Nickel silver

Nickel silver is a cupronickel (copper with nickel) alloy with the addition of zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver does not contain the element silver. It is named for its silvery appearance, which can make it attractive as a cheaper and more durable substitute. It is also well suited for being plated with silver.

A naturally occurring ore composition in China was smelted into the alloy known as paktong or báitóng (白銅) ('white copper' or cupronickel). The name German Silver refers to the artificial recreation of the natural ore composition by German metallurgists. All modern, commercially important, nickel silvers (such as those standardized under ASTM B122) contain zinc and are sometimes considered a subset of brass.

Nickel silver

General characteristics

Composition Copper (majority, from 45% to 65%), nickel (minority: from 5% to 25%, 5% minimum), zinc (minority, from 20% to 45%) and sometimes lead (very low)

Uses Cutlery, Coin, Key Keywork (d) Musical instrument

Physical characteristics

Density 8,600 kilograms per cubic meter, 8,750 kilograms per cubic meter

Mechanical characteristics

Hardness 75,190

Thermal characteristics

Melting point 980 degrees Celsius, 1110 degrees Celsius

History

Nickel silver was first used in China, where it was smelted from readily available unprocessed ore. During the Qing dynasty, it was "smuggled into various parts of the East Indies", despite a government ban on the export of nickel silver. It became known in the West from imported wares called baitong (Mandarin) or paktong (Cantonese) (白 銅, literally "white copper"), for which the silvery metal colour was used to imitate sterling silver. According to Berthold Laufer, it was identical to khar sini, one of the seven metals recognized by Jābir ibn Hayyān.

In Europe, consequently, it was at first called paktong, which is about the way baitong is pronounced in the Cantonese dialect. The earliest European mention of paktong occurs in the year 1597. From then until the end of the eighteenth century there are references to it as having been exported from Canton to Europe.

German artificial recreation of the natural paktong ore composition, however, began to appear from about 1750 onward. In 1770, the Suhl metalworks were able to produce a similar alloy. In 1823, a German competition was held to perfect the production process: the goal was to develop an alloy that possessed the closest visual similarity to silver. The brothers Henniger in Berlin and Ernst August Geitner in Schneeberg independently achieved this goal. The manufacturer Berndorf (founded in 1843) named the trademark brand Alpacca, which became widely known in northern Europe for nickel silver. In 1830, the German process of manufacture was introduced into England, while exports of paktong from China gradually stopped. In 1832, a form of German silver was also developed in Birmingham, England.

The industrial production of copper-zinc-nickel alloys was initiated in 1823 by a competition organized by the Association for the Promotion of Industrial Diligence in Prussia. The challenge was to produce a white alloy that would resemble 750/1000 (fine) silver and would also be suitable for dining utensils. It should also cost only 1/6 of the price of silver at the time. Ernst August Geitner, who came from the Kingdom of Saxony, solved this problem. He developed the Argentan alloy in 1823 in Auerhammer near Aue, but was unable to receive the prize because he was not a Prussian citizen. The Henniger brothers in Berlin, who had succeeded in producing a nickel silver alloy similar to Argentan in 1824, purchased nickel from Geitner for their cutlery. This replaced the arsenic-containing white copper previously used.

After the modern process for the production of electroplated nickel silver was patented in 1840 by George Richards Elkington and his cousin Henry Elkington in Birmingham, the development of electroplating caused nickel silver to become widely used. It formed an ideal, strong and bright substrate for the plating process. It was also used unplated in applications such as cutlery.

Characteristics

Nickel silver is a silvery-white to yellow-colored alloy made of 47–64% copper, 10–25% nickel, and 15–42% zinc, possibly with admixtures of elements such as lead, tin, manganese, or iron. It is distinguished from copper by its greater hardness and corrosion resistance due to its nickel content. The official identification mark is the weight number stamp.

Melting point: from approx. 900 °C, increasing depending on the alloy

Density: 8.1 to 8.7 g cm −3 (depending on the mixture)

Electrical conductivity: approx. 3•10 6 to 5•10 6 Ω −1 •m −1

Thermal conductivity: approx. 25 to 35 W•m −1 •K −1

Coefficient of thermal expansion: 16•10 −6 to 17•10 −6 K −1

Like many copper alloys (wrought alloys), nickel silver can be hardened by cold forming (surface hardening), for example, by forging, rolling, or drawing. Heating (annealing) above approximately 500 °C creates new metal grains (recrystallization), and the material becomes soft again.

Chemical composition

The overall Ni and Zn contents must be less than 36% by mass to obtain a homogeneous alloy, otherwise the alloy is a solid solution:

either single-phase (cold malleable, easily transformed by rolling, stamping or embossing);

either two-phase (even poorer in copper, but even more easily machinable, and especially hot spinning, die-stamping, etc.).

The respective proportions are for Cu 45% to 65%, Ni 5% to 25% and Zn 20% to 45%.

Some common alloys are: Cu 63 Zn 28 Ni 9, Cu 55 Zn 27 Ni 18, Cu 46 Zn 45 Ni 9, Cu 57 Zn 17 Ni 26.

Nickel silver could or still may contain very small amounts of lead, tin or iron. Note the lead alloy, the main two-phase nickel silver Cu 46 Zn 10 Ni 42 Pb 2.

Mass proportions of the alloy: Cu 45 to 65%, Ni 10 to 25% and Zn 20 to 27%.

If the proportion of Cu exceeds 65%, the alloy takes on a golden color; the term nickel silver then becomes abusive and it is preferable to use the term nickel brass. For example, the crown of the 1 euro coins and the center of the 2 euro coins have a composition of Cu 75 Zn 20 Ni 5.

Technical characteristics

This white, hard, slightly oxidizable alloy with low electrical conductivity, generally characterized by colors, generally has good machinability and weldability, it is especially excellent for cold working.

It is generally harder than silver while being slightly more elastic. Silver material has a better resonance, however, to ensure the flute notes, but the less expensive nickel silver is suitable.

Range of properties:

density: 8,600 kg m −3 to more than 8,750 kg m −3 (density: 8.6 to 8.8);

melting point: 980 to 1110 °C;

Vickers hardness: 75-190;

resistivity: 2.5 to 3.1 × 10 −7 Ω m.

A nickel silver coin (at least in alloys with less than 25% nickel) is not lifted by an ordinary magnet.

The alloy of the 10 and 25 centime nickel silver coins from 1939 is close to Cu 63 Zn 28 Ni 9.

Uses

Nickel silver first became popular as a base metal for silver-plated cutlery and other silverware, notably the electroplated wares called EPNS (electroplated nickel silver). It is used in zippers, costume jewelry, for making musical instruments (e.g., flutes, clarinets), and is preferred for the track in electric model railway layouts, as its oxide is conductive. Better quality keys and lock cylinder pins are made of nickel silver for durability under heavy use. The alloy has been widely used in the production of coins (e.g. Portuguese escudo and the former GDR marks). Its industrial and technical uses include marine fittings and plumbing fixtures for its corrosion resistance, and heating coils for its high electrical resistance.

After Alfred Krupp patented the spoon roller in 1838, nickel silver was used for the industrial production of cutlery. Even today it is the basic material for silver-plated cutlery. It is used for precision mechanical and electrical devices, medical equipment, zippers, jewelry, snaffle bits, parts of wind instruments and eyeglasses, and as a material for frets on stringed instruments. The track profiles of model railways, precision mechanical springs and connectors in electrical engineering are sometimes made of nickel silver because the oxide is electrically conductive. Nickel silver is a common material for the crossguard of cutting and stabbing weapons and for the front sight of firearms because the color of the metal offers a good contrast to black. Nickel silver was initially used for test coins around 1900. A well-known early nickel silver coin is the 1 trillion-mark coin of the province of Westphalia from 1923. Numerous commemorative coins of the GDR were made of nickel silver. A more recent nickel silver alloy that is also used for coins is Virenium.

Keys, especially those for high-quality locking cylinders and locking systems, are also often made of nickel silver due to their low wear resistance. Some manufacturers also make the cylinder core in nickel silver (referred to as a "low-wear core").

These materials are of particular interest to electrical engineering and electronics due to their strength and toughness, sufficient electrical conductivity, their considerable modulus of elasticity compared to other copper materials, their better tarnish resistance, and their corrosion resistance. This combination of properties is particularly advantageous for electrical contacts and springs.

In practice, nickel silver solder is often used to describe a hard solder consisting of approximately 50% copper, 10% nickel, 40% zinc, and approximately 0.2% each of silicon, manganese, and tin. The melting range is 890–920 °C.

In the nineteenth century, particularly after 1868, North American Plains Indian metalsmiths were able to easily acquire sheets of German silver. They used them to cut, stamp, and cold hammer a wide range of accessories and also horse gear. Presently, Plains metalsmiths use German silver for pendants, pectorals, bracelets, armbands, hair plates, conchas (oval decorative plates for belts), earrings, belt buckles, necktie slides, stickpins, dush-tuhs, and tiaras. Nickel silver is the metal of choice among contemporary Kiowa and Pawnee in Oklahoma. Many of the metal fittings on modern higher-end equine harness and tack are of nickel silver.

Early in the twentieth century, German silver was used by automobile manufacturers before the advent of steel sheet metal. For example, the famous Rolls-Royce Silver Ghost of 1907 used German silver. After about 1920, it became widely used for pocketknife bolsters, due to its machinability and corrosion resistance. Prior to this, the most common metal was iron.

Musical instruments, including the flute, saxophone, trumpet, and French horn, string instrument frets, and electric guitar pickup parts, can be made of nickel silver. Many professional-level French horns are entirely made of nickel silver. Some saxophone manufacturers, such as Keilwerth, offer saxophones made of nickel silver (Shadow model); these are far rarer than traditional lacquered brass saxophones. Student-level flutes and piccolos are also made of silver-plated nickel silver, although upper-level models are likely to use sterling silver. Nickel silver produces a bright and powerful sound quality; an additional benefit is that the metal is harder and more corrosion resistant than brass. Because of its hardness, it is used for most clarinet, flute, oboe and similar wind instrument keys, normally silver-plated. It is used to produce the tubes (called staples) onto which oboe reeds are tied.

Many parts of brass instruments are made of nickel silver, such as tubes, braces or valve mechanism. Trombone slides of many manufacturers offer a lightweight nickel silver (LT slide) option for faster slide action and weight balance. The material was used in the construction of the National tricone resophonic guitar. The frets of guitar, mandolin, banjo, bass, and related string instruments are typically nickel silver. Nickel silver is sometimes used as ornamentation on the great highland bagpipe.

Nickel silver is also used in artworks. The Dutch sculptor Willem Lenssinck has made several pieces from German silver. Outdoors art made from this material easily withstands all kinds of weather.

Jewelry

In Europe, there has been a ban on the use of nickel and its derivatives in jewellery that is in direct, prolonged contact with the skin since 1994. 

Numismatics: coins and medals

It was used in Austria for the minting of 10 haller coins in 1915 and 1916. In France, trial coins were found from 1856 and it was used for circulating coins, for the first time in 1903 for the 50 centime and 1 franc Guadeloupe and dependencies coins, then, from 1938 to 1940 for the minting of the 5, 10 and 25 centime "holes" Lindauer type coins, as well as certain emergency coins. In Belgium, the 5, 10 and 25 centime coins between 1930 and 1939 were also made of nickel silver.

The current Mexican bimetallic 10 peso coin has its center made of this metal, with the outer ring made of aluminum bronze.

There are also many medals made of nickel silver.

Virenium is a nickel silver-type alloy developed from the late 1970s onwards.

Nickel silver has a specific electromagnetic signature and density that allows electronic parts analyzers to easily distinguish it from other part materials (12% Ni or 18% Ni nickel silver).

Automotive industry

The famous horseshoe-shaped grilles of old Bugattis are made of polished nickel silver.

In the early 20th century, nickel silver was used by car manufacturers before the advent of sheet steel. For example, the famous 1907 Silver Ghost from Rolls-Royce Limited.

In the 1920s, Carrozzeria Viotti & Tolfo in Italy used nickel silver for car chassis. The solution, called " Clairalpax," replaced the solid wooden door jambs with thin nickel silver ones, which provided the passenger compartment with greater brightness thanks to the increased glass area.

Electrical industry

Nickel silver is particularly attractive in electrical engineering and electronics due to its strength and resistance to wear, its sufficient electrical conductivity, its remarkable modulus of elasticity compared to other copper-based materials, its better resistance to tarnishing and its resistance to corrosion. This combination of properties is particularly advantageous for electrical contacts and springs.

Welding

In practice, nickel silver solder is often referred to as a hard solder composed of about 50% copper, 10% nickel, 40% zinc, and about 0.2% silicon, manganese, and tin respectively. The melting range is 890–920 °C.

Keys

In locksmithing, the best quality keys and lock cylinder pins are generally made of nickel silver for its mechanical properties allowing precise work and good resistance to use.

Goldsmithing

Patented in 1838 by Alfred Krupp under the name Neusilber for the industrial production of cutlery, it is still the basic material for silver-plated cutlery today. The manufacture of silver-plated cutlery uses it as a basic support, with the nickel silver core being visible when the plating silver is worn and worn away, as oxidation to toxic verdigris becomes apparent. According to the Merck Manual of Diagnosis and Therapeutics, prolonged contact of copper alloys with acidic food or drink (including boiling milk) can leach copper and cause toxicity.

Model making

It is used in particular to make model train tracks, because it oxidizes less easily than tinned (tinplate) or zinc-plated steel. Despite lower electrical conductivity, it reduces sparking on contact with the wheels, linked to contact resistivity (it depends on surface oxidation).

In thin plate, it allows the production of highly precise parts by chemical etching then welded assembly in several layers to create complex three-dimensional shapes.

Instrumental invoice

In musical instrument manufacturing, it is used for the manufacture of parts subject to high stress and whose lifespan is extended by their reduced wear. Musical instruments, including the flute, saxophone, trumpet and French horn, the frets of string instruments and the pickup parts of electric guitars, may be made from nickel silver. Student-level transverse flutes and piccolos are also made from silver-plated nickel silver, although higher-level models are frequently made from solid sterling silver. Even when the body is silver, it is rare for the keywork not to be nickel silver.

Many professional-level French horns are made entirely of nickel silver. Some saxophone makers, such as Keilwerth , offer nickel silver saxophones (Shadow model); these are much rarer than traditional lacquered brass saxophones. Nickel silver produces a bright, powerful sound quality; an additional advantage is that the metal is harder and more corrosion-resistant than brass. Because of its hardness, it is used for most clarinet, flute, oboe, and similar woodwind instrument keys, usually nickel-plated for student models and silver-plated for high-end models. It is used to make certain tubes (Chiarugi, Pisoni brands...) to which oboe reeds are attached.

Many parts of brass instruments are made of nickel silver, such as tubes, reinforcements, and valve mechanisms. Many manufacturers' trombone slides and slide cases offer a lightweight nickel silver (LT slide) option for faster slide action and weight balance.

This metal was also used extensively from 1835 in the manufacture of bows. The material was used in the construction of the National String Instrument Corporation 's tricone resonator guitar. The frets of the guitar, mandolin, banjo, bass, and related string instruments are commonly made of nickel silver. Nickel silver is sometimes used as an ornament on the Scottish bagpipe.

Due to their properties, nickel and its derivatives such as nickel silver are used in the manufacture of instruments which are not currently included in the scope of REACH regulations in France and Europe; this applicable text does not only concern the placing of objects on the market, but also the manufacture of these objects on European soil.

Arms industry

This alloy is used to make all or part of the small arms projectiles for the Dutch Mannlicher or Mauser 98.

Equestrian equipment

Many metal accessories in modern high-end harnesses and equestrian equipment are made of nickel silver.

Works of art

Nickel silver is also used in artwork. Dutch sculptor Willem Lenssinck created several works from nickel silver. Outdoor artwork made from this material easily withstands all weather conditions.

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