Silver Brazing Alloys

Silver based brazing alloys are mainly used for bonding the most ferrous and nonferrous metals except magnesium and aluminum. A large number of silver based brazing alloys are used for different industrial uses. These include various additions, such as Cu, Li, Zn, Mg, Ni, Cd. The addition of zinc in the Ag-Cu alloy decreases the melting temperature and helps wet iron, cobalt, and nickel. Cadmium is also very good in lowering the brazing temperature and helps in wetting different metals. Zinc and cadmium vaporises during the brazing.

Silver filler alloys melt at lower temperatures than most bronze or brass fillers. The alloys having greater percentage of silver melts at lower temperature and can produce stronger joints. These materials are used for different brazing processes, such as resistance brazing, gas flame brazing, high frequency induction brazing and furnace brazing.


Silver
Silver is a white, soft, and lustrous metal having highest electrical and thermal conductivity for the metals. Its atomic number is 47 and the symbol is Ag. It is a precious metal and used in ornaments, currency, jewelery, utensils, etc.

Physical Properties
Appearance	Solid, White,Lustrous, Soft
Heat of Fusion	11.28 KJ/mol
Heat of Vaporization	250.58 KJ/mol
Heat Capacity	25.350 J/mol/K (at 25°C)
Melting point	962 °C

Chemical Properties
Atomic number	47
Atomic mass	107.87 g.mol -1
Electro-negativity	1.9 ( Pauling Scale)
Oxidation States	1
Ionization Energies	1st: 731.0 KJ/mol 2nd: 2070 KJ/mol 3rd: 3361 KJ/mol

Types	Constituents	Applications
Cadmium Bearing Silver Brazing Alloys	Silver, Copper, Zinc, Cadmium, Nickel	Used where joint clearances are large and fillets are desired, and for economical joints.
Cadmium Free Silver Brazing Alloys	Silver, Copper, Zinc, Manganese, Nickel, Tin	Brazing of Silverware, Vacuum tube seals, ferrous and non-Ferrous alloy without Flux, Ships piping, Band Instruments, Aircraft Engine, Oil Coolers, Brass Lamps.
Phosphorous Silver Brazing Alloys	Silver, Phosphorous, Copper	Used for copper, and brass brazing.

Features

• Silver based brazing alloys perform efficiently with middle-range melting point. They show high strength, good ductility and conductivity.
  
  
• Primary alloys elements in silver fillers include copper, zinc, cadmium,tin, and Ni.
  
  
• Brazing alloys having low melting points have usually good "wettabilty", high strength, toughness and silver brazing alloys have all these characteristics.

Forms of Silver Brazing Alloys
Silver filler materials usually come in the form of wires. The wires are of different shapes and sizes:

• Coils
• Bars
• Rods
• Flat
• Ring

Alloys of Silver

• Sterling Silver
  Sterling silver is an important alloy of silver constituting of 92.5% pure silver and 7.5% other metals mainly copper.
  
  
• Britannia Silver
  Britannia silver is an alloy of silver containing 95.84% silver, with the balance mainly copper.
  
  
• Goloid
  It is an alloy of silver, gold and copper patented by Dr. William Wheeler Hubbell. It contain 1 part gold (about 3.6%), 24 parts silver (about 87.3%), and 2.5 parts copper (about 9.1%, all by weight).
  
  
• Electrum
  It is a naturally occurring alloy of gold and silver having traces of copper and other metals.