Does anyone know the F temperature and time needed to work harden ?
Or have an alternate idea?
None of the pure metals can be hardened via heating. Not pure gold,
nor pure silver, nor pure copper, and many more.
The heat treatment is not actually work hardening. work hardening
happens because the crystals that make up the structure of the metal
become distorted, and over time, additional distortion becomes harder
to do because the boundries between crystals are less able to be
distorted than the crystals themselves, and with work hardening,
those boundaries become stretched. They then resist additional
With heat treatments, what generally has to happen is that the metal
consists of two or more elements (metals or other), and with heating,
one or more of those metals becomes segregated into separate
crystals, or another structural change happens that makes the result
more resistant to distorting the crystals. With both silver/copper,
and gold/copper, it works because copper is not actually all that
soluable in the other two, so with heating, the original crystals of
mixed metals separates out into discrete copper crystals along the
boundaries between gold or silver crystals. That makes those crystals
and their boundaries much more locked in shape and takes much more
force to then distort those crystals, thus they become hardened.
Because your copper does not have a convenient added componant which
can come out of solution or otherwise change structure with heat, you
cannot heat harden it.
As I noted, actual work hardening requires that the metal crystals
actually distort and stretch. That is difficult to achieve with
simple tumbling because the depth to which that distortion can happen
without actually also distoring the shape of the finished work, is
minimal. So tumbling may compact the surface slightly, making it a
little harder, but the overall wire won't harden that much.
At this point, with the chain finished, you won't really be able to
harden the wire much.
There is one method that occurs to me though, but it's considerably
more involved. By the very nature of the process, an electroformed
copper deposit comes out of the electroforming/electroplating bath
already quite hard, because the process produces a chaotic mix of
small crystals rather than a uniform even structure. So if you were
to put a fairly heavy copper electroplated or electroformed deposit
on the chain, that would effectively increase the hardness of the
chain. electroforming and electroplating are essentially the same,
except electroplating isn't as thick. Also, if your plating bath is
the type that produces a bright shiny deposit, it will be harder than
the simpler dull plating.
But as you can guess, putting on a thick enough electroformed layer
on your chain is more than a simple process in terms of needing other
A better approach, before you make the next one of these chains,
would be to start with hardened wire. Pulse arc welding the links
will give you a small annealed/soft area at each weld, but it will be
small, not enough to affect the overall hardness of the chain. You
could harden the copper wire by buying it hard already, or by work
hardening it. You can do that by starting with heavier wire, and
drawing it down with a drawplate. You'd have to reduce the diameter
of the wire by about 50 percent to get a good workably hard wire,
though lesser reductions will help too, just by less. Even just
putting one end in a vise, the other in pliars and giving it a good
sturdy pull to slightly stretch it will harden it a little. But just
a little, though it's enough to notice. The other way, if your wire
is already the right diameter, is to twist it. Put one end in a vise,
the other in the chuck of your flex shaft or an electric drill, pull
it straight with just a little tension, and let the drill twist it.
You'll see a faint twist striation pattern on the wire so you can see
how much it's twisted.
It will take more than just a little twisting to get it reasonably
hard, but this doesn't much change the shape of the wire outside of
that surface texture it will form. Either way, once the wire is
hardened, then make your chain, and with this, is should then be hard
enough to resist the steel shot tumbling which will nicely clean up
that faint twist pattern if you wish.
One final option is to use an alloy of copper that CAN be heat
treated. There is such an alloy, called Beryllium copper. It's made
for use in manufacturing springs. The down side of this is that it
can be toxic to work with. I don't recommend this route for jewelry
if it will be in contact with skin.
Back again to the subject of heat hardening (or as it's more
properly called, age hardening or precipitation hardening). Not all
alloys of even two or more metals will do this. It requires that, on
heating, one or more of the alloy componants seperate out from the
others. Usually, this requires that it is not fully soluable in the
other/parent metals. This is true with silver or gold alloys that
contain copper, as the copper is not fully soluable in the others.
But it is not true with an alloy of gold and silver, since each is
fully soluable in the other, and heating causes no separation of the
two, just annealing. As a general rule, normally the only way to work
harden metal is to work it, to distort the shape of the crystals,
which is why it's called work hardening. Various forms of heat
treating to age harden or percipitation hard metal alloys differ
with the different alloys, and are easily more of a subject for
confusion because it's confused often with the totally different
process of heat treating steels which happens due to a totally
different type of structural change in the steel, from what happens
with our non-ferrous jewelry metals...
Hope this helps