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.

Adjustable Wrench with 'BeCu' on the side, to show that it is made from beryllium copper

Properties

Beryllium copper is a ductile, weldable, and machinable alloy. Like pure copper, it is resistant to non-oxidizing acids like hydrochloric acid and 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] It has good thermal conductivity (62 Btu/ft-deg.F-H) 3-5 times more than Tool steel.

Toxicity

In solid form and as finished objects, beryllium copper presents no known health hazard. However, inhalation of dust, mist, or fume containing beryllium can cause the serious lung condition, chronic beryllium disease. That disease affects primarily 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 Human Carcinogen. The National Toxicology Program (NTP) also lists beryllium as a carcinogen.

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. It has high electrical conductivity, and 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 as 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 and not as strong, but the properties of beryllium copper in hazardous environments may outweigh the disadvantages. Some other uses include:

  • Some percussion instruments for its consistent tone and resonance, especially tambourines and triangles.
  • Ultra-low temperature cryogenic equipment, such as dilution refrigerators, because of its mechanical strength and relatively high thermal conductivity in this temperature range.
  • Moulds for manufacturing plastic containers (including virtually every plastic milk jug), with the blow molding process.
  • Armour piercing bullets,[2] though such usage is unusual because bullets made from steel alloys are much less expensive and have similar properties.
  • 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. Also for its high strength combined with anti-galling properties.
  • Servicing magnetic resonance imaging (mri) machines, where high strength magnetic fields make the use of ferrous tools dangerous, and where magnetic materials in the field can disturb the image.
  • Gaskets 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, particularly wedges and putters. Though some golfers prefer the feel of BeCu club heads, regulatory issues and high costs have made BeCu clubs difficult to find in current production.
  • Kiefer Plating (defunct) of Elkhart, Indiana built beryllium-copper trumpet bells for the Schilke Music Co. of Chicago. These light-weight bells produce a sound preferred by some musicians.

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 guides are used in high performance four-stroke engines with coated titanium valves. BeCu dissipates heat from the valve as much as seven times faster than powdered steel or iron seats & guides. The softer BeCu reduces valve wear and increases valve life.

Alloys

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 is valued for spring properties, corrosion resistance, stability, conductivity, and low creep.

Tempered beryllium copper is C17200 & C17300 that has been age hardened and cold drawn. No further heat treatment is necessary beyond 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.

C17510 and C17500 beryllium copper alloys are age-hardenable and provide good electrical conductivity, physical properties, and endurance. 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 as much as 2.7% beryllium (cast), or 1.6-2% beryllium with about 0.3% cobalt (wrought). The strength is achieved by 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, producing a precipitation of metastable beryllide crystals in the copper matrix. Overaging beyond the equilibrium phase depletes the beryllide crystals and reduces the strength. The beryllides in cast alloys are similar to those in wrought alloys.

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

References
  1. Bauccio, Michael (Ed.). ASM Metals Reference Book, Third Edition. Materials Park, Ohio: ASM International. p. 445. ISBN 0-87170-478-1.CS1 maint: extra text: authors list (link)
  2. "Federal Law and AP Ammunition". Nucnews.net. Archived from the original on 2009-11-14. Retrieved 2009-11-02.
  3. "Archived copy". Archived from the original on 2009-06-27. Retrieved 2009-05-08.CS1 maint: archived copy as title (link)
  4. "Feature -- EDMing Beryllium Copper: An Introduction". Mmsonline.com. Archived from the original on 2011-06-14. Retrieved 2010-10-17.
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