dry ice cold treatment

scott.livesey

scott.livesey

Dealer - Purveyor
hi,
i am going to try some AEB-L or 13C26 both of which recommend cooling to -95F. dry ice will do this, the question is which liquid? i really don't want to mess with acetone, nasty stuff to breath, fire hazard. has anyone tried alcohol? was thinking Everclear, which is 95% ethanol, should work without the hazards of acetone. might even make an interesting drink when done.
 
I've always used denatured alcohol. It's a lot cheaper than everclear. A gallon is less than $20 at Lowes, Home Depot, etc.. You'll find it in the paint section right by the acetone, mineral spirits, etc. Denatured alcohol is grain alcohol with poison added to make it unfit for human consumption, that way it doesn't have to be taxed like liquor.
 
I always wonder why everyone is so opposed to acetone? At -95 degrees there aren't any fumes to breath. There are some data tables out that show the temps you can reach with various solvents and dry ice. If I remember correctly, acetone can reach that temp easily, a lot of those others are borderline. I used it on 14c28n, verified the temp with thermocouple, worked great. After all the dry ice evaporated I poured it back into the can, good as new. What's so bad about acetone?
 
Anthony, Since I've worked with acetone for many years being careful about fire hazard is 2nd nature when dealing with acetone. The fear of fire is why I normally hear concerns about use of acetone with dry ice. As Darrin says, denatured alcohol works just fine. BTW, don't try plain old rubbing alcohol - it will just turn to mush with dry ice. I wonder if acetone would even burn at -95ºF? doubtful?

edit several days later: Just to clarify here, when I'm working with acetone I'm ALWAYS outside in open air. NEVER inside- just don't like the smell of that stuff. These days I even wear rubber gloves - not like in the old days when we washed our hands with acetone.

Ken H>
 
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When you're ready to go with that AEB-L, Scott, skip the snap temper. From what I am hearing, AEB-L gets best performance if the snap is skipped. As a friend of mine said, "Why interrupt Mf?" I mean, I know the answer.....stress relief. But you probably don't need that is the point. Go from quench to cryo, or sub zero here in this case. I would think ALL steels would get their best performance if the snap temper was tossed.
 
I got my recipe for AEB-L from Devin Thomas and he's been using it for many years and probably knows as much about it as any maker around. He was the first one to advise me to go directly from the plates to the freeze. I've made close to 1000 blades using that process and have never had a blade break. AEB-L is VERY stable in H/T. You can take it to within a few thousands of finished dimensions at the edge with no problem.
I've been using it for about 6 years and its good stuff. I'm glad its finally gaining popularity.
 
Self Made Knives said:
I always wonder why everyone is so opposed to acetone? At -95 degrees there aren't any fumes to breath. There are some data tables out that show the temps you can reach with various solvents and dry ice. If I remember correctly, acetone can reach that temp easily, a lot of those others are borderline. I used it on 14c28n, verified the temp with thermocouple, worked great. After all the dry ice evaporated I poured it back into the can, good as new. What's so bad about acetone?
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if i was in an industrial setting and had explosion proof ventilation and all the other controls, i would not have any issues. however, i am sensitive to acetone and related solvents, a good whiff will give me a rest of the day headache similar to a migraine. so i avoid it along with lacquer, some epoxies, oil based wood finish unless i can use it outside. i have found the data tables. acetone and ethanol are with 2 or 3 degrees of each other when mixed with dry ice.
an aside, just thought it would be neat to do my sub-zero quench then use some of the quenchant to make PJs.
not sure the definition of "SnapTemper". when using O1 or 1.2519, i go from quench to 300F oven until the batch is done and last blade has had at least an hour. second temper is usually between 325 and 350F. most of my blades are 3/32" or less and two one hour tempers with cold water quench in between continue to give good results.
 
The idea is that for the martensite trasformation to happen it is required a continuous cooling from Ms to Mf. You can go down with the temperatures fast or slowly, but you are not supposed to invert the gradient otherwise you could stabilize the austenite.
With high alloyed steel as AEB-L, where RA is a major concern (vs. simple medium carbon steels), because have Mf under 0, you really want to do anything to provide a continuos cooling to Mf.
With steels like O1 or 1.2519 you don't need sub zero temperatures (if properly austenitized), just to reach room temperature and then temper. To finish the quench at 300F directly in the oven it is not a good idea (but you probably didn't mean that) because the Mf is not there and it is not even marquenching that way.
 
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Just to clarify Scott, my friend, your statement on "I go from quench to 300F oven", and what Stezann was saying. You shouldn't go from quench into a 300F oven WITHOUT the steel reaching at least room temp. The Mf needs to be reached (and that is pretty close to room temp, maybe a 100F or so with O1 and O7) before tempering. Like Stezann said, you probably didn't mean to say to go from quench into a 300F oven without reaching Mf first. Just wanted to clarify and verify!
 
Just to clarify my earlier post, when I'm working with acetone I'm ALWAYS outside in open air. NEVER inside- just don't like the smell of that stuff. These days I even wear rubber gloves - not like in the old days when we washed our hands with acetone.

Ken H>
 
samuraistuart said:
Just to clarify Scott, my friend, your statement on "I go from quench to 300F oven", and what Stezann was saying. You shouldn't go from quench into a 300F oven WITHOUT the steel reaching at least room temp. The Mf needs to be reached (and that is pretty close to room temp, maybe a 100F or so with O1 and O7) before tempering. Like Stezann said, you probably didn't mean to say to go from quench into a 300F oven without reaching Mf first. Just wanted to clarify and verify!
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sorry for confusion. when i said quench, i meant a complete quench, cooled to barehand temperatures. wipe off excess oil, then into oven. and i know i dont need sub-zero for high carbon steel and oil hardened tool steel. main point of asking about ethanol is my shop is inside and acetone is not nice stuff both in flammablility and harm to me.
 
I have been using kerosene with my dry ice with good results. Flammable, but not flash flammable like acetone.
 
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