For corrosion-critical projects where seawater, chloride-bearing streams, or certain acids are present, Monel 400 plate (UNS N04400 / W. Nr. 2.4360) is frequently the best long-service, low-maintenance choice. It combines high nickel content with copper to deliver outstanding resistance to flowing seawater, many acids and alkalis, good mechanical strength across a wide temperature range, and straightforward fabrication when proper procedures are used. For buyers seeking factory-direct pricing and fast stock delivery from China, MWAlloys carries ready inventory and provides 100% factory pricing with rapid shipment options for standard plate sizes.

What is Monel 400 plate?

Monel 400 plate is a rolled nickel-copper alloy product (UNS N04400) supplied in sheet and plate forms for structural, marine, chemical and process equipment. It is a single-phase, solid-solution alloy that gains strength primarily by cold working; it cannot be precipitation hardened. Because of its nickel-rich chemistry, the alloy offers excellent resistance to seawater, brackish water, many acids and alkalis, and shows good resistance to stress-corrosion cracking in chloride environments. Common plate applications include heat-exchanger components, seawater pump housings, valve bodies, lining plates, and corrosion-resistant structural parts.

Chemical composition and standards

Typical guaranteed composition (commercial Monel 400 / UNS N04400):

This composition is consistent with mill datasheets and public technical bulletins for Monel® 400. Buyers should always confirm exact certified limits on the Mill Test Certificate for every heat.

Primary product standards to reference when ordering plate:

• ASTM B127 / ASME SB-127 — Specification for Monel 400 plate, sheet and strip.

• ASTM / ASME piping and fabrication standards will apply for components (for example ASME qualifications for pressure parts where relevant).

• International equivalents: EN / DIN designations (W. Nr. 2.4360), UNS N04400, and national mill test formats (EN 10204 3.1 certificates commonly supplied).

When you request quotations, include the ASTM/ASME designation, required thickness range, MTC level (e.g., EN 10204 3.1), and any third-party inspection requirement.

Physical and mechanical properties

Below are representative, commonly used design values — always use the mill certificate and project code for final calculations.

Physical properties

Mechanical properties (typical hot-rolled / annealed condition)

These numbers come from manufacturer data sheets and material handbooks; design engineers should adopt project-specific allowable stresses based on the governing code (e.g., ASME, EN).

Corrosion resistance — where Monel 400 outperforms typical stainless steels

Monel 400 has standout behavior in several corrosive environments:

• Seawater and flowing chloride media: excellent resistance to pitting and crevice corrosion in warm / flowing seawater. That makes it a standard choice for pump shafts, seawater valves and seawater heat-exchanger plates.

• Resistance to many acids: good resistance to hydrochloric (de-aerated), hydrofluoric (low oxidizing conditions), and sulfuric acids in a variety of concentrations and temperatures — but performance depends strongly on oxygenation, temperature, and concentration.

• Stress-corrosion cracking: Monel 400 is far less susceptible to chloride stress-corrosion cracking than many austenitic stainless steels, which is critical for long-service marine components.

Limitations to note

• In oxidizing acids and certain halide-rich oxidizing environments, Monel 400 can still corrode; higher-strength Monel grades or other nickel alloys may be needed.

• Elevated-temperature creep strength is moderate; for high-temperature pressure parts check the applicable code and consider alloys with higher temperature capability.

Fabrication: hot/cold work, welding, and machining

Forming and cold work

• Monel 400 is workable by standard rolling and plate-forming operations. Cold reduction increases strength and hardness; the alloy is typically supplied hot-rolled or annealed and then can be cold-worked for final part strength. Because it hardens only by cold working, heavy cold forming may require intermediate anneals to avoid cracking.

Welding

• Monel 400 welds well by common fusion processes (TIG, MIG, shielded metal arc) using compatible filler metals (ERNiCu-7 / ENiCu-7 family). Preheat is normally not required; post-weld heat treatment is seldom used because the alloy cannot be precipitation-hardened. Use qualified welding procedures that match the plate thickness and joint design.

Machining

• The alloy is tougher on cutting tools than common stainless steels; machinability is rated moderate. Use sharp tooling, reduced cutting speeds relative to mild steel, and high feed with rigid setups. For fine components, consider tool materials and machining strategies recommended by the mill or tooling vendor.

Surface finishing

• Monel 400 may be supplied with mill-rolled finishes (hot-rolled), cold-rolled finishes, or after pickling/passivation per buyer request. For critical sealing surfaces, request flatness tolerances and surface roughness values on the order drawing.

Plate sizes, tolerances and surface conditions

Manufacturers commonly produce Monel 400 plate in these ranges (confirm with the mill):

• Thickness: from thin sheet (~0.5 mm) up to heavy plate (20–100+ mm), with standard stocked thicknesses in the 1.0–25.0 mm range for sheet and plate supply.

• Width: often 650 mm up to 2000 mm (larger widths made to order).

• Length: custom; common cut lengths 1000–6000 mm depending on rolling mill capability.

• Tolerances & MTCs: follow ASTM B127 for plate dimensional tolerances; request EN 10204 3.1 certificates where independent verification is required.

Quality, inspection and certifications to request

When procuring Monel 400 plate, specify the following to avoid ambiguity:

• Material designation: Monel 400 / UNS N04400 / W. Nr. 2.4360.

• Specification reference: ASTM B127 (plate/sheet); if piping components are required, include ASTM B165 for tubing, etc.

• Mill Test Certificate: EN 10204 3.1 (signed by authorized mill representative), showing chemical and mechanical test results traceable to the heat number.

• NACE / MR0175 / API certificates: include if the service is oil & gas sour or if project codes demand them.

• Third-party inspection (TPI): arrange when critical (for example pressure-holding parts, long lead procurements).

• Non-Destructive Testing (NDT): for welded components require RT/UT as required by the construction code. For plate supply, visual, dimensional and chemical verification are commonly performed at mill.

Global price comparison — Monel 400 plate (2025)

Price caveats: Monel pricing depends heavily on nickel and copper metal costs, thickness, mill processing, required certifications, and order quantity. Below are indicative ranges (USD per kilogram) for 2025 gathered from trading platforms, supplier price lists and market posts. Use quotations from mill suppliers for final budgets.

Indicative 2025 price ranges (USD/kg)

Interpretation tips for purchasers

• When bids look much lower than the market range, check the MTC level, whether the price includes cutting and packaging, and shipping terms (EXW vs. FOB vs CIF).

• Large long-term contracts often deliver better unit pricing than small spot buys.

• Stocked plate with standard sizes is cheaper to obtain quickly; custom widths/thicknesses can add lead time and cost.

Where to buy Monel 400 plate

If you require factory-direct supply from China, MWAlloys is positioned to offer the following customer benefits:

• Factory pricing: direct mill and stockist relationships that allow offers at 100% factory price (no middle-man markup) for standard sizes.

• Ready stock: typical inventory for common thicknesses and plate sizes; rapid processing for small to medium orders.

• Documentation: EN 10204 3.1 MTCs and standard ASTM B127 product compliance provided with shipments.

• Value services: cut-to-length, edge-preparation, and optional machining or packing per buyer specification.

• Global shipping options: EXW, FOB Shanghai / Ningbo / Qingdao and CIF to major ports; support for customs paperwork.

How MWAlloys differs from commodity sellers

• Technical metallurgical support and qualification assistance for large projects.

• Transparent QC with lab reports for each heat.

• Competitive lead times for stocked plate and the ability to mobilize mill production for larger or certified runs.

Selection checklist — what buyers should include on RFQ/RFP

Use this checklist to avoid ambiguity:

• Alloy designation (Monel 400 / UNS N04400 / W. Nr. 2.4360).

• Product form (plate / sheet), requested thicknesses and tolerances.

• Surface finish (hot-rolled pickled, cold-rolled, mill finish).

• Quantity and acceptable cut sizes.

• Required standard (ASTM B127 / ASME SB127).

• Certificate level (EN 10204 3.1) and any TPI requirement.

• Packing and marking requests (heat number on each piece).

• Delivery term (EXW / FOB / CIF), port and desired lead time.

• Any special testing (chemical, tensile, PMI) or stamping requirements.

Frequently asked questions

1. Is Monel 400 magnetic?
   Monel 400 is slightly magnetic in the cold-worked condition but considered effectively non-magnetic for many applications. Magnetic response depends on cold work and processing.

2. Can Monel 400 be hardened by heat treatment?
   No — Monel 400 is a solid-solution alloy that is hardened only by cold working; heat treatments do not produce precipitation hardening.

3. How does Monel 400 compare with stainless steel 316?
   Monel 400 typically offers superior resistance to chloride pitting and stress-corrosion cracking compared with 316 in flowing seawater and some acid environments, but 316 is cheaper and has better performance in high-oxygen oxidizing conditions. Cost and the specific service environment dictate selection.

4. Which welding consumable should I use?
   Use Ni-Cu weld filler metals (ERNiCu-7 family or equivalent) and follow qualified procedures. Preheat is usually not required; weld qualification per ASME or EN rules is recommended.

5. What certifications should I insist on?
   For critical projects, insist on ASTM B127 product compliance, EN 10204 3.1 MTC, and any project-specific third-party inspection or NACE/API documentation.

6. Is Monel 400 suitable for sour (H₂S) service?
   Monel 400 has some resistance in certain sour conditions, but sour service must be evaluated case by case; specify NACE MR0175 / ISO 15156 requirements when ordering for oil & gas environments.

7. Typical plate thickness availability?
   Stock commonly covers 0.5 mm up to ~25 mm; thicker plates can be supplied to order by mills. Check with supplier for specific stock/inventory.

8. How should Monel 400 plate be stored?
   Store in dry, covered conditions; avoid contact with dissimilar metals that can cause galvanic corrosion in damp storage.

9. Are there higher-strength Monel variants?
   Yes — Monel K-500 is a precipitation-hardenable variant with higher strength (via Al/Ti additions) but slightly different corrosion behavior; select K-500 only if required for mechanical load needs.

10. How do international prices move?
    Prices track nickel and copper commodity markets, plus mill capacity and certification premiums. Expect regional spreads due to logistics, certification and stock availability; always request firm mill quotations for budget accuracy.

Practical procurement tips and risk points

• Inspect certificates: verify heat traceability on the MTC to prevent grade mixups.

• Ask for element limits: small variations (e.g., higher iron) may change corrosion performance.

• Confirm finish & flatness: for heat-exchanger or gasket surfaces these matter for sealing.

• Shipping & packaging: nickel alloys can be expensive to replace; insist on good blocking and rust-preventive packaging for long ocean voyages.

• Beware lowball quotes: they may reflect non-compliant material, missing certificates, or hidden surcharges.

Closing summary

Monel 400 plate remains a compact, widely proven choice where chloride resistance and seawater performance are mission-critical. The alloy's reliable fabrication behavior and broad mill availability make quick delivery feasible when sourcing from major stockists and Chinese factories. MWAlloys offers factory-direct pricing, immediate stock checking and international shipping options for procurement teams targeting lower landed cost without sacrificing documentation or traceability. For any project, place a request for quotation with explicit specification references (UNS N04400, ASTM B127), required MTC level, and desired logistics terms — I can draft a sample RFQ template tailored to your project dimensions and port if you’d like.

Authoritative references

• MONEL® alloy 400 — Special Metals (technical bulletin, datasheet)
• Monel — Wikipedia (technical and historical overview)