Brazing alloys, gold-based

The fluxes used with both silver and gold jewelry brazes are standard formulations, nsed also in industrial brazing. The most common fluxes used with gold brazing alloys are based on sodium tetraborate (Na2B407 IOH2O), commonly known as borax, which is fluid above 760°C, applied in the form of a paste. 

Lower melting point gold-based brazing alloys may be classified into two groups, according to the application. There are the karat gold brazes, which are mostly used in the jewelry trade, and others that were developed to address the needs of other application sectors, such as the electronics, nuclear power, and aerospace industries [29]. These types of gold-based brazes will be discussed in turn. 

Infrared brazing of TL NLn shape memory alloy using gold based brazing alloys, H. Shuie and S. K. Wu, Gold Bulletin, 2006, 39, 200-204. 

Gold is unusual in that it is the only element on which both brazes and solders are based. However, because gold is the most expensive constituent of solders and brazes, the use of gold filler alloys tends to be limited to high value applications, such as electronics, photonics, and jewelry manufacture. 

The different alloying elements nsed in gold solders and brazes have implications for recycling that need to be considered. Many base metals can cause embrittlement in gold alloys, even at low concentrations, and the treatment of scrap would have to recognize this problem and implement suitable solutions, analogous to the handling of aluminum scrap. 

The gold-bearing alloys designed for industrial use are superior to base-alloy brazes in the following respects ... 

A similar challenge was met in the United States with brazes having a much reduced gold content. These are quinary alloys that contain around 20 wt% gold and 65 wt% nickel, with the balance made up of chromium, irou, and silicon [40]. They melt in the fairly narrow range of 943-960 C and were developed for the assanbly of space shuttle eugines as alternatives to conventional nickel-based brazes and conferred with an enhanced ductility. 

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