greetings o wise ones
i have a question about the different media used for quenching. as i
sit here in the evenings i read a lot. haveing read a few books on
blacksmithing and noticed a difference. when discussing quenchants
they all list oil as the slowest /least harsh, some then go to water
others to brine, with the harshest flipping the water and brine. what
is the consensus here as to order of severity of quench media? air -
oil - water - brine or is it air - oil - brine - water.
Alright so lets say that a higher boiling point has a slower cooling
factor. That is what we're saying right? So on quote from Alexander
Weyger's book The Complete Blacksmith, he lists water having a boiling point
of 212 F, Brine at 226 F and Oil at 290 F. His claim is that because of
this water is the fastest (and harshest). Makes sense to me but is it true?
Seems like everybody I've heard from in the groups and forums believes it's
the other way around for water and brine. Don't have a particular favorite
here myself but I'd like to get straight answer on this one ;-)
Granted there are offsets to the boiling points since water boils at
different temperatures depending on the altitude (air pressure) but I would
think the same holds true for brine and maybe oil too? Then there are a
variety of oils in use as a quenching medium so not all oils will work the
same (as other oils).
Now other sources I've read (think it was Metallurgy Theory and Practice
by Dell K. Allen) make the statement that when the quench boils it actually
creates an insulating heat shield till the vapor blows off and so would cool
less efficiently once that happens. Hey, I'm confused and thats after
reading the work of the "experts". Might just be me though...
Pretty much all competent sources agree on brine being the fastest
quench. As for why, think not "boiling point", think "heat capacity", or
"specific heat". It takes more heat to heat up the same amount of brine
rather than water. More heat for water than oil. Believe in boiling
points? Grab a thermos full of liquid nitrogen and try to get a good
quench in it - it's not how cold it is, it's how fast it takes the heat
Just to add to the confusion I have a book ("what steel shall I use?")
that makes a distinction about what temperature the quench material
needs to be -- they talk about experiments involving quenching
low-carbon steels in chilled brine, and you can certainly chill brine
down to a lower temperature than plain old water.
And yes, the boiling point of a liquid is determined by the air pressure
-- you can boil water at room temperature if the pressure is low enough.
Lower the pressure even more and you can boil it until it freezes,
then watch it sublimate away.
I suspect that there are a lot of factors beyond just boiling point that
affect how quickly a quench medium can transport heat away from a piece
-- just off the top of my head the boiling point, thermal capacity,
thermal capacity of the medium _and_ it's vapor would all have an
effect. Two of my references ("What steel should I use" and
"Hardening", or "Hardening Tool Steels" by Linsay press) both make a
point of saying that quench water must be clean and one of them
("Hardening") recommends throwing in a bit of lime if the water gets
soapy -- I can't see how this would affect any of the qualities that
I've dreamed up already, yet obviously _somebody_ believed it made a
Standard disclaimer: This is all just book learning; I've only quenched
one or two pieces in my life, so I can't claim to be anything resembling
an expert (although I have annealed any number of drill bits without
really meaning to :).
Jack Andrews in "New Edge of the Anvil" refutes that statement. he
lists a solution "... to be used with low carbon steels (no hight than
30 points). On a 1018 mild steel a tool quenched, at 1550 F, light
cherry red, in this solution can reach a hardness of 43 to 45 Rochwell
the solution is
5 gal water
5 lbs. salt
32 oz. dawn dishwashing liquid (blue)
8 oz. shaklee basic "I" wetting agent.
If you have any doubts, just wash your hands in GoJo or Ivory soap,
rinse off in your slack tub, then try to quench a piece of hot iron in
After you do, please post the results on this forum.
I don't know what that mess mixed together will do. :/
It might do just as he sez.
My tool steels book makes a big deal out of the "vapor stage" and
how long it hangs on as to the timing and whether it will allow time
for the formation of pearlite.
Tap water is quicker than distilled water and adding just 0.2% NaCl
made water twice as fast. A "2% soap solution" could slow the
distilled water by a factor of 4 which could keep the austenite from
decomposing into almost no martensite under certain conditions.
9% solution of NaCl in water was considered the best overall
concentration. If you insist;) on using NaOH then 3% is suggested
There's a lot more to this, we've barily scratched the surface. ;)
FWIW, I've had real good luck with commercial quenching oil on 1095
at ~1/32" thick. Beats the heck out of water or brine, IME.
Alvin in AZ
I've heard about the "soap problem" before, but never really
investigated it. It's usually put down to some sort of localised
foaming problem around the hot metal and a particularly dense layer of
steam bubbles. As any text on boilers will tell you, conduction
through the metal firebox and the water itself is quite efficient,
it's the thin gas layers that represent the real barrier to heat, even
though they're so thin.
In this Edge of the Anvil example though, there's a load of wetting
agent added as well as the soap. This may well be there to reduce the
I can't think what the original intention of adding soap in the first
place is though.
I don't know about GoJo, but Ivory soap is _soap_, made from fat and
lye. Dawn dish washing detergent is detergent but not soap; it shares
some qualities of soap, but isn't soap.
Perhaps it is specifically soap that causes the problem, or a class of
detergents to which soap belongs, and not all detergents?
This would be a good science fair project if anyone has a 12-year old kid...
snipped-for-privacy@XX.com wrote in news:crmmgu$coh$ firstname.lastname@example.org:
I have a feeling it could be olive oil or some type of citrus oil, both
On the subject that started this thread about the soap in the quench,
I once had a lady offer to buy some of my quench water right out of the
barrel at a show..She said her grandmother, and great grandmother both
cured everything by rubbing the water from a blacksmith's quench tank, go
figure...Heck if I'd known that to be true, well nevermind..
This is commonly known as Super Quench. It works very nicely on medium
or lower carbon steel. Tool steel, properly hardened and tempered is
better, but you can get "mild" steel in a much larger variety of shapes.
Here is an email I saved from TheForge. I save many of Hochewa's posts.
Quenchants are to extract heat from the work piece at somewhat of a controlled
The traditionally meanest, fastest, ugliest quench was sodium hydroxide (lye)
in water to the tune of about 10% by weight. Lye is dangerous as it will chew
on your skin, eyes and lungs.
The action of the sodium is reportedly to reduce the solubility of air in the
water. Less air, more water better quench.
The action of the salt is to deposit itself on the work piece as the water
evaporates around the work. The resulting steam blanket is a poor quench
medium. The salt that precipitates onto the surface has some water of
hydration in it. As it heats, it turns to steam rapidly (I want to say
explosively here but it is not an explosion). This burst of steam breaks down
the steam blanket surrounding the work and fresh quench is brought to the
surface. The process repeats itself until the work is below 212*F. This is
the sizzle that you hear. The formation of steam on the surface of the work
extracts a most of the heat. The water does not do much until the work is
cool enough that you are not making steam. Then the water cools by conduction.
Common salt in water to the tune of 10% by weight works exactly the same way,
almost as well and is a lot safer. The old timers say the brine should be
strong enough to float a potato. More salt is not better.
Plain water is not a good quenchant as the chemistry of it is variable. Just
imagine what has lived or died or fallen into your slack tub.
MIneral oils can be had in a variety of quench rates. Synthetic quenchants
are glycol based and can mirror the mineral oils without the flamability
worrys. Motor oils are usually too thick to be effective but they can be used
in a pinch.
Gunter's Super Quench is an attempt to maximize the quench rate without the
hazards of lye. The principles are the same. The major difference is that
the SQ contains surfactants and detergents which are wetting agents. It still
contains water and salt. The wetting agents probably do the most good as the
work cools to below the flash point of water.
Given all of the above, why do you have to worry about quench rates?
A full explanation of a TTT-Curve is beyond my patience at this point in time.
A brief summary follows:
The ttt curve is shaped like a C. The y axis is temperature and the x axis is
time. The nose of the C is at or about 1200*f or so. The distance between
the y axis at t=0 and the nose of the curve is determined by the alloy content
of the work. This also determines the quench. If you go through the nose of
the curve you make pearlite. Miss the nose and you have a shot at martensite.
For a 1% plain carbon steel like W-1, the distance between the nose of the
curve and the y axis is about 1-2 seconds. This means that you must take the
work from 1575*F of so to 1200*F in less than 2 seconds. This is why you use
brine and this is why it only hardens to a limited depth. For A-2 this time
is about 2-3 hours. A-2 is air-hardening. It also hardens all the way
Hardening does not occur until you cool the piece to around 400*F. But then
this is another story.....