What Is UNS N04400 Material?
UNS N04400 is the standard designation for the 63Ni-28Cu nickel-copper alloy. It is a single-phase solid-solution material: the copper dissolves fully in the nickel matrix, no precipitation hardening is possible, and strength can therefore be raised only by cold working. In the annealed condition the alloy combines medium-to-high strength with good ductility and weldability.
One property drives most of its specification history. The alloy resists fast-flowing seawater, salt solutions and alkaline media, and it resists chloride stress corrosion cracking, which is the reason it appears so often in marine, refinery and chemical plant piping.
Chemical Composition and ASTM Specifications
The table below gives the standard chemical analysis range that every ASTM product specification for this grade refers back to.
| Element | Composition, % |
|---|---|
| Nickel (Ni) | 63.0 min |
| Copper (Cu) | 28.0-34.0 |
| Iron (Fe) | 2.50 max |
| Manganese (Mn) | 2.00 max |
| Silicon (Si) | 0.50 max |
| Carbon (C) | 0.30 max |
| Sulphur (S) | 0.024 max |
Each product form is covered by its own ASTM specification, and the test schedule follows the form rather than the grade name.
| Product form | ASTM specification |
|---|---|
| Seamless pipe | ASTM B165 |
| Welded pipe | ASTM B725 |
| Seamless tube | ASTM B163 |
| Welded tube | ASTM B626 |
| Sheet, plate and strip | ASTM B127 |
| Rod, bar and wire | ASTM B164 |
| Forgings | ASTM B564 |
| Fittings and flanges | ASTM B366 |
Matching the specification to the form matters. Tube supplied to ASTM B163 is tested for seamless tube duty such as heat exchanger and condenser service, whereas plate to ASTM B127 is ordered for clad vessel and scrubber construction. A purchase order that names only the grade, without the form specification, leaves the supplier free to apply the wrong test schedule.
Grade Equivalents Across Standards Systems
International designations for this grade are listed below so that imported and domestic material can be cross-referenced quickly.
| System | Designation |
|---|---|
| UNS | N04400 |
| Werkstoff number | 2.4360 |
| EN | NiCu30Fe |
| AFNOR | NU-30M |
| JIS | NW 4400 |
| BS | NA 13 |
| GOST | MNZhMts 28-2.5-1.5 |
Physical and Mechanical Data
| Property | Typical value |
|---|---|
| Density | 8.80 g/cm³ |
| Melting range | 1300-1350 °C |
| Maximum continuous service temperature | about 480 °C |
| Tensile strength, annealed bar | about 550 MPa |
| 0.2% yield strength, annealed bar | about 240 MPa |
| Elongation, annealed bar | about 50% |
| Hardening mechanism | cold work only |
Available Mill Forms and Fabrication
Sheet, plate and strip for vessels, cladding and scrubber internals.
Rod, bar and wire for fasteners, machined shafts and welding consumables.
Seamless and welded tube for heat exchangers, condensers and reboilers.
Seamless and welded pipe for process and seawater transfer lines.
Fittings, flanges and forged components for pressure piping assemblies.
Machining is comparable to austenitic stainless steel but the alloy tends to work harden, so heavy depths of cut with positive feeds are preferred over light repeated passes. Welding is straightforward using matching nickel-copper filler; no post-weld heat treatment is needed because the alloy does not respond to thermal hardening.
Frequently Asked Questions
Q: What is UNS N04400 material made of?
It is a nickel-copper alloy with a minimum of 63% nickel, 28-34% copper and no more than 2.50% iron, with manganese, silicon, carbon and sulphur held to the limits set by the ASTM specifications.
Q: What is the melting point of UNS N04400?
The melting range is 1300-1350 °C. The alloy keeps useful mechanical properties from sub-zero temperatures up to a maximum continuous service temperature of roughly 480 °C.
Q: Can UNS N04400 be hardened by heat treatment?
No. It is a solid-solution alloy and responds only to cold working. Any strength increase from cold reduction is accompanied by a loss of ductility and must be accounted for in subsequent forming.
Q: Does UNS N04400 resist seawater?
Yes. It is one of the few alloys that withstands fast-flowing seawater and brackish water with low corrosion rates, and it also resists chloride stress corrosion cracking, which is why it is widely used for marine piping and pump shafts.
Q: How does UNS N04400 behave in acids?
It performs well in deaerated sulphuric and hydrofluoric acid, but corrosion accelerates sharply when the acid is aerated or contains oxidizing salts. It must not be used in nitric acid or in ammonia service.
Q: Which specification should be quoted on a purchase order?
Quote the specification for the product form, not the grade alone: ASTM B165 for seamless pipe, B163 for seamless tube, B626 for welded tube, B127 for plate and sheet, B164 for bar and B564 for forgings.
