ASTM B474 — Electric Fusion-Welded Nickel and Nickel Alloy Pipe
ASTM B474 (latest edition: B474-22) covers nickel and nickel alloy pipe produced by electric fusion welding (EFW) of flat-rolled plate or sheet. ASME SB-474 is adopted in BPVC Section II Part B. B474 EFW pipe is the large-diameter counterpart to seamless ASTM B622 pipe — used when seamless manufacture is impractical or unavailable for sizes NPS 2 and above. Applications include FGD absorbers, chemical reactors, heat exchanger shells, and offshore piping in highly corrosive environments.
1. Manufacturing Process
ASTM B474 pipe is formed by rolling nickel alloy plate to a cylinder and joining the longitudinal seam by one of the following welding processes: GTAW (Gas Tungsten Arc Welding), GMAW (Gas Metal Arc Welding), or SAW (Submerged Arc Welding). The weld seam must be free of additions of dissimilar filler unless agreed. 100% radiographic inspection (RT) of the full weld seam is mandatory under B474.
2. Grades Covered
| UNS No. |
Trade Name |
Alloy System |
Key Application |
| N02200 |
Nickel 200 |
Pure Ni |
Caustic soda vessels, HF scrubbers |
| N02201 |
Nickel 201 |
Low-C pure Ni |
Caustic >300 °C; no graphite precipitation |
| N04400 |
Monel 400 |
Ni-Cu |
HF alkylation, seawater desalination |
| N06600 |
Inconel 600 |
Ni-Cr-Fe |
High-temperature oxidising, nuclear |
| N06625 |
Inconel 625 |
Ni-Cr-Mo-Nb |
Versatile: seawater, sour gas, cryogenic |
| N10276 |
Hastelloy C-276 |
Ni-Mo-Cr-W |
FGD absorbers, mixed-acid environments |
| N06022 |
Hastelloy C-22 |
Ni-Cr-Mo-W |
Oxidising chloride, Cl₂ handling, bleach |
| N10665 |
Hastelloy B-2 |
Ni-Mo |
HCl (non-oxidising), H₂SO₄ reducing |
| N08825 |
Incoloy 825 |
Ni-Fe-Cr-Mo-Cu |
H₂SO₄, sour gas, cost-effective Ni alloy |
3. Chemical Composition (Key Grades)
| Grade / UNS |
Ni |
Cr |
Mo |
Fe max |
Others |
| N02200 |
≥99.0 |
— |
— |
0.40 |
C ≤0.15 |
| N04400 |
63.0 min |
— |
— |
2.50 |
Cu 28–34 |
| N06625 |
58.0 min |
20.0–23.0 |
8.0–10.0 |
5.0 |
Nb+Ta 3.15–4.15 |
| N10276 |
Balance |
14.5–16.5 |
15.0–17.0 |
4.0–7.0 |
W 3.0–4.5 |
| N06022 |
Balance |
20.0–22.5 |
12.5–14.5 |
2.0–6.0 |
W 2.5–3.5 |
4. Mechanical Properties
| Grade |
UTS min (MPa) |
YS min (MPa) |
Elong. min (%) |
| Nickel 200 / 201 |
380 |
105 |
35 |
| Monel 400 |
485 |
170 |
35 |
| Inconel 625 |
690 |
275 |
30 |
| Hastelloy C-276 |
690 |
280 |
40 |
| Hastelloy C-22 |
690 |
310 |
45 |
| Incoloy 825 |
586 |
241 |
30 |
5. NDE and Quality Requirements
| Test |
Requirement |
| Weld Seam RT |
100% radiographic inspection of full seam length (mandatory) |
| Tensile |
One per heat; cross-weld tensile when weld efficiency < 1.0 |
| Hydrostatic |
Each pipe length |
| Chemical Analysis |
One ladle per heat; PMI (XRF) strongly recommended |
| Visual & Dimensional |
100%; OD, wall, straightness per B474 tolerances |
Weld joint efficiency: Under ASME BPVC Section VIII Div.1, EFW pipe with full RT qualifies for joint efficiency E = 1.0 (same as seamless), allowing the thinnest permitted wall for a given pressure. Without RT, only E = 0.85 is permitted for spot-radiographed or E = 0.70 for unradiographed longitudinal welds.
6. B474 vs B622 — Comparison
| Parameter |
B474 (EFW) |
B622 (Seamless) |
| Manufacturing method |
Plate rolled + longitudinal weld |
Hot/cold extrusion or piercing |
| Available sizes |
NPS 2–60+ |
OD up to ~600 mm (size-limited by extrusion) |
| Wall uniformity |
Good (from rolled plate) |
Excellent (no weld deviation) |
| Weld seam |
Visible; must be RT-inspected |
None |
| BPVC joint efficiency |
E = 1.0 with full RT |
E = 1.0 always |
| Cost (relative) |
Lower for large diameters |
Lower for small diameters |
7. Related Standards
| Standard |
Description |
| ASTM B622 / ASME SB-622 |
Seamless nickel alloy pipe and tube (companion seamless spec) |
| ASTM B444 / ASME SB-444 |
Inconel 625 seamless pipe and tube |
| ASTM B366 / ASME SB-366 |
Wrought nickel alloy butt-welding fittings |
| ASTM B564 / ASME SB-564 |
Nickel alloy forgings (flanges) |
HT PIPE supplies ASTM B474 EFW nickel alloy pipe in Alloy 625, C-276, C-22, and Incoloy 825 with 100% RT weld inspection and EN 10204 3.1 MTR. Contact us for large-diameter custom sizes.
