Cupronickel
Cupronickel or copper–nickel (CuNi) is an alloy of copper with nickel, usually along with small quantities of other elements added for strength, such as iron and manganese. The copper content typically varies from 60 to 90 percent. (Monel is a nickel–copper alloy that contains a minimum of 52 percent nickel.)
Despite its high copper content, cupronickel is silver in colour. Cupronickel is highly resistant to corrosion by salt water, and is therefore used for piping, heat exchangers and condensers in seawater systems, as well as for marine hardware. It is sometimes used for the propellers, propeller shafts, and hulls of high-quality boats. Other uses include military equipment and chemical, petrochemical, and electrical industries.[1]
Another common 20th-century use of cupronickel was silver-coloured coins. For this use, the typical alloy has 3:1 copper to nickel ratio, with very small amounts of manganese.
In the past, true silver coins were debased with cupronickel, such as coins of the pound sterling from 1947 onward having their content replaced.
Name
Aside from cupronickel and copper–nickel, several other terms have been used to describe the material: the tradenames Alpaka or Alpacca, Argentan Minargent, the registered
Applications
Marine engineering
Cupronickel alloys are used for marine applications
Important marine applications for cupronickel include:
- Shipbuilding and repair: hulls of boats and ships, seawater cooling, bilge and ballast, sanitary, fire fighting, inert gas, hydraulic and pneumatic chiller systems.[5][6]
- Desalination plants: brine heaters, heat rejection and recovery, and in evaporator tubing.[7]
- FPSO vessels: systems and splash zone sheathings.[8]
- Power generation: steam turbine condensers, oil coolers, auxiliary cooling systems and high pressure pre-heaters at nuclear and fossil fuel power plants.[9]
- Seawater system components: condenser and heat exchanger tubes, tube sheets, piping, high pressure systems, fittings, pumps, and water boxes.[10][11]
Coinage
The successful use of cupronickel in coinage is due to its
In Europe,
In part due to silver hoarding in the Civil War, the United States Mint first used cupronickel for circulating coinage in
Other usage
A thermocouple junction is formed from a pair of thermocouple conductors such as iron-constantan, copper-constantan or nickel-chromium/nickel-aluminium. The junction may be protected within a sheath of copper, cupronickel or stainless steel.[22]
Cupronickel is used in
Beginning around the turn of the 20th century,
Currently, cupronickel and
For high-quality
Cupronickel has been used as an alternative to traditional steel hydraulic brake lines (the pipes containing the brake fluid), as it does not rust. Since cupronickel is much softer than steel, it bends and flares more easily, and the same property allows it to form a better seal with hydraulic components.
Properties
Cupronickel lacks a copper color due to nickel's high electronegativity, which causes a loss of one electron in copper's d-shell (leaving 9 electrons in the d-shell versus pure copper's typical 10 electrons).
Important properties of cupronickel alloys include
Alloy UNS No. | Common name | European spec | Ni[29] | Fe[29] | Mn[29] | Cu | Density g/cm3 |
Thermal conductivity W/(m·K) |
TEC μm/(m·K) |
Electrical resistivity μOhm·cm |
Elastic modulus GPa |
Yield strength MPa |
Tensile strength MPa |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
C70600 | 90–10 | Cu90Ni10 | 9–11 | 1–1.8 | 1 | Balance | 8.9 | 40 | 17 | 19 | 135 | 105 | 275 |
C71500 | 70–30 | Cu70Ni30 | 29–33 | 0.4–1.0 | 1 | Balance | 8.95 | 29 | 16 | 34 | 152 | 125 | 360 |
C71640 | 66–30–2–2 | Cu66Ni30Fe2Mn2 | 29–32 | 1.7–2.3 | 1.5–2.5 | Balance | 8.86 | 25 | 15.5 | 50 | 156 | 170 | 435 |
Subtle differences in corrosion resistance and strength determine which alloy is selected. Descending the table, the maximum allowable flow rate in piping increases, as does the tensile strength.
In seawater, the alloys have excellent corrosion rates which remain low as long as the maximum design flow
However, Cu–Ni alloys can show high corrosion rates in polluted or stagnant seawater when
As copper and nickel alloy with each other easily and have simple structures, the alloys are ductile and readily fabricated. Strength and hardness for each individual alloy is increased by
Applications for Cu–Ni alloys have withstood the test of time, as they are still widely used and range from seawater system piping, condensers and
Fabrication
Due to its
Details of fabrication procedures, including general handling, cutting and machining, forming, heat treatment, preparing for welding, weld preparations, tack welding, welding consumables, welding processes, painting, mechanical properties of welds, and tube and pipe bending are available.[31]
Standards
Thermocouples and resistors whose resistance is stable across changes in temperature contain alloy constantan, which consists of 55% copper and 45% nickel.
History
Chinese history
Cupronickel alloys were known as "white copper" to the Chinese since about the third century BC. Some weapons made during the Warring States period were made with Cu-Ni alloys.[33] The theory of Chinese origins of Bactrian cupronickel was suggested in 1868 by Flight, who found that the coins considered the oldest cupronickel coins yet discovered were of a very similar alloy to Chinese paktong.[34]
The author-scholar, Ho Wei, precisely described the process of making cupronickel in about 1095 AD. The paktong alloy was described as being made by adding small pills of naturally occurring yunnan ore to a bath of molten copper. When a crust of
"San Mao Chun were at Tanyang during a famine year when many people died, so taking certain chemicals, Ying projected them onto silver, turning it into gold, and he also transmuted iron into silver – thus enabling the lives of many to be saved [through purchasing grain through this fake silver and gold] Thereafter all those who prepared chemical powders by heating and transmuting copper by projection called their methods "Tanyang techniques".[34]
The late Ming and Qing literature have very little information about paktong. However, it is first mentioned specifically by name in the Thien Kung Khai Wu of circa 1637:
"When lu kan shih (zinc carbonate, calamine) or wo chhein (zinc metal) is mixed and combined with chih thung (copper), one gets 'yellow bronze' (ordinary brass). When phi shang and other arsenic substances are heated with it, one gets 'white bronze' or white copper: pai thong. When alum and niter and other chemicals are mixed together one gets ching thung: green bronze."[34]
Ko Hung stated in 300 AD: "The Tanyang copper was created by throwing a mercuric elixir into Tanyang copper and heated- gold will be formed." However, the Pha Phu Tsu and the Shen I Ching describing a statue in the Western provinces as being of silver, tin, lead and Tanyang copper – which looked like gold, and could be forged for plating and inlaying vessels and swords.[34]
Joseph Needham et al. argue that cupronickel was at least known as a unique alloy by the Chinese during the reign of Liu An in 120 BC in Yunnan. Moreover, the Yunnanese State of Tien was founded in 334 BC as a colony of the Chu. Most likely, modern paktong was unknown to Chinese of the day – but the naturally occurring Yunnan ore cupronickel alloy was likely a valuable internal trade commodity.[34]
Greco-Bactrian coinage
In 1868, W. Flight discovered a Greco-Bactrian coin comprising 20% nickel that dated from 180 to 170 BCE with the bust of Euthydemus II on the obverse. Coins of a similar alloy with busts of his younger brothers, Pantaleon and Agathocles, were minted around 170 BCE. The composition of the coins was later verified using the traditional wet method and X-ray fluorescence spectrometry.[34] Cunningham in 1873 proposed the "Bactrian nickel theory," which suggested that the coins must have been the result of overland trade from China through India to Greece. Cunningham's theory was supported by scholars such as W. W. Tarn, Sir John Marshall, and J. Newton Friend, but was criticized by E. R. Caley and S. van R. Cammann.[34]
In 1973, Cheng and Schwitter in their new analyses suggested that the Bactrian alloys (copper, lead, iron, nickel and cobalt) were closely similar to the Chinese paktong, and of nine known Asian nickel deposits, only those in China could provide the identical chemical compositions.[34] Cammann criticized Cheng and Schwitter's paper, arguing that the decline of cupronickel currency should not have coincided with the opening of the Silk Road. If the Bactrian nickel theory were true, according to Cammann, the Silk Road would have increased the supply of cupronickel. However, the end of Greco-Bactrian cupronickel currency could be attributed to other factors such as the end of the House of Euthydemus.[34]
European history
The alloy seems to have been rediscovered by the West during alchemy experiments. Notably, Andreas Libavius, in his Alchemia of 1597, mentions a surface-whitened copper aes album by mercury or silver. But in De Natura Metallorum in Singalarum Part 1, published in 1599, the same term was applied to "tin" from the East Indies (modern-day Indonesia and the Philippines) and given the Spanish name, tintinaso.[34]
Richard Watson of Cambridge appears to be the first to discover that cupronickel was an alloy of three metals. In attempting to rediscover the secret of white-copper, Watson critiqued Jean-Baptiste Du Halde's History of China (1688) as confusing the term paktong'., He noted the Chinese of his day did not form it as an alloy but rather smelted readily available unprocessed ore:
"...appeared from a vast series of experiments made at Peking- that it occurred naturally as an ore mined at the region, the most extraordinary copper is pe-tong or white copper: it is white when dug out of the mine and even more white within than without. It appears, by a vast number of experiments made at Peking, that its colour is owing to no mixture; on the contrary, all mixtures diminish its beauty, for, when it is rightly managed it looks exactly like silver and were there not a necessity of mixing a little tutenag or such metal to soften it, it would be so much more the extraordinary as this sort of copper is found no where but in China and that only in the Province of Yunnan". Notwithstanding what is here said, of the colour of the copper being owing to no mixture, it is certain the Chinese white copper as brought to us, is a mixt [sic: mixed] metal; so that the ore from which it was extracted must consist of various metallic substances; and from such ore that the natural orichalcum if it ever existed, was made."[34]
During the peak European importation of Chinese white-copper from 1750 to 1800, increased attention was made to its discovering its constituents. Peat and Cookson found that "the darkest proved to contain 7.7% nickel and the lightest said to be indistinguishable from silver with a characteristic bell-like resonance when struck and considerable resistance to corrosion, 11.1%".
Another trial by Andrew Fyfe estimated the nickel content at 31.6%. Guesswork ended when James Dinwiddie of the Macartney Embassy brought back in 1793, at considerable personal risk (smuggling of paktong ore was a capital crime by the Chinese Emperor), some of the ore from which paktong was made.[35] Cupronickel became widely understood, as published by E. Thomason, in 1823, in a submission, later rejected for not being new knowledge, to the Royal Society of Arts.
Efforts in Europe to exactly duplicate the Chinese paktong failed due to a general lack of requisite complex cobalt–nickel–arsenic naturally occurring ore. However, the
At the same time, the
In 1829, Percival Norton Johnston persuaded Dr. Geitner to establish a foundry in Bow Common behind Regents' Park Canal in London, and obtained ingots of nickel-silver with the composition 18% Ni, 55% Cu and 27% Zn.[35]
Between 1829 and 1833, Percival Norton Johnson was the first person to refine cupronickel on the British Isles. He became a wealthy man, producing in excess of 16.5 tonnes per year. The alloy was mainly made into cutlery by the Birmingham firm William Hutton and sold under the trade-name "Argentine".
Johnsons' most serious competitors, Charles Askin and Brok Evans, under the brilliant chemist Dr. EW Benson, devised greatly improved methods of cobalt and nickel suspension and marketed their own brand of nickel-silver, called "British Plate".[35]
By the 1920s, a 70–30 copper–nickel grade was developed for naval condensers. Soon afterwards, a 2% manganese and 2% iron alloy now known as alloy C71640 was introduced for a UK power station which needed better erosion resistance because the levels of entrained sand in the seawater. A 90–10 alloy first became available in the 1950s, initially for seawater piping, and is now the more widely used alloy.
See also
- Brass (copper alloyed with zinc)
- Bronze (copper alloyed with tin)
- Copper alloys in aquaculture
- Freeze branding
References
- ^ Sakiewicz P.,Nowosielski R., Babilas R. Production aspects of inhomogeneous hot deformation in as-cast CuNi25 alloy, Indian Journal of Engineering & Materials Sciences, Vol. 22, August 2015, pp. 389-398
- ^ Deutsches Kupfer-Institut (Hrsg.): Kupfer-Nickel-Zink-Legierungen. Berlin 1980.
- ^ Marine Applications for Copper-Nickel Alloys http://www.copper.org/applications/marine/cuni/applications/#non_marine
- ^ Kobelco: Copper alloy tubes for heat-exchanger; Shinko Metal Products, Japan; http://www.shinkometal.co.jp/catalog/copperalloy-en-sc.pdf Archived 2013-10-29 at the Wayback Machine
- ^ Copper-Nickel Alloys in Boat and Ship Hulls http://www.copper.org/applications/marine/cuni/applications/hulls/
- ^ Copper-Nickel Alloys in Shipbuilding and Repair http://www.copper.org/applications/marine/cuni/applications/shipbuilding_and_repair/
- ^ Copper-Nickel Alloys in Desalination Plants http://www.copper.org/applications/marine/cuni/applications/desalination_plants/
- ^ Copper-Nickel Alloys in Offshore Oil and Gas Platforms and Processing http://www.copper.org/applications/marine/cuni/applications/offshore_oil_and_gas/
- ^ Copper-Nickel Alloys in Power Generation http://www.copper.org/applications/marine/cuni/applications/power_generation/
- ^ Copper-Nickel Alloys in Seawater System Design http://www.copper.org/applications/marine/cuni/applications/seawater_system_design/
- ^ Copper-Nickel Alloys in Seawater System Components http://www.copper.org/applications/marine/cuni/applications/seawater_system_components/
- ^ Copper-Nickel in Coinage
- ^ "5 Rappen (Coat of arms)".
- ^ "10 Centimes - Léopold I".
- ^ "20 Centimes - Léopold I".
- ^ "10 Pfennig Wilhelm I".
- ^ "5 Rappen Libertas; copper-nickel".
- ^ United States. Bureau of the Mint (1881). "Report of the Director of the Mint Upon the Statistics of the Production of the Precious Metals in the United States". p. 268. Retrieved 2024-02-08.
- ^ "1 Franc (Helvetia)".
- ^ "The United States Mint: Coin Specifications". Archived from the original on 2009-11-11. Retrieved 2008-06-11.
- ^ "Currency in Circulation: Introduction to Coins". Archived from the original on 2014-12-31. Retrieved 2010-09-27.
- ISBN 0-86341-001-4, p. 161
- ^ Cryogenic Properties of Copper-Nickel copper.org
- ^ Low-Temperature Properties of Copper and Copper Alloys copper.org
- ^ Mechanical Properties of Copper and Copper Alloys at Low Temperatures copper.org
- JSTOR 3799102.
- ^ Properties of Copper–Nickel Alloys http://www.copper.org/applications/marine/cuni/properties/
- ^ Physical Properties of Copper-Nickel
- ^ a b c Component values may vary in other standards.
- ^ "Copper-Nickel Alloy Product Forms". Copper Development Association Inc.
- ^ "Copper-Nickel Alloy Fabrication". Copper Development Association Inc.
- ^ Copper-Nickel Standards http://www.copper.org/applications/marine/cuni/standards/
- ^ Ancient Chinese weapons Archived 2005-03-07 at the Wayback Machine and A halberd of copper-nickel alloy, from the Warring States Period. Archived 2012-05-27 at archive.today
- ^ ISBN 0-521-08571-3, pp. 237–250
- ^ ISBN 0-203-19211-7: pp98
External links
- Copper-Nickel Alloys
- Copper-Nickel-Alloys: Properties, Processing, Applications (Source: German Copper Institute (DKI))]
- Copper-Nickel Alloys for Seawater Corrosion Resistance and Antifouling - A State of the Art Review (C.A. Powell and H.T. Michels; Corrosion 2000, NACE March 2000 ( NACE))