HT'ing air hardening steels.

jdm61

jdm61

itinerant metal pounder
Joined
Aug 12, 2005
Messages
47,357
Question. I am getting my HT fixed and tuned up and I am thinking about HT'ing air hardening steels like AEB-L for the first time. Here is my question. If you use foil, do you have to remove the blades from the foil packet before you clamp them between the plates or dunk them in the oil and if so, how the hell do you do that?
 
jdm61 said:
Question. I am getting my HT fixed and tuned up and I am thinking about HT'ing air hardening steels like AEB-L for the first time. Here is my question. If you use foil, do you have to remove the blades from the foil packet before you clamp them between the plates or dunk them in the oil and if so, how the hell do you do that?
Click to expand...


I quench it in the foil. I used to cut the foil off, but that slows down the speed to quench. Especially with thin knives, which are profiled before heat treat, but ground hard.
 
Warren, what size plates do you use for kitchen knives?
Willie71 said:
I quench it in the foil. I used to cut the foil off, but that slows down the speed to quench. Especially with thin knives, which are profiled before heat treat, but ground hard.
Click to expand...
 
jdm61 said:
Warren, what size plates do you use for kitchen knives?
Click to expand...

I’ve got 1”x3”x 30” plates. They only get hand warm/hot for the first three knives (not too hot to touch) then I let them cool down before the next ones. If I’m using 1/4” steel, they get beyond hand touch on the second knife.
 
I have just started with AEB-L but chose to do ATP-641 coating, slow (28 second McMaster Carr) oil quench for 5-8 seconds and then plates, then to LN2. So far I have had excellent success, hitting or exceeding my goal HRCs. Downside is the ATP-641 cleanup, for which I am doing an overnight vinegar soak after tempering.

I may switch to just foil, but my initial knives in AEB-L did not have significant flats and I was worried about getting a sufficient edge quench with plates.

Mike
 
I do not have the tables I follow, but I'll describe the method: I leave the blades in the foil for about 1 minute or more depending on the thickness of the steel. Then I remove the packages from the plates, I open the packages (the blades are around 200 ° C) I watch the blades carefully to see if they are straight. If they have deformations, I straighten them with my hands (at that temperature the steel has not yet completed the transformation and is ductile), then I place them again between the plates so that the steel can complete the transformation.
 
The bevels on AEB-L are not a problem in speed of cooling. Remember, as long as the blade gets below 1100F in less than 2 minutes you're good to go. (per Sandvik on their 13C27). If the plates are getting hot, mist or spray them with water for extra cooling.
 
You guys are using aluminum plates, right? How do you "clamp" them?
 
I attached them to a quick release woodworker's vice set upright. Works a treat.

- It would be scary as balls to try to get the foil off when it is >1900F haha.
 
I think it's helpful to see the process

Here's a video of a friend and me Quenching Nitro V.

Also, you might want to check and make sure you're foil wrapping propely I've seen a lot of different ways for different reasons.



jdm61 said:
Question. I am getting my HT fixed and tuned up and I am thinking about HT'ing air hardening steels like AEB-L for the first time. Here is my question. If you use foil, do you have to remove the blades from the foil packet before you clamp them between the plates or dunk them in the oil and if so, how the hell do you do that?
Click to expand...
 
I'm new to this but have done several knives in AEB-L with 1" aluminum plates in a wood workers vise. It works very well but when I did my first batch I had significant warping (I grind post HT as AEB-L is gummy pre HT). The plates would get hot after a few blades also. I think the warping came at the dry ice bath stage. My last batch I did the following and they came out fantastic.

I use foil with paper and Argon from my Tig just for good measure
I stick 1 foiled blade in the oven for 10 minutes.
I stick my plates in the Dry Ice bath
With 5 minutes left I remove the plates and put them into my vise to prepare for the quench. They're very cold now.
After the blade is done I remove it and clamp between the plates still in the foil (the foil is bulged up from the paper burn)
It only takes a few seconds to get to a touchable temperature
I stick the new blade in the oven and set the timer. ( I have a 1" x 4" by 10" bar of steel in my oven to act as a heat sink so recovery is very fast)
I make sure the blade is cool and remove it from the foil and do a quick check for straight (all were good at this point)
I put the blade back in the plates and reclamp.
I then put c clamps on the plates at each end.
I then take the whole assembly (clamped plates and all) and put it in the dry ice bath.
after 5 minutes I remove the blade and leave in in the bath and put the cold plates back in the vise for the next blade.

Using this method, all 8 kitchen knives (0.1 stock) came out perfectly flat at 63 - 64HRC. There enough going on to keep me busy but not too much that I feel rushed. The other thing I did this batch was a stress relief at 1200 for 3 hours prior to heat treating. That could also be why they came out straight this time.
 
I did the 1200 F for 2 hours stress relief as well, and had no warp on any of my blades.
 
Doi
MBB said:
I did the 1200 F for 2 hours stress relief as well, and had no warp on any of my blades.
Click to expand...
ng the stress relief on my forged carbon steel blades darn near eliminated warpage.
 
You must log in or register to reply here.
Back
Top