What Is a Seamless Alloy 31 tube?
Seamless Alloy 31 Tube (UNS N08031 / 1.4562) – Super Austenitic Stainless Steel for Severe Corrosion Environments
Alloy 31 Seamless Tube is supplied for high PREN nickel-iron-chromium-molybdenum chemistry for severe acid and chloride service. The size range shown (OD 6–257 mm; WT 0.5–35 mm) is the overall capability across this product family, not a per-grade commitment. Confirm the specific OD × WT × length combination for the ordered grade in the quotation. The governing specification must be stated on the purchase order: ASTM B622 / ASME SB622, UNS N08031. Chemistry, mechanical properties, heat treatment, dimensional tolerance, NDT and certification must be reported against the ordered standard and material heat; do not treat typical values as guaranteed acceptance limits.
Manufactured through a seamless process from solid billets (piercing + cold drawing), it features a homogeneous, weld-free structure with no longitudinal weld seam, avoiding the weld-related corrosion risks that welded tube must otherwise consider; allowable pressure is calculated from the governing design code.
With a high PREN value ≥ 48, Alloy 31 offers exceptional resistance to localized corrosion and serves as a cost-effective alternative to higher nickel alloys such as Alloy 625 and C276 in many aggressive chemical applications.
2. Key Technical Advantages
- Outstanding Corrosion Resistance
Excellent resistance to pitting, crevice corrosion, and general corrosion in halide-containing media, sulfuric acid (H₂SO₄), and phosphoric acid (H₃PO₄). - High Resistance to Stress Corrosion Cracking (SCC)
Elevated nickel and molybdenum content significantly improves resistance to chloride-induced SCC. - Enhanced Performance in Reducing Acids
The addition of Copper (Cu) and Nitrogen (N) enhances corrosion resistance in strongly reducing environments. - Good High-Temperature Stability
Maintains mechanical integrity at elevated temperatures, outperforming conventional 300-series stainless steels. - Excellent Weldability
Low susceptibility to intergranular corrosion in the heat-affected zone (HAZ), ensuring reliable fabrication performance. - Cost-Effective Alternative to Nickel Alloys
Provides an optimal balance between performance and cost compared to high-grade nickel alloys (e.g., Alloy 625, C276).
Product Specifications and Data
- The composition of Alloy 31 is carefully balanced to achieve its superior corrosion resistance and high strength.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| N08031 | Alloy 31 | 1.4562 | X1NiCrMoCu32-28-7 | Not listed in grade index | Not listed in grade index |
Grade correspondence does not make ASTM, ASME, EN, JIS and GB delivery requirements interchangeable. Confirm chemistry, heat treatment, mechanical properties, dimensions, testing and certification against the purchase specification. Approximate or unconfirmed correspondences retain their qualification. See the grade designation index.
Chemical Composition
| C | Si | Mn | P | S | Cr | Ni | Mo | Cu | N | Fe |
|---|---|---|---|---|---|---|---|---|---|---|
| ≤0.015 | ≤0.30 | ≤2.00 | ≤0.020 | ≤0.010 | 26.00–28.00 | 30.00–32.00 | 6.00–7.00 | 1.00–1.40 | 0.15–0.25 | Bal |
Data source: ASTM B622 / ASME SB622, UNS N08031 ≤ heat-analysis acceptance limits per the governing standard. Confirm the values against the ordered edition and the MTC.
- Alloy 31 is specifically designed to maintain its strength and shape in high-stress, corrosive environments.
| Tensile Strength | Yield Strength | Elongation |
|---|---|---|
| ≥ 650 MPa | ≥ 276 MPa | ≥ 40% |
- These physical properties highlight the material’s ability to perform reliably under a wide range of conditions.
| Density | Melting Point | Thermal Expansion | Thermal Conductivity | Modulus of Elasticity | Electrical Resistivity |
|---|---|---|---|---|---|
| 8.1 g/cm³ | 1350–1400 °C approx. | 13.5 μm/m·°C (20–100°C) | 11.5 W/m·K (20°C) | 205 GPa | 1.05 × 10⁻⁶ Ω·m (20°C) |
- ASTM A1016/A1016M Tube Size Tolerance Chart
Size Tolerance Chart (mm)
| Specified Outside Diameter (OD) (Inches) | Permissible Variations in OD (± Inches) |
|---|---|
| 1⁄2 to 1 | ±0.005 |
| Over 1 to 1-1⁄2 | ±0.008 |
| Over 1-1⁄2 to 2 | ±0.010 |
| Over 2 to 2-1⁄2 | ±0.012 |
| Over 2-1⁄2 to 3-1⁄2 | ±0.014 |
| Over 3-1⁄2 to 5 | ±0.020 |
Tolerance basis: permitted variations per the governing specification stated on this page and the applicable general-requirements standard (ASTM A1016 / ASME SA1016) for the ordered product form; the wall-thickness and length variations in this section follow the same basis.
| Specified Outside Diameter (OD) (Inches) | Specified Wall Thickness (WT) (Inches) | Permissible Variation (± Inches) |
|---|---|---|
| 1⁄2 to 1 (Inclusive) | 0.025 to 0.065(Inclusive) | ±0.010 |
| Over 0.065to 0.134 (Inclusive) | ±0.012 | |
| Over 1 to 1-1⁄2 (Inclusive) | 0.025 to 0.065 (Inclusive) | ±0.010 |
| Over 0.065 to 0.134 (Inclusive) | ±0.012 | |
| Over 1-1⁄2 to 2 (Inclusive) | 0.025 to 0.049 (Inclusive) | ±0.011 |
| Over 0.049 to 0.083 (Inclusive) | ±0.012 | |
| Over 0.083 to 0.148 (Inclusive) | ±0.014 | |
| Over 2 to 2-1⁄2 (Inclusive) | 0.032 to 0.065 (Inclusive) | ±0.013 |
| Over 0.065 to 0.109 (Inclusive) | ±0.015 | |
| Over 0.109 to 0.165 (Inclusive) | ±0.017 | |
| Over 2-1⁄2 to 3-1⁄2 (Inclusive) | 0.032 to 0.165 (Inclusive) | ±0.020 |
| Over 0.165 to 0.220 (Inclusive) | ±0.025 | |
| Over 3-1⁄2 to 5 (Inclusive) | 0.083 to 0.165 (Inclusive) | ±0.025 |
| Over 0.165 to 0.220 (Inclusive) | ±0.030 |
Length Tolerance
- For Specific Cut Lengths, the standard tolerance is +1⁄8 in. [3 mm], -0 in. [0 mm].
Important Note: The values presented here are based on the dimensional tolerance tables in ASTM A1016/A1016M (General Requirements for Ferritic Alloy Steel, Austenitic Alloy Steel, and Stainless Steel Tubes), contains other essential requirements like straightness and details for tubes with ODs outside of this range. Always consult the latest official standard for design and procurement.
Typical Applications
Seamless Alloy 31 tubes are widely used in industries requiring superior corrosion resistance:
Chemical & Petrochemical Industry
Heat exchangers, evaporators, and piping systems for sulfuric and phosphoric acid production
Oil & Gas / Marine Engineering
Seawater systems, fire-fighting pipelines, offshore platforms, and sour service environments (H₂S)
Environmental Engineering
Flue Gas Desulfurization (FGD) systems and wastewater treatment plants
Pulp & Paper Industry
Bleaching systems handling chlorine dioxide and aggressive chemicals
Quality Assurance & Certification
- Material Certification
EN 10204 3.1 Mill Test Certificate (MTC) as standard; EN 10204 3.2 on arrangement - Inspection & Testing
PMI, UT, ET, Hydro Test, Intergranular Corrosion (IGC) - Third-Party Inspection Available
ABS, DNV, BV, TÜV, Lloyd’s Register - Full Traceability
From raw material to finished product
Frequently Asked Questions
What sizes are available for Alloy 31 seamless tube?
Which specification governs Alloy 31 seamless tube?
What inspection documents are provided?
Technical review: page data reviewed by the Xinzhe technical desk on 2026-09-27. Chemistry acceptance limits are compiled from the governing ASTM/ASME specification stated on this page; mechanical and physical values are typical reference data and are not acceptance guarantees. Values must be confirmed against the standard edition in force at order time and the material test certificate.
Ready to Request a Quotation?
Send the size (OD and wall or schedule), quantity, length, end finish and the inspection items you need as acceptance criteria — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
Compare this grade with other austenitic and high-alloy grades in our stainless steel seamless pipe and tube ranges. Browse the Stainless Steel Seamless Pipe category. Minimum order quantity and lead time are confirmed on enquiry against the ordered grade, size and quantity.
