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View Full Version : Why is D2 so toothy?



Eamon Burke
03-21-2011, 11:39 PM
Why does D2 take such a toothy edge? It's often the go-to for people cutting rope and whatnot, and I'd like to know the specifics of why.

Does it perform like this regardless of how the steel is handled? And does the "toothiness" of it buff out?

Eamon Burke
03-21-2011, 11:40 PM
This is relevant to kitchens because I'm considering making a kitchen knife in D2.

Delbert Ealy
03-22-2011, 12:38 AM
D2 is considered toothy because of the chromium carbides it contains. There are several elements added to steel that have an affinity for carbon, iron is one, but it is not a strong carbide former and will form carbides, but if there are other stronger carbide formers, they will take the carbon and not leave much for the iron to form carbides. Chromium, tungsten, molybdenum, and vanadium are all strong carbide formers. Of these chromium has several characteristics that the others do not have. When present in high enough concentrations, along with some carbon, it will produce stainless steel, and when enough chromium and carbon are present the chromium carbides will clump together. The chromium carbides themselves have a great affinity for each other, they like to get together and throw a party :)
This is where the carbide clusters can cause a problem, since many of you are familiar with the micron scale, I will use that as an example; I have seen micrographs of chromium carbides in D2 that are 50 microns long and 25 microns thick. If you are using a .25 micron spray for the final edge or even a 1 micron spray, think of the huge difference in the fine edge you are trying to produce and the size of these carbides.
The toothyness of D2 is caused by these carbides being torn out of the edge during the sharpening process. They are very hard, if I remember correctly they are about 70 Hrc, and they will tear out of the surrounding matrix rather than being worn down.
There is a way to control these characteristics in D2 and that is to use CPM D2, this version of D2 is made by taking the finished alloy and while it is molten; spraying it out of a fine nozzel in to a cool vaccum, and that makes a very fine powder. That powder is then compressed and heated until it forms a single solid piece again. The temps here are pretty high, but not molten, and it gives a much finer distribution of carbides, so they can't get together and party.
In other alloys it can be controlled by lowering the carbon, such as in AEB-L , or by adding a carbide former that has a stronger affinity for carbon than chromium does.

Eamon Burke
03-22-2011, 12:23 PM
So will the carbides last on the edge a while? Say, longer than a vg-10 or cpm154 that are sharpened to a really toothy edge?

Just like on cheap steel I put toothy edges on them(cause they cut better), I also put toothy edges on my VG-10 Gyuto when I am cutting up something crusty, like grilled chicken, or tough, like beef round. But the teeth break off fairly quickly. Does the naturally occurring large carbide structure improve edge retention on intentionally toothy edges like that?

festally
03-22-2011, 01:35 PM
I used to cut a lot of rope and swiched from VG-10 to a D2 steel edc. The D2 won’t take an edge as fine as VG-10 (the edge sortof crumbles) but with a less acute, more toothy edge, does have a longer edge retention. It also take longer to resharpen.

RobinW
03-22-2011, 07:49 PM
Honestly, try borrowing a SKD11 or D2 kitchen knife before you start down this road.
I have the Yoshikane 240 and it resides mostly in it's box because, quite frankly, apart from having good edge retention i really do not care for the steel. Especially sharpening.

I would take pretty much any decent carbon or VG10, AEB-L etc any day before the SKD11

just my 2c

JBroida
03-22-2011, 07:58 PM
just my 2 cents... i have 4 skd 11 knives from 4 different makers (and a couple of skd 12 knives too), and they all feel noticeably different... some i dont care for that much and some i love

Eamon Burke
03-22-2011, 08:29 PM
Hey, I'd love to borrow a knife in D2 or SKD11, but I don't know anyone who has any sharp knives, let alone one that "oddball". Sounds strange, but it's true. There's 8 million people here in DFW and I don't know any of them personally that know jack crap about knives. I'm sure they are here, but I don't know them!

deanb
03-23-2011, 02:45 AM
Wow Delbert. Now THAT is what I call an explanation! Nice post.

RRLOVER
03-23-2011, 08:15 AM
I have a SKD11&12 blades and i love both of them.I really don't get into toothy-nontoothy edges.Also i can't say i had any trouble sharpening my yoshikane,the only issue is it's so thick behind the edge and can be fixed with some thinning.

l r harner
03-23-2011, 08:36 AM
nice del and thats why i dont like the cpm D2 as its taking away the "best" (is it really that great) thing that D2 does
the CPM make the choice to use cpm154 much easer
D2
C Co Cr Mn Mo Ni P Si S V
1.55 - 11.5 0.4 0.9 - - 0.3 0.03 0.8
cpm154
1.05% 14.00% .50% 4.00% .40%

if you are in need of SS get SS and if you need a crazy tuff tool steel get it (i hate middle of the road steel less you are making miffle of the road knives:) )

tk59
03-25-2011, 02:15 PM
I've been playing with a Heiji. I'm not sure if it's SKD11 or 12 but based on specs, I'd guess it's SKD11. Anyway, I shaved with it, made a few meals with a few hundred boardstrikes and it was still splitting hair. I'm going to strop it and see how it shaves probably tonight. This is an exceedingly fine edge. My understanding is the large carbides will tend to stick around if your edge is fairly thick/coarse.

RRLOVER
03-25-2011, 09:25 PM
[QUOTE=tk59;5744]I've been playing with a Heiji. I'm not sure if it's SKD11 or 12 but based on specs, I'd guess it's SKD11. Anyway, I shaved with it, made a few meals with a few hundred boardstrikes and it was still splitting hair. I'm going to strop it and see how it shaves probably tonight. This is an exceedingly fine edge. My understanding is the large carbides will tend to stick around if your edge is fairly thick/coarse.[/QUOT


Heiji is a SKD12.You are dead-on with this blade having a fine edge.I am not feeling the big carbine shpeel on the edge that is supposed to be a trait of this steel.

JBroida
03-26-2011, 01:07 AM
[QUOTE=tk59;5744]I've been playing with a Heiji. I'm not sure if it's SKD11 or 12 but based on specs, I'd guess it's SKD11. Anyway, I shaved with it, made a few meals with a few hundred boardstrikes and it was still splitting hair. I'm going to strop it and see how it shaves probably tonight. This is an exceedingly fine edge. My understanding is the large carbides will tend to stick around if your edge is fairly thick/coarse.[/QUOT


Heiji is a SKD12.You are dead-on with this blade having a fine edge.I am not feeling the big carbine shpeel on the edge that is supposed to be a trait of this steel.

in all honesty, i'm not 100% sure about this... i really want to ask him, but now is not the best time. As soon as i can, i will. Sorry.

spinblue
03-27-2011, 08:43 AM
Wow Delbert. Now THAT is what I call an explanation! Nice post.

+11111

Gator
03-27-2011, 04:36 PM
I've been playing with a Heiji. I'm not sure if it's SKD11 or 12 but based on specs, I'd guess it's SKD11.
JIS SKD12 (http://zknives.com/knives/steels/skd12.shtml) is AISI A2 tool steel (http://zknives.com/knives/steels/skd12.shtml). About 4%-5% Cr in it, SKD11/D2 have over 11% Cr.

P.S. Does Heiji publish the specs?

festally
03-28-2011, 08:54 AM
...Does it perform like this regardless of how the steel is handled? And does the "toothiness" of it buff out?

I tried a smoother edge on a d2 and cut up a bunch of cardboard without issue. As far a I can tell, d2 will take a polished edge -- as long the edge is on the mighty side. However, it doesn't like acute angles, and takes quite awhile to polish & sharpen. I didnít have the patience to refine to shaving / mirror level, but it seems doable.

JBroida
03-28-2011, 12:54 PM
P.S. Does Heiji publish the specs?

No that i know of... once he gets back on his feet again, i'm intending to talk with him about it

Gator
03-28-2011, 01:35 PM
I C. TK59 said "based on specs" so I thought may be he did publish specs for something. Anyway, you know I am always happy to grab a new steel composition ;) Closing on 3K alloy names fast.