In the fully heat treated and cold worked condition beryllium-copper is the hardest (HV 100-420) and strongest (tensile strength 410-1400 N/mm2) of any copper alloy.
It is similar in mechanical properties to many high strength steels but, compared to steels, it has better corrosion resistance (approximately equivalent to nickel-silvers), higher electrical conductivity (16-65% IACS) and higher thermal conductivity (210W/moC). It is also non-sparking and non-magnetic. Beryllium-copper should only be specified where its unique combination of properties can be fully exploited.
Beryllium-copper has long been used for non-sparking tools in the mining, gas and petrochemical industries.
Because of the excellent fatigue resistance, beryllium-copper is widely used for springs, pressure responsive diaphragms, flexible bellows, connectors, contacts and relays, which are all subject to cyclical loading.
The anti-galling, strength and good corrosion resistance led to the widespread use of beryllium-copper for down-hole drilling tools for the oil and gas industry.
Smaller component size has become the main design criterion in the telecommunications and computer electronics markets. Companies are constantly looking for ways to reduce the size and weight of their products, such as mobile phones, iPads, tablets and lap-tops, without sacrificing performance. The unique combination of strength, electrical and thermal conductivity of beryllium-copper make it an ideal choice for miniaturised components in the above applications.
The main product forms for beryllium-copper are sheet, strip, wire, rod, tube and forgings. Castings are available.
Health and Safety
The inhalation of beryllium in a finely divided form can cause a serious lung condition in some individuals. Precautions must therefore be taken in melting, casting, machining and welding of beryllium-copper. However, in service beryllium-copper is perfectly safe to handle and use.
Brush Alloy 25 offers high strength and excellent corrosion resistance in combination with galling resistance, magnetic transparency, resiliency and high hardness, making it the material of choice for downhole drilling, production and completion tools. Photo courtesy of Brush Wellman Inc.
The only copper alloys to meet the hardness requirement are the CuBe alloys. The alloy CW101C, (CuBe2, UNS C17200) when aged at 315oC will have the required hardness.
Copper strip and wire may be produced with a combination of high elastic limit and good corrosion resistance, making them an ideal choice for springs. The main groups of alloys are:
- Phosphor bronze, typically CW451K (PB102) with a yield strength of about 500 N/mm2.
- Nickel-silver, typically CW409J (NS106).This is silver coloured and has excellent tarnish resistance.
- Copper-beryllium CW100C (CB101). This alloy is used where very high yield strength is required (greater than 1000 N/mm2). These alloys are expensive and phosphor bronze will be adequate for most engineering applications.
A useful Specification is BS EN 1654:1998 (Copper and copper alloys. Strip for springs and connectors).
Publication 120 summarises the main compositions and the range of properties for the most commonly specified copper and copper alloys.
For equivalents of copper alloys worldwide, their chemical compositions, material designation and national standards