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High-Performance Blades Sharing ideas for getting the most out of our steel.

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  #16  
Old 12-06-2002, 09:46 AM
LYNN DRURY LYNN DRURY is offline
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Join Date: Sep 2002
Location: POTEAU, OK
Posts: 196
D-2

GENE, EVEN IF YOUR BLADE IS TAPERED IT WILL STILL SIT
BETWEEN THE HEAVY PIECES. I DON'T BOLT THEM
TOGETHER. I JUST LAY THEM ON THE BLADE.

I DON'T KNOW ANYTHING ABOUT CYRO TREATING OR
THE OTHER WAY OF TREATING A BLADE BEFORE
HEAT TREATING. I JUST USE FOIL.


LYNN DRURY
POTEAU, OK
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  #17  
Old 12-06-2002, 09:59 AM
Jerry Hossom Jerry Hossom is offline
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My good friend and outstanding knifemaker, Rob Patton uses Turco and does well. After hardening he holds the tang with tongs and hits the edge with a blast of shop air, and he's never had a problem.

Lots of people do their own heat treating. I used to, until I realized I just couldn't get the same results as Paul. All of them I know who are doing high alloy steels like D2 use a heat treating oven. Temperature control is very critical with high alloy steels to get a consistent result. By consistent result I mean not just something that will be hard, but something that is hard and tough.

The cryogenic quench usually comes right after the hardening and before tempering. Sometimes with some steels Paul does what he calls a snap temper, drawing the steel up to tempering temperature briefly, before cryo. Cryo is simply leaving the steel in Liquid Nitrogen for a couple hours, or dry ice and alcohol for a few hours, or in your freezer for a day or so. It helps in completing the conversion of Austenite to Martensite.

Let me point something out. With high alloys steels there are no shortcuts to getting a good product. The balance between hard and tough is a very fine line that can only be achieved consistently with a tighly controlled process. There's a very good reason why the Strider guys, Rob Simonich, Trace Rinaldi, Mike Hull, I and a goodly number of other knifemakers who are focussed on very hard use blades use Paul. All of us have done our own heat treating. The Strider shop in particular is one of the best equipped knife shops in the world and they still use Paul because he has over $1 million worth of precision, atmospherically controlled ovens, and can do it better than we can. There are at least two and usually more hardness testing dimples on every tang or every knife I get back from Paul, because he tests the hardness of every knife after every step in his process, to ensure that even his expensive ovens have done the job properly.

Do you need that finely controlled a product? Most don't, but I'm pointing that out to make the point that properly heat treating high alloy steels is not a trivial undertaking that can be done properly with a torch.

I couldn't use quench plates either, because all my tangs are tapered and all my blade are deeply hollow ground. They just wouldn't work for me. Even if they did, I simply couldn't afford to buy a precision oven. Salt pots certainly do work, but that's a big commitment to building them. Rob Patton does his own by the method I mentioned but he uses a $1000 digitally controlled oven, and is meticulous in controlling his process as tightly as he can. I know, I've watched him do it.

There's no witchcraft here. It's all just a matter of heating it to the exact temperture, holding it there briefly, cooling it as fast as possible to below 1000F, completing the quench all the way to -300F if that's what you want, then double tempering at precisely 400F twice for an hour each time.

BTW Gene, I visited your website and I'd greatly admire your work.


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  #18  
Old 08-29-2004, 02:03 PM
Wilhelm Wilhelm is offline
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So quench plate are good? How heavy do they have to be? Do they have to be steel or could they be something like a cinderblock or two? Thanks for the help!
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  #19  
Old 08-29-2004, 03:13 PM
Jerry Hossom Jerry Hossom is offline
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You need something that is a very good thermal conductor and can contact as much of the blade as possible. Cinderblock wouldn't be very good for that, besides the fact that you don't want TOO much weight. The steel is fairly maleable at that point and you don't want to deform it. That's one reason a lot of guys use aluminum plate. Steel works though and it really doesn't need to be all that bulky. The drill is to get the steel below 1000F fast, not necessarily down to room temperature, so it likely doesn't take a whole lot more mass than maybe 2-3 times the blade weight if it's steel and less if it's aluminum.


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  #20  
Old 08-29-2004, 04:06 PM
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rlinger rlinger is offline
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You will need to foil wrap your D2. The long soak time at 1850 F will otherwise cause very deep decarburation.

I like to harden D2 to 60 - 61 Hrc.

Here is a good recepie but in it is a deep cryogenic treatment:

Preheat at 1200 F for 7 minutes (moderately ramp blade to 1200 F and hold 7 minutes)

Austenitize at 1850 F / soak 20 minutes (ramp to austenitizing as fast as possible after preheating)

Rapid air quench (equal air volume on all sides. A good way is point down in a vertical wind tunnel)

snap temper at 300 F / 1 hour

Deep cryo for minimum 10 to 12 hours (longer won't hurt but no extra benefit)

Temper at 400 F / 2 hours

Temper at 375 F / 2 hours
---------------------------------
About 60 to 61.5 (much depends on thickness of blade) The above procedure was used on a small hunter blade and the Rockwell was 60.5 - 61.5 HRc.

Thicker blades may require a little longer soak. Do not over soak. It is best to over soak a little than to under soak a little but too long a soak will enlarge grain structure.

RL


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Last edited by rlinger; 08-29-2004 at 04:09 PM.
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  #21  
Old 02-05-2013, 07:46 PM
Damascusstudio Damascusstudio is offline
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Best way to harden d-2 is vacume oven and nitrogen gas for quenching
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