Sub-Zero Quench

G

GW

Joined
Jan 20, 2000
Messages
18
O.K. - this might be a stupid question but......for those of us who live in areas where dry ice is not available.....would a CO2 fire extinguisher not do the trick? I have no idea how cold this is but I do know that it cools off a case of beer pretty quick!
 
George is right. I've played with the acetone/dry ice mixture too, and am not convinced that it does a lot. I suspect that the temp is just not low enough. (acetone/dry ice will only go to -70), whereas liquid nitrogen is at -300. I don't have the time cycle nailed down the the minute, but know that there is a noticable performance increase after 4 hours. (At least it works that way with my set up.)


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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
The triple point of CO2 IS -70 F. This means that all three states: liquid, gas, and solid can exist at that temp at atmospheric pressure. How do you achieve this? Take the outlet of your CO2 container, and capture the spray (hopefully liquid) in a cloth bag.
BUT.... what remains is solid, which is only -14.
I believe in a sub zero quench. But at what cost? And just how much will it improve the perfomance of a knife, or is it just something to dazzle your clients with because your grinds aren't quite perfect, or your lines are washed over?
I've never known any client to brutalize a knife to the point of a power machine tool, which is what extreme quenches are for. It is after all, a hand piece. More importantly, concentrate on proper blade geometry and a good heat treat to begin with, with NO NO NO decarburization of the steel!!! This will do wonders for perfomance.
And if you need something incredibly hard, tough and long lasting, try some good old D2, hardened to Rc62, and let your client cuss you out when he tries to sharpen it!

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Jay
www.gilanet.com/JayFisher/index.htm
 
can you dub zero quench O-1,and does it help?
Karl schroen says he uses dry ice and acetone..but neglected to mention O-1 and i`ve read his book numerous times!
Thanks for all the help guys this forum kicks a$$
biggrin.gif


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http://www.nebsnow.com/The_Dwarven_Forge

That which does not kill you only makes you stronger
 
A large CO2 fire extinguisher can actually get you a colder temperature than dry ice, but you need to use a lot of liquid CO2 in the process. The process is a lot like evaporation where your remaining fluid gets colder as evaporation takes place (technically you are cooling via adiabatic expansion).

You would need to make yourself a heavily insulated cold box. Take a lot of styrofoam or fiberglass insulation. Make a very heavily insulated well in it for your blade and some other thermal mass (a good thermal mass would be a bunch of gravel). Cover your blade with the gravel. Insert snout of extinguisher in the well and empty it quickly through the mass. You want the whole knife and thermal mass chilled. Wrap up your insulation thoroughly. The mass should stay cold for a long time.

Quickly evaporating liquid CO2, expanding freely into the air, will produce super-cooled dry ice powder. You just need to keep the temperature from going back up.



[This message has been edited by Jeff Clark (edited 02-11-2000).]
 
From the research that I have done so far, these are the conclusions I've come to.

1. Cryo quenching is only effective at -100F. minimum and best if held around -300F.

2. It is also recommended that a dry quench be used so as not to shock the material which may cause fractures in its structure, and the temperture lowered over a period of time and then held - which if I recall was somewhere in the neigborhood of 12 hours or more.

One method I read about was to drip liquid nitrogen into a insulated container with the item to be quenched suspended (in a rack of some sort) above the pool of liquid nitrogen below. The other method along these lines was to use dry ice placed on top of the rack and leave for duration. (remember to leave an opening in the top to let the gas escape - outside.

I think that it was Wayne Goddard in Blade magazine who wrote that he has gained good results with all steels (don't quote me on that, but I think that is fairly correct) with Cryo-quenching; explaining it like...
a room full of plastic balls (like you might find in a childs daycare center) that are just randomly ditributed - this is the steel in its normal state. Then consider this same room, but all the balls are neatly stacked in the tightest pattern that can be arranged - this would be the cryo-quenched state. I believe in the article he does have some test results on various types of steel that seem to say that it does make a difference.

With that said, I think the general concensus is that cryo-quenching only really has any benefit on alloyed stainless type steels.

I'm certainly no expert, so if anyone knows better, let me know.

Best regards,

Darren
 
Cryo treating has proved advantageous in most metals to improve stability. The earliest tests that I have heard of were over 30 years ago in the aerospace industry with drill bits where they were improving performance 3 to 5 times by simply cryo treating. Other items like sawblades also benefit from this treatment, ask Jim at Texas Knifemaker's Supply...he is now cryo treating his bandsaw blades that he uses to cut up materials. High precision machining of aluminum is enhanced when the metal is cryo treated before machining, less creep.
Match grade rifle barrels also benefit by treating them.


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george
www.tichbourneknives.com
sales@tichbourneknives.com


 
metallurgist reason for cryo- complete marstinite transformation...i think the molecules in steel are austinite before h/t and marstinite after.....so the cryo helps the molecules make the molecular charge more completely. thus you have a more homogeneous mix if you cryo...whereas the other way there a bunch of molecules that dont make it and you have a less homogeneous mix...is that right???? thats my take on it. absolute zero is the right temp.....but we cant get that.

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http://www.mayoknives.com




[This message has been edited by tom mayo (edited 02-11-2000).]
 
Tom,
Your on the right track. Here's the low down on how the process works from the "inside" of the steel.
Hardening (critical) temp is general the temp that all the elements are in solution on simple steels. Some soak time is required for more alloy rich steels. Solution can be explained by saying that all of the elements are equally distributed and mixed throughout the steel.
Austinite is a platlette structure situated in an end to end fashion, and after hardening, some of this sturcture remains within the steel. Through sub-zero quenching most, if not all of this structure (austinite) is transformed into Martinsite, which is an overlapping platlette sturcture. The way I explain this to people is to have them imagine dinner plates arranged edge to edge.(austinite formation) Think of the force is would take to segregate the plates. Now imagine the same plates with their edges overlapping, (Martinsite formation) and think of the forces necessary to segregate them. It becomes clear, that the overlapping plates have a much greater overall strength than the edge to edge plates.

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
There is a 3 part series of articles over at heatreatingonline.com that talks about the process and how to do it. The article talks about using dry ice and kerosene. It states that the dry ice makes it down to -120 degree.

Here is the link to where the articles are: http://www.heattreatingonline.com/articles.html

The title is "CYROGENICS CAN KEEP YOUR TOOLS SHARPER and LONGER"

Stiletto
 
A couple of weeks ago, I was given the nickel tour at Texas Knifemaker's Supply heat treat and cryo chamber. They ramp down to -305 degrees F and soak it there(don't ask me how long, I didn't pay that MUCH attention) then ramp it back up. Tempering is usually done then. Pretty interesting process.

They also do gun barrels, guitar strings, musical instruments, etc.

It sounds like the old dry ice/acetone slurry is off spec and you really can't get there from here for the most part.


C Wilkins

[This message has been edited by C L Wilkins (edited 02-11-2000).]
 
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