Ankerson, I always enjoy reading your posts, you obviously have more knowledge and experience than I will ever have. The knives I have in 12c27 I like because they seem tough and easy to sharpen. Which stainless steels would you say are as tough and easy to sharpen, yet hold an edge better? I realise that geometry and hardness are big factors, but I mean in general, everything else being equal?
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12c27... why not more love?
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Ankerson
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I would go with CPM 154/RWL-34 as the main choice then ELMAX or S35VN after that.
HT and geometry is everything though as we all know.
CPM 154/RWL-34 is one of the best more balanced stainless steels out there with a proven track record.
None of them are really hard to sharpen.
Bump....
Could somebody explain to me why 12C27 should be thought of as being functionally different than 1095 in terms of performance (given reasonably similar Rc levels)?
Could somebody explain to me why 12C27 should be thought of as being functionally different than 1095 in terms of performance (given reasonably similar Rc levels)?
:fatigue:
Who really gives a spit about 12c27. It is a low grade steel you can make a blade from. It will never perform from an edge retention perspective like a super steel and is used only because it is cheap and easy for knife makers to work with. No one in their right mind would ever prefer it over granulated steels except for the dude machining it. I will even go out on a limb and say that s35vn at the same hardness will outperform 12c27 in every way as a knife steel except for during manfacture.
:hopelessness::disgust:
Who really gives a spit about 12c27. It is a low grade steel you can make a blade from. It will never perform from an edge retention perspective like a super steel and is used only because it is cheap and easy for knife makers to work with. No one in their right mind would ever prefer it over granulated steels except for the dude machining it. I will even go out on a limb and say that s35vn at the same hardness will outperform 12c27 in every way as a knife steel except for during manfacture.
:hopelessness::disgust:
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toughness? everything is a trade off and from what i have read S35VN isn't nearly as tough or ductile as 12c27. could be wrong... not the first time.
Ankerson
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Actually the information is very sketchy/vague on 12c27/PM27 really, but from what I can tell from the data sheets etc it and S35VN are in the same range toughness wise or in other words there isn't that big of a difference.
S35VN and AEB-L/ 13c26 are basically the same toughness/impact resistance based on the data sheets.
Those are based on real numbers from the data sheets, that's what the numbers say anyway.
So what that all means is that S35VN and 12c27 are in the same range toughness wise, but S35VN has one heck of a lot more edge retention.
Same can be said for S35VN and 13c26.
HT and geometry are still large factors though as they always will be so adjust according to actual needs.
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Ankerson, glad you're still following the thread.
I would like to hear your perspective on what performance differences you see between 1095, 420HC and 12C27, assuming similar hardness levels of, say, 58Rc (common for each).
I'm keying off of your comment that the soldiers in question might have been well served being given knives made from 1095 along with a simple sheath carried stone. Based on what I've seen (as a user), I can't tell any difference between these 3 steels other than the fact that 1095 forms patina and rusts more easily. Again, this is all with knives known to be hardened in the 58Rc range (Schrade USA, Mora, Opinel, Buck).
I would like to hear your perspective on what performance differences you see between 1095, 420HC and 12C27, assuming similar hardness levels of, say, 58Rc (common for each).
I'm keying off of your comment that the soldiers in question might have been well served being given knives made from 1095 along with a simple sheath carried stone. Based on what I've seen (as a user), I can't tell any difference between these 3 steels other than the fact that 1095 forms patina and rusts more easily. Again, this is all with knives known to be hardened in the 58Rc range (Schrade USA, Mora, Opinel, Buck).
Ankerson
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Experiences will vary as with most things, actual knives, geometry etc.
Head to head at the same hardness, geometry etc cutting the same media it would be 1095> 420HC> 12c27.
1095 has the highest Carbon content of the 3.
From what I have personally seen, 12c27 goes dull VERY FAST like 420J2 does, that's actual use.
Interesting [1].
Very interesting because the numbers are 0.95 > 0.60 > 0.46 > (0.36 - 0.15).
These are the carbon numbers for 1095, 12C27, 420HC, (420J2).
So, if we're only going to talk about edge retention only (a problem in itself, since the whole point of the thread is that it's not always about edge retention) and in so far as carbon content is the primary predictor of edge retention, then one would expect that the ordering would be:
1095 > 12C27 > 420HC (> 420J2).
BTW, I think it's pretty hard to compare 12C27 and 420J2 "head to head at the same hardness" given that 12C27 is typically run at 58Rc (Opinel, Mora (57)) and iirc 420J2 maxes out at around 55Rc.
Personally, I can't tell any difference in use between 1095, 12C27 and 420HC if all are at 58Rc. Maybe I'm doing it wrong.
I can tell a difference between those steels and 420J2. It's way soft.
Regardless, if a soldier would do well with a 1095 Ka-Bar and a crude stone in a sheath, that soldier would do just as well with a Ka-Bar made from 12C27 or a Ka-Bar made from Buck's 420HC. At least, that's been my experience.
[1] - I assume you're talking about edge retention with this ranking, and not an overall ranking based on all factors.
Ankerson
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The steel used in Ka-Bars is 1095 Cro-Van, not quite the same as basic 1095..
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Is there really a practical difference? Significant enough to notice in unmarked blades in use?
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If you have the datasheets for 12C27/PM27 13c26 etc where they give impact toughness etc please do share as I have not found them.
One thing I feel is neglected here is carbide volume.
Carbide volume does affect the impact energy of a steel.
Carbide volume according to data sheet of S35VN.
CPM S35VN 14.0%
CPM S30V 14.5%
440C 12.0%
154 CM 17.5%
CPM S90V 20.0%
From the CPM-3V patent of Crucible:
"An important aspect of the invention is illustrated in Figure 3 which shows the Charpy C-notch impact test results versus total carbide volume for the PM tool steels that were heat treated to 60-62 HRC, as well as test results obtained for several conventionally produced tool steels at about the same hardness. The results show that the toughness of the PM tool steels decreases as the total carbide volume increases, essentially independent of carbide type."
Reference: https://www.google.ca/patents/EP0875588A2
This is also stated on Zapp Steels website:
Now where the "data sheets" give some information as to C-Notch tests is in the transverse energy readings in S35VN and longitudinal impact energy in the CPM3V "data sheet" but no values in the transverse or longitudinal tests for CPM-154. Only a graph.
No surprise that the powdered metallurgy performs better in the transverse department though but I would love Crucible to compare CPM-154 to S35VN in both longitudinal and transverse testing.
The only values I can find for 440B (closest to 12C27) is 20 ft/lb Transverse Rapture.
http://www.gkn.com/hoeganaes/media/...ess Steel AISI Grades for PM Applications.pdf
Ankerson
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Head to head in like blades in testing I would say yes, in real world actual use, that will vary depending on use etc.
Same old answer as usual.
It depends.
There aren't any definite answers especially in steels that are relatively close in alloy content.
Ankerson
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If you have the datasheets for 12C27/PM27 13c26 etc where they give impact toughness etc please do share as I have not found them.
One thing I feel is neglected here is carbide volume.
Carbide volume does affect the impact energy of a steel.
Carbide volume according to data sheet of S35VN.
CPM S35VN 14.0%
CPM S30V 14.5%
440C 12.0%
154 CM 17.5%
CPM S90V 20.0%
From the CPM-3V patent of Crucible:
"An important aspect of the invention is illustrated in Figure 3 which shows the Charpy C-notch impact test results versus total carbide volume for the PM tool steels that were heat treated to 60-62 HRC, as well as test results obtained for several conventionally produced tool steels at about the same hardness. The results show that the toughness of the PM tool steels decreases as the total carbide volume increases, essentially independent of carbide type."
Reference: https://www.google.ca/patents/EP0875588A2
This is also stated on Zapp Steels website:
Now where the "data sheets" give some information as to C-Notch tests is in the transverse energy readings in S35VN and longitudinal impact energy in the CPM3V "data sheet" but no values in the transverse or longitudinal tests for CPM-154. Only a graph.
No surprise that the powdered metallurgy performs better in the transverse department though but I would love Crucible to compare CPM-154 to S35VN in both longitudinal and transverse testing.
The only values I can find for 440B (closest to 12C27) is 20 ft/lb Transverse Rapture.
http://www.gkn.com/hoeganaes/media/...ess Steel AISI Grades for PM Applications.pdf
Surprise, there aren't any as in they didn't do any on 12c27 or it would have been published in their datasheets.
So they tend to use 13c26 as an example or round things off for some odd reason.
There really wouldn't be much of a difference between 12c27 and 13c26 as far as impact toughness goes, not enough to really matter anyway, both are strip steels.
chiral.grolim
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Regarding the link, isn't that 20 ft.lbs (27 J) value for 440B longitudinal impact energy of an un-notched specimen at ~34 Rc?
The 3V patent chart is longitudinal Charpy C-notch values. 440C has ~12% carbide volume at 58Rc, very similar to D2, while CPM154 has ~18% and S30V has >20% if I'm not mistaken, like that "PM 12Cr4V" on the chart - approximately 2X higher carbide volume but same impact toughness as D2. Crucible says that the longitudinal Charpy V-notch is approximately the same for CPM154, S35VN, S30V: 22 - 28 ft.lbs (30-38 J), and that is comparable to (slightly superior than) 440C (22J @ 58Rc).
In the 3V patent it states the following:
The PM steels present significantly higher carbide volumes while also presenting high impact toughness. One would hope that other steels with 4-8% carbide volume and <6um carbide aggregates at 58+ Rc would present similar Charpy toughness values to 3V ... but A2, O1, 1095, etc. (similar carbide percentage to 3V) don't really come all that close with toughness values in the 40J-range. We've seen the micrographs of 13C26 and O1 carbide size and distributions, looks really good for ingot steel, but if O1 isn't that much tougher than CPM154... *shrug*
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thought this was a fun read, at least Sandvik's higher level heat treating systems, and that 12c27c is done by piece, that's cool.
Here's their guidelines:
link to data sheet: http://www.smt.sandvik.com/en/materials-center/material-datasheets/strip-steel/sandvik-12c27/
Here's their guidelines:
link to data sheet: http://www.smt.sandvik.com/en/materials-center/material-datasheets/strip-steel/sandvik-12c27/
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All good comments. I agree the contribution of powdered metallurgy and the refinement of grain size has really pushed the ability of higher alloy steels to be tougher, my only concern with regards to the increase in carbide volume is that it could create stress concentration for crack growth or fracture toughness. Crack growth starts with non-metallic inclusions, individual carbides and carbide clusters or (if they are present) at voids.
I mean the carbide clustering can be seen in CPM-154:
Compared to AEB-L
This is why I tend to question what is mentioned in "data sheets". Crack growth etc IMO is important for steels that would be used in fixed blades etc at thin geometry but we do not see values for fracture toughness. It could be because of the shear amount of different tests for fracture toughness measuring different aspects.
One of the main comments that started me in questioning "data sheets" was from Ed Schempp.
Ed Schempp said:
The more I read the more I realise the less I know. :foot:
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chiral.grolim
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All good comments. I agree the contribution of powdered metallurgy and the refinement of grain size has really pushed the ability of higher alloy steels to be tougher, my only concern with regards to the increase in carbide volume is that it could create stress concentration for crack growth or fracture toughness. Crack growth starts with non-metallic inclusions, individual carbides and carbide clusters or (if they are present) at voids.
I mean the carbide clustering can be seen in CPM-154:
Compared to AEB-L
This is why I tend to question what is mentioned in "data sheets". Crack growth etc IMO is important for steels that would be used in fixed blades etc at thin geometry but we do not see values for fracture toughness. It could be because of the shear amount of different tests for fracture toughness measuring different aspects.
One of the main comments that started me in questioning "data sheets" was from Ed Schempp.
The more I read the more I realise the less I know. :foot:
One thing i would put to you is that the crack initiation can start at a very small inclusion and what it needs to propagate is grain-boundaries (weak joints) to follow. In those images, CPM154 has larger carbides with grain-boundaries around each one - a less-linear path for a crack to follow; and there is much greater distance between carbides making it much harder for a crack to jump across (actually proceed through) the tougher tempered-martensite/austenite to the next weak-joint around the next carbide. For the AEB-L, the path from carbide to carbide may be more linear with less matrix between. Using these slightly larger carbides in the midst of larger distances between may actually give the slightly higher-carbide volume CPM steel slightly greater fracture toughness than the lower carbide AEB-L though the difference might not be noticeable in actual use where threshold stresses are likely to be unreached or exceeded for both. But for ingot high-carbide steel, the larger carbide aggregates provide a path yet more linear with less matrix between than the lower-carbide AEB-L (or 420HC) hence the increased toughness over steels like 154CM and 440C. Using PM you get very high-carbide (high-wear) steels with toughness levels comparable to low-carbide (low-wear) ingot.
Here is a chart relating to fracture toughness in cemented carbide (<30% matrix WC-Co) that helps illustrate fracture toughness with regard to matrix volume and carbide size, specifically looking at the differences in toughness at 85% carbide between "submicron" vs "medium" and "coarse" carbide material. There are some excellent papers on the toughness of cemented carbide detailing how fracture-toughness relates to the ease with which a crack can follow a path through the material.
Again, Crucible suggests in its data sheets that the difference in longitudinal impact toughness between 440C (22J @58Rc) and S35VN (38J @58Rc?) may not be all that noticeable (or the values have a large range of deviation) so they push transverse impact toughness instead, and Sandvik won't even release notched impact toughness values for what they peddle. Based on the data from cemented carbides, I am suspicious that fracture-toughness values would be even closer, i.e. harder to differentiate steels that are between 4% and 24% carbide rather than only 4% to 24% matrix as is the case for cemented carbide - there is just so much more matrix in knife steel to absorb fracture energy, it is likely not a very good way differentiate between them for this purpose. *shrug*