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

Discussion in 'Knife Reviews & Testing' started by Ankerson, Nov 24, 2010.

  1. bluntcut

    bluntcut KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2012
    Pertain to ht with cryo quenched for high alloy steels (starting out with low as-quenched RA% < 2%)

    *1* Aust temperature above 1050c = head toward grain coarsening (see chart below).

    *2* HTT (high temperature temper > 500c): Cr & Mo precip (mostly Cr) = loss of corrosion. Precipt carbide coarsening/enlarging = some level of lowering elasticity and apex keenness.

    *3* LTT (low temp temper < 350c): cementite precip is mostly diffusionless (thanks to alloy for blocking C movement) - therefore cementite remain at nano scale non-crack-initiator/nucleator particle.

    Jury/camp for edge tools LTT vs HTT is a continuing discussion - perhaps so because context of usage could tilt between pro/con. Does this tradeoff worth it - HTT to get rid of 2-% RA in trade for more/en-larged CrxC and gave up some corrosion resistance? It's sure relevant to edge stability and endurance (of course depend on intended uses).

    Also quite obvious from my posts on BF - my blades are mostly LTT (and occasionally untempered). YMMV :D

    http://i.imgur.com/VR4Bhzg.jpg
    [​IMG]

    http://i.imgur.com/XMBFzZt.png
    [​IMG]

    IF edge tools are for cutting & chopping - IMHO Zt S35VN knives (I presumptuously assess based on videos and other people anecdotal opinion/data) are sub par performance on intended uses. S35VN definitely a poor choice for prying tools.
     
  2. daberti

    daberti

    496
    Apr 2, 2005
    Martin, you nailed it.
    Every steel obviously has a delta where the balance between good edge holding and though ness can be traded for each other.
    But asking from an M390 the toughness of a 3V ...well it is another story to be told.
     
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  3. daberti

    daberti

    496
    Apr 2, 2005
    Bluntcut, please allow me to get back from beer to properly reply to your quite interesting post &#128077;&#127995;
     
  4. daberti

    daberti

    496
    Apr 2, 2005
    @Bluntcut

    Sverker, Sleipner, Calmax and Rigor are ingot steels where Vanadium content is pretty much negligible and this is pretty much important about grain growth as V is a very proficient grain refiner.
    Vanadis 4E has deinitely a more important content of V and it is PM. I've had some knives in that steel and if not high austenized it rusts in a breeze. Not a great bargain against 3V.

    Back to the SS I mentioned, all of them require interrupted quench at 80°C and if aust. above certain temps the aust. time is even half.
    What is more important is that quenching (I'm limiting to the production knoves thus vacuum...) has to be done in an overpressured environment of at least 3Bar in compliance of their CCT graphs in order to avoid the Bainite nose. If there is at least 0.5%W content this will additionally help avoiding Bainite nose, as well. Count M390 in, so.
    Your charts do not show the most important thing: how was it done the quenching in vacuum furnace? No overpressure? Then no mercy: grain growth is just expected.


    As an example, Elmax aust. @1080°C has a PRE value of 15, just on par with 440C aust. @1050°C. Unsurprisingly by sporting 16%M7C3 Cr carbides and 2%MV V ones. 440C has 9%M7C3 Cr carbides.
    I've an Elmax fixed blade made by my HT specs using Sec. Hard. a bit short of it apex (520°Cx3 and deep cryo in between) and aust. at 1150°C (vacum, and 5bar overpressure interrupted quenching).
    Proper quenching following these rules will greatly limit grain growth.
    Never seen a hint of rust in my trekking sessions, nor any chipping or microchipping (my ZT 0560 Elmax did show both troubles: same 20° per side and finishing).

    Secondary hardening must be always associated with the highest possible aust. temperature and the most efficient and CCT compliant quenching available to us.
    This is just plain common sense as this way Cr carbides will be dissolved as much as possible (aust. phase) and the SH if not pushed to its very limit won't generate such a Cr/Mo carbide precipitation to have an impact on stain resistance, which will be better than (following my example) if I hardened my Elmax blade 1080°C/150°C.
    Just do a test yourself: 1080/150°C against 1150°C/520°C, 3 bar overpressure (following CCT), tre temper and deep cryo in between. Go and compare hardness: the blade with higher hardness will have less Cr carbides thus more C and Cr available in solid solution, thus an higher HRC value and stain resistance.
     
  5. bluntcut

    bluntcut KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2012
    I understand your view point but there are many more ways to achieve certain desirable + some ht result. For examples - I sold this Elmax a couple weeks ago

    [​IMG]

    This knife was wider than this before I batoned it through a 16D nail. As-sold the edge would ripple before fracture. I have a few other elmax blades with different ht version settled for ~63rc however I am not happy with them because edge can only ripple very little before fracture/micro-chips when whittle nail.

    btw - small % RA actually functions similar to ferrite on high impact.

    As for grain size - I perform grain refinement on steels range from rex121,15v down to 5160. Last weekend, I tested this:
    [​IMG]
    [​IMG]

    Well, whether actually I did refined grain or not may not important as - how could that even possibly be done for elmax/s110v/m4/etc?

    To say - there are much more to learn about ht for everyone, myself included.

     
  6. daberti

    daberti

    496
    Apr 2, 2005
    @Bluntcut

    First thanks for sharing your works and knowledge: yes, count me in as an HT learner as well.

    My experience (answering to your implicit question) is that if you want blades capable of withstanding severe impacts (I'm repeating it to myself as well) the first thing is to choose proper steels.

    More than bare thoughness data I learned to rely on the lowest possible content of Cr carbides.
    Cr carbides typically place at grain boundaries with two side effects:
    1)Where they are there is poor stain resistance and here will start pitting/rusting etc
    2)Being them relatively bigger than Moly, W, V carbides (even on PM steels), if a chip is to start, it will be typically there.

    CPM-4V and equivalent grades will have Cr carbides.

    CPM-3V will not. It will sport 5-7% MC V based carbides. This is why it is somehow stain resistant and so tough.

    CPM-M4 and equivalents will have 12-14% overall carbide content if high aust. Let's leave tempering alone for now. Very few Moly ones, and MC W and V.
    W and V carbides will place mainly intra-granularly, creating a "bond" which will reinforce the strength of martensitic grain itself.
    In the end for this steel I'd recommend as the best compromise between hardness and toughness:
    Aust. @1150°C, 15min. minimum holding time at aust. temperature
    Oil quenching
    4 tempers:
    option A) @550°C (63HRC aim hardness)
    option B) @520°C (62HRC aim hardness)
    EDIT: always use a thicker specimen than the final thickness desired.

    Edge finishing: 18° per side with a micro-bevel at 21°per side. If it withstands punishment then try 15° main bevel with 21° microbevel
    Finishing grit: my usual finishing reference for a steel with such fine carbides is Naniwa Chosera stone in 10000 grit, which has a lot of feedback.

    Elmax and M390: I've posted the HT in the Lionsteel->Steels forum

    You can hit me a PM so that I could leave you my email, for a mutual exchange :)

    Nearly missing: use as reference CCT diagram the one of BU S690 View attachment BOHLER_S690.pdf
     
    Last edited: Apr 4, 2017
  7. bluntcut

    bluntcut KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2012
    Thanks for sharing ht insight and actual params and edge geometry for impact. I agree about best to start with steels designed for appropriate applications and usages. I enjoy doing unconventional ht - M2 and Cruwear micrographs above are grain refined, plus grain boundaries and particle/carbide interface cohesion optimized. Of course, I coined these terms for my work, which might or might not have merrit in metallurgy ;) fwiw - I made two 15V 70rc compact chopper & util (aka chomper).

    Sorry about my little OT, Jim!

     
  8. daberti

    daberti

    496
    Apr 2, 2005
    @ Bluntcut: Edited option B)
     
  9. bluntcut

    bluntcut KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2012
  10. hugofeynman

    hugofeynman Gold Member Gold Member

    626
    Jan 18, 2011
    Sorry my ignorance, but why cpm-4v will have Cr carbides and Cpm3v not? Doesn't Cpm3v have more Cr in his composition? I'm more interested in Vanadis 4 extra properties, but cpm-4v is pretty identical.
     
  11. daberti

    daberti

    496
    Apr 2, 2005
    Because CPM-4V has 1.35C content against 0.8%C of CPM-3V.

    Vanadis 4 @1150°C/15’ 9,1% carbide content: 34,3 % Cr7C3; 12,5 % V4C3; 53,4 % V8C7 (datasheet already referenced in this thread)
    Van. 4E will still have 18-20% Cr7C3 carbides.

    Lower than 1150°C and more Cr carbides.

    I quite dislike CPM-4V class steels.
     
  12. hugofeynman

    hugofeynman Gold Member Gold Member

    626
    Jan 18, 2011
    Thank you, daberti!
     
  13. cornfedgroove

    cornfedgroove

    12
    Aug 28, 2011
    Interesting
     
  14. daberti

    daberti

    496
    Apr 2, 2005
    @Hugo and @Confed
    You're welcome :)
    To make things clearer I should plot a phase diagram, honestly speaking, but I'm terribly longing for my bed now.
     
  15. hugofeynman

    hugofeynman Gold Member Gold Member

    626
    Jan 18, 2011
    Thanks daberti, I love to speak about steels (listening more than speaking) so I'll follow this thread with entusiasm!

    Best regards!
     
  16. daberti

    daberti

    496
    Apr 2, 2005
    As a matter of facts I'm uncovering some strictly metallurgically related aspects on this thread because I think that they are intimately connected with Jim's testing results.
     
  17. MAD777

    MAD777

    267
    Aug 3, 2011
    And so appreciate because Jim's tests show not only differences among the steels, but also differences among the heat treats.

    Sent from my SM-G900V using Tapatalk
     
  18. LX_Emergency

    LX_Emergency KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 28, 2007
    And among grinds. The increase in performance between a production Spyderco blade and a reground to be thin behind the edge reground spyderco blade is crazy.
     
  19. hugofeynman

    hugofeynman Gold Member Gold Member

    626
    Jan 18, 2011
    It's geometry that cuts, all other things being equal! Bad geometry in a great steel very well heat treated cuts worse than a proper geometry in a simple steel. That's physics I guess.
     
  20. MAD777

    MAD777

    267
    Aug 3, 2011
    That's why I like that Jim reprofiles most of the blades (and reports thickness behind edge) to try to level the playing field on geometry somewhat.

    Sent from my SM-G900V using Tapatalk
     

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