AUS-8, 420HC, 440A or 440C?

[Bowzer]

Another point about steel selection to bear in mind is: What will I use this knife for? For some purposes 420 and 440A may be superior (such as in use around water or other rust causing fluids where the knife receives little care). Other activities, such as cutting up used carpet or cardboard, require good edge retention.

My experience is that most cheap stainlesses don't stand up very well to prolonged cutting tasks whereas carbon steel seems to do much better.

 

[WYK]

I don't think AUS-8 and 440C can be considered low end steels at all. 440C is probably the best general purpose steel around, it offers no particularly noteworthy advantages, but unlike other steels, it has no weaknesses either.
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440C is a brittle steel - it isn't very strong, and it's more difficult to sharpen than most carbon steels. D2, M2, S30V, CPM-3v, and most all other properly treated knife-making carbon steels are stronger, hold an edge better, and can take more shock. I don't know about calling 440C and Aus8 'low end' unless you are using price as the determination. They are good steels if you need stainless. But, they do have their drawbacks. If you know how to take care of a knife, there's no real reason to use stainless, though.

WYK

 

[averageguy]

"440C is a brittle steel - it isn't very strong, and it's more difficult to sharpen than most carbon steels. D2, M2, S30V, CPM-3v, and most all other properly treated knife-making carbon steels are stronger, hold an edge better, and can take more shock."

You must have missed this chart posted not too long ago.
http://www.bladeforums.com/forums/showthread.php?t=349821

Barry Dawson has been using 440C for three decades. His differentially treated 440C blades are as tough as they come.
Given that during this time more custom knife makers have offered 440C in their knives than virtually any other steel, I would say there are those including myself that disagree with you.

 

[Cliff Stamp]

You must have missed this chart ...

That chart actually shows those steels having higher toughness and wear resistance, some slightly, some much greater.

...differentially treated 440C blades are as tough as they come.

You can adjust the temper on any steel and it will get tougher and more ductile, but there are limits. You are never going to get the shock resistance and strength of steels like S7 in 440C. If this was not the case there would be no need for different steels obviously because one steel could do everything with the right heat treatment.

Did the maker at any time actually claim that he could achieve the toughness, ductility and strength of spring and shock steels with 440C? Plus of course differential tempering does little to nothing to improve the durability of the edge, it mainly gives the blade as a whole more flexibility and add to its ability to take heavy shocks on the spine.

-Cliff

 

[averageguy]

The chart actually shows similar toughness and wear resistance to D2 and M2.

Are there better steels - yes, but these are uncommonly used as you know.
While O1 and A2 are tougher, there wear resistance is less.

440C is a premium steel and it is plenty strong and it is still a popular choice for many custom makers today.

 

[Lil Timmy]

440C is a brittle steel - it isn't very strong, and it's more difficult to sharpen than most carbon steels. D2, M2, S30V, CPM-3v, and most all other properly treated knife-making carbon steels are stronger, hold an edge better, and can take more shock. I don't know about calling 440C and Aus8 'low end' unless you are using price as the determination. They are good steels if you need stainless. But, they do have their drawbacks. If you know how to take care of a knife, there's no real reason to use stainless, though.

WYK

S30V is a stainless steel, and is much more brittle than 440C. D2, M2, S30V, and CPM 3V are all harder to sharpen than 440C, for the same reason that they hold an edge longer.

 

[Cliff Stamp]

S30V is a stainless steel, and is much more brittle than 440C.

What is that based upon? The charpy values are similar. It doesn't bend very far before it breaks, but neither do many of the high carbon stainless steels.

D2, M2, S30V, and CPM 3V are all harder to sharpen than 440C, for the same reason that they hold an edge longer.

Even on cutting which is dominated by wear resistance, that isn't true because machinability isn't inversely proportional to wear resistance in that manner.

CPM steels can improve machinability and wear resistance at the same time by improving carbide distribution. CPM-3V isn't even overly difficult to machine.

440C has a reputation for poor ease of sharpening for some such as Jeff Clark who has noted this before :

http://www.bladeforums.com/forums/showpost.php?p=3063834&postcount=7

Buck also switched from it to 420HC for this reason, or so they claim anyway, 420HC would also be easier / cheaper to make knives from.

The chart actually shows similar toughness and wear resistance to D2 and M2.

The M2 there has the hardness much higher than it is usually ran in knives, at the same hardness M2 is much tougher and more ductile.

440C is a premium steel and it is plenty strong and it is still a popular choice for many custom makers today.

Yeah, it is a decent high carbon stainless, strength isn't really an issue with most hardened steels, they are all pretty difficult to bend at ~60 HRC, some just don't bend very far before they break or can't take much impact.

-Cliff

 

[Lil Timmy]

So you are going to say S30V is LESS brittle than 440C?

 

[Cliff Stamp]

Hossom and many other knifemakers claim it is much tougher, in terms of impacts it reacts similar to the other steels I have used which makes sense considering its charpy values. It tends to shatter when it breaks by prying and has low ductility, but few of those class steels do well in that respect though ATS-34 has always tended to break clean.

There is also a wide range of performance, the S30V Reeve uses is far inferior to ATS-34 I have seen, his is brittle and soft at the same time. Same with edge retention, some like VG-10 a lot better than S30V which I would expect is due to a softer S30V blade. It is too bad all knives are not individually HRC tested, it would eliminate a lot of the contradictory information floating around.

So yes and no, in some makers it is more brittle, and weaker with less edge retention, but that isn't the steel just the choice of heat treatment.

-Cliff

 

[WYK]

You must have missed this chart posted not too long ago.
http://www.bladeforums.com/forums/showthread.php?t=349821

Barry Dawson has been using 440C for three decades. His differentially treated 440C blades are as tough as they come.
Given that during this time more custom knife makers have offered 440C in their knives than virtually any other steel, I would say there are those including myself that disagree with you.

Disagree all ya want - you're wrong. I did not say S30V WASN'T brittle, just tougher at the same hardness levels(5X tougher on the Charpy test according to CPM itself if you look at their web page data) and holds an edge better (45% better according to CPM's web page again).

The chart you saw had several responses to it - both from me and Cliff. If you read those responses, you would have understood why that chart had no value, you also would not have said I didn't see it - I had a post in response, afterall. You may want to do some homework before you write next time.

Back to 440C. 440C has a lot of carbon in it. For a stainless with high carbon and high chromium, it would be impossible not to be brittle compared to non-stainless steels at the same hardness levels. I hope it was clear that time. It is simple physics. Certain elements have certain properties they give to steel - regardless of heat treating, I would put my differentially treated L6 bandsaw steel blade up against anything Dawson can manufacture out of 440c - and he stands even less chance against my bowies in 5160, and I haven't even been using 5160 steel for over 20 years. In fact, no matter how long you use 5160, or what your name is, with a proper heat treat stainless can't touch it for toughness. It's not experience or voodoo magic - it's physics.

No chart will make physics disappear, regardless of how inadequate or out of context it was posted If you think for a moment that S30V at 59-61 RC has the same wear resistance and toughness M2 has at 61 RC, you're confused. Mostly because that chart shows M2 at 65-68 HRC - something you'll never see it hardened to for knives. You would have realized that if you clicked 3 web pages away and saw the data on M2 and S30V on crucible's web site.

WYK.

 

[averageguy]

First off WYK, your post was off topic. Why don't you go back and read the thread title and the first post. You might notice he didn't ask how it compared to carbon steels, D2 M2 S30V or CPM3V.

Second, you stated 440C wasn't very strong - wrong again.
A handbook published by the American Society for Metals in 1994 states:
"440C is capable of attaining, after heat treatment, the highest strength, hardness and wear resistance of all the stainless alloys"
Stainless has evolved but 440C is plenty strong.

Regardless of your post regarding that chart, it stands on its own as a benchmark and it shows similar toughness and wear resistance to D2 and M2.
And as I said before better wear resistance than some other high carbon steels.

440C is a premium steel and a benchmark steel.

It is common knowledge that 5160 is a tough steel.
I seriously doubt you have anything on Barry Dawson. When you have made a name for yourself you can tell me how much tougher your knives are.

 

[Roman Landes]

Hi,

if one wants to understand witch properties of a steel are useful for knives this may help to explain!

http://www.schmiedecafe.com/forum/attachment.php?attachmentid=83

The basic manual for the sheet you find at the starting thread in English here
http://www.schmiedecafe.com/forum/showthread.php?t=339&page=2&pp=20

If one wants to discuss different properties of steel, it is helpful to understand the basic behavior with either focusing on the edge, as well as looking at the whole body of the blade.

In the chart you find the 440C featured as well as the S90V.

The S30V basically looks the same as the S90V in terms of carbide size and distribution, just the amount of carbides in relation is a bit less in the S30V.

So for the discussion you now have a basic pic of the steels you want to discuss and here magnified 1000x and put into the model of the edge.

Now looking at the two opponents, both are high alloyed steels but with different looks inside.
The 440C standard steel grade is conventionally produced and shows large segregated lines of huge carbides, whereas the S30V has more alloys in total, but due to the PM production method the steel is evenly structured inside.

Note: Neither one of the steels has been designed especially for knives, although they have been used widely in that field.

Since their inner structure is significantly different, they will of course behave different in terms of cutting behavior such as (cutting ability, edge holding ability, type of cutting action, sharpen ability)

What helps the model of the edge to see?

Employing steel like 440C in a edge will effect the behavior of the edge in terms of stability.
One can say, large carbides embedded in the edge, will give in the first run a good wear resistance, because the carbides are much harder than the matrix surrounding it.
Well that’s only true if the angel of the edge is dull enough (40° plus) to hold the monster carbide in place.
You will get a weak edge, when you go below 40° in edge angle.
(experiment with the print!!)

Looking into the S30V obviously the carbides you see, don’t look as big as the 440C, but the total amount is greater than the 440C, and it is so much that the relation between the matrixes around is the determining factor for its behavior as a cutting edge.
Again when you employ steel like this one, our basic understanding is, in an edge the wear resistance is very high, even more than the 440C
But only, if you use a dull enough angle (40°plus) to keep the large volume of carbides at their place.
On the other hand, one will get a weak edge when you go below 40° in edge angle.

Now the subject we talking about is the stability of the edge, when it comes down to fine angles and high cutting performance.
The stability of the edge is an equivalent to edge holding, which as a measurable parameter that summarizes the effect of,
 steel structure,
 heat treatment,
 and geometry (edge angle),
in an edge.

Unfortunately employing a edge angle of more than 40°, is decreasing the cutting ability (which is driven by geometry only) of a blade significantly.
So what one can do, is to put a coarse grinded edge on this type of blade to regain some of the lost potential caused by the dull angle.

Looking at the factor steel and geometry only to keep it simple at the moment, we just assume that the HT is perfect.

But back to what you get out of this.
I used many of the steels discussed for knives yet and had my own experiences with them.
To get an answer towards their behavior, I also make the practical tests (use). To my experience, the basic behavior of either one of the steels matches perfectly with the theoretical model I work with.

 Therefore neither one of the discussed steel gets really super sharp nor they are easy to sharpen (High wear resistance due to large or large amounts of carbides)
 The sharpness you get is a edge with micro serrations after short use and gives them good slice cutting abilities (Again: High wear resistance due to large or large amounts of carbides)
 This kind of sharpness that is reached after short use is kept very long (coarse micro serrated edge) (Again: High wear resistance due to large or large amounts of carbides)
 Only steeper angles (40°plus) have enough stability (Again: High wear resistance due to large or large amounts of carbides)
 Although the complete geometry of the blade has to be thicker because of the basic brittle behavior of both of them, which makes them not good to have them e.g. for thin high performance knives. (Again: High wear resistance due to large or large amounts of carbides)
 If HT is done right (Cryo and low temper) corrosion resistance is good enough (Enough Chromium more than 13% solution in the matrix by proper HT)

Now what you see is that the technical discussion of steel only is a single sided one.
To discuss the steel in the application “knife”, one has to involve the discussion of geometry as well, as the one about the correct HT.
But not to end the cycle, once the technical discussion is finished, one has to start it again, when you discuss about the job that needs to be done with the blade and the person who is using it.

Of course we can expand the discussion towards any kind of steel! e.g. O1,D2, ATS

RGDS Roman

 

[STR]

All the 440 steels are going to be popular in the market. Today knives sell a whole lot based on their looks instead of performance and 440, particularly 440C can be polished to such a high level that it is used for making mirrors, so that means it makes for a very nice looking finished blade. When a steel can look that good it is going to attract people to it so there will always be some makers that prefer 440C over anything else because of the way it looks when finished. Thoughts of it's cutting ability are not an issue. It works and fits the bill as a great steel for cutlery uses. I've never had a 440C blade I didn't like.

I read a while back that the mirrors on board the space shuttle and those in air port and air line wash rooms were made of 440C also. I don't doubt that 440C can be found in rest stop areas all across the country functioning as mirrors. Proof again of the high polish it can be brought up to in the right hands.

Still, when I was young Gerber was making the Premium knives of the time in their Sportsmans knives. I have several of these old classics in my collection. Great knives and made with 440C steel blades. These knives hold their own in cutting performance with anything manufactured today plain and simple. I own one that is an old standby that has seen lots of pocket time. The others I have are mint and unused but just as nice. These old 440C blades are a bit of a challenge to sharpen but they hold their edge as good as anything I've ever had. Don't know the Rc hardness on these but it's hard whatever it is.

 

[Cliff Stamp]

Neither one of the steels has been designed especially for knives...

That is how Crucible actually promotes S30V. In fact Chris Reeve has commented that he was part of its development. It is even in the Steel FAQ as being designed specifically for knives.

Unfortunately employing a edge angle of more than 40°, is decreasing the cutting ability (which is driven by geometry only) of a blade significantly.

You can pretty much eliminate this factor as well as the machinability issues by using a secondary edge angle. As the secondary edge bevel is very narrow, a small fraction of a millimeter, not even visisble by eye. It doesn't reduce cutting ability significantly plus it is trivial to sharpen even with difficult to machine steels because the amount of material which needs to be removed is minimal.

Therefore neither one of the discussed steel gets really super sharp ...

I have seen many S30V blades which are sharp enough to float hair off the arm without touching the skin. Many custom makers would object to saying S30V could not get very sharp. Even in the production field a high sharpness isn't a problem, Spyderco's S30V blades are really sharp, push cut light newsprint easily for example.

A handbook published by the American Society for Metals in 1994 ...

The date is kind of important. Note that most books as well don't contain information right up to the date of publishing for obvious information so you are looking at material which is more than ten years out of date.

When the authors were writing that did they have access to ATS-34, 154CM, S30/60/90V, BG-42, ZDP, etc. . For any blade material there was a time when it was the premium choice.

One question would be how far from the top would you have to go for a steel to still be premium? In a small light use knife S90V would be a better choice, but is 440C still premium?

I see it as a solid benchmark for the high carbon stainless steels, there are stainless steels which will surpass it in various areas, but it does the same as well to a lot of others. In particular for the title of this thread, outside of sharpening concerns it would be the better choice for light use knives.

-Cliff

 

[Sword and Shield]

All thing equal -same knife, same heat-treat, same grinds-, 440C will outcut any of them. However, it is also the least stainless. That's not to say it's bad, I've a few fillet knives of 440C and they show no staining.

 

[Roman Landes]

That is how Crucible actually promotes S30V. In fact Chris Reeve has commented that he was part of its development. It is even in the Steel FAQ as being designed specifically for knives.

Well to my mind that dosent make much sense, if you only look at the econamical facts making the steel only for knifemakers definitely doesn’t pay the bills, because of the little amounts used by them.
I guess the simply needed something tougher for some kind of industrial application whereas the knifething just makes good marketing. By the way also the metalurgical design of the alloy followed this fact.

You can pretty much eliminate this factor as well as the machinability issues by using a secondary edge angle. As the secondary edge bevel is very narrow, a small fraction of a millimeter, not even visisble by eye. It doesn't reduce cutting ability significantly plus it is trivial to sharpen even with difficult to machine steels because the amount of material which needs to be removed is minimal.

Well egde angle is edge angle and the physics are clear, 40 plus is 40 plus and works alike no matter how small it is. Of course, when you have not so much material to remove the sharpening action is easier to be done all high quality kichen knifes work like this.
What you discribe is, you thining the blade on the lower grind (secondary bevel) that is good so the wedge effect decreases in this area and things that are stiffer to cut do not work as strog against your own force but this only works till the thing gets thik again on the back unless the compelte section is nicely thin 2mm max.

But the same time you do so you have less material absorbing the force if a deflection on the edge happens and chipping of the edge becomes easier than before. So you will be limited towards thinning of the blade which also limits your ability to cut.
And because of the brittleness these hyper alloyed steels have the limits are way beyond eutectic or hypereutectic steels like O1.
Basically you always end up making a thik bladed knife, with an more or lesse dull edge, employing micro/ macro serrations for slicecutting witch is good for alldays if this is what you want.

I have seen many S30V blades which are sharp enough to float hair off the arm without touching the skin. Many custom makers would object to saying S30V could not get very sharp. Even in the production field a high sharpness isn't a problem, Spyderco's S30V blades are really sharp, push cut light newsprint easily for example.

Well you get them sharp, but not maximum like carbon steels and the super sharpness turns into a fair sharpness which feels aggressive, because of the serrations that start to to grow with every use.
The reason why, you find in the sheet (model of the edge) the large carbides of eihter one of the hyperalloyed steels simply chip already with sharpening because of the low stability they have when you use slim angles
Actually you can sharpen a piece of mild steel and it gets sharp like a straight razor but for how long. And, you can get a 90° angle also very sharp, but cutting ability and edgeholding of that type of geometry and high sharpness is very very limited.

 

[Cliff Stamp]

Well to my mind that dosent make much sense, if you only look at the econamical facts making the steel only for knifemakers definitely doesn’t pay the bills ...

I would not argue otherwise, but that isn't what they say.

What you discribe is, you thining the blade on the lower grind (secondary bevel) that is good so the wedge effect decreases in this area...

You can do this, J.J. of Razor's Edge recommends this for example, but I was speaking just of allowing a secondary edge bevel. Thus say for example if you want to sharpen at 15 degrees, cut the edge at 13 with x-coarse hones, these will shape the edge quickly regardless of the steel. Now you actually sharpen the edge at 15 which creates a small micro bevel only and thus the sharpening is very fast in total regardless of the steel.

...this only works till the thing gets thik again on the back

Yes, as you keep sharpening at 15 degrees the bevel starts becoming less and less micro and thus sharpening time increases. Once this becomes significant you just recuct at 13 with the x-coarse hone which again is very fast irregardless of the steel type.

For example :

http://i7.photobucket.com/albums/y269/CliffStamp/Spyderco/paramilitary/hole_paramilitary.jpg

After the above work, plus some harder metal chopping which left the edge actually visibly damaged, the primary edge was reset with an x-coarse waterstone in just a couple of minutes. Now a secondary edge bevel was applied near instantly, thus total sharpening time was minimal and this is obviously a very extreme case of blunting.

But the same time you do so you have less material absorbing the force if a deflection on the edge happens and chipping of the edge becomes easier than before.

Yes, as you reduce the edge profle you lose strength, but most edges are far over thickened for the work most knives do. Most of mine are ~10 degrees per side with some of them ~5 degrees per side and they cut woods, foods, ropes, etc. perfectly well. The only blades I run at 15 degrees per side are heavy wood choppers, and the only ones I run at 20 are those designed to cut bones and metals.

And because of the brittleness these hyper alloyed steels have the limits are way beyond eutectic or hypereutectic steels like O1.

Yeah you lose toughness with a lot of those highly carbided steels, but for a lot of knives you don't need it.

...an more or lesse dull edge, employing micro/ macro serrations for slicecutting witch is good for alldays if this is what you want.

Well a lot of cutting does use a drawing motion and for this an aggressive edge works much better, giving you more cutting ability (less force required on a draw) and better edge retention.

Well you get them sharp, but not maximum like carbon steels ...

In theory, the really fine grained steels should be able to be honed to finer edges, but in practice it doesn't have an effect for many reasons often simply because rarely does anyone actually use abrasives which are fine enough to even bring out this difference.

For example it is common for the ABS guys (who do use very fine grained steels like 52100) to actually finish sharpening on an india stone which leaves the edge many times rougher than the inherent carbide aggression of even the most aggregated steel.

Even for those that use very finish finishes like Jerry Hossom, there are little complaints about the initial sharpness of his blades, or Spyderco's S30V, etc. . Even steels like D2 take high polishes well and stay sharp for a long period of time, check out the work of Swamp Rat, Mel Sorg, Bob Dozier, etc. .

-Cliff

 

[WYK]

First off WYK, your post was off topic. Why don't you go back and read the thread title and the first post. You might notice he didn't ask how it compared to carbon steels, D2 M2 S30V or CPM3V..

He asked for information on 440C. I answered his question. Just because it wasn't what he or you may have wanted to hear, does not make the topic different. Having options, and someone willing to give them, is what advice is about. We're talking about stainless, regardless.
Read my statement. Compared to other options, 440C is not a top choice. It may be affordable, but it isn't my first choice, and I stated as such.

Second, you stated 440C wasn't very strong - wrong again.
A handbook published by the American Society for Metals in 1994 states:
"440C is capable of attaining, after heat treatment, the highest strength, hardness and wear resistance of all the stainless alloys".

Hrm... 1994. That was like..10 years ago - before S30V, S90V, VG-10, 154CM, et al became more mainstream - all of which are stronger than 440C at the same hardness levels. Join us in 2005, and there's other options. Personally, I would opt out of stainless whenever I could. Don't get me wrong, I have stainless blades. I just prefer my carbon blades because they perform better the vast majority of the time.

Regardless of your post regarding that chart, it stands on its own as a benchmark and it shows similar toughness and wear resistance to D2 and M2.

It stands on it's own - and that's all it stands on. Without comparing hardness, and tool use, the chart is worthless. In fact, to show how easy it is to make a chart deceptive - many on this thread think it's a single chart. It is not - it is a combination of at least 2 charts. Neither of which state the hardness of the metals in the comparison - making it worthless. You could put 5160 up there annealed, and the shock tests would be off the chart. Even if one were to do the minimal amount of homework and go to CPM(which SOME did not bother to), it shows the hardness levels to be different, placing M2 at 65-68HRC - totally unsuitable for knife use. This means your statement was derived from incomplete information at best - and false and misleading information at worst. Tool steel tempered/heat treated metal is rarely suitable for knife making. Knife making requires specific tempering and hardness for specific tasks that are generally much different than die cutting or stamping etc..

And as I said before better wear resistance than some other high carbon steels.

440C is a premium steel and a benchmark steel.
.

I agree. However, you specifically stated M2 and D2, both of which have better wear resistance and strength than 440C at typical hardness levels used in cutlery. Though D2 is only a tad stronger, it is stronger, and thus less brittle.

It is common knowledge that 5160 is a tough steel.
I seriously doubt you have anything on Barry Dawson. When you have made a name for yourself you can tell me how much tougher your knives are.

You just stated my case. 5160's toughness is legendary - nearly all ABS flex tests are done using 5160 - like 99% of them. I'll put any of my 3/16th" thick 5160 Bowies up against anything Dawson, or any other maker, makes in 3/16th 440c for strength. It's not the knife maker - that's why you are confused that I am trying to compare myself to Dawson. I am not doing any such thing - it is the steel. A 3/16th" thick Bowie blade of 5160 differentially treated is nearly impossible to break with bare hands(assuming a good heat treat, of course). The spine is somewhere in the neighborhood of 45 RC, the middle at 50ish, and the edge at 56-59. I can take a 5160 bowie and bend it into a donut - the grain structure and molecular bonds in 440C physically won't allow that. Next time you go to work, you're trusting your life on 5160 to keep from breaking after flexing thousands of times each day as part of your suspension. There's a reason why it's there instead of 440c, and there's a reason why it's used far more often in large knives instead of 440c.

WYK

 

[Cliff Stamp]

...M2 at 65-68HRC - totally unsuitable for knife use.

M2 maxes at ~65 HRC, M4 gets a couple of point higher. M2 full hard, while quite brittle, makes very nice light use knives, they have little flexibility or toughness so you can't impact or twist them, but the tensile strength is very high, and that combined with the high wear resistance gives extremely high edge retention.

Though D2 is only a tad stronger, it is stronger, and thus less brittle.

Strength usually refers to resistance to deformation under slow loads, defined by yeild / tensile strength, toughness being the ability to handle sudden loads, charpy impact values. These steels are similar in toughness, neither is high. D2 can get to 62 HRC, 440C is usually ~58 and thus D2 would have signficantly better edge retention usually, unless corrosion was an element.

-Cliff

 

[Roman Landes]

You can do this, J.J. of Razor's Edge recommends this for example, but I was speaking just of allowing a secondary edge bevel. Thus say for example if you want to sharpen at 15 degrees, cut the edge at 13 with x-coarse hones, these will shape the edge quickly regardless of the steel. Now you actually sharpen the edge at 15 which creates a small micro bevel only and thus the sharpening is very fast in total regardless of the steel.

Sorry cliff I simply don’t get the idea can you make a drawing please

Yes, as you reduce the edge profle you lose strength, but most edges are far over thickened for the work most knives do

Absolutely right cliff way too much over thickened I’ d say

Yeah you lose toughness with a lot of those highly carbided steels, but for a lot of knives you don't need it.

Yes right, because they are so thick that features like toughness simply do not count. Manny blades I see from custom makers are so thick on over weighted that they are difficult to handle

Well a lot of cutting does use a drawing motion and for this an aggressive edge works much better, giving you more cutting ability (less force required on a draw) and better edge retention.

Yes for the average class of cutting (slice cutting) that is a fact

Though D2 is only a tad stronger, it is stronger, and thus less brittle.

Well I doubt this D2 the amount of undissolved carbides is just huge so the toughness is less at the same level of martensitc grain size.

See the macrostructure here.
http://www.schmiedecafe.com/forum/attachment.php?attachmentid=82
magnifacation is 200x
well of course the 440 C doesn’t look much better but there still is a slight difference
to my taste both of the steels are nothing for high performance in knives the are good tool steels that’s what they have been made for.
One has to explain why I should use a steel like D2 if it is neither fully corrosion resistant, nor it gets really sharp, it isn’t easy to heat treat or sharpen by easy means you cant make thin and blades and after a polish you see the ugly monster carbide structure with bare eyes.