Temper has its origin in the old english word Temprian, with the meaning "to modify some excessive quality; to restrain within due limits" Temprian comes from the Latin word Temperare, which means "To mix correctly, moderate, regulate, blend"

Sorry. I've just got an arguing problem :P

Problem is, we're agreeing instead of arguing. Or maybe that's not a problem. :D

What can dry ice and acetone do for 51XX?

Homeshow,That has pretty well been covered in this thread. If you make and test your blades using the steel makers recomendations the steel will work as it is intended. Some steels as mentioned above benefit from cryogenic treatment. 

The most impportant thing a new maker can do is establishh aproper hardening and tempering protocol sheet and follow it to the letter. And keep in mind that sheet will only work if yoiu know the exact steel yoiu are using. And that sheet may only work for that one particular type of steel.

What can dry ice and acetone do for 51XX?

maybe nothing but it will get it to -170F.   If you have 5110 wont do much from any heat treating, 5160 it might.  What do you have ?  You have asked various questions about 151XX ,  but never state the actual steel you are using.

 

51xx is a series short hand we use , but you are asking a few specific questions that can only really be applied to a known steel, not much of an answer is available for a potentialy broad carbon range.  With a little more reading plus more accurate questions, it could lead to more detailed answers for your steel what ever it is. So basically the xx means nothing.

Leaf spring off of a mid 90 jeep. No I can't afford store bought steel, really. So I have 2 6ft. Pieces of leaf spring and no seriouse knife makers around here.

Lie Nielsen has been using a double tempered chryogenically treated a2 for his plane blades for 10 years or so.  It outperforms any blade material I have ever used, it terms of edge holding and chip resistance. More anecdotal evidence, to be sure, but I have tested their cryo blades against anything I can find. Cutting full width .003 shavings from maple, it provides twice the life of non cryo a2. I will leave the "why" to the more knowledgable

We use  a dry ice slurry (-109*) on complex and stainless steels..Basically like everyone else said it turns RA into MA..Its cold enought to do this..There is a lot of talk and subject about carbides and LN treatment..I dont have a dewar or Id use just for the fact that I wouldent have to buy dry ice everytime we heat treat..Though we get the same gain in hardness from dry ice slurry as cryo (I know Ive seen the RC tests)..What you dont get is the somewhat controversial "nano carbide" formation etc.Now im not knocking LN or even saying dry ice is as good but I am saying dry ice does a fine job at converting RA,,.

 The RA is the big deal..RA is a bad thing in complex steels..Its part of the reason you hear stories about some D2 taking such a crappy edge and chipping..There is a big diffeence in heat treating a blade and heat treating a press die..RA is fine in a die, but its awful in a blade..

Lie Nielsen has been using a double tempered chryogenically treated a2 .., it provides twice the life of non cryo a2. I will leave the "why" to the more knowledgable

The "why" has already been explained in this very thread. More than once. Multiple times, even.

The "why" has already been explained in this very thread. More than once. Multiple times, even.

 

My apologies, It seemed that there was a less than complete understanding. MY experience is there is more than a minor improvement in performance.

we can post it, but if they wont actually read it, it wont help  :(

You got that right, Brother Sells. Horses. Water. We'll just drown 'em if we say "retained austenite" too many times. :rolleyes:

Hmmm. I didn't think dry ice was even close to cold enough to break down the crystal boundries that weaken hard steel. It's been a number of years since I looked into cryogenic "hardening", tempering is a much more correct term as of then. The severe shrinking as the part is chilled crushes the crystals obliterating the crystal boundries that are the inherent weak points of initiation for failures. The same basic thing as a cold shut.

 

The first place I recall hearing about cryogenic heat treatment was aerospace parts Dad used to make. We tried dry ice in alcohol or oil but it was no joy, not cold enough to do the job so he had to pay for proper cryogenic treatment. Before manufacturers figured out how to make amorphous castings, mono-crystal, they had to cryo-treat things like turbines, rocket nozzles, etc. or the normal crystal structure, (grain) would cause them to fail in use.

 

Okay, that's about what I remember from a loooong time ago and I haven't read anything about cryo treating blades that makes me thing something else is going on. Without crystal boundries weakening the steel it allows more acute bevels and sharper edges because they're stronger. Not harder, stronger.

 

When I first heard about cryogenically "hardening" blades I thought they were talking about quenching from critical in LN or L Helium. I really REALLY wanted to see this in person! After the internet went public I was able to research it and lost interest in the process as a spectacle. Besides the really cool explosion of nitrogen or helium when someone dropped a piece of oh say 1,700f. steel in a beaker, I had a lot of trouble visualizing the steel surviving such a rapid chill.

 

Turns out there was no cryo chill involved at all, it was a superior tempering process, FAR superior.

 

Frosty The Lucky.

What the heck. I've got enforced down-time. May as well spend some composing exposition.

My apologies, It seemed that there was a less than complete understanding. MY experience is there is more than a minor improvement in performance.

YOUR experience is with high alloy steels. (Said so yourself. Said "A2.") YOUR experience is with much greater amounts of retained austenite than OTHERS might have when using the lower alloy steels.

 

A2, D2, and other high-alloy steels have much lower martensite finish temperatures and much greater degree of retained austenite than simple steels. The extra cold after the initial quench (call it an "extended quench" or "tempering" or call it "Bob.") converts this retained austenite to more martensite. Very little improvement with low alloy steels. Lots of improvement with high alloys steels.

 

For more education on the effects of alloying elements in steel, their effect on the eutectoid, Ms, and Mf, as well as "what cold does to steel," read George Krauss'  Principles of Heat Treatment of Steels.

 

What's that I hear? Horses drowning? Oops.

 

Hmmm. I didn't think dry ice was even close to cold enough to break down the crystal boundries that weaken hard steel. It's been a number of years since I looked into cryogenic "hardening", tempering is a much more correct term as of then. The severe shrinking as the part is chilled crushes the crystals obliterating the crystal boundries that are the inherent weak points of initiation for failures. The same basic thing as a cold shut.

Now this is a new one to me. I'd like to learn more about this. Frosty, Can you steer me toward any articles or books? I am, of course, familiar with recrystallization due to nucleation on heating to Ac, but had not before learned of this crushing effect. Sounds interesting!

I'm afraid the sources are gone with the birch I remember reading on recommendation from knife guys on The Forge list years ago.

 

I'm afraid my memories will have to go in the anecdotal catagory now. I remember the discussion and the sited material, just not who or where. <sigh>

 

Frosty the Lucky.

Thanks anyway, Frosty. I'll just have to see what I can dig up on my own.

The pompous sanctimony and self adulation aside, there is so much good information available here. Sometimes I think I might drown in the condescension though

The pompous sanctimony and self adulation aside, there is so much good information available here. Sometimes I think I might drown in the condescension though

Amen brother.

In retrospect, my choice of metaphor was inadequate social judgement. I apologize for not expressing my frustration more permissibly.