Cryo?

This is one of those threads that I usually try to steer away from-just not often enough. Remember that the thread started was dealing with D2, stainless steel, and other complex alloys and not something as relatively simple as even 52100. With some alloys, as indicated by their data sheets, cryo or even just cold treatment does make an improvement. Other steels you're just making cold. The formation of eta-carbides and their significance seems to be a area that is still under research and discussion.

As far as people putting their garbage out there, remember it goes both ways. I get frustrated at people who don't have the ability to isolate and test the variables involved reject decades of metallurgical science for their own pet theories and they get tired of me quoting Verhoeven and other authors of books on metallurgy. We just need to try real hard and treat each other with respect and know when to back off. Remember, never argue with an idiot. They'll drag you down to their level and beat you with experience.

Doug

Like the old saying goes:

6 to one 1/2 dozen to the other. :D

You guys really do need to get along better though, granted competition is there, but as a whole I would recommend showing the respect that is earned. :)

Nobody knows everything, that would be impossible to even think about that.
 
I'm not sure which guys aren't "getting along" on this forum - it really seems that Boss keeps everybody in line pretty good - what little they do need keeping in line.

By far, for the most part everyone on here seems to get along quite nicely. Not always agreeing isn't "not getting along". Especially as long as true repeatable knowledge is shared.

Maybe times the difference that shows up with good solid testing won't be noticed in normal everyday use by the average person.

All I wish to really know and understand is what can be shown by scientific testing and repeatability.

Ken H>
 
Might be a silly question but do you have to cryo the stainless? And steels like d2? Thank Davey
the jury is still out. there may or may not be gains in performance. here is a link to an easy to read article from Industrial Heating, a respected metal industry source on the subject of heat treating. http://www.industrialheating.com/ar...ogenic-treatment-on-properties-of-tool-steels

the article address the use of cryo for D2 and similar alloys(VANADIS 6 and Vanadis 4). it looked at sub-zero(-130F) and cryo(-320F) treatments. some of the conclusions reached:

3. The hardness of CT materials is lower in comparison with no CT by 1-2 HRC and does not depend on the CT holding time.

4. The differences that have been proved so far between CT and no-CT materials are not too practically important considering CT costs.

5. Investigators are not unified in the opinion of CT benefits, although research has been going on for more than 50 years. General conclusions and achieved results do not differ much steel by steel

these are direct quotes from the article. read the article and the source documents, they were written by scientists stating the results they found after doing testing using industry standard procedures.
 
That's the complete opposite of what is normally expected and experienced so I am not sure what was going on with their experiment.

But it was interesting none the less.
 
That's the complete opposite of what is normally expected and experienced so I am not sure what was going on with their experiment.

But it was interesting none the less.

what is "normally expected"? do you have links to any documents showing what is "normally expected"? if you read the article, they list all their steps, including times and temperatures. it is a whole lot more involved than dropping a blade into a container of LN2 and pulling it out 24 hours later. I come to this forum to gain information based on proven fact, not claims. Cryogenic treatment of blades is expensive and the materials used are hazardous. it is irresponsible to answer a basic "do i need to ....?" question with an answer like
"Ideally the blades should be kept in LN2 for 24 hours before the tempering cycles begin."
 
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I heat treated a blade of cpm154 the other day. I used a double wrap of foil to minimize heat patina. I plate quenched and took readings. I got 59.5, 61.5 and 60hrc. I expected 61 as I have used this recipe dozens of times. I suspect the double foil wrap gave me a slightly lower quench hardness than what I am used to.

Then to liquid Ln for 15 hours. No snap temper. Next readings were 63.5,63.5,63
then temper at 400 for two hours once, readings were 59.5, 61
temper again for two hours and it settled in at 60.5 to 61 which is where I will leave it.

Some might say a cryo bath fixes a bad quench and is a crutch. Some might say a cryo bath improves a typical quench.
I know every time I have used liquid Ln I have seen a movement in hardness. I routinely measure each step. Does the cryo improve cutting performance? I think so. Does it improve grain structure? I think it reduces retained austenite and converts it to martinsite which we know is good.
I did one cutting comparison myself a long time ago. I got what I think was a slight improvement in edge retention but the testing (cutting rope) was so subjective it's just hard to be sure. We need a CATRA machine I guess.
 
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Scott - thank you for the link. Very interesting results and it does seem to be well tested for bending and hardness comparisons of CT. There is an interesting comment at bottom from a guy who takes issue with the tests. It really seems to confirm what I've read before, how important CT (or Cyro) is depends to a GREAT extent on the steel used. AND - from that report:

Moreover, exceeding the optimal austenitizing temperature means that MS falls well under subzero. For example, the MS temperature of X153CrVMo12 (1.2379, AISI D2) is 175˚C (347˚F) for an austenitizing temperature of 1050˚C (1922˚F) but -100˚C (-148˚F) for an austenitizing temperature of 1200˚C (2192˚F).[1]

Note these are all higher carbon steels with carbon level 1.4%.

I would think these companies who develop a special cutlery steel (Sandvik, Crucibale, etc) would have tested to determine proper HT and if/what CT/Cryo is required and just how much it helps. Sandvik says clearly Cryo is of no benefit, but that CT (-95) does help, and that even a -5F treatment helps.

Perhaps it got off the OP's original question a bit, but still good discussion and I've learned from it.

Ken H>
 
Thanks for the article Scott. Always interesting to hear a point of view that does not conform to conventional wisdom. While I accept their observation that the benefits of cryo are unclear, I also question the hardness findings. As Boss pointed out, many of us on this forum have done hundreds, thousands or tens of thousands of blades with cryo and have never seen a 'lower' Rockwell reading - in fact quite the contrary.

While I support the method, I've become skeptical of the results of some scientists. They are generally employed by someone who wishes a given outcome. If I were to see a preponderance of evidence from multiple sources suggesting reduced hardness or function with cryo, I'd re-evaluate my methods. For now - not so much. :3:

Rob!
 
We need a CATRA machine I guess.

That still wouldn't matter to some, even with a CATRA machine and Aerospace Furnaces.

You would need a team of scientists with slide rules in hand working in a vacuum clean room doing quadruple double blind testing, 100 runs, 50 different steels then have it all published and peer reviewed.

Even then it still wouldn't be good enough if the results weren't what some wanted them to be.

So you could spend 10 Million Dollars in research and it still wouldn't matter.
 
Not to side track this, but that reminds me of the climate change debate. As far as sub zero quench goes, with my limited experience I think it's a beneficial step in the knife making process.
 
We need a CATRA machine I guess.

The testing I was referring to earlier was done on a CATRA machine. Looking over it though, the cryo procedure was not provided in detail. It was evidently a relatively short soak, perhaps just long enough to equalize at temperature, but a specific time was not given.
 
Something I have been wondering about is the ETA carbides that form in cryo, but not sub-zero. IIRC, they are only there after cryo, and once tempered they dissolve. Is this true? At a structural level, what improvement would cryo result in over sib-zero, as long as Mf is reached by -110f? It seems obvious that Mf at -200f would benefit from cryo, but that's not what we are talking about here.
 
While I support the method, I've become skeptical of the results of some scientists. They are generally employed by someone who wishes a given outcome. If I were to see a preponderance of evidence from multiple sources suggesting reduced hardness or function with cryo, I'd re-evaluate my methods. For now - not so much. :3: Rob!

the folks who wrote the article i quoted own and operate a precision heat treat service based in the Czech Republic. http://www.prikner.cz/en/ one would think they would only publish articles that showed performance increases after cryo as cryo is part of their core business.
IMHO, if you are trying stainless or high alloy steels for the first time, perhaps sending blades to someone like Peter's would give the best results until you are ready to invest in a precision high temperature furnace and the equipment to safely use liquid nitrogen.
as an aside, read this link http://www.cryogenictreatmentdataba...chilling_toughens_metals_increases_tool_life/, please note the date. as a tease, the author talks about cryo treatment of fuel pump parts used on the B-36 bomber.
 
Well, I do think, perhaps to a great extent - how well cyro or CT works will vary a GREAT deal depending on type of steel - does that not make sense? Boss mentioned CPM154, and I do suspect he's limiting his input to the steels he's worked with.

Ken H>

yep. I have had a similar increase in RC with cryo using BG42, CPMS30, CPMS35VN, ATS34, 154CM.
I have seen less of an increase in the few times I have dunked 440C.
I dunked some 01 once and didn't see any change after cryo.
 
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The problem with scientists performing testing and interpreting the data only to support their pre-determined point of view is not just a problem with scientists acting to support company goals. It's also a problem with non-technical people who wish to forward their own agenda. As mentioned above, you need to know what alloys you're talking about. You also need to know how the testing was done and how much does it correlates to function as in how well does the charpy test or HRc testing relate to edge holding. You also need to know if the method is valid like using a light microscope to look for small amounts of retained austinite or a hand held microscope to do any analysis. Sometimes you have to be honest with yourself enough to ask if you are only willing to consider your own pre-determined point of view.

Doug
 
I doubt that you would ever see that happen. :)

Never say never. :biggrin: I see on restarting the upgraded Large Hadron Collider, scientists expect to observe rainbow gravity - parallel dimensions and invalidate the big bang theory. Of course, all that could explain a great deal of the abnormalities we find in heat treat operations.

(sorry - might be getting off topic - or not)
 
Never say never. :biggrin: I see on restarting the upgraded Large Hadron Collider, scientists expect to observe rainbow gravity - parallel dimensions and invalidate the big bang theory. Of course, all that could explain a great deal of the abnormalities we find in heat treat operations.

(sorry - might be getting off topic - or not)


Well yes that could have a large effect on how things change. LOL :biggrin:

More like they keep getting the same results as in the hardness going up, but they can't have that happen so they implement the slide rule effect while burying the changes they did to make it go down on purpose to meet the original predetermined outcome.

So then you have a ton of Knife Makers etc telling people it rises because that's what they are actually experiencing, but one Scientist telling people it's not right it drops.

Then take a few people that read that and use the bad information to argue their point on a forum.

Sound about right?
 
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The problem with scientists performing testing and interpreting the data only to support their pre-determined point of view is not just a problem with scientists acting to support company goals. It's also a problem with non-technical people who wish to forward their own agenda. As mentioned above, you need to know what alloys you're talking about. You also need to know how the testing was done and how much does it correlates to function as in how well does the charpy test or HRc testing relate to edge holding. You also need to know if the method is valid like using a light microscope to look for small amounts of retained austinite or a hand held microscope to do any analysis. Sometimes you have to be honest with yourself enough to ask if you are only willing to consider your own pre-determined point of view.

Doug

if scientists are selective in their results, or interpretation, it isn't science by definition.
 
Well yes that could have a large effect on how things change. LOL :biggrin:

More like they keep getting the same results as in the hardness going up, but they can't have that happen so they implement the slide rule effect while burying the changes they did to make it go down on purpose to meet the original predetermined outcome.

So then you have a ton of Knife Makers etc telling people it rises because that's what they are actually experiencing, but one Scientist telling people it's not right it drops.

Then take a few people that read that and use the bad information to argue their point on a forum.

Sound about right?

Do you have any examples of the changes that could be made and then buried to make hardness go down after cold/cryo treatment? Is anyone actually claiming the hardness goes down after cold/cryo? If so, did they give an explanation or mechanism as to why?
 
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