no Sub zero AEB-L?

Kevin McGovern

Kevin McGovern

Joined
Jul 31, 2015
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the last batch of AEB-L hunters I did I used Dry ice after the plate quench. I am wondering if I can skip this step as I don't really need a hunter to be over 60 RC. It just makes it less convenient since i have to get dry ice before doing my HT and if family overrides my plans for the evening, I am out that money. Thanks in advance.
 
The idea of the dry ice or LN2 is to convert as much of the retained austenite over to untempered martensite, which RA will be significant in alloy steels like AEB-L. The retention of RA gives macro toughness (across the blade cross section), but micro toughness (small apex at the edge) suffers. It is usually most always the best practice to get as much hardness as you can out of the quench, then temper back to desired HRC, for high apex stability.

Exactly how much the RA will affect an edge apex under use has a number of variables, personally I think it is best HT practice to get rid of as much RA as you possibly/efficiently can.
 
You can totally skip it, but the cryo'd blade would be (much?) better.
Your debating creating a blade that is 75% martensite instead 95% martensite (those are just random numbers). I view this similarly to my experience brine and oil quenching shallow hardening steels. IME brine quenched piece was harder and more durable, the logical reason is that it was properly hardened, thus had a more martensite and less fine pearlite, making for a better blade. Now your dealing predominantly with RA, and I was dealing with fine pearlite, but seeing as how the total amount of martensite in the blade is the important part in both equations, I expect your non cryo'd blades to be simaler to my oil quenched blades in relative performance to a properly hardened (so quench and cryo for you or brine in my case) blade of the same steel.
 
Lower the quench temp to 1925'f, keep the soak time at temp to ten minutes, quench in oil or plate quench, faster is better, put it in your freezer right after the quench, this will keep the RA down.

Hoss
 
I would say that if you're selling them then you should try and get the most out of whatever steel you are using. It only cost $15 or so to subzero and is well worth that. It also doesn't take me any longer to do it because it takes an hour or two for my oven to cool off so I can temper.
 
Kevin - AEB-L is (from all reports I've read) "almost" the same steel as Sandvik's 13C26 steel. Sandvik's HT info gives for a -5F freeze (in home freezer checked at -5F) treatment and a -95F dry ice treatment for steels OTHER than 13C26 (AEB-L??). For 13C26 (AEB-L?) Sandvik gives only -95F (Dry Ice) or no -95F treatment. Here you can see both results on Sandvik's site: https://goo.gl/EyLXMZ

Ken H>
 
thanks for the tips gentlemen. Matt, it's not so much the cost as the waste. Since this is now a hobby that pays for itself for me, it is not my priority. While I want to produce the best knife I can, home life trumps hobby. So even if I plan ahead, sometimes that $15 is going to waste when something pops up. The money won't kill me, but I just hate to waste something, and I don't like to keep myself on a rigid schedule, as this is a relaxing thing for me to do and I want to keep it that way. If that makes any sense.
 
It's not a safe assumption that a cryo/cold treated blade will be better. You'll have to try one vs the other. Devin's procedure above is a great place to start.
 
This is the one big reasion I love having a dewer of liquid nitrogen. It's there all the time just waiting for me to use it. That being said I'm not a AEBL-L expert as I have not used that steel but from reading and research there defently is performance to be gained from doing a cold treatment. If your making the knife for you then go ahead and do it how you want, but if this is for a customer then I say you give them the best performing knife you possibility can. Customers look to us knife makers because we provide top quality and don't cut corners.
 
DevinT said:
Lower the quench temp to 1925'f, keep the soak time at temp to ten minutes, quench in oil or plate quench, faster is better, put it in your freezer right after the quench, this will keep the RA down.

Hoss
Click to expand...

Boom. Wouldn't take anyone else's advice without doing my own tests unless it was from Devin Thomas regarding AEB-L heat treat.
 
The "Man" has spoken - I follow DevinT's guidance for AEB-L completely. He IS the expert. Hoss, THANK YOU so much for sharing your knowledge.

Ken H>
 
Kevin McGovern said:
thanks for the tips gentlemen. Matt, it's not so much the cost as the waste. Since this is now a hobby that pays for itself for me, it is not my priority. While I want to produce the best knife I can, home life trumps hobby. So even if I plan ahead, sometimes that $15 is going to waste when something pops up. The money won't kill me, but I just hate to waste something, and I don't like to keep myself on a rigid schedule, as this is a relaxing thing for me to do and I want to keep it that way. If that makes any sense.
Click to expand...
I understand bud as my family is always first too. I put my knives in the oven and once I ramp them to 1950 I have about 50 mins until I have to quench so I run to the grocery and grab some dry ice. If -5 will work then I'm not buying anymore dry ice! I will do a few test next time I'm heat treating.
 
Kevin McGovern said:
thanks for the tips gentlemen. Matt, it's not so much the cost as the waste. Since this is now a hobby that pays for itself for me, it is not my priority. While I want to produce the best knife I can, home life trumps hobby. So even if I plan ahead, sometimes that $15 is going to waste when something pops up. The money won't kill me, but I just hate to waste something, and I don't like to keep myself on a rigid schedule, as this is a relaxing thing for me to do and I want to keep it that way. If that makes any sense.
Click to expand...

I can 100% relate to trying to enjoy it and not wanting to waste... however, I'd rather waste 15$ worth of dry ice if that's all it cost than skip a step that does that much to help. if it makes you feel better, I pay $60 for a bag of dry ice and usually don't get my money's worth out of it for the same reason, but I feel better getting that last few percentages out of a knife I'm gonna sell.
 
Matt R said:
.......... If -5 will work then I'm not buying anymore dry ice! I will do a few test next time I'm heat treating.
Click to expand...
Understand, while -5ºF "might" be "pretty" good, it's NOT going to be as good as -95ºF. Take a look at the links I gave, the -%ºF was NOT for AEB-L (13C26???) but for 12C27 or 14C28N Sandvik steels. Even there Sandvik shows the -5ºF does NOT equal .-95ºF.

Ken H>
 
The whole point of the lower temperatures Devin posted is to minimize the retained austenite so cold/cryo aren't necessary. There are other issues that are affected so you have to decide what the primary goal of the knife is and choose accordingly.
 
A year or so back I did the same cutting test with one knife at 60Rc (no sub zero) and the other at 62Rc (with sub zero).

[video=youtube;sdhOCjaLWlw]https://www.youtube.com/watch?v=sdhOCjaLWlw[/video]

[video=youtube;sUmzIsXGCWM]https://www.youtube.com/watch?v=sUmzIsXGCWM[/video]
 
I never used AEB-L steel but I will say My experiences with hardening stainless steels. If 56-57 Hrc is enough for You just temper it at about 180°C (356F) for 2 hours (two times is better). There will be more austenite against cryo (about 15-25% against 3-10% with cryo). I think it doesn't make big difference for ordinary use. I use 56-57 Hrc or so on My kitchen knives. I do HT without cryo everytime and I perform tests by chopping antler or brass rod (usually rod because it's handy). Here is picture from testing. White marks are from antler, blade is without damages (try zoom it).
 
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