I Tested the Edge Retention of 48 Steels

Larrin said:
Thanks everybody. I don't think I've changed history but I do enjoy testing knives and steel.
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I am grateful for your hard work, sacrifice, and hard-core information. You've profiled so many parameters which go
into cutting/slicing efficiency and effective length of a working edge.
It makes me happy that I just purchased a nice folder in S90V...it should serve me well.
 
Pretty much confirmed why I'm a fan of AEB-L and close equivalents. For my contexts of use, I prioritize ease of sharpening and toughness over resistance to abrasive wear, and being a fairly tough stainless that holds an edge respectably for its class and can be sharpened effectively on almost anything, it ticks all of the boxes for me. Other contexts obviously have different demands, though.

Incredible work, as always. Y'all outdid yourselves on this.
 
sgt1372 said:
I'm not a steel geek and a lot of the info went and still remains over my head but I appreciate the amount of effort that went into this study.

Not to oversimplify the results but, as a layman, this is what I get out of the report, based on the main chart, which compares edge retention (# of cards cut) vs hardness;

The steels with the greatest edge retention ability (that I am most familiar with as a knife collector/buyer), grouped in order from high to low, are:

1) S90V (about 775 TCC) and 10V (which varied from about 725-800 TCC based on hardness from about 59-65)
2) K390/S110V/ZDP189 (about 725 TCC).......

What surprised me (just as a knife but not steel geek) was:

1) How much better S90V did than K390/S110V/ZDP189 and M390/20V.
2) How well S30V did and how important the heat treatment was to its performance; still below the "premium steels above" but not far behind for a steel that is often overlooked/maligned (based on what I've read).
3) The fact that M4/Elmax/S45VN did not outperform S30V, even at it lowest hardness level.
4) How poorly LC200N did when compared to the other steels; it obviously it gives up a great deal in edge retention in lieu of corrosion resistance.

What didn't surprise me was how poorly (relatively speaking) that D2/CPM154/VG10/440C and O1 did in the testing. Fortunately, they usually come w/lower priced knives and are easy to sharpen by hand; not so the harder premium steels......

I guess it also shouldn't be a surprise that the degree of edge retention varied directly w/the hardness of the steel but unfortunately the degree of hardness of the steel used in knives often is not provided to potential buyers but, when it is, obviously the hard steel would be preferred, whenever edge retention of the knife is considered important.


In this sense, S30V comes out the winner to me for a relatively low cost common steel, especially if you can find it at the highest level of hardness (around 64.5) with an equal edge retention results (about 624 TCC) as compared with M390/20CV, which is also quite surprising and also nice to know since I own so many ZTs/Spydercos and other knives that use S30V.

Thanks for this report!
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The key point here is the hardness, or lack thereof in so many retail knives. I submit that very little say spyderco s30V is above 61, let alone 62-64.5 HRC. Seems based on the PMI chart that spyderco s30V hits around 60.3, whereas Benchmade hits 57-60 but is said to cut test better (SSS). It would seem that all the steels leave performance on the table, and the table top is the heat treat.
 
Zeunerite said:
What sort of magic does LC200n use to perform so well in rope cutting tests despite the relatively poor catra results?
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The rope cutting tests I have seen are for different knives not identical knives in the same steel. So presumably if LC200N did well it would be from better edge geometry and/or hardness.
 
For wear and corrosion resistance, 204P still appears to be a slight step-up from S30V. I found S35V and S45VN to be surprising steps down from S30V. I would much prefer S30V to S35V and S45VN based on these results. I still don't understand why CRK won't use S30V over the other two. The data also seems to reveal a clear gem amongst the contenders: S110V. This steel really deserves more attention from knife makers. S110V out-cuts 204P by a good bit, and comparing to S90V, it's easier to sharpen, has way more corrosion resistance, has almost the same edge retention and is a tougher steel.
 
Mrs_Esterhouse said:
The data also seems to reveal a clear gem amongst the contenders: S110V. This steel really deserves more attention from knife makers. S110V out-cuts 204P by a good bit, and comparing to S90V, it's easier to sharpen, has way more corrosion resistance, has almost the same edge retention and is a tougher steel.
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And yet, if you read both our own, and Spyderco's independently owned forum, you'll come across many more issues reported from users with S110V vs. S90V blades. I'd be interested in hearing the opinions of Larrin and Shawn regarding this anecdotal evidence.
 
It gets interesting when you factor the charpy impact toughness results to put things in perspective.

The s35vn looks about ~520mm TCC at 61.2rc and the toughness was ~9lbs on charpy at about the same hardness

The S30v was ~595mm TCC at 61.9rc but was ~6lbs on the charpy despite softer at ~60.3rc on the Charpy specimen.

Percentage difference between 520mm and 595mm is 13.4% difference on CATRA

Percentage difference between 6lbs and 9lbs is 40% difference on Charpy Impact.

Not claiming one is better than the other just thought I'd share some food for thought and perspective.

If we remember the original reason for moving to S35VN was not for more edge holding but for increased toughness, corrison and ease of grinding/sharpening to balance the steel out more than S30v.

I'm enjoying what folks are gathering from all this information.

Excited to see more folks share their thoughts.

Thanks!

Mrs_Esterhouse said:
For wear and corrosion resistance, 204P still appears to be a slight step-up from S30V. I found S35V and S45VN to be surprising steps down from S30V. I would much prefer S30V to S35V and S45VN based on these results. I still don't understand why CRK won't use S30V over the other two. The data also seems to reveal a clear gem amongst the contenders: S110V. This steel really deserves more attention from knife makers. S110V out-cuts 204P by a good bit, and comparing to S90V, it's easier to sharpen, has way more corrosion resistance, has almost the same edge retention and is a tougher steel.
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Like Phil Wilson and many others say.

It's the sharpening that is one of the biggest variables between peoples anecdotal experiences.

Blues said:
And yet, if you read both our own, and Spyderco's independently owned forum, you'll come across many more issues reported from users with S110V vs. S90V blades. I'd be interested in hearing the opinions of Larrin and Shawn regarding this anecdotal evidence.
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This is an awesome study, and I don't want to throw cold water on it. But, it is important to remember that there are credible data out there that come to different results.

For example, Crucible's own characterization of S30V vs S35VN does not show a 50 percent toughness advantage for S35VN. It does not show a 14.4 percent advantage in wear resistance for S30V. Nothing even close.

And it shows that CPM M4 has a big wear resistance advantage over S30V, which is quite different from what Larrin and Dead's data show.

PDFs\DataSheets2010\dsS35VNrev12010.pdf


Bohler's tests show different toughness data, too.

This study by Larrin and Dead is pretty awesome, especially because it does a good job of addressing confounding variables. And I also like it because it tends to make sense. But there remain some data that don't fit in with other work. And we saw from the introduction of S30V steel that very small changes in the heat treat can lead to large differences in the final edge.

I also find that my own personal experience is sometimes quite different that the data here. For example, I have a custom 440C chef's knife with aggressive geometry and a Super Blue chef's knife at 64 Rc that has similar geometry. This study shows 440C has a roughly 36 percent advantage in wear resistance over Super Blue run harder. But in my use of these knives, Super Blue holds its edge a lot longer.

Still, a great study. Glad it's a sticky. It's a standard of evidence that we can compare to other work.
 
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T Twindog

It's always nice to get independent steel data in addition rather than only information from just the manufacturer that sells to other industries than solely knives.

If we look closer at that data sheet we can see they are using "relative catra % to 440C" in a percentage and don't have data about Total Cards Cut in Millimeters and Hardness,
Nor do they provide any information about edge angle, sharpeness, what abrasive was used to shape the edge and if they were grinding with water cooling, etc.

Anecdotal experience and evidence is never obsolete but it's nice to see how things stack in a more controlled environment since the list of variables is VAST as to why something out cut something else in the wild.

I'm a big fan of super blue as well but I Do have some 440C at 64rc with a custom protocol that is also interesting.

That's another thing about data sheets, they don't show you all the possible ranges of where the steel can go. According to the 440C data sheet there is no 64rc range.



Twindog said:
This is an awesome study, and I don't want to throw cold water on it. But, it is important to remember that there are credible data out there that come to different results.

For example, Crucible's own characterization of S30V vs S35VN does not show a 50 percent toughness advantage for S35VN. It does not show a 14.4 percent advantage in wear resistance for S30V. Nothing even close.

And it shows that CPM M4 has a big wear resistance advantage over S30V, which is quite different from what Larrin and Dead's data show.

PDFs\DataSheets2010\dsS35VNrev12010.pdf


Bohler's tests show different toughness data, too.

This study by Larrin and Dead is pretty awesome, especially because it does a good job of addressing confounding variables. And I also like it because it tends to make sense. But there remain some data that don't fit in with other work. And we saw from the introduction of S30V steel that very small changes in the heat treat can lead to large differences in the final edge.

I also find that my own personal experience is sometimes quite different that the data here. For example, I have a custom 440C chef's knife with aggressive geometry and a Super Blue chef's knife at 64 Rc that has similar geometry. This study shows 440C has a roughly 36 percent advantage in wear resistance over Super Blue run harder. But in my use of these knives, Super Blue holds its edge a lot longer.

Still, a great study. Glad it's a sticky. It's a standard of evidence that we can compare to other work.
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DeadboxHero said:
T Twindog

It's always nice to get independent steel data in addition rather than only information from just the manufacturer that sells to other industries than solely knives.

If we look closer at that data sheet we can see they are using "relative catra % to 440C" in a percentage and don't have data about Total Cards Cut in Millimeters and Hardness,
Nor do they provide any information about edge angle, sharpeness, what abrasive was used to shape the edge and if they were grinding with water cooling, etc.

Anecdotal experience and evidence is never obsolete but it's nice to see how things stack in a more controlled environment since the list of variables is VAST as to why something out cut something else in the wild.

I'm a big fan of super blue as well but I Do have some 440C at 64rc with a custom protocol that is also interesting.

That's another thing about data sheets, they don't show you all the possible ranges of where the steel can go. According to the 440C data sheet there is no 64rc range.
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Absolutely, Shawn. I agree with your points. Nothing I said is a criticism of your study. Larrin's and your study is the best I've seen on knife-steel performance. And Larrin's investment in time and money and expertise to create this epic thread is better than anything similar that I've seen on the forum.

But there are some curious findings that it would be interesting to sort out.

Crucible designed S35VN to be 15-20 percent tougher than S30V, with no loss of edge wear. Your study found a much larger, 50 percent increase in toughness and a significant loss in edge wear. As you rightly point out, Crucible didn't provide any of the basic data behind its representations, but it's difficult for me to believe that Crucible would do sloppy research or be that clueless about two steels it designed for the knife industry.

"CPM S35VN was designed to offer a 15-20% improvement in toughness over CPM S30V without any loss of wear resistance or corrosion resistance. It is also easier to machine and polish than CPM S30V."​


And in comparing its own S30V to its own CPM M-4, Crucible found M4 to be much better at edge wear. Your study found S30V to be better.

Did Crucible's engineers screw up their tests? Did they use different heat treats or edge angles or sharpening techniques that explain the differences? Or can we just not trust anything the steel companies say? Who knows? Fun to discuss.

Thanks for your amazing work.
 
In the S35VN datasheet they say the CATRA result is an estimate based on market feedback. In other words, they didn't test it. It strains reason how dropping the vanadium and carbon content and replacing it with 0.5% Nb would lead to equal edge retention.

Crucible hasn't provided any edge retention numbers for CPM-M4, only a value on a bar chart for wear resistance with no information about hardness differences, what test was used to derive the values, or even if a test was performed at all or whether it is an estimate.
 
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