Monel 400 Product Introduction
Product Overview
Monel 400 (UNS N04400) is a classic nickel-copper (Ni-Cu) corrosion-resistant alloy developed by Special Metals Corporation (USA), renowned for its exceptional resistance to marine and aggressive chemical environments. Unlike Incoloy series (Ni-Fe-Cr-based, focusing on high-temp strength or sour service), Monel 400 features a nickel-rich matrix (63-70% Ni) combined with copper (28-34% Cu)—a synergy that delivers unmatched resistance to seawater, brine, and dilute acidic solutions (e.g., sulfuric acid, hydrochloric acid at low concentrations). It maintains good mechanical properties at temperatures up to 427°C, with excellent ductility and weldability, making it a staple material for critical components in marine engineering, chemical processing, and oil & gas offshore applications where "seawater corrosion resistance + structural reliability" are paramount.
International Grade Comparison
Standard System | Grade | Description |
ASTM (USA) | N04400 | UNS Unified Numbering System Grade (exclusive for Monel 400) |
EN (EU) | NiCu30Fe | EN 10088-1 Standard Grade (Ni-Cu corrosion-resistant alloy) |
JIS (Japan) | NW04400 | JIS G4902 Standard Grade (equivalent to Monel 400) |
DIN (Germany) | 2.4360 | DIN 17750 Standard Grade (classic Ni-Cu alloy) |
ISO (International) | NiCu30Fe | ISO 6363 Standard Grade (marine-corrosion-optimized variant) |
Physical Properties (Room Temperature & Key Performance Highlights)
Property Indicator | Typical Value (Room Temp) | Unit | Performance Advantage |
Tensile Strength | ≥485 | MPa | Retains ≥310 MPa tensile strength at 427°C |
Yield Strength (0.2% Offset) | ≥170 | MPa | 427°C yield strength: ≥140 MPa; no significant softening |
Elongation (50mm Gauge Length) | ≥35 | % | High ductility enables cold forming (e.g., bending, drawing) |
Density | 8.89 | g/cm³ | Higher than Incoloy series due to high Cu content |
Melting Point | 1300-1350 | ℃ | Stable liquidus/solidus up to maximum service temp (427°C) |
Magnetic Property | Non-magnetic | — | Suitable for electronic/navigation components |
Chemical Composition (Mass Fraction, Key Elements & Roles)
Chemical Symbol | Composition Range (%) | Role in Performance |
Ni | 63.0-70.0 (Balance) | Stabilizes austenitic matrix; enhances general corrosion resistance |
Cu | 28.0-34.0 | Boosts resistance to seawater, brine, and dilute acids; improves ductility |
Fe | ≤2.5 | Enhances hot workability; reduces hot cracking during forging |
Mn | ≤2.0 | Refines grain size; improves toughness |
C | ≤0.3 | Controlled to minimize carbide precipitation; avoids intergranular corrosion |
Si | ≤0.5 | Improves weldability; reduces welding defects |
S | ≤0.024 | Low content prevents sulfide-induced brittleness |
Product Characteristics
1.Exceptional Marine Corrosion Resistance: Ni-Cu synergy forms a dense protective film, resisting pitting, crevice corrosion, and erosion in seawater, salt spray, and marine sediments—outperforming most stainless steels and Incoloy 825 in long-term marine exposure;
2.Good Acid Resistance: Performs well in dilute sulfuric acid (≤30% concentration, room temp), hydrochloric acid (dilute), and organic acids (e.g., acetic acid), making it suitable for chemical processing of weak acidic media;
3.Superior Formability & Weldability: High elongation (≥35%) enables cold forming (e.g., tube bending, sheet stamping); compatible with arc welding (TIG/MIG) and resistance welding—post-weld corrosion resistance is retained without complex heat treatment;
4.Stable Mechanical Performance: Maintains structural integrity at 427°C; non-magnetic nature makes it ideal for navigation, medical, and electronic components sensitive to magnetic fields;
5.Long Service Life: Resists biofouling in marine environments (e.g., algae, barnacle adhesion) and minimizes maintenance costs for offshore/coastal equipment.
Metallographic Structure
At room temperature, Monel 400 features a single-phase face-centered cubic (FCC) austenitic matrix with no phase transformations during heating/cooling. Trace iron and manganese are dissolved in the Ni-Cu matrix, while low carbon content prevents harmful carbide precipitation at grain boundaries. This simple, stable structure ensures consistent mechanical properties and corrosion resistance across the material—even after long-term exposure to marine or chemical environments.
Product Forms and Executive Standards
Product Form | Main International Executive Standards | Application Reference |
Plates/Sheets | ASTM B127, EN 10088-2 | Marine hull components, chemical tank liners, heat exchanger shells |
Seamless Pipes/Tubes | ASTM B165, EN 10216-5 | Seawater cooling pipes, offshore oil & gas flowlines, acid transport tubes |
Bars/Forgings | ASTM B160, EN 10269 | Marine propeller shafts, valve bodies, pump impellers, fasteners |
Wires/Rods | ASTM B164, EN 10250-3 | Welding filler wires, electrical contacts, precision springs (non-magnetic) |
Tubesheets | ASTM B171, EN 10088-2 | Heat exchanger tubesheets (marine/chemical use) |
