Why "Cryo" anything?

Hi guys...just joined..

Cryo treatment of steel: As steel is cooled to a point below M s , known as the martensite start temperature, martensite will begin to form, it being transformed from austenite.. At M f , a lower temperature known as the martensite finish temperature, all of the austenite will have transformed. This gap in temps exists because the lattice changes that occur stabilize the structure are volumetric ones...austenite is FCC while martensite is BCC...(face center cubic vs body centered cubic.)

Varying the cooling steps and temperatures can force pearlite and martensite to exist together, ratios and relative amount modified by the temp profiles...What is consistent here, is that all the treatments alter the composition at the lattice level. The cryoing of steels, brasses, et al, do indeed cause a re-structuring of the crystal structure, as the strain induced by the lower temps will be reduced by molecular adjustments...some of those adjustments alter the marco physical properties...these changes are used in many areas, such as engine stuff, turbine blades, knives...etc.

Cryoing of copper, however, while theoretically capable of adjusting the crystal lattice (I've not seen this, btw.), will not significantly alter the mean free path of the electrons at room temp (this is the energy loss we call resistance). It will still be at the 3 times 10 -6 regardless..there are no discontinuities caused by grain boundaries, no signal reflections...nada.

A polymer below T g is indeed a solid, and it's TCE is a specific value..for example, E+C 2851 will be about 29 PPM/C. Above T g , TCE will be in the 90 to 120 PPM/C range, and will be in a plastic (soft) state.

At nitrogen temps (77K), kapton and tefzel are still quite flexible, and kapton only at helium temps of 4.5K and 1.8K.

AT 77K, only bisco and yibco are superconductors..too brittle for use yet, and J c (critical current) are not very high, but they are getting better.

Adhesives do not melt at cryo temps..If thin enough, they will be ok, unless they are being used to bond differing TCE materials, for example..copper (16PPM) to aluminum (25PPM), then they will fail in shear.

Adhesives and epoxies that are greater than 20 mils in thickness will crack if they are bonded to a metal, the thicker the adhesive or epoxy, the higher the temp they will fail at.

At the 5 to 10 mil thickness, unfilled epoxies will work and remain quite strong all the way to superfluid helium (1.8 K). However, even by themselves unbonded to anything else, they will tend to craze and crack if they are not cooled down extremely slowly, as the combination of heat capacity and thermal conductivity do not allow high cooling ramp rates.

Jena labs stated "the LN2 is actually much colder than this temperature."...they meant room temp..not below 77K. To get below 77K, they have to pull a vacuum. Not very hard to do, but still requires some horsepower..with helium, a reasonable setup will require several hundred horsepower..some do this with nitrogen, to get measurements at 50K.
"Micro-diodes" do not exist..period.nor does "slow field transverse energy generation"..skin effect is a current slew rate based entity, relying entirely on the radial conductivity of the wire, the geometry of the conductors, internal magnetic field rate of change, and the ability of the surrounding dielectric to charge the internal volume of the conductor with magnetic field. If you are looking for 50 hz signal propagation at 2.93 feet per second, you are looking in vain..

I was unaware silicon could be damaged by cryo..that has not been my experience...you intended to say silicone, perhaps??

Cheers, John

Geoffkait,
Please go through my post again. Cold tempering requires heat treatment cycle. Not cooling from room temperature, which is what's in vogue right now in Audio.

Cello,
Please try to under this. When you make a scientific claim such as DBT testing, the test result must be statistically significant. Otherwise, it's just pseudo-science.

Eric

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John,
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Great post and very informative thank you. Yes, I did mean to write silcone.
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Rgds,
Larry
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Ejliu,

I think I'm beginning to understand the purpose of you posting this thread. Maybe I have it wrong and I'd welcome some clarification if so, but I think this is the type of troll meant to start a fight. Let me explain.

You state that "Cold tempering requires heat treatment cycle". Not true. It's not a matter of being in vogue either. While I concentrated on deep cryo immersion of engine blocks and reciprocating assemblies in order to stay under the radar, the principles remain the same. If one were to heat treat a block and then cryo treat it the resultant brittle casting would last less than sixty seconds after start-up and subsequent shatter. Heat treating is a part of the equation only if you wish to add hardness. In fact, most applications of cryogenics don't want the material to also be hardened. If only you would do a small amount of research you'd find this to be true.

Large firms like Rockwell, IBM, 3M, etc. cryo many parts and have participated in important research. The findings are yet to be fully understood. An example is the theory that molecular reorganization occurs through cryo'ing. The results seem to prove this because holes in silica wafers become filled after. They don't know why. Science hasn't gotten that far yet.

Your mistaken claim that heat treating is required destroys any validity you may wish to have garnered with your diatribe. Obviously, you ain't no scientist. In a hobby where what matters is what one hears you conveniently dismiss anecdotal evidence. Our ears will always and forever be anecdotal devices. They are not meters. Your proposition is totally absurd and I'm calling you on it. BTW, I'll be glad to have some brake pads heat treated and cryo'd as a gift to you as long as you promise to install them and hit the brakes hard the first time at about 140 entering a curve.

To my simple way of thinking discussions like this could be fun and interesting and as science evolves eventually enlightening. Nobody needs to agree about any aspect of these technologies. At some point most of us learn that life is too short for this kind of twisted enjoyment. I wish you luck in getting there.

Ejliu,

I would think cryo treatment comprises a complete cooling and (re)heating cycle; i.e., the return to room temperature constitutes "heating" in my book. No heating above room temp is required, but I suppose it could be used along w/ cryo in some applications like hardening of tools, etc.

Cold tempering (as I use the term) has been around for a very long time; what is in vogue, as you say, in audio is same process (or should be) as Cryopro and other outfits have been doing for years. Actually cryoing has been around in audio for quite, more than 6 or 7 years, now that I think about it, Meitner, Walker, and many others, some more public than others. I first started using Crypro about 12 years ago, about the time that some big guns like Holleywell were experimenting with cryoing transistors. (Never did hear about their results heheh)