Monel K500 round bar is a precipitation-hardenable nickel-copper alloy (UNS N05500) that combines near-Monel-400 corrosion resistance with significantly higher strength and hardness due to aluminum and titanium additions and age-hardening. For components that must resist seawater, many acids and sour environments while carrying higher static or fatigue loads (shafting, valve trim, fasteners, springs), K500 round bar is among the best practical choices. If you need mill-tested bar, fast factory dispatch from China at competitive factory pricing, MWalloys holds stock and can ship standard diameters and custom lengths with full test documentation.

What is Monel K500 round bar

Monel K500 is a nickel-copper base alloy (roughly 63–66% Ni, ~29–30% Cu) with controlled additions of aluminum (~2.5–2.8%) and titanium (~0.5–0.7%) that enable precipitation (age) hardening to produce a fine dispersion of Ni₃(Al,Ti) precipitates. In the aged condition this alloy attains yield and tensile strengths far higher than Monel 400 while retaining comparable corrosion resistance in many environments. It is non-magnetic at low temperatures and finds frequent use where a combination of corrosion resistance and elevated strength is required.

Chemical composition & standards

Typical composition window (representative — always confirm on MTC/test report):

• Nickel (Ni): ≈ 63.0–66.0 wt%

• Copper (Cu): ≈ 27.0–33.0 wt%

• Aluminum (Al): ≈ 2.5–2.8 wt%

• Titanium (Ti): ≈ 0.5–0.7 wt%

• Iron (Fe), Manganese (Mn), Silicon (Si), Carbon (C) — trace to controlled levels per spec.

Common specifications and designations you may see on drawings and certificates:

• UNS: N05500 (generic K-500 designation)

• Special Metals trade name: Monel® K-500 (Special Metals / INCO origin).

• ASTM / ASME: ASTM B865 / ASME SB-865 (bar/rod forms); other forms per AMS 4676, QQ-N-286, Werkstoff Nr. 2.4375.

Procurement tip: put UNS N05500 and the required spec (e.g., ASTM B865 or AMS 4676) on the PO and request the Mill Test Certificate (MTC) with the lot heat number.

Mechanical properties (representative, aged / hot-worked)

K500’s purpose is higher strength. Typical ranges reported for correctly heat-treated/aged material:

• Tensile strength (ultimate): ≈ 965 MPa (140 ksi) and up — many suppliers list 965–1050 MPa depending on condition.

• Yield strength (0.2% offset): ≈ 690 MPa (100 ksi) minimum in many aged conditions.

• Elongation: generally modest but acceptable (range depends on condition and cross-section).

• Hardness: aged material often ~HRc 27–30 (or HB ~265–300 depending on condition).

Note: mechanical numbers depend strongly on the precise thermal history (solution treat, quench, ageing) and whether the bar was hot-worked or cold-finished before ageing. Ask suppliers for “condition” on the certificate: hot-worked & aged, cold-worked & aged, or solution annealed only.

Corrosion resistance and environment guidance

• In general chloride-bearing seawater, brines, many organic acids and non-oxidizing mineral acids — K500 performs like Monel 400 and is highly resistant.

• Caveat: in the fully aged (high-strength) condition K500 has an increased tendency to stress-corrosion cracking in some concentrated, high-temperature or highly oxidizing environments compared with alloy 400. For critical sour or high-stress applications specify test data and consider the aged vs. solution condition choice.

• For H2S and sour-gas exposure K500 often performs well, but field conditions vary; project-specific corrosion evaluation is recommended (e.g., NACE testing where applicable).

Heat treatment & age hardening (how the strength is produced)

K500 is strengthened by precipitation (age) hardening through a three-step style process used by mills and shops:

1. Solution treatment — heat to a specified high temperature to put solute into solid solution.

2. Quench — fast cool to preserve the supersaturated matrix.

3. Age (precipitation) treatment — hold at an intermediate temperature (e.g., 700–900°F / 370–480°C depending on spec) for a prescribed time to precipitate fine Ni₃(Al,Ti) particles that raise strength and hardness.

Because over-aging or improper quenching can change toughness and SCC susceptibility, specify the required temper (hot-worked and aged / cold-worked and aged) and require MTC details. Special Metals technical bulletin gives recommended thermal cycles and properties for standard conditions.

Forms, stock sizes and weight table

Monel K500 is manufactured and stocked as round bar, hex, flats, plate, wire and forgings. Round bar is the most common stock shape for shafts, fasteners and components.

Below is a practical weight table for commonly stocked Monel K500 round bar diameters. The weights are vendor-reported typical kg/ft and kg/m values (used by many stockists). Use this table for quick estimation; ask your supplier for exact certified weights and dimensional tolerances.

Monel K500 round bar — typical weight chart (selected sizes)
(values taken from industry stock lists and supplier weight charts; confirm with supplier MTC)

Sizing note: ASTM/ASME tolerances apply depending on the ordered standard (ASTM B865 etc.). Typical stock lengths are 1.0–6.0 m or cut to customer length; many suppliers offer custom machining and MTCs.

Machining, welding, forming & finishing

• Machining: K500 machines more difficult than typical stainless steels because of its tendency to work-harden; however carbide tooling, modest cuts and rigid setups produce good results. Use positive rake tooling, low-to-moderate speeds and good coolant.

• Welding: K500 can be welded, but post-weld heat treatment (ageing) may be required to recover strength. Welding filler and procedure must match the metallurgical needs; consult standards and welding suppliers (ERNiCu-7 type filler wire is used in some cases).

• Forming: K500 is workable in the solution-annealed condition; after ageing the ductility falls so forming should be done before final age hardening.

• Surface finish: common finishes for bar are hot-rolled, cold-drawn bright, or turned/ground to size. Specify finish on the PO if surface condition is critical.

Typical industrial uses (where round bar is selected)

• Marine & seawater equipment: propeller shafts, pump shafts, components in seawater service.

• Oil & gas: valve stems, wellhead components, downhole tools and fasteners, particularly where sour gas or H₂S tolerance is needed (project-specific evaluation required).

• Chemical processing: valve components, pump parts exposed to chlorides and organic media.

• Aerospace & instrumentation: specialized fasteners and small parts where corrosion resistance + high strength are required.

Market supply & 2025 pricing snapshot

Market pricing for Monel K500 depends on form (bar, wire, plate), order quantity, surface finish, test certificates, and region. Prices also track base metal costs (nickel + copper) and alloy mill surcharges.

Quick 2025 price snapshot (indicative ranges, mid-2025):

Why prices move: nickel and copper commodity prices set the raw-material floor for Monel alloys. In 2025, LME nickel cash quotes have been in the mid-to-high USD 14,000–15,500/tonne range which materially affects alloy cost. Expect short notice moves if LME swings or tariffs/shipping change.

Procurement tip: for large project buying (several tonnes), ask suppliers for FOB factory quotes from China (100% factory pricing offered by MWalloys where applicable) and compare landed cost including inspection, MTC, shipping and duties. Bulk buys lower unit cost considerably.

Quality, testing & specification checklist

When specifying or buying K500 round bar, insist on:

• UNS N05500 or Monel® K-500 designation and the required specification (e.g., ASTM B865, AMS 4676 or QQ-N-286) on the PO.

• Mill Test Certificate (MTC) with chemical analysis by heat number and mechanical test results (tensile, yield, elongation, hardness).

• Heat treatment condition explicitly stated: hot-worked & aged, cold-worked & aged, or solution annealed.

• Non-destructive testing (NDT) and PMIs if required for critical service.

• Traceability: heat/lot numbers traceable to melting records.

• Inspection: third-party inspection (e.g., SGS, Intertek) if the project demands it.

How To Choosing a supplier

MWalloys sources and holds Monel K500 round bar stock in China and offers:

• 100% factory pricing on standard stock and reasonable lead-times for larger orders (FOB China).

• Fast stock dispatch for common sizes; cut-to-length service and basic machining to print (available on request).

• Full documentation: MTCs, hardness reports, and option for third-party inspection.

• Export compliance & packaging for international shipment, commercial invoices and HS coding assistance.

FAQs

1. Is Monel K500 stronger than Monel 400?
   Yes — K500 attains significantly higher yield and tensile strengths after age hardening due to Ni₃(Al,Ti) precipitates, while keeping Monel-400-like corrosion resistance.

2. Can K500 be used in seawater pump shafts?
   Yes — it is widely used for propeller shafts and pump shafts in seawater, but specify the correct condition and inspection regime for critical shafting.

3. Will K500 rust in saltwater?
   It does not “rust” like carbon steel; nickel-copper alloys resist pitting and uniform corrosion in chloride environments much better than steel. Keep galvanic coupling in mind.

4. What test certificates should I require?
   Mill Test Certificate (MTC) to ASTM/ASME spec, heat number, chemical analysis, mechanical tests (UTS, yield, elongation), hardness, and any NDT you need.

5. Is K500 magnetic?
   K500 is essentially non-magnetic in typical conditions and remains non-magnetic to very low temperatures (special properties noted in manufacturer data).

6. Can I weld K500 and retain strength?
   Welding is possible, but the weld and heat-affected zone often require post-weld heat treatment/ageing to restore properties. Coordinate welding procedure with metallurgist.

7. How does price compare to stainless steels?
   K500 is more expensive than common stainless grades (e.g., 304/316) — it is a specialty nickel alloy and priced accordingly; compare total life-cycle cost for corrosion-critical parts.

8. Do I need to avoid any environments with K500?
   Beware high-temperature oxidizing acids and situations known to promote stress-corrosion cracking for aged K500. For very aggressive conditions consider alternative nickel alloys or consult corrosion experts.

9. What documentation will MWalloys provide?
   Standard MTC to the requested spec, material dimensions, and optional third-party inspection reports on request.

10. Lead time for stocked sizes?
    For common diameters MWalloys can often ship from stock within days; larger, custom or certified lots may take weeks. (Confirm at RFQ.)

Quick procurement checklist

• Spec: UNS N05500 / Monel K500, ASTM B865 or AMS 4676 (pick one).

• Condition: hot-worked & aged / cold-worked & aged / solution annealed.

• Quantity, diameter, length, finish.

• Required MTC fields (chemical, mechanical, heat number).

• Inspection requirement (3rd party? PMI? UT?).

• Delivery terms (FOB/CIF/DDP). For best unit price, consider FOB China factory offers.

Closing recommendations

If your parts require the combined attributes of high corrosion resistance and elevated strength, specify Monel K500 round bar with the exact ASTM/AMS spec and required heat-treatment condition. For volume buys, request a factory FOB quote from an established mill-backed supplier; for small, certified lots, select a trusted distributor and confirm MTCs. MWalloys supports both small and bulk procurement from Chinese factory stock, offering competitive 100% factory pricing and rapid dispatch for common sizes.

Authoritative references

• Monel — Wikipedia overview (history, alloy family, general properties)
• Nickel Institute — Properties of some metals and alloys (Monel K-500 reference table)