard fusion welding processes such as GTAW (TIG), GMAW (MIG) and SMAW. Due to the higher carbon content, heat input should be controlled. Matching or slightly over-alloyed filler metals (e.g., ER347 or ER348) are recommended. Preheating is generally not required. Post-weld cleaning and passivation are advised to restore optimum performance. In critical high-temperature applications, the effect of welding on creep properties should be carefully evaluated.
Equivalent Material Grades
| Grade | Standard | Designation |
|---|---|---|
| Type 348H | ASTM A240 / ASME SA-240 | — |
| UNS S34809 | Unified Numbering System | S34809 |
| Related to 1.4961 | EN (with Ta control) | High-carbon Nb-stabilized equivalent |
| Related Chinese grades | GB/T series | High-carbon Nb-stabilized 18Cr-11Ni types with low Ta |
| SUS348H | JIS (reference) | — |
Applications
ASTM A240 Type 348H is selected for continuous high-temperature service where improved creep strength, intergranular corrosion resistance and controlled low tantalum content are required. Typical applications are shown below with relevant keywords:
| Application Area | Typical Components / Uses (Keywords) |
|---|---|
| Power Generation | Superheater supports, boiler components, heat recovery systems – A240 348H Power |
| Petrochemical Industry | Furnace parts, reformer components, high-temp piping – A240 348H Petrochemical |
| Chemical Processing | High-temperature reactors and process equipment – A240 348H Chemical Processing |
| Nuclear & Specialized Service | Applications requiring low tantalum content – A240 348H Nuclear |
| Heat Treatment Equipment | Furnace hardware, radiant tubes, fixtures – A240 348H Heat Treatment |
| Industrial High-Temperature Service | Structural components under continuous elevated temperature – A240 348H Industrial |
Why Choose SHH STEEL
SHH STEEL maintains long-term strategic cooperation with major Chinese stainless steel mills and acts as a first-level (primary) agent for these mills. This direct partnership enables us to offer competitive pricing advantages, faster delivery times and consistent quality assurance that many intermediate traders cannot match.
All ASTM A240 Type 348H material is sourced from reputable Chinese mills under strict quality control, supplied with complete Mill Test Certificates (including grain size results), and supported by our professional export team. Customers benefit from reliable supply, short lead times, technical support and cost-effective solutions for high-temperature and specialized applications worldwide.
FAQ
-
What is the main difference between 348 and 348H?
- Type 348H has a higher controlled carbon content (0.04–0.10%) and must meet a grain size requirement of ASTM No. 7 or coarser. These features provide better creep strength for continuous high-temperature service. Type 348 has carbon ≤ 0.08%.
-
What is the difference between 347H and 348H?
- Both are high-carbon niobium-stabilized grades with grain size requirements. Type 348H has a controlled maximum tantalum content (typically ≤ 0.10%), while Type 347H does not have the same strict tantalum limitation.
-
Why is grain size important for Type 348H?
- Coarser grain size (ASTM No. 7 or coarser) improves high-temperature creep and rupture strength, which is critical for continuous elevated-temperature applications.
-
What are the equivalent grades of ASTM A240 Type 348H?
- The primary designation is UNS S34809. It is related to high-carbon niobium-stabilized grades in EN, Chinese and Japanese standards with controlled low tantalum.
-
What is the density of ASTM A240 Type 348H?
- Approximately 8.00 g/cm³.
Conclusion
ASTM A240 Type 348H Stainless Steel Sheet and Plate from SHH STEEL deliver enhanced high-temperature creep strength and excellent resistance to intergranular corrosion through controlled higher carbon content, niobium-tantalum stabilization, low tantalum and mandatory grain size requirements. With strict quality control, flexible sizing options, competitive pricing through direct mill partnerships and professional global export service, we provide trusted solutions for continuous elevated-temperature and specialized applications worldwide.
Contact SHH STEEL today for your ASTM A240 Type 348H requirements.
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