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Forming 24K Gold


#1

I am attempting to form a domed disc from what used to be a 24 kt
Chinese ring. Can the metal be formed totally without annealing? I
have rolled it to begin flattening, and so far so good, but should
there be a need to anneal at some point, and how do I know when I
have reached it? I am familiar with other karat golds. How does this
differ?

C. Valli


#2

As with all karat golds, 24 works easier if you anneal it. You’ll
probably never reach a point where you need to anneal it.


#3

I wouldn’t anneal 24k, it goes so soft that it takes for ever to get
anything you can wear. I am pretty sure you can work this stuff to
your hearts content and never anneal. If you get afraid that you need
to anneal it, plan on work hardening at least 50 percent reduction
afterwards.

Dennis


#4
I am attempting to form a domed disc from what used to be a 24 kt
Chinese ring. Can the metal be formed totally without annealing? I
have rolled it to begin flattening, and so far so good, but should
there be a need to anneal at some point, and how do I know when I
have reached it? I am familiar with other karat golds. How does
this differ? 

Sorry I don’t know how quickly or if 24 kt gold hardens. But since
annealing is not a difficult task would you not just be safe and do
so rather than sorry. I work with silver and I know when the metal
needs annealing when it becomes harder to work. You don’t want to
leave it until the metal tears.

Cheers, Renate
www.renatesommerjewellery.com.au


#5

Dennis,

Only alloys can be annealed. 24K gold, being pure, cannot be annealed
and does not ever need to be. Mechanical friction, beating, etc tend
to “order” the molecules of an alloy; heating and proper cooling
tends to “dis-order” those molecules, making the metal workable
again. Some alloys just need to be heated to a certain temperature
and allowed to cool, others need to be quenched properly. Oppi
Untracht’s work goes into good detail on te subject for both ferrous
and on-ferrous alloys.

Wayne Emery
The Gemcutter


#6
Only alloys can be annealed 

Um, no, sorry. This is just plain wrong. On a weekly basis, I
roller-print copper, causing it to work harden like crazy, then I
anneal it to butter-soft. It is not an alloy.

Noel


#7
Only alloys can be annealed. 24K gold, being pure, cannot be
annealed and does not ever need to be. Mechanical friction,
beating, etc tend to "order" the molecules of an alloy; heating and
proper cooling tends to "dis-order" those molecules, making the
metal workable again. Some alloys just need to be heated to a
certain temperature and allowed to cool, others need to be quenched
properly. Oppi Untracht's work goes into good detail on te subject
for both ferrous and on-ferrous alloys. 

Work hardening comes about because the stress of cold work strains
the crystal lattice in the metal or alloy and eventually enough
strain can be built up in the lattice that it will break or fracture
rather than become further strained (strain is the geometrical
expression of deformation caused by the action of stress on a
physical body). The strain in a metal or alloy can be relived by
annealing. That is the heating of the metal to the point where the
crystals start to re-grow and the strain is relived from the matrix
in this re-growth. The temperature that annealing occurs at depends
on a variety of factors but the quality of the annealing depends on
how much strain was in the matrix before annealing. the more strain
the smaller the resulting crystals will be and the more ductile the
metal will be after annealing. This is why it is not a good idea to
anneal too often in the working of metals. A good rule of thumb is a
50% reduction in section between anneals.

All metals work harden, gold included, and will re-crystalize when
heated to the appropriate annealing temperature.

Ordering is not related to cold work or work hardening but the
composition of alloys the relative size of the atoms in the alloy and
their solubility in each other. Some examples gold-silver alloys will
not order because their atomic size is virtually the same so they can
freely substitute for one another in the lattice and there is no
particular “order” to their distribution in the matrix. Gold-copper
however will order if mixed in the right proportions and allowed to
sit at a certain temperature range. For example 18K red gold (gold,
copper) will order and become brittle like glass if allowed to spend
much time at temperatures between 770 F (410 C) and 482 F (250 C). It
forms the intermetallic or ordered compound AuCu (one gold atom for
every copper atom) and every atom of gold will be in a certain
location with respect to every copper atom ie they will be ordered.
However if it is rapidly cooled by quenching from above 770F it will
not order and will remain ductile. Some intermetallics are never able
to dis-order till they melt like the purple gold intermetallic of
gold aluminum AuAl2 (two aluminum atoms to every gold atom) this
compound is always brittle and cannot be heat treated in any way to
make it ductile.

It just takes a lot of cold work to harden pure gold but once it is
work hardened it can be annealed to restore its full ductility. It
will however never get very hard, annealed fine gold is 20 on the
Vickers hardness scale (HV) “hard” fine gold is 58 HV in comparison
annealed sterling silver is 56 HV, work hardened sterling is
140-180HV, 14K standard yellow is 190 HV and typical 18K Nickel white
is 220 HV.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#8

I can work harden 24k gold and then soften it by bringing it up to
red hot, do it all the time. Is this not annealling?


#9

Dear Wayne,

I did check Oppi Untracht’s books, and found that he does not
recommend annealing. I have managed to form the metal as desired
without annealing. The edges got a little ragged, but I supposed I
could have gone back in and remelted them if they had gotten out of
hand. The metal is still quite soft, but will work for my purpose (a
reproduction of an ancient Roman “bulla”, a good luck charm worn by
patrician and freeborn children). Thanks for your time!

Colleen Valli


#10

Jim, can you post this same as it relates to .9999
silver?

Thanx