Hangbo Alloy Group
Shanghai · Est. 2012
UNS N08031 / W.Nr. 1.4562 — Chemical composition, mechanical properties, and corrosion resistance data for engineers and procurement professionals.
Alloy 31 (UNS N08031 / W.Nr. 1.4562) is a high-chromium nickel-iron-molybdenum alloy with nitrogen addition that provides excellent resistance to pitting and crevice corrosion in chloride environments. The nitrogen addition significantly improves the alloy's PREN (Pitting Resistance Equivalent Number).
The chemical composition of Alloy 31 is carefully controlled to achieve its unique combination of properties and performance characteristics.
| Element | Min % | Max % |
|---|---|---|
| Iron (Fe) | Balance | Balance |
| Nickel (Ni) | 30.0 | 32.0 |
| Chromium (Cr) | 26.0 | 28.0 |
| Molybdenum (Mo) | 6.0 | 7.0 |
| Nitrogen (N) | 0.15 | 0.25 |
| Copper (Cu) | 1.0 | 1.40 |
| Carbon (C) | — | 0.02 |
| Manganese (Mn) | — | 2.0 |
The mechanical properties of Alloy 31 vary depending on product form and heat treatment condition. The data below represents typical values for solution-annealed material.
| Property | Value |
|---|---|
| Tensile Strength | 700 MPa |
| Yield Strength (0.2% offset) | 320 MPa |
| Elongation in 2 inches | 50% |
| Density | 8.10 g/cm3 |
| Melting Point | 1350 °C |
| Max Service Temperature | 700 °C |
Excellent resistance to pitting and crevice corrosion in chloride-containing environments. Good resistance to sulfuric acid at medium and high concentrations. Outstanding resistance to caustic environments. Superior to 904L in many aggressive media.
The unique combination of properties makes Alloy 31 suitable for a wide range of demanding applications:
Hangbo Alloy Group manufactures and supplies Alloy 31 in the following product forms, conforming to ASTM, AMS, and ASME specifications:
| Standard | Description |
|---|---|
| ASTM B625 | Plate, Sheet, and Strip |
| ASTM B622 | Seamless Pipe |
| ASTM B619 | Welded Pipe |
| ASTM B690 | Seamless Tube |
| ASTM B366 | Fittings |
| VdTUV 521 | German Approval |
Alloy 31 (UNS N08031) was developed as a "superaustenitic" bridge between 6Mo stainless steels and the high-nickel C-type alloys. Nitrogen addition raises both strength and pitting resistance without the cost of a fully nickel-based grade.
| Property | Typical value |
|---|---|
| PREN (Cr + 3.3Mo + 16N) | ≈ 54 |
| Critical pitting temperature | > 75 °C |
| Nickel content | 30–32 % |
| Molybdenum | 6.0–7.0 % |
| Sulphuric acid, 50 %, 80 °C | Corrosion rate < 0.1 mm/yr |
This combination makes it a standard choice for flue-gas desulphurisation absorbers, phosphoric acid evaporators and mixed-acid pickle lines where 316L and 904L fail but full C-276 is hard to justify.
In many wet-chemical duties, yes — and at lower cost. It is not equivalent in the most aggressive mixed oxidising/reducing acids or where wet chlorine is present; for those, C-276 or C-22 remains the safe specification.
Alloy 31 has roughly 15 PREN points more than 904L and better resistance to sulphuric and phosphoric acid. It also retains strength better at elevated temperature because of its higher nickel content.
Yes for flowing seawater and brackish cooling water, but avoid creviced, stagnant conditions at elevated temperature — the same limitation applies to all stainless grades; check our chloride SCC guidance.
UNS N08031 / W.Nr. 1.4562: about 30-32% nickel, 26-28% chromium, 6-7% molybdenum, 1.0-1.4% copper and 0.15-0.25% nitrogen, iron balance. The nitrogen significantly raises the PREN.
It resists the acidic chlorides and sulfuric-acid condensate in scrubbers and absorbers, delivering pitting and crevice corrosion resistance at lower cost than C-type nickel alloys.
Tensile strength about 700 MPa, yield strength about 320 MPa and 50% elongation in the solution-annealed condition.
UNS N08031 and W.Nr. 1.4562, with product forms following the standard ASTM/EN framework for nickel-iron-chromium plate, sheet, tube and bar.
About 700 °C, although structural strength drops well before the oxidation limit.
Yes, with matching or over-alloyed nickel filler. Keep heat input low and surfaces clean to retain corrosion resistance of the as-welded metal.
Hangbo Alloy Group maintains extensive inventory of Alloy 31 in all standard product forms. We can provide mill test certificates, third-party inspection reports (SGS, TUV), and custom processing services.
For quotations, material certifications, or technical consultation, contact our sales team or call +86 166 2109 2936. We typically respond within 10 minutes.
Request a quotation for Alloy 31 round bars, tubes, plates, or custom products. We stock standard sizes and accept custom orders.