Blades Warping

CDHumiston

CDHumiston

Well-Known Member
I usually use steel from Alpha Knife Supply and I've had no issues at all with warpage.

I heat treated three blades last night using steel from Aldo (NJSB) and all three have a slight warp.

I used the recommended times and temps from the site so I'm not sure if it's just the steel.

All three blades were AEB-L. Hardness came out to 61 HRC after two tempering cycles of two hours each.
 
tkroenlein said:
How severe was the warp? You can do a stress relief before you HT.
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It's not terrible and I don't think some people would notice after the knife is finished. But when I lay the blade on a flat surface and tap one end you can feel and hear it wobble...

I used up all the Aldo steel. I'm going to make some blades of the same shape and size from some AKS steel and see if I have issues.
 
If you're cooling between plates already (are you plates flat?) and it's still warping, maybe a stress relief cycle or two could be the answer. Or a shimmed temper.

Also, to have a way of quantifying the amount of distortion, a surface plate and feeler gauges - or better yet, surface plate and a dial test indicator - works well.

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Search - Grizzly Industrial

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Ebay is a good place to get second hand dial test indicators.

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My plates are flat. When is a stress relief cycle done? Can I do it after heat treat and temper?
 
CDHumiston said:
My plates are flat. When is a stress relief cycle done? Can I do it after heat treat and temper?
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No.

Stress relief is a post profiling and drilling step performed prior to heat treating. There are industry numbers for this. It is one notch above tempering and one notch below annealing. Usually a couple hours at something like 1200F-1250F depending on steel.
 
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CDHumiston said:
My plates are flat. When is a stress relief cycle done? Can I do it after heat treat and temper?
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Heating the steel up and slowly cooling. Well, basically.

Edit: I use the terms stress relief and normalizing interchangeably.


www.thermexmetal.com

What is Normalizing?

Normalizing is a heat treatment process that is used to make a metal more ductile and tough after it has been subjected to thermal or mechanical hardening processes.
www.thermexmetal.com www.thermexmetal.com


Outside of the regular quench and temper stuff, you can really go down metallurgical rabbit hole. Controlling grain size and stuff like that.
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Straightening a warped blade in the temper:

1) Do your first temper cycle as normal. Crooked, warped and all. No changes to normal tempering.

2) After your first temper and the blade is cooled to ambient, assess the amount of warp, and mark the "inside" of the warp.

3) Using an example measurement of 1/8"- place the inside of the warp against an angle iron, and place a 1/8" shim under the point of the blade and clamp in the center of the blade. You have created a "bend" that is 100% opposite of what it is naturally.

4) Perform second temper cycle, and when you're done remove it and leave clamped until it's cooled to ambient.
 
Taz575 said:
Many people use a carbide tipped hammer to straighten warped blades from heat treating. AEB-L loves to warp a lot, too.
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I've got more than a dozen AEBL blades done and the only warps I've had are the blades using steel from New Jersey Steel Baron.

I still have some left and I also got a new shipment from Alpha Knife Supply. I'll be doing some comparison testing...
 
CDHumiston said:
I've got more than a dozen AEBL blades done and the only warps I've had are the blades using steel from New Jersey Steel Baron.

I still have some left and I also got a new shipment from Alpha Knife Supply. I'll be doing some comparison testing...
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I'm assuming it's due to what sort of stresses are pent up in the metal when they get to you. Definitely do some stress relieving on the steel.

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If the blades are warped really bad, take a straight edge find the center of the bend, mark it, take a scribe, make sure you get a good line scratched into the surface.

Now, cut the blade in half along that line.

THEN clamp to blade to something flat.

Now, weld it back together :)

Fixed. You're welcome. I don't usually share this sort of advice. I don't feel many people are worthy of it.

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HAHAHA! Hopefully someone doesn't try welding it back together!

Supposedly AEB-L, especially in thinner stock, was originally made in coils, so it retains memory. I sent some to Paul Bos, no warping and no signs of straightening, other stuff has straightening marks on it from other HT places, so it depends on people's process I guess. I do my grinding post HT, so it makes the warping a bit less and I seem to have less with Nitro V than AEB-L. I wonder if places are doing sheets of it now versus the coils for the knife industry?
 
Taz575 said:
HAHAHA! Hopefully someone doesn't try welding it back together!

Supposedly AEB-L, especially in thinner stock, was originally made in coils, so it retains memory. I sent some to Paul Bos, no warping and no signs of straightening, other stuff has straightening marks on it from other HT places, so it depends on people's process I guess. I do my grinding post HT, so it makes the warping a bit less and I seem to have less with Nitro V than AEB-L. I wonder if places are doing sheets of it now versus the coils for the knife industry?
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I have a sheet from NJSB and a sheet from AKS that are both the same thickness and near identical size.

I plan to heat treat some blades of the same shape and size and see what happens. So far my only warping is from NJSB AEB-L
 
I also use a good bit of AEB-L from NJSB, and like everyone else I get frequent warps, especially on thinner material. I do what tkroenlein does in the temper, but sometimes the blades are still warped. I use a carbide tipped hammer to correct that. It only takes 30 seconds, but you have to be able to grind out the small divots that are left.
 
Owl said:
I also use a good bit of AEB-L from NJSB, and like everyone else I get frequent warps, especially on thinner material. I do what tkroenlein does in the temper, but sometimes the blades are still warped. I use a carbide tipped hammer to correct that. It only takes 30 seconds, but you have to be able to grind out the small divots that are left.
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Those are not cheap! I also only see them in a 2-pound variety.

Any help on where to get one and am I looking at the right thing?

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CDHumiston said:
Those are not cheap! I also only see them in a 2-pound variety.

Any help on where to get one and am I looking at the right thing?

View attachment 80821
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You aught to be able to make your own fairly easily. Get a steel hammer and braze on the carbide.

Thinking about it, if I was to make one (I kinda want to now :D ), I'd use air hardening tool steel for the head, forge and grind it, then when I get it up to temp to harden it, I'd use that heat to braze the carbide. Tempering it shouldn't get it hot enough to melt the braze, so it should all stay together. Then, shape the carbide with a CBN or diamond wheel.

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