Stainless san mai, core steel testing.......

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WillC

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Im very happy with 01 as an uber fine grained staple core steel. It takes a fantastic edge and gives reasonable edge retention whilst being very nice to sharpen. Exactly as you would want from a good carbon steel.

I would like to flirt with some other options, not super wear resistant, but something a little less fine grained, toothier quality and greater wear resistance, whilst not being overly hard to sharpen. I have read lots of bad and good things about D2, many contradictory to each other. But from the offset and having read some excellent papers with heat treat tests on the steels grain structure and ultimate toughness I would say there is a lot in a heat treatment. So with my own testing Im aiming the the finest grain possible whilst being as hard as possible without being brittle.

I tried a few different austenitizing temperatures which were quite close, these produced the finest grain to the naked eye.



I went with the later lower temperature for the rest of the samples. To me this grain is surprisingly small and even to what I have heard of D2. It is not as fine as 01 but finer than something like blue paper steel, which has a slightly courser structure to the naked eye.
The pieces were 65hrc after a plate quench followed by cryo. They were also very very hard to break, Already some tough stuff over this thickness.

3 samples I then used to bracket my temper temperature. Each had 3 temper cycles at one hour. This is important to this steel it has been proven. I also gave them all a second cryo for good measure.

Each piece I then ground and sharpened, a pretty crude grind but with a fairly low final angle about 15 degrees per side. With each I cut notches in some mild steel until they would no longer perform the task or until dulled significantly.



The one I have settled on as my ideal temper temperature managed this complete row without chipping in the slightest, just a little dulling which came out easily on a chosera 1000 grit stone.


This was the two with a lower temper temperature.



This is the piece with a slightly higher temper temperature and the HT I will settle on for further testing. Final hardness 61/62hrc



Next to make a knife out of it to get an idea how I like it on a much thinner edge and get a feel for edge retention vs sharpenability.

Im hoping to make same nice hard wearing slicey 210 line knives in this steel with stainless cladding. I am also waiting for some cpm 3v to arrive, which I believe I will like for different reasons.:cool2:

Ill update as I manage to get a san mai knife together with out melting the stuff:D
 
Great testing photos. Thanks for sharing. I have worked with a few diffrent D2 steels and the D2 thats made of powder steel.. Is some amazing stuff! If ya really want to make it more wear resistant. Cryo it!! Takes it from tough to CRAZY tough!!
 
Yep, these pieces were cryo'd twice. I did not try a piece without cryo, except for a hardness test prior to cryo and it brought it up 1-2hrc. Looking forward to trying it in context of a chef knife.:D Cheers Folks.
 
I missed that in your post. Sorry. Yep I have yet to try it as a kitchen knife. Mainly using it for camp knives, and or smaller carving knives. One you get the stuff sharp it stays that way a very very long time!!

Have fun and thanks again for sharing
 
Good to hear mate, thanks. Looking forward to trying the 3V too. I can only get it in 12mm so a fair bit of forging out if it works out in san mai. :pirate1:
 
Hey Will,

It is always interesting to follow craftsmen trying out/testing new things which is a testament of their mastery of the basic skills required and is free to be creative and find new things, methods/ techniques to reach a new height of which is never ending.

Been following your tweaks as to handles, profiles, geometry, materials heat treats etc as it is informative and broadens my knowledge as to a well made knife in terms of form and function and what you guys go thru to make one. WIPS is always a joy to follow. Videoes.. can't ask for more.

Comparing your first few knives and the the recent few knives to your latest.... it has become a never ending quest for me too and I can't keep up with you.

Of all, my favourites are still the "USA Passaround" ( http://www.kitchenknifeforums.com/showthread.php/2796-300mm-Damascus-Suji-U-S-Pass-around) and the Twin Petty (( 68,000 layersdidn't manage to snag the Feather damascus) as it constantly reminds me of your journey... and I did't make a mistake is spotting a budding craftsman then.

Have fun.. always

D
 
Thanks David, your, confidence in my work, support and advise has and is very helpful along the way:)
 
D2 core san mai...


Stress relieving before doing a full anneal on two stainless damascus clad D2 core blades.

 
Got these two ht'd, cryo'd and first temper cycle, two more full hour temper cycles to go. With forging more complex steels, makes the pre-heat treatment and heat treatment processes take much longer. The anneal cycles were 3 hours and cool in furnace, so basically 2 days of annealing before HT can begin.

I also did a billet in plain stainless clad D2 as it was the perfect test for my new furnace, very narrow temperature band for success, it was a success:) A bar of 12mm x 50 x 1000 cpm 3V is on its way to me from germany.
 
In simple terms;)
The main reason to heat cycle and anneal after forging is that the grain structure will be very large and crystalline after heating it up to welding temperature, then forging. Also during forging it may have become somewhat hardened, these are air cooling steels in this instance, so it is hard to avoid. The heat cycling reduces the grain size and removes stresses, Annealing ensures that it is in its fully un-hardened condition.
Now you have a piece ready to heat up to critical temperature and quench to harden, in oil or air. In this case I used my hydraulic press to plate quench the blades, the plates under pressure take the heat quickly from the blade and this also helps keep it straight as a bonus.

After this you have cryo treatment - Short answer this helps you achieve greater hardness, especially in stainless and not at the expense of toughness.... and tempering, Tempering takes some hardness from the steel to ensure a good balance of toughness. In this case triple tempering is also shown to help reduce carbide size....therefore giving greater toughness at a given hardness......

Looking forward to testing these blades now........... Will have to wait till next week:)
 
You should always forgive the steel, as its much harder than you.:D
 
In simple terms;)
The main reason to heat cycle and anneal after forging is that the grain structure will be very large and crystalline after heating it up to welding temperature, then forging. Also during forging it may have become somewhat hardened, these are air cooling steels in this instance, so it is hard to avoid. The heat cycling reduces the grain size and removes stresses, Annealing ensures that it is in its fully un-hardened condition.
Now you have a piece ready to heat up to critical temperature and quench to harden, in oil or air. In this case I used my hydraulic press to plate quench the blades, the plates under pressure take the heat quickly from the blade and this also helps keep it straight as a bonus.

After this you have cryo treatment - Short answer this helps you achieve greater hardness, especially in stainless and not at the expense of toughness.... and tempering, Tempering takes some hardness from the steel to ensure a good balance of toughness. In this case triple tempering is also shown to help reduce carbide size....therefore giving greater toughness at a given hardness......

Looking forward to testing these blades now........... Will have to wait till next week:)

Thanks, I needed that!
 
Worcester? Only about half an hour from my workshop.
Here is a good paper on Metallurgy for bladesmiths.
http://www.feine-klingen.de/PDFs/verhoeven.pdf
I often refer to this as I could never remember it all, well maybe one day. I have not really that type of brain, I just like to know enough to get a feel for what Im doing and take it from there with some real world tests. Where as the science would explain what is happening during the processes and transformations, in general I only wish to know what will achieve the best results, though I can see how a greater understanding of the chemistry can help so i do try to understand.
There is a great chapter on AEB-L in the above.
 
This is the paper I read on getting the best toughness and as fine and even distribution of carbides in D2 as possible.
https://tspace.library.utoronto.ca/bitstream/1807/13366/1/MQ45596.pdf

I will be interested in the results in terms of a kitchen knife because that is my field of comparison with everything else in terms of how it sharpens, how sharp it gets, how the edge feels to the touch and in cutting and edge retention. Im sure it will be tough at this HT. D2 has been reported as many things, hard to sharpen, very toothy, tough, chippy. There is allot in a heat treatment for sure.
I hope with this heat treatment, I will have an optimum level of the toothy character of the steel, but tough with no microchipping, easy to sharpen, relatively fine edge. Its never going to be as fine and get as sharp as a super fine carbide steel like AEB-L or 14c28n, but I'm going for a different effect here, some teeth and an increase in wear resistance over fine carbides. For a real hard wearing slicer, that retains its teeth long after loosing the shine from the strop.
Will be very interesting to compare to cpm 3v, which should be a very tough steel also with good wear resistance, but with finer carbides, given correct treatment. So they should feel and cut slightly different. There are a few others I would like to try. None are particularly in the super wear resistant area. I might play with this later, but at the moment Im interested mostly in steels which are at least relatively easy to sharpen and work with.
Something like cpm 10v is an interesting proposition but poses issues in all areas as far as forging, grinding and maintaining a knife made from it.
 
Those were some prett amazing posts, Will. Now, I'll follow it up with this. Ready for it... :

Pierre made a slicer from D2 (I believe), and if I'm not mistaken, the owner was really impressed. I think you're onto something. And, I like ice cream.
 
Yep lets see. I expect the D2 and 3v will be chalk and cheese. Its fun to play in these extremes to learn. Yeah the main concern is the D2 will not be terribly stable on a very thin edge due to larger carbides. Although the grain looks fine would need a micrograph to show up the large undissolved carbides. So I'm hoping I have pulled off something with my moderate HT in not going for extreme hardness and multiple temper cycles, cryo, all this should help reduce the larger carbides and give a more even distribution, but we will see.
I have just found an excellent source for samples of many Bohler and latrobe steels, so more testing to come over future months.:D Obviously the pm steels get expensive so will be done gradually.
 
How much of a difference would CPM D2 make Will? I imagine it would have all the neat properties of D2 but with finer carbides?
 
I really could not say without trying them side by side. If I find a use for D2, I may give it a try.
I tried my sample piece with a very very thin edge, taken to zero in fact at a very shallow angle to see what happened. On a brass rod I got neat semi circular chips about 0.5mm diameter with not too much force. So I took the sample up in temper temperature by about 20 degrees, this stopped the chipping. But with this thin an edge, It was not exactly stable either there were instead little folds in the edge pushed to destruction, but these very limited. But on this thin an edge my 01 would show allot of flex before distorting slightly or ultimately chipping. Putting a secondary bevel on the sample totally changed it, I could now not mark the edge what so ever with a brass rod and again take notches out of my steel bench with no damage at all. So so far it seems the shape of the edge makes a difference, a little bit thicker at the edge gets the most out of this steel and it becomes very very tough in this format. Still thin at the edge but I would not choose this for a line knife I don't think. Just off the strength of this sample I think it would be fantastic for any thicker boning or filleting knife, or even a big carving knife, would be no worries being hammered or sliced through and against bone so long as there is a distinct secondary bevel, and it can still be thin, it just needs to be there and more so than the tiniest of micro bevels as with my carbon/14c28n knives. I will keep this in mind with my test blades. Im now thinking Honesuki:knight:
The 3v has arrived also, its a huge chunk, nearly 14mm thick, by 50mm by 1000mm, (smallest they had)! I'll have to grind it down a little to san mai it with some 12mm for plain stainless clad.
 
@Tim

One steel at a time. This experiment is about taming something with notorious teeth and putting them to best use and with the best possible heat treatment. I do like a challenge. I have pretty much decided D2 will not be suitable for an all-round chef knife, it looks like it can be made to be more suitable with the right HT, but it seems to really excel with a slightly thicker edge, where as others would excel on a thin edge, so I think it would be wasted on anything else. I will still take my samples blades to the thinest possible edge and test them and can thicken the secondary bevel till I reach that magic point. I think they will make some incredible Honesuki or Big sunday joint carver.

A2 looks like a contender for a more wear resistant line knife, I think that would be a vs 3V experiment. But 3V will come first, as a girt big chunk of it just turned up from germany.:D
 
Ah I think your confusing meat on the bone with camberwell carrots.:lol2:
 
Thats the baby, great film:biggrin:
 
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