Cryo Treatment

B

Brandon369

Joined
Dec 31, 2007
Messages
149
Does anyone know where to buy the right equipment to do the cryogenic treatment of knives?

-Brandon
 
Note that cryo is part of heat treatment - not something done later on.

Rob!
 
Well, I don't know Robert. 300below didn't beat around the bush, he went straight for the commercial plug with his very first post at these forums, that is a heck of a lot more straight forward than what we have encountered in this conversation before. Give him credit, his cards are on the table, at least until a mod thinks one should pay for advertising on this site. ;) At any rate I admire the openess.
 
:jerkit: :rolleyes:



:rolleyes:
Well dont quote the idjits.
 
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I'll say it one time and refuse to get into a debate - friendly or other- over this. It has been beat to death over and over.

Cryo is the lower end of the quench. Steels with high alloy content and thus more retained austenite can have an extremely low Mf point, often 100F below zero. The cryo is done to finish the quench and bring the steel to below the Mf. A snap temper at 200 is just a quick stop on the way to stabilize the steel a bit. Once the quench is done ( the cryo) the retained austenite has been mainly converted to martensite. The steel now needs to be tempered to form tempered martensite. A second cryo may have some advantage in very complex steels (High Alloy). The steel needs a second, and sometimes a third temper to convert all the newly transformed martensite into tempered martensite.

While the cryo can be done long after quench and even after temper, it will do more good as a part of the initial quench. Taking the steel from 1950F to -200F in a steady (more or less) drop will get the best results. Shipping it off days or weeks later will gain much less. Doing cryo on a fully finished knife is mainly a waste of time and money.

Simple steels , like 1095, have a Mf point well above room temperature, and will gain little or nothing from cryo.

Statements that cryo will change the properties of steel, and make it into super steel are mainly sales talk. There are reasons for cryo in industry, but for knives, it is to finish the Mf......period. It will gain some toughness and a little hardness. It will not make the steel able to cleave anvils, or cut rope ten times longer.

Thanks for listening and I will put this to rest as far as I am concerned.
Stacy
 
Nathan the Machinist said:
:jerkit: :rolleyes:
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Well! I have never been so insulted in all my life! Nathan your callous use of the :jerkit: so soon after our group therapy session over its effects leaves me speechless! You sir are a cad! :p I am so traumitized I am dialing my counselor as I type this! Really, how could you?:(
 
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Kevin R. Cashen said:
Well! I have never been so insulted in all my life! Nathan your callous use of the :jerkit: so soon after our group therapy session over its effects leaves me speechless! You sir are a cad! :p I am so traumitized I am dialing my counselor as I type this! Really, how could you?:(
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Kevin, you need to be careful, here... you're becoming so relaxed that you're allowing your sense of humor to show!:eek::D
 
Kevin R. Cashen said:
Well! I have never been so insulted in all my life! Nathan your callous use of the :jerkit: so soon after our group therapy session over its effects leaves me speechless! You sir are a cad! :p I am so traumitized I am dialing my counselor as I type this! Really, how could you?:(
Click to expand...

I'm a "cad"?

A "Computer Aided Design"?

Dude...

You see Kevin, that wasn't a "group therapy", it was a "group intervention". You've been getting high on L6 fumes (again) and were developing a real problem, and we, your loving forumites, stepped in to help you. That your memory has twisted it into a "group" "therapy" about :jerkit: is a very bad indication for your current state. You been mixing hashish into the salts again? Does that work?

heh heh heh...
 
L6 fumes are actually quite tame, the only thing to worry about is the nickel and chromium dust. Breathing too much of it can make you get all quirky about hitting all kinds of silly things really hard with blades. 52100 is the one that scares the hell out of me! I have always believed there is something toxic in that steel, something similar to the mercury in a hatters shop which goes air born and gets into smiths brains. Since everytime I hear of just plain bizarre things being done to steel that one seems to be involved. Things that may actually need a good freezing to compensate for.;)

Matt, now you are the one who is getting loopy and seeing imaginary things, since all you have to do is ask my wife and she will tell you that I have no sense of humor. Well that is not exactly true either, she would most likely say that I have one but it is so twisted and strange that most would not recognize it as one:(.
 
Brandon369 said:
What does Mf mean?

-Brandon
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It is a somewhat antiquated term that means "Martensite Finish". It is the temperature at which the martensite transformation is, in theory, complete. It is below room temperature for complex steels, requiring a cold treatment to compete the martensite transformation, and is the best reason to employ sub zero freezing, to complete the quench. But to work properly, it needs to be used as part of the quench, not days later. And the benefits are pretty much limited to increasing the % of martensite. I think it is good for smaller blades in steels such as D2 and stainless.
 
Kevin R. Cashen said:
ask my wife and she will tell you that I have no sense of humor. Well that is not exactly true either, she would most likely say that I have one but it is so twisted and strange that most would not recognize it as one:(.
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This is actually kind of true. It is funny to watch Kevin tell a joke. But not really because the joke is so funny...


*geek*
 
I don't think the standard Mf goes that low (-100°F). The higher alloy steels have a large percentage of transition metal carbides that can cause charge abd size deficiencies that can create lattice dislocations and vacancies. This may disrupt the Martinsite transition as it sweeps through creating strain shadpw areas where the steel remains Austenitic.

The cryo process helps change the retained Austenite to more Martinsite abd creates small secondary carbides-generally FeCs. Doing 2-3 temperings will also transform the retained Austenite.

For a good overview of the effects of cryo on tool steels, not published by a cryo company, read through the following article:
http://www.airproducts.com/NR/rdonl...019GLB.pdf#search="cryogenic quenching steel"

I have posted this link before, but since the topic keeps returning, here it is again.

I did cryo treating on tool steel blades for years, but based on this articles info, have given it up. One of the reasons I like working with A2 and D2 is the fact that they both peak in impact strength at HRC 60, which gives a nice combination of edge retention and toughness. In the tests done with cryo cited in the article above, the A2 did not show an impact strength peak at 60, but was lower.
 
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