cryo hardening

[skinner]

Has anyone tried this where they freeze your parts and make them harder, Im sending a set of the Donny cases down to try they say it will be 40% harder for 250.oo would be good for 6 series alum.This new tech stuff is cool Im thinking of putting a set of these in second of eds frames. would be a really nice and rare bike

[Donson]

I have heard of it, but had no experience with it.
I am wondering if it will make the castings more brittle?

[skinner]

dont know but gonna find out Case maker says give it a try Ill let you know

[DarthRider]

dont know but gonna find out Case maker says give it a try Ill let you know
Wayne, I think it's an aerospace process using liquefied O2 or something. And I think I recall Jon Minonno saying something about it related to his drag bikes.
Let us know what you find out!
Wish I could still just pick up the phone and call Ed...

[JCsman]

Operating from memory here (Danger warning - that's an increasingly unreliable source:099:).

We've all seen pics of a crystal or other structure. Nice, neat, uniform. The metal matrix is similar, except, some of the nice, neat stacks are tilted, twisted, misaligned. That weakens the entire structure of the part. The cryo process, as I understand it lowers the temperature - slowly - to near absolute zero. Likely uses liquid hydrogen if that absolute zero part is right.

The "vibration of molecules slows and as the part shrinks in the cold, it tend to stack more tightly and efficiently. IOW any microscopic misalignments are corrected. Raising the temperature - again slowly - does not introduce any of the original issues. That would seem to mean the brittleness should not be a problem.

I recall a report on this years ago where they put a razor blade through the process. IIRC some dude was still shaving with it five or six times longer than his usual razor.

[JCsman]

Dang it.... insufficient memory failure (AGAIN).

I just HAD to look this up. In steel the cryo process (minus 300 degrees F, so liquid nitrogen) transforms some of the carbon in the steel from a soft to hard form, "transforming soft retained austenite to hard martensite".

Man, it's a good thing that wasn't on the test.

[DarthRider]

Dang it.... insufficient memory failure (AGAIN).

I just HAD to look this up. In steel the cryo process (minus 300 degrees F, so liquid nitrogen) transforms some of the carbon in the steel from a soft to hard form, "transforming soft retained austenite to hard martensite".

Man, it's a good thing that wasn't on the test.
But aluminum is as you described? Any downsides you know of?

[JCsman]

But aluminum is as you described? Any downsides you know of?

Well, the aluminum would not have the carbon inclusion factor.... hmmmm .... could my memory have been partially right? Dang it. Back to the NET!

[JCsman]

Hey, I was in the ball park... from an article involving cast aluminum.

http://www.cryotron.com/thermal-stress.htm

As cast parts cool... there are " thermal stresses placed on the internal matrix of the part. ... there is also the stress and tensions put onto the parts by machining as well.

Because of the fact that ...casting parts ... have different cross section thicknesses, the different cross sections cool at contrary rates. Of course the exterior of the object cools before the internal does as well. As the thinner sections cool and solidify, they begin to contract, the larger sections still being in a slightly molten stage will give way to this contraction. However, by the time the thicker sections begin to cool and contract, the thinner sections are already in a solid state with no room to give way to contraction of the larger sections. Naturally, this will not hold the larger sections back from completing their cooling effect. The contradiction of the two sections ends up leaving the material with significant residual stress. This is in addition to the thermal stress created through different cooling stages from external to within the object.

So what does that mean?

It means that on a molecular level there is an imbalance of proper mechanical structuring between the molecules creating, not only a weak spot, but a potential danger point. You can think of this stress spot as the weakest link in a chain, or a couple bricks missing in the wall, but no matter how you look at it, this stress point will be where the first signs of stress failure will begin to happen.

How do you remove these stress areas?

...a cryogenic process – otherwise known as cryogenic tempering – will properly relieve the underlying residual stresses by relaxing the molecules into a uniformly distributed pattern; creating a tighter bond between them. This in turn increases tensile strength prevents distortion in heated parts and closes the grain structure. Cryogenics however is not just a surface treatment and will relieve stress throughout the part."

Should be one of those rare win-wins. Less brittle, yet harder.

[DarthRider]

Bill I actually followed & understood that!
When I was with Union Carbide Chemicals & Plastics we shipped anhydrous (water free) ammonia in aluminum rail tankcars. We had to used "quenched & tempered" material for the tanks, else the ammonia would cause stress cracks in the aluminum shells with ultimate failures.
I wasn't in the technical end of that but I bet it was cryogenic tempering.
From the part of the business I was involved with I know those Q&T aluminum cars were very expensive!