Copper-Nickel-Silicon-Chromium (CuNi₂.₅SiCr)

Hardenable Copper Alloy With High Conductivity and Wear Resistance

The material combines high electrical conductivity with mechanical stability and corrosion resistance. Copper ensures low-loss current transmission, nickel increases strength and improves performance under electrical and mechanical load. Silicon suppresses oxidation, thereby minimizing thermally induced material loss. Chromium enhances thermal conductivity and contributes to corrosion resistance.

Compared to CuAl₂O₃, CuNiSiCr achieves higher strength and hardness. Unlike beryllium-containing alloys such as CuCoBe or CuCoNiBe, this alloy poses no health risks during machining or handling. The Ni-Si precipitates are considered non-hazardous and enable comparable performance.

Composition of Copper-Nickel-Silicon-Chromium

  • 29

    Copper

    Cu

    ≥ 96.2%

  • 28

    Nickel

    Ni

    2.3% – 2.7%

  • 14

    Silicon

    Si

    0.5% – 0.8%

  • 24

    Chromium

    Cr

    0.1% – 0.3%

Key Properties

  • Stress Relaxation Resistance

    CuNi2.5SiCr maintains significantly lower stress relaxation at temperatures above 150 °C compared to other copper alloys. This ensures long-term contact pressure stability, which is critical in spring contacts and mechanical joints under continuous load.

  • Corrosion Resistance

    The chromium content forms a protective oxide layer that reduces corrosion in harsh environments. CuNi2.5SiCr contacts remain maintenance-free even during long-term exposure to challenging conditions such as offshore platforms or marine electrical systems.

  • Thermal Stability

    With a recrystallization temperature of 650 °C, CuNi2.5SiCr outperforms CuBe in high-temperature applications. It withstands soldering processes involving thermal stress without compromising strength. This makes it suitable for electronic assembly processes requiring consistent mechanical properties throughout multiple thermal cycles.

Physical and Mechanical Properties

Property

Unit

Value

Tensile strength (Rm)

MPa

600–750

Yield strength (Rp0.2)

MPa

460–600

Elongation at break (A)

%

10–15

Elongation

%

≥ 25

Hardness (Brinell)

HBW 2.5/62.5

185–200

Hardness (Vickers)

HV

185–220

Electrical conductivity

MS/m

26–29

Electrical conductivity

% IACS

45–50

Density at 20°C

g/cm³

8.9

Melting temperature (liquidus)

°C

1070–1090

Linear thermal expansion coefficient (20–300 °C)

x10⁻⁶/K⁻¹

18

Elastic modulus

kN/mm²

140

Thermal conductivity at 20°C

W/(m·K)

220

Softening temperature

°C

475

These figures represent minimum values, typical averages or defined tolerance ranges. If your application requires specific material characteristics such as a defined hardness or higher flexibility, we will develop a suitable variant in close cooperation with you. Get in touch to discuss your specifications.

Industrial Applications

Typical use cases for CuNi₂.₅SiCr in industrial environments

  • Electrical Engineering

    CuNi2.5SiCr combines high electrical conductivity with thermal stability. These properties ensure reliable current transmission in continuous operation. The alloy is used in electrical contacts, connectors and conductive components.

  • Welding Technology

    The alloy's high softening point, mechanical strength and electrical conductivity make it suitable for seam welding wheels and electrode holders. It is a beryllium-free alternative to components made from Wirbalit B.

  • Aerospace

    The alloy combines heat resistance, mechanical strength and corrosion resistance. It is used in engine components, structural elements and fasteners that must retain dimensional stability under demanding thermal conditions.

  • Marine and Offshore Engineering

    CuNi2.5SiCr offers high resistance to seawater and aggressive media. It is used for valves, pumps, structural parts and shipboard systems where long-term corrosion resistance is required.

  • Die Casting

    Its dimensional stability under thermal and mechanical cycling makes CuNi2.5SiCr suitable for pistons, system parts and components exposed to sustained high temperatures in die-casting processes.

CuNiSiCr Welding Parts

Manufacturing Process

The production of a CuNi2.5SiCr rod involves multiple steps to achieve the desired material properties.

  • 1
    Step 1

    Alloy preparation and melting

    High-purity copper, nickel, silicon and chromium are melted in a high-temperature furnace to form the alloy. The exact composition is adjusted to meet material specifications.

  • 2
    Step 2

    Casting

    The molten alloy is cast into moulds using either continuous or block casting. Solidification is carefully controlled to promote a fine-grained microstructure and prevent shrinkage cavities or segregation.

  • 3
    Step 3

    Hot forming

    The solidified ingots are heated and passed through a series of rolling mills. This plastic deformation improves workability and further refines the grain structure.

  • 4
    Step 4

    Solution annealing

    The material is heated to 800–950 °C and rapidly quenched. This process dissolves nickel and silicon in the copper matrix, setting the basis for subsequent precipitation hardening.

  • 5
    Step 5

    Cold drawing

    The rods are cold drawn through dies to achieve final dimensions and surface finish. Cold working also increases strength.

  • 6
    Step 6

    Precipitation hardening

    A controlled heat treatment is applied to increase hardness and enhance the surface condition.

  • 7
    Step 7

    Surface treatment

    Residual contaminants are removed by grinding, polishing or chemical surface treatments, depending on the application.

  • 8
    Step 8

    Quality control

    All manufacturing steps are subject to strict quality monitoring to ensure that CuNi2.5SiCr rods meet the required mechanical and physical properties.

  • 9
    Step 9

    Packaging and shipping

    Finished rods are packed using protective materials to prevent damage during transport. Packaging is selected based on shipment type and customer requirements.

This process ensures that CuNi2.5SiCr rods develop the material characteristics required for industrial use. These include high mechanical strength, reliable electrical and thermal conductivity, and resistance to wear.

Talk to Our Material Specialists

In close cooperation with you, we analyse your requirements, provide comprehensive guidance and find the solution that fits your process best.

Contact us