ASME SA240 348 Stainless Steel Plate | SA240 Type 348
What is ASME SA240 348 Stainless Steel Plate?
As a professional stainless steel plate supplier and China Mill-Direct Supply / Mill Direct Exporter, SHH STEEL is pleased to present ASME SA240 348 Stainless Steel Plate, also known as SA240 Type 348.
ASME SA240 Type 348 is a niobium- and tantalum-stabilized austenitic chromium-nickel stainless steel. It is closely related to Type 347 but features tighter controls on residual elements, particularly cobalt and tantalum. The niobium + tantalum addition stabilizes carbon, effectively preventing chromium carbide precipitation at grain boundaries and providing outstanding resistance to intergranular corrosion after welding or after prolonged exposure to the sensitization temperature range (approximately 450–850°C).
Type 348 retains the excellent toughness, good formability, and reliable fabricability of the 300-series austenitic stainless steels. Because of its controlled residual element chemistry, it is frequently specified for nuclear applications, high-temperature process equipment, and other services where low cobalt content or tighter chemical control is required. It offers performance essentially equivalent to Type 347 in most high-temperature and welded applications, with the added benefit of more stringent residual element limits.
SHH STEEL supplies ASME SA240 348 as true Mill Direct Supply, sourcing directly from major Chinese stainless steel mills. This model delivers competitive mill pricing, consistent quality, full heat traceability, and shorter lead times. We offer thicknesses from 1 mm to 100 mm (thicker plates available on request), widths up to 2000–3000 mm, and lengths up to 12000 mm or cut-to-length. Material is supplied in the solution-annealed condition with a full range of surface finishes.
Material Specification
| Specification Element | Requirement | SHH STEEL Compliance |
|---|---|---|
| Primary Standard | ASME SA240 / SA240M | Full compliance |
| Steel Grade | Type 348 (UNS S34800) | Confirmed |
| Product Form | Plate, Sheet, Coil | Available |
| Delivery Condition | Solution Annealed | Standard |
| Thickness Range | 1 mm – 100 mm (thicker available) | 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, BA, No.4, HL, Polished | Available |
| Certification | EN 10204 3.1 / ASME Mill Test Certificate | Available |
Chemical Composition
Heat Analysis (Ladle Analysis) according to ASME SA240 Type 348:
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.08 |
| Silicon (Si) | ≤ 0.75 |
| 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 + Tantalum (Nb + Ta) | ≥ 10 × C% |
| Tantalum (Ta) | ≤ 0.10 |
| Cobalt (Co) | ≤ 0.20 (typical control) |
| Nitrogen (N) | ≤ 0.10 |
| Iron (Fe) | Balance |
Product Analysis (typical permissible variations):
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.08 |
| Silicon (Si) | ≤ 0.75 |
| Manganese (Mn) | ≤ 2.00 |
| Phosphorus (P) | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 |
| Chromium (Cr) | 16.90 – 19.10 |
| Nickel (Ni) | 8.90 – 13.10 |
| Niobium + Tantalum (Nb + Ta) | ≥ 10 × C% |
| Tantalum (Ta) | ≤ 0.10 |
The combined niobium + tantalum content of at least ten times the carbon percentage provides effective stabilization. Tighter limits on tantalum and cobalt distinguish Type 348 from standard Type 347 and make it suitable for applications with residual element restrictions.
Mechanical Properties
Room-Temperature Mechanical Properties (Annealed Condition)
| Property | Value |
|---|---|
| Tensile Strength | ≥ 515 MPa (75 ksi) |
| Yield Strength (0.2%) | ≥ 205 MPa (30 ksi) |
| Elongation (in 50 mm) | ≥ 40% |
| Hardness | ≤ 217 HB / ≤ 95 HRB |
Elevated-Temperature Behavior ASME SA240 Type 348 maintains useful strength and excellent resistance to sensitization at temperatures up to approximately 900°C. Its high-temperature performance is essentially equivalent to Type 347.
Physical Properties
- Density: 7.93 g/cm³
- Melting Range: approximately 1400–1425°C
- Magnetic: Non-magnetic in the annealed condition
Material Comparison
| Grade | Stabilization | Key Distinction | Typical Preference |
|---|---|---|---|
| SA240 Type 321 | Titanium | Good sensitization resistance | General welded high-temperature service |
| SA240 Type 347 | Niobium | Excellent high-temperature stability | Most severe continuous high-temp service |
| SA240 Type 348 | Niobium + Tantalum | Same stability + tighter residual element control | Nuclear, special high-temp, or low-cobalt service |
| SA240 Type 347H | Niobium (higher carbon) | Higher strength at elevated temperature | Continuous high-temp service requiring higher allowable stresses |
| SA240 Type 316Ti | Titanium + Mo | Stabilization + better pitting resistance | High-temp + chloride service |
Type 348 is essentially interchangeable with Type 347 in most high-temperature and welded applications, but is preferred when specifications require tighter control of cobalt, tantalum, or other residual elements. It is frequently specified alongside or instead of astm a240 type 347 stainless steel sheet plate for nuclear or special-service projects. For general high-temperature welded service without residual element restrictions, Type 347 remains the more commonly available option. When improved chloride resistance is also needed, astm a240 type 316ti stainless steel sheet plate should be considered.
Corrosion Resistance
In the annealed condition, ASME SA240 Type 348 offers corrosion resistance similar to Type 347 and Type 304 in most atmospheric, fresh-water, and oxidizing environments. Its principal advantage is the excellent resistance to intergranular corrosion after welding or after prolonged exposure to the temperature range of 450–850°C, thanks to niobium-tantalum stabilization.
Resistance to pitting and crevice corrosion in chloride environments is comparable to 304 and inferior to molybdenum-containing grades. For combined high-temperature and chloride service, a molybdenum-bearing stabilized grade is preferred.
Weldability
ASME SA240 Type 348 has excellent weldability by all standard fusion and resistance welding processes. Because the grade is stabilized with niobium and tantalum, it can normally be used in the as-welded condition without risk of intergranular corrosion.
Matching niobium-stabilized filler metals (E347 / ER347) are recommended to maintain stabilization in the weld metal. Post-weld heat treatment is generally not required for corrosion resistance.
Heat Treatment
ASME SA240 Type 348 is supplied in the solution-annealed condition.
Recommended Solution Annealing Parameters
- Temperature range: 980 – 1150°C (typically 1040 – 1120°C)
- Holding (soaking) time: – Plates ≤ 25 mm: minimum 10–20 minutes after the section reaches temperature – Plates 25–50 mm: minimum 20–40 minutes – Plates > 50 mm: 30–60 minutes or longer to ensure uniformity throughout the cross-section
- Cooling: Rapid cooling (water quench preferred for thicker plates) to retain the stabilized structure and maximum corrosion resistance
An optional stabilizing heat treatment at approximately 840–900°C for several hours can be applied in special cases to ensure complete niobium/tantalum carbide precipitation, although modern melting practices usually make this unnecessary for most applications.
Surface Finishes
| Finish | Description | Typical Use / Keywords |
|---|---|---|
| No.1 | Hot-rolled, annealed and pickled | SA240 348 No.1 – most common for pressure vessel and industrial plate |
| 2B | Cold-rolled, annealed, pickled, skin-passed | SA240 348 2B – general fabrication and process equipment |
| BA | Bright Annealed | SA240 348 BA – clean and special applications |
| No.4 | Brushed (satin) finish | SA240 348 No.4 – architectural or visible surfaces |
| HL | Hairline finish | SA240 348 HL – decorative panels |
| Polished | Mirror or custom polish | SA240 348 Polished – sanitary and high-end applications |
SHH STEEL regularly supplies ASME SA240 348 in No.1 and 2B finishes, and can provide BA, No.4, HL, and polished finishes according to project requirements.
Tolerances
Dimensional tolerances conform to ASME SA240 and the general requirements of ASTM A480. Thickness, width, length, and flatness are controlled within standard or tighter agreed limits.
Equivalent Material Grades
| Grade / Designation | Standard | Notes |
|---|---|---|
| SA240 Type 348 | ASME SA240 | — |
| A240 Type 348 | ASTM A240 | Essentially identical |
| UNS S34800 | — | Unified Numbering System |
| 1.4550 (related) | EN 10088-2 | Closest European Nb-stabilized grade |
| Related 348 grades | JIS / GB | Approximate national equivalents |
Related grades frequently evaluated with ASME SA240 348 include astm a240 type 347 stainless steel sheet plate, astm a240 type 347h stainless steel sheet plate, astm a240 type 321 stainless steel sheet plate, and astm a240 type 316ti stainless steel sheet plate.
Applications
ASME SA240 Type 348 is used in high-temperature and welded applications, particularly where residual element control is specified:
| Industry / Sector | Typical Components / Equipment |
|---|---|
| Nuclear | Components requiring low cobalt and controlled residuals |
| Chemical & Petrochemical | High-temperature reactors, piping, heat exchangers |
| Power Generation | Boiler components, superheater parts |
| Heat Treatment Equipment | Fixtures, radiant tubes, furnace parts |
| Pressure Vessels | High-temperature shells and components |
| Aerospace & Exhaust Systems | High-temperature exhaust components |
| General Fabrication | Welded structures requiring long-term high-temp stability and residual control |
Why Choose SHH STEEL
SHH STEEL is a China Mill-Direct Supply and Mill Direct Exporter of stainless steel plate. We maintain long-term strategic cooperation with major Chinese stainless steel mills and supply ASME SA240 Type 348 with the following advantages:
- Competitive mill-direct pricing
- Consistent quality and complete heat traceability
- Full Mill Test Certificates (EN 10204 3.1 / ASME)
- Flexible dimensions and surface finishes (including SA240 348 No.1 and SA240 348 2B)
- Technical support for high-temperature and special-residual material selection
- Reliable worldwide logistics and export documentation
FAQ
- What is the main difference between SA240 347 and SA240 348?Both are niobium-stabilized grades with essentially equivalent corrosion and high-temperature performance. Type 348 has tighter controls on residual elements (especially cobalt and tantalum), making it preferred for nuclear and special-service applications.
- When should I choose Type 348 instead of Type 347?Choose Type 348 when the project specification requires low cobalt content or tighter residual element limits. For general high-temperature service, Type 347 is usually sufficient and more readily available.
- Is ASME SA240 348 magnetic?Non-magnetic in the annealed condition. It may become slightly magnetic after heavy cold working.
- What is the density of SA240 Type 348?7.93 g/cm³.
- Can SHH STEEL supply dual-certified ASME SA240 / ASTM A240 Type 348?Yes, dual certification is commonly available.
Conclusion
ASME SA240 348 Stainless Steel Plate (SA240 Type 348) is a niobium-tantalum stabilized austenitic stainless steel that offers excellent resistance to intergranular corrosion, reliable high-temperature performance, and tighter control of residual elements. It is the preferred stabilized grade for applications requiring low cobalt or special chemical restrictions while maintaining the performance of Type 347.
As a professional China Mill-Direct Supply and Mill Direct Exporter, SHH STEEL provides high-quality ASME SA240 Type 348 plate with competitive pricing, full certification, and complete technical support.
Contact SHH STEEL today for stock availability, surface finish options (including SA240 348 No.1 and SA240 348 2B), or a competitive quotation.
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