Sub zero/ temper question

PEU, please be VERY careful using MEK .It's dangerous stuff ! Acetone would be a better choice.
 
Mete, I used MEK once because I ran out of Acetone, I had to do a subzero and googled every solvent I had at hand for the adecuate melting point, MEK worked, now I have a full liter of acetone at my disposal. Thanks for the heads up.


Pablo
 
mete said:
PEU, please be VERY careful using MEK .It's dangerous stuff ! Acetone would be a better choice.
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That's the new solvent in the "better" non-acetone nail polish remover. I laughed and my wife gave me some funny looks.
 
I'm not a biologist...
but it has been my understanding that your body has mechanisms for dealing with acetone because it's a naturally occurring metabolite. So, while it's a pretty nasty solvent, your body can deal with it. MEK is just plain nasty.
 
A gallon can of plain old denatured alcohol from HD or Lowes will work just fine. I stopped using acetone a while back.
 
I love acetone. A little shot in the coffee every morning.....keeps you cleaned out! I may try some denatured alcohol, Stacy! Is that like 80 proof? OK...back to serious stuff. Do any of you guys recall seeing a video of tempering being performed on steel, filmed through a microscope, and as the steel hit 420F (the real-time temperature was given in celcius at the bottom of the screen IIRC) you could actually see some sort of change occurring in the steel? This change did not happen until 420F was reached. It was some time back that I saw the video....but I can't seem to locate it again, and my memory may be off a bit. Ring a bell to anyone? I'll try to find it and linkey.
 
If the change doesn't happen until 420˚F then what good are tempering temps below that?
 
i4Marc said:
If the change doesn't happen until 420˚F then what good are tempering temps below that?
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What you see depends on what kind of microscope. Because that change didn't happen until then, doesn't mean there weren't others that the person running the microscope wasn't interested in seeing. Changes in tempering start at or just below 300 F.
 
Sorry, Me2...it wasn't that one. I4Marc....please don't misunderstand my post. I get what you are saying. That is WHY the video stuck in my head. There was a PHYSICAL change in the structure of the steel that did not happen until 420F was reached. Once 420F hit...you could see it. It was very obvious. Hence my bringing it up. I saw it.....questioned "what in the world is that?" and filed it away as....you don't know enough to ask yet!!!!! I hear you....I totally understand your hesitancy!!! But I do remember it quite well...and it stuck with me. I wish I could find it. I looked and looked right now online....I cannot find it again. Damnitt. Totally frustrating!!!
 
I don't know about steel, but I do see physical changes in some of the young folks around here (Washington state) when 4:20 is reached. PM that is.
 
If it was the micrograph video I remember, it was one of cooling from austenitization. The austenite suddenly converts to martensite around 400F. That has nothing to do with the tempering of brittle martensite ( I now see it called alpha martensite) into tempered martensite ( beta martensite). The martensite is raised to near or slightly above the original transformation point to re-arrange the structure. I agree that a temper below 350F is pretty useless for a knife. 400-500F is the better range for most knife purposes.
 
The video I have in mind may very well be the one Stacy mentioned, which does not have anything to do with tempering. Elementfe...that was hilarious!!! Yep.....420 can make some changes for sure. Colorado is a different state during the late afternoon nowadays!
 
That video shows definite changes still happening below 350˚F. I put up a link to Mr. Bhadeshia's lectures and videos in another thread last night.
 
Seems like I once read that tetragonal martensite starts to convert towards cubic martensite around 300F. *shrug*
 
Bluntcut....that isn't it either! But essentially yes...it was indeed very very similar. It seems as if I remember the degrees were given in celcius, and I had to convert it to F.

Dude....I FOUND IT!!!! So excited now!!!! The temp was given in Kelvin, not C!!!!! Here it is...this is what was scrambled in my brain!!!!....... https://www.youtube.com/watch?v=jlXc82n1ThU
 
I was discussing minimum tempering temps with Brad Stallsmith a few weeks ago and he advised 300 as a minimum for simple steels and 350 for more complex alloys, especially the PM steels.
 
samuraistuart said:
Bluntcut....that isn't it either! But essentially yes...it was indeed very very similar. It seems as if I remember the degrees were given in celcius, and I had to convert it to F.

Dude....I FOUND IT!!!! So excited now!!!! The temp was given in Kelvin, not C!!!!! Here it is...this is what was scrambled in my brain!!!!....... https://www.youtube.com/watch?v=jlXc82n1ThU
Click to expand...

That's a very different steel from what we are used to dealing with. I'm not familiar with it, yet. The processing and transformation characteristics appear to have been developed in the late 90's. The major uses I've found are for car parts, possibly involved in crumple zones, as the properties list 113,000 psi tensile strength coupled with high ductility and energy absorption. They are dual or even triple phase, with ferrite, retained austenite, and possibly bainite.
 
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