[DMCForum] One more thing...
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[DMCForum] One more thing...




...The guy was talking about soldering aluminum, not welding it.
Welding by definition is the melting and fusion of the base
materials. This doesn't happen with soldering or brazing.

Aluminum can easily be soldered or even brazed with the proper flux
and technique. Don't use normal solder though, there are special
alloys made just for A/C repairs. Search on the net to find them or
ask at www.aircondition.com. I answer questions over there as I'm
also a licensed automotive A/C tech, among other things. However, I'd
take the other guy's advice and let an experienced A/C shop do it.

Aluminum doesn't oxidize when welding, it develops an oxide layer in
contact with the air. This "alumina" layer melts at a very high temp
and is why you need to remove it with AC current or other means. Try
puttin an arc on a thin piece of AL with normal (electrode negative)
DC GTAW current, it'll just shrug off the arc. Using electrode
positive will break up the oxides but very little heat is tranfered
to the work and the tungten will melt. It's why you need a larger
diameter tungsten when GTAW welding with AC or to weld aluminum or
magnesium. It's also why the tungsten "balls" when welding with A/C.
It has to do with the physics of the arc, I won't bore you with the
details unless you really want to know.

It's also why you can't cut aluminum well with a torch. A cutting
torch doesn't simply "burn" ferrous metals like steel, it oxidizes
them. Since AL contains no iron it can't be oxidized at the temps a
torch develops. A plasma cutter is a much better way to deal with non
ferrous metals. Fwiw, welding is much more science (and art) than
people think. It's far more involved than simply making sparks and
melting stuff.



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