I had been taught to quench metal (silver & copper) after annealing.
Last night this subject arouse during my class at the Baum school.
So, my question is this: When should you air cool and when is it o.k.
to quench after metal is heated. I’m looking for guidelines the would
cover annealing prior to forging or heating a piece as a consequence
of soldering.
thanks
Ed Ledner
Hi Ed,
Silver and copper can be quenched after annealing to remain in an
annealed state but brass and steel need to be air cooled to be
annealed if you quench after heating it will harden the metal.
If you are looking to forge brass or steel its best to do it hot
(dark cherry red not orange), I have also heard the same is true of
silver but have not put it to the test…
Christine
www.christinebossler.com
With regard to silver or high silver content alloys, Christine’s
comment on forging at red heat is absolutely incorrect, silver goes
"hot short", that is, will readily crack and fracture if subjected
to mechanical stress when the billet temperature exceeds around 550c.
Kind regards
Don Iorns
Dear Ed,
A simple thing to remember for quenching after annealing. Only
sterling silver (NOT ARGENTIUM SILVER!!!) gets quenched right after
annealing. Copper, brass, gold & argentium silver all need to AIR
COOL after annealing. The copper, brass, & gold will temper or get
harder if quenched immediately. Argentium tends to crumble if quench
immediately.
Happy torching!
Ruthie Cohen
Mountain Metalsmiths School
So, my question is this: When should you air cool and when is it o.k. to quench after metal is heated.
When the metal cools to 700 degrees. This topic has been covered
extensively in the archives. Search the archives on the word
annealing, or use google and use the terms annealing and ganoksin.
Hi Ed,
I had been taught to quench metal (silver & copper) after annealing. Last night this subject arouse during my class at the Baum school. So, my question is this: When should you air cool and when is it o.k. to quench after metal is heated. I'm looking for guidelines the would cover annealing prior to forging or heating a piece as a consequence of soldering.
Jewelers and metalsmiths disagree about this—always have, and
always will, I think. Here is my opinion: it is okay to quench when
forging or raising a piece of metal, but do let it cool a bit, so
that it “sizzles” in the water. Shocking the metal by quenching too
soon, so that the water seems to boil and “explode”, can crack the
metal. I recommend waiting even longer to quench after soldering, so
that the water does not even sizzle—so that the construction does
not get distorted by the sudden change. If I want to cool metal a
little quicker, I place it on a heavy piece of steel.
Cynthia Eid
Copper, brass, gold & argentium silver all need to AIR COOL after annealing. The copper, brass, & gold will temper or get harder if quenched immediately.
Ummm…
No, Ruthie, that’s not quite right. Copper does not harden at all
with quenching. The only thing quenching does to pure copper is cool
it. Same thing with Brass. Neither one hardens either with air
cooling or quenching. In fact, if cooled too slowly, some slight
increase in grain size can occur in some metals (though not really
those two), which actually hardens the metal a bit. In the case of
most gold alloys, quenching gives the softer metal, since it stops
the precipitation hardening that can occur with copper bearing gold
alloys (and sterling silver too), as it cools slowly through the
range of about 800 down below 650 or so. Rose and red gold in
particular, MUST be quenched or they can become not just hard, but
very hard and brittle if air cooled. Even ordinary yellow golds, if
they contain copper, do this to a degree, and are softer with a
quench. Many nickle based white golds too, are softer with a quench,
and some are substantially hardened if not quenched. Now, the bit
about air cooling may be due to the fact that some of these, some of
the white golds, and most red or rose golds, need some care in
quenching, because they can be somewhat weak while hot, and if
quenched too hot, can crack. For this reason, some people (including
me) recommend quenching rose golds especially but also any white
golds that are giving problems, in alcohol, rather than water. It
cools quickly enough to avoid hardening, but not as drastically as a
water quench, so it’s less likely to crack the metal.
It’s probably fair to say that the majority of the non-ferrous
metals we use in jewelry will be softer if quenched after annealing.
Those few, like argentium, are the exceptions. The key, however, to
doing this with success is how you quench the metal. Most of these
alloys should be allowed to cool below about 900, which is the point
at which you can still see any dark red glow in subdued light. Once
that glow is gone, you quench. I’ve found a few white golds that seem
to do better if quenched a bit hotter, but most are fine as
described, especially with an alcohol quench. The pure metals,
copper, fine silver, fine gold, etc, couldn’t care less whether they
are quenched or not, since there are no significant changes in
structure between quenched metal or unquenched, other than perhaps a
slight difference in grain size, but most grain growth occurs at a
much hotter temperature range than we quench at anyway, so for the
most part, it’s more theoretical minor details rather than any real
difference. Platinum alloys too, other than the specific heat
treatable alloys, also are softer when quenched, but here you quench
from a good red heat.
Overall, the most important metals which ends up softer when air
cooled, preferably as slowly as possible, are the various grades of
steel. Don’t confuse the practices of hardening or tempering (which
is a process to soften or stress relieve hardened steel, not a
process of hardening it) in steel, with the processes of non-ferrous
metals. Ferrous and non-ferrous metals are generally quite different
in these respects, and practices between the two families can’t be
interchanged.
Peter
With regard to silver or high silver content alloys, Christine's comment on forging at red heat is absolutely incorrect, silver goes "hot short", that is, will readily crack and fracture if subjected to mechanical stress when the billet temperature exceeds around 550c.
Fine silver can be forged at heats up to damn near molten with no
issues. The higher the copper content the more finicky the alloy is
with regards to hot forging but standard sterling can be hot forged
at temps up to 650C 1200F without cracking, I do it regularly. The
biggest problem comes at temps above 704C 1300F when it will indeed
be hot short. The big problems with hot forging sterling is accurate
temperature control and really nasty fire stain form prolonged
exposure to oxygen at forging temps.
James Binnion
James Binnion Metal Arts
Again this is not an area for opinion or disagreement but simple
metallurgical facts. Peter has given the correct in
regards to quenching various alloys.
...brass and steel need to be air cooled to be annealed[;] if you quench after heating it will harden the metal.
I don’t know about steel, but this is not true of brass (in my
experience of working with mainly red brass for the last 30 years).
Judy Bjorkman
The only detail Peter left out is the fun of repairs with diamonds
and red gold. Quench hot for the gold or cooler for the diamonds.
Makes for an interesting judgement call. Get it right and all is
good, wrong and everything is toast.
jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand
The only detail Peter left out is the fun of repairs with diamonds and red gold. Quench hot for the gold or cooler for the diamonds. Makes for an interesting judgement call. Get it right and all is good, wrong and everything is toast.
Here’s the trick that I finally hit upon in one of those rare
moments of clarity…
compressed air. You need to do your annealing with a good compressed
air gun right next to your bench. Instead of quenching in water or
alcohol, quench with a blast of compressed air. The effect is much
like a torch flame heating the diamonds, only in reverse, cooling
them. Gentle enough it won’t break your diamonds, but fast enough to
chill the rose gold enough to avoid that nasty brittleness. Be sure
that your air line is supplying properly dry air. The only accident I
ever had with this method was using an air line in a building where
the compressed air was supplied by the building. The old air
compressor in the basement got enough condensation somewhere,
somehow, mostly in winter, that sometimes, you’d expect a blast of
compressed air and get, instead, a mix of compressed air and water
giving a high pressure water spray jet, rather than just an air
blast… Good way to get unexpectedly sopping wet, not to mention
too harsh a quench for the diamonds. But with a decent air supply, it
seems to work fine. The main problem is the need for more than two
hands. One for the torch you’re still holding, one for the tweezers
holding the work, and then what to hold the air gun with… But you
can figure that out OK.
Peter
compressed air. You need to do your annealing with a good compressed air gun right next to your bench. Instead of quenching in water or alcohol, quench with a blast of compressed air. The effect is much like a torch flame heating the diamonds, only in reverse, cooling them.
I should also have mentioned that quenching in compressed air is not
a full substitute for the usual quench in water or alcohol. It’s a
substitute that I’ve found adequate to avoid excessive
hardness/brittleness from forming in rose golds or white golds or
other alloys that need to be quenched, but which already have diamond
set in them. You do still get some hardening with a compressed air
quench, but not so much as to kill your project, as might happen
with a slow air cool, especially with an 18K red gold (just gold and
copper) Don’t consider it fully the equal of a wet quench if you want
full softness in any alloy that requires quenching. It’s a workaround
for an otherwise tricky situation.
Peter
Peter,
A very nice trick for working with red golds and diamonds. One which
gets filed in my brain
Thanks, jeffD
For what it’s worth on this issue, this is what I was taught: Air
cool copper a bit before quenching
For silver - Size matters! It boils down to the size of the sizzle
in the quenching dish.
The larger and/or thicker the piece of metal, the longer it should
air cool after annealing or soldering before it is quenched.
Your average size earring, pendant or ring can be quenched
immediately. (Although, if it’s a very complex construction, I let it
air cool enough that the water only sizzles gently)
Cynthia’s recommendation/opinion is spot on: it is okay to quench
when forging or raising a piece of metal, but do let it cool a bit,
so that it “sizzles” in the water. Shocking the metal by quenching
too soon, so that the water seems to boil and “explode”, can crack
the metal. I recommend waiting even longer to quench after soldering,
so that the water does not even sizzle—so that the construction
does not get distorted by the sudden change. If I want to cool metal
a little quicker, I place it on a heavy piece of steel."
Jane Walker
For what it's worth on this issue, this is what I was taught: Air cool copper a bit before quenching For silver - Size matters! It boils down to the size of the sizzle in the quenching dish. The larger and/or thicker the piece of metal, the longer it should air cool after annealing or soldering before it is quenched. Your average size earring, pendant or ring can be quenched immediately. (Although, if it's a very complex construction, I let it air cool enough that the water only sizzles gently)
Hmm.
I studied top level precious metals metallurgy courses in Germany’s
major jewelry center, Pforzheim, have read widely (Mark
Grimwade-Brynmorgen press book in the works), and translated
Brepohl’s book which has an excellent section on metallurgy.
If you want maximum softness then you quench immediately upon
annealing. You never should see a red glow from your metal when
annealing (in contemporary lighting). Any air cooling beyond actually
hardens your metal (anything containing copper, all copper alloys,
sterling, most gold alloys).
In all cases wait till any glow is gone from the metal. (You should
not actually see much glow at all) Note that if you watch the flame
color glancing off your metal (on the side, next to the metal, you
will see the flame (with any gas system I have found, including
hydrogen) change to a distinct yellow orange when you have reached
annealing temperature (ok, it varies, but reality is you can use this
indicator for almost any metal, including aluminum) then it is
annealed. This is definitly not the dull red glow (that old hack
comes from the days before electric light, when the ‘hearth’ was
literally a charcoal fire in the deepest darkest recesses of the
workshop-the color, in the dark, was the color of concord grapes-if
you see ANY visible glow off the metal today, then you are damaging
your metal). In other words, glowing red is too hot, and so quenching
is not a problem. For best crystal (grain) structure (ok, so you
only care if you are going to work, hammer, deform the metal-if you
are just soldering and are not going to forge, set, raise, chase,
die-form etc the metal in the next step-who cares if it is
air-cooled?)
Remember- in current lighting-NO VISIBLE GLOW IN TODAY’S LIGHTING.
Indicators: orange flame, Sharpie marker disapears, ivory soap turns
black, flux melts (then you have to get rid of the flux), bamboo
skewer leaves a mark like charcoal)
http://www.ganoksin.com/orchid/archive/9801/msg00596.htm
For gold alloys (except nickel white) Quench immediately upon
annealing (orange flame)
Copper, sterling, bronze, nickel silver, Quench immediately upon
annealing. (note see the articles on argentium for details.
http://www.argentiumsilver.info/index.php/questions-answers)
Brass: No glow, and it is okay to wait a bit before quenching, brass
has odd crystal structures as it cools, and a little wait can help.
Steel: heat till glowing orange and cool as slowly as possible.
(heap with kitty litter, leave in really hot kiln, turn it off, come
back hours later)
Platinum: heat it glowing bright orange, and maintain at this
temperature for 30 seconds for every square inch of material, then
air cool.
Aluminum: orange flame, bamboo skewer looks like drawing with
charcoal, sharpie marker disapears.
In other words, for most of the materials we work with:
NO glow in normal lighting, watch for the orange flame.
Quench immediately to get the metal to maximum softness.
best
Charles
Thanks Charles.
This is one of the most lucid descriptions of metal annealing I’ve
had the privilege to read.
Judy in Kansas, where it’s another chilly day and my gladiola bulbs will
have to wait a while before they go in the ground!
If you want maximum softness then you quench immediately upon annealing. You never should see a red glow from your metal when annealing (in contemporary lighting). Any air cooling beyond actually hardens your metal (anything containing copper, all copper alloys, sterling, most gold alloys).
This is just not the case for the vast majority of copper alloys.
For reference the copper alloys that are considered to be heat
treatable (that care how fast you cool them from elevated
temperatures and or show precipitation or spinodal hardening with
heat treatment) are copper-zirconium, copper-beryllium,
copper-chromium and copper- aluminum and copper-zinc alloys with over
40% zinc (of which the only commercial alloy is muntz metal
Cu60-Zn40). ASM materials handbook Volume 4 covers heat treating
copper alloys and is available in most college libraries that have an
engineering department if anyone wants to look it up.
As studio metalsmiths it is highly unlikely you will ever get your
hands on one of the above alloys. They are industrial products and
unless you get some from a scrap dealer you would have to buy a full
sheet or more to purchase any. A full sheet is somewhere between 2-4
feet wide and 8-10 feet long.
In regards to the majority of gold and silver alloys with some
copper content your observations are absolutely right.
James Binnion
James Binnion Metal Arts
Hi Jim,
Thanks for the correction. Does the lack of silver in the copper, or
its alloy mean that oxygen does not penetrate the material?
I had understood that much increased hardness from overheating or
slow cooling came from copper oxides being formed (in the alloy),
migrating to the grain boundaries, increasing grain size, all
contributing to an increase in hardness?
best
Charles
Hi Charles,
Does the lack of silver in the copper, or its alloy mean that oxygen does not penetrate the material? I had understood that much increased hardness from overheating or slow cooling came from copper oxides being formed (in the alloy), migrating to the grain boundaries, increasing grain size, all contributing to an increase in hardness?
No, the oxygen / oxides will stay on the surface of the alloy in the
relatively brief heating you would do for annealing. The increasing
grain size will make the material softer not harder.
Jim
James Binnion
James Binnion Metal Arts