Constantan Foil

Precision Resistance Alloy · 6J40 / 6J44

Rolled copper-nickel precision resistance alloy foil. With high resistivity, a very low temperature coefficient of resistance, a wide operating temperature range and non-magnetic properties, it is a reliable material for precision resistors, strain gauges, thermocouples and compensating wires where resistance to temperature drift and long-term stability matter.

· Product Features

6J40 · CuNi40
6J44 · CuNi44
GB/T 6145-2010
Non-Magnetic
0.01–0.20 mm

Product Story

Its resistance barely changes with temperature

Constantan is a precision resistance alloy based on copper and nickel, offering high resistivity, a low temperature coefficient of resistance, a wide operating temperature range (below 500 ℃), good machinability and brazeability, and non-magnetic properties.

Adding nickel to copper not only changes the material's color but fundamentally reshapes its electrical resistance behavior. Constantan is well suited to AC circuits and widely used in precision resistors, sliding resistors, resistance strain gauges, thermocouples and compensating wires. Its temperature coefficient of resistance can be held within −40 ~ +40 ×10⁻⁶/℃, meaning resistance stays highly stable even when the ambient temperature changes significantly.

6J40 is the general-purpose constantan grade with about 40% nickel (CuNi40); 6J44 contains 43%~46% nickel (CuNi44) and is also a high-nickel copper-nickel constantan grade with resistivity similar to 6J40, used mainly in applications with higher requirements for temperature coefficient of resistance and corrosion resistance. Both are produced to GB/T 6145-2010.

Foil thickness ranges from 5 to 200 μm (0.01–0.20 mm), width from 4.0 to 250 mm, thickness tolerance down to ±1 to ±5 μm, and surface roughness Ra ≤ 0.5 μm. Every micron of precision is a commitment to the long-term stable output of precision components.

Key Properties

0.48±0.03 μΩ·m

Resistivity ρ

−40~+40×10⁻⁶/℃

Temperature coefficient of resistance α

10–200μm

Foil thickness range

4.0–250mm

Foil width range

Why Civen Metal

Why Choose CIVEN Metal?

The core value of constantan foil lies in electrical stability and batch consistency. Through strict melting control and rolling process management, CIVEN ensures that the performance of every roll is well documented.

CIVEN's Quality Commitment in Precision Resistance Alloy Foil

Constantan's performance is highly sensitive to composition. Through composition control and process stabilization, we keep the nickel content and impurity elements of 6J40 / 6J44 within the standard window, so resistivity and temperature coefficient remain stable from batch to batch. For manufacturers of components that operate long-term in precision measurement circuits, this consistency translates directly into lower temperature drift and longer product life.

≥99.5%

Minimum combined mass fraction of Cu + Ni + Mn, with a tightly controlled composition window.

High Resistivity · Low Temperature Coefficient

Resistivity 0.48 ±0.03 μΩ·m, temperature coefficient of resistance held within −40 ~ +40 ×10⁻⁶/℃, suitable for precision resistors and shunts with very high temperature stability requirements.

Wide Operating Temperature Range

Suitable for long-term use below 500 ℃, with a single-phase austenitic solid solution structure and stable performance; for enameled wire, the upper limit is set by the heat resistance of the enamel.

Non-Magnetic

Constantan is non-magnetic and introduces no hysteresis or eddy current interference in AC circuits, making it an ideal material for AC precision resistors and measuring elements.

Workability & Brazeability

Good plasticity for stamping, bending and slitting; good brazeability for producing precision components such as strain gauges and compensating wires.

Stable Electrical Consistency

Chemical composition controlled to GB/T 6145-2010, suitable for applications requiring temperature self-compensation, such as resistance strain gauges.

Full Certification & Delivery

ISO 9001 quality management system, RoHS compliant, with a COA for every shipment; fumigation-free wooden crate packaging available for export.

Applications

Which Precision Components Does It Power?

From precision resistors to temperature measurement, CIVEN constantan foil supports key components in measurement and compensation circuits with stable resistivity and non-magnetic properties.

Precision Resistors · Shunts

Precision resistors and current shunt resistive elements. A low temperature coefficient of resistance ensures long-term accuracy in measurement and metering.

Sliding Resistors · Adjustable Resistors

Sliding resistors, starting and regulating resistor elements. The foil is easy to work, simplifying forming and assembly.

Resistance Strain Gauges

For use from room temperature up to 200 ℃, with temperature self-compensation, suitable for stress measurement and sensor manufacturing.

Thermocouples & Compensating Wires

Used as thermocouple and compensating wire material, with a thermoelectric EMF against copper of about 40–45 μV/℃ (0–100 ℃).

Instrument Resistor Elements

Precision resistor elements in instruments, electronics and industrial equipment, with low long-term drift and good stability.

AC Circuit Measuring Elements

Being non-magnetic, it is well suited to precision resistors and measuring elements in AC circuits, avoiding magnetic interference.

Technical Parameters

Grades, Specifications & Main Properties

Typical reference values (20 ℃) are shown below; actual properties vary with specification, processing condition and heat treatment.

Item	6J40 (CuNi40)	6J44 (CuNi44)
Alloy name	Constantan	Constantan
Standard	GB/T 6145-2010	GB/T 6145-2010
Main composition system	Cu-Ni-Mn (CuNi40)	Cu-Ni-Mn (CuNi44)
Nickel Ni (%)	39.0 ~ 41.0	43.0 ~ 46.0
Manganese Mn (%)	1.0 ~ 2.0	1.0 ~ 2.0
Copper Cu (%)	Balance	Balance
Resistivity ρ (μΩ·m)	0.48 ± 0.03	0.48 ± 0.03
Temperature coefficient of resistance α (×10⁻⁶/℃)	−40 ~ +40	−40 ~ +40
Thermoelectric EMF vs copper (μV/℃)	40 ~ 45	≈ 45
Density (g/cm³)	8.88 ~ 8.90	≈ 8.8
Melting point (℃)	≈ 1270	≈ 1250
Max operating temperature (℃)	≈ 500	≈ 500
Magnetism	Non-Magnetic	Non-Magnetic

Supply Specifications (Foil / Strip)	Range	Notes
Thickness	0.01 ~ 0.20 mm (5 ~ 200 μm)	Customizable in steps
Thickness tolerance	± 1 ~ ± 5 μm	Varies with thickness
Width	4.0 ~ 250 mm	Common 10 ~ 260 mm
Width tolerance	± 0.1 ~ ± 0.5 mm	Varies with width
Surface roughness Ra	≤ 0.5 μm	—
Coil weight	≤ 1000 kg	—
Delivery form	Coils / sheets / slit narrow strip	Inner diameter 50 ~ 150 mm

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