# Heat Treating



## watercrawl (Jun 9, 2011)

I found the following on heat treating AEB-L on the net...specifically on www.alphaknifesupply.com:

Heat Treating Information: 
Preheat: Heat to 1560° and equalize.
1920°F Austenitize: Ramp to 1920°F and hold at temperature for 15 minutes. Oil or plate or air quench as quickly as possible.

1975°F Austenitize: Ramp to 1975°F and hold at temperature for 5 minutes. Oil or plate or air quench as quickly as possible.

Cryogenic Treating: To get the most from AEB-L you must cryo. Cool to -95 °F. No soak is required.

Temper: Temper immediately after hardeneing or cryo. Temper at least 2 times for two hours each time. Use the table below to achieve desired hardness.







I'm bound to start searching what the difference between the two austenitizing temps do, but I would like some input here as well. It seems weird to me, these forumulas. 

So let me see if I get this right:

Start the oven, get it to 1,560 degrees

Open door, insert blanks, close door

Turn up temperature to either temp

Wait the 20 or so minutes it will take the oven to get there

Then let it soak for 5 or 15 minutes at either 1920 or 1975

Remove blanks immediately and quench

Cryo in some stupid cold liquid

Then temper immediately based on the table

That sound right?

What will oil versus plate versus air quenching do to AEB-L? 

Lot's of questions....sometimes the engineer in me sucks! :razz:


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## Larrin (Jun 9, 2011)

That would work.

Oil quench would give higher hardness. Plate quenching will give similar hardness to oil quenching but will keep it straighter. Air quenching is the least severe so if you had a complicated shape (probably not a knife) it would be the best.


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## watercrawl (Jun 9, 2011)

Thanks Larrin!!


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## Michael Rader (Jun 10, 2011)

Ha ha. I want some "stupid cold liquid" for my shop. Would Bud Lite count?

I would suggest seeing if Devin Thomas would either chime in here or give him a call. I believe he is the AEB-L heat-treating expert in the knife-world.
-M


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## watercrawl (Jun 10, 2011)

Michael Rader said:


> Ha ha. I want some "stupid cold liquid" for my shop. Would Bud Lite count?
> 
> I would suggest seeing if Devin Thomas would either chime in here or give him a call. I believe he is the AEB-L heat-treating expert in the knife-world.
> -M


 
I'm trying my best to not bother that man any more.  I still want to spend a few days at his side and don't want to wear out all of the questions I'm allowed before then.


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## watercrawl (Jun 10, 2011)

To be clear, this thread is about a publicly available heat treat formula for AEB-L. It is in no way an attempt to pry out trade secrets from any one. I've never heat treated anything myself and I'm trying to figure out how to do it and what different things do and such. If I wanted someones specific formula for a heat treat, I'd call them and ask if they'd give it to me. However, in my situation I don't feel that's the right thing to do. If anyone wants to publicly reply to this thread with help for me, I welcome that help with open arms. If they don't, I'm good with that too. If someone would like to send me a private message for the same reasons, I'm good with that too of course. 

Sorry if this has caused anyone any stress.


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## Eamon Burke (Jun 10, 2011)

That sounds like someone got really upset. I'm an outsider, and I'd like to say that this didn't look to me like Adam asking for anyone's trade secrets or guarded knowledge. Nobody is going to fault makers, smiths, or otherwise for telling people some information is top secret.


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## rockbox (Jun 10, 2011)

I don't think anyone got upset. I just think Adam is making sure the knife makers here don't feel any pressure to give any info they don't want to give up. Kind of like when everyone was pressuring Dave on who manufactured his 10K stone on KF.


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## Eamon Burke (Jun 10, 2011)

lol I heard about, but missed that one. It's really silly to take things that far. TELL US WHO IT IS! HOW DID YOU HEAT TREAT THIS BLADE?! HOW DO YOU DO SUCH GOOD WORK?! 

Reminds me of this:

[video=youtube;U6VPEcj77v8]http://www.youtube.com/watch?v=U6VPEcj77v8&feature=related[/video]


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## Larrin (Jun 10, 2011)

No one's upset that I know.


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## watercrawl (Jun 10, 2011)

rockbox said:


> I don't think anyone got upset. I just think Adam is making sure the knife makers here don't feel any pressure to give any info they don't want to give up. Kind of like when everyone was pressuring Dave on who manufactured his 10K stone on KF.


 
Yeah, this.


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## watercrawl (Jun 10, 2011)

Larrin said:


> No one's upset that I know.


 
Nor I! The above post was not a response to someone getting upset. Somebody made some comments about my thread and I wanted to make extra clear my intent.


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## rockbox (Jun 10, 2011)

Larrin, 

Does AEB-L benefit from triple quenching?


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## Larrin (Jun 11, 2011)

rockbox said:


> Larrin,
> 
> Does AEB-L benefit from triple quenching?


In triple quenching fast thermal cycles are used to refine the grain size. This works because you are forming a new phase: austenite. After quenching rapidly martensite is formed from austenite. Then once the steel is heated to austenite again, then new, small austenite grains form at the grain boundaries. So the new grains are small and the old grains continue to grow. While old grains reach a point where they are replaced by smaller grains, there is a functional limit, usually 3-5 cycles, but this depends on your heating and cooling rate and hold time, etc. The problem with air hardening steels like martensitic stainless steels is that a conventional triple quench creates disproportionate grain growth which creates a duplex grain structure with very small grains and very large grains. Appropriate temperatures have to be used which are dependent on steel type.


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## ajhuff (Jun 11, 2011)

Is cryogenic HT being done at higher temperatures these days? -95F is not very cold. I remember cryo being done in liquid nitrogen to convert retained austenite. Is the Mf temp of this AEB-L that high?

-AJ


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## Larrin (Jun 11, 2011)

ajhuff said:


> Is cryogenic HT being done at higher temperatures these days? -95F is not very cold. I remember cryo being done in liquid nitrogen to convert retained austenite. Is the Mf temp of this AEB-L that high?
> 
> -AJ


 Probably considerably higher. Colder temperatures give some leniency as far as time between quench and cryo, however.


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## peterm (Jun 12, 2011)

Wow Larrin! Are you going into your Ph.D. program to teach it? You seem to know answers to every question already!


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## rockbox (Jun 12, 2011)

I think AJ is also a metallurgist, so we two in our mists now.


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## Larrin (Jun 12, 2011)

Adam, here is more information on AEB-L/13C26:

https://rapidshare.com/files/2731329401/AEB-L.pdf

http://www.smt.sandvik.com/sandvik/...025299743D103B04C1257428004F0A91?OpenDocument

I've never used rapidshare so let me know if that upload worked.


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## watercrawl (Jun 16, 2011)

Thanks Larrin.

Not sure about the RapidShare thing Larrin, I cannot find a download link. Don't know, could be missing something.

The 13C26 link worked though. 

So that I understand, I assume what we're talking about here is the "Batch Hardening" tables, yes?

If I'm reading that description correctly, it says to:

Equalize your oven to 1,560 degrees for 30 minutes

Put the knife(s) into the oven, ramp up to 1,975 degrees and hold there for 30 more minutes

Then take the blanks out and immediately quench them down to room temperature then immediately cryo them to -95 degrees

Then temper at 345 degrees to get to 62 HRC

This sounds very similar to the recipe above with the exception of the 30 minutes at high temp versus a mere 5 minutes at high temp in the AKS recipe. The 30 minutes noted here is even longer than the time stated at the lower temp from the AKS recipe. 

Anyone care to share what the difference might be? 

The blade (AEB-L in this case) would need to be wrapped in foil (Heavy Duty or the Easy Release stuff?  ) for reasons I'm not confident on but I believe has to do with oxidation. 

Plate quenching....does it need to be done with those plates you can buy? Or are there alternative methods? 

How does one know it's safe to put into the cryo? Cool enough to handle bare handed? Does it need to be cooled first in the fridge?


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## Larrin (Jun 16, 2011)

You would actually be using the piece hardening instructions, unless you're giving instructions to a larger heat treater or you have a very large heat treating furnace and many knives that you haven't told anyone about. The pdf I tried to put on rapidshare has a nice chart for holding time at austenitizing temperature. I'll e-mail it to you. The longer time required by what you're looking at is because you're looking at the instructions for the batch hardening. The hold times for piece hardening on the Sandvik website look fine though. 

You can use just about any plates as long as they are thick enough. 

You don't need to cool it in the fridge first. Around room temperature is fine.


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## watercrawl (Jun 16, 2011)

Larrin -

I'm sorry, I meant "Batch Furnace", not "Batch Hardening". There is also a "Belt Furnace" option, which I don't understand so I thought an oven like we're talking about would be the "Batch Furnace". 

I would want the "Piece Hardening with Deep Freezing", correct?


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## Larrin (Jun 16, 2011)

watercrawl said:


> Larrin -
> 
> I'm sorry, I meant "Batch Furnace", not "Batch Hardening". There is also a "Belt Furnace" option, which I don't understand so I thought an oven like we're talking about would be the "Batch Furnace".
> 
> I would want the "Piece Hardening with Deep Freezing", correct?


Even though you won't be using a belt furnace you will be doing piece hardening so it is the one you should look at.

Piece hardening with deep freezing is correct.


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## rockbox (Jun 16, 2011)

watercrawl said:


> Larrin -
> 
> I'm sorry, I meant "Batch Furnace", not "Batch Hardening". There is also a "Belt Furnace" option, which I don't understand so I thought an oven like we're talking about would be the "Batch Furnace".
> 
> I would want the "Piece Hardening with Deep Freezing", correct?



I think a belt furnace is what Wusthof uses. They run the blades down a belt and the time is controlled by how fast the belt goes through the furnace. Its like the pizza ovens they have a Costco and Sams. Stick the pizza in one side and its finished when it reaches the other side.


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## watercrawl (Jun 16, 2011)

Kind of assumed that's what a belt furnace was, but didn't know enough to be sure. 

Thanks Larrin, I appreciate it.


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## rockbox (Jun 16, 2011)

Buy the quenching plates, unless you like seeing the flash from the burning oil. It may be cheaper just to get aluminum plates from your local metal supplier.


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## watercrawl (Jun 16, 2011)

Larrin -

Got the email....thanks.


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