Stainless vs carbon steels: toughness and edge retention - what am I missing?

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big D

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Based on the micrographs I have seen at 1475˚F with a 10min soak you can get something like 0.8-0.9% C in solution max. You can use the iron-carbon phase diagram to calculate the exact solubility limit and its pretty close to that. So carbon contents above that just leads to more iron carbide
Interesting. Thank you.
 

HumbleHomeCook

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This thread got me to thinking and I finally have some time to type those thoughts out.

Why is "vastly superior" hard to answer for me?

Let me start by saying I am an unabashed, shameless, intensely loyal Shawn Houston fanboy. There are some who've felt the need to point this out in the past so I thought I'd just clarify it right up front. If you're unaware, Shawn Houston is aka Triple B Handmade, Big Brown Bear, and @Deadboxhero.

If you're so inclined, please indulge me...

Why am I such a fan? Shawn isn't a steel guru by birth or familial provenance. He's an ambulance driver who started sharpening knives. His fascination and obsession exploded and before you know it, he's not just pushing steel boundaries and learning from and collaborating with legends, he's developing his own line of abrasives just to make the steels he was obsessing over a viable end-user possibility. And yes folks, he very much wanted those abrasives to come in cheaper to make them more accessible but just couldn't make it work with his strict quality requirements.

For me, this background is important as for the first time, I personally found, and watched, a "regular" guy excelling at all things knives and it was highly relatable to me. Shawn's posts across various forums and his videos broke things down, explained things, but most importantly encouraged everyone to dive in.

He didn't know it but Shawn gave me the confidence to reapproach free hand sharpening. Then, despite my staunch opposition to these "new fangled steels" his work and communications had me trying all manner of steel. "Sharpen because you want to, not because you have to." :)

Shawn's dedication to the knife community and his unyielding willingness to share his knowledge and his intense, deep study of the craft I strongly believe had a massive impact on the popularity explosion of HS/PM steels and changed, at least in the EDC world, the landscape.

No, I'm not typing all this just to sing Shawn's praises but because it is relevant to a much bigger lesson that Shawn taught me.

One night Shawn and I are talking on the phone about this kinda stuff and I made some type of disparaging comment about all these simple steels like shirogami and such. And the guy who I'd been watching for years promote all these crazy steels reminded me of some things.

He told me there's nothing at all wrong with all those simple steels and if a person is happy sharpening often and likes simplicity then they "...can saddle up to super simple shirogami and ride off into the sunset and it's totally cool." That's a paraphrase but close.

In that comment and yeah, our subsequent conversation, but really in that comment what Shawn did was free my mind to love what I loved. Or, again, maybe better said, to remind me. Once I got hooked and started shunning my simpler steels, I kind of lost the fun and easiness of simple stuff and Shawn reminded me that it's not a popularity contest. Like what you like. Use what you want to use.

The guy who so many of us in the knife community link so strongly to "super steels" also doesn't hate simple steels.

Shawn's real lesson for me was not about "superior" steels but about appreciating all of them and choosing what you like and want and what works best for your application. But be sure to be educated on why you like what you like. Make informed decisions.

As Shawn says, "Fear no steel."
 
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Jovidah

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CATRA is a very good test of wear resistance which translates very well into slicing edge retention, be it on rope, cardboard, or bananas. There is really no reason to think that cutting food is somehow different except like you point out board impact could very well be one of the main dulling mechanisms. This is why we don’t just look at CATRA results. Since we are lucky enough to get toughness numbers, hardness/strength numbers and wear resistance numbers we can make a reasonable prediction of which steels have better edge retention everything else being equal. Of course the problem is everything else is not equal in real knives and this is why most popular steels are arguably not the best steels for kitchen knives if we only care about theoretical best performance. In reality the most popular steels are the ones that are the easiest for makers to use and the easiest for users to sharpen. We could split off ease of deburring from ease of sharpening but it really is part of ease of sharpening since sharpening is the whole process. Deburring can definitely be more difficult on some steels and especially when the heat treat is screwed up.
My issue is that most of what we do in the kitchen is not slicing... unless you're specifically talking meat slicers.
But by it's very nature the CATRA testing inherently 'favors' carbide steels that will wear unevenly resulting in a somewhat micro-serrated edge. If that is the edge you are looking for great, but that's not necessarily so. The CATRA testing doesn't contain any information about the quality of the edge in any of the stages; it's a simple pass/fail test. What kind of edge (quality) is desirable is up for debate anyway, considering the debates about ideal finishing grit.

Don't get me wrong I don't intend to dispute Larry's testing but I think we should be cautious into generalizing such an abstract test too much. It's great work but I think it's more of a starting point where further investigation is needed than a definitive conclusion.
Like I said in my first post though I think we're largely on the same page. In general lines I agree that the 'carbon is better' mythos is largely overblown.
As far as anecdotes of high alloy steels loosing their peek sharpness sooner, I think this is a myth that has been debunked by a few tests. I believe the explanation is most likely due to people using inappropriate abrasives or lacking the skill that higher alloy steels might require to not leave burrs, wire edges, overstressed apex, etc. Basically the ease of getting a clean, crisp apex on low alloy steel out weights the benefits of high alloy steels for most sharpeners. The problem with anecdotes is that it is not always clear how the edge failed, is it from deformation or micro chipping at a level that can’t be seen with a naked eye or wear. One mechanism can be mistaken for another very easily.
I don't think we've seen any testing really diving into this (with microscope pictures, etc). I do agree that the inappropriate abrasive thing definitly plays a role with certain steels, just like certain heat treatments might.
In addition, we don’t know if geometries are the same or how sharp the knives really are when comparing low and high alloy steel knives. It is just not very easy to compare real knives. When diamonds or CBN are used especially with guided systems people seem to not see these strange results of low alloy steels keeping peek sharpness longer. This leads me to believe that what we see when free hand sharpening on conventional stones is due to sharpening and not the attribute of the steels. High alloy steels that are commonly used in knives should keep any level of sharpness longer. I really dislike vg10, but it is a fine steel and if heat treated well and sharpened correctly will hold any level of kitchen knife sharpness longer than white class steels given similar hardness and same geometry. Or take something like aebl, there is absolutely no scenario where white steel would be superior to it if cutting performance is all you care about.
I do agree with you that white steel is possibly the most overhyped steel in existance; for me it dulls faster than just about any other steel I have in the kitchen.

For what it's worth, the only somewhat comprehensive test I have ever seen that actually compares sharpening stones and hints at this 'insuitable abrasive' problem you mention is this one:
 

Jovidah

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I don't think you can say this for all knives as it is both steel and geometry dependant but there are certain circumstances in which rolling or microchipping can be the dominant form of wear rather than abrasion. But that would really only support the OP's point as many common stainless steels (and even more non-stainless high alloy steels) have better balances of hardness and toughness than low alloy steels, especially the very high carbon stuff that most makers tend to use for whatever reason.
As you see in my first reaction I'm not disputing his point; I generally agree with the notion that carbon isn't outright 'better'.
I'm just saying we should be cautious about gospelizing CATRA results. They have great reliability and repeatability, but the question is their validity for the question at hand.
 

Jovidah

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Also something I haven't seen come up yet: I think one of the reasons that some of the Japanese carbon steels got such a reputation is because they are generally sold at high(er) HRC. If you know nothing else about knives it's intuitive to think that 'more HRC is more better'. VG-10 at 60 HRC vs white steel at 62 HRC? The white steel must be better right? You have to really dig into the steel science to find out that this might not be the case.

I also highly agree with the sentiment that you mostly buy 'makers / specific knives' and you sort of accept the steel choice that comes with it. I love my Masamoto KS... but if I had the choice I'd much rather have it in 1.2519 or monosteel SG2. But I don't get that choice. I quite like my Mazakis.. but I'd much rather have them in something far less reactive and with better edge retention...but again I don't get that choice (unless I'm willing to pay double).
 
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But by it's very nature the CATRA testing inherently 'favors' carbide steels that will wear unevenly resulting in a somewhat micro-serrated edge.
A couple of points:
1. Assuming silica is the dominant abrasive in food all steels will dull in this way except i. low alloy steels with <0.9% C ii. C-Mn steels (White steels)
2. If it there is some softer abrasive then only i. would not dull in this way.
3. It's certainly plausible that Micro-serrations have something to do with CATRA performance but I don't think that has been proven.

My point with these is that if what you are saying is true it just means that the small subset of very low alloy steels (low alloy with no W V and <1% Cr) might be an exception to the testing. I see no reason to assume that CATRA isn't a valid test of wear resistance vs a Silica test medium.

Anyway, I think you are right about most of what you said especially with the hardness pt above I just wanted to address the above point because it stuck out to me.
 

henkle

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As a relative noob I have two questions:

Would a master sharpener (say a Broida or a Carter) be able to sharpen a stainless knife (regardless of steel) to a degree of sharpness that would be virtually indistinguishable from a carbon steel knife sharpened by a good sharpener but perhaps not at their level?

Second, for a non-professional cook (ie home cook) would the occasional but regular touch-up on the stones mean that in theory, you would never really have to "sharpen" (an extensive exercise often cited here on KKF) the knife?
 

coxhaus

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I remember carbon steel knives in the kitchen as that is all I had when I was young. They were a pain as you really had to take care of them and cutting limes and lemons were issues and probably other things I don't remember now. And then on top of all that you kept an oil stone in the kitchen because you constantly had to sharpen them. Stainless was a blessing. The stainless was harder to sharpen and would not get as sharp as carbon steel. But overall, it was a better kitchen knife.
 
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There are a lot of cutting and edge holding attributes of knives that we attribute to steel which in many cases are not really related to steel specifically. Benefits of carbon vs stainless in many cases are some of these. The praise of carbon edge holding is most likely due to carbon knives in general being heat treated harder and having thinner geometry, this is even more pronounced when comparing older western stainless knives against Japanese carbon knives. Harder Japanese knives can support and have thinner geometry, so they cut better, edges stay sharper longer due to lower angles and possibly deform less due to higher hardness. On top of this they are easier to sharpen with conventional stones and average skill. Combination of these makes many believe that carbon > stainless, but what end users experience is not specifically related to steel or it being carbon or stainless and of course the reality is much more complex and nuanced. AEB-L is better in every category than white steel except maybe tiny bit harder to sharpen, but this difference is academic at best since either is easy when heat treated well. So if we could compare 2 exactly same knives with only the steel being different AEB-L would always win in performance.
 
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Very interesting thread … as always many points of view.

My thought … there are too many variables to draw conclusions applicable to everyone. For example … I am a home cook. I have way too many knives in my rotation and my stones and strops are an arms length away in my kitchen. If a knife shows a trace of “dull“, I reach for another, or sharpen it or strop it immediately as required. At worst I’ll wait until the end of day and sharpen anything that moves just because I want to … except for thors fancy extra hard steels.

SO …. I like carbon steels like Blue 2, Aogami Super or 52100 because they are easy to sharpen quickly to a wicked edge. Stainless is OK too but I’ve convinced myself that I don’t like sharpening it as much as carbon steel because it feel “sticky” on the stone. It’s my imagination probably because one of my all time favourite knives is a stainless Kurosaki bunka. Go figure!

I have a number of ZDP189 knives and have sharpened a number of HAP40 knives for friends and the odd customer. I don’t find myself reaching for them because they are more work and take more time to sharpen. I finally invested in a set of vitrified Diamond stones to speed things up. Once sharpened the “better” steel holds a satisfactory edge for a ridiculously long time … which is a bad thing for me because I generally don’t want to drag out my Diamond stones to sharpen them when they finally get dull … so they stay dull and I reach for my carbon steel blades when I want to get things done.

So … what does all of this mean … everything to me and probably nothing to you. Your experience is different. There are a multitude of variables in three categories … the steel, and its maker … the knife, and its maker … the owner/user, and how they use and maintain their knives.

In my opinion there is one maker whose knife everybody should try. That Bjorn Birgersson, and his knives forged to a rediculous hardness from Swedish mystery steel. His knives just don’t seem to get dull, cut like fiends and are easy to sharpen. That’s my opinion anyway.
 

M1k3

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As a relative noob I have two questions:

Would a master sharpener (say a Broida or a Carter) be able to sharpen a stainless knife (regardless of steel) to a degree of sharpness that would be virtually indistinguishable from a carbon steel knife sharpened by a good sharpener but perhaps not at their level?

Second, for a non-professional cook (ie home cook) would the occasional but regular touch-up on the stones mean that in theory, you would never really have to "sharpen" (an extensive exercise often cited here on KKF) the knife?
Diamond stones are the great equalizer when it comes to edge quality and ease of sharpening with different steels.
 

Jovidah

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Now that you mention banding...I've always wondered... I understand the visual appeal, but what does it do for performance? First time I saw it I thought it was a defect...
 
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Now that you mention banding...I've always wondered... I understand the visual appeal, but what does it do for performance? First time I saw it I thought it was a defect...
It technically is a defect, just not a defect that matters for knives we are interested in. Not to confuse it with the pattern we see in wootz/bulat/true damascus steels, as that is different.
 
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It technically is a defect, just not a defect that matters for knives we are interested in. Not to confuse it with the pattern we see in wootz/bulat/true damascus steels, as that is different.
Always been a bit unsure about banding. What makes it a defect and why are we not bothered by it?
 
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It technically is a defect, just not a defect that matters for knives we are interested in. Not to confuse it with the pattern we see in wootz/bulat/true damascus steels, as that is different.
@PeterL I'd say it does matter to knives although it depends a bit on the steel. Banding is pretty bad for toughness as it can increase carbide size. However in kitchen knives honestly it doesn't seem like toughness is a huge factor in what people want so banding is not a big deal. In steels like 26c3, I'm not super concerned about banding because the carbide volumes are fairly low and the carbide size can be more easily controlled through normalization but there are a few stainless steels that have pretty bad banding that I tend to avoid. Like VG-1, 440C, and Becut. In those cases, carbide sizes can get very large which can cause problems.
 

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There are a lot of cutting and edge holding attributes of knives that we attribute to steel which in many cases are not really related to steel specifically. Benefits of carbon vs stainless in many cases are some of these. The praise of carbon edge holding is most likely due to carbon knives in general being heat treated harder and having thinner geometry, this is even more pronounced when comparing older western stainless knives against Japanese carbon knives. Harder Japanese knives can support and have thinner geometry, so they cut better, edges stay sharper longer due to lower angles and possibly deform less due to higher hardness. On top of this they are easier to sharpen with conventional stones and average skill. Combination of these makes many believe that carbon > stainless, but what end users experience is not specifically related to steel or it being carbon or stainless and of course the reality is much more complex and nuanced. AEB-L is better in every category than white steel except maybe tiny bit harder to sharpen, but this difference is academic at best since either is easy when heat treated well. So if we could compare 2 exactly same knives with only the steel being different AEB-L would always win in performance.

Should have been the first, and only, answer. The question - and understanding behind it - lies on a faulty syllogism. Given two knives that are exactly the same except steels, all the superior characteristics that can benefit the end user COULD be proven to do just that with simple experiments by said end user.

Real world is a different prospect - just talking about having two perfectly identical knives except steels is not going to happen. It could be controlled as to be "close enough" and then yeah we could set experiments as to prove the theory closely enough - but we're drifting already.

End user scenario, that control won't happen. Exit the theory. Woving "why people say" into that is just more aggravating - when trying to tie it to theory or dispute theory.

That's why there's a resource like @Larrin - controlled settings and experiments, and even that guy can't be PERFECT, but he can control enough things to almost be. That's why there's a forum like KKF - so that we can discuss our opinions and experiences with knives. But really, while there can be a certain consensus generally, it's also a place where you have a guy saying he uses a Zwilling edge for months without sharpening, and another guy saying all Aogami Super he tried would not hold an edge for dear life, so... Somewhere in between ignorance, there are knives that are not the same, and users with different point of views and preferences that discuss them in good faith and intellectual competence, and that's the end of it.

So...
 

esoo

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Real world is a different prospect - just talking about having two perfectly identical knives except steels is not going to happen. It could be controlled as to be "close enough" and then yeah we could set experiments as to prove the theory closely enough - but we're drifting already.

These two knives are about as close are you're going to get to the same knife in different steels - Euroline Stainless (13c26) and the 1.0 version of the Carbon (52100).

The 2.0 Carbon is a slightly different profile.

I didn't have the two knives at the same time, but had the Carbon, then the Stainless, and now the Carbon again. The stainless was a functional knife, but missed something compared to the carbon.
 

ModRQC

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These two knives are about as close are you're going to get to the same knife in different steels - Euroline Stainless (13c26) and the 1.0 version of the Carbon (52100).

The 2.0 Carbon is a slightly different profile.

I didn't have the two knives at the same time, but had the Carbon, then the Stainless, and now the Carbon again. The stainless was a functional knife, but missed something compared to the carbon.

I wouldn't count on two units having the same exact geometry to same exact edge.

If we're ready to accept differences, then Sukenari would be a foisonous place to start comparing a lot of different steels. But after three, they're never entirely the same, although it wouldn't be SO difficult to control and make them much more alike. Same with the Kramers.
 

Jovidah

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Another candidate to do 2 steels, 1 knife would be the Ashi Ginga series.

And to add another (very subjective) factor to the equation that's rarely mentioned here: cutting feedback. Although I'm not sure how much of an influence carbon vs stainless has there, so far I mostly noticed monosteel vs san-mai.
 
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Another candidate to do 2 steels, 1 knife would be the Ashi Ginga series.

And to add another (very subjective) factor to the equation that's rarely mentioned here: cutting feedback. Although I'm not sure how much of an influence carbon vs stainless has there, so far I mostly noticed monosteel vs san-mai.
I don't really see how that would be steel related. I think you are right a lot of it is in the surface finish of the grind.
 

Benuser

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And to add another (very subjective) factor to the equation that's rarely mentioned here: cutting feedback. Although I'm not sure how much of an influence carbon vs stainless has there, so far I mostly noticed monosteel vs san-mai.
With the feedback discussion in the case of soft stainless cladding I remember it is often related to poor sharpening where the hard core didn't get freed enough, which results in a damped feeling. Thinning the soft stainless is no fun but very necessary.
One might think the tactile feedback has all to do with the blade's more or less thin geometry or steel hardness. Well, soft carbon Sabs do offer a huge feedback.
 

Delat

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I wouldn't count on two units having the same exact geometry to same exact edge.

If we're ready to accept differences, then Sukenari would be a foisonous place to start comparing a lot of different steels. But after three, they're never entirely the same, although it wouldn't be SO difficult to control and make them much more alike. Same with the Kramers.

Yu Kurosaki typically does the same knife in several different steels. For instance his Fujin series was available in AS, VG10, and R2. I don’t think there’s a lot of daylight between those steels though; I picked AS as the best of the bunch and was pretty impressed with it - still regret selling it on BST.
 

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Even if a maker makes the "same knife" in different steels, there is so much inter-knife variation in the grind of hand made knives that the knives are not directly comparable anyway.
 

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Sukenari you could sample more than any other maker or brand I know of. The only sad thing is they don't actually do a very simple Carbon steel, and if they once did it'd have to be verified that geometry is at least close enough to what it is today that we could bank on having control towards making them similar. Also, they are very consistent in regard to blade thickness, and if the BTE thickness does vary a bit. their geometry is up to a point quite the same all around. But then again, the actual layout would be quite telling of its own:

Aogami Super
Gingami #3
YXR7
SG2
HAP 40
ZDP-189

I know that they do make some Shirogami #2, or did, but double bevel ones are Honyaki and I've never seen the geometry to those. They also make or did make it in single bevels, and also Aogami #2 single bevel, and VG-10 single bevel, all unusable samples if we'd want to benefit from the most extensive layout of different steels. So I'm counting these out but possibly we'd have a chance with the Honyaki W#2. And well YXR7 doesn't seem so readily available, but there's a few each year to hit BST so they're certainly in somewhat of a circulation, and a Matrix steel would be interesting into this comparison.

I've owned one AS, one SG2, one HAP. One of my lady friend bought a Ginsan on my advice and I see a lot of it in sharpening. It's as close as we could get from a single brand with almost identical geometries in between units, but there'd be a lot of thinning to do on a few to match the thinnest one I've seen.
 

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I was actually thinking of Sukenari when I made my previous post. My Sukenaris have fairly different geometries.
 
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