Calibrating heat treat furnace

[Polymer Man]

I have never checked the calibration of my heat treat furnace, a small
Lindbergh Blue, so with my last MSC order, I got a chalk stick that is
calibrated to melt at a given temperature. You're supposed to rub it
on a piece of hot steel and see if it is above or below the melt temp
of the stick. It is supposed to be accurate within one percent.

It either melts or doesn't melt. Real simple.

So I got one at the top of the range, 1800, which is close to the
ausentizing for D2. Perfect, same part of the scale.

So I heated up a chunk of 1018 to 1775 and rubbed the stick on it.
Remember, it either melts or doesn't melt. Real simple. Well, mine
vaporized and burst into flames, which wasn't on the list. But it was
kinda pebbly while doing it.

So, to 1800, the melt point. Still pebbly.

To 1815, and, under the mushroom cloud, it appeared to be smearing
before erupting into flames.

Is there a better way to do this?

[Del Cecchi]

Post by Polymer Man
I have never checked the calibration of my heat treat furnace, a small
Lindbergh Blue, so with my last MSC order, I got a chalk stick that is
calibrated to melt at a given temperature. You're supposed to rub it
on a piece of hot steel and see if it is above or below the melt temp
of the stick. It is supposed to be accurate within one percent.
It either melts or doesn't melt. Real simple.
So I got one at the top of the range, 1800, which is close to the
ausentizing for D2. Perfect, same part of the scale.
So I heated up a chunk of 1018 to 1775 and rubbed the stick on it.
Remember, it either melts or doesn't melt. Real simple. Well, mine
vaporized and burst into flames, which wasn't on the list. But it was
kinda pebbly while doing it.
So, to 1800, the melt point. Still pebbly.
To 1815, and, under the mushroom cloud, it appeared to be smearing
before erupting into flames.
Is there a better way to do this?

The ceramics folks have little cones they put in the furnace. In fact,
how about putting a little piece of the crayon in the furnace to see if
it melts. vaporizing and bursting into flames sounds like it might be a
little hot.

del

[MatthewK]

Post by Polymer Man
I got a chalk stick that is
calibrated to melt at a given temperature. You're supposed to rub it
on a piece of hot steel and see if it is above or below the melt temp
of the stick. It is supposed to be accurate within one percent.

This is cool, I just found out about tempilsticks a week or so ago.

Post by Polymer Man
Is there a better way to do this?

If you find out somewhere else, let us know.

matthew
ohio

[a***@XX.com]

Post by MatthewK

I got a chalk stick that is calibrated to melt at a given
temperature. You're supposed to rub it on a piece of hot steel
and see if it is above or below the melt temp of the stick. It
is supposed to be accurate within one percent.

This is cool, I just found out about tempilsticks a week or so
ago.

Is there a better way to do this?

matthew

You said you pulled the metal from the furnace and it still didn't
work, right? :/

My plan is/was to make an electric furnace and use a thermocouple
for heat treating A2.

I have the meter that's calibrated for a Pt/Pt 13%Rh thermocouple
and the thermocouple is the last piece needed. Haven't dared look
into the price of one of those. ;)

We used TempilSticks at work we all thought their brag of accuracy
was total crap "in practice"... I suppose in theory or their lab
it's "spot on"? :) Two 425F sticks side by side on the truck dash
and one would be melted and the other fine, for an example.

Alvin in AZ

[MatthewK]

Post by a***@XX.com
We used TempilSticks at work we all thought their brag of accuracy
was total crap "in practice"... I suppose in theory or their lab
it's "spot on"? :) Two 425F sticks side by side on the truck dash
and one would be melted and the other fine, for an example.
Alvin in AZ

Thats good to know. Been thinking about getting some to help me learn
what the temp range is. I still want to learn by eye, just have to
keep practicing. I thought they would be handy for normalizing. A
metalurgist on Don Fogg's forum was saying that if you normalize 3 times.
First 100 degrees over critical, second 50 degrees over critical, and the
third just at or above. It will produce a finer grain structure than just
doing it by the seat of your pants.

One of Kyle J's posts
http://forums.dfoggknives.com/index.php?showtopic=2487&hl=double+temper

matthew
ohio

[a***@XX.com]

Post by MatthewK
One of Kyle J's posts
http://forums.dfoggknives.com/index.php?showtopic=2487&hl=double+temper
matthew

Loading Image...

That came right out of the same book DonFogg was using. :)

And I have the Kruass book Nichols was using. (and yes it's a
re-write of those great old books by Bain and Grossman that
Nichols likes so much :) Thanks Dennis in No.CA for the book! :)

Cashen got it pretty much staightened out, but it didn't stick. :/
(with all that talking past each other)

A situation like that really needs quick easy editing like usenet
has with it's little >'s in front of the quoted text so specifics
can be addressed one step at a time, making for quick and easy
reading too.

Was it Cashen tho? that had the hardness spots after the second
temper? Easily explained IMO. :)

If you are tempering below 425F then a sustantial part of the
retained austenite can transform to untempered martensite. You'll
have "dead hard" untempered martensite spots. He's working real
hard to find those tho! :)

Krauss goes into detail about why not to do mulitple tempers.

Cold treating directly after the quench will reduce the need for
multiple tempering.

I agree the "3" normallizing steps need careful temperature control.

I couldn't get it to work before... need to try it again... I've
gone down a step or two in the size of my burner heads since I last
tried it. :)

You know, there was a lot(!) of right stuff in there. :)

Even knowing the answer ahead of time made it it tougher than hell
to sort out tho. :/ I feel as tho I didn't either.

It's a mess. :/

I'd be cool to get an answer on the blue brittle stage when quick
tempering times are used instead of the standard 1 hour tempering
times. Time at the blue-brittle stage temperatures has been
talked-at in several places in differnet books but no where
throughly I've seen.

Alvin in AZ

[MatthewK]

Post by a***@XX.com
Cashen got it pretty much staightened out, but it didn't stick. :/
(with all that talking past each other)

I'll have to read it again with that in mind.

Post by a***@XX.com
A situation like that really needs quick easy editing like usenet
has with it's little >'s in front of the quoted text so specifics
can be addressed one step at a time, making for quick and easy
reading too.

Yeah, only usnet people seem to get that. It ticks one of my friends
off...."I have no interest in reading my own words matthew"

Post by a***@XX.com
I agree the "3" normallizing steps need careful temperature control.
I couldn't get it to work before... need to try it again... I've
gone down a step or two in the size of my burner heads since I last
tried it. :)

Yeah, one of the reasons I wanted to give charcoal a try, I figure I'll
have more controll.

Post by a***@XX.com
You know, there was a lot(!) of right stuff in there. :)
Even knowing the answer ahead of time made it it tougher than hell
to sort out tho. :/ I feel as tho I didn't either.
It's a mess. :/

The better stuff I've read is just confirming what you told us. They were
talking about "fields of modulity" or something....basically a lot of old
smiths had a hard time accepting that a hard bar flexes just as much as
soft one. Hardness/stiffness don't go together.

Or a paraphrase of you "A fillet knife made out of an old all-hard hacksaw
blade will be just as flexible as a soft one if you grind it right"
"Flexiblilty is a resut of the blade grind"

I'm even starting to think for myself :), I read in the DF forum archives
about crumbly edges that went away with a hotter temper....their heat
treatings must of sucked. Taps aren't crumbly, I figure if the HT is good
than those edges should of chiped or sheared if abused.

Just had a conversation with a guy that said if I was going to cold treat
low alloy carbon, I minus well go for stainless for a razor. He mentioned
s30v. Always heard that stuff was terrible to heat treat, he also said
blacksmith techniques are will do for stainless...........and I didn't want
a ultra hard edge. I left the heat treating part alone and made a case for
a harder blade.

His heat treating advice....why bother, the ultra hard edge. My thinking
is it will be easier to hone properly and stay that way longer, the burr
can really mess a guy up on straight razors.

matthew
ohio
matthew
ohio

[a***@XX.com]

Post by MatthewK
Yeah, only usnet people seem to get that. It ticks one of my
friends off...."I have no interest in reading my own words
matthew"

LOL :)

Post by MatthewK

Post by a***@XX.com
I couldn't get it to work before... need to try it again... I've
gone down a step or two in the size of my burner heads since I
last tried it. :)

Yeah, one of the reasons I wanted to give charcoal a try, I figure
I'll have more controll.

They have controlled furnaces or they are bullshitting us on their
temperatures.

Post by MatthewK

Post by a***@XX.com
It's a mess. :/

They were talking about "fields of modulity" or something...
matthew
ohio

I don't know what that is. :/

I do know that sources that speak of Mf are old suckers. ;)
Not wrong really, just old.

<snipped old guy story>

Working with rail and around welders I've heard a lot of stuff about
steel. It was soooo cool to read MT&P and finally get the straight
dope on it! :) It was funny how pieces of what was said here and
there, were right and the rest as wrong as it could be.

Not just wording like "the steel crystalizes" when they were really
talking about large grain so big you could see it as crytals. I'm
not picking on that sort of stuff but instead wrong ideas, and ideas
going the wrong direction. ;)

And how one old rail welder, that many run-down, was the closest to
right of all of them. :) Fred French. :) Some of which I prob'ly
never fully understood or there'd be more right about what he said.

Alvin in AZ (retired signalape)
ps- Hi Fred, you ugly old fart! :) (if he google's his name;)

[Del Cecchi]

Post by MatthewK

Post by a***@XX.com
We used TempilSticks at work we all thought their brag of accuracy
was total crap "in practice"... I suppose in theory or their lab
it's "spot on"? :) Two 425F sticks side by side on the truck dash
and one would be melted and the other fine, for an example.
Alvin in AZ

Thats good to know. Been thinking about getting some to help me learn
what the temp range is. I still want to learn by eye, just have to
keep practicing. I thought they would be handy for normalizing. A
metalurgist on Don Fogg's forum was saying that if you normalize 3 times.
First 100 degrees over critical, second 50 degrees over critical, and the
third just at or above. It will produce a finer grain structure than just
doing it by the seat of your pants.
One of Kyle J's posts
http://forums.dfoggknives.com/index.php?showtopic=2487&hl=double+temper
matthew
ohio

ceramic cones? http://www.potterymaking.org/KilnFiringLayout.pdf

[a***@XX.com]

Post by Del Cecchi
ceramic cones? http://www.potterymaking.org/KilnFiringLayout.pdf

Cool chart. :)

Sorry, but cones just won't be accutate enough, the optical or
thermocouple stuff is the only way to go here I'm afraid. :/

The temperature needs to be held within 10F of the target and
for at least a half hour for A2 ...don't know how long for D2.

Alvin in AZ

[Del Cecchi]

Post by a***@XX.com

Post by Del Cecchi
ceramic cones? http://www.potterymaking.org/KilnFiringLayout.pdf

Cool chart. :)
Sorry, but cones just won't be accutate enough, the optical or
thermocouple stuff is the only way to go here I'm afraid. :/
The temperature needs to be held within 10F of the target and
for at least a half hour for A2 ...don't know how long for D2.
Alvin in AZ

What kind of atmosphere? Just regular air? nitrogen, argon, something
reducing?

[Polymer Man]

Post by Del Cecchi
What kind of atmosphere? Just regular air? nitrogen, argon, something
reducing?
--
Del Cecchi
"This post is my own and doesn't necessarily represent IBM's positions,
strategies or opinions."

Is this question directed toward me?

The furnace is electric. I use argon during a heat treat, though it
was off for this test to conserve gas, which ain't cheap. I'm thinking
about going to foil.

The furnace is digitally controlled (meaning not a thermostat), and
uses a thermocouple to measure the temperature. It's cool because it
ramps up to heat in just a few minutes, then throttle's back before
hitting temperature so it doesn't overshoot. The furnaces we had while
I was in school didn't work this way.

My problem is I may be hitting a temperature with great precision, but
lousy accuracy. I've never checked the calibration. Getting a
thermocouple to check it might be informative, but there is already a
thermocouple in there, so wouldn't be any more definitive than what
the control shows. The melty stick turned out to be rather crude. Is
there a handy little trick out there to double check this thing?

[Del Cecchi]

Post by Polymer Man

Post by Del Cecchi
What kind of atmosphere? Just regular air? nitrogen, argon,
something
reducing?
--
Del Cecchi
"This post is my own and doesn't necessarily represent IBM's
positions,
strategies or opinions."

Is this question directed toward me?
The furnace is electric. I use argon during a heat treat, though it
was off for this test to conserve gas, which ain't cheap. I'm thinking
about going to foil.
The furnace is digitally controlled (meaning not a thermostat), and
uses a thermocouple to measure the temperature. It's cool because it
ramps up to heat in just a few minutes, then throttle's back before
hitting temperature so it doesn't overshoot. The furnaces we had while
I was in school didn't work this way.
My problem is I may be hitting a temperature with great precision, but
lousy accuracy. I've never checked the calibration. Getting a
thermocouple to check it might be informative, but there is already a
thermocouple in there, so wouldn't be any more definitive than what
the control shows. The melty stick turned out to be rather crude. Is
there a handy little trick out there to double check this thing?

Actually it was directed at whoever. I was just wondering about heat
treat ovens and how to make one using stuff intended for ceramic kiln,
electric heat. And the question crossed my mind.

A new thermocouple should be accurate since the voltage it puts out is
determined by the materials, so long as the cold junction is handled
correct and any extensions to the cable are made correctly, at least if
what I read was correct.

If you use a different type of thermocouple? Optical pyrometer? check
it with two thermocouples and go with the majority?

del