[gtrdude]

Has anyone looked into cryo tempering their parts before building a machine before? Is the end result likely to give greater stiffness and finer tolerances? What about being able to use less costly parts (ie. smaller metal tube and rails) to acheive the same thing?

If anybody has experience or can shed some light on the process I would be greatful.

Paul

[atifeh]

One example of cryo treatment which I know and use it to some extent is:

(Theory) after quenching hardenable steels you will get Martensite (a hard but brittle structure). By tempering it you get tempered Martensite which gains some toughness while somehow losing the hardness.

(More theory) quenching in oil, brine or water will not produce a fully Martensitic matrix and still has residues of un-transformed Austenite, named retained Austenite (which is soft and impairs the strength gradually). By quenching to lower temperatures you can transform the retained Austenite to Martensite.

I usually put a quenched part in the freezer, about -13 C, and then put it in dry ice (CO2 ice) which is about -40 C, then temper it. The effect is noticeable in low alloy steels, specially containing Mo, but minute in carbon steels.

I have not tried to cryo treat available quenched and tempered part. Don't know if subsequent tempering will be required or not, but will try to find some articles on it.

Nader

[smarbaga]

i made a heat treating controller for a company that made pump shafts.
they cut and ground the shafts then put them into the ovem for like 24 hours.
this could be done for smaller parts in a home oven as the temp was about 500 degrees .
it took like 3 hours to bring the shaft up to temp and about 5 hours to bring it down.
the bringing up to and cooling down times were the critical part of the controller.

[One of Many]

i made a heat treating controller for a company that made pump shafts.
they cut and ground the shafts then put them into the ovem for like 24 hours.
this could be done for smaller parts in a home oven as the temp was about 500 degrees .
it took like 3 hours to bring the shaft up to temp and about 5 hours to bring it down.
the bringing up to and cooling down times were the critical part of the controller.

Chances are this was to remove residual stress in the surface after grinding? We did a similar procedure in high temp oil after bearing duplex grinding. Without it, the surface could fracture like a glass marble. Something to be avoided on a $12k propeller blade!

DC

[sendkeys]

I wonder, if you could get a couple extra inches of cutting using this type of treatment on hss tools ?

[Evodyne]

Hi guys,

A former employer of mine operated a hydraulically operated, very large (building size) scrap metal shear. The guillotine blade was door sized, at least. This thing was in use 24x7 and blade replacement was the primary source of downtime. So they hired a company to cryo the blades and got like three times the lifespan. It was really impressive. I would think there would be a direct parallel to CNC tooling. Guys were also sending down their golf clubs with the blades. They didn't play any better afterwards though.

Lance

[Geof]

If you put "cryogenic tool treatment" into Google you will come up with over 300,000 hits. It is a valid method for increasing tool life in some applications but I think it has been oversold so you will encounter people who say it is a bunch of rubbish. It can also extend the life of gears and bearings in some applications but it is really only applicable to hardened alloy steels. It will not alter stiffness or strength or anything like that.

One technical explanation I read about cryogenic treatment, and this is real cryo down to liquid nitrogen temperatures, suggested it worked because the extreme low temperature forces the austenite to martensite transformation more completely. This means the material is more even in hardness so when the surface is elastically deformed during use you do not get micro stress raisers in the transition region between hard spots and harder spots. This reduces the incidence and size of micro fatigue fractures that cause spalling and surface breakdown leading to the eventual wearing out of the part.