Thin AEB-L heat treating issues

scott kozub said:
Make sure they're as cool as possible before going into cryo or sub zero.
Click to expand...
Is room temperature ok? One of the blades was around 70F IIRC, the other a bit warmer. I could put them in an ice bath or stick them in the freezer for a few minutes if that helps.
 
daizee said:
Yeah, 1/16" or thinner tends to be thinner than the foil folds, which is problematic between plates. I carry my blades in a vertical orientation from the kiln to the plates, but I think the thin ones still warp under their own weight. Vertical plates would be better.
Click to expand...
I mounted my plates to a vise today, but they are horizontal. I have thought about putting pins in one plate and clearance holes in the other for the blades to sit on so I can keep the plates vertical. I have not seen anybody use a vertical quench vise in my internet searching, though.
daizee said:
The baby powder trick is key. Doesn't take much.
Click to expand...
I will get some for my next attempt.
daizee said:
I warm to tempering temp for an hour at least, then bend between wooden vise jaws. Often takes several cycles. Key is to not let the blade cool too much during each attempt, or *snap*.
Click to expand...
I snapped the thinner blade I heat treated. Maybe I left it too hard, I think I misread the tempering chart.
 
I have read in a previous thread (https://www.bladeforums.com/threads/delay-between-pre-quench-and-quench-with-aeb-l.1588976/) that it is possible to do the prequench at 1,725F one day and the hardening the next day. A "snap temper" was recommended after the prequench. I am tempted to try this as I don't think I have enough time this weekend to do it all in one day.

I am wondering about the specifics of the "snap temper". What temperature and for how long?
 
I remember when I first started using AEB-L, that stuff warped just looking at it. Now I've not had a problem with warps in a long time. I do the usual HT/Quench plates, then while still warm from quench plates to an "freeze plate" for dry ice treatment. The "freeze plate" is aluminum bar, usually 1/2"X2" (or 1" wide depending on width of blade). Clamp blade (s) between this pair of aluminum, then put in dry ice (or freezer for -5°F treatment). After removing from dry ice and cooling a bit I've not had any problem with AEB-L warping.

My blades are all profiled only with grinding post HT. I grind making one pass, dunk in water, make one more pass on opposite side. Being sure to alternate sides each pass (possible two passes max on each side). I use .040", .062", .090" as well as some +1/8" AEB-L and it all gets the same treatment. My "magic" moment came when I started using "freezer plates" for the cold treatment. I have clamped 3 blades of same profile between freezer plates for cold treatment.

Good luck - AEB-L is great stuff, since I can't get 14C28N anymore :(
 
Thank you everybody for your help. I really appreciate it.

I just finished heat treating four blades and they all came out of the dry ice pretty straight. One of the thin ones has a slight bow, the other three are near perfect. They are in the oven for the first tempering cycle now.

Again, thank you very much for all of your suggestions, they have made a big difference.
 
Another thing, you can put a few hundred degrees on the spine with a propane torch and bend it straight most of the time after grinding. All of the advice above is solid on avoiding and correcting AEBL warp in my experience.
 
Jason Fry said:
Another thing, you can put a few hundred degrees on the spine with a propane torch and bend it straight most of the time after grinding. All of the advice above is solid on avoiding and correcting AEBL warp in my experience.
Click to expand...

I would stay away from heating it with a torch. A few hundred degrees is not going to make much of a difference. You would need to be at least in the 300° to 500° to get it to the point that you can tweak it. But this is what you do by counter bending while tempering and that doesn’t even work very well. To get Abel to respond you going to have to heat the spine up quite a bit like peters does. But that means you now have soft spots in your blade.
 
I think JT is right. I have not been able to correct the warp with a few hundred degrees, neither through counter bending during tempering nor by bending fresh out of the oven. I might not be aggressive enough, but I bent the blades a fair bit.

The two 0.082" thick blades I did yesterday are perfectly flat. The 0.04" blades both have a slight warp at the front pin hole in the tang. If I hold the blade down flat on a surface plate, the tang is off the plate by about 1mm at the end. If I stack four quarters on top of the end of the tang, the blade sits flat against the surface plate. I am hoping that the scales will keep the blade straight since the force required is so low.

The other thing that I did not notice immediately is that the spine is no longer straight in profile view on both of the 0.04" blades. The handle on both blades now points up a little bit and if I put the spine against a surface plate, there is a small gap of about 0.5mm on one and a bit more on the other. I am fairly convinced they were straight before HT, unless I somehow managed to grind them concave with the spine against the flat platen.

Regardless of the small flaws, I am very excited about the result. I will finish one of the thin blades and see how well it works for making Spätzle, and then see what I can improve on. I think I will get hardness testing done on the santokus in the meantime.
 
JTknives said:
Welcome to the world of aebl. Everything your experiencing is normal for aebl. Only double fold the edges. If and when you get a leak it won’t be from a fold it will be from the bottom edge that is sitting in the oven floor. When ever I have a foil packet fail that’s where it fails. Your going to need more weight then just standing on it unless you weigh 400-800 pounds. My plates are mounted to 9” wood workers vises with a quick release. Aebl has to evenly cool or it warps, and even then it will still try and get away from you. The thing is that aebl is cold rolled (most thicknesses) and coiled. Even if you get it straight out of the quench and temper it’s going to warp and bow as you grind it. I have not found clamping during tempering to help with straightness. Clamping and counter bending on plates while tempering works really good with carbon steel but does not really phase aebl. I find the best way to deal with warps is to get all your heat treating and annealing done and out of the way. Then surface peen to correct the bows. You can surface peening a blade as you grind it as well if you need to. I made a filet knife for my mother-in-law for Christmas’s abs as I was hallow grinding it the tip kept wanting to bow one direction. Just gently peened it on the inside of the bow and back to grinding. It came out perfectly straight.

AEBL is a steel that you will HATE heat treating at first but as you do it more and more it won’t bother you as much as you slowly die inside from all the stress. Once you’re fully dead inside you will fly through the heat treating with out batting an eyelash.

oh and .040 aebl can be a royal pain in the ass. It’s so thin it cools all mostly instantly so it has to get into the plates and clamped with in seconds. When clamped you have to make sure your plates are clamped square and perfectly parallel. If not then you not cooling the blade evenly.
Click to expand...
Can you elaborate on what it means to "lightly peen" the interior of the bend? How big of a hammer? How much force? Just tapping or much more? I'd like to see the Murray Carter video, but it is quite buried in his playlist.
 
Hubert S. said:
The Murray Carter video is here:

Click to expand...

I have two large bowies, I may try some of these tricks on......

One is a forged, differentially tempered bowie from very early in a makers career. Not a straight line on that sucker!! I've fixed a super wonky harpoon grind, but the blade has a bow to the edge.

Have another big fighter with a bowed clip. (Though, on the fighter, it is ground visibly unevenly, but night be harder for me to fix).
 
Last edited:
JTknives said:
Hammers are getting closer.
Click to expand...

Watched the Murray Carter video. What type of hammer are you making?

In the video there was one Japanese hammer with carbide inserts. Is that what will you be making?

Thanks,
Constantin
 
Yes I am making/modifying a hammer and inserting carbide. I have gone through a handful of revisions and have settled on this version and really love it.
 
JTknives said:
Yes I am making/modifying a hammer and inserting carbide. I have gone through a handful of revisions and have settled on this version and really love it.
Click to expand...
Ah, that’s awesome. Do you have any pics. Looked on your website but didn't see any.
 
I took the blades to the engineering department to get some hardness measurements. They consistently measured Rc 63. I double checked a reference sample and it read one point low. I am quite surprised that the numbers are that high. I tempered twice at 375F for two hours each, or at least that's what I set the PID on the toaster oven to.

From what I've read, most people use AEB-L at Rc 61-62 for kitchen knives. I guess I will temper at 400F for another couple of hours.
 
Hubert S. said:
I took the blades to the engineering department to get some hardness measurements. They consistently measured Rc 63. I double checked a reference sample and it read one point low. I am quite surprised that the numbers are that high. I tempered twice at 375F for two hours each, or at least that's what I set the PID on the toaster oven to.

From what I've read, most people use AEB-L at Rc 61-62 for kitchen knives. I guess I will temper at 400F for another couple of hours.
Click to expand...
Before you do that I'd suggest putting a quick working edge on the knife and do a brass rod test. AEBL is extremely tough and may surprise you how it performs at 63. If it doesn't chip out you'll get a little better edge retention out it. My last batch I was going to try some at 63 to see how well they work.
 
You must log in or register to reply here.
Back
Top