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Cupronickel

What Is Cupronickel (Copper-Nickel)

Cupronickel (also as copper-nickel) is the name given to any alloy that belongs to an important group of alloys containing copper (for a major part) and nickel (in a lesser amount) that is widely known for its excellent resistance to corrosion, pitting and erosion, strength, workability and weldability. It is manufactured in the form of wires, tubes, pipes, rods, sheets, etc. according to its applications. It comes in different grades [1, 5, 7].

Cupronickel

Composition [1]

The most common copper-nickel alloys being 90/10 cupronickel and 70/30 cupronickel, the chemical composition of both are given below.

90/10 Cupronickel

Copper 86 – 89.7%
Nickel 9.0 – 11.0%
Iron 1.0 – 2.0%
Manganese 0.3 – 1.0%

70/30 Cupronickel

Copper 70.1 – 65.5%
Nickel 29.0 – 32.0%
Iron 0.5 – 1.5%
Manganese 0.4 – 1.0%

Cupronickel Sheet

Properties and Characteristics of Cupronickel

Physical Properties

Color/appearance Silvery [9]
Luster Metallic [9]
Melting point 1170 – 1240°C, 2140 – 2260°F [1]
Density 8.5 – 8.95 mg m3 [5]
State of matter at room temperature (normal phase) Solid [1]
Thermal Conductivity 19 – 66 W/(m K) [5]
Electrical Conductivity 5% IACS [7]
Resistivity 50X10-8 ohm-m [3]
Ductility Yes [5]
Malleability Yes [9]
Tensile strength 267 – 624 MPa [5]
Young’s modulus 120 – 156 GPa [5]

Magnetic Properties

Magnetic ordering  Paramagnetic and ferromagnetic depending on the nickel content [6]

Cupronickel Wire

Uses

  1. In brazing, making standard resistors. However, their high thermoelectric e.m.f against copper is a disadvantage towards their application in dc resistors. In ac resistors, though, there is not much of a problem [8].
  2. For manufacturing welding electrodes, boat hulls, marine condenser tubes, heat exchangers, brake lines, pipe fittings, valves and fasteners [1].
  3. Its high success as a coinage material is mainly due to its durability and no-tarnish property [9].

Copper-nickel

Is It Dangerous

It may cause allergic skin reactions. If skin irritation or rash occurs, prompt medical supervision is required. Note that copper-nickel coins are not allergic due to low nickel content. Inhalation of fumes or dust should be avoided as it is suspected to cause cancer. Do not handle the alloy without wearing protective gloves and covering your face and eyes [2].

Copper Nickel Coin

Cupronickel Image

Interesting Facts

  • The alloy is 100% recyclable [9].
  • The nickel coins that we use are actually made of cupronickel and not nickel [1].

References:

  1. What is Cupronickel? – Thebalance.com
  2. Copper Nickel Safety Data Sheet – Husseycopper.com
  3. Resistance Alloys and Wire Resistances – Kayelaby.npl.co.uk
  4. Magnetic Properties of Copper Nickel Alloys – Journals.aps.org
  5. Copper Alloys – Copper/Nickel Alloys – Nickel-alloys.net
  6. Nickel Allergy – Corrosion-doctors.org
  7. 70/30 Cupronickel – Columbiametals.com
  8. Copper Nickel Alloy Wire Heating – Heating-element-alloy.com
  9. Coinage – Copper.org

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