"Bob La Londe"Â wrote in message news:u7vc95$3pur9$1@dont-email.me...
Most of us know If you dump a ton of oxygen, heat, and fuel on steel it
can burn. Burn may be technically arguable but a very violent reaction resulting in loss of material in its original form results.
Some of us may know that there is some steel loss from reactions at a
lower temperature when using a steel crucible for things like casting aluminum and even some material loss with steel molds used for casting aluminum many times.
...
---------------------
Steel wool burns.
Steel's tempering colors result from oxidation. https://www.servicesteel.org/resources/steel-tempering-colors
As you can see it starts to oxidize below the melting point of lead.
Above 700F the oxidation layer becomes too thick to show a sub-micron interference effect. A cast iron exhaust manifold shows the result of
being heated for a long time. I had to replace my catalytic converter at
80k miles because there was barely enough of the rear flange left to
retain the bolts. The joint had loosened and become noisy.
The blacksmith told me to temper the quench hardened froe blade I made
from a leaf spring at ~350F for an hour, twice, and the high areas I had ground down became faintly yellow from incipient oxidation.
"Bob La Londe"Â wrote in message news:u83vsa$hvpc$1@dont-email.me...
I absolutely believe what I was taught, that steel burns.
[[[ Pinch off a bit of steel wool and light it. When forging if the
steel is yellow hot and gets into the air stream it can burn and spark. ]]]
That
reactiveness of steel premise was originally shared with a tackle making group which tends to be more "craftsy" than technical. Sometimes its
easier to allow for some grudging disagreement than to parrot "facts."
Of course its obvious that steel(iron alloys) becomes more reactive at temperatures as low as molten lead. If for no other reason than an old gunsmith's trick for tempering flat springs (simple carbon spring
steels) is to dunk them in molten lead until they change color. That's
more than twice the temperature than knife makers tend to temper knife
steel, but a much faster temper. (seconds)
"Bob La Londe"Â wrote in message news:u7vc95$3pur9$1@dont-email.me...
Most of us know If you dump a ton of oxygen, heat, and fuel on steel it
can burn. Burn may be technically arguable but a very violent reaction resulting in loss of material in its original form results.
Some of us may know that there is some steel loss from reactions at a
lower temperature when using a steel crucible for things like casting aluminum and even some material loss with steel molds used for casting aluminum many times.
...
---------------------
Steel wool burns.
Steel's tempering colors result from oxidation. https://www.servicesteel.org/resources/steel-tempering-colors
As you can see it starts to oxidize below the melting point of lead.
Above 700F the oxidation layer becomes too thick to show a sub-micron interference effect. A cast iron exhaust manifold shows the result of
being heated for a long time. I had to replace my catalytic converter
at 80k miles because there was barely enough of the rear flange left
to retain the bolts. The joint had loosened and become noisy.
The blacksmith told me to temper the quench hardened froe blade I made
from a leaf spring at ~350F for an hour, twice, and the high areas I
had ground down became faintly yellow from incipient oxidation.
"Bob La Londe"Â wrote in message news:u84v2q$lce4$1@dont-email.me...
That of course leads me to wonder then why steel baking in the southern Arizona Sun will get hot enough to harm you if you pick it up and hold
it for very long, but just develops a light surface rust and lasts for decades. LOL.
Bob La Londe
-------------------
As a general rule, the rate of a chemical reaction doubles with a
temperature rise of 10 degrees C (18F). I mentioned that 2 hours at 350F
gave a barely visible yellow tinge to bare spring steel. The jump from
150F to 350F is more than 10 such doublings, or 1000 times faster. Steel
can oxidize in several ways (oxidation states) under different
conditions to give red, brown, yellow->purple or black oxide coatings.
Around room temperature the overall energy level is low so rust forms preferentially at irregularities with slightly higher energy, hot steel
has enough overall energy to overwhelm the slight differences and it
oxidizes more evenly, for example mill scale and temper color.
That's a vast oversimplification of the complex subject of chemical thermodynamics.
https://en.wikipedia.org/wiki/Arrhenius_equation
"With this equation it can be roughly estimated that the rate of
reaction increases by a factor of about 2 or 3 for every 10°C rise in temperature."
Thermodynamics can be hard to understand. 200 years ago the best minds believed that heat was an invisible fluid
that could be squeezed out of the steel by cutting or hammering it. The concept that heat and temperature were the kinetic energy of molecular
motion took a while to be accepted, and longer to be well understood. Chemistry is an example of pure reason utterly failing to discover the
truth although it had succeeded for math and physics. https://en.wikipedia.org/wiki/Phlogiston_theory
Thermodynamics can be hard to understand. 200 years ago the best minds believed that heat was an invisible fluid
"Bob La Londe" wrote in message news:u86ojc$vrtr$1@dont-email.me...
On 7/5/2023 8:14 PM, Jim Wilkins wrote:
Thermodynamics can be hard to understand. 200 years ago the best
minds believed that heat was an invisible fluid
And while its totally wrong its still a good analogy for getting the
point across. Its not just angry punk rockers in a mosh pit. Its a
volume of angry punk rockers in a mosh pit. Not to technical people who
will stop listening and start trashing you to show how smart/educated
they are the instant you use an analogy so they can tell you how wrong
you are. Its good for practical people who need a feel of how the a
large volume of a substance at a particular temperature has more heat to manage than a small volume of that substance at the exact same
temperature. Its not just angry punkers or the level of their anger.
Its about a whole bunch of angry punkers.
People sometimes struggle with heat management in injection molding
because they can't understand why their skinny rubber worm comes out
fine, but their thick heavy swimbait dents or pulls air. The people I
am dealing with are often not technical experts, but sometimes they are
or are becoming practical experts.
Think of heat as having volume. The more volume there is, and the less transmission media there is the longer its going to take to drain the
heat away.
Yes I know that's wrong, and if anybody will feel better about
themselves by telling me I am wrong have at it.
----------------------------
Not wrong, actually pretty close to reality. Heat capacity is usually specified by mass, the easily determined weight of material, but in
fact it's nearly constant per atom so lighter elements have higher
specific heats. All metals would have about the same heat capacity per
volume if their atoms were the same size, but they do vary
somewhat. Their heat capacity runs around 2 to 3.5 Joules per cubic centimeter to change the temperature by one Celsius (Kelvin, K)
degree. A Joule is 1 Watt for 1 Second.
https://en.wikipedia.org/wiki/Table_of_specific_heat_capacities
"Generally, the most notable constant parameter is the volumetric heat capacity (at least for solids) which is around the value of 3
megajoule per cubic meter per kelvin:"
Or 3 Joules per cubic centimeter.
The molar heat capacity is for equal numbers (6.02E23) of atoms of
metal or individual molecules of chemicals, for compounds it's larger
because they have more atoms per molecule.
Measuring in cubic centimeters is a historical practice, they are
equal to milliliters.
Thermodynamics can be hard to understand. 200 years ago the best minds believed that heat was an invisible fluid
"Richard Smith" wrote in message news:lysfa08vt2.fsf@void.com...
"Jim Wilkins" <muratlanne@gmail.com> writes:
...
Yes, the "Molar Heat Capacity"; the heat capacity for a certain
reference number of atoms. Is almost identical across metals.
I've seen that at least approximately across a few common metals.
--------------------------
Which tends to support the belief that heat is a separate undetectable
fluid that infiltrates the volume of the metal. They weren't too far
off since conduction band electrons do just that.
Which tends to support the belief that heat is a separate undetectable
fluid that infiltrates the volume of the metal. They weren't too far
off since conduction band electrons do just that.
"Bob La Londe"Â wrote in message news:u86ojc$vrtr$1@dont-email.me...
People sometimes struggle with heat management in injection molding
because they can't understand why their skinny rubber worm comes out
fine, but their thick heavy swimbait dents or pulls air. The people I
am dealing with are often not technical experts, but sometimes they are
or are becoming practical experts.
-----------------------
I've known about copes and drags and core prints and riddles and sprues
and runners and vents and shrinkage voids since I was 5, watching the
foundry workers sand-cast aluminum and describe the process to me. When
I was apprenticing as a machinery designer I looked at casting design
again and noticed that the descriptions assumed no scientific education, which I had plenty of by then. They gave rules of thumb...
On 7/5/2023 8:57 AM, Jim Wilkins wrote:
"Bob La Londe" wrote in message news:u83vsa$hvpc$1@dont-email.me...
I absolutely believe what I was taught, that steel burns.
[[[ Pinch off a bit of steel wool and light it. When forging if the
steel is yellow hot and gets into the air stream it can burn and spark. ]]] >>
That
reactiveness of steel premise was originally shared with a tackle making
group which tends to be more "craftsy" than technical. Sometimes its
easier to allow for some grudging disagreement than to parrot "facts."
Of course its obvious that steel(iron alloys) becomes more reactive at
temperatures as low as molten lead. If for no other reason than an old
gunsmith's trick for tempering flat springs (simple carbon spring
steels) is to dunk them in molten lead until they change color. That's
more than twice the temperature than knife makers tend to temper knife
steel, but a much faster temper. (seconds)
That of course leads me to wonder then why steel baking in the southern >Arizona Sun will get hot enough to harm you if you pick it up and hold
it for very long, but just develops a light surface rust and lasts for >decades. LOL.
We joke about it developing its light coating of protective rust. Okay
maybe two of us make that joke.
Bob La Londe <none@none.com99> on Wed, 5 Jul 2023 16:41:13 -0700 typed
in rec.crafts.metalworking the following:
On 7/5/2023 8:57 AM, Jim Wilkins wrote:
"Bob La Londe"Â wrote in message news:u83vsa$hvpc$1@dont-email.me...
I absolutely believe what I was taught, that steel burns.
[[[ Pinch off a bit of steel wool and light it. When forging if the
steel is yellow hot and gets into the air stream it can burn and spark. ]]] >>>
That
reactiveness of steel premise was originally shared with a tackle making >>> group which tends to be more "craftsy" than technical. Sometimes its
easier to allow for some grudging disagreement than to parrot "facts."
Of course its obvious that steel(iron alloys) becomes more reactive at
temperatures as low as molten lead. If for no other reason than an old >>> gunsmith's trick for tempering flat springs (simple carbon spring
steels) is to dunk them in molten lead until they change color. That's >>> more than twice the temperature than knife makers tend to temper knife
steel, but a much faster temper. (seconds)
That of course leads me to wonder then why steel baking in the southern
Arizona Sun will get hot enough to harm you if you pick it up and hold
it for very long, but just develops a light surface rust and lasts for
decades. LOL.
Local Humidity. There's not really enough water in the air to do
more that oxidize the top later.
We joke about it developing its light coating of protective rust. Okay
maybe two of us make that joke.
And then there is the stuff which just rust "a little bit" then
stops. Used in some decorative pieces.
Bob La Londe <none@none.com99> on Wed, 5 Jul 2023 16:41:13 -0700 typed
in rec.crafts.metalworking the following:
We joke about it developing its light coating of protective rust. Okay
maybe two of us make that joke.
And then there is the stuff which just rust "a little bit" then
stops. Used in some decorative pieces.
pyotr filipivich <phamp@mindspring.com> writes:Then there is Cor-ten weathering steel used in bridge pier nosings.
Bob La Londe <none@none.com99> on Wed, 5 Jul 2023 16:41:13 -0700 typed
in rec.crafts.metalworking the following:
We joke about it developing its light coating of protective rust. Okay
maybe two of us make that joke.
And then there is the stuff which just rust "a little bit" then
stops. Used in some decorative pieces.
Yes. The welded sculpture is rusty-brown but otherwise fine decades
later. OTOH, the stone plinth, surrounding walkways and anything open
to run-off rain water is permanently stained a similar brown. There
was much flap about a public sculpture at Dalhousie University in
Halifax years ago.
Um, well, not in the Arizona desert perhaps. Nova Scotia is very
unline the Arizona desert.
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