Alloy 31 (UNS N08031): Grades, Properties & Supply
Basic Description
Sagiant Piping Industries supports enquiries for Alloy 31 (UNS N08031, Werkstoff 1.4562; also known as Nicrofer 3127 hMo) as pipe, tube, buttweld and forged fittings, flanges, bars, sheet/plate and fasteners. This 6–7Mo super-austenitic iron-nickel-chromium-molybdenum alloy with copper and nitrogen additions offers strong resistance to hot sulphuric and phosphoric acids, pitting, crevice corrosion and chloride stress-corrosion cracking — performance still depends on concentration, temperature, aeration and weld condition. Its PREN is best read as an index range (roughly 50–52 by the Cr+3.3Mo+16N formula, higher with a 30×N nitrogen coefficient), not a single guaranteed value. N08031 is an active grade covered by current ASTM references (B625, B649, B622/B619/B626, B366, B564), EN 10216-5 and VdTÜV Werkstoffblatt 509; the accepted specification and edition are confirmed per order with EN 10204 3.1 or 3.2 documentation. Alloy 31 Plus (UNS N08034 / 2.4692) is a separate, further-developed grade, not an alias. Sagiant is an independent supplier and stockist, not the alloy producer.
Alloy 31 (N08031): chemistry, properties, standards and RFQ data
Alloy 31 (N08031) composition, condition-scoped mechanical and physical reference data, PREN index, current standards status and acid/chloride corrosion guidance. Producer reference values are shown separately from specification acceptance limits confirmed on the certificate; Alloy 31 Plus (N08034) is a distinct grade.
Technical Specification
| Parameter | Specification |
|---|---|
| Material | Alloy 31 (UNS N08031, W.-Nr. 1.4562, X1NiCrMoCu32-28-7; producer designation Nicrofer 3127 hMo) — a 6–7% Mo super-austenitic Fe-Ni-Cr-Mo alloy with copper and nitrogen. Alloy 31 Plus (N08034) is a separate, related alloy |
| Product Forms | Seamless & welded pipe/tube, buttweld & forged fittings, flanges, bars, sheet/plate/strip and fasteners — per grade/form availability |
| Supply Condition | Solution-annealed and quenched per specification |
| Standards | ASTM B625 (flat), B649 (bar/wire), B622 (seamless pipe/tube), B619 (welded pipe), B626 (welded tube), B366 (fittings), B564 (forgings); EN 10216-5 (seamless tube); VdTÜV material sheet 509 — confirm the ordered edition and covered forms |
| Testing & Docs | Heat chemistry (with nitrogen by suitable analysis), tensile, hardness, intergranular corrosion (ASTM G28 Method A as ordered), PMI, NDE per order; MTC EN 10204 3.1 or 3.2 |
Sagiant Piping Industries is an independent supplier and stockist, not the alloy producer. Identify the exact specification edition, condition and any producer requirement on enquiry; do not treat producer typical data as a contractual minimum.
Chemical Composition (mass %)
| Element | Alloy 31 (UNS N08031) |
|---|---|
| Nickel | 30.0–32.0 |
| Chromium | 26.0–28.0 |
| Molybdenum | 6.0–7.0 |
| Copper | 1.0–1.4 |
| Nitrogen | 0.15–0.25 |
| Carbon | ≤0.015 |
| Silicon | ≤0.30 |
| Manganese | ≤2.0 |
| Phosphorus | ≤0.020 |
| Sulphur | ≤0.010 |
| Iron | Balance |
Limiting composition from the VDM Alloy 31 datasheet; balance does not mean a fixed iron percentage, and the ordered product standard and heat/product certificate control acceptance. Nitrogen is a deliberate alloying addition and must come from a suitable laboratory analysis — handheld XRF PMI cannot measure it. Alloy 31 Plus (N08034) has its own modified composition (including aluminium and other controls) and is not represented by this row.
Designations & Related Materials
| Name / material | Relationship |
|---|---|
| Alloy 31 / UNS N08031 / 1.4562 | Core wrought alloy (this page) |
| X1NiCrMoCu32-28-7 | EN name for N08031 (with standard/condition caveat) |
| VDM Alloy 31 / Nicrofer 3127 hMo | Producer/trade designation for N08031 — verify product origin before branded-supply claims |
| Alloy 31 Plus / N08034 / 2.4692 | Separate related alloy with its own chemistry, processing and property data — not an automatic upgrade/substitute for 31 |
| FM 31 / FM 31 Plus | Welding consumables, not wrought base-alloy grades |
| Alloy 28, Alloy 20, 904L, 6Mo, C-series | Comparator alloys, not Alloy 31 grades |
Matching UNS or a trade name alone does not establish identical dimensions, tests, manufacturing route or code approval. Designations are cross-references and related materials, not substitution approvals; no “31L / 31H” grades are invented, and 31 Plus data is used only from its own source where that alloy is offered.
Mechanical Properties (solution-annealed reference)
| Property (annealed) | Reference value |
|---|---|
| Tensile strength | ≥650 MPa |
| 0.2% proof stress | ≥276 MPa |
| Elongation | ≥40% |
| Hardness | ≤100 HRB (typical annealed) |
Indicative solution-annealed values; the exact figures depend on product form, size, condition and the governing specification edition, and typical producer data are separate from contractual minima. Confirm form (plate/sheet, bar, pipe/tube, forgings, wire, fasteners), size interval, condition and test basis on the certificate. Elevated-temperature, cold-worked, impact, fatigue and creep data are supplied where relevant with their conditions; typical tensile strength is not a design allowable and pressure-code allowable stresses reference the code, edition, form and temperature.
Physical Properties & PREN
| Property | Reference value |
|---|---|
| Density | 8.05 g/cm³ at 20°C (producer reference) |
| Melting range | ~1320–1355°C (approx.) |
| Young’s modulus | ~195 GPa (20°C) |
| Magnetic response | Austenitic; low permeability (annealed) |
| PREN (screening index) | Cr + 3.3×Mo + 16×N ≈ 51.7; or with 30×N ≈ 54.5 (at nominal 27Cr / 6.5Mo / 0.20N) |
Producer reference values near ambient; the melting range is not a service temperature. PREN is a screening index, not a measured corrosion rate, a guaranteed critical pitting temperature, an SCC rating or an acid-resistance metric — the “≈54” figure corresponds to the 30×N convention, and the value depends on the equation and the actual heat chemistry (use heat analysis for a heat-specific PREN, and the same formula when comparing 904L or other alloys). Thermal conductivity, specific heat, thermal-expansion coefficient (with interval) and resistivity with temperature are provided on enquiry.
Standards by Product Form
| Product | Reference | Boundary |
|---|---|---|
| Plate / sheet / strip | ASTM B625 | Exact grade, edition and condition |
| Bar / wire | ASTM B649 (B581 rod route if applicable) | By scope and edition |
| Seamless pipe / tube | ASTM B622; EN 10216-5 (seamless tube) | Confirmed grade and delivery requirements; EN 10216-5 is a seamless-tube reference, not a family label |
| Welded pipe / welded tube | ASTM B619 (pipe) / B626 (tube) | Distinct routes; class, examination and heat treatment stated |
| Wrought fittings | ASTM B366 material + B16.9 geometry | Grade/class and manufacturing requirements |
| Forgings / flanges | ASTM B564 material + B16.5 geometry/rating | N08031 is within B622/B564 scope; confirm ordered edition |
| Fasteners | Material condition + dimensional/thread/testing requirements | — |
These ASTM routes are current (not withdrawn) — B622 and B564 include N08031 — but the exact ordered revision and scope are verified per order, since catalogue abstracts can lag scope changes. Record ASME SB adoption and code eligibility independently. The producer material sheet is VdTÜV 509 (not 505); VdTÜV coverage is not a universal certification for all products. Rename designation “equivalents” as cross-references, and there is no “B622-style” compliance — state the exact standard, edition, form and condition.
Available Forms, Sizes & Availability
Availability is confirmed per enquiry with stocked / sourced / made-to-order status — the ranges below are indicative and verified against supply records per order.
| Form | Size range (indicative) | Wall / thickness / rating | Route |
|---|---|---|---|
| Seamless pipe | 1/8" – 12" NPS | Specified schedule / wall; S schedules and STD/XS/XXS are not one continuous series | B36.10M dims; B622 material |
| Welded pipe | to ~16" where offered | Specified wall | B619 material |
| Tube (OD × wall) | 6–50 mm OD (tube OD is not NPS) | 1–6 mm wall; avg- or min-wall basis stated | B622 / B626 / EN 10216-5 |
| Flanges | Class 150–1500 | Facing / bore / rating per class | B16.5 dims; B564 material |
| Bar / plate | bar 6–200 mm; plate 2–50 mm | Solution-annealed | B649 (bar) / B625 (flat) |
The ~16" welded and 12" seamless figures are route-dependent, not a contradiction. Class is a flange pressure class, not psi. Keep dimensional standards (B36.10 / B36.19) separate from material qualification; mark undefined size/schedule combinations rather than interpolate. See the schedule chart and weight calculator.
Corrosion & Temperature
Welding, Heat Treatment & Fabrication
Testing & Documentation
| Item | Basis |
|---|---|
| Heat chemistry (incl. N) | Laboratory analysis; nitrogen by suitable method — handheld PMI confirms major elements only and cannot measure nitrogen or prove heat treatment |
| Intergranular corrosion | ASTM G28 Method A (VDM-reported) — state method/edition, specimen condition, duration and acceptance; not a universal pass or a service-life guarantee |
| Pitting / crevice | ASTM G48 method and basis where ordered |
| Tensile / hardness / NDE | Per ordered specification, form and condition |
| Certification | EN 10204 3.1 or 3.2 (3.2 needs the agreed independent validation; not every listed test is automatically included) |
IGC testing and calculated PREN do not establish service life. Specify supplementary tests, corrosion method/acceptance and certificate type at ordering.
Applications & Industries Served
Map the component and fluid to the material: acid coolers/heat exchangers, absorber and scrubber internals, seawater piping and process vessels. The correct form and condition depend on the specific medium, concentration, temperature and stress — not the industry label.
Product Range
The alloy 31 range can be supplied with related pipes, tubes, butt weld fittings, forged fittings, flanges, fasteners and custom fabricated items where required by the BOQ.
Applications
For dimensional references, see the Pipe Schedule & Fittings Guide. For related supply, review Pipes & Tubes, Butt Weld Fittings, Forged Fittings and Flanges.
Types of Products
| Type | Description |
|---|---|
| Pipes & Tubes | Seamless, welded and large-diameter supply |
| Fittings | Butt weld, forged and fabricated fittings |
| Flanges | Forged flanges and special machined items |
| Plates / Bars / Round Bars | Subject to grade and project availability |
Available Forms
Related Pages
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Frequently Asked Questions
Is Alloy 31 the same as Nicrofer 3127 hMo and UNS N08031?
Yes — UNS N08031 (Werkstoff 1.4562, X1NiCrMoCu32-28-7) is the super-austenitic alloy marketed as Nicrofer 3127 hMo. It is a 6–7Mo grade with copper and nitrogen additions. We identify material by UNS N08031 and the applicable specification; a branded name does not mean every generic N08031 item was made by that producer.
What is the difference between Alloy 31 and Alloy 31 Plus?
They are separate grades. Alloy 31 is UNS N08031 / 1.4562. Alloy 31 Plus is UNS N08034 / Werkstoff 2.4692, a further-developed variant with higher molybdenum and manganese and modified nitrogen — it is not an alias for Alloy 31, has its own composition limits and specifications, and must be ordered by its own UNS. Confirm which grade a drawing or datasheet actually requires.
What is the PREN of Alloy 31 and how is it calculated?
PREN is a screening index, not a service rating. Using PREN = Cr + 3.3×Mo + 16×N, Alloy 31 is roughly 50–52; with the 30×N nitrogen coefficient sometimes used for high-nitrogen grades it reaches roughly 54–55. The exact figure depends on the actual heat chemistry and the coefficient chosen, so it should be presented as an index range rather than a single guaranteed number, and pitting resistance is confirmed by the relevant corrosion test (for example ASTM G48 or G28) for the service.
Which specifications and standards apply to Alloy 31?
N08031 is an active grade covered by ASTM references such as B625 (plate/sheet/strip), B649 (bar), B622/B619/B626 (seamless/welded pipe and tube), B366 (fittings) and B564 (forgings), by EN 10216-5 for seamless tube and by VdTÜV Werkstoffblatt 509. These are current, not withdrawn — there is no “B622-style” substitute; the exact specification, edition and product form are confirmed per order with EN 10204 3.1 or 3.2 documentation.
How does Alloy 31 perform in sulphuric and phosphoric acid?
Alloy 31 was developed for hot, contaminated sulphuric and phosphoric acid and for high-chloride media, and resists pitting, crevice corrosion and chloride stress-corrosion cracking well. Performance still depends on concentration, temperature, aeration, impurities, velocity and weld condition, so it is confirmed against a concentration–temperature corrosion map for the actual fluid rather than treated as suitable at all concentrations and temperatures.
What welding and heat treatment does Alloy 31 need?
Alloy 31 is solution annealed around 1150–1180°C followed by rapid cooling; the exact cycle is form- and producer-specific. For welding, an over-alloyed filler (for example a nickel-base consumable of the FM 31 / higher-Mo type) is normally qualified to preserve corrosion resistance in the weld and heat-affected zone. Weld procedures and consumables are qualified for the intended service.
What information is needed for a quotation?
Provide the product form, dimensions and tolerances, quantity, condition (solution annealed), the exact specification and edition, service chemistry, concentration and temperature, required testing (for example G28 Method A intergranular corrosion), traceability and certificate type (EN 10204 3.1 or 3.2), finish and delivery location. Availability and the accepted specification route are confirmed with the quotation. Sagiant is an independent supplier and stockist, not the alloy producer.
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