Copper alloys
Copper alloys are alloys with copper as their principal component. They have high resistance to corrosion.
Due to its high electric conductivity, pure electrolytic copper is used mostly for making of electrical cables.
Compositions
The similarity in external appearance of the various alloys, along with the different combinations of elements used when making each alloy, can lead to confusion when categorizing the different compositions. There are as many as 400 different copper and copper-alloy compositions loosely grouped into the categories: copper, high copper alloy, brasses, bronzes, copper nickels, copper–nickel–zinc (nickel silver), leaded copper, and special alloys. The following table lists the principal alloying element for four of the more common types, along with the name for each type.
| Family | Principal alloying element | UNS numbers |
|---|---|---|
| Copper alloys, brass | Zinc (Zn) | C1xxxx–C4xxxx,C66400–C69800 |
| Phosphor bronzes | Tin (Sn) | C5xxxx |
| Aluminium bronzes | Aluminium (Al) | C60600–C64200 |
| Silicon bronzes | Silicon (Si) | C64700–C66100 |
| Copper nickel, nickel silvers | Nickel (Ni) | C7xxxx |
Some common Copper alloys[1]
| Name | Nominal composition[2] | Form and condition | Yield strength[3] | Tensile strength[4] | Elongation[5] | Hardness[6] | Comments |
|---|---|---|---|---|---|---|---|
| Copper (ASTM B1, B2, B3, B152, B124, R133) | Cu 99.9 | Annealed | 10 | 32 | 45 | 42 | Electrical equipment, roofing, screens |
| Cold-drawn | 40 | 45 | 15 | 90 | |||
| Cold-rolled | 40 | 46 | 5 | 100 | |||
| Gilding metal (ASTM B36) | Cu 95.0, Zn 5.0 | Cold-rolled | 50 | 56 | 5 | 114 | Coins, ammunition casings |
| Cartridge brass (ASTM B14, B19, B36, B134, B135) | Cu 70.0, Zn 30.0 | Cold-rolled | 63 | 76 | 8 | 155 | Good for cold-working; radiators, hardware, electrical |
| Phosphor bronze (ASTM B103, B139, B159) | Cu 70.0, Sn 10.0, P 0.25 | Spring temper | — | 122 | 4 | 241 | High fatigue-strength and spring qualities |
| Yellow or High brass (ASTM B36, B134, B135) | Cu 65.0, Zn 35.0 | Annealed | 18 | 48 | 60 | 55 | Good corrosion resistance |
| Cold-drawn | 55 | 70 | 15 | 115 | |||
| Cold-rolled (HT) | 60 | 74 | 10 | 180 | |||
| Manganese bronze (ASTM 138) | Cu 58.5, Zn 39.2, Fe 1.0, Sn 1.0, Mn 0.3 | Annealed | 30 | 60 | 30 | 95 | Forgings |
| Cold-drawn | 50 | 80 | 20 | 180 | |||
| Naval brass (ASTM B21) | Cu 60.0, Zn 39.25, Sn 0.75 | Annealed | 22 | 56 | 40 | 90 | Resistance to salt corrosion |
| Cold-drawn | 40 | 65 | 35 | 150 | |||
| Muntz metal (ASTM B111) | Cu 60.0, Zn 40.0 | Annealed | 20 | 54 | 45 | 80 | Condensor tubes |
| Aluminium bronze (ASTM B169 alloy A, B124, B150) | Cu 92.0, Al 8.0 | Annealed | 25 | 70 | 60 | 80 | — |
| Hard | 65 | 105 | 7 | 210 | |||
| Beryllium copper (ASTM B194, B196, B197) | Cu 97.75, Be 2.0, Co or Ni 0.25 | Annealed, solution-treated | 32 | 70 | 45 | B60 (Rockwell) | Electrical, valves, pumps |
| Cold-rolled | 104 | 110 | 5 | B81 (Rockwell) | |||
| Free-cutting brass | Cu 62.0, Zn 35.5, Pb 2.5 | Cold-drawn | 44 | 70 | 18 | B80 (Rockwell) | Screws, nuts, gears, keys |
| Nickel silver (ASTM B112) | Cu 65.0, Zn 17.0, Ni 18.0 | Annealed | 25 | 58 | 40 | 70 | Hardware |
| Cold-rolled | 70 | 85 | 4 | 170 | |||
| Nickel silver (ASTM B149) | Cu 76.5, Ni 12.5, Pb 9.0, Sn 2.0 | Cast | 18 | 35 | 15 | 55 | Easy to machine; ornaments, plumbing |
| Cupronickel (ASTM B111, B171) | Cu 88.35, Ni 10.0, Fe 1.25, Mn 0.4 | Annealed | 22 | 44 | 45 | – | Condensor, salt-water pipes |
| Cold-drawn tube | 57 | 60 | 15 | – | |||
| Cupronickel | Cu 70.0, Ni 30.0 | Wrought | – | – | – | – | Heat-exchange equipment, valves |
| Red brass (ASTM B30 4A) | Cu 85.0, Zn 5.0, Pb 5.0, Sn 5.0 | Cast | 17 | 35 | 25 | 60 | — |
Brasses
A brass is an alloy of copper with zinc. Brasses are usually yellow in color. The zinc content can vary between few % to about 40%; as long as it is kept under 15%, it does not markedly decrease corrosion resistance of copper.
Brasses can be sensitive to selective leaching corrosion under certain conditions, when zinc is leached from the alloy (dezincification), leaving behind a spongy copper structure.
Bronzes
A bronze is an alloy of copper and other metals, most often tin, but also aluminium and silicon.
- Aluminium bronzes are alloys of copper and aluminium. The content of aluminium ranges mostly between 5-11%. Iron, nickel, manganese and silicon are sometimes added. They have higher strength and corrosion resistance than other bronzes, especially in marine environment, and have low reactivity to sulfur compounds. Aluminium forms a thin passivation layer on the surface of the metal.
- Nickel bronzes, e.g. nickel silver and cupronickel
Precious metal alloys
Copper is often alloyed with precious metals like silver and gold, to create, for example, Corinthian bronze, hepatizon, tumbaga and shakudo.
See also
References
- Machinery's Handbook, Industrial Press Inc, New York, ISBN 0-8311-2492-X, Edition 24, page 501