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Hardening cast 900/100 Platinum/Iridium ring


#1

Does anyone know the process, if there is one, for heat treating /
precipitation hardening 900/100 Platinum/Iridium. It is a cast ring
with diamonds already set in it.

Thanks,
Eric in Indiana


#2
Does anyone know the process, if there is one, for heat treating /
precipitation hardening 900/100 Platinum/Iridium. It is a cast ring
with diamonds already set in it. 

There isn’t such a process for that alloy.

The only way to harden 90/10 iridium platinum is work hardening it,
and as with most platinum alloys, it work hardens only slowly.
Burnishing the surface thoroughly with a polished carbide burnisher
can improve surface quality and resistance to scratching, but this is
only a minor surface improvement in actual hardness, but the
improvement in appearance is quite real, and worth the effort in many
cases, allowing the higher level of fine polish attainable with
rolled and drawn or forged platinum instead of what the as cast metal
will usually take, and the improvement in scratch resistance, while
not large, is still enought to notice and be worth the effort.

Rhodium plating, not commonly used on platinum, can also be used to
improve the surface hardness and resistance to scratching, since
rhodium plating is quite a bit harder than platinum itself. But then
your metal no longer looks like platinum in color…

There ARE platinum alloys that can be hardened. Heat treatable
platinum alloys such as Hoover and Strong’s Platinum SK are based on
the work the late Steven Kretchmer did to produce his signature
tension set rings in platinum. Some other refiners also now offer
similar heat treat platinum alloys, but these are not alloyed with
iridium. Even with these, there are limits, since the hardening
procedure involves heating the metal to the usual platinum annealing
temperatures and allowing it to slowly air cool. These temperatures
are generally too high for stones, including diamonds, so stone
setting generally has to be done after the heat treatment.

Peter Rowe


#3

Platinum/iridium is not heat treatable.

James Binnion
James Binnion Metal Arts


#4

put it in the Magnetic Tumbler for a couple of hours. yhis works for
all sorts of things that need to be work hardened


#5
put it in the Magnetic Tumbler for a couple of hours. yhis works
for all sorts of things that need to be work hardened 

Don’t be silly. No insult intended, but this is just plain totally
wrong.

The tiny pins of a magnetic tumbler do a nice job of brightening up
(burnishing) even tiny otherwise inaccessable areas, but they don’t
have anywhere near the mass or energy needed to do any actual
deformation of the surface that would give any measurable increase in
hardness, even for metals that work harden more easily.
Iridium/platinum is highly malleable and work hardens only slowly
even with drastic work like rolling, drawing, forging, etc. Even
tumblers that use heavier steel shot will give only a minor
improvement in surface hardness, and that only a very thin layer, to
the most work hardenable metals. And platinum simply isn’t such.
Magnetic tumblers are very useful tools for helping to finish
detailed items and surfaces, but they do absolutely nothing to
increase hardness in platinum, or for that matter, other metals. Even
rotary or vibratory tumblers with heavier larger steel shot don’t do
much hardening, and what little they do is a thin surface skin only.
Both these tools DO offer substantial improvements in finish and
polish and help with things like closing up minor surface porosity in
castings (steel shot especially, magnetic tumbers to a much lesser
extent). But any significant hardening the metal is not something you
should expect them to do.

Peter Rowe


#6
No insult intended, but this is just plain totally wrong. 

If this is wrong then why do I get results ? maybe you should try it
then admit that it does work, especially on things like sterling ear
wires or sterling earring posts and Platinum prongs - goo


#7
If this is wrong then why do I get results ? maybe you should try
it then admit that it does work, especially on things like sterling
ear wires or sterling earring posts and Platinum prongs - goo 

First, remember that the original question was specifically about
90/10 iridium platinum, not sterling or other metals… And it was
about cast items, which generally don’t include ear wires (though it
may include prongs of course). And my response was primarily aimed at
your reference to magnetic tumblers, which are far gentler than steel
shot in a vibratory or rotary tumbler. But anyway…

Imagination is a powerful thing. The tumbled items will look better,
(sometimes a LOT better) so one can easily assume they are also
harder. I’ve been guilty of such wishful thinking myself at times.
Ear wires might be a special case if the tumbling action causes them
to repeatedly flex back and forth. That could indeed cause some
hardening, especially with sterling, and more likely with steel
shot. But platinum in a magnetic tumbler? I’ve never seen any
significant hardening.

As to trying it, I’ve had steel shot tumblers in my own shop for 30
years, and a magnetic tumbler for a decade now, and use both types,
with all metals. I too have hoped for some increase in hardness with
a magnetic tumbler, but actually comparing un-tumbled with tumbled
has demonstrated to me that there is not any actual increase in
hardness that I can detect, much though I’d like to. And I’ve got
good long term observational experience with jewelry I’ve made in
the past, later seen back for cleaning or service, and have been able
to take note of whether things prepared in certain ways, such as
tumbling, differ in their long term durability and toughness, etc. If
tumbling, which I don’t do to everything, made any clear difference,
I’m pretty sure I’d have noticed by now…

However, who knows. Perhaps I’ve been misled and am missing
something. if you think your seeing an increase in actual hardness,
try this test.

PLEASE try this test.

Take a piece of platinum wire, fully annealed. Pull just enough to
get it dead straight and uniform. Anneal again. Cut into two exactly
equal lengths. Best if they are at least a couple inches long, but
still a size that fits comfortably in your tumbler without hanging
up. Tumble one. Now take each, holding just by one end, extending
horizontally, and hang a weight on the other (bend into a tiny hook
if you like to make this easier) Use a weight enough to cause the
wire to flex/deflect downwards a bit. Measure the degree of
deflection for each. Do it again with more weight, enough so it
actually leaves the wire bent, ie enough weight so it overcomes the
elasticity of the wire. See if one bends more than the other. Come
back and tell me, and Orchid, if you find any real significant
difference.

I’ve done exactly this with several variations, and found no
significant difference with the magnetic tumbler (and I ran it a full
two hours, that’s resetting the cycle and running twice, much more
than I’d normally do) With steel shot running overnight in a fairly
robust rotary tumbler, using 22 guage wire about two inches long, I
did see a slight increase in the wire’s stiffness. But it was a small
difference, not enough to give a significantly longer life to jewelry
made with that wire instead of the un tumbled one. And some of the
difference may simply have been that tumbling bent it slightly and I
had to straighten it out again a bit after tumbling. If your results
really are different from mine, I’d really like to know about it,
since I’d then try to duplicate your results, and my jewelry might be
the better for it. So please, try this, and report back to us on what
you find. Perhaps somehow your equipment or methods are doing
something different from mine.

You might also refer to recent discussions (within the month or so,
here on Orchid) on just this topic. Jim Binnion in particular gave
references to several pertinant sources on the subject,
which back up my statement (his statement at the time) that tumbling
does not make a big difference in hardness or any effect that
penetrates much into the metal. In fact, I’d had the impression
before Jim’s references that the effects of steel shot ( not the
much gentler magnetic tumbler) penetrated deeper into the metal. But
Jim’s sources say no, and I tend to believe him…

Also, note that I’m talking here about actual hardness of the whole
piece of metal, such as would make a difference in how platinum gets
dented up, or bent out of shape or deformed, or the strength of a
prong holding a stone, etc. I’m not arguing that steel shot tumbling
will somewhat improve the resistance of a platinum surface to very
minor damage like scuffing the polish or slight scratching. A thin
surface skin does get burnished, and that hardens it a little,
especially with silver or gold. Less so with platinum, which work
hardens more slowly. But it’s a very thin layer, not enough, for
example, to keep an ear wire from bending. At least, as detailed
above, that’s been my experience.

Improved appearance and finish and final polish? Yes. Improvements
in the porosity often seen in cast platinum? Certainly. But
improvements in real hardness and durability? Nope. Not that I’ve
seen. Not in iridio-platinum.

Peter


#8

Hi goo,

The layer that gets hardened is only a few microns thick. It feels
harder as in the case of the earwires but it is only a thin sheath
that will wear away very rapidly on any area where there is any kind
of abrasion. So on things like the prongs any advantage is very
short lived if it is on a ring. On things like earrings or pendants
the process will give a bit more advantage as long as you dont polish
after hardening. If you polish after tumble hardening most if not
all the hardened layer will be gone.

James Binnion
James Binnion Metal Arts


#9
If this is wrong then why do I get results ? 

Gustavo might have a point here.

I too have had great success hardening silver ear wires in my rotary
tumbler.

I don’t know about platinum though. I mostly hand fabricate the
stuff old school style so it’s not such an issue for us.

Have fun and make lots of jewelry.
Jo Haemer
www.timothywgreen.com


#10

I would like to make a correction, my magnetic tumbler is an IKOHE,
model K149-100 from mawah NJ which is probably why it works for me
(not one of those cheaply made junk ones) somtimes it takes more than
two hours to work harden platinum prongs. if it is not working for
you P.R. maybe the platinum did not get alloyed or mixed right ?
Sometimes its better not to over analyse stuff if something works, it
works, for platinum ir or plat rueth or platinum anything, excuse me
but, the person needed a soloution, and I offered mine. I do not have
to be right all the time but this time I am, and I can accept that. I
do other stuff that people scoff at as well but somehow it works for
me after 30 years in this business of surviving by pulling rabbits
out my back pocket I am just be thankfull to have results instead of
a scientific explanation - gh


#11

First, remember that the original question was specifically about
90/10 iridium platinum it does work on cast platinum !