For me, the key difference is how they work on the joint.
Silver Solder is more fluid than Braze and works by being drawn into the joint by a capillary action. So if, for example, you want to join two pieces of thin sheet metal together, you would need to overlap them. The Silver Solder will be drawn through the joint, filling the minute crack between the two pieces of metal, bonding with the surfaces to join them. If you tried to butt the two pieces of metal together, there simply wouldn’t be enough surface area touching to achieve a strong joint.
Silver Solder is used with a Flux, which chemically cleans the metal and keeps it clean during the Silver Soldering process. Silver Solder is also know as Silver Brazing.
Braze on the other hand, does not get drawn into the joint, but is built up on the surface of the metal being joined, so it looks more like a weld. Like Silver Solder, the Braze material bonds with the surface of the metal being joined.
Braze is used with a Flux, which chemically cleans the metal and keeps it clean during the Brazing process. Brazing is also known as Bronze Welding.
What Silver Solder & Braze have in common is that neither involve melting the metal that’s being joined, that would be welding!
In the joint examples shown, I would use Silver Solder on the Edge & Lap Joint and Braze for the Butt, Corner & Tee Joint.
Whilst there are a number of Brazing Alloys on the market, for this article we’ll keep it simple and just cover the most common, C2.
C2 is a multi purpose, Silicon Bronze brazing rod that’s suited to most general purpose brazing on metals including Steel, Copper, Cast Iron and dissimilar metals.
C2 Braze is Brass Coloured and typically melts at around 875⁰C.
Most Silver Solders can be categorised by their Silver content. The Silver content will determine the fluidity and melting temperature, the more Silver, the more fluid and the lower the melting temperature.
Most common are 33% Silver (around 720⁰C), 40% Silver (around 675⁰C) and 55% Silver (around 650⁰C).
Also available are Silver bearing Copper Phosphorus Alloys (CoPhos). These are available with either 2% or 5% Silver and are used primarily for joining Copper to Copper, where, if the metal is clean, no Flux need be used.
Silver Solder can be used to join most common metals, including Mild Steel, Stainless Steel, Copper, Brass, Cast Iron and Dissimilar Metals.
Silver Solder & Braze is usually available in 2 or 3 forms:
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