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Author Topic: Heat Treating 2013  (Read 4316 times)
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Ed Fowler
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« on: June 12, 2013, 11:04:44 AM »

  This is a fairly detailed description of our heat treating methods and theory as they exist at this time.   I put it all in one place and describe then each in turn. Any comments are welcome.                               

                                                        Why Forge

There are several reasons why a maker chooses to forge a blade rather than make one by the methods generally referred to as Stock Removal. Some forge simply because they enjoy learning and practicing one aspect of the art of the blacksmith.

Availability of desired material: A maker may not be able to obtain the metal of his choice in the dimensions he can work with, for some forging is the only way to be able get the metal in the dimensions and condition he wants.

Forging can conserve time and materials: Some materials are expensive and the stock removal method leaves a lot of steel lying on the floor of the makers shop along with the cost of time and other materials. Forging for high production without wasting materials and saving time are well documented, the ABS has some demonstrations where makers can complete a forged blade including hardening, tempering, completing the blade and adding a handle in less than an hour.

Forging for the beauty of Damascus: Naturally if a maker wants to make art knives using Damascus steel he can buy it from one of many makers who make it for sale or make his own. If he chooses to make his own he enters in to a realm with a lot of room for individual expression and creativity.

The legends of the performance qualities of the forged blade: is another reason some of us chose to forge Steel. Greatest of these legends in my book is the story of King Arthur and Excalibur. The quest for performance in the realm of the forged blade is the realm I chose to pursue and have for sought for most of my life we have invested over $70,000 in the development of the following heat treating methods. All of them may not be necessary for your desired performance level of your blades, therefor I suggest that you try what you can, test the performance qualities of your blades and make your decisions based upon your personal testing.

                          Our Heat Treating methods for forged 52100& 5160

A reader asked me to explain the heat treating methods we use when we seek the High Endurance Performance Knife. Rather than repeat what I have written in the past about forging, I will answer his question starting with one of our blades after it has been forged to the desired shape at low temperature starting with a 6 ? inch round bar of high quality 52100 steel resulting in a high rate of reduction by forging.

Our performance testing indicates these methods work well with material that knows a high rate of reduction by forging at low temp. 1625 to about 1400 f.  we quit forging when the steel does not move readily under the hammer. (You can predict 1625 f. when your steel is nonmagnetic and the slag that comes off of the blade while forging is either nonexistent or very fine like powder snow). I believe some of the following methods can also improve the performance qualities for the blades of some stock removal makers. You can try them if you wish, I suggest you test your experimental blades and compare them with your standard methods and see for yourself how well they work for you.

              Fifteen steps to heat treating the High Endurance Performance Blade
                                           
                                       Post Forging Quenches

Post Forging Steps 1 to 3: Immediately after forging the blade I heat the blade as forged to just above critical temperature check with a magnet and then quench the entire blade (except the tang) from edge to spine with the edge down in room temperature Texaco Type A quenching fluid. I hold the blade in the oil for at least 35 seconds, then place it back in the forge, and repeat this process for a total of three times. The temperature of the oil will rise with subsequent quenches; this does not seem to make any significant difference in the performance qualities of the blade.  Note (Since we started this using this step we have never had a blade warp in subsequent heat treat.)

                                         Normalizing Cycles         

Post Forging Steps 4 to 6: the blade does not need to cool beyond its temperature after the last 35 second quench. I place it back in the forge and heat it to a dull orange temp, brush it off with a wire brush to remove scale from the first three oil quenches then heat it to a little above nonmagnetic (critical Temp) check with a magnet, then hold it in a dark area and watch as the blade cools down through critical temp. The blade will be Bright colored, slowly turn dark, then turn light again and at this point be magnetic. I check it on a magnet, and then repeat the process for a second time. Next I again heat it slightly above critical temp and place in it in 70 degree f. temperature still air and allow it to cool down to room temperature.  This is known as a full normalizing cycle, (I never hurry this cycle by waving the blade in the air or placing it in a draft). Once it reaches room temperature I place it in the freezer of my refrigerator for at least 24 hours.

                                      Low Temperature annealing

Post Forging Steps 7 to 9: I then place the blade in my Paragon Oven at room temperature; set the Paragon to heat the blade to 988 degrees f. in one hour, hold at 988 f. for two hours then shut off and let it cool to room temperature slowly with the oven door closed. I then place it again in my freezer overnight and repeat the process two more times for a total of three cycles. Low temperature annealing will preserve the grain structure you have developed to this point. After this tempering cycle the blade is close to dead soft, we can easily cut the steel with a cheap hack saw blade.

                                     Preparing the blade for Hardening

I then grind the blade toward its final shape, defining the area that will be the ricasso and blade edge, I leave the future edge a little thicker than a quarter as I believe the best edge this bade can support lies a little under the surface of the blade after hardening. I am very careful to grind the blade to a smooth surface, removing any dents or scratches over a 220 grit before hardening. Photo 5206

Quench tank and adjustable table Photo 5250
Steps 10 to 12: We preheat our Texaco type A oil to 165 f. before quenching the blade.
I heat the lower 1/2 to 1/3rd of the blade using a 2 X flame on my oxygen - acetylene torch using a Victor 3-W tip on my average sized blades. I heat the blade from the center of the ricasso down the center line of the blade to a little behind the tip and am very careful to not overheat the future edge or the tip. Once the lower third of blade is a little over critical it is ready to quench, the spine remains slightly magnetic. I learned this method from Bill Moran and was in awe of his ability the first time I watched him. This method takes practice, but I feel that once you have mastered you it you will have developed a very special skill. We have found it is a very valuable attribute and proves to be a tremendous benefit to the kind of blade we want to make. You can learn to paint the desired color into the blade with your torch, just like an artist paints his colors into his art.
(photo 5208)

After we have heated the oil we check the oil level by rocking the cool blade on the table and adjust the oil level. (photo) 5222 We set the table in the oil to only submerge to about ? the depth of the blade. Deeper blades are not quenched as far into the oil, but at least to one third. Blade ready to harden (photo \) 5214 I put the blade tip first into the oil on my adjustable table in the oil and then I rock the blade rapidly to harden the tip as well as full edge and part of the ricasso. Once the blade has cooled to a dark heat, I submerge the blade fully into the oil and let it cool to room temperature.  The blade then goes in the freezer of my house hold refrigerator until the next day. This process is repeated for a total of three times.

 (Note I never harden the tang, this is another lesson I learned from Bill Moran and it is my firm belief that one of the major factors of blade failure is encouraged by tangs that have been hardened. The memory of every thermal event is forever recorded in the steel)

                                        Tempering the blade
(Photo 5253)
Steps 13 to 15. Last three steps in our heat treat are as follows. I place the blade in my Paragon at room temperature, set the Paragon to heat to 388 degrees in one hour, hold for 2 hours, then allow the blade to cool down in the closed Paragon until it reaches room temperature, then again place it in my house hold refrigerator freezer overnight and repeat for three times. Again I never cool the blade rapidly by opening the oven door or quenching.

This is a summary of the system we have found works best with the steels we use, high quality 5160 and 52100, we have tested hundreds of blades to complete destruction in the past 35 years and find any shortcuts may have a very significant influence  in what I call the balanced performance of the High Endurance Performance  Knife.  Using these methods we have achieved an aggregate ASTM grain size of 15 and smaller in our 52100 steel.  When we started our work with 52100 an ASTM Grain Size of 10 was he theoretical limit, we have exceeded that by a long ways. The Blades cut exceptionally well, are very strong, tough and are easy to sharpen.   

I ask that you do not simply take our word for the process, but that you try various aspects you may choose using your steel in your shop with your equipment, test your experimental blades yourself and you will know.

Whenever a maker tells you how to heat treat your blades, ask them a simple question, ?How to you test the performance qualities of your blades?? his answer will tell you if his way is how you want to make your blades.

While researching for another article I came across a statement that claimed James Black who some feel made a knife for James Bowie used a 12 step heat treating process and he never revealed his secret. I am a believer that a good heat treat is essential in order to get the best the steel has to offer.  My experience leads me to believe that whoever made that statement may have been very knowledgeable.

I want to thank those who have helped us in our search for the High Endurance Performance Blade and a very special to the man of science who dared to work with us for over 25 years, Rex Walter, his knowledge and dedication to our work continues to be our greatest asset. Kevin Gray, another metallurgist has been studying these methods and will be writing for publication in the near future.


Note: Some believe that 52100 steel is difficult to work with and heat treat.  All the steps we use are not necessary to develop a fine blade. 52100 is what I call an honest steel, the more you put into the development of the blade, greater the performance.                           


Thanks for sharing time with me, any questions or comments you may have will be welcome.


   

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billy brewton
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« Reply #1 on: June 12, 2013, 11:44:40 AM »

Great tutorial Ed also loved the spread in blade just got the latest today haven't had a chance to paruse it yet. I have one tiny question if you don't mind. When it comes to the tempering cycles does the orientation of the blades matter?? As in laying flat down or edge up or down?? Just one of my wonderings. Thank you for all you do an teach. Have a good one friend
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Ed Fowler
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« Reply #2 on: June 12, 2013, 11:55:57 AM »

I have a little rack  for the blades and always place my blades with the spine down and edge up. I like to keep the tip away from the immediate vicinity of the heating coils if possible, but when you ramp up slowly it probably makes very little difference.

At one time I was fighting blade warp and that is when I quit laying them on their sides, I did notice a difference in some blades from side to side when I laid them flat, the difference was gone once I started using the rack.

Thank you, that was a good question! Glad you liked the write up.
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Daniel Rohde (D-Vision)
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« Reply #3 on: June 12, 2013, 01:28:29 PM »

Nice Ed! I really like having it all written in one place and beautifully executed!
a few questions( Wink)
do you still use the blades smith anneal that you wrote about in your first book?
in your video(number two) you sometimes when your forging just let the steel cool down with out hammering it why?and how often do you do this?
in your first book you said that when forge by randomly quenching the steel makes it tougher is that what the post forging quenches are?
in the normalizes does it matter if you let it cool little past the stage where it turns bright again?why not just let it cool for 3 minutes?
Thanks for sharing and well done!!!
DV...
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mreich
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« Reply #4 on: June 12, 2013, 06:45:48 PM »

Thank you for the excellent run down Ed. it's great to be reminded of your complete process.

Thank you for the perfect honesty of your methods. That is one of the things that I respect you so much for. You don't have any secrets. You share everything completely and honestly, and hold nothing back. That is pretty rare.

Another thing is your open minded approach. I love to hear your "try it and see" humility. I don't ever remember any admonishing. I know you are always open minded, even though you've tried something that didn't work, you always say "go ahead and try it, and please let us know how it worked for you".   

I feel so blessed to be to be an apprentice on your crew, and I love this forum. You are a true friend, gentleman and teacher. Everything seems to work out just as you thought it would, and you only compliment the guy who tried it, even when it turns out exactly as you'd figured. You know we learn more from our failures than our successes.

Well, that came out kinda brown nosing, but it's just the truth to me.
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Dennis Mashburn
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« Reply #5 on: June 13, 2013, 09:47:09 AM »

Very good post and information.  I also really like your humble try it and see attitude on this.  I don't see how anyone could make arguments about this post.  I passed the link to a local knifemaker friend of mine so now maybe he won't think I am so crazy as I can't explain all that nearly as well as you.

I have one question if it won't derail the thread.  What ill effect does it have to heat 1/2 to 1/3 of the blade, but dunk the whole blade under instead of just a 1/3 or so with the depth plate.  I had a quench oil fire one day and am a little gun shy about not dunking all of the blade.  I do now have all needed items in case I have a quench oil fire again though.  (good lid for tank and fire extigusher if needed)

Thanks again for sharing you hard earned knowlege with us.
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« Reply #6 on: June 14, 2013, 07:49:52 AM »

I think quenching the whole blade makes it harder, thus stronger, but you won't get many 180* flexes.

I'm just saying, because that's what I do, and I don't get many 180* flexes.

To me, that's not a big deal. I never recommend flexing more than 45*, simply because if you haven't done the job at 45*, you're only testing the flexibility of the blade. You can't get any more prying power going beyond 45*.

We should ask Kevin if that's accurate. I think you could "prove" it mathematically, but I took physics a very long time ago.

The other reason I see for not flexing a blade 90*, is that if you do, I believe the blade should be replaced. I wouldn't count on it after that sort of treatment.

If you tell someone that your blades can do multiple flexes of 180*, he'll likely try to prove it.

If you're just testing a blade, then that's a good reason to see how tough it is.

If you are Using the blade, and flex it to 90*, you should expect that it will ruin the integrity of the blade, even if it doesn't break.

JMHO. What do the rest of you think? Would you expect the blade to sustain damage on one 90* flex?
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« Reply #7 on: June 14, 2013, 10:30:36 AM »

I think quenching the whole blade makes it harder, thus stronger, but you won't get many 180* flexes.

I'm just saying, because that's what I do, and I don't get many 180* flexes.

To me, that's not a big deal. I never recommend flexing more than 45*, simply because if you haven't done the job at 45*, you're only testing the flexibility of the blade. You can't get any more prying power going beyond 45*.

We should ask Kevin if that's accurate. I think you could "prove" it mathematically, but I took physics a very long time ago.

The other reason I see for not flexing a blade 90*, is that if you do, I believe the blade should be replaced. I wouldn't count on it after that sort of treatment.

If you tell someone that your blades can do multiple flexes of 180*, he'll likely try to prove it.

If you're just testing a blade, then that's a good reason to see how tough it is.

If you are Using the blade, and flex it to 90*, you should expect that it will ruin the integrity of the blade, even if it doesn't break.

JMHO. What do the rest of you think? Would you expect the blade to sustain damage on one 90* flex?

I agree 90 degrees is excessive, dont get me wrong if your knives can do this during destruction test, awesome more power to you. But under normal or even hard use 90 degrees is excessive.  I want about a 45 degree angle and spring back to straight numerous times
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Daniel Rohde (D-Vision)
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« Reply #8 on: June 14, 2013, 07:25:06 PM »

so hears my questions(you new it was coming right?) and well done Ed!!
Do you still use the blades smith anneal that you wrote about in your first book?
In your video(number two) you sometimes when your forging just let the steel cool down with out hammering it why?and how often do you do this?
In your first book you said that when forge by randomly quenching the steel makes it tougher is that what the post forging quenches are?
In the normalizes does it matter if you let it cool little past the stage where it turns bright again?why not just let it cool for 3 minutes?
Thanks for sharing and well done!!!
DV...
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« Reply #9 on: June 16, 2013, 05:12:09 PM »

my question was up above(I need thoughts!!)
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Ed Fowler
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« Reply #10 on: June 19, 2013, 10:51:54 AM »

We let it complete the cycle from bright to dark and back to bright and non magnetic to insure a full cycle, this seems to be essential. The third normalizing cycle is from non magnetic to room temp in still air, never hurry this cycles by waving the blade in the air or in a draft.

Many times I give the steel I am working on a complete normalizing cycle. In one experiment I gave a blade over 50 normalizing cycles, it turned out beautiful as seen by the etch and performed beyond my personal endurance in cut. Any full normalizing cycle during the forging of a blade will not harm the blade as far as we can know at this time. Laying the blade on an anvil or floor to cool provides a thermal shock to the steel and should be avoided at all costs as thermal shocks show up as faults in grain flow during testing. Many times you can see them in the etched blade.
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« Reply #11 on: October 29, 2013, 05:34:57 AM »

Hi Ed! Hi everybody!

I wonder if it's ok with you to translate your arcticle in Greek and post it (along with the link to your original arcticle ofcource) to the Knives and Blades Greek Forum. A knifemakers and bladesmiths community here in Greece. You have many big supporters here you Know! Thanks for the knowledge you share anyway!
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« Reply #12 on: October 29, 2013, 08:51:11 AM »

You are welcome to translate anything I write and share it with others. The opportunity to share what we have learned and our opinions is the reason I write.

I am honored by what you write, thank you.
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« Reply #13 on: October 29, 2013, 03:05:45 PM »

Wow! That's very cool!

I wouldn't have guessed you were world famous, Ed.

I like you slightly more now.







 Grin
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jared williams
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« Reply #14 on: April 17, 2014, 10:27:03 AM »

I wanted to renew this thread for anyone wondering how we heat treat an HEPK knife. There is a lot of solid info here.
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