Normalizing AEB -L, Grain Refinement, etc. Need some help!

A

Augus7us

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Oct 9, 2014
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Hey All,

Getting tired of dealing with twisted AEB-L kitchen knives. I think you can look at them funny and cause a warp with my current process :mad:

I'm going to try a few different changes to alleviate this but I also wanted to hear from you all.

I've heard they should be normalized, snap tempered, grain refined due to the steel coming off a roll. But I could not come across consistent routine folks are using. If anyone would be so kind as to enlighten me with a working normalization grain refinement program with temps I would be very grateful!

If you are familiar with any other AEB related nuances that can end in a warp or twist and your remedies, please feel free to share.

Thanks,
-Clint
 
Watching this thread to learn, I've wondered this too.
For now, my approach is what you'd naturally expect a blacksmith to do- get em out of the foil before they cool too much and straighten them on an anvil with a mallet or brass hammer. Occasionally one will bend a little in the subzero, but it can almost always be straightened in tempering.
 
If you are grinding them really thin you might want to try grinding one post heat treat to see how it turns out. I've been using 1/8" stock and have only ground it post heat treat. Plate quench with sub zero and no issues.
 
What's your current method?
If you aren't plate quenching, you should be. If you are, and still getting warpage, I don't know.

As far as grain refinement, that's not usually an issue with steels that have a high hardening temperature.
 
I only made one kitchen knife out of AEB-L so far. My procedure was same as LoRez and no real issues. Grind post HT. Just checked my notes for what I did with that knife:


(I didn't make a note about it but I probably surface ground the stock down to .085")

-Wrap in stainless tool wrap
-Heat to 1560˚, hold 3 minutes, ramp up to 1990˚, hold 3 minutes
-Plate quench, (I didn't write it down but pretty sure I quenched in the foil wrap for no longer than 30 seconds - my quench plates are 2" X 4" x 18" 6061 aluminum bars)
-1 hour sub-zero bath consisting of denatured alcohol/dry ice immediately after removing the blade from the foil
-Temper 3x @ 350˚, 2 hours each cycle - the 3rd cycle was to correct a slight wiggle.


Others with more experience with AEB-L than I can give you better HT specs. But from my research it didn't appear that normalizing was recommended or necessary, at least with stock removal.
 
This.
Lo/Rez said:
If you are grinding them really thin you might want to try grinding one post heat treat to see how it turns out. I've been using 1/8" stock and have only ground it post heat treat. Plate quench with sub zero and no issues.
Click to expand...
 
Its .110" thick and I do plate quench. One of the things I intended on trying was grinding one 50/50 pre/post HT and one entirely post heat treat to see what changes. But mostly the issue isn't post HT its while grinding it pre HT.

I should have elaborated a bit more, the main issue I am running into is getting "bacon" waves while grinding. Mostly on the spine as I'm probably grinding out any waves near the edge. I tried to eliminate myself as the cause by putting all lateral force against the platen when I'm grinding, index fingers behind the platen and thumbs putting pressure on blade. That said I could still be causing some of it.

Based on what I read about it coming from a roll it does seem like it could be warping some due to this and me heating up the steel on the grinder. So in addition to the grinding post HT I was interested in normalizing to see if there is any difference.

So two questions:

For those that have normalized AEB what is your routine? Mainly temperature and times.

If I do normalize it do I have to also worry about grain refinement?

Thanks All
 
You keep mentioning normalizing ! That complicates things ! Warping is a product of stresses from cold working or grinding. HT procedures also can add to that.
Most thorough, easiest solution is Sub-critical anneal/ stress relief. This is done at 1200F for two hours .You won't be getting scale or decarb at this temp nor significant grain size change. Do this before you start
.If you do this before you grind you might also repeat after grind.
 
I feel that I am pretty good at straightening knives and/or keeping them straight and AEB-L is the only steel that has really given me problems. I did an entire run of Petty's that I just could not keep straight. (and lost the run) Every one would warp after plate quench... I'd straighten then grind gently... they would warp right back. I do all of my grinding post heat treat. Some of the other AEB-L in the same batch was just fine, I guess I got a bar that had been highly stressed.

I'm trying Mete's advice next round!
 
Thanks for the information Mete. I will give that a try on my next set. I'm going to try and get three in that are identical; 100% pre HT (doing a few things different this round), 50%/50% pre/post HT and one 100% post HT. I'll let you all know how it goes.

I mentioned normalizing as I thought that was the best way to remove any stressers from being rolled or worked before it gets to me. I buy from Aldo and I've heard it was cold rolled before he gets it, I very well could be wrong on this as I can't find where I read it. But either way I was assuming normalizing was the way to go to alleviate any past stress inducing work. I'll definitely will give the sub critical anneal you mentioned a go.

Its the compound warps that get me, one warp making an arch when I set it on my granite isn't to bad, but when I look at it down the spine and it looks like a horse trail... I have trouble fixing it without making it worse.

-Clint
 
Lo/Rez said:
If you are grinding them really thin you might want to try grinding one post heat treat to see how it turns out. I've been using 1/8" stock and have only ground it post heat treat. Plate quench with sub zero and no issues.
Click to expand...



They'll warp plenty post HT, I made a handful of pairing knives that were 0.040 thick at the spine above the choil. Each pass on the grinder would warp one way, and you'd have to grind the other side to warp it back. Broke a few trying to straighten with conventional methods.


FWIW, these were plate quenched and LN2 cryo'd, left at 63 RC.
 
Is there any possibility that tempering them prior to grinding would help? Just thinking out loud and hoping someone with a lot of experience can answer this one.
 
Javan I've heard others grinding back and forth to "reverse" the warp when reading old threads. I don't think I was as diligent with that as I could have been grinding this one so I plan on keeping that in mind on the next few and paying a lot more attention to it while grinding.

Lo/Rez if he is getting a warp grinding at 63HRC then I can only imagine tempering would make it easier to warp the blade. My theory is that because they are thin and I am imparting some level of heat and pressure on the blade while grinding, if my pressure is not directly applied against the platen then I risk warping it. At least I think that is one of the reasons I'm running into this many warped areas. I've noticed when annealed you can bend thin AEB pretty easy by hand or by accident. But I've also noticed that I can easily compound the problem by trying to fix it. If I'm not bending in exactly the correct place I will create a compound warp.

After reading Stuart's comment I checked the other blade I profiled on the granite today and it was pretty much dead straight in its current form. Though that will change once I start to grind on it :D I did order this batch in a 6"x48" sheet vs the 2" bars I was ordering.
 
The speed at which you are making your passes across the platen may contribute to the heat build up. I make many fast passes vs doing less, but taking off more at a time. Might be a factor, but probably not.
 
I have done 2 aeb-l's both 1/8 I HT'ed+cryo+tempered then grind the bevels in, dunking every pass to keep cool takes a lot longer but they are arrow straight.
 
KUNTZI66 said:
I have done 2 aeb-l's both 1/8 I HT'ed+cryo+tempered then grind the bevels in, dunking every pass to keep cool takes a lot longer but they are arrow straight.
Click to expand...

No disrespect intended, but in fairness, 1/8 is a huge difference from 1/16 and under. I have no problems keeping this stuff straight at 1/8" either, except when they taper to zero. Once you get below a certain threshold I think this stuff simply moves based on how much material you have backing the opposite side when you're grinding.


Believe me when I tell you, you've got no choice but to dunk each pass when you get this thin, but it doesn't seem to help. Bear in mind that making super thin knives is a whole different ball game. Most people never even get much below 1/16 even at the very tip of their fixed blades.

Still, for whatever reason, AEB-L seems tougher to keep straight. Although I think a big issue with this is just that it doesn't respond to straightening techniques very well. Worth the effort IMHO though. Only stainless I'm using anymore.
 
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