Copper & copper alloys

About the material

Copper and its alloys are among the oldest technical materials – and are still indispensable today, particularly in electrical engineering, precision engineering and the watchmaking industry. Pure copper offers the highest electrical and thermal conductivity of all metals in industrial use. In addition, it offers excellent formability and natural corrosion resistance.

Through targeted alloying with elements such as zinc, tin, nickel or beryllium, the properties of copper can be significantly expanded – for example, to achieve higher strength, improved relaxation resistance or increased wear resistance.

Studer-Biennaform processes copper grades into cold-rolled precision flat wire. This is used as electrical conductors, in spring contacts, connectors, decorative components or as a precision element in watches – wherever reliability, shaping accuracy and conductivity are crucial.

Pure copper

Electrolytic copper Cu-ETP (EN CW004A) and oxygen-free copper Cu-OF (CW008A) are among the most important pure copper grades for technical applications.
Cu-ETP contains at least 99.90% copper and approximately 0.02–0.04% oxygen. When soft-annealed, it achieves an electrical conductivity of almost 100% IACS (International Annealed Copper Standard, approx. 58 MS/m), making it the standard grade for conductive components in electrical engineering and power transmission.

At 99.99%, Cu-OF is even purer and is completely deoxidised (O < 0.001%). As a result, it also offers approximately 100% IACS, but is insensitive to hydrogen embrittlement – an advantage in high-temperature applications and in a vacuum. When heated in a controlled environment, the alloy does not form any copper oxide or brittle phases and remains ductile even in red heat, making it suitable for particularly demanding applications.

Both grades are non-magnetic, have good cold formability and have a moderate level of strength when soft (tensile strength approx. 200–250 MPa, significantly higher when work-hardened). The surface quality is very high – Cu-ETP and Cu-OF can be polished, coated, plated and structured.

Typical applications:

• Cu-ETP: busbars, contact springs, cables and stranded wires, connecting cables, transformer windings, motor coils, printed plates – wherever low line losses are critical.
• Cu-OF: welding electrodes, high-vacuum components, mirror holders in laser devices, heat conduction rails or ductile components for high-temperature areas. Cu-OF also offers advantages in precision engineering – e.g. for flexible spring contacts or mirror-polished functional parts.

Pure copper plays only a minor role in the watchmaking industry, but is used in certain special applications. Both grades can be easily electroplated (e.g. silver plating for electrical contacts) and anodised for decorative purposes, resulting in colourless oxide layers.

Brass

Brass refers to copper alloys with typically 5–40% zinc. Depending on the composition, the mechanical properties, formability and colour can be specifically influenced. Known grades include CuZn36 (CW507L) and CuZn37 (CW508L) as classic wrought brass and CuZn39Pb3 (CW614N), a leaded machining brass.

As the zinc content increases, the strength raises significantly, while the colour changes from reddish (at low zinc) to bright yellow. Brass with approximately 37–39% zinc offers high mechanical strength with sufficient ductility. Above 40%, the cold formability decreases noticeably. At the same time, zinc improves pressure formability at raised temperatures – for example, when hot pressing brass bars. All types of brass are non-magnetic and offer good to very good corrosion resistance to air, water and many saline solutions.

Brass is an extremely versatile material. Its gold-like colour makes it ideal for decorative applications, such as cases and dials in the watchmaking and jewellery industry, musical instruments, fittings and visually demanding elements in interior design.

Brass is widely used in the technical field:

• CuZn39Pb3 (machining brass) is processed on automatic lathes for precision parts such as gears, valves, threaded bushings or watch movements.
• Brass cooling pipes, connectors and contacts are used in the automotive industry.
• CuZn36 and CuZn37 are standard grades for stamped and bent parts such as sheet metal sleeves, clips, clamps and screws.

Thanks to its formability, good machinability and attractive appearance, brass is a tried-and-tested material in terms of both function and design.

Copper beryllium

Copper-beryllium alloys such as CuBe2 combine mechanical strength and electrical conductivity at a level that is otherwise rarely achieved simultaneously with copper grades. These alloys offer exceptionally high spring force combined with very good fatigue resistance and relaxation resistance.

CuBe has excellent flexural strength and remains dimensionally stable even under dynamic continuous loads. The relaxation resistance is outstanding – even at temperatures of up to around 200 °C, CuBe springs largely maintain their tension. As a result, they clearly outperform classic alloys such as bronze or brass. At the same time, CuBe is corrosion-resistant and forms a protective oxide layer to the air. The material is non-magnetic and can be processed without sparks.

Typical applications:

• Electronics: miniature springs, contact blades, connector pins, relay springs, battery contacts – wherever high conductivity has to be combined with a defined spring resistance.
• Measurement technology and sensors: pressure measuring springs and similar resistant elements that must remain stable over the long term and retain their shape.
• Medical technology: MRI-capable surgical tools and instruments where non-sparking and non-magnetism are required.
• Watchmaking industry: special watch springs (e.g. torsion springs, coil springs in complications) that remain vibration-resistant for decades.
• Aerospace: contact springs, valve components, spring retainers in vibrating environments – anywhere failure has to be ruled out.

This makes copper beryllium a high-performance material for resistant, highly stressed precision elements – reliable, durable and versatile.