Technical datasheet · Published 14 May 2018 · Last reviewed 20 August 2026 by the metallurgical team at Jiangyin Jiangnan Metal Co., Ltd.
§1 What Monel 400 is
Monel 400 is the most widely used nickel-copper alloy. It is roughly two-thirds nickel and one-third copper, and it is specified for corrosion resistance rather than for strength.
Nickel and copper are mutually soluble across the whole composition range, so alloy 400 forms a single face-centred-cubic solid solution with no second phase. This gives the alloy good ductility, reliable weldability, toughness down to cryogenic temperature and practical immunity to chloride stress corrosion cracking. It also makes the alloy soft. Minimum yield strength in the annealed condition is 170 MPa.
The best-known application is hydrofluoric acid, where alloy 400 remains the standard material of construction for HF alkylation units. It is also used in flowing seawater and brackish water, steam, neutral and alkaline salts, and hot concentrated caustic soda.
Common specification error
Monel 400 cannot be age hardened. There is no second phase to precipitate, so a solution-plus-ageing cycle produces no strength increase. Strength is raised only by cold work. Drawings that call for a heat-treatable nickel-copper alloy require Monel K-500 (UNS N05500), which contains aluminium and titanium and ages at about 595 °C. We query this at enquiry stage whenever an alloy 400 order arrives with an ageing requirement attached.
§2 Specifications and equivalents
ASTM B564, and its ASME boiler code equivalent SB-564, is the controlling specification for Monel 400 forgings. Alloy 400 also has direct national equivalents in the German, British, French, Japanese and Chinese systems.
| System | Designation | Scope |
|---|---|---|
| UNS | N04400 | Unified numbering system |
| Werkstoff / DIN | 2.4360 · 2.4361 | 2.4361 is the higher-purity, lower-carbon variant |
| DIN / EN | NiCu30Fe | DIN 17750 / 17751 / 17752 / 17753 / 17754 |
| British | NA13 | BS 3072 / 3073 / 3074 / 3075 / 3076 |
| French | NU-30 | AFNOR |
| Japanese | NW4400 | JIS H 4551 and related |
| Chinese | NCu30 · NCu30-3-0.5 | GB/T |
| US military | QQ-N-281 | Naval procurement: bar, plate, rod, sheet, strip, wire, forgings |
| Trade names | Monel® 400, Nickelvac® 400, Nicorros® | Proprietary equivalents |
| Product form | ASTM | ASME | Other |
|---|---|---|---|
| Forgings | B564 | SB-564 | QQ-N-281 |
| Rod, bar and wire | B164 | SB-164 | AMS 4674 |
| Plate, sheet and strip | B127 | SB-127 | AMS 4544 |
| Seamless pipe and tube | B165 · B163 | SB-165 · SB-163 | MIL-T-1368 |
| Fittings | B366 | SB-366 | — |
Monel® is a registered trademark of the Special Metals Corporation group of companies. Jiangyin Jiangnan Metal Co., Ltd. is an independent forging manufacturer with no affiliation to Special Metals. The name is used here as the industry-standard designation for UNS N04400.
§3 Chemical composition
Composition limits follow ASTM B564 for UNS N04400. Alloy 400 is melted by electric arc furnace with argon-oxygen or vacuum-oxygen decarburisation, and by electroslag remelting where the customer specification calls for tighter cleanliness. Sulphur is held low because it embrittles nickel alloys at grain boundaries.
| Element | Minimum | Maximum | Role |
|---|---|---|---|
| Nickel + cobalt (Ni+Co) | 63.00 | — | Matrix, carries the corrosion resistance |
| Copper (Cu) | 28.00 | 34.00 | Solid-solution partner, seawater and HF performance |
| Iron (Fe) | — | 2.50 | Residual from melt stock |
| Manganese (Mn) | — | 2.00 | Deoxidiser, sulphur control |
| Carbon (C) | — | 0.30 | Residual |
| Silicon (Si) | — | 0.50 | Deoxidiser |
| Sulphur (S) | — | 0.024 | Impurity, grain-boundary embrittlement |
Nickel is reported inclusive of cobalt, per ASTM convention. Alloy 400 carries no deliberate chromium, molybdenum, aluminium or titanium. A specification asking for Al and Ti is describing Monel K-500, not alloy 400.
§4 Mechanical and physical properties
The tables below give the ASTM B564 minima for annealed forgings, together with typical figures for design guidance.
| Property | Metric | Imperial | Basis |
|---|---|---|---|
| Tensile strength | 480 MPa | 70 ksi | ASTM B564 minimum |
| Yield strength, 0.2% offset | 170 MPa | 25 ksi | ASTM B564 minimum |
| Elongation in 50 mm / 2 in | 35% | ASTM B564 minimum | |
| Reduction of area | 55–70% | Typical | |
| Hardness | 60–80 HRB (≈ 110–150 HB) | Typical, annealed | |
| Modulus of elasticity | 179 GPa | 26 × 106 psi | Typical |
| Impact toughness | Tough to cryogenic temperature, no ductile-brittle transition | Characteristic of FCC alloys | |
| NACE MR0175 / ISO 15156 | Annealed material sits well below the 35 HRC sour-service limit | Hardness survey on request | |
| Property | Value |
|---|---|
| Density | 8.80 g/cm³ · 0.318 lb/in³ |
| Melting range | 1,300–1,350 °C · 2,370–2,460 °F |
| Maximum continuous service in air | ≈ 540 °C · 1,000 °F |
| Curie temperature | ≈ 20–50 °C, varies with heat chemistry |
| Specific heat at 20 °C | 427 J/kg·°C |
| Thermal conductivity at 20 °C | 21.8 W/m·°C |
| Mean thermal expansion, 20–100 °C | 13.9 µm/m·°C |
| Electrical resistivity at 20 °C | 547 nΩ·m · 54.7 µΩ·cm |
| Magnetic response | Weakly ferromagnetic near ambient, paramagnetic above the Curie point |
Magnetic response
The Curie temperature of alloy 400 straddles room temperature, so two heats that both meet ASTM B564 can behave differently on a magnet. Where an application requires non-magnetic material, state the requirement at enquiry stage so it can be written into the order rather than found at inspection.
§5 Forging and heat treatment
Monel 400 forges readily. Two process controls decide the result: finishing temperature and furnace atmosphere.
- Verify billetMTC check · spectrometer re-test
- Heat1,150–1,180 °C · sulphur-free atmosphere
- Open-die forgefinish above 930 °C
- Solution anneal870–980 °C · short soak · rapid cool
- Machinestress relieve 540–565 °C if needed
- Verifytensile, hardness, UT, dimensional
Process notes
- Keep sulphur out of the furnace. Sulphur pickup at forging temperature causes intergranular embrittlement, and it is the most frequent cause of scrapped nickel-copper forgings. Fuel, refractory and residual lubricant all contribute.
- Do not finish cold. Alloy 400 work hardens quickly, and forging below about 930 °C invites cracking. Reheat rather than continue working a cooling billet.
- Full anneal at 870–980 °C with a short soak and rapid cool restores maximum ductility and a recrystallised structure.
- Stress relief at 540–565 °C for 1–2 hours with slow cooling reduces residual stress and machining distortion without recrystallising.
- There is no ageing cycle for this grade. See §1.
- Strength above the annealed minimum comes from cold work, supplied as tempers, or from a change to Monel K-500.
§6 Forged product forms and sizes
Jiangyin Jiangnan Metal Co., Ltd. produces Monel 400 as open-die forgings and seamless rolled rings, worked from certified ASTM B564 billet. Every item is made to drawing. One-off and small-batch work is accepted.
| Form | Typical range | Common uses |
|---|---|---|
| Seamless rolled rings | OD 200–3,000 mm · wall 20–500 mm | Vessel shells, bearing races, flange blanks |
| Forged rings and flanges | DN 15–DN 2000 · Class 150–2500 | Piping, heat exchangers, pressure vessels |
| Discs and blanks | Ø 150–2,500 mm | Tube sheets, closures, blind flanges, pump parts |
| Round bar and shafts | Ø 50–1,000 mm · length up to 6,000 mm | Chemical and plunger pump shafts, valve stems |
| Forged tube sheets | Ø up to 3,000 mm | Shell-and-tube heat exchangers, condensers |
| Hollow bar, sleeves, bushings | OD 100–1,500 mm | Pumps, compressors, subsea housings |
| Valve bodies, seats and stems | to drawing | Ball, gate, globe, check and plug valves |
| Blocks, cubes, stepped shafts | to drawing | Wellhead, Christmas tree, manifolds |
| Single-piece weight | 5–8,000 kg | — |
Delivery condition
- Annealed, black forged with machining allowance. Lowest cost option.
- Annealed, rough machined. Usual choice where the customer does their own finish machining.
- Finish machined to drawing, with dimensional report.
- Cold worked to a specified temper where strength above the annealed minimum is required.
§7 Corrosion performance
Alloy 400 performs well in reducing conditions and poorly in oxidising ones. Most field failures come from crossing that boundary, usually because a service was aerated or contaminated with an oxidising species that was not in the original design case.
| Environment | Performance | Notes |
|---|---|---|
| Hydrofluoric acid | Excellent | Standard material for HF alkylation units |
| Flowing seawater, brackish water | Excellent | Handles high velocity better than copper alloys |
| Caustic soda and alkalis | Excellent | Caustic SCC possible in very hot, concentrated liquor |
| Chloride stress corrosion cracking | Not susceptible | Main reason to select it over 300-series stainless |
| Hydrochloric and sulfuric acid | Good if de-aerated | Moderate concentration and temperature, oxygen degrades it |
| Neutral and alkaline salts, steam | Good | Condensers, feedwater heaters, brine heaters |
| Stagnant seawater | Fair | Crevice and pitting attack possible under deposits |
| Nitric and other oxidising acids | Poor | Not suitable, specify Inconel 625 or a stainless grade |
| Ferric / cupric chloride, wet chlorine | Poor | Oxidising chlorides attack rapidly, use Hastelloy C-276 |
| Moist aerated ammonia, mercury | SCC risk | Stress corrosion cracking hazard |
| Sulfur-bearing gas above ≈ 425 °C | Poor | Sulfidation attack |
Not suitable for
Oxidising media. This covers nitric acid, oxidising salts such as ferric and cupric chloride, aerated acids, and wet chlorine or hypochlorite. Alloy 400 is also at risk of stress corrosion cracking in moist aerated ammonia and in mercury, and it should not run above about 425 °C in sulfur-bearing gas. For oxidising or mixed-acid duty specify Inconel 625 or Hastelloy C-276. For high-temperature oxidising service, Inconel 601.
§8 Where Monel 400 is used
Alloy 400 is specified where a component must survive seawater, hydrofluoric acid or caustic service over a long design life, and where a 170 MPa yield strength is adequate for the load case.
Refining and chemical processing
HF alkylation valve bodies, pump casings and shafts, flanges and tube sheets. Chemical and plunger pump components. Columns, towers, reactors and crystalliser equipment. Heat exchanger tube sheets and channel covers in caustic and salt service.
Marine, offshore and desalination
Seawater pump shafts and impellers, propeller and lineshaft components, valve parts, water-box fittings and brine heater tube sheets. Subsea and deepwater production equipment, wellhead and Christmas tree components, and manifold parts where chloride cracking rules out stainless steel.
Pressure vessels and heat transfer
Forged shells, nozzles, closures, blind flanges, air receivers and shell-and-tube heat exchanger components, built to ASME Section VIII with SB-564 material.
Valves and rotating equipment
Forged bodies, bonnets, seats, seat rings, stems and blocks for ball, gate, globe, check and plug valves. Compressor and turbine parts, gear and coupling blanks, industrial air compressors and nitrogen generators.
Heavy and process industry
Shipbuilding, pulp and paper, pharmaceutical and biochemical plant, cement and sugar mill equipment, forged rolls, wheels and manifolds.
§9 Monel 400 vs K-500, Inconel 625 and 316L
Alloy 400 has the lowest yield strength of the four grades below. That is rarely the deciding factor, because the grade is selected on corrosion behaviour. Where strength does decide the design, the answer is a different alloy rather than a different heat treatment.
Minimum 0.2% offset yield strength. Alloy 400 and 316L annealed, Inconel 625 Grade 1 annealed, K-500 in the aged condition.
| Monel 400 N04400 |
Monel K-500 N05500 |
Inconel 625 N06625 |
316L S31603 |
|
|---|---|---|---|---|
| Base system | Ni-Cu | Ni-Cu-Al-Ti | Ni-Cr-Mo-Nb | Fe-Cr-Ni-Mo |
| Strengthening | Solid solution, cold work | Age hardening | Solid solution | Solid solution |
| Tensile, min | 480 MPa | 690–1,100 MPa | 827 MPa | 485 MPa |
| Yield, min | 170 MPa | 480–790 MPa | 414 MPa | 170 MPa |
| Hydrofluoric acid | Excellent | Very good | Fair | Poor |
| Flowing seawater | Excellent | Very good | Excellent | Poor at velocity |
| Chloride SCC | Not susceptible | Not susceptible | Not susceptible | Susceptible |
| Oxidising acids | Poor | Poor | Excellent | Good |
| Max service temp | ≈ 540 °C | ≈ 480 °C | ≈ 980 °C | ≈ 800 °C |
| Relative cost | Moderate | High | Highest | Lowest |
| Select when | HF acid, seawater or caustic service and strength is not the driver | Same media, but strength, hardness or galling resistance decides | Oxidising or mixed acid, or high temperature | Cost decides and chlorides are absent |
| Page | This page | Monel K-500 | Inconel 625 | Stainless grades |
Within the nickel-copper family
Monel R-405 is alloy 400 with a controlled sulphur addition for free machining, used where high-volume automatic screw machining governs cost. Its corrosion behaviour matches alloy 400, but the sulphur makes it much harder to weld. Monel K-500 is the age-hardening variant. For forgings, alloy 400 and K-500 cover most requirements between them.
§10 Machining, welding and fabrication
Machining
Alloy 400 work hardens rapidly. Use sharp tooling with positive rake, rigid setups, low surface speeds and heavy positive feeds. Do not allow the tool to dwell or rub, because a glazed work-hardened skin will ruin the following pass. Take a consistent depth of cut below any previously hardened layer, and use flood coolant. Machinability is comparable to an austenitic stainless steel, poorer than 304 and considerably poorer than free-machining grades. Where high-volume turning governs cost, Monel R-405 is the alternative.
Welding
Alloy 400 welds well by GTAW, GMAW, SMAW and submerged arc. Use matching Ni-Cu filler: ERNiCu-7 for gas-shielded processes, ENiCu-7 for covered electrodes. No preheat is needed, and no post-weld heat treatment is required for corrosion performance, though stress relief may be specified for dimensional stability. Joint surfaces must be clean, since sulphur, lead, grease and marking paint left on the joint cause hot cracking. Keep interpass temperature low and heat input moderate.
Surface and handling
Forgings ship with rust-preventive oil and VCI film. Alloy 400 needs no protective coating for service in its intended media, though it will tarnish and form a patina in air and seawater. Avoid contact with mercury and with moist aerated ammonia at every stage, including cleaning and testing.
§11 Testing, certification and traceability
Every Monel 400 forging leaving Jiangyin Jiangnan Metal Co., Ltd. is released against a documented test package tied to the heat and lot number.
- Chemistry: melt analysis and product analysis, both reported. PMI on request.
- Mechanical testing: tensile, yield, elongation, reduction of area and hardness survey from test blanks heat treated with the production parts. Charpy V-notch impact on request.
- Ultrasonic examination: EN 10228-3, ASTM A388 or SEP 1921, to the acceptance class stated on the order.
- Surface NDT: dye penetrant to ASTM E165 or E1417. Magnetic particle does not apply to this alloy.
- Grain size and cleanliness: ASTM E112 and ASTM E45 where specified.
- Sour service: hardness survey demonstrating compliance with NACE MR0175 / ISO 15156-3 where required.
- Heat treatment records: furnace charts for the solution anneal and any stress relief.
- Dimensional report for finish-machined parts.
- Certification: EN 10204 3.1 as standard. EN 10204 3.2 witnessed by TUV, SGS, BV or Lloyd's on request.
§12 How to order
Send a drawing or the finished dimensions. Jiangyin Jiangnan Metal Co., Ltd. returns a quotation, forging plan and test scope, normally within 24 hours. To get a firm price first time, include:
- Drawing or dimensions, with machining allowance if the part is to be supplied rough machined.
- Quantity, and whether this is a prototype, a trial order or a series.
- Controlling specification: ASTM B564, ASME SB-564, QQ-N-281 or a customer specification such as NORSOK or Shell DEP.
- Delivery condition: annealed black forged, rough machined or finish machined.
- Whether NACE MR0175 / ISO 15156 compliance and hardness testing are required.
- Test and certification requirements, including UT standard and acceptance class.
- Destination port, Incoterm and required delivery date.
| Item | Detail |
|---|---|
| Minimum order | 1 piece. Trial and prototype orders accepted |
| Lead time | 20–45 days, depending on size, machining and testing |
| Quotation turnaround | Within 24 hours of receiving a drawing |
| Incoterms | EXW, FOB Shanghai / Ningbo, CIF or DDP |
| Payment | T/T or irrevocable L/C at sight |
| Packing | Rust-preventive oil, VCI film, fumigation-free plywood cases |
§13 About the manufacturer
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The works sits in the Yangtze River delta forging cluster, about two hours from the ports of Shanghai and Ningbo.
We produce open-die forgings and seamless rolled rings in carbon steel, alloy steel, tool steel, stainless steel, nickel alloys and maraging steels, covering rings, discs, shafts, bars, flanges, sleeves, bushings, tube sheets and blocks, all made to customer drawing. Monel 400 is supplied alongside Monel K-500 and R-405, the Inconel and Incoloy grades and the Hastelloy family, so a single enquiry can be quoted across several candidate materials where the corrosion case has not yet fixed the alloy.
- Made to drawing. No catalogue-only limitation, and one-off and small-batch work is accepted.
- In-house heat treatment with recorded furnace charts.
- EN 10204 3.1 certification as standard, 3.2 third-party witnessed on request.
- Export experience across Europe, North America, the Middle East and Asia.
Contact the sales engineering team or email sales@steelforgepieces.com with your drawing.
§14 Frequently asked questions
What is Monel 400?
Monel 400 is a nickel-copper alloy containing a minimum of 63% nickel and 28–34% copper, also known as alloy 400, UNS N04400, W.Nr. 2.4360 and NiCu30Fe. It is a single-phase solid-solution alloy that resists seawater, hydrofluoric acid, de-aerated hydrochloric and sulfuric acid and caustic alkalis, and it does not suffer chloride stress corrosion cracking. Jiangyin Jiangnan Metal Co., Ltd. supplies it as open-die forgings to ASTM B564.
Can Monel 400 be age hardened or heat treated to higher strength?
No. Monel 400 is a solid-solution alloy with no second phase to precipitate, so it cannot be strengthened by age hardening or precipitation hardening. Its strength is raised only by cold work. The heat-treatable nickel-copper alloy is Monel K-500 (UNS N05500), which contains about 2.3% aluminium and 0.6% titanium and does respond to ageing at around 595 °C.
What is the difference between Monel 400 and Monel K-500?
Monel 400 is a plain nickel-copper solid-solution alloy with a minimum tensile strength of 480 MPa and a minimum yield strength of 170 MPa. Monel K-500 adds aluminium and titanium so it can be age hardened, reaching roughly 690–1,100 MPa tensile and 480–790 MPa yield. Monel 400 has marginally better seawater corrosion resistance and is easier to weld and machine. Select K-500 where strength, hardness or galling resistance decides the design, such as pump shafts, fasteners and valve stems.
Which standard covers Monel 400 forgings?
ASTM B564, and its ASME equivalent SB-564, is the specification for nickel alloy forgings including UNS N04400. Related product standards are ASTM B164 for rod and bar, ASTM B127 for plate, sheet and strip, ASTM B165 and B163 for seamless pipe and tube, ASTM B366 for fittings, and QQ-N-281 for naval procurement. Jiangyin Jiangnan Metal Co., Ltd. forges to ASTM B564 and issues EN 10204 3.1 or 3.2 certificates.
What is the chemical composition of Monel 400?
Per ASTM B564 for UNS N04400: nickel plus cobalt 63.0% minimum, copper 28.0–34.0%, iron 2.5% maximum, manganese 2.0% maximum, carbon 0.30% maximum, silicon 0.50% maximum and sulphur 0.024% maximum, with iron and residuals making up the balance. Monel 400 contains no deliberate chromium, molybdenum, aluminium or titanium.
What are the mechanical properties of annealed Monel 400 forgings?
ASTM B564 requires a minimum tensile strength of 480 MPa (70 ksi), a minimum 0.2% offset yield strength of 170 MPa (25 ksi) and minimum elongation of 35% in 50 mm for annealed forgings. Typical hardness is 60–80 HRB, well below the 35 HRC limit set by NACE MR0175 and ISO 15156 for sour service. The alloy stays tough to cryogenic temperature with no ductile-to-brittle transition.
Where should Monel 400 not be used?
Avoid Monel 400 in strongly oxidising media: nitric acid, oxidising salts such as ferric and cupric chloride, aerated acids, and wet chlorine or hypochlorite. It is also subject to stress corrosion cracking in moist aerated ammonia and in mercury, and it should not run above about 425 °C in sulfur-bearing gas. For oxidising or mixed-acid duty specify Inconel 625 or Hastelloy C-276 instead.
Is Monel 400 magnetic?
Monel 400 is weakly ferromagnetic at room temperature. Its Curie temperature falls in the region of 20–50 °C and shifts with the exact heat chemistry, so one heat may test slightly magnetic and another effectively non-magnetic near ambient. Above the Curie point the alloy is paramagnetic. Where genuinely non-magnetic material is required, the requirement should be stated at enquiry stage.
Why is Monel 400 used for hydrofluoric acid service?
Monel 400 forms a protective film in hydrofluoric acid that most other engineering alloys cannot, and it holds up across a wide range of HF concentration and temperature. It remains the standard material of construction for HF alkylation units in refineries, covering valve bodies, pump parts, flanges, tube sheets and piping components. The acid must be kept free of dissolved oxygen and oxidising contaminants, which accelerate attack.
What size Monel 400 forgings can Jiangyin Jiangnan Metal produce?
Jiangyin Jiangnan Metal Co., Ltd. produces Monel 400 open-die forgings from about 5 kg to 8,000 kg per piece, with forged and seamless rolled rings to roughly 3,000 mm outside diameter, discs to about 2,500 mm diameter and forged bars and shafts to about 1,000 mm diameter. Send the drawing to sales@steelforgepieces.com to confirm the exact envelope for your part.
How do I order Monel 400 forgings from China?
Send a drawing, or the finished dimensions, quantity, controlling specification and delivery condition, to sales@steelforgepieces.com or call +86-189-2135-9659. Jiangyin Jiangnan Metal Co., Ltd. returns a quotation with a forging plan, test scope and lead time, normally within 24 hours. Typical lead time is 20–45 days depending on size, machining and testing, and trial quantities of a single piece are accepted.
§15 Data sources
Composition, property and heat treatment data on this page are drawn from the published specifications and reference works below, and cross-checked against production test results at Jiangyin Jiangnan Metal Co., Ltd. Where a range is given, the controlling specification and the purchase order take precedence.
- ASTM B564/B564M, Standard Specification for Nickel Alloy Forgings, covering UNS N04400.
- ASTM B164, Nickel-Copper Alloy Rod, Bar and Wire. ASTM B127, Nickel-Copper Alloy Plate, Sheet and Strip.
- ASTM B165 and B163, Nickel-Copper Alloy Seamless Pipe and Tube. ASTM B366, Factory-Made Wrought Nickel Alloy Fittings.
- ASME Boiler and Pressure Vessel Code, Section II Part B: SB-564, SB-164, SB-127, SB-165.
- QQ-N-281, Nickel-Copper Alloy Bar, Plate, Rod, Sheet, Strip, Wire, Forgings and Structural Shapes.
- Special Metals Corporation publication SMC-053, MONEL alloy 400 technical bulletin.
- ASM Handbook, Volume 13B, Corrosion: Materials, nickel and nickel alloys.
- NACE MR0175 / ISO 15156-3, Materials for use in H2S-containing environments in oil and gas production.
- EN 10204, Metallic products, types of inspection documents. EN 10228-3, Non-destructive testing of steel forgings, ultrasonic testing.
This datasheet is provided for guidance. It is not a warranty of properties for a specific application, and it does not replace the controlling specification. Contact our engineering team to confirm suitability for your design.