I read in one of the How-To books that ATS-34 needed to be sub-zero quenched "for a full heat treatment", but I have talked with reputable knife makers about how they treated their steel and they said that they didn't do it and that it wasn't necessary. Does anyone know if the sub-zero quench either necessary, preferable or wasted effort?
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Sub-Zero quench & ATS-34
- Thread starter joelandry
- Start date
Joe: Sub zero treatment will benefit a blade made from virtually any material-some more than others, but all will benefit. There is hard evidence to support this.
With a steel such as ATS34, which is fairly highly alloyed, the Martensite Finish temperature is WAY below RT.
Can you not sub zero heat treat? Sure.
Is it cheaper and easier not to sub-zero treat? Sure
Can you get "the right" Rc hardness without sub zero treatment? Yes.
Will cryogenic treatment enhance the properties and microstructure of the blade, regardless of how it was heat treated? DEFINITELY
One last tip-if the maker says it's cryogenically treated, ask them how it's done-LN2, -120F cold box, or just their ice-cream freezer! The colder the better-LN2 rules! (the freezer barely counts)
RJ Martin
With a steel such as ATS34, which is fairly highly alloyed, the Martensite Finish temperature is WAY below RT.
Can you not sub zero heat treat? Sure.
Is it cheaper and easier not to sub-zero treat? Sure
Can you get "the right" Rc hardness without sub zero treatment? Yes.
Will cryogenic treatment enhance the properties and microstructure of the blade, regardless of how it was heat treated? DEFINITELY
One last tip-if the maker says it's cryogenically treated, ask them how it's done-LN2, -120F cold box, or just their ice-cream freezer! The colder the better-LN2 rules! (the freezer barely counts)
RJ Martin
- Joined
- Jan 22, 1999
- Messages
- 331
I would agree with RJ,
the quench helps set all the elements. It can be done without, but I'll take mine frozen.
Jeff Hubbard
Quality Supervisor
Buck Knives
the quench helps set all the elements. It can be done without, but I'll take mine frozen.
Jeff Hubbard
Quality Supervisor
Buck Knives
- Joined
- Oct 7, 1998
- Messages
- 1,838
Gentlemen; your positions are such that I tend to accept what you say as truth. Mr. Martin, particularly, as you are a materials engineer.
However, there are many differing opinions regarding this subject, and some knowledgable posters have stated unequivocally that cryo has no benefit at all.
Would you gentlemen be kind enough to publish the data, or at least post where these data can be found, that support your position.
Frankly, I had written cryo off as akin to snake oil (the stuff salesmen in the 1800's sold, not the high tech lube marketed by some pistolsmith [Wilsons??]). I was surprised at your postings.
If the stuff works, this is going to be just one more thing for Dr. Walt to have done to his incredibly vast, pricey knife collection. Sigh. It's a dirty job, keeping up with the latest tech, but someone has to do it.
Mr. Martin; if N2 rules, and the others drool, why not use liquid He?? Heck, they created a Bose-Einstein condensate a few years ago, that was stable for an astonishing 10 seconds. This means that absolute zero is atainable; why stop several degrees K short?? Thank you for your consideration and time. Walt
However, there are many differing opinions regarding this subject, and some knowledgable posters have stated unequivocally that cryo has no benefit at all.
Would you gentlemen be kind enough to publish the data, or at least post where these data can be found, that support your position.
Frankly, I had written cryo off as akin to snake oil (the stuff salesmen in the 1800's sold, not the high tech lube marketed by some pistolsmith [Wilsons??]). I was surprised at your postings.
If the stuff works, this is going to be just one more thing for Dr. Walt to have done to his incredibly vast, pricey knife collection. Sigh. It's a dirty job, keeping up with the latest tech, but someone has to do it.
Mr. Martin; if N2 rules, and the others drool, why not use liquid He?? Heck, they created a Bose-Einstein condensate a few years ago, that was stable for an astonishing 10 seconds. This means that absolute zero is atainable; why stop several degrees K short?? Thank you for your consideration and time. Walt
- Joined
- Apr 19, 1999
- Messages
- 3,560
joelandry
I first became aware of the cryo treatment process back in the 60's through an article in Popular Science when the benefits of cryo treating were just being explored. The way it was explained then was that the steel during heat treatment is heated until the crystal structure was destroyed then the steel was allowed to recrystallize around the free carbon atoms in the alloy thus creating carbon centered crystals, carbides.
Carbides are the very wear resistant crystals that enhance edge holding in cutting tools and the higher percentage carbides in the tool steel the better wear resistance. During the cooling period the recrystallization around the carbon atoms was noticed to take place right down to room temperature where it stopped.
Some bright engineer noticed that not all of the free carbon in the alloy had converted to carbide crystals. Since the recrystallization stopped when the steel reached room temperature the obvious question was "What would happen if room temperature was lower?" closely followed by "How low can we go?"
The first tests were carried out in a freezer and a small improvement in cutting life was observed. The next tests were in
Liquid Nitrogen and very significant improvements were noticed. The first tests were done on drill bits. Representative samples were taken from production runs of drill bits and split into two lots. The firstlot was frozen in liquid nitrogen and the other lot was not. During drilling tests the frozen lot outperformed the control lot by 3 to5 times. Significant!
My heat treater claims a 98% conversion rate of free carbon to carbide crystal structures.
I cannot in all fairness put a knife on the table unless it is the best that I can make it and cryo treatment is part of the process necessary to deliver that knife.
This process works with all carbon bearing steels in the same way.
Other materials benefit from cryo treatment because of the tendancy to form more stable crystal structures in the metal. High precision aluminum machinists use cryo treated raw stock for machining items where tolerances are extremely close because it is so stable.
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george
I first became aware of the cryo treatment process back in the 60's through an article in Popular Science when the benefits of cryo treating were just being explored. The way it was explained then was that the steel during heat treatment is heated until the crystal structure was destroyed then the steel was allowed to recrystallize around the free carbon atoms in the alloy thus creating carbon centered crystals, carbides.
Carbides are the very wear resistant crystals that enhance edge holding in cutting tools and the higher percentage carbides in the tool steel the better wear resistance. During the cooling period the recrystallization around the carbon atoms was noticed to take place right down to room temperature where it stopped.
Some bright engineer noticed that not all of the free carbon in the alloy had converted to carbide crystals. Since the recrystallization stopped when the steel reached room temperature the obvious question was "What would happen if room temperature was lower?" closely followed by "How low can we go?"
The first tests were carried out in a freezer and a small improvement in cutting life was observed. The next tests were in
Liquid Nitrogen and very significant improvements were noticed. The first tests were done on drill bits. Representative samples were taken from production runs of drill bits and split into two lots. The firstlot was frozen in liquid nitrogen and the other lot was not. During drilling tests the frozen lot outperformed the control lot by 3 to5 times. Significant!
My heat treater claims a 98% conversion rate of free carbon to carbide crystal structures.
I cannot in all fairness put a knife on the table unless it is the best that I can make it and cryo treatment is part of the process necessary to deliver that knife.
This process works with all carbon bearing steels in the same way.
Other materials benefit from cryo treatment because of the tendancy to form more stable crystal structures in the metal. High precision aluminum machinists use cryo treated raw stock for machining items where tolerances are extremely close because it is so stable.
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george
- Joined
- Apr 7, 1999
- Messages
- 74
It seems that most guys who say sub-zero quenching is useless either haven't tested blades treated this way, or don't want to spend the extra time and money it takes to treat their blades in this manner. But despite the cynics, science and real world experience show that is works.
When I first became interested in knifemaking, I had the very good fortune of obtaining a temporary position at a heat treatment facility. I spent 5 months learning the particulars of hardening, tempering and testing various hardness levels of many types of steel. The business was fairly small (12 employees), and the owner was a tight wad. Despite all of this, he spent a huge sum of money on a sub-zero quench set-up. After months of research and several industry conferences/seminars, he was convinced that cryogenics was vital to improving the quality of his services.
He just couldn't refute the overwhelming scientific and industrial evidence about the positive effect sub-zero treatment has on all types of tool and high carbon steels. Besides, all of his customers were requesting it. The business' reputation was based on their quality work (their prices weren't cheap, and turn-around was pretty slow), and he wanted to make sure he could continue to provide the best services around. There is no way this guy would have forked out big time money on a process that was not going to greatly improve the quality of the steel he was handling.
Sure, you can make a very good knife using traditional heat treating methods. But you will increase the performance of that knife significantly by adding a proper sub-zero quench.
The evidence is there if people are willing to look.
When I first became interested in knifemaking, I had the very good fortune of obtaining a temporary position at a heat treatment facility. I spent 5 months learning the particulars of hardening, tempering and testing various hardness levels of many types of steel. The business was fairly small (12 employees), and the owner was a tight wad. Despite all of this, he spent a huge sum of money on a sub-zero quench set-up. After months of research and several industry conferences/seminars, he was convinced that cryogenics was vital to improving the quality of his services.
He just couldn't refute the overwhelming scientific and industrial evidence about the positive effect sub-zero treatment has on all types of tool and high carbon steels. Besides, all of his customers were requesting it. The business' reputation was based on their quality work (their prices weren't cheap, and turn-around was pretty slow), and he wanted to make sure he could continue to provide the best services around. There is no way this guy would have forked out big time money on a process that was not going to greatly improve the quality of the steel he was handling.
Sure, you can make a very good knife using traditional heat treating methods. But you will increase the performance of that knife significantly by adding a proper sub-zero quench.
The evidence is there if people are willing to look.
- Joined
- Mar 27, 1999
- Messages
- 162
R.J. what is the LN2, 120F. cold box you were talking about? Thanks
Guys: If you'd like to read a 3 part article on Cryogenics, go to www.heattreatingonline and check out the "articles" section. This is basically the cryogenics chapter from Bill Bryson's book "heat treatment, selection and application of tool steels", published by hanser Gardener. Fot the $30, best book you can own on heat treatment, IMHO.
Bill is soon to have a book dedicated to Cryogenics, also published by Hanser Gardner, and I will have one ASAP when it's available.
You can also search "cryogenics" and see the sites of 300 Below, etc. Very informative.
You should note that cryogenics is used in automotibe racing-entire engines are treated, for musical instruments, and even panty hose. Welders have treated their welds with dry ice since the 40's, I believe-not knowing why it worked, but seeing the benefits in stress relief.
As to Liquid gasses colder than Nitrogen, they might work better, but, you might never be able to measure the difference, either. You need to remember just how slowly things happen at minus 300!! My understanding is that you can reach about 99.9 % of Austenite to Martensite conversion with LN2, so, you can pretty well stop there. But, it is a good point, and I will contact Bill and ask him. Liquid Helium is an order of magnitude more expensive to procure and store than LN2, so, that's a factor as well.
It's interesting to note, that, even since I was in College (graduated 1984), that MUCH has changed WRT this area. I have testbooks from the 50's that are now totally incorrect, and quite amusing. Certainly, I don't want to present myself as an authority here, either, because I don't do metallurgy as my career. BUT, I do know what works, and have personally experienced the remarkable effects of cryogenic treatment on tool steels. All my drill bits, end mills, carbide tools, etc get treated in my Dewars flask of LN2, and they last longer and cut better.
The more sophisticated the steel, the more you NEED to cryo treatment. And remember, you still need to know your stuff when it comes to the heat treatment itself.
Hope this helped!
RJ Martin
Bill is soon to have a book dedicated to Cryogenics, also published by Hanser Gardner, and I will have one ASAP when it's available.
You can also search "cryogenics" and see the sites of 300 Below, etc. Very informative.
You should note that cryogenics is used in automotibe racing-entire engines are treated, for musical instruments, and even panty hose. Welders have treated their welds with dry ice since the 40's, I believe-not knowing why it worked, but seeing the benefits in stress relief.
As to Liquid gasses colder than Nitrogen, they might work better, but, you might never be able to measure the difference, either. You need to remember just how slowly things happen at minus 300!! My understanding is that you can reach about 99.9 % of Austenite to Martensite conversion with LN2, so, you can pretty well stop there. But, it is a good point, and I will contact Bill and ask him. Liquid Helium is an order of magnitude more expensive to procure and store than LN2, so, that's a factor as well.
It's interesting to note, that, even since I was in College (graduated 1984), that MUCH has changed WRT this area. I have testbooks from the 50's that are now totally incorrect, and quite amusing. Certainly, I don't want to present myself as an authority here, either, because I don't do metallurgy as my career. BUT, I do know what works, and have personally experienced the remarkable effects of cryogenic treatment on tool steels. All my drill bits, end mills, carbide tools, etc get treated in my Dewars flask of LN2, and they last longer and cut better.
The more sophisticated the steel, the more you NEED to cryo treatment. And remember, you still need to know your stuff when it comes to the heat treatment itself.
Hope this helped!
RJ Martin
Guys: Missed a question. LN2 is Liquid Nitrogen, minus 300 F. Commercial heat treaters sometimes have "cold boxes", which are freezers that generally run to minus 120F. Your deep freeze in your basement might reach 0F.
Just checked Bill Bryson's book. Really good heat treatment can reach 95 or 96% martensite, but, more likely you'll get 50-60% from mass produced items like drill bits, etc. Cryo, as I indicated, can get you to 100%, or so close you can call it 100%.
When you look at the data on sites like 300 below, you'll see instances of 800% increases in wear resistance, for example. You can bet that the original tools weren't perfectly heat treated.
What cryo also gives you is refined grain size (translate: Increased toughness, increased wear resistance)
RJ Martin
Just checked Bill Bryson's book. Really good heat treatment can reach 95 or 96% martensite, but, more likely you'll get 50-60% from mass produced items like drill bits, etc. Cryo, as I indicated, can get you to 100%, or so close you can call it 100%.
When you look at the data on sites like 300 below, you'll see instances of 800% increases in wear resistance, for example. You can bet that the original tools weren't perfectly heat treated.
What cryo also gives you is refined grain size (translate: Increased toughness, increased wear resistance)
RJ Martin
R
Ruppe
I have notice a distinct difference identical ly ground blades where I used a cold cycle of acetone and dry ice on one and not the other. There is no question in my mind the the cold cycle makes for a more durable blade.
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Ron Ruppé
www.ruppe.com/Knives/index.htm
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Ron Ruppé
www.ruppe.com/Knives/index.htm
Cliff Stamp
BANNED
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- 17,562
Walt. there are a number of reasons why it might not be practical to work with Helium as a coolant. First off it is both very unstable in liquid form and very expensive compared to Nitrogen (which is pennies per litre to condense). Because the boiling point of Helium is so low, it is much more difficult to work with liquid Helium. Helium will not remain a liquid by itself at room temperature (or even much lower) which Nitrogen will. To keep Helium in liquid form you need to keep it insulated with a layer of liquid Nitrogen and it still boils off rapidly. Also as R. J. noted, the temp difference between liquid Nitrogen and liquid Helium, is much smaller than between liquid Nitrogen and room temp so your possible gain is only a modest improvement. Nitrogen has a boiling point of 77 K, Helium is 4 K and room temp is about 300 K. Keep in mind that the improvement relationship could be an exp. damping function which is effectively zero past 77 K. It would be interesting to see exactly what functional form the relationship would take, odds are its not going to be simply linear.
-Cliff
-Cliff
amacks
Gold Member
- Joined
- Oct 13, 1998
- Messages
- 674
One thing I noticed, in David Boye's literature on Dendritic 440C, he mentions that cryo treatment reduces the bite of the blade.
Aaron
ps Walt: A BEC and 0K are very different things, one is simply a group of many atoms behaving as if they were just one, the other is the total cessation of molecular motion. With about 100,000, making a BEC is pretty easy, ataining Abs 0 is pretty much impossible.(it would also stop molecular motion in the steel, not what you want to do if you are trying to change crystaline structure)
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aaronm@cs.brandeis.edu
I like my women like I like my knives: strong, sharp, well-formed and pattern-welded!
Aaron
ps Walt: A BEC and 0K are very different things, one is simply a group of many atoms behaving as if they were just one, the other is the total cessation of molecular motion. With about 100,000, making a BEC is pretty easy, ataining Abs 0 is pretty much impossible.(it would also stop molecular motion in the steel, not what you want to do if you are trying to change crystaline structure)
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aaronm@cs.brandeis.edu
I like my women like I like my knives: strong, sharp, well-formed and pattern-welded!
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- Apr 7, 1999
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- 74
Doea anyone know a website/address of a company that sells nitrogen and containers? Or, what is the best way to obtain them locally?
Cliff Stamp
BANNED
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- 17,562
Fenixforge, contact a local university (physics/chemistry stores dept.) or a local hospital and ask them where they get theirs. The university problably has a condenser of their own.
Concerning, a cryo quench reducing the bite of dendritic steel, is this just the effect of it reducing the grain size?
-Cliff
Concerning, a cryo quench reducing the bite of dendritic steel, is this just the effect of it reducing the grain size?
-Cliff
- Joined
- Oct 7, 1998
- Messages
- 1,838
Er, guys, I was JOKING about liquid He and a Bose Einstein condensate.
I did read in Scientific American about six months ago about the creation of a BEK, and it was a small number of atoms; however, I thought it was a tremendous advance. Remember that Bose and Einstein theorized that this form of matter could exist about 1905, and it has taken this much time to actually produce one.
Besides, how many chances do you have to drop 'Bose Einstein condensate' into a conversation??
For a real laugh, check out the article in Sci Am which covers the BEK story. The apparatus they used looks so absolutely Rube Goldberg that at first I thought it was a joke. It is like something out of a sci-fi movie!
Once more amazed at the erudition of the forumites, I thank you.
(formerly Whacko) Walt
I did read in Scientific American about six months ago about the creation of a BEK, and it was a small number of atoms; however, I thought it was a tremendous advance. Remember that Bose and Einstein theorized that this form of matter could exist about 1905, and it has taken this much time to actually produce one.
Besides, how many chances do you have to drop 'Bose Einstein condensate' into a conversation??
For a real laugh, check out the article in Sci Am which covers the BEK story. The apparatus they used looks so absolutely Rube Goldberg that at first I thought it was a joke. It is like something out of a sci-fi movie!
Once more amazed at the erudition of the forumites, I thank you.
(formerly Whacko) Walt
I started a thread one this on swordforum awhile back and a couple of the smiths got very very angre at me. And when I told them about the article that Tim did, they called him and me stupid some of the stuff they e-mailed me. Plus one of them said it might work with a oil quench or air quench but not a water quench. He said he water quenches everything including Ats-34. and with water quench he gets 100% martensite everytime.
I would like to know if anybody has done much water quenching. From what I have learned the slower the quench and still get it hard is best, less stress
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-Greg Johnson
ICQ#4236341
I would like to know if anybody has done much water quenching. From what I have learned the slower the quench and still get it hard is best, less stress
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-Greg Johnson
ICQ#4236341
amacks
Gold Member
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- Oct 13, 1998
- Messages
- 674
Water quenches ATS-34?! That I'd like to see(from a large distance). I was playing around with forging some old HSS drill pits(prob M2) and water quenching them made them crack, so I have very little faith for a large piece of some high-alloy steel.
Aaron
ps If anyone wants more info on the properties and formation of a BEC, I have text of a few articles, but I can't post them here.
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aaronm@cs.brandeis.edu
I like my women like I like my knives: strong, sharp, well-formed and pattern-welded!
Aaron
ps If anyone wants more info on the properties and formation of a BEC, I have text of a few articles, but I can't post them here.
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aaronm@cs.brandeis.edu
I like my women like I like my knives: strong, sharp, well-formed and pattern-welded!
R
Ruppe
Hitachi is very specific about ATS-34 being a n air quenched steel. Water quenching will crack a number of oil quenching steels. By the way, the "O" in O-1 stands for oil.
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Ron Ruppé
www.ruppe.com/Knives/index.htm
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Ron Ruppé
www.ruppe.com/Knives/index.htm
