Two Diagrams from Crucible Data Sheets

[Cliff Stamp]

M2 seems to handle 10 degrees just fine though.

Mel Sorg made a lot of blades out of D2, full cryo, his blades could shave hair above the skin, push cut right into newsprint, the edge angles were really low. His father used to work as a paper cutter and had them almost right to the primary grind. D2 is one of the most coarse grained steels, but even it doesn't have a problem with high finishes. The Sorg blade I ran at the above extreme profile cut over 2000 pieces of 3/8" hemp without resharpening, and was at ~20 lbs of force at the end of the cutting. Carbide tear outs were no problem there obviously as the edge retention was extremely high. M2 is however pretty much a directly better cutting steel, gets harder, is tougher, and has better wear resistance and hot hardness.

-Cliff

 

[WYK]

WYK-
For your kind of use, it doesn't sound like you'd see the difference or need the extra toughness offered by 3V. But when I sharpen my bowie, I use a 120 grit alumina stone, and remove metal so quick the blade actually gets hot. That's how much damage it gets. It would take a month to sharpen it with a strop. According to the chart, 3V or S7 may well reduce this damage significantly, meaning my knife will last longer. I've already removed a quarter inch of steel from the last third of its edge.

3V is likely the best steel for any sort of knife that will take a beating and needs to hold a good edge.

However, I only use my Bowies for one thing - hunting and self defense. I don't camp with them, per se. I mean I use other tools for wood, making spikes etc. A custom 52100 13" bowie is made to kill animals and people - not sticks For sticks and splitting I use a 5160 axe with a full flat grind that I ground out of a huge billet a forging bud made a short while ago and did a differential heat treat on(hard, soft, hard). I'm a big guy, so carrying 6lbs of tools into the woods is an easy chore, and I get tired of the woods after afew days(basically cause I live in them to start with) so I rarely camp so long I consider leaving tools behind to stuff more food or provisions into the backpack. So, when I am sharpening my Bowies it is usually after it's killed something or done some cutting my 5.5" hunting knife(also of 52100) couldn't do on a hock or some such. It's just good fun cleaving the leg off of an animal in one stroke with a 13" Bowie for the BBQ that evening.

I can go an entire season and not have to sharpen it, though. And it still gets plenty sharp by stropping. I've not had to grind it out, yet, either. My brother has a 10.5" hunting Bowie I ground for him out of 154CM and had hardened to 59 RC. It has a 1/4" thick spine with a full flat grind on it's 2" wide blade. That thing sees less work than my 52100 Bowie does, and it is much more of a chore to sharpen. So I'm just comparing my experiences with carbon and stainless here.

I do not have a 3V blade, but I do want to grind one sometime soon and send it to Bos. I've been getting some quotes on 3V stock, and it's expensive!

WYK

 

[Blop]

Carbides are really small, ~1 micron, you don't need to worry about them even in steels like D2.

There are many pictures about D2 showing it has carbides far larger. Pictures of S60V show how much carbides are included and so on.

Wear resistance as prooved normaly is a matter of carbide amount and size. Fine edges need well destributed and small carbides.

Look here to see many pic:

Pictures

Any tuogh steel shows a very fine and homogeneuos structure unlike CPM or D2.

 

[the possum]

WYK-
sounds like we aughta swap stories sometime.

However, I only use my Bowies for one thing - hunting and self defense.... So, when I am sharpening my Bowies it is usually after it's killed something or done some cutting my 5.5" hunting knife(also of 52100) couldn't do on a hock or some such. It's just good fun cleaving the leg off of an animal in one stroke with a 13" Bowie for the BBQ that evening.

So what do you get to use the blade on down there? You hunt hogs with it? Though I do use my blade for general brushwork, it's primary role is also hunting. Coons & possums are about the biggest critters I can hunt with it up here though. (stalked within 5 yards of a little buck the other year, but spooked him) I can only assume the differences we're getting in edge durability are due to vast differences in our hunting style.
I know what ya mean about the leg thing, though. I've used my bowie the past several seasons to help butcher our deer, and it easily snicks their heads off without even slowing down. Bone doesn't seem to affect my edge too badly; I may have to realign it with a ceramic rod or something, but it usually doesn't need heavy sharpening from that.

Do you see chips or impaction?

Both, actually. I've even seen tearing, which surprised me. As mentioned, this was an inconsistent piece of steel, so I don't know if I can form generalities based on my blade. If I had to pick one, though, I'd say I see more impaction than chipping.

 

[Satrang]

Carbide size of powdered steels is consistently 2-4 microns in size.
Conventionally melted steels like D2 have a broader range of carbide size. The range is dependent on the hot reduction of the steel. 2-250 micron carbides are common in D2 depending on the reduction. Sheet materials will max out around 50 microns since they are reduced about as much as you can get. The problem with the conventionally melted steels is the banding and orientation of the carbides from the rolling operations.

 

[Cliff Stamp]

There are many pictures about D2 showing it has carbides far larger.

Than one micron yes, ~micron means approximately, as it the carbides are measured in microns. 1-10 microns covers most steels, D2 gets larger still, as it is one of the highest aggregates, but still as noted isn't large enough to prevent very fine edges and high wear resistance.

Now in an extreme you will run into trouble, but you are looking at hollow grinds which are say ~0.015" thick at 1/4" back from the edge and the edge ground at ~5 degrees per side. For that type of profile you need fine grain sizes, but few knives are ground like that.

Of course improving the grain size though careful heat treating, minimal soaks, cryo, etc. is always a good thing as you get better machinability, improved wear resistance, higher toughness, etc. .

I've even seen tearing...

Yeah, there are obviously problems with that steel, you are getting extreme ductile failure and brittle in the same piece.

-Cliff

 

[the possum]

Yeah, there are obviously problems with that steel, you are getting extreme ductile failure and brittle in the same piece.
-Cliff

I dunno- it's kinda wierd.
Normally I think tearing would be a sign of soft ductile steel. But when I resharpened that portion of the edge, it still seemed like it was in the mid 50's Rc. Others who have written about the performance of bainite make vague allusions that it takes damage differently than we're used to with martensitic structures. Could this just be one of bainite's quirks?

I've only seen it happen that one time, even though that same portion of the edge has taken further damage since then. It was a nick about 2mm long, and ~.7mm deep.

 

[Cliff Stamp]

Could this just be one of bainite's quirks?

It is supposed to be far tougher than martensite at similar hardness, so it isn't unlikely that it would rip instead of crack, however unless you are working with a really thin cross section it should be near impossible to do, at 55+ hrc because the strength should be really high, unless you smack into a heavy bolt or similar with a lot of force. I would also expect to see a lot of denting or deformation in general before it ripped.

-Cliff

 

[Satrang]

I have seen edges where the carbide bands lie directly on the cutting edge. It is a rarity but can happen. This weakened edge will fail and have a tearing look to it since what happens is the entire edge chips off leaving a rough appearance. You can sharpen past the area if enough meat is on the edge to work with.

 

[Cliff Stamp]

What knives?

-Cliff

 

[Satrang]

The knives were all customs of varying design. One a fighter, one fairly fat bellied skinner. The fighter was interesting in that it was polished and you could see the carbide bands running lengthwise when you angled it in the light. The band of carbides that broke out at the edge, you could follow back into the blade. The microstructures of both of these showed a heavily banded structure with a carbide size range quite high for thin sizes. Further investigation into the origin of the steel found that the D2 came from precision ground flat stock and the producer of the ground flat stock cuts their material from plates of steel and not sheet product. Everything made sense then.

 

[Cliff Stamp]

Did you do any work with them, I would not imagine the edge durability was high.

-Cliff

 

[Satrang]

No work was done with them at all. Both were heat treated and nearly complete. The fighter just needed scales and the skinner needed scales and buffing. These were one of those "what the heck is this" scenarios. There were at least a half dozen of the skinners that went out that did not show the edge chipping. According to the maker all went well in the field and continues to do so today. My feel is if you could avoid the large banded carbides right on the edge you would see normal performance assuming the thermal treatments were ok. My concern with the banded carbides is the potential for cracking. It is longitudinally oriented but is very weak structure wise. Don't pry and twist.