Copper Brazing

Copper and its alloys are used in a wide variety of applications due to their properties. The family of copper and their alloys have excellent corrosion resistance and formability. Brazing is the most suitable metal joining process for all types of copper alloys but with a little bit of precaution. If proper precautions aren't taken during brazing then it may lead to cracking, distortion, and unacceptable softening. They have higher thermal expansion than steels, and it plays an important role when brazing dissimilar metals.



Base Metals

Copper and Its Alloys	Suggested Brazing Filler Metals	Description
Oxygen Bearing Coppers	Copper Brazing Alloys(Alloyed with Phosphorous and/or Silver)	It includes the fire-refined and electrolytic tough pitch grades of copper and silver bearing copper.
De-oxidized and Oxygen-Free Coppers	Copper Brazing Alloys(Alloyed with Phosphorous and/or Silver)	It includes phosphorus deoxidized copper, which is free from oxygen. Oxygen free copper has an oxygen content that is deliberately minimized.
Special Coppers	Copper Brazing Alloys(Alloyed with Phosphorous and/or Silver)	It includes some alloys, which provide high electrical conductivity along with special properties like machinability.
High Coppers	Silver Brazing Alloys(with varying amounts of Cu-Zn-Cd)	It includes the copper with additional amounts of alloying elements that enhance mechanical properties.
Copper-Zinc Alloys(Brasses)	Silver Brazing Alloys and Copper Brazing Alloys	They are produced with varying ratios of these two elements to provide desired properties and casting characteristics.
Copper-Tin Alloys(Phosphor Bronzes)	Silver Brazing Alloys(Cu-Zn-Cd) Copper Brazing Alloys(Ag-P)	The amount of tin may vary from 1% to 10% in different alloys.
Copper-Aluminum Alloys(Aluminum Bronzes)	Silver Brazing Alloys(Cu-Zn-Cd)	They are high copper alloys that contain 3 to 13 % aluminum and varying amounts of iron, nickel, manganese, and silicon.
Copper-Silicon Alloys(Silicon Bronzes)	Silver Brazing Alloys(Cu-Zn-Cd)	These alloys include 1.5 to 3.5 % silicon and 1.25% or less of zinc, tin, manganese or iron.
Copper-Nickel Alloys	Silver Brazing Alloys(Cu-Zn-Cd) Copper Brazing Alloys(Ag-P)	The nickel content ranges from 5 to 30%. Some other elements are also added, such as iron, manganese or chromium.
Copper-Nickel-Zinc Alloys(Nickel Silvers)	Silver Brazing Alloys(Cu-Zn-Cd) Copper Brazing Alloys(Ag-P)	Nickel is added to make them silvery in appearance and to enhance strength and corrosion resistance.

Brazing Filler Metals
The most commonly used filler metals for brazing copper and its alloys:

• Silver Brazing Filler Metals
  Silver brazing alloys are the most used filler metals for brazing copper and its alloys. The percentage of silver, copper, zinc, and cadmium vary in different products). Their brazing temperatures should lie in the range from 1145° F to 1600° F (620° to 870°C).
  
  
• Copper Brazing Filler Metals
  Copper brazing alloys are also widely used for brazing copper and their alloys. The primary constituents are zinc, phosphorous, silver, etc.
  • Copper brazing alloys with zinc as the second most major constituent are suitable for brazing coppers, copper-nickel, copper-silicon, and copper-tin alloys. Their liquidus temperature are very high and aren't suitable for brazing the brasses and nickel silvers. They aren't suitable for brazing aluminum bronzes.
    
    
  • Copper brazing alloys having phosphorous and silver as the other two main constituents are useful for most of the copper base metals because fluxes are not required.

Atmospheres
Combustion fuel gases are useful and economical atmospheres for brazing most copper base alloys. Dissociated ammonia and hydrogen are also useful, except for oxygen-bearing coppers. Inert-gas atmospheres, such as argon and helium, and also nitrogen may be used for all copper base alloys without harmful effects. Vacuum atmosphere is suitable for copper and copper alloys when the alloys are essentially free of elements having high vapor pressure at the brazing temperature.

Safety
Some brazing filler alloys contain cadmium and zinc, some base metals contain lead, zinc or beryllium, while some fluxes contain fluorides. When such material are used, proper ventilation must be provided to protect the personnel.