Beryllium copper

Beryllium copper (BeCu), also known as copper beryllium (CuBe), beryllium bronze and spring copper, is a copper alloy with 0.5—3% beryllium and sometimes other elements. Beryllium copper combines high strength with non-magnetic and non-sparking qualities. It has excellent metalworking, forming and machining properties. It has many specialized applications in tools for hazardous environments, musical instruments, precision measurement devices, bullets, and aerospace. Beryllium alloys present a toxic inhalation hazard during manufacture.

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. It can be heat-treated for increased strength, durability, and electrical conductivity. Beryllium copper attains the greatest strength (to 1,400 MPa (200,000 psi)) of any copper-based alloy.[1]

Toxicity

In solid form and as finished objects, beryllium copper presents no known health hazard.[2] However, inhalation of dust, mist, or fume containing beryllium can cause a serious lung condition (chronic beryllium disease) in some sensitive individuals. Chronic beryllium disease is a condition that primarily affects the tissue of the lungs restricting the exchange of oxygen between the lungs and the bloodstream. The International Agency for Research on Cancer (IARC) lists beryllium as a Group 1 – Known Human Carcinogen. The National Toxicology Program (NTP) lists beryllium as known to be human carcinogens. (Both organizations also list aluminum and steel production, rubber manufacturing, chromium compounds, nickel compounds, wood dust, silica dust (fine sand containing quartz), leather dust, diesel exhaust and many others.)

Uses

Example of a non-sparking tool made of beryllium copper

Beryllium copper is a non-ferrous alloy used in springs, spring wire, load cells, and other parts that must retain their shape under repeated stress and strain. Because of its high electrical conductivity, it is used in low-current contacts for batteries and electrical connectors.

Beryllium copper is non-sparking but physically tough and nonmagnetic, fulfilling the requirements of ATEX directive for Zones 0, 1, and 2. Beryllium copper screwdrivers, pliers, wrenches, cold chisels, knives, and hammers are available for environments with explosive hazards, such oil rigs, coal mines, and grain elevators. An alternative metal sometimes used for non-sparking tools is aluminium bronze. Compared to steel tools, beryllium copper tools are more expensive, not as strong, and less durable. However, the advantages of beryllium copper in hazardous environments outweigh the disadvantages.

Beryllium copper is frequently used in the manufacture of professional-quality percussion instruments, especially tambourines and triangles, where it is prized for its clear tone and strong resonance. Unlike most other materials, beryllium copper maintains 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 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 been used for armour piercing bullets,[2] though such usage is unusual because bullets made from steel alloys are much less expensive and have similar properties.

Beryllium copper is used for measurement-while-drilling (MWD) tools in the directional drilling industry. A non-magnetic alloy is required, as magnetometers are used for field-strength data received from the tool.

Beryllium copper gaskets are used to create an RF-tight (resistant to radio frequency leakage), electronic seal on doors used with EMC testing and anechoic chambers.

For a time, beryllium copper was 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 difficult to find in current production, so vintage and pre-owned examples remain in demand.

Kiefer Plating (now long gone) of Elkhart, Indiana built some beryllium-copper trumpet bells for the Schilke Music Co. of Chicago. These seamless, light-weight produce a bright projecting sound, particularly noticeable with higher overtones.

Beryllium copper wire [3] is produced in many forms: round, square, flat and shaped, in coils, on spools and in straight lengths.

Beryllium copper valve seats, and valve guides are used in high performance four-stroke engines using coated titanium valves. BeCu dissipates heat from the valve up to 7 times faster than powdered steel or iron seats & guides. The softer BeCu seats also cushion the valves, which helps reduce wear of the coating on TI valves, thus increasing valve life.

Alloys

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) that 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. Provided in either the age-hardenable condition or as tempered ware, they are used in springs and wire where electrical conduction or retention of properties at elevated temperatures is important.

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 formed with 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 must be avoided because the alloy reaches an equilibrium phase that depletes the beryllide crystals and reduces the strength enhancement. The beryllides in cast alloys are similar to those in wrought alloys.

High conductivity beryllium copper alloys contain up to 0.7% beryllium, together with some nickel and cobalt. The thermal conductivity of these alloys is greater than aluminium and slightly less than pure copper. They are often used as electric contacts.[4]

Manufacturers

The global leading manufacturers of beryllium copper are Ulba Metallurgical, Le Bronze Industriel, IBC Advanced Alloys, NGK, and Brush Wellman (now Materion Corporation). Ulba manufactures beryllium master alloys. LBI manufactures extruded bars and bushings. IBC Advanced Alloys manufactures rods, plates, tubes, rings and bushings. NGK and Brush Wellman are the primary strip suppliers for electronics.

References

  1. ↑ Bauccio, Michael (Ed.). ASM Metals Reference Book, Third Edition. Materials Park, Ohio: ASM International. p. 445. ISBN 0-87170-478-1.
  2. 1 2 "Federal Law and AP Ammunition". Nucnews.net. Retrieved 2009-11-02.
  3. ↑ http://www.lfa-wire.com/berylliu.htm
  4. ↑ "Feature -- EDMing Beryllium Copper: An Introduction". Mmsonline.com. Retrieved 2010-10-17.

External links

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