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Hardening Argentium Wire?


#1

Good Day,

I have been working with argentium sterling silver for over a year.
I wonder if someone can offer some advise regarding the best way to
harden round wire. Here are my questions:

  1. I recently tried to harden some 21 gauge wire (the project I am
    working on won’t allow me to go any thicker). As suggested here on
    Orchid, I heated treated the argentium in my oven at 450 degrees
    (the hottest it will go) for about 2 hours. I did not anneal it ahead
    of time (some info I have read suggested this doesn’t make a
    significant difference). I did notice it was harder but not nearly as
    hard as when I recently tried twisting it with my drill. Does twisted
    wire typically have a harder end result than heat hardening or am I
    not heating it at a high enough temperature?

  2. I generally work as I go with smaller lengths of wire (let’s say
    1 - 2 feet). When twisting the wire in my drill, I clamp the wire
    into the chuck and hold the other end with a pair of pliers until
    taunt and then start to twist. The problem is I don’t know how long
    to twist or how many rotations. I have read that you can twist the
    wire until one end breaks but I am worried that over twisting will
    make the metal brittle. Also, is there any advantage/disadvantage to
    twisting in one direction and then reversing the drill in the other
    direction (toggling between the two)? While twisting I have noticed
    under magnification that the surface of the wire is not as smooth
    with tiny breaks on the surface. I assume this can be polished out
    but not with just a final polish (I am guessing at least a two step
    polish)?

  3. When making jump rings I am coiling around a mandrel, hardening
    the coil in my oven (as described above), polishing the coil and then
    cutting into rings. I now wonder if I should be hardening my wire by
    twisting it first and then coiling around a mandrel as this seems to
    achieve a harder end result. I prefer the heat hardening method
    because it does not distort the surface of the metal.

I rarely need to post questions as I usually find the answers in the
archives from all of you (my Orchid teachers). It always amazes me
the generosity of time that Orchid members give.

Any suggestions or input are very much appreciated.

Sincerely,
John


#2

Hello John, you’ve asked some good questions. Let’s take them in
order:

... Does twisted wire typically have a harder end result than heat
hardening or am I not heating it at a high enough temperature? 

You are correct, any significant amount of work hardening will
produce harder metal than precipitation hardening. Precip hardening
isn’t really a replacement for work hardening, it’s a different
technique to get good hardness, though not maximum hardness, where
work hardening is not practical.

... I have read that you can twist the wire until one end breaks
but I am worried that over twisting will make the metal brittle. 

Again, I’d say your instinct is correct. I’ve done the “twist 'til
it breaks” trick before too and noticed micro-cracks appearing
elsewhere along the length of the wire. Also, you have little
control over where the break occurs (see next paragraph). Unless
these micro-cracks are something you actually want – needless to
say that’s rather unlikely – you might want to use a different
method.

Part of the reason this isn’t an entirely successful technique is
that it can be quite tricky to anneal a coil of wire perfectly
evenly throughout. In other words you’re going to end up with wire
that has varying hardness before you start your twisting process
and that means that the twisting is very likely to cause hardening
faster at some points than others. It’s at those "harder, faster"
points that you’re going to get micro-cracks and quite possibly
total failure (it snaps).

 Also, is there any advantage/disadvantage to twisting in one
direction and then reversing the drill in the other direction
(toggling between the two)? 

Hmmm, my memory is letting me down a bit on this one but I remember
I did the reversing trick only once because the results were
terrible. As I recall it the hardening was very inconsistent along
the length of the wire and that was quite useless to me, not to
mention that the reversing was MUCH more likely to cause breaks
somewhere along the length of the wire.

FWIW I suggest you might want to alter your twisting process to
twist longer lengths of wire at a go. For instance you mention that
you “clamp the wire into the chuck and hold the other end with a
pair of pliers”. I’ve found that this isn’t an ideal technique
because it leads to too much variability in the final results.

A better approach, IMHO, is to anchor one end of the wire to a hook
in wall or shelf, pull the wire taunt, and then twist. This allows
you to do longer lengths of wire (I’ve gone as long as 2 or 3
meters) which, again, I’ve found helps get better, more consistent,
and more controllable twist-hardening results.

 While twisting I have noticed under magnification that the surface
of the wire is not as smooth with tiny breaks on the surface. 

I see two possibilities heRe: (a) they’re not actually breaks,
they’re linear imperfections that are not very noticeable before the
wire is twisted but become quite noticeable because of the twisting.
I’ve often seen this on my wire, largely because I draw it myself as
opposed to buying it at pre-determined gauges.

And (b) they are actually cracks which means that you’ve
over-hardened the metal and stress cracks are starting to appear.
When this happens it is usually caused by inadequate or uneven
annealing prior to the working, in our case it’s the twisting,
process.

 When making jump rings I am coiling around a mandrel, hardening
the coil in my oven (as described above), polishing the coil and
then cutting into rings. 

I would do it slightly different: pre-polish, coil, cut, then
(anneal for best results) and harden. Tumble polish with stainless
steel as a final step if necessary.

If you do the twist-harden then coil method you will, in my
experience, have a lot of problems getting tight and well-formed
rings. Besides, who needs the hassle?

Cheers,
Trevor F.
in The City of Light
Visit TouchMetal.com at http://www.touchmetal.com


#3

Hello, John -

Twisted wire will be harder than heated wire. You can leave it in
the heat for longer and maybe get it harder than it is after two
hours (it will not be damaged by longer time), but you will get it
harder by twisting. So hard that it becomes brittle and breaks.

The twisting and then anti-twisting, you will not like the results
(but I cannot tell you WHY!). Try it with copper wire and see what
happens…I suspect it will be difficult to prevent kinks while you
do this, and then you will have to anneal to get the kinks out. (my
guess, I haven’t done it)

Since hardness of the wire is important to you, I would sacrifice
several lengths of wire (12-18"; minimize your loss…cut up the
waste finely & make little balls for granulation…oh, sorry - off
topic, where was I?) and twist to varying levels. One you take to
breaking point, carefully counting revolutions. Examine under
magnification. Next, twist to half the revolutions, compare
magnification and assess hardness. Third, go halfway between the two
points and compare to previous (breaks and hardness).

Decide which range gives you the best balance of harness that
minimizes polishing time, then run a fourth try in the middle of the
range. Example: if the twisting to breakage and the middle effort
gave better results than twisting halfway to breakage, then use 3/4
of the revolutions to breakage and examine again. This will help
narrow the range of effort that gets the best results.

Have your heat-hardened wire on hand as a control. Compare all
work-hardened results to that, then go with the most efficient
method that gets you the results you want.

Sorry if I’m giving you advice you have already figured out; you
were asking if anyone’s already done it and what the results were.

Anyway, good luck on your project. You have given me ideas for
something else I’m doing!

best regards,
Kelley


#4

Correction from my original post:

I indicated that my oven only goes as high as 450 degrees. It
actually goes to 500 degrees. I usually heat treat for 2 hours at
this temperature in a glass dish with no cover.

John


#5

I harden any argentium @ 580 for about 45 min


#6

John:

I am a metallurgist and am not aware that you can harden silver by
HEATING it. Generally, metals are hardened by cold working, and the
stress from that is RELIEVED by heating (first comes RECOVERY,
followed by RECRYSTALLIZATION and GRAIN GROWTH). In other words, the
heating process will only SOFTEN your metal, not harden it. Some
alloys will AGE HARDEN, which means alloying constituents will
precipitate at grain boundries and “pin” individual grains/crystals
so that slippage between grains becomes more difficult. Age hardening
happens only in certain alloys; 18 karat white gold is notorious for
this. To acvhieve work hardening, you should start with wire (or
sheet) in a guage thicker than you need; pull through at least two or
more holes in your drwplate until you achieve the guage you need, and
the resulting wire should be pretty stiff. This may require a little
experimentation to get the exact condition you need. I am just now
starting to work with argentium myself, and still need to get used to
its various properties.

Chris van Laer
ASTERISM Services


#7

John

You didn’t mention if you are making you own wire, if you are I
would just draw it down to size without annealing. With a little
practice you should be able to judge how many reductions you need
before the metal requires annealing and then start out with a
sufficiently larger size so that when you reach the size you want, it
will be clean and shiny and fully work hardened. A few broken wires
will teach you where the limit is.

Dennis Smith - thejewelmaker


#8

Thanks everyone for your explanations/advise. I have a couple more
questions from your responses if I may.

I did not anneal my wire before I started twisting as I purchased it
dead soft from my supplier. I assume annealing first is not
necessary when working with dead soft?

Trevor, I will take your advise and instead of clamping the wire in
my drill chuck and holding the other end with a pair of pliers, I
will attach one end of the wire to a hook and then pull taunt. I take
it that by holding with pliers you are suggesting that my tension may
not be constant and possibly causing a problem.

As far as what the surface looks like when I twist, I took a closer
look under a loop and your description " they’re linear
imperfections" is more accurate than mine “tiny breaks on the
surface”. The appearance under magnification is more like waves which
makes sense since the wire is twisting into itself. I think the
polished surface changes when the wire is twisted and maybe it is the
texture difference I am seeing? It isn’t smooth though. I can feel a
difference when I run my fingers along the surface.

With my jump rings, I actually find that heat hardening my coils in
the oven works well (even though I don’t anneal) so if it’s not
broken I won’t fix it. I was just curious if my method was sound. I
was hoping to hear that twisting before coiling is not worthwhile and
I agree an extra unnecessary hassle.

Tim, I take it you are using a kiln to get to 580 degrees? II have
never heard of an oven going that high (except for maybe a self
clean cycle). I wish I had a means to experiment with higher
temperatures to see if that makes a significant difference.

Chris, regarding your statement " I am a metallurgist and am not
aware that you can harden silver by HEATING it." I will let the
Argentium experts explain that one. All of the articles I have read
about Argentium indicate that it is possible. I read and re-read
Trevor’s blogs, Cynthia’s technical papers and lots of other threads
here on Orchid. I use heat hardening in my work often which I didn’t
do when using sterling. I now realized that heat treating has a lower
result that work hardening. Still, heat hardening is very useful for
many applications. As for your other suggestion, I have no drawplate.
Something I would love to try though.

Lastly Kelley, as soon as I read your comments I went in my studio,
stuck some argentium in my drill and went all the way, (twisted
until it broke). Your suggestion of experimenting did tell me
something. It was even harder than my previous attempts because
before I was only twisting less than half as much. The result was
springy and seemed sound so now I wonder if twisting until it breaks
is not a bad approach. I will likely not go quite that far but have
realized that I can twist much more than I was.

This has been a great help. Thanks so much everyone.

John


#9

Chris

I am a metallurgist and am not aware that you can harden silver by
HEATING it. 

Well I am not a metallurgist but you might want to look at your ASM
Handbook Volume 4 in the heat treating nonferrous metals section.
Ag- Cu alloys precipitation harden. Sterling silver given a solution
heat treatment (1200 F-1350 F) then quenched results in a duplex
structure with small amounts of copper rich phase scattered about the
silver rich matrix. When followed by an aging treatment at 535 F for
two and a half hours, the copper rich phase precipitates out and
greatly strengthens the alloy. It goes from an annealed state
hardness of 40 HB and 40 ksi tensile strength to around 90 HB
hardness and 50 ksi tensile strength. A significant improvement.

Argentium has a similar but from what I have been told slightly
greater increase in hardness and tensile properties due to the
presence of the germanium.

Jim Binnion

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550