HISTORY OF BRAZING
With millions of joints being produced daily, the use of silver solder for brazing is firmly established throughout the metals industries world wide as a simple, safe, reliable method of joining metal components. It has earned this position over thousands of years spreading from its earliest days in Asia to span all five continents today.
The earliest recorded examples of brazed joints were made around 3000 BC in Sumaria. They have survived the ravages of time because they were made predominantly using gold and silver alloys to produce the intricate jewellery for the Pharoahs that is still admired today.
For thousands of years this was the major application for brazing and remained the case through the Greek and Roman empires. Four thousand years later in China and India joints made from base metal were found. The East had found zinc and mixed it with copper to produce the first base metal brazing alloys.
Brass was created but it took until the mid sixteenth century and thanks to Dutch traders, before it became an economic, viable material in Europe.
Perhaps the word braze was originally derived from "brass" meaning - a means of joining two metals.
Silver was added and the alloys favoured by industry changed and lead to the range of silver solder used today.
Why use silver solder?
Intrinsically brazing alloys and silver solders are among the most expensive filler metal. Their use must be balanced with other technical, engineering and commercial reasons.
A silver solder is capable of joining a wide range of dissimilar metals, ferrous and nonferrous.
The joints are strong, leak tight and capable of withstanding a wide range of service conditions.
The low melting points associated with the process mean that joints can be made using less energy with minimum metallurgical degradation and minimum distortion - producing joints invariably stronger than the parent materials.
The presence of silver can offer enhanced corrosion resistance over other joining techniques.
But what is brazing?
Brazing is akin to the soldering process but merely carried out at higher temperatures. The principles are the same. It has been defined as "a metal joining process whereby molten alloy is drawn into a controlled gap between two components by capillary attraction." which upon solidification produces a sound joint.
The mention of capillary attraction sets brazing and soldering apart from all other metal joining processes. Achieving it will produce joints of the highest integrity and strengths higher than that of the parent materials. Unlike welding, the joint strength is not dependent upon the filler metal or the strength of the parent materials.