What is the best steel for retaining high sharpness?

[LazyOutdoorsman]

What are good steels for retaining a very sharp, shaving edge? I've heard many opinions such as super blue/blue super (is there a difference?), cruwear, AEB-L, 52100, etc.

Also, what makes a steel retain that super sharp edge as opposed to "breaking down" into a working edge?

[vivi]

I think how you sharpen matters as much as anything. stropping the same apex back to shaving sharp over and over won't give you the same 90%+ sharpness retention as stones.

as far as steel, in my experience high hardness lower carbide seems to do best here.

[zhyla]

I think Vivi is right. I’m no metallurgist but without carbides I believe edge retention is dominated by hardness.

I would caution against throwing around “shaving sharp” unless you’re actually talking about a razor.

[Bolster]

Interestingly, Super Blue, AEB-L, and 52100 are all very low on the CATRA TCC scale, which is a measure of retaining sharpness. But then--you're not shaving abrasive impregnated cards, you're shaving your face. Which is probably a little different.

I guess my question is: Are you more interested in retaining high sharpness, or attaining high sharpness?

[elena86]

Interestingly, Super Blue, AEB-L, and 52100 are all very low on the CATRA TCC scale, which is a measure of retaining sharpness. But then--you're not shaving abrasive impregnated cards, you're shaving your face. Which is probably a little different.

I guess my question is: Are you more interested in retaining high sharpness, or attaining high sharpness?

The OP was quite clear. It's ''retaining'' and I guess he asked for examples not a metallurgical lesson. I am also very interested in the subject.

[Synov]

It depends on what you're cutting, but the most important thing for maintaining a fine edge is a small edge angle. Therefore you need a steel that can support a small edge angle, and the analysis becomes an edge stability question rather than an edge retention question. You want a tough, hard steel with low carbide volume to prevent cracking, chipping, deformation, and carbide pullout. Steels that fit these parameters are Z-Tuff, 3V and 1V.

You should also read https://knifesteelnerds.com/2018/08/27/ ... stability/

[jmj3esq]

S90V

[LazyOutdoorsman]

I think how you sharpen matters as much as anything. stropping the same apex back to shaving sharp over and over won't give you the same 90%+ sharpness retention as stones.

as far as steel, in my experience high hardness lower carbide seems to do best here.

Thanks, that makes more sense. maybe i was mixing up "strop-ability" with fine edge holding

[vivi]

there's this weird concern in knife enthusiast circles about over sharpening & reducing the life of the blade.

typed out by folks with 50+ knives

a lot of people have the mentality of doing the bare minimum to bring shaving sharpness back. whether that's stropping, doing a few strokes on the fine sharpmaker rods, or whatever else they like to use as a finishing step.

I sometimes use my extra coarse medium rods between full sharpenings to do touch-ups. Same deal with my chef knife roll and my medium bench stone.

However, I always see both greater front end sharpness and better edge holding after a full sharpening VS a touch-up.

I define each as:

full sharpening: removing the current edge bevel by resetting the edge on a very coarse stone, then taking the apex to whatever level of polish I desire from there

touch-up: refining the apex of an existing bevel with a finishing level stone

This influences my sharpening habits two ways.

Using coarse final finishes means my touch-ups can achieve similar sharpness and edge holding as a full sharpening. I touch up my M4 Manix XL and Magnacut Military 2 on a DMT Coarse, for example.

Utilizing microbevels means I can do a full sharpening very quickly. I can reset the edge on a 140 grit diamond plate in five minutes unless I'm thinning the edge angle out too. From there I can take the apex up to 8,000 grit in 3-5 minutes since I'm refining the apex at a more obtuse angle.

for granpappy who carried one slipjoint for 50 years those concerns made sense, but for most people on sites like this there's no need to worry.

[dsvirsky]

there's this weird concern in knife enthusiast circles about over sharpening & reducing the life of the blade.

typed out by folks with 50+ knives

Not just knife enthusiasts. I see the same logic in articles about kitchen knives, aimed at the average guy/gal on the street: use a steel to restore your edge, rather than a hone, so you don't wear out your knives. If you wear out your fancy $180 chefs knife in 5 years (unlikely), your cost was less than 10 cents a day.

[Deadboxhero]

Also, what makes a steel retain that super sharp edge as opposed to "breaking down" into a working edge?

Differences in retained austenite, carbide size/volume, hardness, stress/fatigue, grain growth, plate martensite vs lath and heat build up during processing.

Lastly, your sharpening skill is probably the biggest most immediately controllable factor.

This means even the same steel can have a different behavior depending on the factors above.

7 years ago I had a similar question, at the time it seemed like CPM 4V was the answer since it seemed like back then it was the nexus of strength and toughness.

I ran it 65rc and ground the knife as thin as possible and the edge failed hard carving wood.

Maybe it was the 8% carbide volume?

I talked to Larrin at the time and he recommended a "matrix" steel.

Caldie, which is technically a matrix of "4V" without the carbide.

However, to dissolve all the carbide causes EXTREME grain growth without carbides to pin grains along with detriments from the other variables I shared above due to overaustenitizing.

This causes the properties to drop in performance.


So, it might not be as simple as hardness, impact toughness and carbide.

7 years later and I certainly know that the factors I shared above

(retained austenite, hardness, stress/fatigue, grain growth, plate martensite vs lath and heat build up during processing, how it's sharpened)

Play a bigger role than just the carbides alone.


To actually answer your the question it requires physical experiments that factor in the variables I shared above along with good control.

Simulation and speculation alone will not work.

You'll have to invest into some equipment and gather more knowledge and skills to execute the testing and correct your procedures after scrutiny.


Regardless, you will never achieve a fine edge that holds that kind of sharpness similar to how the working edge lasts but there are certainly features that could prolong it compared to other conditions.



TL:DR

Steel chemistry is not the only factor but the name of the steel gets the credit or the blame for expectations good or bad.

Now that we got that out of the way the answer is Nitrobe 77.

[dan31]

I hope we see a Native 5 in 52100. I have the Military 52100 sprint and the steel and heat treat are ideal for maintaining a fine edge. Perhaps it may happen if 52100 remains available in sheet form for Spyderco.

[LazyOutdoorsman]

Also, what makes a steel retain that super sharp edge as opposed to "breaking down" into a working edge?

Differences in retained austenite, carbide size/volume, hardness, stress/fatigue, grain growth, plate martensite vs lath and heat build up during processing.

Lastly, your sharpening skill is probably the biggest most immediately controllable factor.

This means even the same steel can have a different behavior depending on the factors above.

7 years ago I had a similar question, at the time it seemed like CPM 4V was the answer since it seemed like back then it was the nexus of strength and toughness.

I ran it 65rc and ground the knife as thin as possible and the edge failed hard carving wood.

Maybe it was the 8% carbide volume?

I talked to Larrin at the time and he recommended a "matrix" steel.

Caldie, which is technically a matrix of "4V" without the carbide.

However, to dissolve all the carbide causes EXTREME grain growth without carbides to pin grains along with detriments from the other variables I shared above due to overaustenitizing.

This causes the properties to drop in performance.


So, it might not be as simple as hardness, impact toughness and carbide.

7 years later and I certainly know that the factors I shared above

(retained austenite, hardness, stress/fatigue, grain growth, plate martensite vs lath and heat build up during processing, how it's sharpened)

Play a bigger role than just the carbides alone.


To actually answer your the question it requires physical experiments that factor in the variables I shared above along with good control.

Simulation and speculation alone will not work.

You'll have to invest into some equipment and gather more knowledge and skills to execute the testing and correct your procedures after scrutiny.


Regardless, you will never achieve a fine edge that holds that kind of sharpness similar to how the working edge lasts but there are certainly features that could prolong it compared to other conditions.



TL:DR

Steel chemistry is not the only factor but the name of the steel gets the credit or the blame for expectations good or bad.

Now that we got that out of the way the answer is Nitrobe 77.

Thanks for the details!
You said that nitrobe 77 takes a crazy good edge. Does that generally mean knives that easily sharpen do well in high sharpness retention?

[Enactive]

In my uses, laminated Mora blades do well and so do Spyderco Rex45, V-Toku 2, Suoer Blue. I agree that high hardness and lower carbide volumes are generally better, but strength and hardness are your friend-- high Charpy toughness isn't always important at pocket and carving knife size and proportion, nor in kitchen use. Edge stability and strength are your huckleberries-- which are harvested from strength and hardness combined with finer, more homogeneous grain structures, and good sharpening for the application.

Geometry trumps all of this!

[Scandi Grind]

there's this weird concern in knife enthusiast circles about over sharpening & reducing the life of the blade.

typed out by folks with 50+ knives

Not just knife enthusiasts. I see the same logic in articles about kitchen knives, aimed at the average guy/gal on the street: use a steel to restore your edge, rather than a hone, so you don't wear out your knives. If you wear out your fancy $180 chefs knife in 5 years (unlikely), your cost was less than 10 cents a day.

Yeah, and if you ever get there kitchen knives can be thinned to get them back to proper geometry and last another many years. The few times that I have seen people wear out a blade by sharpening they were knives that were 20+ years old and often the only knife that the person had for it's role. You don't want to go forming massive burrs with coarse stones all the time or blades will wear out faster, but with reasonable sharpening habits I think of sharpening as increasing the useful life of the blade, not as an act that is reducing its life. You could never sharpen and it would last forever, but it would only be as useful as a butter knife eventually. Then you just have an expensive butter knife. Sharpen it and you will enjoy a high performance tool for many years. And if it ever wears out, it will certainly have been worth it's price for all the work it did for you.

[Mage7]

Interestingly, Super Blue, AEB-L, and 52100 are all very low on the CATRA TCC scale, which is a measure of retaining sharpness. But then--you're not shaving abrasive impregnated cards, you're shaving your face. Which is probably a little different.

I guess my question is: Are you more interested in retaining high sharpness, or attaining high sharpness?

Well, that's the thing with the CATRA test that I think people understand intuitively, but then gets lost in all the conflation of terms and concepts... There's just a difference in a sharp edge with a very fine apex that can shave versus one that is sharp by the simple virtue that it can cut whatever you want it to cut. Basically think of how a very thin kitchen knife or a box cutter will still cut food or cardboard very well while you can even run your fingers along the edge without worry. Then on the other hand sometimes you might have a big thick chopper or something that you wouldn't dare touch without being delicate, but then just by virtue of the geometry being too thick it might not actually cut things very well. When it comes to CATRA, it's really more of a test of how well a dull edge still cuts than how long an edge takes to get dull.

There's a lot more intricacies to it and that's a pretty gross over simplification, and also doesn't really broach whether it makes more sense to evaluate "sharpness" by how well it cuts versus how little force it takes to initiate (and continue through) a cut, but it just so happens that Larrin has a great article about it.

https://knifesteelnerds.com/2018/08/06/ ... g-ability/

So when it comes to CATRA it's important to realize it's measuring how well a knife retains its cutting ability, and that cutting ability and sharpness are not necessarily the same thing.

[Bolster]

The OP was quite clear. It's ''retaining'' and I guess he asked for examples not a metallurgical lesson. I am also very interested in the subject.

Oh, maintaining and retaining are two completely unrelated topics, eh? I'm not sure the OP agrees:

Does that generally mean knives that easily sharpen do well in high sharpness retention?

My rhetorical question was intended to get the OP to think about which is actually more important for a shaving blade, and 'shavers' often go for 'attaining' over 'retaining.' The highest edge retention steels are typically packed with carbides, which probably isn't what the OP wants. The question was intended to invite discussion, not pass your literal parsing filters.

OK, everybody, don't give any advice in this thread that might increase overall knowledge about metallurgy. We're not here to learn. Just give examples.

[Jeb]

The best edge retention I got around here and that there is a bigger difference from the others. My 3 best.
I don't have these in any particular order either:

Rex121
M398
10V

[Spyderfreek]

Rex 45. The fine grain structure and extremely high hardness gives it a very long lasting super scary edge in my experience. Rex 45 is pretty much all fine edge.

[LazyOutdoorsman]

Rex 45. The fine grain structure and extremely high hardness gives it a very long lasting super scary edge in my experience. Rex 45 is pretty much all fine edge.

I have heard of rex 45 holding a good edge for a long time before, but only once. Have you used hap40 before? composition wise, they look very similar.

Data from zknives

Too bad spyderco doesn't sell rex 45 or hap40 knives anymore as far as I know