UNS N05500 Weld Neck Flanges — Monel K-500 Age-Hardened (2.4375)
Tesco Steel & Engineering forges UNS N05500 weld neck flanges in Monel K-500 — Werkstoff Nr. 2.4375, the age-hardenable nickel-copper alloy — to ASTM B865, from 1/2″ NB to 56″ NB in ASME B16.5 Class 150–2500 and European PN patterns. Aluminium and titanium additions let K-500 be precipitation-hardened to roughly triple Monel 400's yield strength — ~790 MPa typical — while keeping the family's seawater, hydrofluoric acid and caustic resistance and complete chloride-SCC immunity. The alloy of pump shafts, oil-tool components and naval hardware, NACE MR0175 listed to 35 HRC. Supplied age-hardened with PMI and EN 10204 3.1/3.2 on request. ISO 9001:2015, made in Mumbai, India — exported worldwide.
Monel K-500 · UNS N05500 · 2.4375
Al 2.30–3.15% · Ti 0.35–0.85%
ASTM B865 · QQ-N-286 Heritage
~1100 / 790 MPa Age-Hardened
Seawater · HF · SCC Immune
1/2″ – 56″ NB · Class 150–2500
ISO 9001:2015 · Exported Worldwide
UNS N05500 Weld Neck Flange — Monel K-500 (2.4375), Technical Specifications
What is a UNS N05500 (Monel K-500) Weld Neck Flange?
Monel K-500 (UNS N05500 / 2.4375) is
Monel 400 with muscle:
aluminium and titanium additions let the same two-thirds-nickel, one-third-copper base be
precipitation-hardened to ~1100 MPa tensile / 790 MPa yield — roughly triple the parent alloy — while keeping its
seawater, hydrofluoric acid and caustic resistance and complete
chloride-SCC immunity. A
N05500 weld neck flange pairs that combination with a long
tapered hub butt-welded to the pipe, forged to
ASTM B865.
The strengthening is classic gamma-prime metallurgy: an ageing treatment near 590 °C precipitates fine Ni₃(Al,Ti) particles through the matrix. Decades of QQ-N-286 naval hardware, propeller and pump shafts, oil-tool components and sour-service equipment (NACE MR0175 to 35 HRC) built the alloy's pedigree — flanged joints specify it where mechanical load, not just pressure, governs.
For ordinary Monel piping joints, Alloy 400 remains the economical answer; K-500 is the deliberate step up when the specification names it.
Also searched as: Monel K500 flange, Alloy K-500 flange, N05500 flange, 2.4375 flange, QQ-N-286 flange, age hardened Monel flange, ASTM B865 flange — all refer to the product on this page; see also our
Monel K-500 flanges overview.
Chemical Composition of UNS N05500
| C | Mn | Si | S | Cu | Fe | Ni |
|---|
| 0.25 max | 1.50 max | 0.50 max | 0.010 max | 27.00-33.00 | 0.50-2.00 | 63.00 min |
Values in weight %. N05500 additionally requires the grade's defining age-hardening additions of aluminium 2.30–3.15% and titanium 0.35–0.85% — the elements that form the strengthening Ni₃(Al,Ti) precipitates and separate K-500 from plain Monel 400.
Mechanical Properties of UNS N05500
| Tensile Strength, MPa | Yield Strength, Min, MPa | Elongation % min. |
|---|
| 1100 | 790 | 20 |
Typical age-hardened values per our supply practice; the governing ASTM B865 age-hardened minimums are 965 MPa (140 ksi) tensile and 690 MPa (100 ksi) yield, demonstrated on every certificate — roughly triple Monel 400's strength. For NACE sour service, hardness is verified against the 35 HRC ceiling.
Equivalent Grades of UNS N05500
| Standard | Werkstoff Nr. | UNS |
|---|
| Monel K500 | 2.4375 | N05500 |
Also encountered as Alloy K500 and under the US federal specification QQ-N-286. Forgings supply to ASTM B865. The solid-solution parent is Monel 400 (N04400); the wider family lives on our Monel flanges overview.
UNS N05500 Weld Neck Flange Specifications
| Monel K500 Weld Neck Flanges are available in the following specifications: |
|---|
| Size | 1/2"NB to 56"NB |
| Class | 150#, 300#, 400#, 600#, 900#, 1500#, 2500# |
| Sch (Schedule) | XS, XXS, STD & Schedule 20, 40, 80, 160 |
| Pressure Ratings | PN 2.5 - PN 400 |
| Standards | ASTM B865 / QQ-N-286; ASME B16.5, ASME B16.47, EN 1092-1, DIN 2631–2635, BS 4504 |
| Condition | Solution Annealed & Age-Hardened (precipitation hardened) |
| Other Services | Sand Blasting on Monel K500 Weld Neck Flanges
Shot Peening on Monel K500 Weld Neck Flanges
NACE MR0175 hardness surveys (≤35 HRC)
PMI testing & dye-penetrant examination
Project-specific marking, wrapping & export packing |
Why K-500 When Monel Needs Muscle
Triple the Strength, Same Chemistry
Age hardening lifts yield from ~240 to ~790 MPa while corrosion behaviour stays essentially Monel — seawater, HF and caustic duty intact.
Oil-Tool & Sour-Service Pedigree
NACE MR0175 lists N05500 to 35 HRC — drill collars, wellhead components and subsea hardware have proven it for decades.
Naval Heritage
QQ-N-286 propeller shafts, fasteners and minesweeper hardware — strength plus seawater tolerance plus near-zero magnetism.
Cryogenic Bonus
Strength rises at low temperature with no toughness cliff — the age-hardened structure serves liquefied-gas systems comfortably.
One Family, Both Grades
K-500 flanges forged alongside Monel 400 — matched chemistry through mixed systems, one source for the pair.
Welding K-500 — Plan Around the Ageing
K-500 welds with ERNiCu-7 filler and the usual nickel-alloy cleanliness discipline — but with one planning rule the parent alloy doesn't have: welding locally re-solution-treats the age-hardened structure, softening the heat-affected zone. Practice is to weld in the annealed condition and age the finished assembly, or accept the local soft zone where the design allows — corrosion resistance is unaffected either way. No preheat, no conventional PWHT; sulphur-free cleanliness throughout.
Selection note: for ordinary piping pressure duty,
Monel 400 carries the rating at lower cost — specify K-500 where bolting loads, bending, fatigue or system standardization on K-500 hardware demand the strength.
Where UNS N05500 Weld Neck Flanges Are Used
Oil-tool and subsea equipment lead: wellhead and valve components, drill collars, sour-service hardware to NACE limits. Marine engineering follows — pump and propeller shaft systems, naval fasteners and instrumentation hardware — then chemical plants needing Monel chemistry at mechanical load, and cryogenic systems. Our nickel-alloy production below:
Weld Neck Flanges — Machined & Packed Production
UNS N05500 Weld Neck Flange Dimensions
Monel K-500 weld neck flanges share their dimensions with every other material in the same class — OD, thickness, hub, bore, bolt circle and bolting per the standard tables. Full ASME B16.5 charts:
European PN dimensions are published on the EN 1092-1 Type 11, DIN 2631–2635 and BS 4504 pages.
Price List & How to Order
K-500 pricing tracks nickel closely plus the heat-treatment and testing scope, so we quote live with a stated validity rather than publish a static list. To get a firm quotation, usually within 24 hours:
1
List your requirement — size (NB), class or PN, standard (ASME B16.5 / B16.47 / EN / DIN / BS), grade (Monel K-500 / N05500 / 2.4375), pipe schedule or bore, and quantity.
2
State the condition & testing scope — age-hardened (default) or annealed-for-welding, NACE MR0175 hardness verification, 3.2 witness, PMI, dye-penetrant, or project specifications.
UNS N05500 Weld Neck Flanges — Frequently Asked Questions
What is a UNS N05500 (Monel K-500) weld neck flange?
It is a weld neck flange forged from Monel K-500 — the age-hardenable nickel-copper alloy, UNS N05500 / 2.4375 — to ASTM B865. Aluminium and titanium additions let the alloy be precipitation-hardened to roughly triple Monel 400's yield strength while keeping the same seawater, hydrofluoric acid and caustic resistance. The long tapered hub is butt-welded to the pipe with the bore matched to the pipe schedule — the flange for joints that need Monel chemistry with real muscle.
What is the difference between Monel K-500 and Monel 400?
Chemistry and strength. K-500 adds 2.3-3.15% aluminium and 0.35-0.85% titanium to the same two-thirds-nickel base; an ageing heat treatment then precipitates fine Ni₃(Al,Ti) particles that lift yield strength from Monel 400's ~240 MPa to around 790 MPa — with hardness to serve shafts, fasteners and wear surfaces. Corrosion behaviour stays essentially Monel: seawater, HF and caustic duty with chloride-SCC immunity. Where 400 is the piping workhorse, K-500 is the high-strength specialist.
When does a flange need K-500 instead of Monel 400?
When the joint lives with high mechanical loads beyond gasket seating — subsea and oil-tool connections, high-pressure seawater injection details, pump and agitator mounting flanges that see bending and fatigue, or systems standardized on K-500 hardware. For ordinary piping joints the pressure class governs and Monel 400 is the economical answer; specifications usually name K-500 deliberately, and this page is for when they do.
What does age hardening (precipitation hardening) mean for K-500?
After solution treatment, the alloy is held around 590 °C and slow-cooled, letting sub-microscopic gamma-prime Ni₃(Al,Ti) particles precipitate through the matrix. Those particles obstruct dislocation motion — roughly tripling yield strength without any cold work. The treatment is reversible metallurgy: welding locally re-dissolves it, which is why fabrication planning matters on this alloy.
What are the equivalent designations for Monel K-500?
UNS N05500; Werkstoff Nr. 2.4375; the US federal specification QQ-N-286 familiar from naval hardware; and the trade names Monel K-500 or Alloy K500. Forgings are supplied to ASTM B865. An enquiry in any of these designations is quoted as the same material.
What is the chemical composition of UNS N05500?
Per our supply practice: nickel 63.00% minimum, copper 27.00 to 33.00%, iron 0.50 to 2.00%, manganese 1.50% max, carbon 0.25% max, silicon 0.50% max and sulphur 0.010% max — plus the grade's defining age-hardening additions of aluminium 2.30 to 3.15% and titanium 0.35 to 0.85%, which form the strengthening precipitates.
What are the mechanical properties of N05500 flanges?
Typical age-hardened properties run 1100 MPa tensile, 790 MPa yield and 20% elongation; the governing ASTM B865 age-hardened minimums are 965 MPa (140 ksi) tensile and 690 MPa (100 ksi) yield, demonstrated on every certificate. That is roughly triple Monel 400's strength — nickel-alloy corrosion resistance at alloy-steel muscle.
How does K-500 perform in seawater?
Like Monel 400 with muscle: excellent in flowing seawater against impingement, cavitation and chloride SCC — the pedigree that put K-500 on propeller shafts, pump shafts and naval fasteners. The same honest caveat applies: under stagnant biofouling it can pit, so design keeps systems flowing or drainable. Its combination of strength and seawater tolerance remains unusual among engineering alloys.
Is Monel K-500 suitable for sour service (NACE MR0175)?
Yes, within defined limits — ISO 15156 / NACE MR0175 lists N05500 with a hardness ceiling of 35 HRC for sour-service equipment, and oil-tool components have used it for decades. State the sour-service requirement in the enquiry so heat treatment and hardness verification are aligned to the standard.
Which pipe and fittings do N05500 weld neck flanges mate with?
K-500 piping systems are rare — the alloy usually appears as high-strength components inside Monel 400 systems, so these flanges most often mate B165 Monel 400 pipe with ERNiCu-7 weld metal, keeping one corrosion family through the joint. Where full K-500 runs are specified, B865 bar-machined spools and matching forgings complete the system.
How are Monel K-500 flanges welded to pipe?
With ERNiCu-7 (Monel 400 type) filler and nickel-alloy cleanliness discipline — and one planning rule: welding locally re-solution-treats the age-hardened structure, so the heat-affected zone loses strength unless the assembly is re-aged afterwards. Practice is to weld in the annealed condition and age the finished assembly, or accept the local soft zone where the design allows. The corrosion resistance is unaffected either way.
What temperature range can K-500 flanges be used in?
From cryogenic — strength actually rises at low temperature without a toughness cliff, one reason for its liquefied-gas pedigree — up to about 480 °C, above which the strengthening precipitates begin to over-age. The same sulphur-atmosphere caution as all nickel alloys applies above roughly 315 °C.
Is K-500 magnetic?
Essentially non-magnetic when age-hardened — its Curie point sits well below room temperature, lower than Monel 400's — which is why K-500 served in minesweeper hardware and instrumentation around compasses. Machining can raise faint surface magnetism; normal for the alloy and no cause for PMI alarm.
What testing and certification do you supply with N05500 flanges?
Every lot ships with EN 10204 3.1 mill test certificates covering chemical analysis — demonstrating the aluminium and titanium windows — mechanical properties and the age-hardening record, with 3.2 certification witnessed by Lloyd's, DNV, BV or TÜV on request. We also offer PMI verification, hardness surveys for NACE compliance, hydrostatic testing and dye-penetrant examination, with full heat-number traceability.
Where are UNS N05500 weld neck flanges used?
Oil-tool and subsea equipment — drill collars, valve and wellhead components, sour-service hardware — plus marine engineering where strength meets seawater: pump and propeller shaft systems, naval fasteners, doctor blades and springs. Flanged joints in these systems specify K-500 where mechanical load, not just pressure, governs the design.
What sizes and standards do you manufacture N05500 weld neck flanges in?
From 1/2 inch NB to 56 inch NB: ASME B16.5 Class 150 to 2500 up to 24 inch, ASME B16.47 above, and European PN 2.5 to PN 400 patterns to EN 1092-1, DIN and BS 4504. Raised face is standard, ring joint on request, and every bore is machined to the mating pipe schedule from Sch 10 through XXS.
Do you keep Monel K-500 weld neck flanges in stock? What is the lead time?
K-500 is a to-order alloy in flange form — material moves in project quantities, and the ageing heat treatment adds a production step — so typical lead times run 4 to 6 weeks, with common small sizes occasionally available from bar stock. Prices track nickel closely, so quotations carry a validity period.
Do you export UNS N05500 flanges outside India?
Yes. Tesco Steel & Engineering is an ISO 9001:2015 certified manufacturer based in Mumbai, and Monel K-500 flanges ship to offshore, marine and defence-adjacent projects across the Middle East, Europe, Africa, Southeast Asia and the Americas. Flanges travel face-protected and seaworthy-packed, with full heat-number and test traceability.
