Jeff Wisnia wrote:


I've done that many times. (If you asked SWMBO she would say of me, "Can
you spell c-h-e-a-p?")

On several occasions I found it extremely difficult to get the joints
apart, after they were heated to well above the melting point of soft
solder. Twisting a fitting while pulling on it to try and get it to come
off would produce a squeek like the door hinges from "Inner Sanctum".

I asked metallurgist about that and he told me it was due to the
formation of intermetallic compounds over time, which had a higher
melting point than solder.


Yep.

There's another similar phenomenon that's quite interesting, but perhaps not
directly relevant, diffusion brazing.

You braze a joint and keep it hot for an hour or do. Note that braze metal
necessarily has a lower melting point than the base metal, otherwise it
would ebe welding. The lower-melting metals in the braze diffuse into the
base metal, and eventually the melting point of the metal where the brazed
joint was is as high as the original base metal (it can actually even be
higher).


And the same Cu3Sn (or Sn3Cu, I'm too drunk to remember) molecules (*shhh..)
(though they are a problem in diffusion brazing - come to think of it, they
are also a problem in disassembling plumbing fittings - darn those Cu3Sn
molecules!) are often involved, to bring it right back on topic!


--
Peter Fairbrother

Love is old, love is new
Love is all, love is you

Ahhhh

Because ...



*yes i know they aren't.