Constantan alloy wire

Product Introduction
Constantan alloy wire is a precision resistance alloy wire mainly composed of copper and nickel. Its core characteristics include stable resistivity, low resistance temperature coefficient, and minimal resistance fluctuation within a wide temperature range. It also features good oxidation resistance, corrosion resistance, flexibility and weldability, with a maximum operating temperature of up to 500°C.

Applications & Instructions
1. Precision Resistance Components
Used for manufacturing various precision wire-wound resistors, standard resistors, sampling resistors and shunt resistors, widely applied in instruments and electrical measuring equipment.

2. Electronics & Industrial Control
Used for rheostats, potentiometers, strain gauges, heating elements and stable resistance parts in various control circuits.

3. Electrical Equipment
Suitable for electric welding machines, power supplies, frequency converters, instrument cases and other scenarios requiring low temperature coefficient resistance.

4. Scientific Research & Laboratory Equipment
Used in laboratory precision measuring devices, temperature control systems, calibration equipment and other occasions with high requirements for resistance stability.

5. Thermocouple Temperature Measurement
Mainly used as the negative electrode material for Type J, T and E thermocouples, as well as the corresponding thermocouple compensating wire alloy, for industrial temperature detection and signal transmission.

Instructions
It can be connected by resistance welding, argon arc welding, laser welding, silver-based brazing and other methods. Welding joints shall be firm and free from cold soldering to ensure stable conductivity and signal transmission. Insulation treatment shall be carried out according to voltage and environment during use to avoid short circuit caused by direct contact with conductive objects; sleeves or sealing protection shall be added in high temperature or humid environments.

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Core Advantage Specification

Q1: Can constantan wire be used as heating wire?
A1: It can be used as a simple heating element for short-term, low-power applications, but is not suitable for long-term high-temperature heating. The core advantage of constantan is stable resistance rather than high-temperature heating; long-term high temperature will cause oxidation, embrittlement and resistance drift.

Q2: What is the difference between constantan wire and manganin wire?
A2: Both are precision resistance alloys. Manganin has a lower resistance temperature coefficient and higher precision, making it suitable for high-precision standard resistors. Constantan has better oxidation resistance and a higher operating temperature, making it more suitable for thermocouples, compensating wires and general sampling resistors.

Q3: Can constantan wire be used to make thermocouples?
A3: Yes. Constantan paired with iron forms Type J thermocouple, paired with copper forms Type T thermocouple, and paired with nichrome alloy forms Type E thermocouple. It is the key negative electrode material for these three types of thermocouples.

Q4: Can constantan wire still be used if its surface turns black?
A4: Slight oxidation and blackening generally do not affect conductivity and resistance performance. If serious oxidation, peeling, brittle fracture or poor contact occurs, replacement is recommended.

Q5: Can constantan wire be directly soldered with tin?
A5: Yes. Constantan has good weldability and can be firmly connected by conventional tin soldering. The welding temperature should not be too high and the time should not be too long to avoid affecting the internal structure.

Name	Code	Main Composition(%)				Standard
Name	Code	Cu	Mn	Ni	Si	Standard
Constantan	6J40	Bal	1~2	39~41	—	GB/T6145-2010

Name	Code	Resistivity μΩ·m	Temp. Coeffi. Of Resistance (20-1100℃) ×10⁻⁶/℃	Thermal EMF vs. Copper (μV/℃)	Max. working Temp (℃)	Elongation (%)	Tensile Strength (MPa)	Density g/cm³
Constantan	6J40	0.48±0.03	-40~+40	45	≥ 500	≥15	≥390	8.9

Diameter(mm)	0.02-0.028	0.032-0.10	0.112-0.28	0.135-0.50	0.56-1.0	1.06-1.60	1.70-2.12	2.24-3.00	3.15-4.50
Tolerance(mm)	±0.002	±0.003	±0.005	±0.010	±0.015	±0.020	±0.025	±0.030	±0.035