Monel 401 (UNS N04401) – Low-Resistivity Electrical Alloy Supplier of Round Bars, Wire & Strip | Shanghai Hangbo Alloy Group
Date: 2026年7月22日 Categories: News Views: 257
By Shanghai Hangbo Alloy Group Co., Ltd. | ISO 9001:2015 Certified | Est. 2012 | Shanghai, China
Contact: sales@hangboalloy.com | hangbo@nickel-alloy.com | WhatsApp: +86 13611656360
Quick Answer: What Is Monel 401?
Monel 401 (UNS N04401) is a nickel-copper electrical alloy with approximately 42% nickel and 55% copper that delivers the lowest electrical resistivity of all Monel grades (~0.49 μΩ·m) combined with very low thermoelectric EMF against copper — a combination essential for precision resistor wire, transistor lead frames, waveguide components, and glass-to-metal seals. Unlike Monel 400 (63% Ni) which is optimized for corrosion resistance, Monel 401 is metallurgically tailored for electrical performance while retaining good seawater corrosion resistance and non-magnetic behavior at room temperature. Shanghai Hangbo Alloy Group supplies Monel 401 as round bars, cold-drawn wire, and strip per ASTM B164/B127.
Industry Pain Point: Electronic component engineers selecting contact materials face a classic impedance mismatch: copper has ideal conductivity but negligible corrosion resistance, while standard Monel 400 has excellent corrosion resistance but 25× the resistivity of copper. Monel 401 — with resistivity 3× lower than Monel 400 (~0.49 vs. ~0.54 μΩ·m) and seawater corrosion resistance 100× superior to copper — occupies the narrow performance window where electrical efficiency meets environmental durability.
Key Properties at a Glance
| Property | Value |
|---|---|
| UNS Number | N04401 |
| Alloy Family | Ni-Cu (Monel) — Electrical Grade |
| Density | 8.88 g/cm³ (0.321 lb/in³) |
| Melting Range | 1300–1350°C (2370–2460°F) |
| Curie Temperature | ~25°C (near-room-temp, very weakly magnetic) |
| Electrical Resistivity (20°C) | 0.49 μΩ·m (49 μΩ·cm) |
| Temperature Coefficient of Resistance | ~0.0011 /°C (20–100°C) |
| Thermal EMF vs. Copper | ≤ 5 μV/°C (very low — critical for precision electrical contacts) |
| Tensile Strength (Annealed) | ≥ 380 MPa (55 ksi) |
| Elongation (Annealed) | ≥ 35% |
| Key Standards | ASTM B164, B127, B165 |
Product Overview
Monel 401 is the electrical specialist in the Monel alloy family. While the broader Monel brand is known for seawater corrosion resistance (Monel 400, K-500), Monel 401 was developed for a different set of performance criteria: low and controlled electrical resistivity, minimal thermoelectric voltage when joined to copper conductors, and adequate corrosion resistance for electronic packaging environments.
The alloy's nickel content is deliberately reduced to 40–45% (vs. 63–70% for Monel 400) and copper correspondingly increased to ~55%. This compositional shift has three electrical consequences:
- Resistivity drops from ~0.54 μΩ·m (Monel 400) to ~0.49 μΩ·m — approximately a 10% reduction, which is significant in precision resistor and waveguide applications where every milliohm of series resistance matters.
- Thermoelectric EMF vs. copper is reduced to ≤ 5 μV/°C — an order of magnitude below standard structural alloys. This is critical for low-level DC signal paths: a 10°C temperature gradient across a Monel 400-to-copper junction generates ~40 μV of thermal offset, enough to corrupt a 10 mV full-scale measurement by 0.4%. Monel 401 reduces this error to ≤ 5 μV.
- Temperature coefficient of resistance (~0.0011/°C) is lower and more linear than pure nickel or copper, enabling precision resistor wire that maintains calibration across ambient temperature swings.
The elevated manganese content (up to 2.25%) serves multiple purposes: it provides deoxidation during melting, improves hot workability of the high-copper matrix, and contributes to the controlled resistivity-temperature characteristic. Shanghai Hangbo Alloy Group supplies Monel 401 primarily as cold-drawn wire (for resistor and lead-frame applications), round bar (for machined electrical contacts), and cold-rolled strip (for waveguide and stamped connector applications).
Executive Standards
| Product Form | ASTM | ASME | Typical Dimensions |
|---|---|---|---|
| Round Bar & Rod | ASTM B164 | ASME SB-164 | Ø6–150 mm, hot-rolled or cold-drawn |
| Plate, Sheet & Strip | ASTM B127 | ASME SB-127 | Strip: 0.1–4.0 mm × ≤ 400 mm; Plate: 5–50 mm |
| Seamless Pipe & Tube | ASTM B165 | ASME SB-165 | OD 6–150 mm |
| Cold-Drawn Wire | ASTM B164 | — | Ø0.05–10 mm, bright or coated |
| Forgings | ASTM B564 | ASME SB-564 | Rings, discs, custom shapes |
Chemical Composition (wt.% per ASTM B164/B127 – 100% OES Verified)
| Element | Min | Max | Role in Monel 401 |
|---|---|---|---|
| Nickel (+ Cobalt) | 40.0 | 45.0 | Matrix element; provides corrosion resistance and ductility; lower than Monel 400 to reduce resistivity |
| Copper (Cu) | Balance (~53–58) | — | Primary conductivity element; high Cu content minimizes resistivity and thermoelectric EMF vs. pure copper |
| Manganese (Mn) | — | 2.25 | Deoxidizer; improves hot workability; contributes to controlled temperature coefficient of resistance |
| Iron (Fe) | — | 0.75 | Incidental; kept low to avoid ferromagnetic contamination that would affect low-field magnetic behavior |
| Silicon (Si) | — | 0.25 | Residual deoxidizer; low Si preserves electrical conductivity |
| Carbon (C) | — | 0.10 | Kept moderate — unlike magnetic alloys, Monel 401 does not require ultra-low carbon for electrical performance |
| Sulfur (S) | — | 0.015 | Controlled for hot workability and wire drawability |
Key compositional distinction: The higher copper content (~55% vs. ~32% for Monel 400) and lower nickel (42% vs. 65%) is the root cause of Monel 401's lower resistivity. In Ni-Cu alloys, resistivity follows a roughly parabolic composition dependence with a maximum near 65–70% Ni (the Monel 400 range). Moving the composition toward the 40–45% Ni range shifts the alloy away from the resistivity maximum, reducing ρ by 8–12%.
Physical & Mechanical Properties
Physical Properties
| Property | Value | Unit |
|---|---|---|
| Density (20°C) | 8.88 | g/cm³ |
| Melting Range | 1300–1350 | °C |
| Curie Temperature Tc | ~25 (near room temperature) | °C |
| Electrical Resistivity (20°C) | 0.49 | μΩ·m |
| Temperature Coeff. of Resistance (20–100°C) | ~0.0011 | /°C |
| Thermal EMF vs. Copper (0–100°C) | ≤ 5 | μV/°C |
| Thermal Conductivity (20°C) | ~22 | W/m·K |
| Coefficient of Thermal Expansion (20–100°C) | 14.0 | μm/m·°C |
| Young's Modulus | ~180 | GPa |
| Magnetic Permeability (20°C) | ~1.001 (essentially non-magnetic) | μᵣ |
Mechanical Properties
| Condition | Tensile Strength | Yield Strength 0.2% | Elongation | Hardness |
|---|---|---|---|---|
| Annealed (760–870°C) | 380–480 MPa (55–70 ksi) | 140–240 MPa (20–35 ksi) | 35–45% | 55–75 HRB |
| Cold-Drawn 1/4 Hard | 480–585 MPa (70–85 ksi) | 310–450 MPa (45–65 ksi) | 20–30% | 70–85 HRB |
| Cold-Drawn 1/2 Hard | 585–690 MPa (85–100 ksi) | 450–585 MPa (65–85 ksi) | 10–20% | 80–90 HRB |
| Spring Temper | 690–830 MPa (100–120 ksi) | 585–725 MPa (85–105 ksi) | 5–10% | 88–96 HRB |
Design note: The cold-worked conditions are primarily for wire spring and connector applications where mechanical resilience is the primary requirement and electrical resistivity is tolerant to the ~2–3% increase caused by cold-work-induced dislocations.
Heat Treatment
Solution Annealing (Softening)
| Parameter | Specification |
|---|---|
| Temperature | 760–870°C (1400–1600°F) |
| Soak Time | 15–60 minutes depending on section thickness |
| Cooling Method | Air cool or water quench — either is acceptable |
Stress Relief (After Cold Working)
| Parameter | Specification |
|---|---|
| Temperature | 400–540°C (750–1000°F) |
| Soak Time | 1–2 hours |
| Cooling | Air cool |
Process distinction from Monel 400: Monel 401's annealing temperature range (760–870°C) is approximately 100°C lower than Monel 400 (870–980°C) due to the lower nickel content shifting the recrystallization temperature downward. Processing shops accustomed to Monel 400 must reduce furnace setpoints accordingly — over-annealing Monel 401 at 980°C causes excessive grain growth and a surface "orange peel" texture during subsequent forming.
No precipitation hardening: Monel 401 is a solid-solution alloy. It does not respond to age hardening. Strength increases are achieved through cold working only. Do not apply Monel K-500 aging schedules — the alloy lacks aluminum and titanium and will not age-harden; the 760–870°C range will simply re-anneal any prior cold work.
Production Process
1. Round Bar & Wire
- Melting: Air induction melting or VIM. The high copper content (~55%) gives Monel 401 a lower liquidus than Monel 400, permitting slightly lower pouring temperatures and reducing refractory erosion.
- Hot Working: Billet heated to 900–1100°C. Hot-forged or hot-rolled to bar with minimum 4:1 reduction. Finishing temperature ≥ 850°C. The high manganese content (>1.0%) significantly improves hot workability compared to Monel 400 — the Mn ties up residual sulfur as discrete, spheroidal MnS inclusions rather than grain-boundary Ni₃S₂ films that cause hot shortness.
- Cold Drawing (Wire): Hot-rolled rod annealed at 760–870°C, then cold-drawn through progressive diamond or carbide dies to final diameter. The alloy draws cleanly with standard lubricants; the limiting factor for ultra-fine wire (≤0.05 mm) is the inclusion population from the melting practice — VIM + ESR is recommended for wire below 0.10 mm.
- Surface Finishing: Bright drawn or lightly pickled. For electrical contact applications, surface must be free of drawing lubricant residue and oxide scale — both increase contact resistance at low contact forces.
2. Strip & Sheet
- Hot Rolling: Slab heated to 900–1100°C, hot-rolled to hot-band coil of 2.5–4.0 mm. Finishing temperature ≥ 850°C.
- Cold Rolling: Multi-pass cold rolling with intermediate anneals (760–870°C). Total cold reduction 50–80% depending on final gauge and temper specification.
- Slitting: Precision slitting to customer width. Edge condition controlled — burr-free edge is critical for waveguide applications where burrs create field concentration points and increase RF insertion loss.
- Final Temper: Controlled final cold reduction to achieve ordered temper (1/4 hard, 1/2 hard, spring). Alternatively, final anneal (760–870°C) for soft-temper electrical contact stampings.
Industry Applications
| Industry | Typical Component | Why Monel 401? |
|---|---|---|
| Precision Resistors & Electronics | Precision wire-wound resistor elements, low-TCR resistor wire, potentiometer windings | Low, linear temperature coefficient of resistance (~0.0011/°C); stable resistivity over ambient temperature swings |
| RF & Microwave | Waveguide components, coaxial connector center pins, RF feedthrough conductors | Low resistivity (0.49 μΩ·m) reduces insertion loss; essentially non-magnetic (μᵣ ~1.001) avoids ferromagnetic RF distortion |
| Semiconductor Packaging | Transistor lead frames, hermetic package feedthroughs, glass-to-metal seal pins | Thermal expansion (14.0 μm/m·°C) matches soda-lime and borosilicate glasses; low thermal EMF vs. copper bond pads |
| Marine Electronics | Underwater connector pins, sonar transducer wiring, subsea instrumentation contacts | Good seawater corrosion resistance; low electrical noise from stable oxide film |
| Thermocouple & Instrumentation | Extension lead wire for copper-constantan circuits, thermocouple connectors | Thermal EMF ≤ 5 μV/°C vs. copper — near-zero thermal offset in connector junctions |
| Electrical Contacts & Springs | Relay contact springs, switch blades, brush-holder supports | Good combination of electrical conductivity, spring temper strength (~690–830 MPa), and atmospheric corrosion resistance |
Quality Assurance: 7-Stage Zero-Defect Inspection
- Raw Material Verification: Electrolytic nickel (≥99.95%) and cathode copper (≥99.99%) analyzed by OES before charging. Manganese purity verified — any Mn charge material with >0.02% S is rejected because sulfur from the manganese would negate its hot-workability benefit.
- Melt Chemistry Control: In-process chemistry check. Cu:Ni ratio verified to ensure 40–45% Ni in the final alloy. Manganese verified 1.5–2.0% (internal target — the high end of the 2.25% max provides optimum hot workability). Carbon ≤0.08% internal target (tighter than 0.10% spec max).
- Hot Workability Verification: Hot-torsion or Gleeble test on as-cast sample to confirm zero hot shortness. Any heat showing edge cracking during hot-roll trial is fully re-melted with adjusted manganese and sulfur levels.
- Electrical Resistivity Measurement (Per Heat): Four-point probe resistivity measurement on annealed wire or strip sample per ASTM B193. Resistivity must be 0.47–0.51 μΩ·m to certify the grade. Thermal EMF vs. copper measured on at least one sample per heat — must be ≤ 5 μV/°C over 0–100°C.
- Mechanical Testing: Room-temperature tensile per ASTM E8. For spring-temper wire, additional bend and torsion tests per customer specification.
- Dimensional & Surface Inspection: Wire diameter verified by laser micrometer (±0.005 mm for precision resistor wire). Strip thickness by X-ray gauge (±0.005 mm for ≤ 0.5 mm gauge). Surface roughness Ra verified ≤ 0.4 μm for electronic applications.
- Final Documentation: EN 10204 Type 3.1 certificate with full chemistry, electrical resistivity, thermal EMF, mechanical properties, and dimensional report. For semiconductor and hermetic packaging customers, additional certification of thermal expansion coefficient and glass-seal compatibility available. Third-party inspection by SGS or Bureau Veritas on request.
Frequently Asked Questions
Q1: What is Monel 401 used for?
Monel 401 is used for precision resistor wire, transistor and diode lead frames, glass-to-metal hermetic seal pins, waveguide components, and marine electronic connectors — applications where low and controlled electrical resistivity must coexist with corrosion resistance in chloride-containing environments. It is the electrical-performance Monel, distinct from the corrosion-focused Monel 400.
Q2: What is the density of Monel 401?
8.88 g/cm³ (0.321 lb/in³) at 20°C — very close to Monel 400 (8.83 g/cm³). The slightly higher copper content (55% vs. 32%) has negligible effect on density because copper (8.96 g/cm³) and nickel (8.90 g/cm³) have very similar densities.
Q3: What is the electrical resistivity of Monel 401?
0.49 μΩ·m (49 μΩ·cm) at 20°C — the defining property. This is approximately 10% lower than Monel 400 (~0.54 μΩ·m) and 3× higher than pure copper (~0.017 μΩ·m), but 25× lower than austenitic stainless steels (~1.2 μΩ·m for 316L). For wire gauge conversion: a 1 mm diameter × 1 m length Monel 401 wire has a resistance of approximately 0.62 Ω.
Q4: What is the melting point of Monel 401?
The melting range is 1300–1350°C (2370–2460°F). The solidus temperature (~1300°C) is approximately 50°C lower than Monel 400 (~1350°C) due to the shift toward the Ni-Cu binary composition with a lower solidus at higher copper concentrations.
Q5: What is the tensile strength of Monel 401?
In the annealed condition (760–870°C), tensile strength is 380–480 MPa (55–70 ksi). In spring temper (heavily cold-drawn), tensile strength reaches 690–830 MPa (100–120 ksi). The alloy work-hardens at a rate similar to Monel 400, achieving approximately 2× strength increase from annealed to spring temper.
Q6: What is the yield strength of Monel 401?
Annealed: 140–240 MPa (20–35 ksi). Spring temper: 585–725 MPa (85–105 ksi). Like all Monel alloys, the yield-to-tensile ratio is relatively low (~0.35–0.40) in the annealed condition, increasing to ~0.85 in spring temper as the cold-worked dislocation density saturates.
Q7: What is the elongation of Monel 401?
Minimum 35% in the annealed condition (typically 35–45%). In spring temper, elongation drops to 5–10% — the trade-off for high strength. For glass-to-metal seal applications, the annealed condition with high elongation is preferred to accommodate the thermal-expansion mismatch stress through ductile yielding rather than brittle fracture.
Q8: What are the full mechanical and electrical properties of Monel 401?
Annealed: tensile 380–480 MPa, yield 140–240 MPa, elongation 35–45%, hardness 55–75 HRB. Spring temper: tensile 690–830 MPa, yield 585–725 MPa, elongation 5–10%, hardness 88–96 HRB. Electrical: resistivity 0.49 μΩ·m, TCR 0.0011/°C, thermal EMF vs. Cu ≤5 μV/°C. Physical: density 8.88 g/cm³, thermal expansion 14.0 μm/m·°C, Curie ~25°C (essentially non-magnetic at room temperature).
Q9: What heat treatment does Monel 401 require?
Solution annealing at 760–870°C (1400–1600°F) for softening after cold work. Air cool or water quench acceptable. Stress relief at 400–540°C (750–1000°F) for 1–2 hours after cold forming to reduce residual stress without significant loss of cold-work strength. No precipitation hardening is available — Monel 401 is solid-solution strengthened only. Do NOT apply Monel K-500 aging treatments — the alloy will not harden, only soften.
Q10: What is the annealing temperature for Monel 401?
760–870°C (1400–1600°F) — approximately 100°C lower than Monel 400 (870–980°C). The lower annealing temperature reflects the lower recrystallization temperature of the higher-copper composition. Over-annealing above 900°C produces excessive grain growth and surface "orange peel" texture that is unacceptable for electronic lead-frame stamping.
Q11: How does Monel 401 compare to Monel 400?
| Property | Monel 401 (N04401) | Monel 400 (N04400) | Selection Rule |
|---|---|---|---|
| Nickel Content | 40–45% | 63–70% | — |
| Copper Content | ~55% | ~32% | — |
| Electrical Resistivity | 0.49 μΩ·m | 0.54 μΩ·m | 401 — 10% lower |
| Thermal EMF vs. Cu | ≤ 5 μV/°C | ~40 μV/°C | 401 — 8× lower, critical for precision DC |
| Tensile Strength (Annealed) | 380–480 MPa | 480–550 MPa | 400 — 15–25% stronger |
| Seawater Corrosion | Good | Excellent (reference grade) | 400 — better for corrosion-limited applications |
| Cost (Relative) | ~0.85–0.95× Monel 400 | Baseline | 401 — slightly lower (less Ni) |
Decision rule: If the primary design constraint is electrical (resistivity, TCR, thermal EMF), select Monel 401. If the primary constraint is corrosion resistance (seawater, HF acid, caustic), select Monel 400. For combined electrical + corrosion requirements (subsea connectors, marine instrumentation), Monel 401 is the optimum choice where the electrical performance margin justifies the slightly lower corrosion resistance.
Q12: What is the price of Monel 401 per kg?
Indicative EXW pricing for Monel 401 round bars is \$22–38/kg, with cold-drawn wire 10–20% higher depending on diameter and temper, and strip 5–15% lower. The lower nickel content (~42% vs. ~65% for Monel 400) typically gives Monel 401 a slight cost advantage — approximately 5–15% less than Monel 400 at equal product form and quantity. Shanghai Hangbo Alloy Group provides firm quotations within 2 business hours — email sales@hangboalloy.com with your specification and annual volume estimate.
Q13: Is Monel 401 weldable?
Yes, using GTAW (TIG) and GMAW (MIG) with ERNiCu-7 (Monel 60) filler metal. Key parameters: preheat not required for sections ≤ 25 mm; interpass temperature ≤ 150°C; heat input 1.0–2.0 kJ/mm. The weld metal chemistry is closer to Monel 400 (65% Ni) nominally, so the welded joint will have marginally higher resistivity than the Monel 401 base metal. For electrical applications where this matters (precision resistors, waveguide), design welded joints to be outside the active current path or use brazing (BAg-series silver brazing alloys) as an alternative joining method with lower joint resistance.
Q14: What product forms does Shanghai Hangbo supply for Monel 401?
We supply Monel 401 in cold-drawn wire (Ø0.05–10 mm, bright finish, in coils or spools — the dominant product form for resistor and lead-frame wire), round bars (Ø6–150 mm, hot-rolled or cold-drawn), cold-rolled strip (0.1–4.0 mm thickness, widths up to 400 mm), plates (5–50 mm), and seamless tubes (OD 6–150 mm). Wire is available in annealed, 1/4 hard, 1/2 hard, and spring tempers. Electrical resistivity and thermal EMF certification provided with each lot.
Q15: Does Shanghai Hangbo ship Monel 401 internationally?
Yes. We export Monel 401 to over 40 countries with terms FOB Shanghai, CIF, CFR, and DAP. Standard destinations include USA, Germany, UK, Japan, South Korea, Singapore, and India. Cold-drawn wire and precision strip are the most common export products — spooled and desiccant-packaged for moisture protection. Stock items ship within 2–4 weeks; mill-order production is 8–12 weeks. All export documentation: commercial invoice, packing list, certificate of origin, EN 10204 3.1 MTC with electrical resistivity and thermal EMF certification.
Q16: Why is thermal EMF vs. copper important for Monel 401?
Thermoelectric EMF (Seebeck effect) generates a voltage at every junction between dissimilar metals in a circuit. In precision DC measurement systems — strain-gauge bridges, thermocouple data loggers, nanovoltmeter input connectors — a Monel 401-to-copper junction generates only ≤ 5 μV per °C of temperature difference, vs. ~40 μV/°C for Monel 400-to-copper. In a 24-bit ADC system with a 10 mV full-scale range, a 40 μV thermal offset from a single connector junction represents a 0.4% systematic error — enough to push a 0.1%-class instrument out of specification before it leaves the calibration lab. By reducing thermal EMF to ≤ 5 μV/°C, Monel 401 eliminates this error source at its root — the connector metal itself — rather than compensating for it in calibration software.
Contact Shanghai Hangbo Alloy Group
| Channel | Details |
|---|---|
| Company | Shanghai Hangbo Alloy Group Co., Ltd. (宝昭实业（上海）有限公司) |
| Website | www.nickel-alloy.com |
| Email (Sales) | sales@hangboalloy.com |
| Email (Technical) | hangbo@nickel-alloy.com |
| +86 13611656360 | |
| Skype | live:specialalloy001 |
| Address | Room 1508, No. 288 Shiyi Road, Baoshan District, Shanghai 200940, China |
| ISO Certification | ISO 9001:2015 — View certificate on request |
| Response Time | ≤ 10 minutes during business hours (Mon–Fri, 08:00–18:00 GMT+8) |
Your Next Step
Email sales@hangboalloy.com with your Monel 401 specification:
- Product form: Wire / Bar / Strip / Tube
- Dimensions: Diameter (wire/bar) or thickness × width (strip), in mm or AWG
- Temper: Annealed / 1/4 Hard / 1/2 Hard / Spring
- Electrical certification: Resistivity, TCR, and thermal EMF vs. copper required? (Yes — standard with all Monel 401 shipments)
- Delivery destination: Full address + preferred incoterm (FOB / CIF / DAP)
For precision resistor wire applications, we can provide sample spools (100 m) for your TCR and noise-floor qualification testing before committing to production quantities.
