01 Key data
Alloy K-500 is the age-hardenable member of the nickel-copper family. Aluminium and titanium are added to the Ni-Cu base so that submicroscopic Ni3(Al,Ti) gamma-prime particles precipitate through the matrix during controlled heating. Corrosion behaviour remains close to that of Alloy 400, while tensile strength approximately doubles. The grade is specified for pump shafts, valve stems, drill collars, fasteners and marine propeller shafts, where the strength of Alloy 400 is insufficient.
- UNS designation
- N05500
- Density
- 8.44 g/cm³0.305 lb/in³
- Melting range
- 1315–1350 °C2400–2460 °F
- Tensile, min. aged
- 965 MPa140 ksi (ASTM B865)
- Yield 0.2 %, min.
- 690 MPa100 ksi (ASTM B865)
- Hardness, aged
- 27–38 HRCTypical delivered range
- Magnetic response
- Non-magneticCurie point −134 °C
- Max. hot-work temp.
- 1150 °C2100 °F
Source: ASTM B865 / AMS 4676 limits and published mill data for UNS N05500, compiled and verified for forged product by the metallurgical department of Jiangyin Jiangnan Metal Co., Ltd., August 2026.
Monel® is a registered trademark of the Special Metals Corporation group of companies. Jiangyin Jiangnan Metal Co., Ltd. is not affiliated with Special Metals and supplies this grade under its generic designations: Alloy K-500, Alloy K500 or UNS N05500. Where the trademark appears on this page it is used only to identify the equivalent chemistry.
02 Chemical composition
Composition limits for UNS N05500 per ASTM B865 and AMS 4676, in weight percent. Nickel is determined arithmetically by difference; copper makes up the remainder of the analysis.
| Element | Ni | Cu | Al | Ti | Fe | Mn | Si | C | S |
|---|---|---|---|---|---|---|---|---|---|
| Specified limit | 63.0–70.0 | 27.0–33.0 remainder |
2.30–3.15 | 0.35–0.85 | 2.0 max | 1.5 max | 0.50 max | 0.25 max | 0.010 max |
| Typical heat | 65.5 | 29.5 | 2.75 | 0.60 | 0.9 | 0.8 | 0.15 | 0.13 | <0.005 |
Source: ASTM B865 Table 1 / AMS 4676. Typical-heat column reflects analyses accepted for forging stock by Jiangyin Jiangnan Metal Co., Ltd. Every heat is verified against the specified limits before release to the press.
Aluminium (2.30–3.15 %) and titanium (0.35–0.85 %) are the elements that make Alloy K-500 age-hardenable, and both are held within narrow limits. Insufficient content gives a weak ageing response; excess content reduces hot workability and weldability. When reviewing mill test certificates, check that the aluminium and titanium values fall near the middle of the specified range rather than at either limit.
03 Mechanical properties
ASTM B865 sets acceptance minimums for age-hardened bar, rod and forgings. Typical delivered values sit above those minimums, with heavy sections trending toward the bottom of each band because the cooling rate through the section is slower.
| Form & condition | Tensile | Yield, 0.2 % offset | Elongation | Hardness |
|---|---|---|---|---|
| ASTM B865 minimum hot-worked + age-hardened, all sizes |
965 MPa 140 ksi | 690 MPa 100 ksi |
20 % min | 27 HRC min 265 HB |
| Forgings, typical solution treated + aged |
900–1140 MPa 130–165 ksi | 585–830 MPa 85–120 ksi |
30–20 % | 24–35 HRC |
| Rod & bar, typical hot-finished + aged |
965–1310 MPa 140–190 ksi | 690–1035 MPa 100–150 ksi |
30–20 % | 27–38 HRC |
| Annealed (unaged) reference only |
620–760 MPa 90–110 ksi | 275–450 MPa 40–65 ksi |
45–25 % | 75–90 HRB |
Source: ASTM B865 Table 5 acceptance minimums; typical bands from published nominal mill data for UNS N05500. Compiled by Jiangyin Jiangnan Metal Co., Ltd. Values are indicative. The governing figure is the mill certificate issued against the order.
ASTM B865 applies a size-dependent rule: rounds over 4¼ in. (108 mm) diameter carry a reduced elongation requirement and a maximum hardness of 260 HB. Where a drawing calls for a large-diameter forging together with a high minimum hardness, the conflict should be resolved at the enquiry stage, as it cannot be corrected after ageing.
04 Physical constants
| 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 | 26.0 × 10³ ksi |
| Modulus of rigidity, torsion | 65.5 GPa | 9.5 × 10³ ksi |
| Poisson's ratio | 0.32 | 0.32 |
| Curie temperature | −134 °C | −210 °F |
| Specific heat | 419 J/kg·K | 0.100 Btu/lb·°F |
| Thermal conductivity | 17.5 W/m·K | 121 Btu·in/ft²·h·°F |
| Mean coefficient of thermal expansion | 13.7 µm/m·K | 7.6 µin/in·°F |
| Electrical resistivity | 615 nΩ·m | 370 Ω·cmil/ft |
Source: Published nominal physical constants for UNS N05500 (aged condition), compiled by Jiangyin Jiangnan Metal Co., Ltd. Physical constants are properties of the alloy and do not vary with supplier.
05 Equivalent designations and governing specifications
Alloy K-500 appears under several names on drawings and purchase orders. All of the following describe the same nickel-copper-aluminium chemistry.
| System | Designation | Scope |
|---|---|---|
| UNS (USA) | N05500 | Primary designation used on mill certificates |
| Werkstoff (Germany) | 2.4375 | DIN 17752 / 17754 material number |
| British Standard | NA 18 | BS 3075 (wire) and BS 3076 (bar) |
| Trade name | Monel® K-500 | Special Metals Corporation group trademark |
| ASTM / ASME | B865 / SB-865 | Bar, rod, wire, forgings and forging stock. Most K-500 forgings are ordered to this specification |
| SAE / AMS | AMS 4676 | Bars and forgings, hot-finished, precipitation heat treated |
| US federal | QQ-N-286 | Legacy procurement specification, still cited on defence and oilfield drawings |
| Sour service | ISO 15156-3 NACE MR0175 | Materials for H₂S-containing oil and gas production environments |
| Ultrasonic testing | EN 10228-3 SEP 1921 · ASTM A388 | Volumetric NDT standards applied to K-500 forgings |
| Certification | EN 10204 3.1 / 3.2 | Mill certificate, or third-party witnessed certificate |
Source: Cross-reference maintained by Jiangyin Jiangnan Metal Co., Ltd. Equivalences are close but not always identical. Confirm against the edition of the specification named in the order.
06 Corrosion behaviour
Alloy K-500 retains the corrosion profile of Alloy 400 with little change after precipitation hardening. Performance is strong in flowing seawater, where the copper content resists erosion-corrosion and biofouling, and in reducing acids, where nickel-chromium alloys are less effective.
| Environment | Behaviour | Notes |
|---|---|---|
| Seawater, flowing | Excellent | Resists erosion-corrosion at high velocity; the classic propeller-shaft application |
| Hydrofluoric acid | Excellent | One of the few alloys accepted across a wide HF concentration range |
| Sulphuric acid | Good | Non-aerated and low to moderate concentration |
| Alkalis and caustic soda | Excellent | Resists caustic stress corrosion cracking |
| Neutral salts and brines | Excellent | Very high resistance to chloride stress corrosion cracking |
| Organic acids | Excellent | Doctor blades and scrapers in pulp and chemical processing |
| Nitric and oxidising acids | Poor | Not recommended; select a Ni-Cr-Mo alloy |
| Oxidation, high temperature | Limited | Service is normally limited to about 480 °C (900 °F), above which the ageing response is lost |
Source: Compiled from published corrosion ratings for UNS N05500 by Jiangyin Jiangnan Metal Co., Ltd. Ratings are indicative only. Corrosion performance depends on concentration, temperature, aeration and velocity, and must be validated for your service.
07 Forged product forms and size capability
Jiangyin Jiangnan Metal Co., Ltd. produces Alloy K-500 by open-die forging and radial-axial ring rolling. Open-die forging is used for this grade because it produces directed grain flow, sound centres in heavy sections, and one-off or short-run geometries without die tooling cost.
| Forged form | Size range | Piece weight | Typical use |
|---|---|---|---|
| Seamless rolled rings | OD 300–3000 mm wall 30–400 mm | 30–6000 kg | Pump casings, valve seat rings, flange blanks |
| Forged rings | OD 150–2000 mm | 20–5000 kg | Spacers, retaining rings, adapters |
| Forged discs / disks | Ø 150–2000 mm thk 30–600 mm | 20–8000 kg | Blind flanges, closure heads, blanks |
| Forged shafts & spindles | Ø 60–800 mm L up to 6000 mm | 30–8000 kg | Pump shafts, propeller shafts, eccentric shafts |
| Forged round bars | Ø 40–800 mm | 20–6000 kg | Machining stock, fastener stock, drill collars |
| Forged flanges | OD up to 2500 mm | 20–5000 kg | WN, SO, blind, ring-type joint |
| Sleeves & bushings | OD 100–1500 mm | 20–3000 kg | Wear sleeves, instrumentation sleeves |
| Tube sheets | Ø up to 2500 mm | 100–8000 kg | Shell-and-tube heat exchangers |
| Hollow bars & forged tubes | OD 150–1200 mm | 30–4000 kg | Cylinders, liners, nozzle bodies |
| Blocks & valve bodies | To drawing | 20–8000 kg | Ball, gate, globe, check and plug valves |
Source: Production envelope of Jiangyin Jiangnan Metal Co., Ltd., No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu, China. Sizes outside this table are often possible; send the drawing for confirmation.
Supply conditions available: as-forged, annealed, solution treated, solution treated + aged, rough machined, proof machined, and finish machined to drawing.
08 Production route
Alloy K-500 has a narrow hot-working window, degrades under prolonged soaking at forging temperature, and requires a long controlled ageing cycle. The eight stages below are applied to every Alloy K-500 order.
-
Melt and verify the heat
Forging stock is melted by electric arc furnace, refined by VOD, then ESR remelted for cleanliness and segregation control. The heat analysis is checked against UNS N05500 limits before any material reaches the press.
-
Heat and open-die forge
Ingots are soaked and forged between 880 °C and 1150 °C (1615–2100 °F), with heavy sections finished above roughly 1040 °C. Soaking time is kept short, as prolonged exposure at forging temperature is harmful to this alloy.
-
Ring roll where the geometry calls for it
Ring blanks are upset, punched and rolled on a radial-axial mill to produce seamless rolled rings with continuous circumferential grain flow. Rolled rings therefore give better fatigue performance than rings cut from plate.
-
Solution treat
Forgings are solution annealed to take aluminium and titanium back into solution and reset the grain structure, then cooled rapidly enough to hold that condition before ageing.
-
Age harden
ASTM B865 ageing: hold at an aim of 595 °C (1100 °F) for 8–16 hours, furnace cool to 480 °C (900 °F) at 8–14 °C (15–25 °F) per hour, then air cool. A step-cooled alternative holds at 595 °C, then about 6 h at 540 °C and 8 h at 480 °C. Furnace charts are recorded and issued with the certificate.
-
Rough or proof machine
Machining to the agreed envelope before NDT provides a clean, geometry-controlled surface for ultrasonic examination of heavy sections.
-
Test and inspect
Tensile, yield, elongation and hardness are tested per heat and per heat-treatment batch. Ultrasonic testing follows EN 10228-3, SEP 1921 or ASTM A388 to the class you specify, with PT, MT, impact and grain size added on request.
-
Certify, mark and dispatch
Each lot is hard-stamped with heat number and released with an EN 10204 3.1 mill certificate, or an EN 10204 3.2 certificate witnessed by TÜV, SGS, BV, DNV or Lloyd's Register.
09 Testing, NDT and certification
| Test | Standard | Basis |
|---|---|---|
| Chemical analysis | ASTM B865 / AMS 4676 | Per heat; ladle and product analysis |
| Tensile, yield, elongation | ASTM A370 / EN ISO 6892-1 | Per heat per heat-treatment batch |
| Hardness | EN ISO 6506-1 / ASTM E18 | Per piece or per batch, as specified |
| Ultrasonic testing | EN 10228-3 · SEP 1921 · ASTM A388 | Standard on forgings; class to order |
| Liquid penetrant (PT) | ASTM E165 / EN ISO 3452 | On request |
| Impact testing | ASTM E23 / EN ISO 148-1 | On request, including sub-zero |
| Grain size | ASTM E112 | On request |
| Intergranular corrosion | ASTM G28 (where applicable) | On request |
| Documentation | EN 10204 3.1 / 3.2 | 3.2 witnessed by TÜV, SGS, BV, DNV, LR |
Source: Standard inspection and test plan applied to Alloy K-500 forgings by Jiangyin Jiangnan Metal Co., Ltd. Customer-specific ITPs are accepted and followed as written.
10 Applications
Alloy K-500 combines seawater resistance, high strength and a non-magnetic structure. Few alternative alloys provide all three properties.
-
Oil and gas, downhole
Non-magnetic drill collars, MWD and instrumentation sleeves, valve stems and blocks, wellhead and Christmas tree components, and equipment exposed to chloride and sour-gas media.
-
Subsea and offshore
Forged discs, sleeves and bushings for subsea and deepwater production systems, fasteners, and components in tidal and splash-zone service.
-
Marine and shipbuilding
Propeller and pump shafts, gyroscope parts, springs, fasteners and forged rolls for vessels operating continuously in marine atmospheres.
-
Pumps and rotating equipment
Chemical and plunger pump shafts, eccentric shafts, spindles, wear sleeves, and forged gears where strength and corrosion resistance must coexist.
-
Valves
Forged bodies, stems, seat rings and blocks for ball, gate, globe, check and plug valves, plus strainers in aggressive service.
-
Pressure equipment and heat transfer
Forged tube sheets, flanges, nozzles and shell sections for shell-and-tube heat exchangers, air receivers, columns, towers, silos and preheaters.
-
Chemical processing
Doctor blades and scrapers in organic acids, caustic soda and dry chlorine service; crystalliser components; forged manifolds and process module parts.
-
Pulp, paper and pharmaceutical
Forged rolls and wheels, and process components in biochemistry and pharmaceutical plants where product contamination cannot be tolerated.
11 Design limitations
Three factors account for most reported service problems with age-hardened Alloy K-500.
Age-hardened K-500 is susceptible to hydrogen embrittlement, particularly at the high end of its strength range and under cathodic protection in seawater. Subsea fastener and shaft failures have been attributed to this mechanism. Where cathodic protection is present, specify a strength and hardness ceiling rather than accepting the maximum values available from the ageing cycle.
The aged condition is more SCC-sensitive than solution-annealed Alloy 400 under sustained tensile stress in aggressive media. Mitigation is by reducing sustained stress, avoiding sharp section changes, and selecting a lower-strength temper where the margin is small.
UNS N05500 is listed in ISO 15156-3 (NACE MR0175), but the listing is conditional rather than a blanket approval. Applicability depends on the specific table and edition, the delivered hardness, and the actual H₂S partial pressure, chloride content, pH and temperature. State the sour-service class on the enquiry so the achievable hardness band can be confirmed before the order is accepted.
Weld in the solution-annealed condition using GTAW with ERNiCu-7 (Monel filler metal 60, UNS N04060). Post-weld solution treatment at 850–900 °C with rapid cooling is recommended, after which the component can be aged, although the weld metal will not reach base-metal strength.
12 How to order Alloy K-500 forgings
A complete enquiry allows a firm price and delivery date to be issued on the first reply. Send the following to sales@steelforgepieces.com:
| Item | Example |
|---|---|
| Grade | Alloy K-500 / UNS N05500 |
| Drawing or dimensions | PDF, STEP or DWG, or OD × ID × height for a ring |
| Specification | ASTM B865, AMS 4676, or customer spec |
| Delivery condition | Solution treated + aged, rough machined |
| Quantity | Prototype, or annual call-off |
| NDT requirement | UT to EN 10228-3 quality class 3, plus PT |
| Hardness cap or sour service | ISO 15156-3, hardness ≤ 35 HRC |
| Certificate level | EN 10204 3.1 or 3.2, and the witnessing body |
| Destination | Port and Incoterm; FOB Shanghai, CIF Rotterdam, DDP |
Quotations are normally returned within one working day. Drawings are treated as confidential and NDAs are signed on request.
13 Frequently asked questions
What is Alloy K-500?
Alloy K-500 is a precipitation-hardenable nickel-copper alloy designated UNS N05500 and W.Nr. 2.4375. It contains 63–70 % nickel with copper as the remainder, plus 2.30–3.15 % aluminium and 0.35–0.85 % titanium. Those two additions allow the alloy to be age hardened, so it keeps the seawater and acid corrosion resistance of Alloy 400 while reaching roughly three times its yield strength.
Is Alloy K-500 the same as Monel K-500?
Yes. They are the same material. Monel® is a registered trademark of the Special Metals Corporation group of companies, so mills outside that group describe the grade by its generic name, Alloy K-500, or by its UNS number, N05500. Jiangyin Jiangnan Metal Co., Ltd. supplies the grade as Alloy K-500 to UNS N05500 chemistry.
What is the UNS number for Alloy K-500?
Alloy K-500 is UNS N05500. Its equivalents are W.Nr. 2.4375 in Germany, NA 18 in the British BS 3075 and BS 3076 series, and AWS 041 for the welding-consumable reference.
What standards cover Alloy K-500 forgings?
ASTM B865 and ASME SB-865 are the primary specifications for UNS N05500 bar, rod, wire, forgings and forging stock. AMS 4676 covers bars and forgings in the hot-finished precipitation-hardened condition, QQ-N-286 is the legacy US federal specification, and ISO 15156-3 (NACE MR0175) governs sour service. Jiangyin Jiangnan Metal Co., Ltd. supplies Alloy K-500 forgings to ASTM B865 and AMS 4676.
What is the chemical composition of Alloy K-500?
By weight: nickel 63.0–70.0 %, copper 27.0–33.0 % (remainder), aluminium 2.30–3.15 %, titanium 0.35–0.85 %, iron 2.0 % max, manganese 1.5 % max, silicon 0.50 % max, carbon 0.25 % max and sulphur 0.010 % max, per ASTM B865 and AMS 4676.
How strong is Alloy K-500 after age hardening?
In the hot-worked and age-hardened condition ASTM B865 requires a minimum tensile strength of 140 ksi (965 MPa), a minimum 0.2 % offset yield strength of 100 ksi (690 MPa), and minimum elongation of 20 %. Typical delivered forgings reach 130–165 ksi tensile and 24–35 HRC. Hot-finished bar reaches 140–190 ksi and 27–38 HRC. Heavy sections fall toward the lower end of each range.
Is Alloy K-500 magnetic?
Alloy K-500 is not magnetic at normal service temperatures. Its Curie temperature is about −134 °C (−210 °F) and it remains non-magnetic down to roughly −101 °C (−150 °F). It is therefore specified for non-magnetic drill collars, MWD instrumentation sleeves and gyroscope components.
Can Alloy K-500 be used in sour service with H₂S?
UNS N05500 is listed in ISO 15156-3 (NACE MR0175) for oil and gas production service, but acceptance always depends on the specific table and edition, the delivered hardness condition, and the actual H₂S partial pressure, chloride level, pH and temperature. State the sour-service class on the enquiry and Jiangyin Jiangnan Metal Co., Ltd. will confirm the achievable hardness band before accepting the order.
What is the difference between Alloy 400 and Alloy K-500?
Both are nickel-copper alloys with similar corrosion resistance. Alloy 400 (UNS N04400) is a solid-solution alloy that cannot be age hardened. Alloy K-500 adds aluminium and titanium, which precipitate as Ni₃(Al,Ti) during ageing and give roughly double the tensile strength and triple the yield strength. Age-hardened K-500 is, however, more sensitive to hydrogen embrittlement and stress corrosion cracking.
Who supplies Alloy K-500 open-die forgings in China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, producing Alloy K-500 (UNS N05500) forged rings, seamless rolled rings, discs, shafts, flanges, sleeves, tube sheets and bars for the oil and gas, marine, valve and chemical processing industries. Enquiries: sales@steelforgepieces.com, +86 189 2135 9659.
What sizes of Alloy K-500 forgings can be produced?
Jiangyin Jiangnan Metal Co., Ltd. produces Alloy K-500 forgings from about 20 kg to 8,000 kg per piece. Seamless rolled rings run to approximately 3,000 mm outside diameter, forged discs and tube sheets to approximately 2,000–2,500 mm diameter, and forged bars and shafts to approximately 800 mm diameter and 6,000 mm length. Sizes outside this envelope are often possible; send the drawing for confirmation.
How is Alloy K-500 heat treated?
Alloy K-500 forgings are solution treated and then age hardened. ASTM B865 specifies ageing at an aim temperature of 595 °C (1100 °F) for 8–16 hours, furnace cooling to 480 °C (900 °F) at 8–14 °C (15–25 °F) per hour, then air cooling. An alternative step-cool cycle holds at 595 °C, then about 6 hours at 540 °C and 8 hours at 480 °C before air cooling. Both cycles are run with recorded furnace charts.
What testing and certification is supplied?
Chemical analysis, tensile, yield, elongation and hardness are tested per heat and per heat-treatment batch, with ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388 as specified. Liquid penetrant, magnetic particle, impact and grain size testing are available on request. Documentation is issued as EN 10204 3.1, or EN 10204 3.2 witnessed by TÜV, SGS, BV, DNV or Lloyd's Register.
What information is required to quote?
The drawing or rough dimensions, delivery condition, quantity, the applicable specification such as ASTM B865 or AMS 4676, the NDT class, any sour-service or hardness limit, the certificate level, and the destination port with Incoterm. Quotations are normally returned within one working day.