Cyrogenics, more questions???

B . Buxton

B . Buxton

Joined
Jul 8, 2001
Messages
3,623
When working with the liquid nitrogen will leaving the blades in the nitrogen for longer peroids hurt them. Say 24hrs. it might not be beneficial past a few hours but will the longer times be harmful?

Is there a time frame that the blades need to be subjected to the LN after they've been heat treated? I'm asking this because I'm wondering about stock piling a bunch of blades before I get the LN. Then doing them all at once, I will heat treat and then flash temper at 300 for 1 hr. to relieve stress before storing them.

Also would a person be wise to put the knives in a deep freezer for a few hours before lowering them into the LN to help decrease the shock factor, or would a deep freezer help that much considering your still going from 0 in the freezer to -300 in the LN and darn big discrepency.

And last, I've read that the prosfessional LN treaters subject there parts to the full cold of LN gradually, so how do you all do it, just drip and leave or is there a more stressless approach??

By the way my steel is 52100, not stainless

Thank you,

Bill
 
The only problems I've had with breakage do to freezing was on blades that were not tempered before freezing. I'd reccommend a full temper before freezing and a full temper after freezing. The freezing will generate untempered micro carbides in the steel. Always temper post freeze...Ed
 
I will have to send my first few blades off for HT. Is there any benefit to a cryo treatment on these blades when I get them back?? I have access to
a Dewar/LN
 
Bill, This is a check to see if I can post here. Tried yesterday and it didn't work. If it works I have more info for you.. Phil
 
Bill, ok seems to work for me today.

A lot that you have asked about has already been said on this forum but at risk of repeating some of it I will tell you how I do it. As you probably know the cryo cycle is used to help in the full transformation to martensite. Some steels do not fully transform when quenched down to room temperture. The higher alloy steels seem to benefit most from this step. If the transformation is not complete then the "retained" austentite can cause problems later. Over time it can transform by itself to martnensite which is then untempered and highly stressed. This can weaken a blade and maybe cause breakage later if there is enough of it. In addition I think it is best practice to get as close to 100% martnensite as possible and then temper it back. At least then we have some control of the crystal structure and do not have to guess at what the end result is. This is mostly a quality control step and some will argure that it is not necessary. It may not be necessary on some steels but I have found that on the CPM steels and 154CM that I can see a benefit. As soon as the blades are quenched down to room temp. I imerse in LN2 directly. I leave them in two hours. More time will not hurt anything, but does not seem to help either. Most of what is going to happen will happen in the first hour according to Ed Severson (metalurgists at Crucible now at a different steel company). As soon as the blade is removed and warmed up to room temp I temper at least once. I have read that it is best to keep the process moving and some steels can "set" and will not transform even in LN2 if enough time goes by between the quench and cryo cycle. I have never had a blade crack like my friend Ed Schemp has, probably lucky. On 154CM, 90V and 10V I can measure a one point hardness increase after the LN2 cycle. So I know on these at least there is a measurable change. All of this is based on what I have read, and discussions with some metalurgists that I have a lot of respect for. Hope this helps some.. Phil
 
Phil your post cleared up a lot of my wondering throughts, very beneificial,thank you. Matter of fact you all helped me. Thanks so much.

Bill
 
This is a subject I'm interested in.

i've looked for a reasonably priced dewar for some time, and did find one on Ebay that I bought.

I had to scrap it though, because the neck opening was too small for the hose at the local LN plant. They couldn't fill it, so I scrapped it. tried two different gas plants.

Does anyone have an idea where I can find a reasonably priced small portable container?

The only ones the local plants have available are the large tanks used by hospitals.

I'm thankful that CPM S30V and ATS 34 can live with a dry ice cryo, but even that is sometimes hard to find. I'd like to have a dewar that can store nitrogen for a few months.
 
Don Robinson said:
This is a subject I'm interested in.

i've looked for a reasonably priced dewar for some time, and did find one on Ebay that I bought.

I had to scrap it though, because the neck opening was too small for the hose at the local LN plant. They couldn't fill it, so I scrapped it. tried two different gas plants.

Does anyone have an idea where I can find a reasonably priced small portable container?

The only ones the local plants have available are the large tanks used by hospitals.

I'm thankful that CPM S30V and ATS 34 can live with a dry ice cryo, but even that is sometimes hard to find. I'd like to have a dewar that can store nitrogen for a few months.
Click to expand...

Don, I have a 10 liter dewar. The neck opening is 2.25" diameter. The brand name is MVE if any of this will help you. :cool:
 
Let's get it straight, people:

for how long will a load of LN last, in a dewar, with occasional
treatment of a blade here and there. I heard very conflicting numbers -
from 2 weeks to few months. Which is it ? :)
 
Rashid, I have a 10 liter dewar with an opening of a little over 2 inches. The length of time for storage depends on how many cycles you do plus how you store Dewar. Large blades evaporate the liquid fast. I usally do the longer blades like fillet knives first so that I can get full immersion by just sliding them in vertical. As the liquid evaporates then go to the shorter blades. As it continues to go down I lay the dewar on its side inside a large cooler chest. Full immersion in one fluid motion is important so that part of the blade is not outside the liquid and seeing a little different temperture. This could cause stresses and maybe do some damage. To calibrate you on how long it lasts, last batch I did 12 blades with one large Chef's knife 6 --8 inch fillet blades and 5 hunter utility blades. I still had enough liquid after 2 weeks to do some small blades if I needed to. Keep the dewar upright in a cooler chest so it is not in contact with the floor and put some blankets over it for insulation. The blankets also help to seal the lid which in my case is just a plastic foam insert. LN2 im my area of California cost $1.50 per liter but I have to drive an hour each way to get it. Phil
 
Thanks again Phil, that was going to be my next question, "what size dewar should a person look for".
I'm like Don, I don't have a dewar yet so I have 6 blades laying on dry ice, there not stainless so the real benefit if any might not be much, but I have read that other people have dry iced high alloy steels over the weekend and on monday the remaining austinite had transformed. That stuff is cold, and with a 15 degree air temp at night it should last a good long while, but its no Liquid Nitrogen.

Bill
 
Bill, dry ice is about -100 F I think. That should be cold enough to get a high percentage of transformation. The only concern I would have with direct on dry ice is that you don't get as good heat transfer that way as you would immersed in a liquid. One side of the blade will be colder than the other side. This could cause differential trasformation of martensite and as a result differential stresses in the blade. Maybe to take care of that an extra temper cycle would be a good idea. Anyhow this is a therory and since we don't have the laboratory equipment to really look at the crystal structure then its just educated guessing at this point. I don't work with 52100 so can't offer any actual experience with it... Phil
 
jhiggins said:
Don, I have a 10 liter dewar. The neck opening is 2.25" diameter. The brand name is MVE if any of this will help you. :cool:
Click to expand...

Jeff, send it to me. UPS COD.

I'll give you a kiss.
:rolleyes:

Seriously, where'd you get it??
 
I don't know Phil, I did a flash temper of 325 and then iced them down, there laying on ice with ice on top. I will temper 3 times at 375 when they come out on Monday, the tests I've done before show these to be good and tough and hold an edge beautifully, the LN would be nice and some day I'll come across a good deal on a dewar, until then its ice time. As far as the total effect on the steel over not icing them I don't know, but there's a lot of things in knifemaking that work and I don't know all the particulars on. Sometimes things are just better because we have more confidence in them. Like I said, I don't know how much the dry ice helps but to me it does help, maybe not as good as LN but until I get a dewar I won't be able to make a comparable conclusion.

Jeff if you'll send it to me I'll give you a beer and a kiss, I don't think there's enough beer to drink you pretty enough to go any farther then that though. hehehhehehehe

Thanks again,

Bill
 
Bill if you can look in your local for a semen service and they sometimes have used semen tanks for sale. Most are from 12 to 16 weeks and have enclosed tops to help hold the liquid better. Some with the dry ice method use acetone to submerge the blades in to get better contact with the steel. MIKE
 
Don Robinson said:
Jeff, send it to me. UPS COD.

I'll give you a kiss.
:rolleyes:

Seriously, where'd you get it??
Click to expand...

eBay, Don. Took a while to get a decent one up for the price I wanted. Can't remember what I paid for it, but I believe it was around $300.
 
Bill, I didn't clearly understand what you were doing. You said laying on ice, didn't realilize you had them "packed" in dry ice. That should give you more even cooling. The 3 tempers are good insurance. When you get your dewar try a blade using the direct imersion and see if you can tell the difference. Phil
 
argel55 said:
Bill if you can look in your local for a semen service and they sometimes have used semen tanks for sale. Most are from 12 to 16 weeks and have enclosed tops to help hold the liquid better. Some with the dry ice method use acetone to submerge the blades in to get better contact with the steel. MIKE
Click to expand...

Hopefully, they've cleaned these used tanks. :)
 
As Bill said before, I break one piece of dry ice into two pieces and sandwich the blade between the two pieces of dry ice.

I do this in a styrofoam ice box that has a tight fitting lid. The ice is still there after leaving it all night.

That assures an even, thorough quench.:)

Jeff, I'll up my offer to a kiss on one cheek (face,that is) and a big old slap on the shoulder.

Now Bill, are you going to beat that offer??:rolleyes:
 
You must log in or register to reply here.
Back
Top