Nickel silver
Nickel silver is the term for a copper-nickel -zinc alloy with high corrosion resistance, strength and silver -like appearance. German silver is used in particular for tableware ( cutlery, cutlery service and body goods), fittings and jewelry.
For nickel silver, there are also the names alpaca / alpaca ( registered trademark ), Argentan, Minar Ghent, the French terms Cuivre blanc and Maillechort and derived from the Chinese name Packfong. Also the name of hotel silver is used. In Spanish, German silver is also known as plata alemana and in English as German Silver (both German silver). Galvanic silver-plated nickel silver is referred to as China silver.
Properties
Nickel silver is a silver -white shining alloy of 47-64 % copper, 10-25 % nickel, 15-42 % zinc, possibly with a mix of elements such as lead, tin, manganese or iron. It is distinguished from copper because of the nickel content by greater hardness and corrosion resistance. The official recognition character is the weight number stamp.
- Melting point: rising from about 900 ° C, depending on the alloy
- Density: 8.1 to 8.7 g · cm -3 ( depending on the mix )
- Electrical conductivity: about 3106-5106 Ω -1 · m -1
- Thermal conductivity: about 25 to 35 W · m -1 · K-1
- Coefficient of thermal expansion: 16:10 -6 to 17.10 -6 K-1
Like all copper alloys, nickel silver only be hardened by cold working ( surface hardening ), for example, by forging, rolling or drawing. A heating ( annealing) above about 500 ° C the crystal system assigns new, so that the material becomes soft again.
History
Already in the 17th century first metal goods came from a Packfong said alloy from the Empire of China to Europe. But it was only in the 18th century it was recognized that Packfong consisting of copper, zinc and nickel. In the metal works of Suhl succeeded already in 1770, to produce a similar Packfong the alloy. They soon became known as Suhler white copper. However, the Suhler White copper containing arsenic and was therefore toxic.
The industrial production of copper - zinc -nickel alloys was initiated in 1823 by a prize offered by the Society for the Promotion of trade diligence. It called for the production of a white alloy, which should be (fine) and the same for dining utensils suitable in appearance to the silver 750 /000. In addition, it should cost only 1/6 of the then price of silver. This solution provided almost the same time Dr. Ernst August Geitner, the alloy Argentan developed in Auernhammer at Aue in 1823, and in 1824 the brothers Henniger in Berlin with the similar alloy nickel silver. So that was previously used arsenic White copper to be replaced.
Use
According to the patent application, the spoon roll in 1838 by Alfred Krupp nickel silver was used for the industrial production of cutlery. Even today it is the base material for surface- silvered cutlery. It is used for fine mechanical and electrical equipment, medical equipment, zippers, jewelry, bridle bits, parts of wind instruments and eyeglasses as well as material for frets on stringed instruments. The rail profiles of model trains, precision mechanical springs and electrical connectors are made sometimes made of nickel silver, because the oxide is electrically conductive. When cutting and stabbing weapons nickel silver is a common material for the guard, for the grain of sight because the color of the metal provides a good contrast to black with firearms. Numerous commemorative coins of the GDR were made of nickel silver. Also key, especially those for high-quality lock cylinder and locking systems are often made because of the low wear of nickel silver. Some manufacturers lead the cylinder core in nickel silver from ( called " wear-resistant core ").
Neusilberlot as a brazing material is referred to, in practice, often consisting of approximately 50 % copper, 10% nickel, 40 % zinc and about 0.2 % each of silicon, manganese and tin. The melting range is 890-920 ° C.