View Full Version : 5160 Cryo ??


MongoForge
05-10-2003, 11:07 AM
Would it be worthwile
to Cryo-treat 5160 ?
Or is it not worth
it in low chromium steels ?

Thanks
Mongo-

Jerry Hossom
05-10-2003, 01:17 PM
It's my understanding that Cryo improves most steels. It helps eliminate retained austenite.

Misque
05-10-2003, 09:10 PM
I read in Ed Fowler's book "Knife Talk" where he and Rick Dunkerley cryo'd some 5160 and got some very impressive test results. Their test blades averaged 132 cuts in 1 1/4" manila rope. After cryo, the blades averaged 270 cuts.:eek: Then they flexed the blades and got one to bend 110 degrees without cracking.:eek:
Judging by their results, I'd say it definately helps.


All the best,
Mike U.

MongoForge
05-12-2003, 04:33 PM
Thanks for the replies,
i really appreciate it..
Mongo-

Daniel J
07-03-2003, 03:54 AM
Hmmm... There seems to be a bit of controversy when it comes to 5160 or other low-alloy steels. The folks at swordforum (http://forums.swordforum.com/showthread.php?s=&threadid=21525) seem to have come to the consensus that if a HT is done properly, cryro will give no noticable benefit (read the Tinker's comment at the bottom of the page.)
Mike, what was the HT process used for those blades? Gas heat to non-mag/warm oil quench?

RPatton
07-04-2003, 07:41 AM
I cryo everything.......

At least everything that I can cram into my tank. The rest I stuff into my freezer. Even if its not doing anything, and I do believe it does, it makes me feel good. ;) Cold cycling seems to help sharpen definition and contrast on a temperline (other makers hold to this) too.

Personally, I think cryo will maximize any steel's potential.


Rob


PS: A benefit doesn't have to be noticable to be a benefit...... :)

Jerry Hossom
07-04-2003, 09:26 AM
If I had to figure out how to cryogenically quench something that was over three feet long, I'd probably spend at least half my time rationalizing why it's not necessary. :)

There's a whole lot of emotion surrounding this, especially in some of those posts on SF. Fact is, I seriously doubt anyone knows everything it does and how. There's a whole bunch of conflicting information on the subject, except on one scorecard that matters a whole lot. If you do it, blades seem to perform better. I seriously doubt completing the martinsitic transformation is all there is to it. Does less than 1% retained austinite explain the observed performance differences? And how do you explain the observed perdformance differences that result from cryo AFTER tempering or on untempered steels?

The problem needs to be examined in the sole context of what blades do and need to do. Metallurgical explanations in a vacuum of application relevance are pretty meaningless. At the same time, cryo will not compensate for other flaws in the process, blade geometry, edge geometry, fundamentally bad heat treating, etc. Frankly, my instinct is that if cryo doesn't improve your blades, something may well be wrong elsewhere in the process. I don't believe in mysticism, that some makers have a magical process that results in perfect steel.

I did find this statement posted in the SF thread very intriguing.

"For all but very high alloy steels, the effects on hardness and wear-resistance is neglibable, and the tiny amounts of retained Austenite create small random stress distributions that have no practical impact except to make thermal expansion somewhat inpredictable, which makes some sense in the context of gun barrels, but not swords."

I think the observed/predicted effect is likely correct, but the conclusion that it would have no meaningful influence on blades is suspect. "Small random stress distributions" would IMO have a very major bearing on blade steel, both in its edge holding and its inherent strength. I'm of the opinion (only mine) that the major source of dulling in a blade is the result of micro-chipping, cracking, edge deformation, and maybe other forms of physical deterioration that have nothing to do with abrasive wear, which is what steel companies publish when they cite numbers for wear resistance. The above statement is consistent with what you would read in steel company literature, but not consistent with how blade edges are in fact shaped, used, and ultimately deteriorate. A blade edge has zero tolerance for internal stresses of any dimension, or any which might be induced by the finishing process. Any such stresses will lead to failure, whether they are the result of the steel's manufacture, its heat treating, or (most commonly) its shaping and finishing. Small stresses lead to bigger stresses which lead to structural failure.

That's my take anyway.