DIY cryo treatment

[Chuck H]

I usually hang on the amp forum but I came across something I think may be of interest here. I "suffer" multiple avocations. One is making knives. A big part of many thermal austenitic steel treatments is cryogenic treatment. Well the clever dudes on some of the blade forums have figured out how to do it with commonly available materials! The best cryo services offer -300F. Some of the thermal treatment services that specializes in blades did a study and found that 95% of the advantages gained by cryo treatment can be obtained by reaching just -70F. A solution of dry ice and isopropyl alcohol will get down to -77F, is quite stable and the materials are easily purchased. So there you go. I can't make any recommendations on ratios or soak times so you guys will probably want to do some research of your own. I just know that some interest in cryo treatments has been expressed here and this information makes it eminently accessible for experimentation.

Cheers

[tedmich]

FYI LN2 is much cheaper than CO2 and, if you can score a dewar, lasts quite a while.

[Chuck H]

I may have heard that but as it happens I've never looked into the procurement of liquid nitrogen. I'll check it out but I just assumed they wouldn't sell it over the counter to just anyone.

[g1]

If you have any doctor friends, they use it to freeze warts.

[Chuck H]

If you have any doctor friends, they use it to freeze warts.

So no one's going to ask about it if that doctor friend starts buying it by the gallon

I'm looking into it now... More to follow.

[Leo_Gnardo]

I may have heard that but as it happens I've never looked into the procurement of liquid nitrogen. I'll check it out but I just assumed they wouldn't sell it over the counter to just anyone.

Try your local welding-gas supply shop. For special attention wear a Zildjian T-shirt with arabic writing and wrap a towel around your head. And smoke a Camel. Around here they'll sell anything to anybody. I see them driving a stake-truck around with bottles of gas of all sorts, not much in the way of load control, so much for "safety."

Dewar flask = fancy thermos bottle. An ordinary thermos made the ol' fashioned way with metallized glass might do for a small quantity if you can cadge some from a place that uses it regularly. Just don't close the cap tightly, gas needs to escape or it will split the glass.

What your doctor friend charges to remove a wart, he can buy a 100 gallon cylinder of LN, who cares how much goes to waste. Or Chuck. Or to quick-chill a case of beer or 2.

[Chuck H]

Ok... Some brief research reveals that they will sell it to just about anyone. They may ask about what you're using it for but you can say "I'm cryogenically treating stuff." and that'll be fine.

One problem is that they won't bring it to you. Another is who they are. Some, but not nearly all welding supply houses, medical supply and even the rare kitchen supply may have it. Maybe you're lucky and live near an industrial district with a liquid gas supply. Good luck finding it near enough because they won't ship it. Further, many places that sell it have a multi liter minimum. So you'd better plan a whole butt load of experiments at once. You'll also need the aforementioned Dewar flask. They won't put the stuff in anything else for you. Some of the liquid gas places will rent you one. Buying a decent one is a couple to a few hundred bones. So there you go.

Or... You could get some dry ice and isopropyl alcohol readily available in manageable quantities for small experiments to be done in a Styrofoam cooler. Just sayin'.

[tedmich]

on the bright side measuring the difference between metal dipped in CO2/IPA versus LN2, or for that matter your scotch on the rocks is very difficult...

[Chuck H]

Yes. Considering my position on it anyway, it seems like much ado about nothing. I posted it because I know some here may be interested. I know I'll probably use it for treating knives, but not tubes or pickup poles.

[Kazooman]

A solution of dry ice and isopropyl alcohol will get down to -77F, is quite stable and the materials are easily purchased.

Cheers

Actually it is more like -109 degrees F. Dry Ice is -78 degrees C.

[tedmich]

cooling baths can be made a variety of temperatures based on the solvent the cooling components (LN2 and CO2) are slurried in. A variety of higher temperatures are achieved with a variety of solvents, see:
List of cooling baths - Wikipedia, the free encyclopedia
so IPA/CO2 is about -77C versus -78.5C for CO2 alone and there are a few oddball "lower than neat" temps too, most notably wet ice and salt!

[Chuck H]

Actually it is more like -109 degrees F. Dry Ice is -78 degrees C.

Capitol! Yes, I failed to note that the temps given were in Celsius NOT Fahrenheit. Good catch keeping it accurate.

[Chuck H]

The tests I reviewed were about austenites transformation into martensite in heat treated steel. The test was only done with the dry ice and isopropyl alcohol mixture (at -77C) and compared with the advantage of cryo treatment in LN2 (at -196C) and it was found that the dry ice and isopropyl alcohol mixture offered 95% of the improvement that the pure LN2 did. That seems like a negligible enough difference but I have no idea what the results would be with solutions that create temperatures above -77C because the test didn't include them.

[defaced]

The austenite to martensite transformation temperature is material dependent, and only exists in material that exhibit this form of diffusionless transformation. This temperature is called the martensite finish temperature. So, yes, you can make a cold bath, and yes it will work for the materials used in knives, but because tubes are made of different materials, you may not get any (supposed) benefit from it.

Regarding gas suppliers, you'll want to ask about the small dewars noted on the bottom of this PDF: http://amo-csd.lbl.gov/downloads/Gas...r_Overview.pdf. I often get HP180s for argon and they are several hundred pounds. I've seen short versions of them on casters, but never bothered asking the delivery guy what the name of the size was. If I was at work right now I'd walk down to the end of the building and ask the gas supplier what sizes are common.

[tedmich]

The austenite to martensite transformation temperature is material dependent, and only exists in material that exhibit this form of diffusionless transformation. This temperature is called the martensite finish temperature. So, yes, you can make a cold bath, and yes it will work for the materials used in knives, but because tubes are made of different materials, you may not get any (supposed) benefit from it.
.

Well you (as usual) take the strictly SCIENTIFIC approach to this marvelous money making enterprise Mike! Many many companies take advantage of the gee-whiz effect of cryo to claim anything about this stuff. There are people who claim that plastics somehow become miraculously harder on LN2 treatment (just ignore the destroyed surface of the plastic part) and there are people who will cryo treat your entire 1959 LP or 1937 Martin. There is such an air of magic around this stuff some poor fools freeze their (entire $$$ or parts $) dead body awaiting rebirth as a non sick/dead person.