Back to Ganoksin | FAQ | Contact

Laser Welding White Gold


#1

Hi All, I have a questions for Peter and the rest of you using laser
welders. I have had’ my Rofin Laser Welder for a month now and
absolutely love it. A great tool for eliminating a lot of headaches.
My question is, How do you avoid pitting when laser welding White
gold? I believe its caused by the zinc being vaporized by the laser
beam. I have started using 18k white 28ga and that is helping, but
not solving the problem. Also, when laser welding silver, I am using
a black sharpy to cut down on the reflection with silver. Do you
guys/gals have any other suggestions for minimizing reflection.

Thanks,
Kevin Fertenbaugh
Hakso Jewelers
www.haskojewelers.com


#2
     How do you avoid pitting when laser welding White gold? 

Shorter pulse lengths, like around 1.5 milliseconds, seem to help,
as does being sure that you use no more power than needed to get the
job done. Punching deeply into the metal causes problems. If you
don’t have an argon tank set up, get one. Argon makes a substantial
difference with nickel white golds. And I find that sometimes I have
to go over a weld area a couple times with the focus opened up enough
so it’s just “polishing” the surface. set the htz (repeat rate)
fairly high, so you can quickly walk it over the weld a couple
times. Set this way, the laser is only barely penetrating into the
metal, and what happens is that any pits just below the surface
reduce the ability of the metal above, to dissipate heat. so the
laser is just barely melting the surface, but when it hits over a
hidden pit, the pit then opens up, and the next shot lets it fill in,
if you’ve got the power settings right. The other thing that will
help (a lot) is to use pulse shapes gentler than the standard square
wave. A sine wave pulse that ramps up to maximum only briefly, then
ramps slowly back down again, can be used with longer pulse lengths,
and will reduce both pitting and weld cracking as it allows the metal
to be molten a little longer without overheating, and then the slower
ramp down allows a little annealing too. One characteristic with laser
welding is that the metal is more reflective when solid than when
molten. So the power needed to initially melt the metal is more than
is needed to keep it molten. A pulse that’s strong enough to melt
the metal initially, then reduces the power so as not to overheat the
metal while continuing to keep it molten will allow deeper
penetration. A pulse that starts high, steps down to a lesser power
for a bit, then ramps off, sorta combines the properties of both the
above…

 Also, when laser welding silver, I am using a black sharpy to cut
down on the reflection with silver 

We use red sharpies. The red is just as effective at allowing the
metal to absorb the pulse, but it’s easier to see the metal through
the marker. We use this on other metals too, including white gold,
to allow you to weld at lower power settings.

Peter


#3

Hi Kevin, Congrats on the laser! Rofin has a nice machine. I’ve
experienced similar problems with white gold. I started using
palladium white alloys and I’m getting good results. I’m not a
metalurgist, but I can’t help but wonder if nickle might also be a
culprit (besides the zinc). Though lasers can weld dissimilar
metals, my experience has been that metals with very different
melting/cooling rates can cause some cracking and poor welds. But,
what do I know!? If you have to weld in areas that have white gold
solder residue present, grind out the residual solder and then try
it. This happens a lot with platinum. Don’t even try to laser plat
where it has been soldered with white gold. Cut out the section that
has white gold solder and then weld with plat.

As for Sterling silver: some time ago I started using silver solder
as the filler and not silver wire. I don’t have to mask it to cut
down on reflection and I get no pitting or cracking from the metals
cooling at different rates. Cut the solder in small strips, much
like the size of the wire you are using, and weld away. Saves a lot
of time and it works for me!

You are welcome to call me anytime. Don’t know if I can help, but
I can tell you what I’ve experienced.

Bob Staley
B.Staley, Goldsmiths & Precision Laser Welding


#4

Hi All,

Been awhile since I last posted. Peter and the other Laser welding
group, I am still having problems with pitting in the metal when
welding white gold. I’m about to give up on this process if I can’t
find a solution. I’ve tried many different settings, including
adjusting the time the metal is exposed to the light to the power I
apply and the size of the beam. I have also tried creating different
pulse shape to minimize the pitting. I have also went to using 30GA
18k white wire thinking the hire Karat may make a difference. 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.

Thanks in Advance,
Kevin Fertenbaugh
KEF Jewelry Designs, Inc.
kevin@kefjewelrydesigns.com or @Kevin_Fertenbaugh1


#5
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


#6

Hi Peter, Thanks again for your input. I’m going to contact Rofin
first thing today to get the low flow regulators and pick up a large
tank of argon. I really appreciate your first hand knowledge of
this subject and knew you would come through. I did test using a
short MS setting and lower power today and noticed a difference. My
problem was I didn’t have the right combination of Pulse shape
setting, MS, and beam diameter to put it all together. Thanks to
everyone who gave input and for your personal advice Peter.

Thanks,
Kevin Fertenbaugh
KEF Jewelry Designs, Inc.
kevin@kefjewelrydesigns.com or @Kevin_Fertenbaugh1


#7
My problem was I didn't have the right combination of Pulse shape
setting, MS, and beam  diameter to put it all together. 

If your machine does pulse shaping, the use a shape with a slow ramp
down in the power, and then you can try longer pulse lengths. The
idea is that the slower cool down allows the weld to stress relieve
or partially anneal, thus reducing cracking. Short pulses are
sometimes useful with curing porosity, but I find it’s more important
to eliminate the cracking of the welds. While it’s good if you can
broaden the beam to lower the heat levels in order to get a smoother
weld surface, I’ve found that sometimes this makes cracking worse.
the reason is that with a setting that just glazes over the surface
giving those nice smooth surfaces, the weld penetration is much less,
and the thickness of the weld being thinner, it’s strength to resist
the stresses of the metal’s shrinking/contraction as it cools, is
less. With a deeper weld depth, the cooling mass is more able to
resist that stress, even if it then leaves a rougher weld surface.
one solution is to use another pass with filler wire to build up the
surface of the weld thicker than you’ll need, so that even though the
surface of the weld isn’t so smooth, you’re then able to grind/file
it down to a uniform surface again. What’s left then should be good
metal, if you’ve got it right.

peter