Cryogenic freezing of tools

[bugzpulverizer]

Has anyone had any experience with the process of cryogenically freezing cutters to increase tool life? We had a company visit us called 300 below, and for $10 a pound they will freeze our inserts, or e-mills which is supposed to give 200%-400% more tool life. I went on their website and read about the technology, and I guess it makes sense. Although my chemistry experience is summed up as 3 drunk semesters in the early '90's. I just hope they move Ted Williams' head before putting our tools in freezer.

[Stepper Monkey]

I haven't used it on tooling, but I do have experience with it on gun barrels and have known knife makers who treat their blades. The process has been around for some time and a lot of people seem to swear by it.
It was some time ago, but I understand Beretta tried it on their tooling for making handgun barrels and got significantly more life out of their cutters. Don't know if they still use it, but they seemed really excited at the time.

[RICHARD ZASTROW]

We had rotary cutting dies cryo. treated. The life of the treated dies was 300% of the non-treated. After that, they all were and probably still are being cryo. treated as part of the heat treatment cycles.

Dick Z

[toastydeath]

The trick, from talking to and reading from folks who do it, is to find a reputable place and pay a few extra dollars to get it done. A poorly done cryo treatment will decrease the life of the tool, and it's easy to muck up.

It's definitely cost effective for things you don't resharpen. Cryo treatment is once, and lasts for.. until you throw the tool away or can't resharpen it anymore. Big endmills especially.

I'm not sure I'd do it on inserts, however, unless you were having trouble with inserts failing before the end of a long operation.

[bugzpulverizer]

Here's the thing. We mill a bunch of big ugly steel castings, and any life improvements of the inserts is very welcome. The company was featured on The Discovery Channel. Don't know if that makes them reputable or not. $10 a pound, seems relatively cheap, and easy to make up if it works. Thanks for your replies guys. They have helped me.

[Geof]

Did you search on the zone for cryogenic treatment? It has been discussed before.

With HSS tooling there does seem to be a positive effect on tool life and if you do some reading on the subject there is a rational metallurgical explanation. Briefly explained, when metals are heat treated to get a particular crystal or phase structure there are always microscopic regions which do not complete the transition during the cooling process in the treatment. This gives minuscule variations in the properties of the metal and it is these variations that lead to faster wear than would be the case with a metal that was utterly identical all the way through. Taking the metal down to liquid nitrogen temperatures, -196 Celsius I think, forces the crystal transition more toward completion so the metal has a more homgeneous crystal structure.

I know people claim that it also works with carbide but I do not know if there is a similar thing occurring; carbide gets its hardness by a completely different mechanism than HSS. But it is possible that cryogenic treatment has an effect on the structure and strength of the binder in carbide tools even if it does not affect the carbide itself.

[toastydeath]

Originally Posted by Geof Did you search on the zone for cryogenic treatment? It has been discussed before. With HSS tooling there does seem to be a positive effect on tool life and if you do some reading on the subject there is a rational metallurgical explanation. Briefly explained, when metals are heat treated to get a particular crystal or phase structure there are always microscopic regions which do not complete the transition during the cooling process in the treatment. This gives minuscule variations in the properties of the metal and it is these variations that lead to faster wear than would be the case with a metal that was utterly identical all the way through. Taking the metal down to liquid nitrogen temperatures, -196 Celsius I think, forces the crystal transition more toward completion so the metal has a more homgeneous crystal structure. I know people claim that it also works with carbide but I do not know if there is a similar thing occurring; carbide gets its hardness by a completely different mechanism than HSS. But it is possible that cryogenic treatment has an effect on the structure and strength of the binder in carbide tools even if it does not affect the carbide itself.

There's an underlying effect that goes on besides the martensitic transition, even in steel, that allows other materials - from carbide to plastics - to undergo successful cryo treatment.

The cold brings the atomic radii closer together (obviously - thermal expansion). In steel, the first effect is the remaining austenite transitions to martensite, as you mentioned. But this also causes the rest of the crystalline structure to reorganize itself wholesale. Atoms that were previously bonded under stress can reform crystals with other, closer atoms as the force required to create a new, more ideal bond overcomes the force holding the stressed bond together. It's very similar to the phase change from liquid to solid. The energy keeping the atoms free and fluid is overcome during that change, forming the initial bonds - which may not be ideal, it was whatever was closest at the time. Keep cooling it down, and those bonds keep rearranging closer and closer to a monocrystalline solid.

Of course, if you cooled it down slow enough in the first place, you'd get a monocrystalline material and cryogenic freezing would have no effect. Such as silicon wafers and whatnot. The other extreme, rapid cooling, would result in amorphous solids like glass, or any metallic alloy capable of glassification.