Whole batch of AEB-L warped convex along spine after HT, what could I have messed up?

M

MM52100

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Dec 29, 2020
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Not left to right they are dead straight, but convex along the spine. All 4 blades. Only shaped, no grinding. Foil wrapped, plate quenched, -40f freezer cold treatment, 350f tempering.

Only thing I can think of is the spine stayed cooler in my HT oven than the edge. The spines were down and I did all 4 at the same time. I usually only do 1-2.

Anyone else ever see this?
 
Two had a 15 minute soak at 1750f then plate quench followed by 1925f 15 minute then another plate quench. The other two straight to 1925f then plate quench. All four went into the oven at the same time for the final austentitize cycle. All look the same. I have a home brewed HT oven similar to an evenheat that usually produces straight steel.
 
Do you happen to have a before and after photo? Or even just after photos, it’s normal for steel to move and change dimensionally in the heat treating the longer the blade the more noticeable some changes may be. It’s hard to really say without seeing the warp or movement.
 
Here are some images. All the spines were dead straight or slightly concave before HT, I ground them flat. 4 are AEB-L and have the bow. The straight one is a 52100 that I did everything the same way but with Larrin's DET cycle and quench 1700-1460-1460-1525f.

I might grind one up now and do it alone to see what happens.

Pictures
 
I have noticed this occasionally with mine. I think it occurs at the handle transition where the blade is tall and the handle is shorter. The handle likely quenches a shade faster, and the blade side being "different" produces a little warp. I just grind it flat again. No big deal in my book.
 
Cool, thanks. I already did some grinding and they are straight again. Just wanted to make sure I wasn't doing something that could be easily remedied.

Much appreciated.
 
I'm pretty sure its from the steel sagging under its own weight at aust. temp. This happens to me with almost every AEBL knife I make thats longer than 10" oal. My HT of AEBL consists of a "pre-quench" at 1725° before austenitization at 1970°, and I've found if I rotate the blades in the kiln (edge up/edge down) between quenches that it mitigates the warping quite a bit.
 
Just as some reference (as I use AEBL frequently) I put in blades at room temp in an Evenheat, rapid to 1565 for 15 mins normalization and then rapid to 1950 austentize for 15 mins. Air quench between aluminum plates. 2x temper 350 for 2 hours (and i put them back in the plates between cycles but not sure that matters). I've never had a warp with this recipe...HRc 60ish...I bevel grind post HT. My 2 cents...
 
On the subject of AEBL. I am about to use some for the first time. How much does the ramp speed matter? My oven is not very fast from 1600-2000 degrees. I haven’t timed it but it’s quite a while. Can I just stick the blades in at 1925 and soak or is the preheat absolutely necessary. I read Larins article on AEBL and he doesn’t mention the preheat in there.
 
MasonOstrom said:
On the subject of AEBL. I am about to use some for the first time. How much does the ramp speed matter? My oven is not very fast from 1600-2000 degrees. I haven’t timed it but it’s quite a while. Can I just stick the blades in at 1925 and soak or is the preheat absolutely necessary. I read Larins article on AEBL and he doesn’t mention the preheat in there.
Click to expand...
No preheat all soak once oven has stabilized at temperature for a while.
 
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