The PREN of Alloy 31 is above 54. PREN. It is calculated from Cr, Mo, and N content. A higher value means better resistance to chloride pitting. Most standard austenitic grades fall well below this figure.
Alloy 31 Seamless Pipe | UNS N08031 | 1.4562 Seamless Pipe
Alloy 31 is a nickel-iron-chromium-molybdenum alloy, also known as UNS N08031 or W.Nr. 1.4562. We at XTD (Zhejiang Xintongda Special Steel) are a reliable manufacturer and supplier of Alloy 31 seamless pipes. Our pipes are produced to ASTM B622 standards using cold rolling, cold drawing, annealing, pickling, and straightening.
UNS N08031 seamless pipe has a chemical composition of about 26-28% Cr, 30-32% Ni, 6.0-7.0% Mo, 1.0-1.4% Cu, and 0.15-0.25% N, which gives it strong resistance to pitting, crevice corrosion, and stress corrosion cracking.
It works reliably in temperatures from -196°C to 400°C, so it can handle both very low and high temperatures. XTD keeps stock ready for quick shipment in about one week, and custom production orders are usually completed within 15 to 60 days, depending on the requirements.
Product specifications:
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Standard
ASTM B622
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OD Range
6-610 mm
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Thickness
0.5-40 mm
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Length
≤ 18 m
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How Alloy 31 Seamless Pipe is Produced
We make high-quality Alloy 31 seamless pipes using a clear and controlled process. We begin with a nickel-iron-chromium-molybdenum alloy ingot and hot extrude or pierce it to form a seamless tube. Then we use cold drawing, cold rolling or pilger processing to achieve precise and uniform dimensions.
After that, we perform solution annealing to restore the microstructure and pickle the surface to get a clean, smooth finish. Each pipe is then straightened and tested by eddy-current and hydrostatic methods before being cut to length and packed. To learn more about our manufacturing process, visit our detailed process page.
Key Features of Alloy 31 Seamless Pipe
This section explains the key features of UNS N08031 seamless pipes, such as their corrosion resistance, ability to handle chemicals, mechanical strength, and how they behave during fabrication under different operating conditions.
- Superior Pitting and Crevice Corrosion Resistance: 1.4562 has a PREN above 54, placing it among the highest-rated nickel alloys. The high Mo and N content makes it highly resistant to localised attack in chloride-containing environments.
- Outstanding Sulfuric Acid Resistance: This alloy handles sulfuric acid across a wide concentration range, including hot, concentrated conditions that degrade most stainless and lower-grade nickel alloys. It is regularly specified for acid piping and heat exchanger service.
- Excellent Phosphoric Acid Resistance: Alloy 31 performs well in wet-process phosphoric acid, environments containing fluoride and chloride impurities. This makes it suitable for fertiliser and chemical processing where acid purity varies.
- Resistance to Stress Corrosion Cracking: The high nickel content of 30 to 32% provides solid resistance to chloride-induced stress corrosion cracking. This is useful in process lines where thermal cycling and tensile stress are both present.
- Good Mechanical Strength: Tensile strength exceeds 650 MPa, with a yield strength above 270 MPa. The alloy retains appropriate mechanical properties across its full service temperature range from -196°C to 400°C.
- Weldability and Fabricability: Alloy 31 can be welded using standard processes, including GTAW and SMAW. It does not require post-weld heat treatment in most cases, and it cold works without significant difficulty during fabrication.
ASTM B622 Alloy 31 Seamless Pipe Equivalent Materials
Different regions and project specifications refer to this alloy under different designations. This makes it easier to find equivalent materials, avoid confusion, and ensure correct material verification during purchasing and inspection.
| GRADE | Alloy 31 |
| UNS | N08031 |
| W.Nr. / EN | 1.4562 |
| EN Name | X1NiCrMoCu32-28-7 |
| Trade Name | Nicrofer 3127 hMo |
| JIS | — |
| ISO | — |
100% Certified Testing & Documentation | NACE MR0175 Sour Service Compliance
Every shipment of Alloy 31 seamless pipe comes with complete documents that confirm its chemical comosition, mechanical strength, corrosion performance, and dimensions. XTD also provides full material traceability and can arrange third-party inspections when needed. All pipes are tested and certified to relevant standards, including NACE MR0175 for sour service.
Certificates and documentation available:
- Mill Test Certificate (MTC) per EN 10204 3.1 / 3.2
- Chemical composition report
- Mechanical test report (tensile, hardness, impact)
- Intergranular corrosion test (ASTM A262)
- Pitting corrosion test (ASTM G48)
- Hydrostatic test report
- Eddy current test report
- Dimensional inspection report
- NACE MR0175 compliance documentation
Alloy 31 Seamless Pipe Industrial Applications
Alloy 31 seamless pipe is used across several industries dealing with chemical processing, energy, environments, and industrial sectors where standard materials fail under aggressive conditions.
Phosphoric Acid Production
Alloy 31 is used in wet-process phosphoric acid plants because its high molybdenum and chromium resist fluoride and chloride impurities, so pipes last longer and need replacing less often.
Sulfuric Acid Concentration and Handling
Alloy 31 is good at handling both general and localised corrosion. This pipe is used in piping systems that carry hot, concentrated sulfuric acid.
Flue Gas Desulfurisation (FGD) Systems
FGD absorber vessels and ducting are exposed to dilute sulfuric acid, chlorides, and moisture simultaneously. UNS N08031 pipe is used in these systems where lower-grade alloys show early pitting and weld zone attack.
Pulp and Paper Bleaching Plants
Bleaching circuits use chlorine dioxide and hypochlorite, which quickly damage normal stainless steel. Alloy 31 withstands these chemicals better, with less risk of pitting and stress corrosion cracking than 316L or 317L stainless grades.
Chemical Processing
XTD’s Alloy 31 pipe is used in reactors, transfer lines, and heat exchangers that handle mixed acids, halide-containing fluids, and other harsh chemicals. Its broad corrosion resistance suits many different process units in one plant.
Seawater and Brine Handling
Alloy 31 resists pitting in seawater and concentrated brine at elevated temperatures. It is used in offshore processing, desalination-adjacent systems, and coastal chemical plants where chloride levels are consistently high.
Frequently Asked Questions
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What is the PREN of Alloy 31, and why does it matter?
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Can Alloy 31 Replace Alloy 926 or Alloy 625?Yes. Alloy 31 matches Alloy 926 in many acid services and can replace Alloy 625 in corrosion-focused, not high-temperature or high-pressure, applications more cheaply.
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What Standards Apply to Alloy 31 Seamless Pipes?Alloy 31 seamless pipes mainly follow ASTM B622. ASME SB-622 and related EN/DIN standards for W.Nr. 1.4562 may also be used for code compliance.
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Is Alloy 31 Suitable for NACE Sour Service?Yes. Alloy 31 / UNS N08031 meets the requirements of NACE MR0175 / ISO 15156 for sour service. XTD supplies full compliance documentation with each order where this is required.