Alloy 825 standards: B424, B423, B366, B564 and the rest
Alloy 825 (UNS N08825) is ordered to a different ASTM standard for each product: B424 for plate, sheet and strip, B423 for seamless pipe and tube, B705 for welded pipe, B366 WPNICMC for buttweld fittings, B564 for flanges and forgings and B425 for bar. ASME adopts each as SB-424, SB-423 and so on.
One alloy, many specifications
ASTM writes its nickel-alloy specifications by product form, not by alloy. That means the same heat of Alloy 825 can end up certified to half a dozen standards depending on whether it becomes plate, pipe, a fitting or a flange. The chemistry limits are the same across them; what changes is the manufacturing route, the testing and the tolerances.
Inconel 825 at a glance
The complete list
| Product | ASTM | ASME | General requirements |
|---|---|---|---|
| Plate, sheet, strip | B424 | SB-424 | B906 |
| Seamless pipe & tube | B423 | SB-423 | B829 |
| Welded pipe | B705 | SB-705 | B775 |
| Heat-exchanger tube | B163 | SB-163 | B829 |
| Buttweld fittings | B366 WPNICMC | SB-366 | — |
| Flanges & forgings | B564 | SB-564 | — |
| Rod & bar | B425 | SB-425 | — |
Dimensional standards sit on top of these: ASME B36.19 for pipe schedules, B16.9 for buttweld fittings, B16.11 for forged fittings and B16.5 / B16.47 for flanges.
What each standard controls
- B424 — chemistry, mechanical properties and annealed condition for flat products; tolerances come from B906.
- B423 — seamless pipe and tube, cold-worked or hot-finished, then annealed; hydrostatic or electric testing of each length.
- B705 — welded pipe in classes that define cold work and weld-bead treatment.
- B366 — fittings made from B423 pipe, B424 plate or B425 bar, marked WPNICMC.
- B564 — forgings, including weld neck, slip-on and blind flanges, supplied annealed.
What to write on the order
A complete Alloy 825 line item names the product standard, the UNS number, the dimensional standard and the certificate — for example: "Pipe, seamless, ASTM B423 UNS N08825, 4" Sch 40S to ASME B36.19, 6 m random, EN 10204 3.1." Adding the UNS number avoids confusion between trade names (Inconel 825, Incoloy 825, Nicrofer 4221) that all refer to the same alloy.
Sour service
Alloy 825 is listed in NACE MR0175 / ISO 15156 for H₂S-containing environments within limits of temperature, chloride and H₂S partial pressure. If your line is sour, say so at enquiry so the compliance statement and any hardness limits are covered.