Monel 400 tubing (UNS N04400) delivers an exceptional balance of corrosion resistance, mechanical toughness, and temperature stability that makes it the preferred tubing material for seawater service, chemical processing lines, hydrocarbon applications, and heat-exchanger systems. For buyers seeking reliable supply with factory-direct pricing and fast stock delivery, MWalloys offers Monel 400 tubing from China at competitive, 100% factory ex-works pricing with quick dispatch for stocked sizes.

What is Monel 400 tubing

Monel 400 is a nickel-copper solid-solution alloy traded under UNS N04400. The alloy contains a high nickel fraction plus substantial copper that provides a single-phase structure which cannot be hardened by heat treatment; strengthening occurs through cold work. Common trade and standard references list Monel 400 under many tubing and pipe specifications used worldwide.

Chemical composition and mechanical properties

Chemical composition (typical limits, weight %)

(values compiled from manufacturer technical bulletins and materials databases).

Representative mechanical properties (annealed condition)

(These figures are consistent with published Monel 400 datasheets and materials references; validate required values on mill test certificates for each heat.)

Standards and specifications to request on purchase

When specifying or buying Monel 400 tubing, include the exact standard, heat treatment condition, and testing requirements. Common industry specifications that cover Monel 400 tubing include:

• ASTM B165 / ASME SB165 — Monel 400 seamless and welded tubing/piping.

• ASTM B829, B775, B725, B163 — supplementary tubing specifications referenced in commercial listings.

• UNS N04400 — material designation for certificate traceability.

• NACE MR0175 / ISO 15156 — material suitability guidance for H₂S service in oil and gas; use for sour-service qualification and selection.

Always request mill test reports (MTRs) that quote the UNS number, batch heat number, actual chemical analysis, tensile test results, and the specification standard.

Corrosion resistance and typical environments

Monel 400 exhibits very good resistance to neutral, alkaline, and reducing acidic environments. Standout performance includes:

• Excellent resistance to seawater, brine, and rapidly flowing saline media — a common reason it is used for marine tubing.

• Strong resistance to hydrofluoric acid in many concentrations up to boiling temperature, and good performance with sulfuric acid under reducing conditions.

• Good resistance to chloride-induced stress-corrosion cracking, making it useful where chloride stress cracking is a concern.

Limitations: Monel 400 is not immune to oxidizing acids containing ferric salts or ferric chloride; performance degrades when oxidizing salts are present. Where severe sour (H₂S) conditions apply, verify MR0175/ISO 15156 compliance before selection.

Manufacturing forms and finishes for tubing

Monel 400 tubing is supplied in multiple manufacturing forms depending on application:

• Seamless tubing — drawn or extruded, used for high-integrity, pressure-critical systems.

• Welded tubing — often available for larger diameters where cost or availability dictate.

• Cold-drawn/annealed tubing — improved dimensional tolerances, smoother finishes.

• Coiled tubing — specialized flexible coils for heat exchangers and transfer lines.

Available finishes: pickled, bright-annealed, or polished surfaces. End preparations: plain ends, chamfered, or beveled for welding.

How to select the correct tube grade, size, and furnishing

Selection depends on fluid chemistry, temperature, pressure, and fabrication plans:

• For seawater or brine circuits select Monel 400 with continuity in MTRs showing the UNS N04400 designation. If welding will be performed in the field, request weld procedures and filler metallurgy compatibility.

• For hydrocarbon and sour environments, review NACE/AMPP MR0175 limits and request material qualification if exposure to H₂S exists.

• For heat exchangers, pick cold-drawn, tight-tolerance tubing in specified OD/wall, with surface finish requirements to meet fouling and thermal transfer needs.

When specifying, include these items on the purchase order: UNS number, ASTM/ASME spec, OD × wall or nominal pipe size and schedule, mill finish, required test reports, and packing/marking.

2025 global price comparison (Monel 400 tubing)

Market pricing for Monel 400 fluctuates with nickel and copper commodity prices, fabrication step costs, certification needs, and order quantity. The table below provides indicative ranges for 2025; use these for budgeting only. Request formal quotations for firm pricing.

2025 Monel 400 tubing price — indicative ranges (USD)

Important purchasing note: tubing price per metre depends on OD, wall thickness, and quantity. For small OD thin-wall tubes, price per metre may be higher due to processing costs. For large OD thick-wall tubing, price per kg tends to reduce slightly because of scale. Always request price per unit (USD/m or USD/pc) with full dimensions and MTRs attached.

Quality control, testing, and traceability

Buyers should require the following minimum documentation and testing for critical projects:

• Full Mill Test Report (MTR) with UNS designation, heat number, chemical analysis, mechanical test results, and hardening/cold work state.

• NDT where required: eddy current for tubing, dye penetrant for welds, visual inspection report.

• Certifications: material complies with ASTM B165 (or agreed standard), ISO 9001 factory quality system evidence, and NACE/AMPP qualification when sour service is expected.

• Traceability: heat number marking, stamped packaging, and certificate links to heat number.

When ordering for high-risk service, include a factory witnessed chemical and mechanical test program in your purchase order.

MWalloys product offering and supply advantages

MWalloys supplies Monel 400 tubing from Chinese mills with a focus on industrial buyers requiring:

• Factory-direct pricing — MWalloys lists products at 100% factory ex-works pricing for standard stocked sizes; volume discounts apply.

• Stocked inventory — common OD/wall combinations kept in warehouse for immediate shipment, reducing lead times.

• Quick delivery for stocked items — typical dispatch times for stocked sizes are short; for larger or special sizes MWalloys coordinates mill runs with expedited options.

• Certification and testing — MTRs supplied with each heat, optional third-party inspection on request.

• Customization — cutting to length, end beveling, small batches for prototype work.

Procurement checklist and inspection guidance

When purchasing Monel 400 tubing, include the following items in your checklist:

• Exact part description: Monel 400 / UNS N04400, ASTM/ASME standard, OD × wall (or NPS and schedule).

• Heat treatment state: annealed or cold-worked status if required.

• Required certificates: MTR, heat number, chemical analysis, tensile test.

• NACE/AMPP MR0175 compliance for sour service if applicable.

• Packing and marking instructions for sea freight: heat number, P.O., gross/net weight.

• Inspection plan: visual, dimensional checks, NDT if required.

• Welding compatibility and filler metals if shop welding planned.

On receipt, validate the MTR against the material marking, check dimensions with calibrated tools, and inspect surface finish for corrosion or cold work anomalies.

Fabrication, welding, machining, handling

Practical notes from manufacturing practice:

• Machining: Monel 400 work-hardens quickly. Use slow speeds and generous feed. Use sharp tooling and chip breakers. Lubricants improve tool life.

• Welding: Monel 400 welds well using compatible Ni-Cu filler alloys. Match filler to service conditions. Post-weld heat treatment is generally not used for strengthening because this alloy is solid solution-strengthened.

• Handling: avoid contamination from carbon steel tooling; ensure clean cut surfaces where corrosion resistance matters.

• Bending/forming: cold working will increase strength through strain hardening; anneal when ductility is required.

FAQs

1. Is Monel 400 tubing suitable for seawater heat-exchanger tubing?
   Yes. Monel 400 has proven performance in flowing seawater and brine environments; verify mechanical condition and tube finish for long service.

2. Can Monel 400 be used in H₂S (sour) oilfield service?
   Use caution. Qualification to NACE MR0175/ISO 15156 is necessary for sour environments. Some applications require material qualification or alternative alloys.

3. What standards should I ask for when buying Monel 400 tubing?
   Request UNS N04400 on the MTR and the relevant ASTM/ASME spec (commonly ASTM B165 for tubing/piping).

4. How does Monel 400 compare to 316 stainless steel for chloride service?
   Monel 400 resists chloride stress-corrosion cracking better than many stainless steels under reducing conditions; however, selection depends on temperature, chloride concentration, and oxidizing species.

5. What is the machinability of Monel 400?
   Moderate to poor if using high speeds; the alloy work-hardens. Slow speeds, positive rake tooling, and sharp inserts recommended.

6. Are there magnetic concerns with Monel 400?
   Monel 400 is essentially non-magnetic in the annealed state; cold work can produce minor magnetic response but normally not an issue for most applications.

7. What testing should I demand for safety-critical tubing?
   Full MTRs with actual chemistry and tensile results, dimensional check, eddy-current for tubing wall defects, and third-party inspection where required.

8. How should Monel 400 tubing be stored offshore or on site?
   Protect from prolonged wet storage; use dry, ventilated conditions and keep original packing until installation. For long storage, silica desiccants and sealed packaging reduce surface discoloration.

9. Is Monel 400 weld filler widely available?
   Yes. Ni-Cu based filler alloys compatible with Monel 400 are commonly stocked by industrial suppliers. Verify filler selection by chemistry and application temperature.

10. How to get the best price for Monel 400 tubing?
    Buy factory-direct stocked sizes in large quantities, accept standard mill finishes, and request FOB factory terms. MWalloys provides factory pricing and stocked options that often undercut distributor quotes for common sizes.

Quick purchasing template (copy/paste into RFQ)

Material: Monel 400 tubing, UNS N04400
Standard: ASTM B165 (or buyer-specified)
OD × Wall: _______ mm × _______ mm (or NPS × Schedule)
End finish: plain / chamfered / beveled
Condition: annealed / cold-drawn
Quantity: _______ pieces / _______ kg
Required documents: MTR (3.1 or 3.2), chemical analysis, tensile test, packing list
Inspection: mill inspection OR third-party inspection (specify company)
Delivery term: EXW / FOB / CIF (specify)
Marking: heat number, P.O. number, part no.
Special requirements: NACE MR0175 compliance (if H2S service) / packing for sea freight

Final notes from the technical expert

Monel 400 tubing offers a strong, reliable, and time-proven material choice when chloride resistance, toughness at low temperature, and resistance to certain acids are priorities. Careful attention to standards, MTRs, and service environment selection will maximize service life. MWalloys can supply certified Monel 400 tubing with factory-direct pricing, stocked inventory for rapid shipment, and optional third-party inspection where required. For project quoting, request full MTRs and confirm the standard referenced on the certificate prior to purchase.

Authoritative references

• Special Metals Corporation — MONEL® Alloy 400 Technical Bulletin (PDF)
• Monel — Wikipedia (overview of Monel alloys, properties, uses)