Warping in dry ice?

E

elementfe

Joined
May 3, 2008
Messages
1,436
I'm trying to track down why my last few blades in CPM154 and 440c warped.
These are flat grind folder blades, from 3/32 and 1/8, I just laid them between two chunks of dry ice for the subzero phase.
Is it possible that they'd pick up a permanent tweak from that, or is it more likely happening earlier in the process?

Another post today suggested that you can straighten after plate quench with AEB-L, same with these two steels?
Thanks for any insight!
Andy
 
elementfe said:
I'm trying to track down why my last few blades in CPM154 and 440c warped.
These are flat grind folder blades, from 3/32 and 1/8, I just laid them between two chunks of dry ice for the subzero phase.
Is it possible that they'd pick up a permanent tweak from that, or is it more likely happening earlier in the process?

Another post today suggested that you can straighten after plate quench with AEB-L, same with these two steels?
Thanks for any insight!
Andy
Click to expand...

I would think that won't give you even contact.

why not use a solvent like the acetone ?
 
Yes, they can warp in dry ice. I plate quenched a batch of blades a few weeks ago. They didn't come off the plates straight, but I bent them all straight by hand before they got hard. I put them in dry ice with kerosene, and 8 of 11 came out warped. Makes Peters or Paul Bos look more tempting every day. You can straigten them in the temper cycles, but it's a pain.
 
Jason Fry said:
Makes Peters or Paul Bos look more tempting every day.
Click to expand...

Word to my brother.

The economics of heat treating my own stainless just doesn't add up anymore. Stainless foil is expensive. So is dry ice, kinda. Electricity too. And then when 8 of 10 of mine can be reliably counted on to be warped, the number of temper cycles necessary to unkink them all just about drives me bonkers. NO MORE.
 
I put mine in the dry ice slurry just the same way I quench... with an even motion and no side to side movement until it seems they are cool.

Any uneven rapid cooling or heating can warp a blade especially during heat treat.


"Cold Quench" this was done after the blade had cooled in plates and then water...

 
Thanks for the replies, everyone!
Count, the blade kind of melts into the bottom block, and with a flat block on top it *seems* like it would become the same temp as the ice fairly quickly...could be mistaken on that one.

Daniel, have you managed to avoid warping issues by doing that? It seems like the most sensible approach. I keep wondering if the slurry is just slightly higher in temp than plain dry ice- it wouldn't take much to miss the benefit, since AFAIK the conversion happens just above dry ice temp.
 
So far they are coming out very straight, I have only sub-zero'd 20 or so blades though. The last batch seemed to be dead straight according to my surface plate, I was impressed.

I'm pretty careful to keep my grinding cool even before heat treat. I only hand sanded my flats before heat treat on the recent batch, they were folder blades so it didn't take much.
 
When I quench in frozen plates (still in the foil) occasionally they come out warped before
the dry ice or LN. After the initial quench in the frozen plates I put them back between the plates
for a couple of min and 10" "C" clamps for maybe 2 min. Directly into the freeze with liquid, if its
LN I suspend them a bit before immersion- Less shock? Can't remember the last time I had one
I would call warped.
Ken.
 
I believe that it is also very important to keep them well supported and not leaning while heating to harden. Taken them to 1850 and soaking for 30 minutes makes them very susceptible to movement. Even the movements to the quench plates while at those temps could cause problems. Much better to keep them true through the whole process than deal with it at any point. I don't believe I have had any problems from the dry ice, but, I use a slurry. I do think laying it sideways on a piece of dry ice would cause the blade to cool more rapidly on that side and could cause problems
 
I recently did some chef knives in 3V and when I brought the longest one , about 15" OAL, out of the oven it was curved significantly, think banana. It plate quenched very back to flat. Into dry ice slurry and then to quench. It came out with a very minor edge wave near the heel and a slight bow that straightened with a temper after being clamped flat.
I would wager that like SteelSlaver commented, laying between the dry ice is not an even contact and allows one side to cool faster than the other.
 
Really appreciate the tips, everyone, thanks! After all the careful grinding to keep it all straight and true, it's pretty disappointing to have to grind it straight again.
 
You must log in or register to reply here.
Back
Top