s30v woes

[Cliff Stamp]

I'm saying that you also have to take Crucible's data into consideration. You would rather ignore it altogether as biased.

A bias doesn't mean you ignore the data, it just means you are aware it isn't population representative, it represents the behavior of a subset. It generally comes from a carefully culled subset where test data is selected based on selling points or the data is subjected to a systematic error such as someone who lives in a really dry enviroment has a biased viewpoint on the requirement of corrosion resistance.

Neither of us has provided actual material data to support our views, thus you are demonstrating as much "faith" as me by your own definition.

I have provided you with significant materials data, these are not issues simply on S30V but general principles of metallurgy.

I haven't seen independent test data to verify your scientific knife testing, so why should I have faith in it?

There is no issue of faith with any data regardless of the source. You examine the data and see if it supports the conclusions. You then see if the predictions made by the conclusions hold true. You also look to other sources for contraditions or validation. This is why it takes time for ideas to generally be accepted because you look for others to confirm the results, expand on it, refine it and show the limitations. Note for example Swaim's work on rec.knives was independently checked by Talmadge and then again I verified the work. None of us proceeded on a viewpoint of faith, you always have the focus of a skeptic.

My first S30V blades were hardened at 950F and in some brief of testing I found the steel was slightly tougher at that temperature than at 600F.

During secondary hardening there is a massive drop in both impact toughness, corrosion resistance and edge stability (ability to hold a fine polished edge). There is materials data on all of those and it is based on the fact that during secondary hardening in high chromium steels there is a significant precipitation of carbides (chromium rich) and these tend to form at grain boundries. This is fundamental behavior of such steels, you will find it in any materials reference on high chromium steels. This precipitation both embrittles the steel and of course reduces the free chromium and thus reduces corrosion resistance. I also reduces edge stability which was shown by Landes.

However in the steels which are tempered significantly higher the chromium won't form chromium rich carbides and the carbides that form won't do so in grain boundries and thus the embrittlement isn't a concern with 3V for example. But you will again lose a significant amount of corrosion resistance vs a low temper as the chroimum has still precipitated. Note this isn't even a property specific to stainless, carbide precipitation during tempering is what causes the 500F embrittlement in low alloy tool steels for example.

It is also why Landes recommends quenching after the temper to minimize any precipitation see his very involved method for hardening steels like 13C26 for example which has three cold/temper/quench cycles.

I've not examined those teeth microscopically, but I know they break off quickly and when they do the blade is dull. That is true of many steels with that edge, but for some reason it's worse with S30V. With a 15 or 6 micron edge, the steel is great at edge holding.

This depends on what and how you are cutting more so that the steel. S30V as well isn't optomized for a fine polish as the carbide volume is too high and there is too much chromium carbide, steels like 13C26 are designed for a high polish. S30V is optomized for holding a thicker/coarser edge. Landes work shows in detail how the carbide size and volume influences edge stability which is supported by a significant volume of measurement including many P/M steels from different manufacturers. Wilson has also used S30V extensively (and S90 and S60V) with a coarse finish and the edge holding is very high when slicing, much better than if the edge was polished and he found this as a general principle which is why he sharpens his hunting knives to a coarse finish. This general principle was studied in detail by Swaim and company on rec.knives many years ago. It is also mentioned in Lee's book on sharpening which predates Swaim's commentary. CATRA also claims to have been aware of it for some time and there is recent data published by FuriTech on the same.

-Cliff

 

[Jerry Hossom]

Cliff, for a scientist to repeatedly misspell the word "optimize", a word fundamental to all experimental designs, is most peculiar. You repeatedly cite data, observations, and quotes of others without references, contextual setting, or evidence that such supporting references actually exist and are applicable in the context of the present discussion. Clearly matters discussed years ago by Swaim on the attributes of other steels than S30V are of questionable value.

You're correct, S30V wasn't designed for high polish, but that doesn't mean it can't be finished to a high polish. Several knifemakers mirror polish knives in S30V. That I think they're masochistic doesn't detract from the fact that even diamonds can be polished and tungsten carbide routinely machined.

As to what cuts what, how well and under what circumstances, I've been studying that subject myself for the past 25 or so years. Nonetheless, I've offered some observations. The readers are free to form their own judgements as to their value.

 

[JoHnYKwSt]

Thank you for your valuable insight, Jerry.

 

[Cliff Stamp]

You repeatedly cite data, observations, and quotes of others without references, contextual setting, or evidence that such supporting references actually exist and are applicable in the context of the present discussion.

As I noted previously I wrote a FAQ page which links to the background information in detail so the references can be looked up. You could also ask for them if you were not aware of the work done.

Clearly matters discussed years ago by Swaim on the attributes of other steels than S30V are of questionable value.

Cutting ability as a function of finish isn't specific to steels however if you really can't get past this then yes Wilson recently did extended slicing comparison with S30V vs other steels with a coarse finish and had the same results as Swaim did with steels he used which would expected because the same thing has been seen by many people in a wide variety of steels in the years since Swaim first discussed it on rec.knives. Landes even discusses it his book noting the difference between cutting with the blade moving perpendicular or lateral to the media, and he is well experienced with a number of P/M's and not just from Crucible. You would also expect the micro-teeth of S30V to be more stable than steels like ATS-34 because of the finer carbide size. It should again be better, not worse.

You're correct, S30V wasn't designed for high polish, but that doesn't mean it can't be finished to a high polish.

High is a relative term, the edge finish will be lower than steels with a finer carbide size. S30V is however better than most of the high carbide ingot stainless like 154CM, but worse than the low carbide stainless like 12C27 and most of the non-stainless tool steels like O1, 52100, 1095, etc. . It also won't hold the finish well as the edge stability is relatively low.

As for spelling, yes I don't always spell words correctly, that is why I didn't do an arts degree.

-Cliff

 

[english mark]

Good grief....this thread is turning into one of those threads where you need a degree in metallurgy just to read it....If it wasn't for Jerry laying it out in laymans terms i'd be baffled with bullshit.

 

[Jerry Hossom]

High is a relative term, the edge finish will be lower than steels with a finer carbide size. S30V is however better than most of the high carbide ingot stainless like 154CM, but worse than the low carbide stainless like 12C27 and most of the non-stainless tool steels like O1, 52100, 1095, etc. . It also won't hold the finish well as the edge stability is relatively low.

As for spelling, yes I don't always spell words correctly, that is why I didn't do an arts degree. -Cliff

S30V is MUCH more difficult than 154CM to finish in any way and to any level, blade or edge. That was my point, and having finished a whole bunch of blades in both steels I have some sense of that. Once properly finished, however, S30V holds the edge very well since the same mechanical issues that make it difficult to finish are those which retard the loss of finish. What may be unclear is that carbides can be polished and are when you polish a blade. Diamonds are polished and they are much harder than the carbides we are dealing with. Further, because it is relatively small in area, the edge is many times easier to polish than the blade as a whole.

Comparatively speaking, I think I can safely say that all stainless steels are more difficult than tool steels. In fact some low carbon stainess steels are very difficult to machine, so carbon is not the sole determining factor on that.

Also, the edge on S30V is quite stable, witness that the steel has been used in the Professional Knife Cutting competitions, where edge deformation or chipping is a disqualifying component. That is one of the reasons CPM-M4 is much used in that event. It has many of the same characteristics as S30V, only more of each.

I'm really not here to argue with you Cliff; I don't have the leisure to do that. I'm trying to convey to those interested what are some of my professional observations and experiences.

Parenthetically, I don't find unsupported references on your website any more convincing than they are here. Also, I think you'll find that AEB-L is also a good example of fine grain structure in a stainless knife steel, maybe even better than is 12C27. I've seen photomicrographs that seem to support that observation.

 

[Kohai999]

You KNOW when you start laying out observations based upon experience and knowledge that Cliff is going to come in and pull out whatever references(valid, or otherwise) he can to kick the chair out from under you. You know that Cliff has endless amounts of time to directly engage you, while you are actually trying to make a living, feed the family and all.

Directly engaging him is frustrating and pointless. I have been praying to all that is holy that I would run into him at some place like Ashokan where you have Cashen, Maragni, Baldwin, Zowada and others, to directly observe the interaction, but that has not happened yet. If only someday.

The way that you have laid out your thoughts and observations on S30v has been very helpful to me, and I am SURE many others that have questions.

Thank you.

Best Regards,

STeven Garsson

 

[flava]

For a few months my EDC was a Buck Mayo 172 (TNT) with S30V blade, heat treated by Bos. When I got the knife it was LNIB, but was far from sharp. I think it was a common problem with the first series of this model. No chippings or defects on the edge, just not properly sharpened.
As it needed reprofiling, the next time I visted my favorite knife shop I had it sharpened. They sharpened it using a coarse belt for reprofiling, then a worn belt, then a buffer for stropping (SP). The edge was brought to a more acute angle. It was not mirror polished but not rough either. It was hair popping sharp, and even though it was thin it never chipped and it held a long time too.
Based on my experience I'm convinced S30V is a great steel when heat treated and sharpened properly.

 

[tsdevanna]

Alot of good stuff here. I agree with alot of it and some of it I won't comment on. Things I do know that might help - Mr. Hossom did spend alot of time on "one" CPMS30V knife that did have a noticeable pit in the finshed blade - I now own it !

We have done thorough lab investigations on two chipped CPMS30V knives. One knife chipped due to insufficient HT and the other chipped because the owner of the knife resharpened the blade and "the chipped blade exhibited a shallow reaustenitized white layer on the blade edge.....the localized stress of the grinding burn at or near the surface could cause or contribute to chipping failure."

Here are three examples of CPMS30V knives that were less than desireable, one a definate steel problem, one a HT problem, and one a user problem. The user problem where the blade chipped - comparisons were made to a new unused blade from the factory.

We are aware of the problems and I can assure you we are paying attention and are being proactive. And yes Mr. Hossom, our available data and info suck so I can promise you this will also be addressed. However, try talking to a warm body about knife steels at that other place.

I have learned alot about knives and knife steels over the past seven years. I think Mr. Hossom has zeroed in on one of the major problems contributing to S30V chipping problems. Thanks for your insight Jerry.

Cliff - its OK to agree evry now and again - really !!

 

[searcher]

It seems what the knife maker and the steel company rep have concluded about S30V is that the problems with it stem from it's being "too good" as a knife steel and the same things that make it great for knives also make it hard to process into a knife. It looks like if things are done right, including proper heat treating, knife forming, and sharpening, you end up with an amazing edge that lasts nearly indefinitely. I, for one, am willing to pay a premium to get a knife with these properties from some one or some company that knows what the h*ll they are doing. I love my Spyderco Chinook and feel that in this case, at least, things were done right and everything came together to create that wonderful confluence of great design, excellent materials, and proper production that yields a really great knife. I am even willing to purchase and do whatever it takes to properly maintain a knife like that. For those that can't handle all these requirements, there is always 1095.

Obviously there needs to be an education effort on the part of the steel manufacturer to knife makers in the form of a "White Paper" explaining how to properly heat treat and produce knives with S30V to protect and even enhance (all) their reputations. It would entail telling the straight story on processing requirements, even at the risk of scaring off potential users. If it takes more grinding belts and time to process a knife, then that's what it takes. The alternative to not telling people about this is poor product quality, always a loser for everyone involved in the end.

As my first boss in engineering always said, "Heat treaters ('poor ones') will kill you." (As well as poor platers and some other secondary operation performer that escapes me at the moment). You often can't see their poor work and the only way to find out is through good quality control testing or from complaints due to failures in the field.

 

[Cobalt]

I'm really not here to argue with you Cliff; I don't have the leisure to do that. I'm trying to convey to those interested what are some of my professional observations and experiences.
.

Jerry, your wealth of kowledge is more than appreciated by those that understand and I wish more knowledgeable knifemakers would participate with their unbiased opinions. Frankly, I enjoy these types of discussions because they bring out a lot of information. I appreciate Cliffs input as well

Alot of good stuff here. I agree with alot of it and some of it I won't comment on. Things I do know that might help - Mr. Hossom did spend alot of time on "one" CPMS30V knife that did have a noticeable pit in the finshed blade - I now own it !

We have done thorough lab investigations on two chipped CPMS30V knives. One knife chipped due to insufficient HT and the other chipped because the owner of the knife resharpened the blade and "the chipped blade exhibited a shallow reaustenitized white layer on the blade edge.....the localized stress of the grinding burn at or near the surface could cause or contribute to chipping failure."

Here are three examples of CPMS30V knives that were less than desireable, one a definate steel problem, one a HT problem, and one a user problem. The user problem where the blade chipped - comparisons were made to a new unused blade from the factory.

!!

Has anyone actually done a comparison of optimal heat treats for S30V and other cpm steels? It seems that the problem lies there in most cases. Even Paul Bos does not seem to get it right.

 

[aberg]

kohai,
I am fairly new to this forum but not to knives. I have been playing with knives for 30+ years and the more I learn the more I realize how little I actually know, and I know even less about metallurgy. I also do not know you but judging from your favorite knife on your profile it is you who should STFU. Nice choice.

 

[Kohai999]

kohai,
I also do not know you but judging from your favorite knife on your profile it is you who should STFU. Nice choice.

Do you know anything about the Cold Steel Imperial Tanto?

If you did, you might not be so likely to limply try to shoot me down.

In that particular case, it is not just about the stainless damascus steel in a factory knife that was produced over 15 years ago, and was to the best of my (limited) knowledge the first factory production knife to marry stainless damascus with a stainless steel core, but also the first to use rayskin and traditional japanese cord(ito). Former ABS MS Dan Maragni had a great deal of influence, research and work on that knife.

I am not remotely a Lynn Thompson nut-hugger but that knife is truly revolutionary, and this is about as far OT as I am going on this thread.

Welcome to the Forums.

STeven Garsson

 

[Jerry Hossom]

Has anyone actually done a comparison of optimal heat treats for S30V and other cpm steels? It seems that the problem lies there in most cases. Even Paul Bos does not seem to get it right.

One thing I know for sure, Paul Bos knows how to heat treat this steel and he does get it right. I've never had faulty heat treating from him on any steel. He does meticulous quality control, calibrating his ovens regularly and doing hardness testing on EVERY custom blade he does, both after hardening and again after tempering to ensure the expected targets are met. (All the blades I get back from him have from two to four dimples from the Rockwell tester) While he is resident at the Buck facility and oversees their heat treating operation, he is not watching every batch to insure it's all done properly. Like anything under human control, every once in awhile someone blinks and something goes wrong.

However, there is a very clear reason why a great many knifemakers and a couple knife companies mark their blades as heat treated by Paul Bos. It means something. That's not to say others don't heat treat blades as well, and they do, but Paul does it well, always, and we know it. It's like a guaranty of heat treating excellence. It's why I ship steel all the way from Georgia to Idaho for heat treating.

Except for maybe a rare bad batch (and that can happen with any steel or any other product for that matter), the issues of heat treating S30V are not a problem except maybe for someone new to the steel. We are pretty certain what the heat treating schedule for S30V should be, because a lot of knifemakers have tried it and we are all free to change it if something's not right or we learn something new. There is nothing magic here, no secrets. As a whole the knifemaking industry is amazingly open and sharing of its technology and methods. (Visit a knife show sometime and ask a knifemaker how he did something. Nine times out of ten he'll not only tell you how he did it, he'll tell you about everything else he does if you're willing to listen. It's just the way we are.) If something is wrong, everyone knows about it in short order. We talk on the phone a lot, via email often, and on internet forums frequently. Unfortunately, we don't talk here as often as we probably should, because the price of dealing with the consequences is just too high for most.

In any case, finishing and sharpening issues are a new variable for most of us. Most steels sharpen like most other steels and are seldom troublesome if it's not just right. S30V makes us pay attention, and it has caused me to pay attention to other steels as well. ALL high alloy steels (maybe all knife steels) benefit from a properly shaped and finished edge. I think it's an area we ought to pay more attention to. I think there are other aspects of knife design, technology and construction that are candidates for re-evaluation as well. We need to be able to do that in a dialog that is respectful, civil and contructive. I hope we can.

 

[Cliff Stamp]

Once properly finished, however, S30V holds the edge very well since the same mechanical issues that make it difficult to finish are those which retard the loss of finish.

No it doesn't, Landes work shows this clearly. You are assuming that a high wear resistance is the critical factor in edge retention which is completely untrue. Makers such as Wilson have known this for years and noted it publically. In fact the properties that make a steel hard to hard to grind are exactly what make it unstable in fine edge profiles. Again, this is supported by published research grade data by Landes. It is one of the basic compromises in performance, you obtain wear resistance at the cost of edge stability.

If you take a steel like W1 at 65/66 HRC then you basically have optimal edge stability and initial sharpness. As you then add an alloy carbide like tungsten to get grades like 1.2562 or O7 then you give up these properties to enable a longer cutting lifetime either at a lower level of cutting ability or simply work with thicker and more obtuse profiles which are inhernetly more stable due to their cross section.

Such comments were made by Johnston on rec.knives over 10 years ago when he compared 1095 vs 154CM and found that 154CM has much lower initial sharpness and edge retention in acute edges. Jeff Clark also made many similar comments through the years on issues with heavy carbide steels in regards to optimal edge finish. Verhoeven notes the same issues when comparing 154CM vs AEB-L. Busse has also noted publically this is why he moved away from high carbide steels like D2 and into the shock steels for his larger knives because again wear resistance does not always equal edge retention it depends pretty much on all the materials properties; strength, toughness, fatigue strength, corrosion resistance, wear resistance, etc. Which one is critical depends on what is being cut and how.

What may be unclear is that carbides can be polished and are when you polish a blade. Diamonds are polished and they are much harder than the carbides we are dealing with.

When a piece of abrasive hits a carbide in the edge of a steel there is an action/reaction force between them which builds until the force is enough to cut the carbide or exceeds the force bonding the carbide to the surrounding steel. If there is little surrounding steel then the carbide will get ripped out. This has been known for a long time. I have seen references to it over 10 years ago on the wood working newsgoups and again Johnston was aware of it for longer than that and this was confirmed recently by Landes work. Buck's CATRA data also shows the same thing and it was made public many years ago. I recently performed some numerical analysis on that data to show the model I was using wasn't simply something that worked on my data and the results I was obtaining were consistent with independent data collected by a completely different lab group.

Comparatively speaking, I think I can safely say that all stainless steels are more difficult than tool steels. In fact some low carbon stainess steels are very difficult to machine, so carbon is not the sole determining factor on that.

There are many tool steels which are harder to grind than many stainless steels, D2 for example is a very difficult steel to machine/grind as are the high tungsten grades or at an extreme the carbide replacements like maxamet. Some of the low carbon stainless steels will work harden which impairs machining.

Also, the edge on S30V is quite stable, witness that the steel has been used in the Professional Knife Cutting competitions, where edge deformation or chipping is a disqualifying component.

The cutting volume is both very low and the materials very soft. Cashen has publically stated that you can pass the ABS tests with a mild steel blade so using similar grade tests to promote the superiority of steels isn't really much of a promotional tool. As for what steels are used, Schempp has noted sponsership influences steel selection and thus you again can't use that an an unbiased sample obviously. Even if this was not the case then the very most you could claim was that the steels which succeeded were superior to the steels which failed so what you have to do is find makers who are willing to say it would not be possible for them to perform the cutting with a specific steel.

Also, I think you'll find that AEB-L is also a good example of fine grain structure in a stainless knife steel, maybe even better than is 12C27.

AEB-L / 13C26 falls on the critical tie line and thus offers a higher hardness than 12C27 with lower corrosion resistance. 12C27 has a finer carbide size and smaller volume than 13C26 but the carbides in 13C26 are still very small, < 1 micron and the volume so low (a few percent) that it has basically optimal edge stability, along with other similar low alloy tool steels like 52100, O1, W1, etc. .

Has anyone actually done a comparison of optimal heat treats for S30V and other cpm steels?

Yes, Landes. His methods are very different from the mainstream heat treating in the cutlery industry as that comes basically from mass production concerns. For example you see common use of multiple high tempers to obtain a low retained austenite vs cold+low tempers which is more demanding. He is very experienced with many P/M's and not just from Crucible. Wilson's methods are very similar to Landes, just not as involved. Landes recipe for 13C26 for example includes an oil quench following by three cyles of cold/temper/water quench. You really can't expect that kind of detail in a production setting and quite frankly from a cost/gain perspective it likely isn't worth it anyway because the gains from repeated cycles are incremental.

-Cliff

 

[Kohai999]

This thread has been:

No it doesn't, Landes work shows this clearly. You are assuming that a high wear resistance is the critical factor in edge retention which is completely untrue. Makers such as Wilson have known this for years and noted it publically. In fact the properties that make a steel hard to hard to grind are exactly what make it unstable in fine edge profiles. Again, this is supported by published research grade data by Landes. It is one of the basic compromises in performance, you obtain wear resistance at the cost of edge stability.............



-Cliff

Best Regards,

STeven Garsson

 

[tom mayo]

I am really confused!!!!!!!!

 

[EDCeeker]

STeven,

You may not care for Cliff's POV, manner, or whatever, but some of the rest of us are enjoying the discussion. If you have nothing more to contribute than personal attacks against Cliff, perhaps you would be so kind as to absent yourself from the discussion?

Thanks.

 

[Kohai999]

STeven,

You may not care for Cliff's POV, manner, or whatever, but some of the rest of us are enjoying the discussion. If you have nothing more to contribute than personal attacks against Cliff, perhaps you would be so kind as to absent yourself from the discussion?

Thanks.

Not during your lifetime, or limited stay on BladeForums, whichever may come first.

If you do a search, you will see where Jerry puts up some very credible firsthand information, and Cliff comes out of Left Newfoundland.

ESAS,

STeven Garsson

 

[Jerry Hossom]

Who is Landes?

Are you seriously telling me that D2 is more difficult to grind than S30V? How would you know? How many blades have you ground in each steel? I've ground dozens of blades in D2 and hundreds in S30V.

Are you also suggesting that Crucible sponsors/bribes competitors to use their steels in the Professional Cutting Competition? That's nonsense, if not libelous. Schemp is using CPM-3V, which would not be my choice even though it is generally my favorite steel. What steel would you suggest using?

The Professional Cutting competition is completely different from the ABS Journeyman Smith test. The only thing they have in common is chopping a 2 x 4 which is just one small part of each exercise, and while a mild steel blade might bend to 90 degrees easily enough it makes a lousy 2 x 4 chopper and would most certainly fail the edge deformation elements of both activities. I seriously doubt Cashen would have suggested otherwise.

Cliif, you are an extremely unpleasant person and your defamatory comments are precisely why knifemakers generally avoid these forums. It just isn't worth the bother. Further, you insist on throwing around unsupported references and spout a lot of nonsense that has no bearing in reality. Unfortunately many of the people who read your posts don't know whether what you say is credible or not so it is often accepted at face value, which simply promulgates the misinformation. In fact if people actually read each of your sentences carefully, they would see that many of them don't make any sense at all or are dependent on hearsay or your personal opinion.

EDCeeker, I think you'll find that most knifemakers are happy to absent themselves from the "discussion", such as it is, as well.