Liquid nitrogen?

Will52100

Will52100

Joined
Dec 4, 2001
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I'm toying with the posibility of getting a heat treat oven, both for theremal cycles on carbon steel and to heat treat the few stainless blades I do. Paul Bos does an excellent job, but I hate having to get a batch together and send them out.

I can invest in a dewer, but that's a lot of wasted nitrogen.

Is there anywhere I can get a large thermos at a time? I'll have to check welding supply places when I get in.

Thanks
 
A possible alternative-In agricultural areas, people store cattle semen in dewars. Check with ag people for dewar sales and/or LN purchases.
 
Liquid nitrogen isnt that expensive. I pay $1.28 CDN a litre. A 20 litre fill lasts for about 2 months if I'm not using it - and even a month or so doing a couple batches a week.

If you are looking at Dewars, may I suggest that Lagavulin is a far superior Scotch. :D

Oops! Off topic. For your nitrogen storage vessel, make sure the neck is wide enough to get your biggest blade in and look at what the depth is as well.

The liquid nitrogen is not limited to Heat treating use. You can remove warts - flash freeze deer steaks - and store semen. (Preferably not all in the same tank) Use your imagination. :rolleyes:

Last week I had maybe a couple litres - err.... quarts... left and was making the trip in for more. Rather that just dumping it, I transferred it to a small cooler (six pack size). Three hours later, when I got back it was all gone. A thermos might be a bit better but....

Hope this helps some.

Rob!
 
When I moved from Iowa to Portland, Oregon area I had about 100 lbs. of frozen venison steaks to take with me on the drive. Through research I found out that most Albertson's have and sell dry ice also. Depending on what temperature you're trying to accomplish, dry ice is about -112 degrees F. If fill a container partially full with industrial alcohol or anti-freeze, and then add dry ice to that so that the volume doubles, you'll have a -55 degree F. slush. Depends on the cryogenic temperature you're after. Most blades, I think, require a temperature down to -100 degrees F.

I've wondered about trying to retain some toughness, by only using -55 degrees F. This temperature won't convert all of the retained austenite to martensite, unless left for a very, very long time in the coolant. If you get the retained austinite down to about 5 to 10%, it might help with toughness. Has anyone experimented with retaining some austinite?
 
will roger linger did a post a while back i believe about getting them off ebay (of course!) might wanna check with him and check whats for sale on ebay
 
scottickes said:
..... If fill a container partially full with industrial alcohol or anti-freeze, and then add dry ice to that so that the volume doubles, you'll have a -55 degree F. slush. ........
Click to expand...

Scott, do you have a reference for that statement? I am under the impression that the important ratio for varying temperature was the percentage of ethylene glycol (anti-freeze) dissolved in the alcohol. (In other words, a bath made with 1:1 alcohol:antifreeze will give a different temperature than 2:1, not the ratio of liquid to dry ice.)

If I have misunderstood this, I would like to read about it. Any information would be appreciated.

Thank you.
 
To answer your question as to if I have a reference for that statement. In essence, I'm the reference for that statement. This comes from my work as a Service Engineering Rep. for a bearing company. Our research center has tested this method of freezing bearings (outer races) for installation purposes and found that 1:1 volume ratio = -55 degrees F.

This assumes a high quality pure dry ice that is truly at about -112 degrees F. I know that if you double the volume in the container when you add dry ice, you get -55 degrees F. If you use a dry ice that isn't pure, which is sometimes the case from ice cream stores, etc., you will be starting at a warmer temperature with the dry ice. I've found that those usually end up at about -20 degrees F. to -30 degrees F. with a 1:1 ratio.

I'm not sure how cold it is if you use a 2:1 ratio of dry ice to alcohol. Bearings shouldn't be taken below -65 degrees F., so we teach mechanics to use the 1:1 ratio to play it safe. I only know the temperature of the 1:1 ratio as stated above.
 
That's an interesting approach to a cold bath. I used constant temp baths in the lab quite a bit over the course of a career and this is the first time I've heard this concept of ratioing the volumes of dry ice to liquid to control the temp.

Whatever works for you. :)
 
In out of the way machine shops and maintenance shops, this is the best that some of them have for freezing parts. It gives them some measure of control.
 
I should be able to get it, my father used to A.I. cattle when he was dairying a few years back. I've got a 30 day tank, but it leaks in a couple of weeks. I'm not sure what it cost now. It used to be around 15$ to fill the tank.

The trouble is for the forseable future I'll only be heat treating two to four blades at a time, mostly high alloy carbon steel like 52100 and the ocasional stainless and damascus. For the most part I only need a big thermos full. Basicly when I've got the forging and grinding done I'll have to go and get it and then it'll evaporate before I need it again, so why get a lot? If it comes down to it I may have to get a dewer full, but I hate waste.

I've thought of the dry ice, but if I'm going to the trouble I might as well see if I can get liquid nitrogen.

I've heard of getting it from welding shops, and will check it when I get in, but I wonder if there are any special hasmat regs?


Thanks
 
Will,
Very sorry to hijack here but it seemed like such an opportune time!;) I was wondering if there is a magic temp to attain for cryo treating. I have access to a dewar @ work but was unsure of the temp needed for proper results.
Thank you ,
Matt Doyle
 
Hey Matt

Check out the crucible website for cryo suggestions. ie: 154CM -100F.

Dry ice will do just fine but Liquid Nitrogen is so much easier to store. Colder does not cause any problems. It's probably a contentious issue, but my understanding is that warmer doesn't accomp;ish anything at all.

So, IMHO, at least -100 is the magic number. I suspect you have opened up something of a diverse range of opinions.:)

Rob!
 
I live in a rural are where AI of cattle was the vogue in about 1970. Consequently there are Dewars sitting around unused. I advertised in the local paper and bought a dewar for $150.

Freezing is recommended by the steel industry when you have a need for precise dimension. The retained austenite will convert with time and change the volume of the steel leading to dimensional changes, like fine blanking dies. This is one of the main reasons for cryo treatments. The process of freezing will speed the reaction that is already happening, it just happens real slow. Dry ice and acetone will be safer to handle that a thermos of Nitrogen. With a dewar you have it filled then quench in the dewar rather than any additional handling of this potentially hazzardous material...Take Care...Ed
 
Will one of the problems filling anything with LN is they use a lot of it to cool the vessel so they can fill it it boils off until the container is cooled , so the more they can sell you the better they'll like it..
a thermos will work for sure the question is will they fill it for you:confused: :)

I do believe dry ice is not cold enough to do the job right right then, I've believed for years now you'll need at least -135 deg's to finish the quench..
this was designed for all of the super steels.. but it is a can of worms for sure.. I always say, better safe then sorry, then I don't have to worry about it..only my opinion
I use a lab Dewar , I have it filled for 10 bucks, it will be gone in about 24-30 hours
and the blades left in the Dewar will warm slowly..average cost per blade
~$1.00-$2.00
 
I picked up a dewar recently and called my local gas supplier to ask about protocol. They said buying small quantities was no problem and that my dewar would be fine. They said they regularly fill thermoses too as long as a small hole is drilled in the lid to act as a vent.

-Ben
 
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