How the Designations Are Built
Most trading confusion comes from treating these as interchangeable. The UNS number and the W.Nr. both identify an alloy’s chemistry. An ASTM or ASME number identifies a product specification, such as plate or seamless pipe, and the same alloy appears in several of them.
The Numbering Systems at a Glance
| System | Example | What it identifies |
|---|---|---|
| Trade name | Inconel 625 | A producer’s brand for the alloy |
| Generic name | Alloy 625 | The same chemistry without the brand |
| UNS | N06625 | The alloy’s chemistry, one letter and five digits |
| W.Nr. | 2.4856 | The European material number |
| EN symbolic name | NiCr22Mo9Nb | The chemistry written out as elements |
| Forging grade | F53, F55 | A grade within ASTM A182 forgings |
| Product specification | ASTM B443, ASME SB-443 | Requirements for one product form |
The complete list is in the equivalent grade chart and the W.Nr. reference.
Names That Are Often Mixed Up
- “Inconel 825” is Incoloy 825, UNS N08825, an iron-nickel alloy with about 30% iron. 825 vs 625
- “Monel 500” is shorthand for Monel K-500, UNS N05500. 400 vs K-500
- S31803 and S32205 are both Duplex 2205. S32205 has tighter limits.
- “Hastelloy C” on old paperwork may mean C-276, C-22 or an obsolete grade. Read the chemistry. C-22 vs C-276
FAQ
What is the UNS number for Inconel 625?
N06625. Its W.Nr. is 2.4856, and it is also traded as Alloy 625.
Is Alloy 22 the same as Hastelloy C-22?
Yes. Alloy 22 is the generic name for Hastelloy C-22, UNS N06022, W.Nr. 2.4602.
What is F53?
F53 is the ASTM A182 forging designation for super duplex 2507, UNS S32750. F55 is the forging designation for S32760.
What does the 2.4 at the start of a W.Nr. mean?
Material numbers starting with 2 are heavy non-ferrous metals, and 2.4 is the nickel alloy group. Steels start with 1 (stainless with 1.4) and light metals such as titanium with 3.
Why should a lot description use the UNS number?
Trade names vary between producers and countries, and some are misused, such as “Inconel 825” for Incoloy 825. The UNS number identifies the chemistry without ambiguity. See how UNS numbers work.