dry ice

jrhart50

jrhart50

Joined
Mar 11, 2007
Messages
261
can dry ice and alcohol be used as cyro on 440-c and if so how much will it take of dry ice in a small lunch type contaner?
Thanks JRH.
 
Yep, dry ice will give you the same final hardness readings as LN2. 2-3 pounds is definitely enough.
 
I have never used alcohol with the dry ice. That probably works but I don't believe that it's necessary. I simply sandwich the blade(s) between two layers of dry ice. Use a well insulated container. It's all time & temperature. It should stay at that temp for a minimum of 6 hrs. You will be able to tell after that time if the amount of dry ice was sufficient by the amount left.

Gary
 
I use dry ice and or LN and have not found a difference between the two in hardness
or toughness (to the best of my ability to check it) I Rc every blade and spring I make.I can get either locally. LN runs about $20-$25 for 10 liters and lasts in my dewar for 3+ weeks. I pour alcohol over the dry ice until violent boiling stops, this is after I have the blades covered with chipped dry ice and then overnite. With the LN I suspend them over it for a while before immersing in the liquid. I pay $5.25 for 3 pounds of dry ice. Make sure either is part of the quench-not later.
Ken.
 
never heard of using alcohol with dry ice?
Have however used dry ice & acetone on several occasions.
believe it will get you to approx -110
 
RSMITH said:
never heard of using alcohol with dry ice?
Have however used dry ice & acetone on several occasions.
believe it will get you to approx -110
Click to expand...

Bob T's book anatomy of a linerlock folder think I read it about 10 or
so years ago.
Ken
 
I wouldn't try to store it. I buy a about 4 or 5 lb at a shot from the grocery store. Bust it up a little bit ( wear gloves to handle or suffer frost bite) and place in a metal 3 gallon bucket. Fill it with acetone and add the blades. My bucket for this I have wrapped with fiberglass insulation and loosely duct taped. Once the blades are in the mix I cover it with a piece of insulation and then go do something else. Once the dry ice has melted and the acetone has warmed back up I pour it back in a container and keep it for the next batch. I try to do aaround 5 blades at a time to keep the cost down and its no harder to do 5 than 1.
 
ib2v4u said:
I wouldn't try to store it. I buy a about 4 or 5 lb at a shot from the grocery store. Bust it up a little bit ( wear gloves to handle or suffer frost bite) and place in a metal 3 gallon bucket. Fill it with acetone and add the blades. My bucket for this I have wrapped with fiberglass insulation and loosely duct taped. Once the blades are in the mix I cover it with a piece of insulation and then go do something else. Once the dry ice has melted and the acetone has warmed back up I pour it back in a container and keep it for the next batch. I try to do aaround 5 blades at a time to keep the cost down and its no harder to do 5 than 1.
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:thumbup:

Yup.

I will add:

I do this in an outbuilding so I don't have a lot of acetone out open in my shop. Once it is cold it stops fuming and evaporating and otherwise making you stoned. All the CO2 can carbonate the acetone a little. I leave the cap on loose after I pour it back in.

You are aiming for wet dry ice, not acetone with some ice floating in it.

The purpose of dry ice or cryo is to get down to a temp where the martensite transformation is (practically) complete before you run into excessive stabilized austenite. For the life of me, I don't understand why it is time dependant, but it does appear to be. 2 hours is probably a good minimum.

For most applications, there is little real difference between dry ice and LN.

It has been my experience that the sooner you get your blade into sub zero, the better the results. To the point that I recommend no snap temper at all, but instead a continuous drop to Mf as part of an relatively uninterrupted quench. Not everyone agrees with this and there have been some heated debates.
 
A little plain language explanation of the process:
Austenite is your brother-in-law at college. He is hot and wild, ready for anything...but he is unstable. ( steel heated to above 1350F).
When graduation time comes ( quench), and things cool off he has to decide what to do with his life. If he sticks around campus too long, he ends up living in the Pearlite frat house until he is 40 ( formed when the steel cools too slowly). Unfortunately, they are all lazy pot heads, and have become soft and useless for any work. So his folks cut him off right after graduation ( fast quench to below the pearlite nose), and he comes home with your sister, to live with the Martensite family. Now you are all sharp folks, and hard workers. You don't wear down and you are tough characters. However, some of Austenite's bad habits are hard to get rid of. He will adapt to becoming a member of your household, but needs a little re-direction. Now, the sooner you get him on the right path, the sooner he becomes a full fledged Martensite member.If he just comes home with you, and doesn't get to work soon, he will become the Bainite of your existence, and will just lay on your couch drinking beer all day ( formed when the steel stays below the pearlite nose, but above the Ms too long). The first step is to get him on the right path ( continuous cooling to below the Ms. Get that done and things start to settle down to normal ( quench to room temperature). However, there is a part of Austenite's party animal past that he clings to ( retained austenite), and he needs some tough love, so you make him go cold turkey until his bad habits are gone ( cryogenic treatment at -100F or lower to gain 100% martensite conversion).The longer you wait, th harder it will be to get him to change. Once he has been at cryo rehab for a while,he is a new man, almost fully Martensite, but frail and he easily could become a broken man ( untempered martensite). You can now take him home for the weekend to your warm and loving home, being careful not to overdo it ( first temper) but he is not yet fully recovered and will need to return to finish his conversion ( second cryo). When he gets released ( no retained austenite), you toughen him up with some extra warm love ( second tempering ). He responds to this well, and becomes more flexible and a useful member of the family ( tempered to the target). Be careful not to overdo the warm treatment, or he may become soft again ( over-tempered and too soft). Now, all that is left is to sharpen his skills and put him to work.
 
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LOL. I must have had a lot of retained austensite when I was younger. Maybe all the cold winters and hot summers around here converted it.
 
Nathan the Machinist said:
...
It has been my experience that the sooner you get your blade into sub zero, the better the results. To the point that I recommend no snap temper at all, but instead a continuous drop to Mf as part of an relatively uninterrupted quench. Not everyone agrees with this and there have been some heated debates.
Click to expand...

I took Nathan's advice and cryo'ed my A2 as soon as it got to ambient, with no snap temper, and the blade came out really great. No problems with cracking.
Thanks again, Nathan.
- Mitch
 
Troop said:
I took Nathan's advice and cryo'ed my A2 as soon as it got to ambient, with no snap temper, and the blade came out really great. No problems with cracking.
Thanks again, Nathan.
- Mitch
Click to expand...

:thumbup:


I have heard of cracks that you can't see, but show up with more sophisticated testing. I'm generally very concerned with cutting performance and edge retention, but I seldom use blades in ways that break them, so any invisible micro cracks have never shown up for me. But if I were making a large chopper I might consider a short temper at 325 to hedge my bets. But not for small knives, skinning knives, kitchen knives, folders etc... *shrug*
 
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There's been several reports of blades being more brittle when they are snap tempered. Maybe the snap temper temperature is too high. Some people just put the blade in boiling water (212F) for 30 minutes and there's been no issues that way.

I just go directly to cryo (something LN2, sometimes dry ice), I've never had any cracked blades. Warming back up make sure it doesn't get covered in ice or it will crack.
 
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