ASTM B622 — Seamless Nickel and Nickel-Cobalt Alloy Pipe and Tube
ASTM B622 (latest edition: B622-22) covers seamless nickel and nickel-cobalt alloy pipe and tube for severe corrosion and elevated-temperature service. ASME SB-622 is adopted in BPVC Section II Part B. B622 is the seamless pipe/tube counterpart to ASTM B474 (EFW) and covers complex high-alloy grades including Hastelloy C-276, C-22, B-2, B-3 and Incoloy 825.
1. Scope
B622 applies to pipe and tube in outside diameters from approximately 6 mm to 600 mm. Unlike ASTM B444 (which is specific to Alloy 625) and ASTM B161/B165 (pure nickel/Monel), B622 focuses on complex nickel alloys with high molybdenum content for maximum corrosion resistance. All pipe/tube must be seamless — no weld seam. Products are furnished in the annealed condition.
2. Grades and UNS Designations
| UNS No. | Trade Name | Alloy System | Primary Advantage |
| N10276 | Hastelloy C-276 | Ni-16Cr-16Mo-4W | Broadest acid resistance; FGD, mixed acids, HCl |
| N06022 | Hastelloy C-22 | Ni-22Cr-14Mo-3W | Better oxidising environments; chlorine, bleach |
| N06455 | Hastelloy C-4 | Ni-16Cr-16Mo | C-276 without W; good thermal stability |
| N10665 | Hastelloy B-2 | Ni-28Mo | Outstanding HCl / non-oxidising acid resistance |
| N10675 | Hastelloy B-3 | Ni-28Mo-1.5Cr | Improved thermal stability vs B-2; same acid resistance |
| N06002 | Hastelloy X | Ni-22Cr-9Mo-18Fe | High-temperature strength + oxidation; gas turbines |
| N06030 | Alloy G-30 | Ni-30Cr-5Mo-2.5W-1.5Cu | Wet phosphoric acid, H₂SO₄/HNO₃ mixtures |
| N08825 | Incoloy 825 | Ni-21Cr-3Mo-2.5Cu-Ti | H₂SO₄, H₃PO₄, seawater; cost-effective |
3. Chemical Composition
| UNS / Grade | Ni (min) | Cr | Mo | Fe | Others |
| N10276 C-276 | Balance | 14.5–16.5 | 15.0–17.0 | 4.0–7.0 | W 3.0–4.5, Co ≤2.5, C ≤0.01 |
| N06022 C-22 | Balance | 20.0–22.5 | 12.5–14.5 | 2.0–6.0 | W 2.5–3.5, Co ≤2.5, C ≤0.015 |
| N10665 B-2 | Balance | 1.0 max | 26.0–30.0 | 2.0 max | Co ≤1.0, C ≤0.02 |
| N10675 B-3 | Balance | 1.0–3.0 | 27.0–32.0 | 1.0–3.0 | Mn ≤3.0, C ≤0.01 |
| N06002 Alloy X | Balance | 20.5–23.0 | 8.0–10.0 | 17.0–20.0 | Co 0.5–2.5, W 0.2–1.0 |
| N08825 825 | 38.0–46.0 | 19.5–23.5 | 2.5–3.5 | 22.0 min | Cu 1.5–3.0, Ti 0.6–1.2 |
4. Mechanical Properties
| Grade | UTS min (MPa) | YS min (MPa) | Elong. min (%) |
| Hastelloy C-276 | 690 | 280 | 40 |
| Hastelloy C-22 | 690 | 310 | 45 |
| Hastelloy B-2 | 690 | 310 | 40 |
| Hastelloy B-3 | 760 | 345 | 40 |
| Hastelloy X | 655 | 240 | 35 |
| Incoloy 825 | 586 | 241 | 30 |
5. Heat Treatment
| Grade | Anneal Temp (°C) | Cooling |
|---|
| C-276 / C-22 / C-4 | 1065–1175 | Rapid water quench or rapid air cool |
| B-2 | 1065–1175 | Rapid water quench — must avoid 600–900 °C range (Ni₄Mo precipitation) |
| B-3 | 1065–1175 | Water quench; B-3 improved stability vs B-2 |
| Alloy X | 1165–1190 | Rapid air cool or water quench |
| Incoloy 825 | 930–980 | Water quench or rapid cool |
B-2 thermal sensitivity: Hastelloy B-2 is susceptible to precipitation of ordered Ni₄Mo phase in the 600–900 °C range, causing embrittlement and loss of corrosion resistance. B-3 was developed to address this — its slightly higher Mn content (1.0–3.0%) widens the safe processing window. For service with PWHT or slow cool-down, B-3 is more reliable than B-2.
6. Testing Requirements
| Test | Requirement |
|---|
| Tensile | One per heat or heat-treatment lot |
| Hardness | Spot check per lot |
| Hydrostatic | Each pipe/tube length; or eddy current as agreed |
| Chemical Analysis | One ladle per heat; PMI (XRF) strongly recommended |
| Visual & Dimensional | 100%; OD/wall tolerances per B622 Table |
7. Related Standards
| Standard | Description |
|---|
| ASTM B444 / ASME SB-444 | Inconel 625 (N06625) seamless pipe and tube |
| ASTM B474 / ASME SB-474 | Electric fusion-welded nickel alloy pipe (B622 complement for large diameter) |
| ASTM B366 / ASME SB-366 | Wrought nickel alloy butt-welding fittings |
| ASTM B564 / ASME SB-564 | Nickel alloy forgings (flanges, nozzles) |
HT PIPE supplies ASTM B622 seamless nickel alloy pipe and tube in Hastelloy C-276, C-22, and Incoloy 825 with EN 10204 3.1 and full PMI certification. Contact us for corrosive service material selection guidance.
