I Tested the Edge Retention of 48 Steels

[Jimboss]

So who wants to donate a Denka, Kato, Fujiyama etc to @Larrin for testing

I assume this is somewhat tongue in cheek but wouldn't testing individual knives give results that are not comparable to the previous results due to introduction of many different variables associated with each specific knife? I agree it would be great to have tests done to compare individual knife makes to each other for different metrics, but in terms of gathering data for analysis about steel type this doesn't seem that useful.

 

[_THS_]

This wasn’t a study of heat treating like some of you are trying to make it in to.

Wear resistance is controlled mostly by carbides and hardness which is controlled by the chemical composition of the steel. Most of these test coupons were heat treated using the standard recommended heat treatments or something that would fit the test better.

There needs to be some follow up testing to determine if we can get some separation with optimum heat treats.

This was some very good testing but I’m afraid some of you lack the intelligence to learn anything from it.

I highly recommend that those of you with the biggest mouths do your own testing and then let us sit back and criticize your work.

Hoss

Would be much better for the test itself to be discussed and clarified instead of being putted on a stand to be untouchable. If someone have a doubt on why some steels are hardened in a way, why not explain it instead of saying we lack the intelligence for understanding? You're taking a scientific test religiously, wich is plainly wrong

 

[Bolek]

If my understanding is correct we need big carbides for edge retention but small ones to have a sharp edge.

 

[Larrin]

Would be much better for the test itself to be discussed and clarified instead of being putted on a stand to be untouchable. If someone have a doubt on why some steels are hardened in a way, why not explain it instead of saying we lack the intelligence for understanding? You're taking a scientific test religiously, wich is plainly wrong

Constructive criticism and discussion are always appreciated. Sometimes what happens is instead there is anger, ridicule, dismissive statements, or “arguing” rather than discussion. In my experience, once an internet discussion has taken a negative turn further productive discussion becomes very difficult, and further negativity is more likely to result. Sometimes the negativity is very obvious to some people (see pushback from some people in this thread about the attitude of some other commenters) while appearing harmless to others. Studies show that when “trolling” comments have appeared in an online discussion, more such comments are more likely to follow. See: Anyone Can Become a Troll

For me personally, when I feel that questions are presented only to win an argument rather than to discuss I would rather avoid further discussion altogether rather than try to “save the thread” because the win-loss record on such attempts is very poor. Sometimes this also requires ignoring questions from people who are more well-meaning because it provides more fodder for the trolls. Once I have given in to my baser instincts and start arguing with the critics, I only add fuel to the fire and diminish my own reputation. Perhaps some of those times I mis-perceived the intentions of the person driving me to argue. Regardless, leaving a conversation is a better avenue, at least for me. Sometimes criticism, even from trolls, may provide food for thought or lead to experiments to see whether experimental assumptions are accurate or if results may be different with certain variables. Even when that is the case, arguing about it in a negative tone is not productive.

 

[The Edge]

Would be much better for the test itself to be discussed and clarified instead of being putted on a stand to be untouchable. If someone have a doubt on why some steels are hardened in a way, why not explain it instead of saying we lack the intelligence for understanding? You're taking a scientific test religiously, wich is plainly wrong

What about his experiment is in question? I gather you want to know why he heat treated the steel the way he did, but is that even a valid question. The fact is, he told you how he shaped the pieces, the tolerances, the heat treating recipe for each steel he used, the method of how he tested, and finally the results. If this brings up more questions like, "I wonder how this steel would perform heat treated a different way." Then I think this experiment did its job.

I, in no way, think this was meant to be a table of results that showed the absolute best capability in each steel. Instead we have a baseline that we can use to compare future values. Larrin took a great amount of time and money to give us raw data. We know more by having it. Does it answer all your questions? Nope. But if your interest is peaked, please stop questioning him, rather than thinking of new experiments that can start filling in some of the holes.

 

[esoo]

For a *free* resource, that article is beyond belief, as is much of Larrin's site for those of us that are non-knife makers.

When designing a test, decisions needed to be made - like how to heat treat the steel. Those choices may seem arbitrary, but they needed to be made to make the test move along. Could Larrin have chosen a different procedure for each steel? Yes. Could those other procedures have ended up with better edge retention? Possibly.

But in the same mind that Dalman isn't going to release his preferred heat treats to Larrin, is Larrin going to give out all his best heat treat knowledge in a free paper? I think not.

You want to find the best heat treat for a steel for edge retention? Pay Larrin (or someone else) to do the work.

In the meantime, he's given us a resource that is great for discussion. Is it what we all want - the comprehensive guide of edge retention from every smith's heat treat of every steel? No. But since we paid zero, I'm pretty damn impressed with what I got.

 

[_THS_]

What about his experiment is in question? I gather you want to know why he heat treated the steel the way he did, but is that even a valid question. The fact is, he told you how he shaped the pieces, the tolerances, the heat treating recipe for each steel he used, the method of how he tested, and finally the results. If this brings up more questions like, "I wonder how this steel would perform heat treated a different way." Then I think this experiment did its job.

I, in no way, think this was meant to be a table of results that showed the absolute best capability in each steel. Instead we have a baseline that we can use to compare future values. Larrin took a great amount of time and money to give us raw data. We know more by having it. Does it answer all your questions? Nope. But if your interest is peaked, please stop questioning him, rather than thinking of new experiments that can start filling in some of the holes.

I wouldn't be able to discuss whether the OP is right or not on his heat treatment as I have no idea whatsoever on the topic, but once you separated some sterile trolling from the serious questions, you can notice that 2 quite famous and renowned makers had the same question: why some steels have been treated that, apparently or at least for them, weird or unusual way. Now, if the OP has no intention in explaining here, that's understandable, but other people asserting that you either agree or you're not intelligent enough is quite annoying since as far as I can tell, the article try to be as scientific as possible. Now, having said my knowledge of metallurgy isn't great, my question is: is it the best choice to heat treat all steels at the same hardness, even knowing some can perform arguably better at different hardness?

 

[Bert2368]

Question for Larin:

Could you ballpark what an asking price might be if you, in your professional capacity, were to test a single heat treat sample provided to you under the regime used here?

Not fabricating/heat treating the test piece. Work to include sharpening a sample to the spec used in previous testing, running it through the card stock test (testing 3X as for the listed samples?), collecting the data and providing documentation.

I do understand why many would not care to disclose their heat treat procedures and that some would not care to publicize their results from such tests. But I suspect, for their own information, many who are driven to pursue the craft still would want to know how their results stacked up.

In the case some experienced, competent people ARE willing to disclose HT procedure and agreed to open publication of results, be they good, bad or indistinguishable- Are you willing to continue this experiment and release such data gratis? To what extent COULD you continue the testing without your wife taking a sledge hammer to the machine...

 

[Larrin]

Question for Larin:

Could you ballpark what an asking price might be if you, in your professional capacity, were to test a single heat treat sample provided to you under the regime used here?

Not fabricating/heat treating the test piece. Work to include sharpening a sample to the spec used in previous testing, running it through the card stock test (testing 3X as for the listed samples?), collecting the data and providing documentation.

I do understand why many would not care to disclose their heat treat procedures and that some would not care to publicize their results from such tests. But I suspect, for their own information, many who are driven to pursue the craft still would want to know how their results stacked up.

I'm still considering costs of testing. It will be $50 or less but I haven't decided how much less.

Knifemakers who do not disclose the heat treatment will not have their knives tested at this time as my interest is in research and not as being a testing service. The CATRA company tests knives for $75 or so for them.

 

[Bert2368]

Sorry, was editing my question while you replied.

 

[Ruso]

@Larrin I might not see it, but I could not find results for xhp. Is it under different name or it was not tested? If the latter, what is your ballpark prediction for XHP?

 

[Larrin]

@Larrin I might not see it, but I could not find results for xhp. Is it under different name or it was not tested? If the latter, what is your ballpark prediction for XHP?

An XHP blank was produced but warped in heat treatment and the warp was missed until it was already ruined. It is on the list to be tested later. It would be expected to be around 540mm at 61 Rc.

 

[DevinT]

I apologize for being so offensive.

@RDalman and @bryan03 are highly respected knife makers who make excellent knives.

I don’t think this is the best test for simple carbon and low alloy steels because it uses far too aggressive media. We need to devise a better test for all of the most popular kitchen knife steels.

I think I’ll build a rope cutting machine so that we can tease out some of the better heat treatments.

In order to find the optimum heat treat and working hardness of a steel, the test would be nearly as big as this one but only involve one alloy. It would require working with several smiths/knife makers.

Heat treating is the most mysterious part of a knife because you can’t see it and it is very hard to measure, there are too many variables.

Even if we did thousands of tests with thousands of alloys with thousands of different heat treatments from thousands of accomplished knife makers, we would never come to any conclusion.

Peace out,

Hoss

 

[esoo]

I think I’ll build a rope cutting machine so that we can tease out some of the better heat treatments.

Take that rope and soak it in different pH solutions to figure out how acidity of the product being cut affects edge retention.

It really is a never ending pit of testing....

 

[Deadboxhero]

Those makers were also asked if they
would like to share their thoughts on heat treatment in detail. They declined, but gave kudos.

So, it's not an open, two-way discussion or even anything to debate.
So, it's not something YOU should be hung up on.

Hardness does increase the wear resistance but it doesn't change the types of Carbide particles that have different hardnesses inside the the steel.
The hardest carbide (Vanadium carbide) is fixed to the steels ingredients.

So heat treatment cannot add elements to the steel.

You can read in the article that 15V cut more than zdp189 despite the zdp189 being harder.

Why?

The answers are in that article, I highly recommend you giving it another read if you have already.

I wouldn't be able to discuss whether the OP is right or not on his heat treatment as I have no idea whatsoever on the topic, but once you separated some sterile trolling from the serious questions, you can notice that 2 quite famous and renowned makers had the same question: why some steels have been treated that, apparently or at least for them, weird or unusual way. Now, if the OP has no intention in explaining here, that's understandable, but other people asserting that you either agree or you're not intelligent enough is quite annoying since as far as I can tell, the article try to be as scientific as possible. Now, having said my knowledge of metallurgy isn't great, my question is: is it the best choice to heat treat all steels at the same hardness, even knowing some can perform arguably better at different hardness?

 

[user 29468]

Those makers were also asked if they
would like to share their thoughts on heat treatment in detail. They declined, but gave kudos.

?

i do not Understand the way this Thread is taking...


all tests on knife’s steel is interesting, and i think it’s legitimate to ask questions, if it’s posted publicly, and Mostly if some points seems unusual with our practices. you are talking about science , it’s not a dogma .

i do not have a PhD , i only have few low alloy steel blades quenched by myself , so i do not wonder everything ( to be honest, nothing with PM steel or thing like that, by lack of interest ) , but i think It’s enought to no been called troll.

 

[Larrin]

For The moment I only have questions :
why cryo for all steel ? i know nothing about SS but 1.2519 ? 1.2442 ? super blue ?

Cryo was performed for all steels to keep the heat treatment process consistent across all steels. It is common for knifemakers working with low alloy steel to claim that those steels do not "benefit" from cryo in some way or that cryo has no effect on them. This is of course false and based on a misunderstanding of what cryo does (and doesn't do) and how it works. I have several articles on cryo where you can learn more. If I hadn't used cryo on the low alloy steel then I would be fielding questions about why I didn't use it and whether that affected the low scores of the low alloy steels.

Why austenize 2442 and 2519 at 800 and the other 830 ?

The higher chromium content of 1.2519 means higher austenitizing temperatures are necessary for a similar amount of carbon in solution. You can read more in the following articles:
https://knifesteelnerds.com/2019/01/28/history-and-properties-of-52100-steel/https://knifesteelnerds.com/2019/05/13/how-to-heat-treat-52100/https://knifesteelnerds.com/2020/02/17/ranking-toughness-of-forging-knife-steels/

why temper 149 and the other 200° ?

To achieve the desired hardness. Since 1.2442 and 1.2519 ended up within 0.3 Rc it appears I was successful.

10 and 15 minute soaking, what thickness at edge before quench ?

Again because of chromium content.

 

[DevinT]

I had forgotten how good those articles are. It was good for me to reread them.

Hoss

 

[Kippington]

Cheers Larrin, for all the work gone into all the detailed and concise information you've put out for free. I continue to learn more with each new article, and this one was a doozy.
I personally find it difficult to think of any additional questions*, as you've covered everything I can think of in previous heat treating articles already.

Also, my personal experience with many of the steels in your study have echoed your results, which is nice because thanks to you I can now slot the untried steels into the picture with ease, plus my confirmation bias is brimming with pride!

Thanks again!

* Did you quench in the light of a blood moon?

 

[Luftmensch]

Well done! I know how long it can take to do labour intensive experiments. What a gift to the collection of freely available knowledge.

Constructive criticism and discussion are always appreciated.

With regards to the low-alloy steels, I can try :

I don’t think this is the best test for simple carbon and low alloy steels because it uses far too aggressive media. We need to devise a better test for all of the most popular kitchen knife steels.

I don't have a feel for how sensitive CATRA testing is. I am just taking the data for granted. From @Larrin's comment in the article, i assume testing variation is low (e.g. +/- 5mm TCC??):

Each knife was tested three times on the CATRA edge retention tester and the results averaged. When one of the tests looked substantially different than the other two I performed a fourth test as a tiebreaker. In general the results between re-tests were pretty consistent but there were cases when an individual test would be worse than the others.

As a sanity check, one thing you guys could do, with the low-alloy steel data, is analyse the variance of the results. If you take the measurements for each low-alloy steel and subtract their mean, you would have a collection of zero-centred measurements. Now if you take the standard deviation across all this zero-centred data, you will get some idea of variation in the testing.

If the variation for the low-alloy steel data is super low (e.g. 1mm TCC), you can probably trust the 'ranking' of steels (even if this isn't the point). A more sensitive test would be unnecessary, unless you want to stretch the scale.

If the variation is something like 10mm TCC, the general trend will be correct but you might not want to trust the exact 'ranking' for similar results. For example, A2 and O1 are well separated - it is likely that A2 has something like 20% better edge retention. On the other-hand, 1.2519 and 1095 are very close. In this (variation) scenario, all you could confidently say is that they perform about the same and the ranking may not be correct (the very slight advantage to 1.2519). If you wanted more precision, you may want to devise a more sensitive test.



Other rambling thoughts:

I may try to use rope or cardboard in the CATRA machine in the future to test this further.

I'd be interested in plain cardboard (it is a cheap and easy test material). Again... I don't have a feel for how CATRA testing scales. Would plain cardboard increase the TCC 100x? 10x? I suspect it is less than 10? That might 'stretch the scale' for the low-alloy steels.

If it is easy to exchange the steel cylinder at the top of the machine, you could also consider lowering the cutting force.


All in all... nice work

 

[Luftmensch]

It's really cool to see some measurable values from standardized testing like this, regardless of the quibbles some people may have. May be of more interest over at Bladeforums shop talk since there is more discussion of steels with respect to knife usage. KKF has a very Japanese knife-centric audience, and for Japanese kitchen cutlery, it's very unlikely many of the favored makers/bladesmiths/shops will expand their steel offerings outside the steels they are used to forging or using especially considering how little spread in the CATRA values are seen between the low alloy carbon steels typically used.

Yeah... just to make it explicit to readers here... The fact that @Larrin makes insightful posts here doesn't mean his immediate interest is kitchen knives. Larrin participates in (at least):

• BladeForums.com
• Spyderco Forums
• r/knives

So he is likely to have a broader view on what use-cases various steels might face; at least, compared to the general standards of kitchen cutlery!

 

[Larrin]

I like kitchen knives the best. But some of my kitchen knife readers are lacking in imagination when it comes to what is relevant for kitchen knives. Or at least that is my conclusion when they say that certain steels or topics are not relevant to kitchen knives. I worked very hard to obtain certain Japanese produced steels that almost no one uses in the USA, for example. But not everything will be about kitchen knives.

 

[Kippington]

It's almost like kitchen knives are related to other cutting tools...

 

[RDalman]

I will say it without imagination. My opinion is that using that catra chart as comparison for choosing steel alloy for kitchen knives is a potentially misleading route. Many of the heat treatments used I have had very poor experience with. And I think the cutting media is problematic as a reference to kitchen knives.

 

[Larrin]

I will say it without imagination. My opinion is that using that catra chart as comparison for choosing steel alloy for kitchen knives is a potentially misleading route. Many of the heat treatments used I have had very poor experience with. And I think the cutting media is problematic as a reference to kitchen knives.

Relying on anecdotal experience is very dangerous when it comes to learning broader principles about how the world works.

 

[RDalman]

Relying on anecdotal experience is very dangerous when it comes to learning broader principles about how the world works.

Enough of the arrogance for me. Peace out.

 

[Larrin]

Enough of the arrogance for me. Peace out.

https://www.merriam-webster.com/dictionary/irony

 

[madelinez]

Edit: Not relevant

 

[DevinT]

I will say it without imagination. My opinion is that using that catra chart as comparison for choosing steel alloy for kitchen knives is a potentially misleading route. Many of the heat treatments used I have had very poor experience with. And I think the cutting media is problematic as a reference to kitchen knives.

You should make test coupons from the steels that you’ve seen the most improvement with your advanced heat treat. Even with the aggressive media being cut/tested, there will be a separation from the standard heat treat. Then we can find out how much of a measurable difference there is.

Hoss

 

[Iggy]

@DevinT @Larrin

Ok... I think every material scientist (btw... am one by myself... polymers and composites, 8 years of experience, worked at a material science institute here in Germany before going to the industry, multiple publications and leading international R&D projects in the field of material development) will agree, that standardized test procedures are one of the key aspects when doing material analysis for comparison (of course besides other factors like a statistically approach the control of defined influence parameters).

But... and I think here lies the key, were you and some of the knife makers here (as well as myself that said) differ...

The use/load case is one of the, may be THE most significant aspect in material testing. The question is... are CATRA or rope cutting tests simulating the real life load cases that occur when using a kitchen knife? For an Outdoorblade or heavy duty folder, that is mostly used for cardboard cutting or wood etc.... maybe, yes.

For kitchen knives? I really doubt it...

In my opinion, kitchen knives are mostly loaded with an impact and bending/shear load case, f.e. in combination with corrosion. The CATRA test (as well as rope cutting when you pull/push cut) is not sufficient to simulate these load cases. This is why the results "from the experience of the real world" and your CATRA based results seem to differ quite a bit.

Maybe it would be more suitable (and scientifically more "clean") to simulate the load cases, that occur in kitchen knives, and test and compare them before transferring results from another only remotely connected test scenario to kitchen knives. Don't you think?

With FEM simulation etc., you could for example simulate the critical load cases with different cutting techniques (f.e. chopping with straight impact on the board or rock chop with a certain amount of orthogonal force etc.). For most of these cases, standardized test methods exist.

Right now, I find the hypothesis to transfer CATRA results to kitchen knives quite (let's say) uncertain and not really "scientific" to be honest.
Would look forward to see how the results of the tests mentioned above would differ.

All the best,
Simon