Knife in freezer?

No, It was not unreasonable.I just held off to start with because in several related threads lately it has descended into a less than friendly exchange of opinions and information.This one seemed to be cruising along nicely,so I added my thoughts.

Mike - It was reactions and comments like yours that I was trying to avoid.I didn't think waiting to reply for 12 hours was chickensh#t.Sorry to have ruffled your feathers (bad pun).

This thread has now been shifted from a discussion of metallurgy to being hijacked for personal feelings.That is what I was trying to avoid.
Stacy
 
Some of you guys are old enough, like me, to remember when we were developing the oil fields in the arctic.

The workers had problems with large steel tools, for example tongs for handling drill rod, breaking suddenly.

Their heat treated and tempered tools broke because of the below zero temperature in the arctic. If the tools had been periodically heated to 2 or 3 hundred degrees they probably wouldn't have broken.

Points out 2 things to me.

1.Dropping the temperature drastically of a piece of steel that had been previously heat treated but not cryo treated will/may cause brittleness.

2. Any scientific study on cryo treatment always advises strongly to temper the steel after cryo.

That's why I said that if the oil tools had been tempered again after exposure to below zero temperatures that they might not have broken.

It won't hurt your knives to boil them in water every twenty years or so if you keep them in the freezer.:jerkit:
 
Here's some data I gathered yesterday. I was making a knife out of 440c, and this thread gave me the idea of seeing if the (home) freezer does anything. So I soaked the knife at 1875 for 5 minutes, quenched in oil, and when it cooled to ambient temp I checked the hardness. It was 59. Then I stuck it next to a frozen chicken for about 15 minutes (till it got as cold as it would). let it warm back up to ambient temp, hardness was now 60.5. Tempered it at 350 now hardness is 58.
I think the freezer did transform some austenite (at least if hardness readings are anything to go by), but multiple temperings would probably do the same thing. I'm going to try it with another knife sometime and see if it works.
 
now on the tempering thing do i hear that maybe if i temper my blades after cryo more then the 3 times i do now that could make them better
right now im doing cpm3v 3 x2hours at 1000f per crucible might i be missing something by not doing 6x30 min at 1000f the kiln is already hot so its just time then
just a though/?
and multi frezze i can do that too if it would be worth while
butch
 
Butch, I think 3 tempers are enough. If Crucible thought they could get significantly better performance from more tempers I'm sure they'd say so. Even one temper is enough, for most high alloy steels, but you have to temper it for a much longer (10+ hours) time.
 
My experience and observations have shown that there is a point of diminishing returns, so I rarely temper more than three times. Mind you, I work with simple steels and really suffer no loss in hardness overall, but consistantly see a "leveling" effect from tempering. I achieve full hardness from the quench but will get a deviation of rockwell readings across the surface of the piece. As quenched this deviation can sometimes be as much as 1.5 and rare occasion 2 points. After the first temper the, average hardness obviously drops a bit but the deviation also drops to within 1 point. After the second temper it is less yet, and by the third time the deviation is so small as to not bother me at all (less than .5).

After observing this on every piece I have tempered and tested over the years I have developed the following schedule for tempering- after quench I temper for 35 minutes at 400F (I use salts, ovens will require longer to reach temperature), check the HRC, bump the temperature up in accordance with the hardness humbers to go for the desired final hardness, and then temper again for 35 minutes. I have found that 20 degrees often will equal around 1 point rockwell with my set up and the steel I work. Check the HRC, if I am at the hardness I desire I then put the piece back in for a full hour or more and call it good.

Doing this some steels like 1095 or some O1 will still have a slight deviation , but nothing to worry about. My O1/L6 damascus, however, will be so consistant that variations are nill, I only mention this because of the still prevailent notion that one cannot rockwell "damascus" (like all damascus is the same). I always get a good chuckle form such a statement because my pattern welded stuff actually rockwells better than my monosteel:D
 
bladsmth said:
........

Mike - It was reactions and comments like yours that I was trying to avoid.I didn't think waiting to reply for 12 hours was chickensh#t.Sorry to have ruffled your feathers (bad pun).

This thread has now been shifted from a discussion of metallurgy to being hijacked for personal feelings.That is what I was trying to avoid.
Stacy
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Stacy, you wanna see why my feathers got ruffled? Look in the mirror. The "old timers" around here noticed long ago that the Great Oz Apelt had a habit of coming late onto a thread and paraphrasing the info that had already been given. You repeat what's already been said, as if now that you have given it your all-knowing seal of approval, we could finally rest easy that what was said could be trusted because Stacy agrees. It's happened so many times that it gets spoken of behind the scenes. Tain't just me, so all of us cain't be wrong.

It brings to mind that little bastid that everyone will remember from grade school. The one that never raised his hand until the teacher was already pointing elsewhere; who at the last moment started furiously waving like he'd been overlooked. If the responder was wrong, there'd be a snigger but the little chickensh*t wouldn't raise his hand and take a chance anyway. If the responder was correct, there'd be an affirmation, "That's what I was gonna say." I hated those little wankers who didn't have the balls to be wrong but always wanted on the glory train, too.......:barf: :barf:

Sorry to hijack the thread with that personal attack, folks, but it felt good to finally say it. It's gnawed at me for a long while. Brought out that aggressive little street kid in me that I often regret, but not this time.

This is my swansong. Odd place in the forum to say goodbye, on someone elses thread. Sorry about that, Vasilli, and the rest of you. Rest assured it won't happen again.

Life is changing and it's time to move on. I'm many things, and jerk is high on the list. Doesn't take a rocket scientist to see that's evident again, eh? LOL :jerkit: I've tried to help folks, though, and I've tried to make some laffs. I think I've done a little of both, and have enjoyed it immensely. Along the way I've displayed the bad side of me often. Sometimes I've even felt bad about it :rolleyes: ; I'm not afraid to say I'm wrong and apologize, though some have not deserved it when it was given. I've made some good long distance friends, too. I will always cherish you guys for the joys you brought to my very small life. Thanks!

Those who are to come along and take a shot at me, try to be novel in your comments so it provides some comic relief for everyone else. ;) Don't just be a little wanker that jumps on the dogpile after the bear's already held down......

Via con Dios, amigos. It's been a slice...................:D
 
Don Robinson said:
Some of you guys are old enough, like me, to remember when we were developing the oil fields in the arctic.

The workers had problems with large steel tools, for example tongs for handling drill rod, breaking suddenly.

Their heat treated and tempered tools broke because of the below zero temperature in the arctic. If the tools had been periodically heated to 2 or 3 hundred degrees they probably wouldn't have broken.

Points out 2 things to me.

1.Dropping the temperature drastically of a piece of steel that had been previously heat treated but not cryo treated will/may cause brittleness.

2. Any scientific study on cryo treatment always advises strongly to temper the steel after cryo.

That's why I said that if the oil tools had been tempered again after exposure to below zero temperatures that they might not have broken.

It won't hurt your knives to boil them in water every twenty years or so if you keep them in the freezer.:jerkit:
Click to expand...


There is some serious misinformation on the net. I have some great 440c & 12c27 knives that were custom made and after hardening in oil left in the freezer over night. It does improve the conversion from Austenite to Marsteninte but needs to be tempered properly afterwards.

Cryogenics generally has a bad name in cutlery. With Carbon steel the tolerences are broad with a reasonable distribution of performance. So if after quenching you choose to dunk it in liquid nitrogen for a day then the chances of all round improvement are better than even. Carefully controlled and one can expect a all round improvement. Transpose the liquid nitrogen dunking to Stainless and you can get small pieces through to mediocre performance, with rare all round excellence. Stainless has a very narrow window of Sub zero treatment to achieve performance without brittleness.

I have not had the experience of dry ice and acetone.
 
Kevin R. Cashen said:
Well, as has been pointed out on this forum, there are a couple hundred degrees difference from cryo and the kitchen freezer. Extremes of that magnitude should be well enough below Mf to beat the snot out of any retained austenite. But that is all I will say about the cryo since there seems to be an organized P.R. push by the guys selling it these days and the slightest touching of the topic can start another sales pitch... oops:foot: I guess I am capable of letting some of those opinions slip out occasionally;) .
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nouph said Kevin .. thanks :)


Tim-Gabz said:
Transpose the liquid nitrogen dunking to Stainless and you can get small pieces through to mediocre performance, with rare all round excellence. Stainless has a very narrow window of Sub zero treatment to achieve performance without brittleness.

I have not had the experience of dry ice and acetone.
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well I'm not sure if I should agree or disagree :confused: I may have miss interrupted what you said..
where Most heat treatable SS was designed to be Cryoe'd in the first place..
if you bend most any SS before it's
Heat treated you'll find it will break anyway with at least ~ 1/8" and up
so the heat treat for SS is for all benefits other than bending. IMHO
I believe SS has more benafits from super cold..then does the simple steels

just how much seems to be the thing..
 
Kevin:

Is there a range of temperatures where the cycling would be most effective?

Here's a hypothetical example: would repeated cycles from a tempering temperature (let's use 400 F as an example) down to -100 F have more of an effect than cycling from room temperature, say 70F down to -430, even though the temperature spread is the same?

George
 
gspam1 said:
Kevin:

Is there a range of temperatures where the cycling would be most effective?

Here's a hypothetical example: would repeated cycles from a tempering temperature (let's use 400 F as an example) down to -100 F have more of an effect than cycling from room temperature, say 70F down to -430, even though the temperature spread is the same?

George
Click to expand...
I'm going to butt in..
where you can't get that cold unless you use helium I'm not sure but it's an unfair question using this hypothetical example..it was thought that using helium would have a benafit if it' wsn't for the cost of cooling with helium..but I see your point,
 
What I get from you guys is that I should keep it in owen for some time also...

It already has cocobolo handle:

knife-83-015.jpg


So what about frying some sand on a pan and then stuck blade in it? Or may be Iron blade?
-----------------------------------------------
About repetitive heat treating:

Anosov write about so called "bulat variant" when regular steel is heat treated many times it make it same as bulat - wootz. Same what Achim Wirtz write aboyt 100 HT cycles when carbides migrate to vanadium structures...

http://playground.sun.com/~vasya/Bulat-Achim.html#English

Will it help if HT carbon steel 50 times or more?

Thanks, Vassili.
 
Dan:

Hmmmm. . . Okay, I'll ask a different question completely to avoid unrealistic temperature ranges. Is there a benefit to cycling down from tempering temp to subzero instead of room temperature to subzero?

This would mean you would heat the part up again to tempering temperature after cooling and then cool again, etc.

George
 
fitzo said:
Odd place in the forum to say goodbye, on someone elses thread........Via con Dios, amigos. It's been a slice...................:D
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Am I the only one that caught this ?? Tell me it ain't so Mikey.......... You can't do this to us you old far-toid.

Take deep.......deep breaths then come back and play.

Robert
 
The Martensite transition is a diffusionless shear (that is a physical transformation without chemical reaction) that progresses through the Fe-C system at around 1Km/Sec. Retained Austenite probably occurs in several different locations during this process. Lattice dislocations, lattice substitutions and vacancies can all create "strain shadow" effects in a crystal. A lack of proper soaking time, leaving remnant Carbide crystals can be a good example of something that will create strain shadows.

For the high alloy steels like the tool steels, the increased temperature will allow most all of the common transition metal carbides to dissolve with proper soaking time. Only Vanadium Carbide has a dissolution temperature over 1900°F. It is neccessary to soak for the full time to get the effects-no cutting down because you think it is thinner than the specs say for 1 inch steel. That soak time is after heating through.

The reforming of carbides after soaking is a diffusion controlled reaction and does not proceed at anywhere near the speed that the Martensite transition does. I like to quench the tool steels as fast as possible and getit into cold treatment ASAP in order to keep the size of carbides down as much as I can. Tempering relaxes the strain formed by the trapping of Carbon in the lattice and allows it to form carbides along with transforming the retained Austenite.

One thing that quenched materials all have in common is that they are metastable at best. Over time the material trapped in between the lattice sites will migrate and diffuse to form the stable phases at the PT conditions where they exist. Martensite is a metastable quench product where the lattice has frozen into BCC (body centered cubic) and BCT (body centered tetragonal) structures that are both a bad fit with the interstitial trapped Carbon. Steel has a known ability to age over months and years, even at room temperatures to a less hard condition. If you leave it in your freezer for a few months, it will lose retained Austenite and the BCT will tend to relax to form BCC structures. Presumably this will toughen and "temper" the steel.
 
I'm almost afraid to post anymore comments and opinions,but what the he!! .

Phillip - I think a bit longer soak time is needed for 440-C. I would suggest 10-15min.at a minimum. If not long enough the carbides will not be completely dissolved and distributed. It can create hard spots and "veins" of carbides in the blade.

Vasilli - Once the handle is on, any attempt at tempering would ,most likely ,ruin the handle.Whatever method you used to heat the blade would conduct up the tang and destroy the glue and probably the wood,too.

Mike - Sorry to see you go.
Stacy
 
bladsmth said:
Phillip - I think a bit longer soak time is needed for 440-C. I would suggest 10-15min.at a minimum. If not long enough the carbides will not be completely dissolved and distributed. It can create hard spots and "veins" of carbides in the blade.

Stacy
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Stacy is right. 5 minutes soak is certainly not enough.

The Timken Latrobe data sheet for 440C recommends a soak at austenitizing temperature for a minimum of 30 minutes, regardless of thickness or size.Up to an hour won't hurt the steel unless the temperature exceeds the maximum recommended.

Strangely, Crucible's data sheet for 440C has been missing off their web site for months.
 
bladsmth said:
I'm almost afraid to post anymore comments and opinions,but what the he!! .

Phillip - I think a bit longer soak time is needed for 440-C. I would suggest 10-15min.at a minimum. If not long enough the carbides will not be completely dissolved and distributed. It can create hard spots and "veins" of carbides in the blade.

Vasilli - Once the handle is on, any attempt at tempering would ,most likely ,ruin the handle.Whatever method you used to heat the blade would conduct up the tang and destroy the glue and probably the wood,too.

Mike - Sorry to see you go.
Stacy
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The data sheet I was using recommended 5 minutes, and all the ones I've seen warn against over soaking. (Just talking 440c here.) 440c doesn't really have much in it to inhibit grain growth, like vanadium.
I might go 10 minutes next time and see what happens.
 
Don Robinson said:
Stacy is right. 5 minutes soak is certainly not enough.

The Timken Latrobe data sheet for 440C recommends a soak at austenitizing temperature for a minimum of 30 minutes, regardless of thickness or size.Up to an hour won't hurt the steel unless the temperature exceeds the maximum recommended.

Strangely, Crucible's data sheet for 440C has been missing off their web site for months.
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Shoot, I think it's time for another experiment. I've got some scraps of 440c. I'm going to soak them for various times and see if there's any difference. Not that I don't believe you, I just want to see for myself. :D
Also, I think we're getting a little off topic here. I'm going to start a seperate thread for this subject.
Crucible also doesn't have the data sheets for L6 and o1. :mad:
 
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