The only thing I've not done yet that someone has mentione to me is
adding an inert gas such as argon. Is this the magic solution?
Any help would greatly be appreciated.
Kevin, I think I mentioned when this first came up, that of all the
adjustments one can make to welding paramaters, the one which makes
the MOST difference in welding nickle white golds, is the use of
argon. With yellow golds the welds come out brighter, but not all
that much cleaner, so it’s used only when the shiney weld will have
cosmetic advantages. But the main reason we have that costly argon
setup is for white golds. The vendor we bought the laser from was
sufficiently convinced of this as well, that they sent us the
special regulator and fittings for free, some time after we’d bought
the laser… By the way, you may wish to purchase the regulator for
the argon from the laser manufacturer. When I bought one, I found the
regulators available from the local welding supply house tend to be
higher flow rates, as used with inert gas sheilded arc welding (MIG,
TIG, plasma, etc). The laser is best with fairly low flow rates. I
modified my own regulator once I realized that the welding supply
one I’d spent a bunch of money on wasn’t quite right, but it would
have been better to get it directly from the laser dealers…
Note that argon still won’t always solve ALL problems. sometimes
you’ll still get some pitting, especially if you’re welding on
castings that are too porous in the first place. It’s one thing,
after all, to ask the laser to not add porosity. it’s something else
entirely to weld on a piece of spongy crappy metal and expect the
laser to leave you with no remaining pits when you’re done. Also,
sometimes it helps a lot to weld your piece, then clean up the weld
(sand or rubber wheel it, to the point where it would be ready to
polish, or even prepolish the thing) . Then go back to the laser and
at very low power, just enough to leave a light melt spot that’s
still fairly smooth and bright, usually with a short duration pulse
but a more rapid pulse rate, “planish” the surface going over
questionable spots repeatedly until pits quit showing up… This can
fix any remaining surface pits if the metal is reasonably good in
the first place. In our shop it’s kinda automatic. We goldsmiths do
the work, and send things on to our polisher, who’s a rather picky
gent. When he finds pits in welds or castings, he marks em with red
marker and puts them back on our benches to touch up. A little
"planishing" on those spots, and it’s back to the polisher who
usually then is satisfied. In the very worst cases, usually really
bad castings, I sometimes have to mechanically burnish the welded
areas before giving them back to the polisher, but usually the
laser, with argon, will do it.
If your laser supports pulse shaping, then a longer pulse that ramps
up, and especially ramps down again more slowly, will reduce the
hardening and tendancy to crack that white golds also suffer from.
The argon doesn’t help with weld cracking much, it just gives you
cleaner looking welds with considerably less pitting. Often, even
with the pulse shaping, I find it advantageous to torch anneal the
weld after welding, if the work is something that can stand the heat
of a gentle anneal or stress relieving process. The welds are then
much less likely to crack or fail later, with a strength that then
pretty much matches the parent metal.
Hope that helps.
Peter