cold weather steel?

[xdshooter]

Cobalt, the cryo transformation of retained austenite to martensite does not significantly increase the strength or flexibility of the steel. It increases the hardness and wear resistance, and I would doubt that very much austenite it retained in busse knife steels. They are not cast, and they are probably quenched to achieve a small grain structure in the first place.

Also, chopping ice is not the ultimate test of a knife in the cold. Ice is chopped to reach water underneath. I am very sorry to break this to everyone, but when you can reach the water underneath, it is not, and has not been, cold. Our friends from Canada are much more experienced, but real cold (in my opinion) starts at -20 F. That is when everyday tools and machines start to "feel" the effects.

 

[hardheart]

http://www.airproducts.com/NR/rdonlyres/3433A3DC-1899-4093-A094-9964342C38C0/0/33005019GLB.pdf

no grain refinement

 

[Cobalt]

Cobalt, the cryo transformation of retained austenite to martensite does not significantly increase the strength or flexibility of the steel. It increases the hardness and wear resistance, and I would doubt that very much austenite it retained in busse knife steels. They are not cast, and they are probably quenched to achieve a small grain structure in the first place..

what does this have to do with the price of tea in china, that is not what we were even argueing about. We all know that it increases hardness and wear resistance. By the way Busse DOES Deep cryo the knives and that kinda kills your last two sentences.

quenching is such a dirty word

so you have seen the effects of cryod knives versus non-cryod and have experience no difference?

 

[knarfeng]

The info is so common knowledge that you can find it if you search long enough in the right sources or talk to the right people.

Mete, I am actually very surprised at your response, since you have been here long enough and in enough discussions about this stuff that I cannot believe you came out and contradicted, but since you have been here a while I will let you explain after some research why in your opinion there is or there is not.

maybe you can resurrect Cliff to explain it.

Well since mete is a metallurgist I do not think he needs a physicist to correct him.

Here is a better explanation than I would give as to what you have to do to "refine the grain structure". (I'm just a materials engineer, not a metallurgist. I deal with these things, but I don't know the theory well enough to give this good an explanation.)

http://www.bladeforums.com/forums/showpost.php?p=5238327&postcount=2

The third paragraph is especially to the point. I added the fourth paragraph to emphasize that you have to heat the alloy to affect the grain structure, rather than ultra cool it.

First of all, you need to realize that you cannot shrink or “break up” the existing grains, that is just bad terminology and understanding by bladesmiths. What you can do is make new grains that more closely fit your tastes. There are two ways to make new grains, you can transform the austenite into another phase and then back into new austenite grains, or you can induce spontaneous recrystalization through deformation. The latter could be handled by heavy forging as the billet drops to below recalescence (critical).

Simply cooling the billet in the air until the magnet sticks again and the reheating to a reasonable temperature, say 1500F will completely remake the grains within the steel, repeating this process without exceeding the grain coarsening temperature will continue to reduce grain size. The process can be accelerated by reducing the temperature that you go to and even more so by how fast you cool the steel. I am not an all out enemy of multiple quenching; I just feel that the focus gets taken away from proper normalizing by the hype. I keep a large tube of old oil near the forge to quench into after forging in order to speed up the grain refinement. The driving force behind recrystalization is stored energy within the crystalline system, thus hitting the steel with the hammer or rapidly cooling and reheating the steel will drive it along quicker.

But I completely agree with you that there is no need to use a titanium blade to get good performance at subambient temps.

 

[hardheart]

I wonder if Infi can avoid RA anyway, it probably has a significant amount, and maybe it's marquenched.

 

[me2]

H1 steel, for example, is even more resistant to corrosion than titanium.

Do you have a link for this info? Sounds interesting.

On the topic at hand, cold weather brittleness goes down with carbon content, and INFI has relatively little carbon, so for a bomb proof blade, this may be the way to go. I've heard of axes chipping and cracking when used in cold weather, but even the lightest axe sees more energetic impact than any knife I can think of. These stories were for full size axes, not hatchets or belt axes.

 

[Cobalt]

http://www.airproducts.com/NR/rdonlyres/3433A3DC-1899-4093-A094-9964342C38C0/0/33005019GLB.pdf

no grain refinement

from your article.......

The inconsistencies in reported data may be,
at least partly, explained by a new effect of cryogenic aging
observed to take place in the background of retained austenite
transformation. Meng observed precipitation of fine -
carbides instead of the usual -carbides following -180oC
cryogenic treatments and noted improvements in both wear
resistance and toughness

http://www.metalscience.com/services.php

Grain structure is refined - All of the individual particles that make up an alloy are placed into their most stable state. These particles then are aligned optimally with surrounding particles. Also, molecular bonds are strengthened by the process.

During the process of deep cryogenic tempering austenite is transformed into martensite, which is then then tempered to change into tempered martensite. In addition, small complex carbides called eta carbides are precipitated out. This greatly reduces residual stress and promotes "micro-smoothing" of the surface.

The dramatic improvement in wear resistance in deep cryogenicly treated tools steels, with no loss in toughness is most likely explained by the formation of molecular eta carbides and the formation of fine cementite particles in the final tempered structure. It would appear that the conversion of additional martensite, although often present, is probably a secondary mechanism. This understanding also supports the increase wear resistance in materials that don’t readily form martensite.

The effects of cryogenic treatment on the microstructure were also studied by means of X-ray diffraction and transmission electron microscopy methods. Unlike cold treatment, cryogenic treatment improves the preferential precipitation of fine n-carbides instead of e-carbides. These fine carbide particles enhance the strength and toughness of the martensite matrix and then increase the wear resistance. The formation mechanism of fine n-carbide is discussed.

The microstructure of the martensite after cryogenic treatment and tempering was remarkably changed. In most of the areas appeared fine carbide particles developed in the boundary of twins. In different areas, fine carbide particles appeared at the points, which have a considerable diffusing density. Some rod like carbide particles parallel to each other appeared and varied in size from 5 to 10nm in cross-section and from 20 to 40nm in length.

http://www.knivesby.com/cliff-stamp-grain-cryo.html

http://www.onecryo.com/

Benefits of our cryogenic process include...
Closes and refines grain structures
Reduces retained stresses, wear and surface roughness
Reduces retained austenite, friction, heat & downtime
Increases dimensional stability
Increases durability & production and profits

A deep cryo should be done as part of the tempering process, it is of course not the last step. Besides allowing 100% transformation to martensite it also refines the grain structure and enhances the creation of very high wear resistant eta carbides.

-Cliff

this is just 5 minutes worth of research of what I thought was common knowledge. Please explain to me how all these sources can be wrong, all of you, please do so.

Show me actual tests, micrographs etc....

Maybe you are right and all these sources are wrong, who knows.

 

[hardheart]

why all the quotes about carbide?

and why the quote from metalscience about the entire HT process

 

[xdshooter]

Those articles look like they are written by companies that sell their cryo services. Hardly a glowing example of impartial research.

Also, increased strength from cryo is a claim I have not seen yet. I would like to see a strength strain curve from a knife company. If a knife company is doing cryo to increase wear resistance, I'll give them that.

Burden of proof is not on the consumer either. We as consumers can be skeptics.

 

[xdshooter]

Back to the original topic, I fully don't believe that just because a knife has been to a lower temperature, that it is immune to anything. Using a knife at -40 tests the steel in ways we rarely see. Just because it was once at -4000 doesn't mean it won't be affected.

 

[mark greenman]

Well, just to bypass everyone's arguments, I'd like to sugest the solid titanium icepick by szabo inc for $60 w/ sheath. Its definitley built to last, and is literaly designed for use in ice- hence ice pick. Snag one of those for prying, pounding, ice picking, and grab a fallkniven (f1,s1, a1, ect) for actual cutting chores, and I think you'll be pretty set.

http://www.szaboinc.com/newitems.html
Its most of the way down the page, looks pretty ideal.

Good luck
mark

 

[knarfeng]

I don't consider CS a valid source. He collects data and is good at that. He is a good observer. Metallurgical theory is not his training. Unless he cites his sources, I'll pass.

Much of the rest of your quotes come from promotional literature of folks who perform cryo heat treat. What did CS used to say about accepting promotional items as gospel? The onecryo site has only promotional material.

As for the Metals Science web site, it is not clear that their work on carbides for carbide tipped saws and routers applies to standard steels.

I note that the ASM Handbook, which the Metals Science web site quotes, acknowledges improvement of properties through conversion of retained austenite only. Nothing about grain refinement.

I accept that cryo improves the performance of the steel. That was never a question. I take exception to unproven statements that existing grains are reduced in size.

 

[hardheart]

So in short, it doesn't actually shrink the grains already formed

same link.

 

[znode]

Do you have a link for this info? Sounds interesting.

Rust-proof Steels -- H1 vs. X15 T.N.:

Originally posted by STR:

To me the best way to make something rust really fast is to do the same procedure as anodizing only in COKE or Diet Pepsi and crank up the voltage. I've made titanium corrode and rust this way. Big pits form at 125V and they take on that typical rust color after you clean it off under the tap water rinse.

I've done this same thing with H1 pins left over from ugrades on Salt knives I've rebuilt for forum members and all the pins do is take on a coat that is aluminum gray in color. No rust is evident and no real corrosion to speak of just a thin oxide layer a gray color.

 

[nodh]

I would suggest any knife from Fallkniven www.fallkniven.com
They are developed by people living just south of the polar circle, and up there it can be quite cold. Yesterday they had -25C (-13F) and that is not cold. We even have that in Southern Sweden from time to time.
It would surprise me if the Airforce issued a survival knife that would break when it really needs to work.

ANY knife can break if it gets really cold. Liquid Nitrogen (-196C) might break anything
Unless you are going to Verchojansk in Siberia (about -55C) or Antarctic (lowest recorded -88C) you need not to worry about knife breaking because you need a saw to cut the PB and J.

 

[Cobalt]

same link.

actually the link and his quote were from two different locations and what he says in your quote does not negate the grain refinement. Of course it doesn't shrink grains already formed. I am not speaking of cryo after HT, I am speaking as cryo as part of HT.

I know that many believe that it does not do much. I cannot bring myself to believe that some of the best hard use knife companies out there use it to just gain little to nothing. They believe in the gains and their products have proven it.

 

[Lycosa]

This was a very interesting thread. I did not mean to start a flame war! But I did learn a lot. Thanks everyone. When I posted on page 1: " They all work.", I meant ALL knives, not just titanium. My favorite steel is tool steel! I just personally like the Mission Titanium knife as my "all weather, outdoor knife." It has never let me down and I felt I had to share this information. No hard feelings. All of you have a lot of knowledge and a lot to offer on BF's.

 

[Jared Stenoien]

actually the link and his quote were from two different locations and what he says in your quote does not negate the grain refinement. Of course it doesn't shrink grains already formed. I am not speaking of cryo after HT, I am speaking as cryo as part of HT.

I know that many believe that it does not do much. I cannot bring myself to believe that some of the best hard use knife companies out there use it to just gain little to nothing. They believe in the gains and their products have proven it.

So you're talking about quenching in LN or something? How about you go try that and come back and tell us what happened?

 

[Cobalt]

This was a very interesting thread. I did not mean to start a flame war! But I did learn a lot. Thanks everyone. When I posted on page 1: " They all work.", I meant ALL knives, not just titanium. My favorite steel is tool steel! I just personally like the Mission Titanium knife as my "all weather, outdoor knife." It has never let me down and I felt I had to share this information. No hard feelings. All of you have a lot of knowledge and a lot to offer on BF's.

Not a Flame war at all, at least not on my part. The cryo subject has been around a very long time, proponents say it works, opponents say it doesn't do much and both have their proof, and this is what you see here.

And it was my one little sentence in my original response that started taking this thread off topic. I should have not mentioned anything about cryo.

Titanium is a great metal for outdoor purposes and it is basically rust proof under normal conditions, and yes, you can make most any metal corrode with enough caustic, pressure and temperature. Cobalt based alloys are also good for corrosion, they just do not have the toughness of tool/carbon steel or titanium. I have had many stellite 6k knives and loved them, they just did not have the toughness of a good carbon steel, but in really cold weather they worked well, although I never used one as a prybar.

 

[Cobalt]

So you're talking about quenching in LN or something? How about you go try that and come back and tell us what happened?

No, but you have yet to contribute anything positive here smarty. Why don't you explain what is going on in cryo since you seem to be an authority.:jerkit: