Cryogenic "Chamber"

Jason B.

Jason B.

Joined
Jun 13, 2007
Messages
11,143
Here at the Phoenix knife house we a looking to get set up for self sufficient knife making and while researching the tools needed the question of cryo treatment came up. One of the first steels we plan to work with is Elmax and would like to ensure we get the most out of the heat treatment.

Space being at a premium in the shop we are basically wondering how to set up a cryo "chamber". Through a little research have found these http://www.cryotron.com/cryogenic-equipment.htm but would like to hear how some of you are performing this process.
 
all you need is a liquid nitrogen dewar

check used laboratory equipment dealers, or semen / insemination services for used units.
 
Seems too simple, am I just over thinking it?

Would you dip or suspend?

Any advantage to a cryo machine like I linked above?
 
Don't bother with a dewar. Get a high pressure tank and just put a hose on the fluid output. The high pressure tank fills are cheap and you can leave the tank sitting around for a while if you aren't using it all the time. You can use the cheap expanded polystyrene coolers to receive the LN. If you want to make the temp a ramp down and up you can put the blade in coarse salt and let the entire mass drop and climb at a shallow ramp. Once cooled the salt will be a large thermal mass that will hold temperature fairly well.

-Sandow
 
Hey knifenut1013, went to your shop when I lived in phoenix about 2 years ago. Bought a Kasumi 3k/8k combination polishing stone from you, never knew you guys where on Bladeforums.

Most guys seem to stick with a Dewar for LN, those systems that you linked do seem interesting but unless you're pumping out multiple batches of knives at a time I doubt it'd be worth the extra expense in the primary investment, power cost and then refilling cost for the LN.
 
When you get a dewar make sure the neck opening is big enough for whatever you want to put in it. I suspend knives through thong holes or drill a small hole in stick tang knives. I normally put about 4 knives on a wire. As said above, suspend slowly into liquid, if you have a full bunch and put them in too fast it will boil over and waste nitrogen.
I use 1/16 or 1/32 stainless welding wire to susupend them.
 
I am new to the knife making world. Yet I have worked in the enviromental testing industry for some time and play with LN2 all day. We use the Dewars you can order from either Praxair or Airgas . You can use a styrofoam cooler to store liquid in. There are better containers out there yet more $$$. LN2 can be delivered from the bottle using a cheap natural gas line. The fittings on the liquid side of a LN2 bottle are 1/2 in. JIC you can order cryogenic lines from McMaster.com. My company orders the equivalent to a 55 gal drum size container at 230psi. Bottles =500lbs to 600lbs so get one with wheels

I am probably going to state the obvious now but some safety concerns need to be taken into account when playing with Liquid Nitrogen

1. LN2 will burn and cause blisters on unprotected skin
2. LN2 has a very rapid expansion rate if placed in a sealed container it has the possibility of exploding
3. LN2 evaporates into GN2. GN2 is gas nitrogen which displaces oxygen. I have had customers (from million dollar aerospace companies) tell me stories of night shift personal being found in eternal sleep the next morning.
>>> So only use LN2 in a well vented area <<<

I can go on and on about LN2 let me know if you have any more questions.

I am trying to find a thread on making knives from files and what temps to anneal and temper at. Also was trying to figure out if sub zero quenching on carbon steel (files) had any benefits over oil or brine quenching.
 
thegraydog said:
I am new to the knife making world. Yet I have worked in the enviromental testing industry for some time and play with LN2 all day. We use the Dewars you can order from either Praxair or Airgas . You can use a styrofoam cooler to store liquid in. There are better containers out there yet more $$$. LN2 can be delivered from the bottle using a cheap natural gas line. The fittings on the liquid side of a LN2 bottle are 1/2 in. JIC you can order cryogenic lines from McMaster.com. My company orders the equivalent to a 55 gal drum size container at 230psi. Bottles =500lbs to 600lbs so get one with wheels

I am probably going to state the obvious now but some safety concerns need to be taken into account when playing with Liquid Nitrogen

1. LN2 will burn and cause blisters on unprotected skin
2. LN2 has a very rapid expansion rate if placed in a sealed container it has the possibility of exploding
3. LN2 evaporates into GN2. GN2 is gas nitrogen which displaces oxygen. I have had customers (from million dollar aerospace companies) tell me stories of night shift personal being found in eternal sleep the next morning.
>>> So only use LN2 in a well vented area <<<

I can go on and on about LN2 let me know if you have any more questions.

I am trying to find a thread on making knives from files and what temps to anneal and temper at. Also was trying to figure out if sub zero quenching on carbon steel (files) had any benefits over oil or brine quenching.
Click to expand...

You would quench your knife using a liquid quench. Once it reached room temperature you would then give it a cold treatment (usually dry ice in something like acetone) to @
-100 F. This would help minimize retained austenite. For high carbon steels > @ 1% carbon the lower temperature for the formation of martensite is less than 0 F. You only need to leave it in the dry ice until it reaches temperature. Then temper.
 
knifenut1013 said:
Seems too simple, am I just over thinking it?

Would you dip or suspend?

Any advantage to a cryo machine like I linked above?
Click to expand...

From what I have read the advantage to cryogenic treatment is the formation of carbides. As such there is a time component, usually 6 - 36 hours. As long as the blade is at temperature for the correct period of time it does not matter if the blade is suspended above the LN or immersed in the LN. Depending on the number and/or size of the blades you are treating, it might be advantageous to build a cryogenic chamber. You could nest a couple of ice chests and pour the LN through a funnel and plastic tube into the bottom on the chamber as needed. You will need a vent hole in the top to release pressure. I think the machines you listed would work for if you were treating hundreds or thousands of blades at a time. Also I think one of them could be adjusted to hold a temperature between that of dry ice and LN. It looks like you could also program heating and cooling curves.
 
Bo T said:
From what I have read the advantage to cryogenic treatment is the formation of carbides. As such there is a time component, usually 6 - 36 hours. As long as the blade is at temperature for the correct period of time it does not matter if the blade is suspended above the LN or immersed in the LN. Depending on the number and/or size of the blades you are treating, it might be advantageous to build a cryogenic chamber. You could nest a couple of ice chests and pour the LN through a funnel and plastic tube into the bottom on the chamber as needed. You will need a vent hole in the top to release pressure. I think the machines you listed would work for if you were treating hundreds or thousands of blades at a time. Also I think one of them could be adjusted to hold a temperature between that of dry ice and LN. It looks like you could also program heating and cooling curves.
Click to expand...

Literature is pretty conclusive that if cryo does anything for the type of steel you are treating, after 30 minutes you are about 95% of the way to what you'd see at 30 to 50 hours. This pretty much means that the second it gets down to equilibrium, it has done its job. Easy to tell when this has happened since the LN stops boiling on contact with the object.

The mist above LN is significantly warmer that the LN. It is steam relative to water.

Some of the studies just drop the test piece in the LN and pull it out when they hit the time window, others ramp it down and then up. Some raise concerns about thermal shocking being a bad idea as the reason for ramping. Yet to see any literature that actually addresses that issue though. Guessing that for some steels it might be a problem and for others it would make no difference. If someone wants to chime in on cracking or warping related to cryo temp shock, I'd love to hear it.

-Sandow
 
I read in David Boyes how to book his use of Gn2 to purge his high temp chamber of oxygen. The large bottles from Praxair and Airgas have gas ports another thing to consider when setting up shop

Also thanks for the info on hardening.
 
Sandow said:
Literature is pretty conclusive that if cryo does anything for the type of steel you are treating, after 30 minutes you are about 95% of the way to what you'd see at 30 to 50 hours. This pretty much means that the second it gets down to equilibrium, it has done its job. Easy to tell when this has happened since the LN stops boiling on contact with the object.

The mist above LN is significantly warmer that the LN. It is steam relative to water.

Some of the studies just drop the test piece in the LN and pull it out when they hit the time window, others ramp it down and then up. Some raise concerns about thermal shocking being a bad idea as the reason for ramping. Yet to see any literature that actually addresses that issue though. Guessing that for some steels it might be a problem and for others it would make no difference. If someone wants to chime in on cracking or warping related to cryo temp shock, I'd love to hear it.

-Sandow
Click to expand...

I haven't found much on the formation of n-carbides or e-carbides for elmax. Do you have references I could check out for more info?
 
Dipping any heat treated part into liquid nitrogen causes massive thermal shock in the part. No serious heat treater does this. Ask an industrial heat treater about it. They will shake their head or laugh at you.

Industrial heat treating companies use deep freezing chambers that slowly lower the parts in temperature, hold them at that temp the desired time and them allow them to slowly come back up to room temperature.

If you do any serious study of het treating metals, you'll get more information.

Hanging your blades on an old coat hanger and dipping them in a bottle of nitrogen out in the garage in't "cryo treating." You'll be better off sending the stainless steel blades out for professional heat treating and testing unless you can afford the equipment and have the knowledge to do it properly.
 
Bo T said:
I haven't found much on the formation of n-carbides or e-carbides for elmax. Do you have references I could check out for more info?
Click to expand...

I've been having a hard time finding papers on cryo treatment that are not from china or India and as a general rule, no hard science is actually done there. It is either completely made up or plagiarized. Here is a write up that address n-carbide formation that falls in the clearly plagiarized category. If you believe whoever they stole the data from, you favor n over e using cryo. Finding data on specific metals, particularly new and rare ones... Best of luck. Hard enough to find believable data on common tool steels.

http://www.industrialheating.com/ext/resources/IH/Home/Files/PDFs/Role of Eta-Carbide-Meng.pdf

-Sandow
 
Kevin Wilkins said:
Dipping any heat treated part into liquid nitrogen causes massive thermal shock in the part. No serious heat treater does this. Ask an industrial heat treater about it. They will shake their head or laugh at you.

Industrial heat treating companies use deep freezing chambers that slowly lower the parts in temperature, hold them at that temp the desired time and them allow them to slowly come back up to room temperature.

If you do any serious study of het treating metals, you'll get more information.

Hanging your blades on an old coat hanger and dipping them in a bottle of nitrogen out in the garage in't "cryo treating." You'll be better off sending the stainless steel blades out for professional heat treating and testing unless you can afford the equipment and have the knowledge to do it properly.
Click to expand...

Is it more massive of a thermal shock than going from the oven at 1850 directly to room temp. aluminum plates?
I understand your point, but a lot of people do "garage" cryo with seemingly satisfying results.
 
Or, is it possible to ease the shock by going from quench to freezer, then to dry ice, then to LN?
 
Just trying to follow the protocol here...

In the HT of Elmax it calls for a cryo temper stage (as with most pm steels). I know its also called a "sub-zero quench" but I do not know if using liquid nitrogen @ -300 or dry ice @ -110 makes any difference. I would think the liquid nitrogen would provide better results but that's just a guess.

Kevin Wilkins,

I agree with what you say and fully understand that a straight dip would cause sever shock. I know just enough about HT to get me in trouble though I understand science and that there is is proper way to do things. If you have any recommendations on a good set-up for a cryo temper chamber I'm all ears.
 
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