ASTM B366
Factory-made wrought nickel and nickel-alloy fittings
Covers factory-made wrought nickel and nickel-alloy fittings — elbows, tees, reducers, caps and stub ends — with grade designations such as WPNICMC (825), WPNCMC (625), WPHC276 and WPNC (Monel 400).
- Pipe fittings
- ASME SB-366
- 7 grades supplied to it
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is ASTM B366?
ASTM B366 is the specification for factory-made wrought nickel and nickel-alloy pipe fittings — the buttweld elbows, tees, reducers and caps used with nickel-alloy pipe. Grades are named by the alloy: WPNICMC for Alloy 825, WPNCMC for Alloy 625, WPHC276 for C276 and WPNC for Monel 400. Dimensions follow ASME B16.9. ASME adopts it as SB-366.
ASTM B366 at a glance
| Products | Wrought buttweld fittings |
|---|---|
| Material family | Nickel and nickel alloys |
| Dimensions | ASME B16.9 (and MSS SP-43 for light wall) |
| ASME designation | SB-366 |
ASTM B366 grade designations
The B366 grade name is what appears on the fitting and the certificate.
| Alloy | UNS | B366 grade |
|---|---|---|
| Alloy 825 | N08825 | WPNICMC |
| Alloy 625 | N06625 | WPNCMC |
| Alloy 600 | N06600 | WPNCI |
| Hastelloy C276 | N10276 | WPHC276 |
| Hastelloy C22 | N06022 | WPHC22 |
| Monel 400 | N04400 | WPNC |
How to write ASTM B366 on a purchase order
Name the product, size, material specification and grade, the dimensional standard and the certificate. An example line:
Illustrative only — sizes, tests, inspection level and any project values come from your purchase specification.
ASTM B366 edition and verification status
Which edition we have confirmed, and what is still being checked before any numerical requirement is published here.
| Current edition (publisher listing) | B366/B366M-25 — checked 7 October 2026 |
|---|---|
| Full-text verification | In progress — numerical requirements are published here only after the current text has been reviewed |
| Edition on your order | The edition named in your purchase order or design code governs — confirm it with your enquiry |
What to know before ordering to ASTM B366
The points that decide whether material to ASTM B366 is accepted at inspection.
- The grade name tells you the alloy: WPNICMC is Alloy 825.
- Fittings are made from pipe, plate or bar to the matching nickel-alloy product specification.
- Dimensions follow ASME B16.9 or MSS SP-43.
Grades and products we supply to ASTM B366
| Grade | Product | Designation on the certificate |
|---|---|---|
| Inconel 825 | Fittings | ASTM B366 WPNICMC |
| Inconel 600 | Fittings | ASTM B366 WPNCI |
| Inconel 625 | Fittings | ASTM B366 WPNCMC |
| Incoloy 800 / 800H / 800HT | Fittings | ASTM B366 WPNIC |
| Hastelloy C276 | Fittings | ASTM B366 WPHC276 |
| Hastelloy C22 | Fittings | ASTM B366 WPHC22 |
| Monel 400 | Fittings | ASTM B366 WPNC |
How ASTM B366 fits into an order
A purchase order line is only complete when it names the material standard, the dimensional standard and the inspection document. Miss one and the mill, the inspector and the buyer can each read the order differently.
Standards used with ASTM B366
Same family
ASTM B366 — questions buyers ask
What is ASTM B366?
ASTM B366 is the specification for factory-made wrought nickel and nickel-alloy pipe fittings — the buttweld elbows, tees, reducers and caps used with nickel-alloy pipe. Grades are named by the alloy: WPNICMC for Alloy 825, WPNCMC for Alloy 625, WPHC276 for C276 and WPNC for Monel 400. Dimensions follow ASME B16.9. ASME adopts it as SB-366.
What is WPNICMC?
The ASTM B366 grade designation for Alloy 825 (UNS N08825) fittings.
What is the difference between B366 and B564?
B366 covers wrought buttweld fittings; B564 covers forgings — flanges and forged socket-weld or threaded fittings.
Is 904L ordered to B366?
No. 904L buttweld fittings are ordered to ASTM A403 WP904L (or CR904L for MSS SP-43).
Which grades do you supply to ASTM B366?
Inconel 825, Inconel 600, Inconel 625, Incoloy 800 / 800H / 800HT, Hastelloy C276, Hastelloy C22, Monel 400 — see the table on this page for the exact product and designation.
What is the current edition of ASTM B366?
The publisher's listing checked on 7 October 2026 shows B366/B366M-25 as the current edition. The edition that governs an order is the one named in the purchase order or design code. Full-text review of the current edition is in progress, so numerical requirements are not published on this page yet.
Do you supply certificates to this standard?
Yes. Material is supplied with mill test certificates to EN 10204 3.1 showing the standard, grade and heat number; 3.2 with third-party inspection on request.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026