In our last two posts, we looked at soldering and welding. Today we look at the other well-known method for metal joining: brazing.
What is Brazing?
Returning again to wiseGEEK.com, this time their article What Is Brazing?, we find that, like the word “solder,” the word “braze” is both a noun and a verb. wiseGEEK describes the verb as “a process that joins two pieces of base metal when a melted metallic filler — the braze— flows across the joint and cools to form a solid bond.” In their description of the verb, we can see that noun form of braze is as a “metallic filler.”
What is the Difference?
As with soldering, we learned that the components to be joined stay intact while a filler is melted between them, whereas with welding, the components themselves are melted together as part of the process. As Chris Woodford, over at ExplainThatStuff.com, explains in his article on welding and soldering, brazing works more like an adhesive where the filler actually seeps into the surface of the components being joined. With soldering, the filler really only sits on the surface of the joined components. Woodford likens brazing to a hybrid between soldering and welding, with a primary goal of a structural joint, with conductance as a by-product.
With respect to the difference between the filler materials themselves, We turn to the Copper Development Association’s article explaining soldering and brazing. As we learned in our post on soldering, solder was tradtionaly composed primarily of lead, usually mixed with tin. Now, it is primarily composed of tin mixed with nickel, bismuth, antimony, silver and/or copper.
Braze is divided into two categories. One, BCuP, is primarily composed of copper and phosphorus, with up to 30% silver. The other, BAg, contains between 24% and 93% silver. Both types have a significantly higher melting point than solder. Materials with a melting point below 450ºC is considered to be solder, while materials above that mark are used in brazing.