On Wed, 28 Apr 2004 01:49:15 -0500, "Tim Williams"
wrote:

"jim rozen" wrote in message
...
No doubt somebody will chime in here and claim I am full of it,
(probably am)

You're full of it, Jim. :-p
Really, it's spot on.

but I think that if it melts above about 900F then that is brazing
and below that it is soft soldering. Purely an arbitrary line drawn
in the (temperature) sand because the process is *exactly* the same:
joining two similar or dis-similar materials, using a third material
as a kind of inter-atomic 'glue.' The adhesion forces that make
solder of any kind stick to another material's surface are not really
well understood by physicists in general.

They say the temperature of brazing opens the crystal structure a little,
enough for a small amount of braze to wick in. It's certainly far, far
stronger than soldering with tin, lead or zinc. I haven't had silver solder
work right with steel so I'll lump it in with soft solder too. ;-P

Well, We broke a couple distributor drive gears on our old Renault R12
rally car years ago, and didn't have another one available when we
finally figured out what was breaking them, so I silver soldered one
back together. We rallied it for 3 years, and my brother used it for a
beater for 3 more. The soldered gear was still in one piece when the
body finally fell off and he scrapped it.
It was a (cast) steel gear.
I have however silver soldered brass and copper with the same strength (that
is, stronger than the base metal due to the added stiffness). But you can
also solder lead together with tin-based solder and it might as well be
welded. (No doubt as the metals are extremely compatible and likely the
solder dissolves into the lead, but that's beside the point...) As such I'd
like to say lead can be brazed, and this would bring about a new definition
of brazing where the base metal is strongly bonded to the filler,
temperature-wise it's probably a fraction of the melting point, with respect
to absolute zero no doubt. And also probably related to the expansion rate
of the metal.

There is considerable
discussion even now about the physical processes of "adhesion" in
some industries. Like mine.

I'm sure there is. Certainly a lot of quantum physics has the chance to
apply...

I found out how well lead can dissolve gold the hard way - by trying
to solder a 0.003 inch diameter gold wire with lead-tin solder.
Talk about frustration!

But hey, it makes gold-plated connectors easy as fudge to tin!

Tim (posting tired so don't be too hard on me