One CAN weld with sterling filler wire, but getting good
welds is hard to do. Peter-- When and why would you weld silver,
rather than solder it? Is this distinct from fusing? Thanks for the
clarification,
Noel, I was referriing to the use of a laser welder. Laser welders
are capable of joins in pieces which cannot be conventionally
soldered, due to heat sensativity, since the overall piece need not
become all that warm, even though the weld area itself is hot enough
to fuse metal. It doesn’t do quite the same type of joint as
conventional soldering, since the laser is “line of sight”, and
penetrates only so far into the surface, while solder can flow along
a well fitted capillary seam to areas you cannot see.
In laser welding, just as with electric arc or other oxy/acteylene
welding on steel, etc, one usually needs to add additional metal to
the joint, and this is usually done by using, as a miniature version
of a welding rod, very fine (.25-.30 mm, or thereabouts) wire of the
metal being welded. The laser then not only melts the joint area of
the pieces being joined, but also a bit of the wire, with each pulse,
so that you build up, with successive passes, a weld bead, and can
build up the joint area above the original surface if you want, or at
least, to a level full join, just like a solder fillet, if you like.
My comment was that using sterling silver or filler wire can be
difficult, since welding sterling silver or fine silver takes rather
high power levels with the laser, and also, especially with lasers
that don’t offer pulse shaping, it can be sometimes difficult to weld
silver without getting cracking of the welds, since a laser weld bead
is often highly stressed and work hardened metal as it first comes
out of the laser. The use of a different, lower metal alloy, like
silver solder, as the filler wire, helps to solve these problems.
The question of when you’d torch fuse silver, vs torch soldering it,
simply depends on what you’re doing, and whether you can tolerate
solder, with it’s lower melting point and sometimes color
differences, in your seams. The question of whether to laser weld a
joint, vs soldering it, isn’t just related to silver, but to all the
jewelery metals. Laser welders do some things much better than torch
soldering, such as highly pinpoint joints that don’t disturb
neighboring metal, the ability to actually build up the metal with
weld beads, rather than jost join two pieces, and the ability to
control the heat damage that can occur with soldering (including, if
you don’t want it, annealing.) Since first getting a laser to use at
work, I’ve become totally hooked on these machines, to the point of
buying one for the personal shop too (an old beat up and therefor
cheaper one, to be sure, but i still spent/borrowed more to buy the
old laser than i did for my much newer (though also used) Corolla…
Nevertheless, lasers have their drawbacks. For one thing, despite
the precision, sometimes the joint is actually not as clean. Solder,
done well, can be an almost invisible capilary join. Laser welds can
be small, but they do have width, and the deeper penetration you need
into the metal, the wider and more disruptive the weld can get. So
though laser welds can avoid solder discoloration, and can avoid
joints coming apart with subsequent heating, or things like that,
sometimes they need more clean up than a solder joint does. And,
joining larger pieces of metal, can mean several overlaid passes
with the laser to get a fully filled joint, often having to then
repeat the process on the other side of the joint too. Though the
laser is very fast on a per pulse basis, it often takes a whole lot of
pulses to actually complete a joint, and sometimes, by the time you’re
done, you’ve spent considerably more time laser welding a joint than
it would have taken to flux the thing and flow some solder in with a
torch.
I often use, in building pieces, both soldering and laser welding,
rather than just one or the other. Often, I’ll use the laser to
discretely tack pieces in position for subsequent soldering. That
solves all the juggling around and third hands and other tricks to
try and hold pieces in position for soldering, while still giving me
the clean capillary joints of a solder seam where I want them.
Saves me a LOT of time… And in places where I can use a pure
laser weld, I then have a clean joint of all the same metal, no real
seam line or visible joint once the weld is cleaned up, especially if
I’ve then annealed or stress relieve the weld so it’s the same
hardness as the surrounding metal. Such weld joints can often be
considerably stronger than a soldered joint as well, especially in
those cases where, were you to have soldered it, you’d have had to
use a medium or easy grade of solder. Even when welding silver
with a solder based filler wire, the joint can be considerably
stronger than a normal solder seam would be.
cheers
Peter