Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope

Phil and SG, thanks for the toughness reports. M4 has been around a while, but it is still one of the best all around blade steels we have.
 
sodak said:
That really (pleasantly) surprises me. I wouldn't have guessed that level of performance, but it is thin and hard. Darren seems to be raising the bar on lots of steels, love reading about it!
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S35VN has been around for awhile now, long enough for the Custom guys to work on their HT Protocols. :)
 
Surfingringo said:
High mamba, I have been using that knife for the last 6 months or so. As Phil said that one has seen some fairly heavy real world use. I intentionally did a lot of pushcuts through large rib bones on large fish. Many of these cuts involved me putting my hand on the spine and using a lot of body weight. I wouldn't say that I was trying to damage it but I wasn't far from it. I definitely haven't cut the knife any slack. Through 6-8 months of that use on an almost daily basis I haven't been able to hurt it. No chips, no rolls...nothing. That has been my experience.

Fwiw, I used it alongside some production knives in s30v with thicker edge geometry and I did see some noticeable (though minor) chipping in the s30v in the same work. I have also experienced some of the same damage using s90v. Those are real observations, but I'm not the most scientific tester out there so don't take it as gospel or anything. :).
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And here we are.
Your feedback is precious and confirms what I've said here many many times: the importance of edge stability. You made reference to S30V and S90V production blades, I could add Elmax and M390 ones (Always production). All have in common underhardening, in the wrong understanding that this will help resistance to chipping (in applications not involving chopping, as Phil correctly said), but it actually goes the opposite way.
Now, thanks to you I've one more confirmation.
 
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Phil Wilson said:
.....CPM M4 overall is not the best grade for the fishing/saltwater/high/high humidity application but it does serve to put another point on the curve and some real life use in the field. Phil
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Phil, I have a Bohler Sheet (I can send it to you if you wish) that states that S690 (their CPM-M4 equivalent) when austenitized at 1200°C/5' would have 12.6% undissolved carbides of V8C7 (Fe3W3)C and (Fe4W2)C type.
This would make for a theoretical PRE (Pitting Resistance) value of (4.3+(4.9*3.3))=20.47 as all Cr and Moly could be in solid solution. In reality it will be lower, but this could be enough to believe that this steel can actually ensure a good stain/pitting resistance when properly heat treated.
PRE number are measures to indicate the resistance to general and pitting corrosion, respectively, where a high PRE number indicates a higher pitting corrosion resistance.
The PRE number being the sum in weight percent of the following elements in solid solution Cr+3,3Mo+16N .

D2 when austenitized at 1020°C would have 14.0% undissolved carbides of Cr7C3 kind.
In these conditions we would have (per another Bohler sheet) 6.4% Cr in solid solution and they calculated a PRE value of 8, meaning that (8-6.4)/3.3=0.48% would be the amount of Moly in solid solution.

All of this is before tempering, yet if tempering is done in the lower range there would not be that much change.

I would like to hear from Surfingringo if he did experience some serious corrosion issue.
 
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Daberti, I do have some information on CPM M4 that basically says the same thing. My main source is "Tool Steels" by Roberts and Carry. I also have the privilege of being able to get excellent guidance form metallurgists at both Bohler-Uddeholm and SB Speciality Metals. Perhaps we could correspond by e mail on some of this. I would appreciate your insight and hands on experience. You can get to me through the contact button on my website and we can go from there. This blade was actually tempered at the high end but I have also done some in the 400F range and have one in actual field use.

Lance may chime in again but he did a forced patina when he first received the knife. I got it back from him through Jim so I could take a look at it. I did have some darker patina on it and a few spots that were very shallow pitting. I cleaned it up with very little effort, basically some work with medium (maroon) Scotch Brite. I was surprised that there was not more corrosion given that this knife was used around salt water. Phil
 
Phil Wilson said:
Daberti, I do have some information on CPM M4 that basically says the same thing. My main source is "Tool Steels" by Roberts and Carry. I also have the privilege of being able to get excellent guidance form metallurgists at both Bohler-Uddeholm and SB Speciality Metals. Perhaps we could correspond by e mail on some of this. I would appreciate your insight and hands on experience. You can get to me through the contact button on my website and we can go from there. This blade was actually tempered at the high end but I have also done some in the 400F range and have one in actual field use.

Lance may chime in again but he did a forced patina when he first received the knife. I got it back from him through Jim so I could take a look at it. I did have some darker patina on it and a few spots that were very shallow pitting. I cleaned it up with very little effort, basically some work with medium (maroon) Scotch Brite. I was surprised that there was not more corrosion given that this knife was used around salt water. Phil
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Email sent, Phil.
Roughly speaking if you austenitize at high temps (1200°C) and triple temper at low (550°C), CPM-M4 will NOT have Cr and Moly carbides, but only W and V ones.
Obviously enough higher tempering temps will mess this setup.

EDIT as April the 27th
I'd be honoured to share my own literature and experience on the field with you.
Along the year I'm doing some day long treks on the Alps and in Tuscany (nearby seashore), in heavily wet/damp/salted air (Tuscany, obviously enough) environments.
Beyond this, I eat ham (the whole ham, not small pieces) fron Tuscany/Umbria. It is HEAVILY salted, and skinning the hard outside plus filleting it Always turned into a enlightening task, as far as stain/corrosion resistance is concerned. Whilst I had staining/rusting issues with ZDP189 >65, CTS-XHP >60 but <62, D2 >60 but no more than 62, I've never had with CPM-M4 or equivalents at >=63. This in the kitchen or Alps. Seashore was somehow a different ballgame IF I didn't mantain and keep the blade clean and oiled. I.e.: my Gayle Bradley Spydie was 61.8 and without a patina, and after a three days hike without any mantainance at all had shown some (small and not hollow but noticeable by naked eye) spot rusting.

I've just given it a look to the S690 own datasheet and I've realized that M4 or equivalents don't actually need to be tempered in the >=550°C level, as far as cutlery is concerned. As a matter of facts 200°C will give more toughness at same hardness and maximize the amount of Cr and Moly in solid solution, when the above mentioned tempering temps will be likely to bring about some Cr carbides .
 
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daberti said:
And here we are.
Your feedback is precious and confirms what I've said here many many times: the importance of edge stability. You made reference to S30V and S90V production blades, I could add Elmax and M390 ones (Always production). All have in common underhardening, in the wrong understanding that this will help resistance to chipping (in applications not involving chopping, as Phil correctly said), but it actually goes the opposite way.
Now, thanks to you I've one more confirmation.
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I think a bigger issue many are concerned with is corrosion resistance rather chipping issues. Especially those that produces and sell knives to far more customers than people on forums and to those that Stainless means a steel that will not stain at all.

Of coarse many here on the forum want to be educated and we chase performance and thereby contact custom makers that are willing to experiment.
 
marthinus said:
I think a bigger issue many are concerned with is corrosion resistance rather chipping issues. Especially those that produces and sell knives to far more customers than people on forums and to those that Stainless means a steel that will not stain at all.

Of coarse many here on the forum want to be educated and we chase performance and thereby contact custom makers that are willing to experiment.
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I tend to agree- or, if not agree- i understand. 90%, IMO, of the customer base of a production knife company is not us. It is someone that if they cant get a reasonable edge on a knife they tend to lose interest in knives all together. For the general knife buying public, it doesnt make sense to put a super steel with a optimal heat treat into their hands. An all around steel, easy to sharpen and wont rust is what sells. I think we are fortunate to have the steels that we do have in the recent years with better and better treatments it seems. Spyderco is a large part of this and i'm glad for what we have available in production knives now-a-days.
 
@Marthinius and @skwurll
Agreed, yet there are some production knives around that cost just as a custom one: I had some customs from SA (M390) costing noticeably less, shipping and duties included.
Or, and I don't make brands' names, rather than having one S3xVx at 59 (actually 58 best case based the 5 I've had hardness tested so far) I'd like purchasing a Domino and a Dice for the same price, which albeit sporting a less wear resistant steel on the chart, have it at least 61 (worst case, and I own both). Here in EU the first costs 589.34EUR whilst the two Spydies together cost less than 592EUR.
I'm not wishing to belong to the "more money than sense" brigade :rolleyes::D . To this extent -and not only- Ankerson's work is PRECIOUS to me :thumbup: :)
 
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I was surprised to see the CPM S35VN out cut the CPM Cru-Wear at similar hardness and geometry. I found the grind ability and finishing of Cru-wear class steel much lower then S35VN.
 
waterstoneblades said:
I was surprised to see the CPM S35VN out cut the CPM Cru-Wear at similar hardness and geometry. I found the grind ability and finishing of Cru-wear class steel much lower then S35VN.
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60 cuts isn't really that big of a spread at that level. :)
 
waterstoneblades said:
I was surprised to see the CPM S35VN out cut the CPM Cru-Wear at similar hardness and geometry. I found the grind ability and finishing of Cru-wear class steel much lower then S35VN.
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That's the good thing about S35VN, you get excellent edge retention with fairly easy grinding and finishing. On this particular knife I only drilled and profiled before H/T and it only took about 1.5 hours to grind and finish this blade to a 600X hand rubbed finish after H/T. And that included etching my mark as well.
That's why I said that I think this alloy is great for knifemakers. Great performance with a reasonable finish time. Time = $$ in my shop. LOL
 
darrin sanders said:
That's the good thing about S35VN, you get excellent edge retention with fairly easy grinding and finishing. On this particular knife I only drilled and profiled before H/T and it only took about 1.5 hours to grind and finish this blade to a 600X hand rubbed finish after H/T. And that included etching my mark as well.
That's why I said that I think this alloy is great for knifemakers. Great performance with a reasonable finish time. Time = $$ in my shop. LOL
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You did a heck of a blade :thumbup::thumbup:
 
darrin sanders said:
That's the good thing about S35VN, you get excellent edge retention with fairly easy grinding and finishing. On this particular knife I only drilled and profiled before H/T and it only took about 1.5 hours to grind and finish this blade to a 600X hand rubbed finish after H/T. And that included etching my mark as well.
That's why I said that I think this alloy is great for knifemakers. Great performance with a reasonable finish time. Time = $$ in my shop. LOL
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And it didn't chip either when I tested it on wood snapping the edge out sideways like 6 or 7 times. :)

That's good for being as thin as it is and in that hardness range. :)
 
Ankerson said:
And it didn't chip either when I tested it on wood snapping the edge out sideways like 6 or 7 times. :)

That's good for being as thin as it is and in that hardness range. :)
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Edge stability Jim, that's it and almost certainly a more favorable V carbides/Cr carbides ratio. I also guess that Darrin HTd in a certain way, so that he managed also to achieve great stain resistance AND residual cementite close to nil.
 
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