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Beryllium copper: Wikis

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Beryllium copper, also known as copper beryllium, BeCu or beryllium bronze, is a metal alloy of copper and 0.5 to 3% beryllium, and sometimes with other alloying elements. Beryllium Copper combines high strength with non-magnetic and non-sparking qualities. It has excellent metalworking, forming and machining qualities. It has many specialized applications in tools for hazardous environments, musical instruments, precision measurement devices, bullets, and aerospace. Beryllium-containing alloys create an inhalation hazard during manufacturing due to their toxic properties.

Contents

Properties

Beryllium copper is a ductile, weldable, and machinable alloy. It is resistant to non-oxidizing acids (for example, hydrochloric acid, or carbonic acid), to plastic decomposition products, to abrasive wear and to galling. Furthermore, it can be heat-treated to improve its strength, durability, and electrical conductivity. Beryllium copper attains the highest strength (to 1,400 MPa (200,000 psi)) of any copper-based alloy[1].

As beryllium compounds are toxic there are some safety concerns for handling its alloys. In solid form and as finished parts, beryllium copper presents no particular health hazard. However, breathing its dust, as formed when machining or welding may cause serious lung damage.[2] Beryllium compounds are known human carcinogens when inhaled.[3] As a result, beryllium copper is sometimes replaced by safer copper alloys such as Cu-Ni-Sn bronze.[4]

Uses

Beryllium copper is a non-ferrous alloy used in springs, spring wire, load cells and other parts that must retain their shapes during periods in which they are subjected to repeated stress and strain. Due to its electrical conductivity, it is used in low-current contacts for batteries and electrical connectors. Because Beryllium copper is non-sparking but physically tough and nonmagnetic, it is used to make tools that can safely be used in environments where there are explosive vapors and gases e.g. oil rigs. Various tool types are available e.g. screwdrivers, pliers, spanners, cold chisels and hammers.[5] Another metal sometimes used for non-sparking tools is aluminum bronze. Compared to tools made of steel, beryllium copper tools are more expensive, not as strong and wear out more quickly. However, the advantages of using beryllium copper in hazardous environments outweigh these disadvantages.

Example of a non-sparking tool

Alloy 25 beryllium copper (C17200 & C17300) is an age-hardening alloy which attains the highest strength of any copper base alloy. It may be age hardened after forming into springs, intricate forms or complex shapes. It has superb spring properties, corrosion resistance and stability as well as good conductivity and low creep.

Tempered beryllium copper is Alloy 25 (C17200 & C17300) which has been age hardened and cold drawn. No further heat treatment is necessary except for a possible light stress relief. It is sufficiently ductile to wind on its own diameter and can be formed into springs and most shapes. Tempered wire is most useful where the properties of beryllium copper are desired but age hardening of finished parts is not practical.

Alloys 3 (C17510) and 10 (C17500) beryllium copper are age-hardenable and provide excellent electrical conductivity in combination with good physical properties and endurance strength. Provided In either the age-hardenable condition or as tempered ware, they are used in springs and wire forms which are electrical conductors or where retention of properties at elevated temperatures is Important.

Beryllium copper is also frequently used in the manufacture of professional-quality percussion instruments, especially tambourine and triangle, where it is prized for its clear tone and strong resonance. Unlike most other materials, an instrument composed of beryllium copper will maintain a consistent tone and timbre for as long as the material resonates. The "feel" of such instruments is rich and melodious to the point that they seem out of place when used in darker, more rhythmic pieces of classical music.

Beryllium copper has also found use in ultra-low temperature cryogenic equipment, such as dilution refrigerators, because of its combination of mechanical strength and relatively high thermal conductivity in this temperature range.

Beryllium copper has also been used for armour piercing bullets,[6] though any such usage is unusual because bullets made from steel alloys are much less expensive, but have similar properties.

Beryllium copper is also used for measurement-while-drilling tools in the directional (slant drilling) drilling industry. A non-magnetic alloy is required as magnetometers are used for calculations received from the tool.

For a time, beryllium copper was also used in the manufacture of golf clubs, with emphasis on wedges and putters. Many golfers prefer the soft feel of BeCu club heads, particularly for chip shots and putts around and on the green, where an extra measure of control is desired. Due to regulatory issues and high costs, BeCu clubs are hard to find in current production. Vintage and pre-owned examples remain in demand at used club shops and on Internet auction sites.

Alloys

High strength beryllium copper alloys contain up to 2.7% of beryllium (cast), or 1.6-2% of beryllium with about 0.3% cobalt (wrought). The high mechanical strength is achieved by precipitation hardening or age hardening. The thermal conductivity of these alloys lies between steels and aluminium. The cast alloys are frequently used as material for injection molds. The wrought alloys are designated by UNS as C17200 to C17400, the cast alloys are C82000 to C82800. The hardening process requires rapid cooling of the annealed metal, resulting in a solid state solution of beryllium in copper, which is then kept at 200-460 °C for at least an hour, facilitating precipitation of metastable beryllide crystals in the copper matrix. Overaging is avoided, as an equilibrium phase forms that depletes the beryllide crystals and reduces the strength enhancement. The beryllides are similar in both cast and wrought alloys.

High conductivity beryllium copper alloys contain up to 0.7% beryllium, together with some nickel and cobalt. Their thermal conductivity is better than of aluminium, only a bit less than pure copper. They are usually used as electric contacts in connectors. [7]

References

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