Addressing warp before quenching

Knight Owl Forge

Knight Owl Forge

Bladesmith
Joined
Mar 14, 2017
Messages
75
Hello,

I have mastered fixing warping after heat treatment using clamping jigs, 3 pin, etc, etc... One thing I can't figure out for the life of me is how to address warping before quenching. For example... I recently forged a blade, profiled it, and roughed in the bevels to make sure everything is even and flat. I generally use a flatter at the end of forging and flip the blade over and flatter it up and down both ways.

I then go to normalize the blade in the forge and can watch it pick up a warp... Okay, easy fix- whack it on the anvil with a soft hammer or whatever... Put it back in to normalize and as it heats up it takes on a warp again--straighten on anvil. The repeat that continuously until I finally just say eff it and get it straight as I can, quench, and fix warps later.

How can you address this warping that occurs when you thermal cycle and normalize before quench? I like to make thinner knives and it is especially noticeable.

Thanks
 
Wish I could help, but I have never had troubles with warping in normalization. What steel are you using? How thick?
 
The best way is to use a 'stress relieve temper 'or ' subcritical anneal ' This is usually heating at 1200 F for two hours , then straightening where necessary This will not cause significant scale or decarb.
Complaints of stainless steels warping are sometimes introduced in the stresses of forming rolls of steel .Flattening the steel into sheets still has the stresses of rolling
. Proceed as mentioned !
 
mete mete has a good point. Do you anneal the blades after forging? This may be why i never have had a problem. I forge the blades and then with the forge still hot, I put the blades in, turn off the burners and stuff all of the openings (even the burner port) with inswool. The blade will get up to ~1500F with the heat in the forge and then cool down slowly. I let it go overnight.
 
mete said:
.Flattening the steel into sheets still has the stresses of rolling
Click to expand...

This happens every time I use Sandvik stainless steels (13c26, 14c28n) they came in flat sheets that once where rolls. If you see the sheet alone is flat as it can be, mostly due to its own weight, but the minute you cut a piece it curls like a banana peel.
This was a real problem every time I cut them using laser, they returned like curly fries...LOL
My solution was a double process, first heat to 900C (1650F) and cool them between aluminum bars with a weight on top, they came straight as an arrow but somewhat hardened (~50RC) so then I cycle them at 650C (1200F) and let them cool overnight in the oven, next day they are straight and soft.

Pablo
 
if i had a blade that would re-warp after straightening when i was normalizing or stress relieving or reducing grain size, instead of straightening it i would go the same amount of warp "past" straight. that way the next time it warped, it would warp itself straight. (i have used this on carbon steels)
 
When straightening a blade in the annealed condition, it’s best to over bend then go back to straight. If you just go to straight, it will have a memory.

Edit: John A. just posted something similar. Thanks, I should pay attention more.

Hoss
 
I have been quenching a lot of chef knives with hamon (1095 and W2, I use a dfogg HT drum forge) and noticed if I nail the aust temp I get less warps. May not be easy to do in a kiln but with my w2 and 1095 I have about a 5-10° window with my thermocouple readout, as long as I soak within this window I find I rarely get any distortions.
I also normalize once hot (1650) and twice in aust range (1450-1500). I use to do a few 1200 cycles but rarely have a need to drill holes and find I get cleaner cross sections grinding in pearlite as opposed to annealed steel (soft steel is grabby)
I also leave an edge thickness of .03" prior to quench, any thinner and parks50 will sometimes make lasagna.
-Trey
 
I will give annealing a shot and also taking a blade past straight and then bending it back.

Both suggestions sound reasonable! Thanks everyone.
 
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