cryogenics for the home shop?

Rob, That should be a treat! Wear him out with questions!!:biggrin:
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So IF ramp time is important on giving your blade the chilly-willies.....

What about something like this:

1) cool blade to +40f in fridge. 1hr

2) take to 0 F degrees (house freezer/ chest freezer) 2hrs

3) take to -20 to -30F degrees (commercial restaurant freezer) 2hrs

4)take to -90F degrees (dry ice/antifreeze) 4 hrs

5) take to -230F degrees (liquid nitrogen) 6hrs.

Then reverse the process back to room temp. Then temper immediately.

Would this help IF ramp time is important? Or would it just be metallurgical aerobics?:3:
 
Kevin R. Cashen said:
..... Fortunately I have a heat treating Power Point that is already in Celsius from a talk I did in Quebec last year.:3:
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Oh-oh. We Canadians are a little conflicted. If you ask us the temperature outside, we'll tell you its a balmy 21 degrees. If you ask what temperature to heat treat 154CM at, we'll tell you 1950. So much of our HT information comes from US forums and suppliers, we almost exclusively us Fahrenheit. When I read European spec sheets, I'm always scrambling for my conversion calculator (cause I can never remember whether to add or subtract 32) :15:

A sheet of plywood is still 4 x 8 - gas is sold at the pumps in litres and we talk about mileage in MPG - Imperial Gallon! Hamburger and bacon come in 454g (1 pound) packages. Speed limits are posted for Km/Hr, but we treat them as MPH anyway. :21:

Please adjust your presentation accordingly. :biggrin:


Rob!
 
Smallshop said:
Rob, That should be a treat! Wear him out with questions!!:biggrin:
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So IF ramp time is important on giving your blade the chilly-willies.....

What about something like this:................
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Let us know how that works out for you. :biggrin: ... as an unscientific guess, I suspect you may be overthinking this. There are tens of thousands of knifemakers dunking their blades in LN or Dry Ice solutions. They aren't breaking and they get harder than a woodpecker's lips. Having said that, your ramp idea likely meets the test of "do no harm"..... unless some of the soft stuff starts to stabilize before it gets to useful lows????

Seriously, there are bigger challenges. Buy a pyrometer and place the thermocouple tip in different places in your kiln - front - back - top - bottom - close to coils..... (Tempering temperatures) After changing your underwear, go back to the cold kiln - put the thermocouple right in your blade rack and watch some of the excursions as your kiln climbs up to temperature. In the end, most of this doesn't have much effect on outcome. The excursions are too brief - and the zone temperature will almost equalize on a 2 hour temper.
 
"Let us know how that works out for you.
4.gif
... as an unscientific guess, I suspect you may be overthinking this."

Yeah....probably. But what I'd really like to do is determine that it IS unnecessary and just do what the woodpecker-lip-brigade has been doing all along! set it and forget it.....

The fellow that wrote that first article probably wasn't trying to lead us down a path intentionally. I think some of his unproven speculations made it into that article. Humans are just SOOOOO prone to bias. And I'm a human......

So...The over thinking and cross checking are due to the lack of skepticism I had years ago....which led me to quench my O1 blades in brine at the advise of an expert......sigh. With the result of me getting disgusted and giving up. Surprisingly, some of those blades performed real well....and still do.
 
my comments were MHO based on where I am with making blades. my approach is to simplify as much as possible, and reduce the number of variables to a manageable number. steel from same maker, same furnace, oven and quench when doing HT, same brand name belts when grinding.
had similar discussion about normalizing, if I am working thin(3/32" or less), do not normalize, watch my temps, and get post temper hardness of Rc63-64, why should i add more steps to the process?
i am going outside the box for a trial though. the CCT for O1(1.2510) and O2(1.2842) makes them candidates for air quenching in thin(3/32 or less) blades. I am going to make a few samples. the thought is a wrapped blade with air cooling should have little or no scale or decarb. will have to see what happens. could reduce grinding time per blade a bunch, and also reduce belt usage.($$$)
 
Scott, I get what you are saying and agree with the simplicity part. The only reason I'm chasing down the Cryogenic stuff is I want to use a stainless for a project I'm on. Most of these super stainless steels advise a cryogenic treatment between HT and temper. If it really didn't do anything I would ditch the idea. As of right now I think that enough guys have seen good results that maybe they can't quantify but they can observe.

The reason I tore up on that article was just that I saw what I thought could be a strong bias. I did not feel the writer was being sneaky or underhanded, just that some of his opinions slipped in as fact. I catch myself doing this in areas that I am expert in and have to back myself off. Theories unproven are just theories no matter how dear they are to us. Nothing was directed your way since you had shared the article. I was just trying to be frank on what I thought could possibly be driving the info there. Apologies if I was too rough on the guy.

I read a lot of what you and Kevin C post as I believe you both to be of more of a scientific bent than I am. I would love to take a seminar of kevin's as I think some of the haze I have would clear up. I can get lost in the aesthetic side of things so right now I am asking hard questions and trying to do homework on things I think I need more knowledge in. Every question I get answered raises two more..... Once I get to the part of making pretty metal and wood hopefully I won't be a pesky on the science side of things.

Do you think warping with O1 could be an issue with air quenching?

Ted
 
on dewars....

I can find a lot of different storage containers for LN online. I am I correct in thinking that the biggest opening at top is best for blade treating? I would think that the larger the opening the easier it will be to use. Some are actually like an igloo cooler with large lids and a straight container with no bottle neck. Would there be a trade off in how long the LN lasts? Smaller lid-longer storage life?

Thanks,
Ted
 
You use a cable or string to drop it in the liquid nitrogen. The bigger the opening, the faster it will evaporate.
 
Smallshop said:
Do you think warping with O1 could be an issue with air quenching?

Ted
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dont have a clue. part of reason for a trial. will be using large enough plates so blade will be clamped flat. when the adventure at work settles down(we are in the last couple days of a 30 day maintenance shutdown) will give it a try. time to go play maintenance man. good luck with new furnace.
 
Thanks! Just got a job in so probably won't get to play for a couple weeks.

After all the different places I thought to park it I finally put it on a hydraulic cart with wheels so I can store it when not in use. Best use of limited space.

the four decent blades I made were O1. two of them held an excellent edge. I loaned one to my brother's best friend who's a backyard chef. He's had it for 8 yrs and refuses to return it. (He knows I'm tickled that someone is enjoying using that knife).

When I see all the different recipes for HT and temper I wonder how many of us are really getting max performance out of the steels we choose. Then when I think of all the designer steels I wonder how necessary they all are. I think the sharpest blade I ever used was 440-c and that is almost old school these days. I read reviews of steels by end users and the results vary wildly. I can only think the HT did also.

Possibly the equipment you are using is higher accuracy/ maintenance than what most of us are using? If so, experimenting may yield a little better results than some of us can realize with our own equipment?
 
Just a cautionary note on doing research on cold (dry ice) and cryogenic (liquid nitrogen) for knife use. 3 or 4 years ago I did a fair amount of research into it. One thing pointed out in one of the articles (published by a university in Ireland) was people play with different rules and compare them somewhat haphazardly. Some use cold and cryogenic interchangeably (cryo by definition is liquid nitrogen or colder), some temper before, some after, some do it as part of the quench, some after all tempers etc. My experience is you have to dig a little deeper than you thought to be sure you know the rules when comparing different articles and services. Basically, you need to know just enough to ask some specific questions, even if just to yourself. After that, things start to make a little more sense with much less effort.
 
Me2,
I appreciate the cautionary note. I too have seen a lot subjectivity. In my earlier post I was including cryogenics in the thought...."When I see all the different recipes for HT and temper I wonder how many of us are really getting max performance out of the steels we choose. Then when I think of all the designer steels I wonder how necessary they all are. I think the sharpest blade I ever used was 440-c and that is almost old school these days. I read reviews of steels by end users and the results vary wildly. I can only think the HT did also."

Different steel suppliers, furnace builders, knife makers all have different ideas of what's best for a given steel. Then as Scott pointed out (somewhere...can't remember which post) The different steel MFG all have a little different process that will fall under the same alloy designation yet are probably different enough to yield slightly different results. He always uses the same MFG per steel designation to remove one more variable.

On Cryogenic treatments the one common area of agreement is that everyone believes it does something to the stainless steels and to a few of the non stainless also. In hopes of eventually selling blades that don't make ladies shriek in horror at the patina, I want to learn stainless steel treating. I cannot convince myself that Cryogenic treatment is useless here even given the large body of positive info.


I have been slowly "digesting" Kevin Cashen's articles and have developed a high level of trust in his info. When he is unsure of something he will qualify his statements accordingly, state theory as theory, and proven fact boldly. A rare combo these days. So using some of his info as litmus has helped me wade through some of the info in that vast echo chamber we call the Internet.


I don't want to become a scientist as I'm not wired that technically. But I do want to be scientific enough to understand the why and how of this stuff. I abhor "back-woodsy-ness" as an excuse for not really knowing what I am doing....along with all the clichés that seem to accompany marginal knowledge in a given area...."this is how we always dun it...." "it was good enuff fer my pappy". In my field of machining this type of thinking abounds and will hold you back if you fall prey to it.

And I have at times.


At the 80 thousand foot level you can look across man's time on earth and probably say that we are in the ultimate sweet spot of blade quality. I think probably most knives being made by guys in their garages today are far superior to the blades across history. (maybe wrong here this is my unqualified opinion as I'm no knife historian)
 
Good topic - one I've read about a good bit. No more knifes than I make in a year, cyro is not really in the picture due to cost. Since I currently do mostly SS blades, I have fairly well settled on Sandvik steels, especially 14C28. Per the Sandvik folks, even freezing to -5ºF will provide almost a point of extra Rc, while -95ºF (dry ice) will provide around 2 points Rc, and along with this extra hardness goes a bit of extra toughness. I find -5ºF does seem to give about 1Rc extra compared to no cold. I have no idea if -95ºF would give the 2 points they claim. The Sandvik engineer I talked with said the same thing as Kevin C. - just get to temp, no reason to hold at low temp longer.

Here is a thread on the "Steel Reference" forum I posted on Sandvik steels. They seem good, easy to heat treat, plate quench, and seem to hold an edge pretty good. I'm not sure why they're not more popular as they are some of the lower cost SS blade steels.

http://knifedogs.com/showthread.php?34605-Sandvik-Blade-Steels

Ken H>
 
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Smallshop said:
...I have been slowly "digesting" Kevin Cashen's articles and have developed a high level of trust in his info. When he is unsure of something he will qualify his statements accordingly, state theory as theory, and proven fact boldly. A rare combo these days. So using some of his info as litmus has helped me wade through some of the info in that vast echo chamber we call the Internet...
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Thank you for your acknowledgement in that Smallshop, I have striven to follow that approach as much as possible in my career in order to avoid creating more of the misinformation that has plagued our craft for far too long. The reason I prefer to pinpoint specific properties and microstructures is the objectivity involved. To say “my special method of treating the steel makes a better blade” is so general, and entirely subjective, that it falls somewhere between meaningless and outright sophistry. Not only beauty, but “better”, “superior” or even “good” is entirely in the eyes of the beholder. While one person finds a specific combination of properties as the ultimate blade, others see it as barely fit for a butter knife.

But while stating that any treatment produces a “better” product is meaningless, stating that it produces the highest percentage of observed martensite as well as the highest levels of tensile strength, is concise, objective and, by extension, perhaps the most honest approach. These are just the facts, to some this will mean the greatest edge retention and overall blade strength, to others it will mean a blade that lacks too much ductility to bend, rather than break, in a vise.

Honesty seems to be the key element here, even in the case of apparently innocent mistakes. For a bladesmith to relate a change in observed properties after performing an operation all that is necessary to convey that is that they did “A” + “B” and got “C”. But personal bias invariably comes into play and in an attempt to strengthen their position will attempt to explain the result “C” with little more than assumptions, and often end up revealing a lack of understanding of the principles that they try to invoke. Just one good example of this is bladesmiths referring to the “packing” of iron “molecules”, in an attempt to sound authoritative in defending edge packing claims. They would be much more credible just describing what they can see rather than using technical terms in a way that clearly demonstrates a lack of understanding that they are implying they have. The reason I spent the years and dollars that I have in setting up my own lab is that I wished to pursue the objective quantitative approach with confidence that I knew what I was talking about.

It is the honest confusing of possible causal relationships to outcomes that has given birth to so many myths in knifemaking, but it is dishonest* adherence to our preconceived beliefs and assumptions about the same that has allowed them to become the detriment to the crafts advancement that some of them have. Then when you mix personalization with these biases you get the venomous cocktail that results in something as inexplicably absurd as two grown men coming to blows over what they quench hot steel in.

*No I am not calling anybody a liar, but I to believe the most destructive lies of all are the pretty little ones that we tell ourselves without even realizing it.

P.S. One of my litmus tests, that has served me well over the years, is if the person has anything to gain or lose by their position. For example- I was influenced early on by bladesmiths who rejected most of the claims of forged blades being superior to stock removal. Here were guys who had nothing to gain from such a position, and indeed they were undermining their own method. The only motivation I could see was a clear conscience by adherence to the facts at all costs. It is easy to be a fanatical believer in something that boosts your P.R. or sales, but it is tougher to embrace facts that do not make your life any easier (which brings us back to those pretty little lies we tell ourselves:3:).
 
This has been a fun read.

Overall I gota say Thanks to you Dogs who take the time to not only help, But to explain in detail your opinions and conclusions based on your hard earned efforts seeking "truth"

Now to the OP. YES. Its worth doing. IF you plan to use Stainless or other high alloyed steels. CPM powder steels. Or most of the "tool" steels.

This, coming from a guy who primarily uses High Carbon and Damascus. I fought even using Stainless for a long time. Then once I did determine to use some, I had to try to learn how to properly heat treat SS. Cryo treatment quickly followed.

RC numbers are great. and a big part of the equation for many makers and buyers alike. And for me. Lets face it RC is one of the main things talked about and it is important. But not as much as many other factors that make up a good cutting tool.. Things like Blade geometry, edge profile and how the edge holds and how thin I can make the blade at and above the edge without catastrophic failure when the knife was used as its intended for its design. to name a few that are important to me. What I found in the tests I ran.. Higher RC, better edge retention/toughness of the edge of a cryo blade over same steel without cryo. And not just a little difference that could be me and my wanting a better result. But a noteworthy difference in edge performance.

I surly dont claim to be a expert in this and your results may vary from mine. :)

I think your on the right track. and your desire to learn and willingness to take that "quest for knowledge" will take you far

God Bless

PS. I have Cryo'ed over 100 blades in my shop and of these. Only 2 blades have failed due to the stress caused by freezing it. again your results may vary!
.
 
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HHH....2% is well within acceptable parameters for a small scale manufacturing operation! Obviously a large corporation making products (not doing research) would shoot for much lower. But your confirmation that the results are not negligible are key. Thanks.

Kevin C...you are addressing one of the deepest issues of human nature as concerns truth in discovery in any field of endeavor. Well said.Also, your statement......" One of my litmus tests, that has served me well over the years, is if the person has anything to gain or lose by their position." is in accord with why I swung pretty hard at the fellow that wrote the article about Cryogenics. A president of a Cryogenic service has much to gain by convincing us we would be better off sending our steel to him. I probably could have been less forceful with my observations yet I felt that if even one aspiring knifemaker gave up on experimenting with this process as impossible to achieve at home due to the writer's bias(regardless of motivation) then an unintentional (or not unintentional...you all decide) injustice was being done. I was in no way challenging that man's integrity yet the premise of the article had a subtle stench. Bias is something EVERY ONE OF US is seemingly hardwired to bend to. That is why double blind tests are performed at the clinical trial level. It removes the human. If the human is involved with the results before the data can objectively be analyzed there will be a bias. Pretty much proven over and over.....

It is never a matter of honesty it's due to being human. A person lacking honesty in industry is merely a fraud, not unintentional bias entering into the process being analyzed.

There have been many humorous examples done to show how easy we lose objectivity. The human brain/psyche is so amazingly elastic when it comes to discerning truth.

Why is this stuff important to some noob trying to decide whether cryogenics are necessary and doable, or which steel to use, etc? Because I've been sent down rabbit trails before, and, never in any other time in history have we as individuals had so much immediate access to experts in any given field. The fly in the ointment is always determining who's really expert and that is done by asking lot's of opinions for a certain amount of cross sampling.

Once again thank you all very much and I would still love to hear any opinions on cryogenic treating. How to, why not to, why to, cost evaluation, worth it for the gain or not, etc.

KenH, thanks for the input and the link!
 
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Smallshop said:
...It is never a matter of honesty it's due to being human. A person lacking honesty in industry is merely a fraud, not unintentional bias entering into the process being analyzed...
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I should have worded things better. You are correct that the simple bias that creeps into almost every aspect of our lives is just human psychology and not a matter of honesty, folks who refuse to acknowledging or accept that this problem exists enter into a gray area. Simple bias is free of moral judgments, but when folks start intentionally plugging their ears, shouting others down or attacking to keep from hearing anything that could legitimately challenge their world view; I believe that is an honesty issue.
 
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I totally agree Kevin. When a person makes the conscious decision to stick to the fable after being shown/proved the truth, it becomes dishonest.

concerning what you just quoted me on, I actually was explaining my treatment of the one article that Scott shared not trying to correct anything you said. I thought you hit the nail on the head. I was concerned that my evaluation of that article/writer could have been perceived as unkind. I was trying to attack bias not people....

It's a struggle for anyone to advance truth at all costs. It's pathetic when someone doesn't want to address truth and cling to familiar nonsense.
 
Smallshop said:
When I see all the different recipes for HT and temper I wonder how many of us are really getting max performance out of the steels we choose. Then when I think of all the designer steels I wonder how necessary they all are. I think the sharpest blade I ever used was 440-c and that is almost old school these days. I read reviews of steels by end users and the results vary wildly. I can only think the HT did also.
QUOTE]

on recipes for heat treat and temper, i always refer back to the maker's recommendation and use that as a starting point. O1 for instance, all makers say heat to 1450-1500, soak for 10 to 30 minutes, quench in warm oil, temper for two hours. so my recipe of 1475(800C), soak for 8 to 12 minutes after part is heated thru, quench in 125F oil, temper at 300F for one hour. water quench, scrub, temper at 325 to 400 for one hour. it is following the mfg recommendations.
where i have an issue would be something like heat to 1600F, hold for one minute, quench in room temp ATF . heat to 1550F, hold for two minutes, quench, temper at 475 for Rc 58 and blade that will bend 90 degrees. that is not even close to industry standards and ATF is not a safe quenchant.
440C has been around a long time and is a proven performer. It is a fairly simple alloy, carbon, chrome, a dash of moly, a dash of silicon, and some manganese. it will polish nicely. but it is old, it is not cool, it has fairly simple straight forward heat treat.
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" but it is old, it is not cool, it has fairly simple straight forward heat treat."

I think between O1, A2 and 440C you could probably cover the bases on any knife you'd ever need. But we all love to fiddle with new things.....

My wife didn't seem too thrilled when I told her I might need to get a LN storage container. She was a bit relieved when I told her a farmer buddy might be able to get me a tank they were using to store bull semen.....for free
 
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