Nickel-copper alloy / UNS N05500 / W.Nr. 2.4375
Monel K-500 Forgings: Rolled Rings, Flanges, Shafts & Bars
Open-die forged and age-hardened Monel K-500 to ASTM B865, AMS 4676 or your own specification. Forged in Jiangyin, China, from 5 kg to 8,000 kg per piece, with EN 10204 3.1 or 3.2 certification.
- UNS
- N05500
- Werkstoff
- 2.4375NiCu30Al, BS NA18
- Alloy type
- Ni-CuPrecipitation hardenable
- Nickel
- 63-70 %
- Copper
- 27-33 %
- Density
- 8.44g/cm³ (0.305 lb/in³)
- UTS, aged
- 965 minMPa (140 ksi)
- YS 0.2 %, aged
- 690 minMPa (100 ksi)
- Specifications
- B865AMS 4676, QQ-N-286
- Sour service
- MR0175ISO 15156-3, 35 HRC max
What is Monel K-500? Monel K-500 (UNS N05500, W.Nr. 2.4375, NiCu30Al) is a precipitation-hardenable nickel-copper alloy containing 63 to 70 % nickel and 27 to 33 % copper. Aluminium (2.30 to 3.15 %) and titanium (0.35 to 0.85 %) are added so that Ni3(Al,Ti) gamma-prime particles precipitate during ageing. The alloy holds the seawater and non-oxidising acid resistance of Monel 400 and reaches about three times the yield strength and twice the tensile strength after age hardening.
Where to buy Monel K-500 forgings. Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. It forges Monel K-500 into seamless rolled rings, flanges, shafts, round bars, disks, sleeves, bushings, tube sheets and valve components from 5 kg to 8,000 kg per piece. Drawings are normally quoted within 24 hours. Contact sales@steelforgepieces.com or +86-189-2135-9659.
- Specify it for seawater, brackish water, sour gas (H2S), non-oxidising acids, salts and alkalis, where Monel 400 does not carry enough load.
- Avoid it for continuous service above roughly 480 °C (900 °F), strongly oxidising acids such as nitric acid, and any part that must respond magnetically.
- Nearest alternatives: Monel 400 at lower strength and easier machining, Incoloy 925 and Inconel 718 at higher strength with better chloride SCC resistance.
Page last reviewed 21 August 2026 by the metallurgical department, Jiangyin Jiangnan Metal Co., Ltd.
§1Monel K-500 forged product forms and size range
All items below are open-die forged or ring rolled from Monel K-500 forging stock. They are not cut from plate, so grain flow follows the contour of the part.
| Forged form | Typical size range | Where it is used |
|---|---|---|
| Seamless rolled rings | OD 200-2,500 mm, wall 20-350 mm, height 30-800 mm | Pump casings, valve seat rings, wear rings, retaining rings |
| Forged flanges | OD 50-2,500 mm, 1/2 in to 60 in NPS | WN, SO, blind, orifice and special-drilling flanges for subsea and chemical piping |
| Forged shafts and spindles | dia. 50-500 mm, length up to 6,000 mm | Pump shafts, propeller shafts, eccentric shafts, crankshafts, valve stems |
| Forged round bars | dia. 20-600 mm, length up to 6,000 mm | Machining stock, fasteners, bolting, springs, drill collars |
| Forged disks and discs | dia. 100-1,500 mm, thickness 20-500 mm | Blind covers, valve discs, closure heads, impeller blanks |
| Forged sleeves and bushings | OD 60-1,200 mm, length up to 2,000 mm | Instrumentation sleeves, wear bushings, liners, protective sleeves |
| Forged tube sheets | dia. up to 2,500 mm, thickness up to 400 mm | Shell and tube heat exchangers, feedwater heaters, condensers |
| Forged tubes and hollow pipes | OD 100-1,200 mm, bored to drawing | Pressure vessel nozzles, air receivers, process modules |
| Forged valve components | 5-2,000 kg per piece | Bodies, bonnets, blocks, seat rings and stems for ball, gate, globe, check and plug valves |
| Near-net and contour forgings | 5-8,000 kg per piece | Gears, wheels, manifolds, nozzles, crankshafts, customer drawings |
Sizes above are typical for our open-die presses and ring-rolling mills. Please confirm the envelope for your part on enquiry. Delivery condition can be as-forged, solution annealed, or solution annealed and age hardened. Machining allowance, rough-machined and finish-machined states are quoted on request. Related categories: forged disks, forging gears, forging shafts.
§2Monel K-500 chemical composition (UNS N05500)
Limits below are those of ASTM B865, the governing specification for precipitation-hardening nickel-copper-aluminium bar, rod, wire, forgings and forging stock. Nickel and copper form the corrosion-resistant matrix. Aluminium and titanium are the additions that make the alloy age hardenable.
| Element | Min % | Max % | Function in the alloy |
|---|---|---|---|
| Nickel (Ni + Co) | 63.00 | 70.00 | Matrix former, corrosion resistance in alkalis and reducing acids |
| Copper (Cu) | 27.00 | 33.00 | Seawater and brackish-water resistance, solid-solution strengthening |
| Aluminium (Al) | 2.30 | 3.15 | Forms Ni3(Al,Ti) gamma-prime, the source of age hardening |
| Titanium (Ti) | 0.35 | 0.85 | Co-former of gamma-prime, ties up carbon as TiC |
| Iron (Fe) | - | 2.00 | Residual, controlled to protect corrosion performance |
| Manganese (Mn) | - | 1.50 | Deoxidiser, sulphur control |
| Silicon (Si) | - | 0.50 | Deoxidiser |
| Carbon (C) | - | 0.25 | Restricted to 0.18 max under AMS 4676 |
| Sulphur (S) | - | 0.010 | Kept low to avoid hot shortness during forging |
Note on the balance: nickel plus copper make up the balance of Monel K-500. Iron is a residual limited to 2.00 % maximum and is not the balancing element. Ladle analysis is reported on every certificate. Product analysis is carried out on request within the tolerances of ASTM B880.
§3Monel K-500 mechanical properties
Monel K-500 is supplied either solution annealed, which is the soft condition used for forming and machining, or solution annealed and age hardened, which is the normal delivery condition for shafts, stems, fasteners and pressure-retaining forgings.
| Condition / specification | Tensile strength | Yield strength (0.2 %) | Elongation | Reduction of area | Hardness |
|---|---|---|---|---|---|
| Solution annealed, ASTM B865 | 620 MPa min (90 ksi) | 275 MPa min (40 ksi) | 20 % min | - | 85 HRB max |
| Solution annealed and aged, ASTM B865, section up to 100 mm | 965 MPa min (140 ksi) | 690 MPa min (100 ksi) | 20 % min | - | 27-35 HRC |
| Solution and precipitation heat treated, AMS 4676 | 931 MPa min (135 ksi) | 655 MPa min (95 ksi) | 20 % min | 35 % min | - |
| Sour service, NACE MR0175 / ISO 15156-3 | per order spec | per order spec | - | - | 35 HRC max |
Properties fall as section thickness increases, because the cooling rate through the ageing cycle changes. State the ruling section and the test location (surface, mid-radius or centre) on the enquiry so that the correct acceptance values are quoted. Charpy V-notch impact testing at minus 46 °C or lower is available for offshore and cryogenic orders.
Elevated and low temperature behaviour
Age-hardened Monel K-500 keeps useful strength to about 480 °C (900 °F). Longer exposure above that overages the gamma-prime phase and strength falls off. The ASME Boiler and Pressure Vessel Code accepts Monel K-500 bolting up to 235 °C (455 °F). At the low end there is no ductile-to-brittle transition, and the alloy stays tough down to liquid hydrogen temperature, which is why it appears in cryogenic valve trim and fasteners.
§4Monel K-500 physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.44 g/cm³ | 0.305 lb/in³ |
| Melting range | 1315-1350 °C | 2400-2460 °F |
| Modulus of elasticity, tension | 179 GPa | 26 x 10³ ksi |
| Modulus of rigidity | 65.5 GPa | 9.5 x 10³ ksi |
| Mean coefficient of thermal expansion, 20-100 °C | 13.7 µm/m·K | 7.6 µin/in·°F |
| Thermal conductivity at 20 °C | 17.5 W/m·K | 121 Btu·in/ft²·h·°F |
| Specific heat | 419 J/kg·K | 0.100 Btu/lb·°F |
| Electrical resistivity | 615 nΩ·m | 370 Ω·cmil/ft |
| Curie temperature | approx. -134 °C | approx. -210 °F |
| Magnetic permeability at 20 °C | approx. 1.0005, non-magnetic | - |
Electrical resistivity of Monel K-500 is strongly affected by thermal history because of the age-hardening reaction. The value above is representative of annealed material with light ageing. A magnetic nickel-rich film can develop on the surface during heating and is removed by pickling.
§5Melting route and forging practice
Melting
Monel K-500 forging stock is supplied on an EAF + VOD + ESR route as standard. VIM + VAR or VIM + ESR is used where aerospace or subsea specifications call for lower gas content and tighter inclusion ratings. Every heat is traceable from ingot to finished forging.
Forging temperature
Forging runs between roughly 1150 °C and 900 °C. Enough hot work is put in below 1010 °C to refine grain. Working below 870 °C risks cracking, so the piece goes back to the furnace rather than being pushed cold.
Forging reduction
A minimum forging ratio of 3:1 is applied as standard, and 4:1 or higher on shafts and pressure-retaining parts, so that the as-cast structure is fully broken down and grain flow follows the contour of the finished component.
Forged rather than plate cut
Continuous grain flow around a ring or a shaft shoulder gives higher fatigue strength and better through-thickness ductility than a part machined from rolled plate or bar. This is why offshore and valve specifications call out forgings for pressure-retaining duty.
§6Heat treatment of Monel K-500 forgings
Strength in Monel K-500 comes from precipitation of Ni3(Al,Ti) gamma-prime particles during a controlled ageing cycle, not from quenching. The sequence below follows ASTM B865.
| Step | Temperature | Hold | Cooling |
|---|---|---|---|
| Solution anneal | 980 °C (1800 °F) | per section thickness | Water quench or rapid air cool |
| Age harden, standard cycle | 595 °C (1100 °F) | 8-16 h | Furnace cool at 8-14 °C/h to 480 °C (900 °F), then air cool |
| Age harden, stepped cycle | 595, then 540, then 480 °C | 16 h / 6 h / 8 h | Furnace cool between steps, then air cool |
| Stress relief, annealed material | 540-595 °C | 1-3 h | Air cool |
Heavy forgings are often aged directly from the hot-worked condition rather than re-solution annealed, which gives a better balance of strength and ductility across large sections. Ageing in free air can damage corrosion resistance, so cycles are run in a controlled atmosphere or the surface is pickled afterwards. Furnace charts are issued with EN 10204 3.1 and 3.2 certificates.
§7Machining, welding and fabrication
Machining
Monel K-500 work-hardens rapidly. A tool that dwells or rubs raises the surface hardness at once.
- Rigid setup, minimum overhang, no interrupted feed
- Sharp carbide tooling, positive rake, generous nose radius
- Slow speed with heavy constant feed, cutting under the previous work-hardened layer
- Flood coolant, sulphurised or chlorinated oil for heavy cuts
- Where tolerances allow, rough machine annealed, age harden, then finish machine
Welding
GTAW, GMAW and SMAW are all used, with Monel filler metal 64 (ERNiCu-7) or covered electrode ENiCu-7.
- Clean thoroughly, since sulphur, grease and marking paint cause hot cracking
- Weld in the solution-annealed condition wherever possible
- Post-weld heat treatment is not normally required, but re-age if full strength is needed across the joint
- The heat-affected zone loses age-hardened strength, so keep welds out of highly stressed sections
Forming and threading
Cold form in the annealed condition only. Rolled threads are preferred over cut threads on fasteners and stems. Rolling after ageing puts the surface into compression and lifts fatigue life.
Surface condition
Pickling or bright dipping after heat treatment removes the oxide and any magnetic nickel-rich surface film, restoring both corrosion resistance and non-magnetic behaviour on instrument components.
§8Corrosion resistance of Monel K-500
Monel K-500 carries the corrosion resistance of Monel 400 into a much higher strength level. It covers a wide range, from pure water through non-oxidising mineral acids, salts and alkalis to flowing seawater. It is not a universal alloy, and the aged condition brings one specific limitation.
| Environment | Rating | Comment |
|---|---|---|
| Seawater, brackish water, tidal zones | Excellent | Resists pitting and crevice attack in flowing seawater, with velocity tolerance far above copper alloys |
| Hydrofluoric acid | Excellent | One of the few alloys usable across a wide HF concentration range |
| Sulphuric and phosphoric acid, non-aerated | Good | Rates rise sharply if the acid is aerated or contains oxidising salts |
| Hydrochloric acid, dilute and de-aerated | Fair | Acceptable at low concentration and temperature only |
| Caustic and alkalis | Excellent | Very low corrosion rates, resists caustic stress-corrosion cracking |
| Sour gas, H2S service | Qualified | Acceptable under NACE MR0175 / ISO 15156-3 with hardness 35 HRC max and a controlled ageing practice |
| Nitric acid and strong oxidisers | Poor | Not recommended, use a chromium-bearing alloy such as Inconel 625 |
| Hot aerated chlorides under stress | Caution | Aged K-500 is more prone to stress-corrosion cracking than annealed Monel 400, so control hardness and residual stress |
Ratings are a screening guide. Final material selection must be verified against the actual service fluid, temperature, velocity, aeration and stress state.
§9Applications for Monel K-500 forgings
Monel K-500 is specified where a component has to survive seawater or sour fluids and carry high mechanical load at the same time. That requirement rules out both stainless steel and Monel 400.
Offshore and subsea oil and gas
- Non-magnetic drill collars and instrumentation sleeves
- Wellhead and Christmas tree components
- Subsea and deepwater production system parts
- Safety lifts, valves and springs for oil and gas production
- Forged bushings, sleeves, disks and discs for compressors and generators
Pumps, valves and rotating equipment
- Pump shafts and impellers for chemical and plunger pumps
- Valve stems, seat rings, blocks, bodies and bonnets for ball, gate, globe, check and plug valves
- Seamless rolled rings and wear rings
- Forged spindles, eccentric shafts and crankshafts
Marine and shipbuilding
- Propeller and pump shafts in marine atmospheres and tidal waters
- Fasteners, chains, cables and springs for marine service
- Heavy machinery forged wheels, manifolds and rolls
Chemical and process plant
- Forged flanges, nozzles, tube sheets and shafts for pressure vessels and air receivers
- Shell and tube heat exchangers, preheaters, columns, towers, tanks and silos
- Crystalliser equipment and process modules
- Doctor blades and scrapers for pulp and paper, pharmaceutical and biochemical equipment
§10Monel K-500 compared with Monel 400, Incoloy 925 and Inconel 718
The four grades below cover most enquiries that begin with a need for a corrosion-resistant, high-strength forging.
| Property | Monel K-500 | Monel 400 | Incoloy 925 | Inconel 718 |
|---|---|---|---|---|
| UNS | N05500 | N04400 | N09925 | N07718 |
| Base system | Ni-Cu with Al and Ti | Ni-Cu | Ni-Fe-Cr with Cu | Ni-Cr-Fe with Nb |
| Strengthening | Age hardening, gamma-prime | Cold work only | Age hardening | Age hardening, gamma-double-prime |
| Typical yield, as delivered | 690 MPa min | 170-345 MPa | 690 MPa min | 1035 MPa min |
| Typical tensile, as delivered | 965 MPa min | 480-620 MPa | 965 MPa min | 1275 MPa min |
| Seawater and HF resistance | Excellent | Excellent | Good | Good |
| Oxidising acid resistance | Poor | Poor | Good | Good |
| Max useful temperature | approx. 480 °C | approx. 540 °C | approx. 540 °C | approx. 650 °C |
| Magnetic response | Non-magnetic | Slightly magnetic near ambient | Non-magnetic | Non-magnetic |
| Relative cost | Medium to high | Medium | High | High |
| Choose it when | Seawater or HF service needs real strength | Corrosion matters, load does not | Sour service with chloride SCC risk | Maximum strength at temperature |
Values are indicative for grade screening. Order against the applicable ASTM, AMS or API specification. All four grades are forged in the same works: Monel 400 forgings, Incoloy 925 forgings, Inconel 718 forgings.
§11Testing, NDT and certification
Every Monel K-500 forging leaves Jiangyin Jiangnan Metal Co., Ltd. with a full documentation package. Acceptance levels are agreed with the customer before production starts.
Non-destructive testing
- Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388
- Liquid penetrant inspection to ASTM E165 or EN 571-1
- Dimensional and surface finish inspection to drawing
- Positive material identification by XRF or OES
Mechanical and metallurgical testing
- Tensile testing at room and elevated temperature
- Charpy V-notch impact testing down to minus 196 °C
- Hardness survey, including 35 HRC max verification for NACE MR0175 / ISO 15156-3
- Grain size, microstructure and macro-etch examination
- Intergranular corrosion and slow strain rate testing on request
Certification
EN 10204 3.1 is issued as standard, covering heat number, ladle analysis, mechanical results and heat treatment charts, signed by our own independent inspection department. EN 10204 3.2 is issued when the material is witnessed by a third party such as BV, SGS, TUV, DNV or Lloyd's Register. Country of origin certificates, traceability records and NACE compliance statements are supplied on request.
- ASTM B865, Standard Specification for Precipitation Hardening Nickel-Copper-Aluminum Alloy Bar, Rod, Wire, Forgings and Forging Stock
- AMS 4676, Nickel Alloy Bars, Forgings and Rings, Solution and Precipitation Heat Treated
- NACE MR0175 / ISO 15156-3, Materials for use in H2S-containing environments in oil and gas production
- Special Metals Corporation, MONEL alloy K-500 technical bulletin
Monel K-500 questions we are asked most often
Answers written by our metallurgical department for buyers, design engineers and procurement teams.
What is Monel K-500?
Monel K-500 (UNS N05500, W.Nr. 2.4375, NiCu30Al) is a precipitation-hardenable nickel-copper alloy containing 63 to 70 % nickel and 27 to 33 % copper. Aluminium (2.30 to 3.15 %) and titanium (0.35 to 0.85 %) are added so that Ni3(Al,Ti) gamma-prime particles precipitate during ageing. The alloy holds the seawater and non-oxidising acid resistance of Monel 400 and reaches about three times the yield strength and twice the tensile strength after age hardening.
What is the difference between Monel K-500 and Monel 400?
Monel 400 (UNS N04400) is a solid-solution alloy and can only be hardened by cold work. Monel K-500 (UNS N05500) contains aluminium and titanium and is age hardenable, giving 690 MPa minimum yield and 965 MPa minimum tensile strength in the aged condition against roughly 170 to 345 MPa yield for annealed Monel 400. Corrosion resistance is comparable. Aged K-500 is more sensitive to stress-corrosion cracking in some environments, so hardness is controlled for sour service.
Which standards cover Monel K-500 forgings?
ASTM B865 is the primary specification for bar, rod, forgings and forging stock. Aerospace and high-strength forgings are ordered to AMS 4676, older defence work to QQ-N-286, and UK equivalents are BS 3072, 3073, 3075 and 3076 NA18. Sour-service components follow NACE MR0175 / ISO 15156-3 and API 6ACRA. Jiangyin Jiangnan Metal Co., Ltd. supplies Monel K-500 forgings to ASTM B865, AMS 4676 or customer specification with EN 10204 3.1 or 3.2 certification.
How is Monel K-500 heat treated?
Monel K-500 is solution annealed at about 980 °C (1800 °F) and cooled rapidly, then age hardened at about 595 °C (1100 °F) for 8 to 16 hours, furnace cooled at 8 to 14 °C per hour to 480 °C (900 °F) and air cooled. ASTM B865 also permits a stepped ageing cycle with holds at 540 °C and 480 °C. Heavy forgings are often aged directly from the hot-worked condition.
Is Monel K-500 magnetic?
Monel K-500 is virtually non-magnetic at ambient temperature. Its Curie temperature is about minus 134 °C (minus 210 °F), so it stays non-magnetic well below zero, which is why it is used for non-magnetic drill collars and instrument housings. A thin magnetic nickel-rich film can form on the surface during heating and is removed by pickling or bright dipping.
What is the maximum service temperature of Monel K-500?
Age-hardened Monel K-500 is normally used up to about 480 °C (900 °F). Above that the gamma-prime phase overages and strength falls. The ASME Boiler and Pressure Vessel Code accepts Monel K-500 bolting up to 235 °C (455 °F). At low temperature the alloy shows no ductile-to-brittle transition and stays tough down to cryogenic conditions.
Can you forge Monel K-500 to my drawing?
Yes. Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. It produces Monel K-500 rolled rings, flanges, shafts, bars, disks, sleeves, bushings and tube sheets to drawing or size list, from about 5 kg to 8,000 kg per piece. Send a drawing or dimensions with the specification, delivery condition and test requirements to sales@steelforgepieces.com, or call +86-189-2135-9659, for a quotation.
What NDT and certificates are supplied with Monel K-500 forgings?
Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, together with liquid penetrant inspection, positive material identification, hardness, tensile and Charpy impact testing as required by the order. Certificates are issued to EN 10204 3.1, or EN 10204 3.2 when witnessed by a third party such as BV, SGS, TUV, DNV or Lloyd's Register.
Why is Monel K-500 difficult to machine?
Monel K-500 work-hardens rapidly, so a tool that dwells or rubs raises the surface hardness at once. It needs rigid setups, sharp carbide tooling with positive rake, slow speeds with heavy constant feed and flood coolant. Machining is easier in the solution-annealed condition, so where tolerances allow the part is rough machined before ageing and finish machined after.
Is Monel K-500 suitable for seawater and sour gas service?
Yes. Monel K-500 resists seawater, brackish water, non-oxidising mineral acids, salts and alkalis, and is used for subsea, offshore and sour-gas components such as pump shafts, valve stems, drill collars and fasteners. For H2S service the material must comply with NACE MR0175 / ISO 15156-3, which limits hardness to 35 HRC maximum and restricts the ageing condition.
What is the lead time and minimum order quantity?
Lead time for Monel K-500 open-die forgings is normally 25 to 45 days after drawing approval, depending on piece weight, machining scope and the length of the ageing cycle. There is no fixed minimum order quantity. Single prototype pieces and one-off replacement parts are accepted alongside series orders.
How is the price of a Monel K-500 forging calculated?
Price follows four things: input weight, which is finished weight plus forging and machining allowance, the LME nickel and copper price at the time of purchase, the forging and heat treatment route, and the testing package. Since Monel K-500 is 63 to 70 % nickel, the alloy surcharge dominates, so cutting machining allowance on the drawing usually saves more than negotiating the unit rate. Send a drawing to sales@steelforgepieces.com for a firm quotation.
Related nickel alloy forgings
All grades below are forged, heat treated and tested in the same works.