Project Description
Monel 400 / UNS N04400 is a classic solid-solution nickel-copper alloy containing nominally 67% Ni and 31.5% Cu, strengthened exclusively through cold working rather than precipitation hardening. Its exceptional resistance to seawater, brackish water, hydrofluoric acid, sulfuric acid, and alkalis — combined with good mechanical properties from cryogenic temperatures up to 480 °C — has made it a staple of the oil & gas industry for over a century. SHUNFU METAL supplies Monel 400 round bar, forged bar, and flat bar melted from VIM + VAR stock, produced to ASTM B164 with EN 10204 3.1 mill test certificates.
Monel 400 — Overview
Monel 400 belongs to the Ni-Cu binary alloy family and ranks among the most corrosion-resistant alloys commercially available. Its solid-solution microstructure delivers a unique combination of strength, ductility, and toughness maintained all the way down to liquid-nitrogen temperatures — an attribute that sets it apart from most other nickel alloys. The alloy is highly resistant to rapidly flowing seawater and brackish water, making it ideal for offshore and subsea hardware where galvanic protection and chloride-induced stress corrosion cracking (SCC) resistance are paramount.
In reducing acid environments — including de-aerated hydrofluoric (HF) acid and dilute sulfuric acid — Monel 400 outperforms most stainless steels and many other nickel alloys. It also resists neutral and alkaline salt solutions and shows good performance in steam and superheated steam service. Its moderate magnetism at room temperature (due to the NiCu solid solution) is a minor characteristic that has no practical impact in most oilfield applications.
At SHUNFU METAL, all Monel 400 heat lots undergo optical emission spectrometry (OES) chemical re-verification at intake. Bar stock is either hot-rolled or open-die forged from VIM+VAR remelt ingots, ensuring a clean, low-inclusion microstructure that is critical for downhole service. Dimensional tolerances are held to h11/h9 on cold-drawn bar.
Monel 400 Equivalent Grades & Standards
| Standard Body | Designation | Scope / Form |
|---|---|---|
| UNS (USA) | N04400 | All product forms |
| ASTM (USA) | B164 (bar/rod), B127 (plate), B165 (tube), B564 (forging) | Bar, plate, tube, forging |
| ASME (USA) | SB-164, SB-127, SB-165, SB-564 | Pressure vessel / boiler code |
| AMS (USA) | AMS 4675 (bar/forging), AMS 4544 (sheet/strip), AMS 4574 (tube), AMS 4730 (wire) | Aerospace-quality bar & forging |
| DIN / W.Nr. (Germany) | 2.4360 (NiCu30Fe) / 2.4361; DIN 17743, DIN 17750–17754 | Rod, sheet, strip, tube, forging |
| EN / ISO | NW4400 (ISO 9723/9724); NiCu30Fe (EN designation) | International equivalent |
| BS (UK) | NA13; BS 3072–3076 | Sheet, strip, bar, wire, tube |
| JIS (Japan) | NW4400 | Bar, plate, tube |
| GOST (Russia) | МНЖМц 28-2.5-1.5 (NCu28-2.5-1.5) | Nearest equivalent |
| NACE / ISO 15156 | MR-0175 / ISO 15156-3 | Sour service qualification |
Oil & Gas Applications — Monel 400 Components
Supply Forms & Size Range — Monel 400 Bar
SHUNFU METAL’s Monel 400 bar is produced from VIM+VAR remelt heats. Each coil or bloom is hot-worked, annealed, pickled, and then finish-rolled or cold-drawn to order. Final inspection includes OES chemistry check, hardness survey, and ultrasonic testing (UT) per ASTM E428 for sizes above Ø25 mm.
| Product Form | Standard | Size Range | Condition |
|---|---|---|---|
| Hot-Rolled Round Bar | ASTM B164 | Ø 10 – 250 mm | Annealed / Hot-finished |
| Cold-Drawn Round Bar | ASTM B164 | Ø 3 – 80 mm | Cold-drawn / Stress-relieved |
| Forged Round Bar | ASTM B564 / AMS 4675 | Ø 80 – 650 mm | Forged + annealed |
| Hot-Rolled Flat Bar | ASTM B164 | Thickness 5–80 mm × Width 20–300 mm | Annealed |
| Forged Flat / Block | ASTM B564 | T 20–300 mm × W 50–600 mm | Forged + annealed |
| Hexagon Bar | ASTM B164 | A/F 8 – 100 mm | Hot-rolled / Cold-drawn |
Standard bar lengths: 1,000–6,000 mm; cut-to-length available. Custom forgings (discs, rings, blocks) accepted to drawing. EN 10204 3.1 MTC supplied as standard; NACE MR-0175 certification on request.
Chemical Composition — Monel 400 (ASTM B164 / UNS N04400)
| Element | Min % | Max % | Role |
|---|---|---|---|
| Ni + Co | 63.0 | — | Base element; corrosion resistance matrix |
| Cu | 28.0 | 34.0 | Resistance to HF, seawater, reducing acids |
| Fe | — | 2.5 | Strengthening; kept low for corrosion neutrality |
| Mn | — | 2.0 | Deoxidiser; improves hot workability |
| C | — | 0.30 | Kept low to minimise sensitisation risk |
| Si | — | 0.50 | Minor solid-solution hardener |
| S | — | 0.024 | Hot-shortness control; kept as low as possible |
Source: ASTM B164 / Special Metals Monel® 400 data bulletin. SHUNFU METAL performs OES verification on every heat at incoming inspection, with results reported on the EN 10204 3.1 MTC. Typical Ni content is 65–68%; Cu typically 29–32%.
Mechanical Properties — Monel 400 Bar (ASTM B164)
| Condition | UTS ksi (MPa) | 0.2% YS ksi (MPa) | Elongation % | Hardness |
|---|---|---|---|---|
| Annealed | 75–90 (517–620) | 25–50 (172–345) | 60–35 | 60–80 HRB |
| Hot-Finished | 80–110 (552–758) | 40–100 (276–690) | 60–30 | 75–100 HRB |
| Cold-Drawn & Stress-Relieved | 84–120 (579–827) | 55–100 (379–690) | 40–22 | 85 HRB – 20 HRC |
Annealing is typically performed at 871–982 °C (1,600–1,800 °F) followed by water quench or rapid air cool. Monel 400 is a solid-solution alloy — it cannot be strengthened by precipitation hardening; cold work is the only method to raise yield strength. For sour service per NACE MR-0175, hardness is typically limited to ≤35 HRC (≤331 HBW); the annealed condition comfortably satisfies this limit. SHUNFU METAL performs room-temperature tensile testing and Brinell hardness surveys on each bar batch, with results traceable to the EN 10204 3.1 certificate.