LN2 an inferior method of an extended quench question

Thank you, Larrin Larrin . I haven't read up on this in the 15 years of my hiatus. Sounds like anything beyond the fact it converts RA has yet to be proven.
 
Here are papers that looked at the effect of cooling rate though most/all are behind pay walls. Like other cryo studies I don’t see any clear trend to rely on based on these studies and at least one of them admits that the effect size was extremely small if there even was one. The benefit of wear resistance testing is that it is highly variable so they can find trends in the data.

 
Larrin said:
Here are papers that looked at the effect of cooling rate though most/all are behind pay walls. Like other cryo studies I don’t see any clear trend to rely on based on these studies and at least one of them admits that the effect size was extremely small if there even was one. The benefit of wear resistance testing is that it is highly variable so they can find trends in the data.

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So, there’s not a real difference between dipping the blades in liquid nitrogen and slowly let the blade achieve that temperature, Larrin? I mean, toughness wise?
You answered this above, sorry.
 
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hugofeynman said:
So, there’s not a real difference between dipping the blades in liquid nitrogen and slowly let the blade achieve that temperature, Larrin? I mean, toughness wise?
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Only one of the studies looked at toughness. A "direct soak" at -73°C led to a small improvement in toughness vs no cold treatment though it also showed a small reduction in strength. The study claims that a 3°C/s cooling rate led to the best toughness and strength. Either the reduction in strength was a fluke or this was due to interactions with the high temper, where in come cases cryo shifts the peak strength tempering range. That is one of the difficulties of these cryo studies is they will use different steels and different base heat treatments and often don't vary the austenitizing and tempering temperatures. When they do, they typically conclude that the austenitizing and tempering temperatures had a much bigger effect than the cryo variables. In the same study they found that a 1°C/s cooling rate led to a reduction in both strength and toughness, so even if we buy the results of the study, it wouldn't clearly show that slower is always better, but would paint a more complex picture that you must optimize the cooling rate based on steel and heat treatment.
 
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hugofeynman said:
Again, rodriguezryan14 rodriguezryan14 , I apologize for referring that slowly cooling could be better than directly dipping the blade in LN. Larrin cleared this.
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Your good man. I’m not worried about it. My results basically speak for themselves. So I don’t get offended. The only thing that bothers me is when others that have never tested or heat treated weigh in and and try to criticize our work! Not you. You understand and work with us on heat treat and contribute to Larrins research!!
The other guy. That thread was locked down because of a simple conversation. So I never did get a response from that individual!
 
rodriguezryan14 said:
Nothing very scientific, cut and chopping tests so far. My edges are ground thinner, convexed, and have just held up better
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I ask because I play with 52100 steel and I found that it is hard to get some data/conclusion with tests like that ..it is difficult to notice the difference .
Do you have a Rockwell tester?
 
Natlek said:
I ask because I play with 52100 steel and I found that it is hard to get some data/conclusion with tests like that ..it is difficult to notice the difference .
Do you have a Rockwell tester?
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Yes I do. I’m primarily working with A8 mod right now. That’s basically infi. My blades range from 59-60 rc on average! I’ve had a couple come out in the 58 range with no cryo and high temper! I have 52100 on hand, just haven’t got around to heat treating any of it! I’ll eventually experiment with it in the future. I find A8 mod to be more than good enough for a lot of different blades right now
 
Larrin said:
Here are papers that looked at the effect of cooling rate though most/all are behind pay walls. Like other cryo studies I don’t see any clear trend to rely on based on these studies and at least one of them admits that the effect size was extremely small if there even was one. The benefit of wear resistance testing is that it is highly variable so they can find trends in the data.

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Thank you, Larrin Larrin . I will read whatever I can on all of them.
 
a knife is the sum of its parts, and while it's interesting and informative to go into the weeds of heat treating, there are many factors which can make for a bad knife even if it's heat treated perfectly. When it comes to the performance of the blade itself, physical dimensions play a much bigger role, in my view, than whether its heat treatment is 'good enough' or 'the best'. I personally strive for the best, but understand that is probably not going to be my result the majority of the time.

don't get me wrong, I do try and be meticulous when it comes to how I run my heat treating, and am open to learning as much as my brain can absorb about it and adopt better methodology whenever possible, but.... there are many variables outside my control. The temperature of my shop being one- that'll affect all sorts of things in small ways. A minute here, a minute there. How many knives are going through the process at any given time. How warm my quench plates get. Of course there are ways of mitigating a lot of variability, but my feeling is that the results are probably not significant compared to many other aspects of a knife's design.

if a maker chooses the right material for the job, has a digital kiln, preps their work properly, follows a proven protocol and makes informed adjustments taking into consideration the dimensions of the knife they're making and its intended use, then I think their patrons/customers will be pleased with the outcome of the heat treatment. Even if it's not perfect. If perfect was what people were looking for when buying handmade knives, there would be very few humans involved in the making of them.

as for the idea that slowly freezing a knife is better than quickly freezing it, well it just doesn't make sense to me. When I think of quenching, I think of something that happens at speed. Freezing a knife is part of the quench, in my mind, so to me it makes sense to get that done quick as possible. Now, I don't know much about this stuff, but I feel like LN2 is superior to a dry ice or deep freeze because it acts on the steel faster, not just because it ultimately gets the steel colder
 
I remember reading one paper that was doing tests with cryo, and determining different things about the amounts of retained austenite remaining. The reason i bring it up, is in that test. They quenched. Then dipped the blade in ice water, then went right into the liquid nitrogen. I thought it was an interesting way to continue the cooling of the quench faster than letting it get to room temp from the quench, and going into the dewar.

That said. I think larrin made a good point in his first post, as well as the others. As knifemakers, the only reason we do cryo at all is to reduce retained austenite. So getting down to the lowest temp, the fastest we can avoids letting the austenite stabilize in the meantime.

Im sure if slowly cooling it ends up having a little more retained austenite. It likely will act a little bit tougher than otherwise. But come with the same drawbacks that higher retained austenite will have. Like more difficulty sharpening (deburring).

Its just how this stuff is. Nothing is going to magically change the material we are working with into something else. We are just getting whatever steel, and getting it to form martensite, and tempering it. We can change things like austenitizing temps, tempering temps, cryo, no cryo, whatever. Its still just going to be steel, and do whatever that steel is expected to do, at a given hardness, with a given carbide volume, carbide size, grain size, with whatever ammount of carbon, or other elements in solution.
 
And that all makes perfect sense. I would imagine you get more retained Austenite from the slow cool down, vs the rapid ln2 dunk. Just like I’ve been told not to put my knives in the freezer for more than 10 minutes after plate quenching! Because austenite stabilizes, and cryo won’t do much after!! But what do we know? Some of these guys that have never heat treated a knife or made a blade period seem to know much more than we do apparently!!
Lorien said:
a knife is the sum of its parts, and while it's interesting and informative to go into the weeds of heat treating, there are many factors which can make for a bad knife even if it's heat treated perfectly. When it comes to the performance of the blade itself, physical dimensions play a much bigger role, in my view, than whether its heat treatment is 'good enough' or 'the best'. I personally strive for the best, but understand that is probably not going to be my result the majority of the time.

don't get me wrong, I do try and be meticulous when it comes to how I run my heat treating, and am open to learning as much as my brain can absorb about it and adopt better methodology whenever possible, but.... there are many variables outside my control. The temperature of my shop being one- that'll affect all sorts of things in small ways. A minute here, a minute there. How many knives are going through the process at any given time. How warm my quench plates get. Of course there are ways of mitigating a lot of variability, but my feeling is that the results are probably not significant compared to many other aspects of a knife's design.

if a maker chooses the right material for the job, has a digital kiln, preps their work properly, follows a proven protocol and makes informed adjustments taking into consideration the dimensions of the knife they're making and its intended use, then I think their patrons/customers will be pleased with the outcome of the heat treatment. Even if it's not perfect. If perfect was what people were looking for when buying handmade knives, there would be very few humans involved in the making of them.

as for the idea that slowly freezing a knife is better than quickly freezing it, well it just doesn't make sense to me. When I think of quenching, I think of something that happens at speed. Freezing a knife is part of the quench, in my mind, so to me it makes sense to get that done quick as possible. Now, I don't know much about this stuff, but I feel like LN2 is superior to a dry ice or deep freeze because it acts on the steel faster, not just because it ultimately gets the steel colder
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Seedy Lot said:
In Larrin's book on page 289 he has a chart for RA with T1 and aging time. If the steel reaches cryo tempterure within an hour the increase in RA is less than 1 percent.
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He gives another example after, of w1 which after aging at room temp an hour, ends up having a bigger increase in retained austenite than the t1. And explains that the carbon in solution being higher than in the high speed steel, caused more stabilization of austenite in that ammount of time.

So really. Its going to matter what the alloy is, how much carbon is dissolved into solution, and other elements, austenitizing temp. That are going to effect how much retained austenite is formed in the time it would take for a slower cooling to the final temp.


All this said. I just really don't think one is superior than the other. I have a feeling all other things being equal they both will produce results. In knives that are nearly identical.
 
Blankblank Blankblank Even the W1 charts are showing less then 1 percent RA gain from immediate cryo to cooled within the hour.

For me it is about 6 minutes from plate quench to cryo dewar. I let the blank sit in the plates for a minute or so and then put the clamped plates in a five gallon bucket of ice water for a couple minutes then the ice water cooled blank into the cryo.
 
Seedy Lot said:
Blankblank Blankblank Even the W1 charts are showing less then 1 percent RA gain from immediate cryo to cooled within the hour.

For me it is about 6 minutes from plate quench to cryo dewar. I let the blank sit in the plates for a minute or so and then put the clamped plates in a five gallon bucket of ice water for a couple minutes then the ice water cooled blank into the cryo.
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Yeah. I'm sure thats more than fast enough for liquid nitrogen.

I certainly would still try to avoid any unnecessary holds at room temp whenever possible. Even with those 2 examples not having a giant increase at liquid nitrogen temps. I don't see any benefit to going down to the cryo temps at a slower rate.
 
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