Silver (Ag) is a transition metal with an atomic number 47.
The atomic mass of silver is 107.8682(2). The most abundant and stable isotopes of silver are 107Ag and 109Ag).
A nucleus of 107Ag is composed of 47 protons and 60 neutrons.
Silver is found in chemically uncombined state: as pure silver (native silver) or in form of a silver-gold alloy (electrum)).
Silver occurs also in a combined form as Ag2S (silver sulfide), AgCl (silver chloride), Ag3SbS3 (silver sulfantimonide).
The most prominent properties of silver:
Pure (fine) silver is very soft (26 HV in annealed state) therefore it is rarely used in an non-alloyed state.
The strength, modulus of elasticity and hardness of silver may be considerably increased by alloying with other metals.
The most popular jewelry/tableware silver alloy is alloyed with 7.5% of copper. The alloy is called Sterling silver.
Sterling silver has a hardness 71 HV in annealed state. The hardness may be increased to 140 HV by strain hardening (cold work).
Jewelry and tableware pieces made of sterling silver has good wear and scratch resistances. On the other hand the alloy is very malleable and ductile what makes it easy to fabricate.
Tarnish resistance of sterling silver may be improved by replacing of 0.5-1% of copper with germanium (Ge) (Argentium sterling silver).
Brazing is a method of joining two metal work pieces by means of a filler material at a temperature above its melting point but below the melting point of either of the materials being joined.
Flow of the molten filler material into the gap between the work pieces is driven by the capillary force. The filler material cools down and solidifies forming a strong metallurgical joint, which is usually stronger than the parent (work piece) materials. The parent materials are not fused in the process.
Silver alloys are popular filler material used for brazing Copper alloys, Nickel alloys, Stainless steels, Carbon steels and Alloy steels.
The melting point of general purpose silver brazing alloys is in the range 1200-1500ºF (649-816ºC).
Besides silver the alloys contain copper 20-50% of (Cu) and 10-40% of zinc (Zn). Some of the alloys may also contain 2-5% of tin (Sn) and/or 0.1-0.25% of silicon (Si) for better flowing ability and aesthetic appearance.
Gold and silver have been used as coinage metals for thousands years.
Content of silver in different coin silver alloys varies within 50-99.99%.
Other metals contained in silver coin alloys are copper and zinc.
One of the standard coin alloys is Britannia silver with the composition 95.84% silver and 4.16% copper. Britannia silver was introduced by English Parliament in 1697 as a replacement to sterling silver.
The modern Silver Britannia coins (since 2013) and American Silver Eagle (the official silver bullion coin) contain 99.90% silver.
Exceptional electrical and thermal conductivities combined with chemical stability make silver very useful for electrical applications.
Silver alloys are widely used in various break contacts, relays, switches, sliding and rolling contacts.
The alloys and pseudo alloys (Metal Matrix Composites) are prepared by casting and sintering technologies.
The most popular silver alloys for electrical applications:
|Argentium sterling silver||92.5||6.5||-||-||-||-||1||-|
|Ag10Cu electrical silver||90||10||-||-||-||-||-||-|
|Ag10Ni electrical silver||90||-||-||10||-||-||-||-|
|Ag5C electrical silver||95||-||-||-||-||-||-||5|
|Brazing alloy AG 202||60||26||14||-||-||-||-||-|
|Brazing alloy AG 102||56||22||17||-||5||-||-||-|
|Brazing alloy AG 206||20||40||39.9||-||-||0.1||-||-|