Icing Down a knife, needs suggestions PLEASE

B . Buxton

B . Buxton

Joined
Jul 8, 2001
Messages
3,623
After a thread a while back talking about dry ice, I did some looking around and found a supplier within a coulple miles of the house.
I've never tried anything like this so I was hoping some of you pros could give me a few pointers. I will be using this on a couple 52100 test knives, so I can compare the performance to my regular heat treatments.
First off I do a 3 - 2 hr. temper cycles, so should I temper 1 time then do the dry ice treatment, then temper the other 2 times. or should I temper 2 times,dry ice then temper 1 last time. Or does it matter. Also I was going to place the dry ice and knives in a small cooler and then place those in the regular freezer, I figured that would just prolong the dry ice life, so does it matter how long I leave it on the dry ice? Is longer better,can it be on dry ice to long? Is over night or as long as the dry ice lasts in the freezer, OK? Do I need to let the blade warm to room temp and then temper immediately? How are you guys doing this?

THank you,

Bill
 
I use dry ice in a cooler and it generally lasts a whole day. I sandwich the blade(s) between two flat blocks so that the cooling is by contact (conductive). When the dry ice is put into liquid, like alcohol or acetone, then there is a convective component to the freezing. It may be nit-picking, but I think you get lower temperatures and more stable cooling with the straight dry ice. It's kind of like the difference between a plate quench and air or liquid quenches.

I put them in as soon as they get down to room temp on quenching. If you temper first, you lose some of the sub-zero effect. Most steel manufacturers call for it prior to tempering. I have never had one crack in the cold quench. I have not done 52100, but use it on A2, D2 and S30V with good results.

I work full time and try to schedule things so that I harden the blades on Friday night and freeze until the morning then start tempering. Most of the specs call for 3-4 hours, but I work it so the it goes for 8 to 10 hours, just to fit my schedule.
 
I thought cryo really only helps transform remaining austenite in air-cooling steels like D2 and A2. :confused: (I'm confused a lot though. :D )
 
Burchtree said:
I thought cryo really only helps transform remaining austenite in air-cooling steels like D2 and A2. :confused: (I'm confused a lot though. :D )
Click to expand...

You aren't the only one, Burchie old pal. The cryo thing is new to me also. My paradigm is that only stainless steels benefit from cryo. If I am wrong, then maybe Mete will jump in and slap us all around some. Heck, I just bought a new dewar and had it filled. I'll dunk everythign in it from now on! :thumbup:
 
Generally, chrome content has a profound influence on whether
a steel will bennefit from sub-zero treatment.

Whether the hardened steel should go straight into the freeze,
or get a flash temper first, depends on the steel. Some air hardening
steels (A-2, D-2, etc) can go straight in, while O-1, and W-2 need
a flash temper first(or you may get pieces!).

The way I do it is to flash temper, then wrap the blades in batting, then
in canvas, then sandwich between cardboard, then between plates of
dry ice, in a cooler. Leave till the ice is gone.

The insulation allows for very slow cooling and return to room temp.

.02
 
You may cryo directly from quench. If you don't want to risk cracking you may 'snap temper' before cryo. This has to be done at 300-350F, no higher.Always temper ,400F or more , after cryo...... The more complex the steel the more it will benefit from cryo to reduce retained austenite .These include 52100 on up to S30V.
 
Did anyone catch the article in Blade Magazine about the increase in carbide content, and associated increase in wear resistance when cryo was done? The greatest increase was with D2. The study was done by a state university. I'll see if I can find it around somewhere.
 
Do Not put dry ice in an air tight container, i.e."refridgerators or freezers", the hinges cant take the shock of the doors being blown off.Use a cooler that can breathe.
 
some manufactures say the high carbon SS's needs to be at least down to -120 to work
and I'm told Dry ice only gets down to -90. :o
 
Dan Gray said:
some manufactures say the high carbon SS's needs to be at least down to -120 to work
and I'm told Dry ice only gets down to -90. :o
Click to expand...

Which manufacturer is that?

Dry ice is -112°F, which is the temperature reccommended by Bohler/Uddeholm, Crucible and Timken/Latrobe.
 
This is a great thread for me. I'm shopping for a heat treat oven I can start on stainless steels, but I've been really apprehensive about buying a dewar and liquid nitrogen as I understand that it's an expensive proposition and evaporates quickly. When I first heard, a few days ago, about using dry ice for Cryo treatments, I got very excited as I have an affordable local source for dry ice.

So will it get cold enough, or not?
 
shgeo said:
Which manufacturer is that?

Dry ice is -112°F, which is the temperature reccommended by Bohler/Uddeholm, Crucible and Timken/Latrobe.
Click to expand...

Scott which are they using Nitrogen or Dry ice? and why?

I was told a long time ago -90 on the dry ice..
l'll have to confirm that now..

I'm not sure if 8 degs is much to agrue the point on as the min temp drop..

opps sorry Steve...
 
Things don't change at a certain temperature it's a gradual thing. However to get significant reduction in retained austenite you need ~ -110 .I'm sure that temperature was picked because it's the temperature that CO2 sublimes [goes from solid to gas]
 
For those of you who don't know,a lot of grocery stores now carry dry ice.Ask at the counter.
 
Bill, if your EDC model becomes better as a result of this then you'll be eliminating all competition. Think about what you're doing, man! :eek: :D
 
:thumbup:

Thanks for all the input here. Mete, you have cleared that up for me. Much obliged, bro !
 
Thanks for the info -- I learn something new every day.
 
Thanks again everyone.

dstutts, a freezer is what they keep it in at the local store. Anyway thats all it looks like a , a small chest type freezer.

Chiro, if I made the money bone crackers make, I wouldn't be makin knives, I'd be out spending my money, huntin, fishin, travelin. etc. :D Its just one of those things I've always wanted to try, and when the dry ice thread came out a while back it let me know of a cheap way of experimenting/testing so I can see if its really worth the time and added expense to get a Dewar and nitrogen setup. I've heard it has a big effect and I've heard it doesn't, so now I can see for myself, for only about $10 of dry ice.

Bill
 
My gas guy is looking it up, it's not that I don't believe you Robert , I just want the block temperature out of the book.
you said ~
he did say the LN liquid is -320 of coarse above it where it's gas the temp will be higher.
With-out quoting Mete
I'm trying to say, colder is better in an average situation among us all here.
if your testing,,with something that is hovering around an iffy point
that can be changed and may vary by your own situation, I'd like you to see the full benefit..then you can back up temperature wise knowing the difference... you can always send it out to have it done..then use it as a test point..

LN cost me just over $10.00 for 9 pounds it varies a lot from place to place so shop around..if or when you go that way..

.. a lab dewar On ebay can be had at times for a good price..a lab Dewar is for transporting LN in smaller amounts and it lets the LN
evaporate at just about the right amount of time thus letting the blades come back to room temp slowly..
that's about $1.00 per blade or less..
 
You must log in or register to reply here.
Back
Top