Cryogenic Treating

Cured my '99 Suburban rotor wear problems with a cryo treated pair of rotors.

And the science behind it seems solid.

I'm not familiar with it, but would like to hear more about it. This might make a good blog entry for CR4's Automotive Blog. Feel like writing something up?

That sound's OK to me. I don't want to come across pushing what we do, but simply want to spread the word, explain where it does work, i.e. what materials and reasonable expectations of the strengthening and stress relief deep cryogenic treating achieves. Thank you for the suggestion. Dave, dkimmel@300below.com

I once had some carbide engraving cutters cryogenically treated. Apparently the cryogenic treatment alters the structure of the micrograins, strengthening them considerably. I didn't have time to do a proper trial & the results were inconclusive, but I do recall one cutter lasted 10 times its normal life.

We braze 316 stainless and Inconel assemblies in a high vacuum autoclave so as to prevent many if the negative consequences of welding. Concentrated localized stresses being just one. Alteration of the material properties being another.

It never occured to me to use cryogenic temps to stress relieve parts but to my gut-level self, it makes sense.

As for altering the molecular structure at the material, I'd want to see more concrete evidence.

Fascinating.

Thanks much for the heads up. . . . . I'll dig some more!

Laughing Jaguar

If I can be of assistance, more info, etc., Dave, dkimmel@300below.com

Hi,

cryo treatment has 2 (may be more ?) consequences:

A:

in martensitic transformation at hardening of iron - carbon (+ chromium and other elements) alloys there is a 5 to 10% of austenitic material remaining that is slowly changing into ferritic or martensitic structure thus giving rise to material dimensional instability.

See: Marshall, Maringer: Dimensional Instability, Pergamon (early 70ies out of print now).

or

Bernst: Werkstoffe des wissenschaftlichen Instrumentenbaus (in German)

At cooling down this transformation will be complete within minutes and precision parts will not change much: gage-blocks are treated by this procedure since Johanson invented these 1890 or near that year. Precision ball-bearings (not the ordinary ones) and other precision equipment too.

B: on cooling down and warming up again very often this is done too rapidly thus introducing thermal distortion and related stress-distribution. If ultimate shear strength is reached there will be plastic deformation. This is beneficial if large internal stress is relieved but this is no good if additional internal stress is generated after stress-relieve heat treatment. Allowed cooling and heating rates depending on materials properties as function of temperature: who knows these? So measure if you have to be sure.

May be you encounter the worst case at low temperatures: total embrittlement and cracking to pieces.

Many materials are not suited for cryo use.

RHABE

Very good observations and you are correct. Cyrogenic treating benefits only the appropriate material, primarily higher carbon steel, alloys and carbide. For other metals, lower carbon steel, aluminum, etc, stress relief is the primary benefit. There has been experiments on everything from condoms to nylon stockings, but no real benefit there, just the novelty of having been to minus 300F. And also your comments about the very carefully controlled cooling down and raising back up of the material is dead on. Not only does the material have to be sloooowly and in a controlled means cooled and brought back up, but to achieve the true benefit of cryo treating, material needs to be held at Minus 300F for 24 hours. Dave. dkimmel@300below.com