Soldering? Brazing? Welding? What?

Published at 21:27 on 4 February 2014

Just to confuse neophytes, different trades use different words for the same process as well as the same word for different processes.

Soldering as the electronics and plumbing fields calls it is using a metal that melts at under 500 °F and which is relatively thick and capable of filling gaps when it melts, but which bonds relatively weakly with the metals being joined.

Soldering as the jewelry field calls it uses a metal that melts at over 1,000 °F and which is thin, runny, and not capable of filling large gaps when it melts, but which bonds very strongly with the metals being joined. Provided you can have the necessary tight fit, it can make a bond as strong as a weld.

Brazing as the plumbing field calls it is the same thing as what jewelers call soldering.

Brazing as welders call it is using brass or bronze to join parent metals which are typically not brass or bronze and which melt at higher melting points than brass or bronze. It has the advantages of both brazing (as plumbers call it) and soldering (as plumbers and electricians call it): it both bonds very strongly and is good at filling gaps. The disadvantage is that it doesn’t melt easily; you need an oxy/acetylene torch to do brazing in the welder’s sense.

Welding is melting the two pieces of similar parent metal together, and often adding additional similar metal as filler. It makes a joint almost indistinguishable from the parent metal, is every bit as strong as the parent metal, and fills gaps well. But it takes the most heat of all, either an oxy/acetylene flame or an electric arc.

This all confused me to no end for a long time. I wondered how jewelers could get away with hammering on soldered butt joints; I had soldered things many times in working with electronics and knew soldered joints were nowhere near strong enough to stand such treatment. And what was the deal with those “brazing rods” for sale near the propane torches? I knew a mere propane torch couldn’t braze; you needed oxy/acetylene for that!

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