Copper Brazing Alloys

Brazing alloys based on copper, basically of copper and zinc with melting ranges of 866° C to 1082°C are used to braze ferrous alloy components. Pure copper can wets such components under carefully controlled brazing conditions. The presence of zinc in copper alloys facilitates wetting and also decreases the brazing temperature.

Copper-Phosphorous Brazing Alloys
In all the copper brazing alloys, copper-phosphorus alloys have spectacular brazing properties and defining capabilities. Phosphorus readily alloys with copper. Phosphorus acts as a reducing agent for copper and also de-oxidizes silver. The brazing alloys of copper-phosphorus and silver-copper-phosphorus are self-fluxing on pure copper.

The additions of silver and reduction of phosphorus have a sound effect on the fluidity of brazing alloys. Alloys with greater phosphorus content are extremely fluid, while the alloys with lower phosphorus and high silver alloy has a wide plastic range. Even slight differences in alloy composition have a pronounced effect on brazing alloy fluidity.

Copper-phosphorus brazing alloys having the liquidus temperatures range of 718°C to 924°C are also widely used. Apart from improving wetting characteristics and lowering the brazing temperature , the phosphorous adds a self-fluxing characteristic to the alloys under oxidizing conditions. But due to the deleterious effect of phosphorus on ferrous alloys, these alloys are restricted in use for the brazing of non-ferrous components and stainless steels.

Copper
Copper is an important metal having atomic number 29 and symbol Cu. Its electrical conductivity is second only to silver. It is highly ductile and malleable metal with good thermal conductivity. Copper is extensively used as electrical conductor, heat conductor, building material, and as a component of a number of alloys.

Physical Properties
Density	8.96 g-cm-3
Liquid Density (at mp.)	8.02 g-cm-3
Melting Point	1357.77 K
Boiling Point	2835 K
Heat of Vaporization	300.4 KJ-mol-1
Heat of Fusion	13.26 KJ-mol-1

Chemical Properties
Oxidation States	2, 1
Atomic Radius	135 pm
Atomic Weight	63.54
Electro-negativity	1.90 (Pauling scale)
Ionization Energies	1st: 745.5 KJ-mol-1 2nd: 1957.9 KJ-mol-1 3rd: 3666 KJ-mol-1

Copper Alloys

• Beryllium Copper
  It is also known as copper beryllium or beryllium bronze. It is an alloy of copper and 0.5 to 3% beryllium and sometimes with other alloying elements.
  
  
• Billon
  This alloy contains copper as the majority base metal content and a precious metal (most commonly silver, but also gold). It is used mainly for making coins, medals.
  
  
• Brass
  Brass is a very important and popular alloy of copper. It is made up of copper and zinc. The proportions of copper and zinc vary to create a range of brasses.
  
  
• Bronze
  It is any of a wide range of copper alloys. Tin is the main additive but sometimes other elements like phosphorus, manganese, aluminum, silicon are also used.
  
  
• Constantan
  It is a copper-nickel alloy usually made of 40% Nickel and 60% Copper. Its resistance is extremely good and remain constant over a wide range of temperatures.
  
  
• Manganin
  This is a trademarked name for an alloy, which is typically constituted of 86% copper, 12% manganese, and 2% nickel.