CPM3V vs CPM4V

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by gsx-rboy750, Oct 7, 2014.

  1. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014
    Looking for some feed back on CPM 3V vs 4V. I finished two knives so far in 3v with one being 62-63RC and the other being 61. They are both 3/16 survival knives which I have beat the snot out of so far. I did notice some very small chipping on the 62-63RC knife and none on the 61.
    I understand I had the 62-63 done somewhat out of its desired hardness.
    I have done some test flexing on both knives flexing them beyond 50'. Much farther then I ever would. I have read all that I seem to be able to find about both and talked to a rep from a steel company I have bought from but you get really bland non direct answers.
    Say I like a 3V knife at 61. Would I get better hardness relative to toughness with a 4v at the lower end of it's hardness preference of 62-64RC? DOes anyone have some solid testing between the two?
    I love both my knives but would not go over 61RC again on 3V but am unsure if I should try some 4V. Is 4V really as close to 3V toughness as they claim?
    Thanks
     
  2. aarongough

    aarongough

    Mar 12, 2013
    There's not much info out there regarding CPM4V from what I've seen. It's a relatively new steel from Crucible and right now it seems that no-one stocks it apart from Niagara Specialty Metals. I recent paid $200 for a 0.180x1.5x36" bar so I can do some testing with it early next year. Steel prices direct from NSM are much higher than if you bought from one of their distributors, until you start buying at least full sheets (2x3').

    CPM4V is at least partially optimized for higher hardnesses as opposed to CPM3V. 63HRC is pretty hard for CPM3V, was it tested with a Rockwell tester? How did you get it that hard? What were your tempering and austenitizing temperatures?

    The toughness of CPM4V only catches up with CPM3V when they're both at high hardness. The charpy c-notch numbers for both of them at 62HRC:
    CPM3V - 40 joules
    CPM4V - 36 joules

    At slightly lower hardnesses CPM3V is substantially tougher.

    Personally I've had great results with A2 run at 62.5HRC, so I'm looking forward to trying 4V as it should be tougher at that hardness, more corrosion resistant, more wear resistant and the steel should be cleaner.
     
  3. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014
    Thanks for the answer. I was the guy that commented on my handle attachment method. Thanks for the reply in that reguards also.
    Ya I am having Peters do my HT. So to be clear I requested the HT at 61 and 62-63. I have a nother knife getting done 3V as well and I intend on having 60rc so I can compare the HTs. They do the ball method and I could see the difference in indent size and can tell blind flooded what blade is what from running it on a stone. It feels that different. They have a pretty strong method for 3v in belive including cryo. Please dint quote me.

    When I first got the 61rc knife I pounded some cinder blocks and all I got was edge distoration NO chipping. If you are bottoning with the 62-63 and hit some sand you get some really small chips. Understandable from the high HT and low torque.
    So in your eyes a knife in 3v at 62 would be close to a 4v at 62.
    I guess for certain applications I wonder if 3v is excess toughness where 4v is plenty.
    About to order again from NSM and am either getting more 3v and a little 30v for the kitchen or ordring some 3v, 4v and 30v.
     
  4. aarongough

    aarongough

    Mar 12, 2013
    At 62HRC the toughness should be roughly the same in CPM4V and CPM3V. 3V would have an edge in corrosion resistance, 4V would have an edge in terms of wear resistance.

    I'll be evaluating CPM154, CPM3V, CPM4V and some other steels in my next round of testing. I expect that one of the CPM steels will end up being top dog after the testing as I've learnt some extra things about how to get the best performance out of those steels over the last year from other people here on BF. One of the big ones is avoiding the high-temperature temper by using cryo, last time I used 3V I found it tended to dent and avoiding the high temperature temper cycle is supposed to help with that.
     
  5. MeatRobot

    MeatRobot

    203
    Sep 22, 2012
    If your looking for 4v try Aldo I got a 4.5" x 36" at .227" thick for around $240 I'm about to do my first test blade and I'm shooting for 63rc, any info on the heat treat besides whats in the data sheets would be awesome.
     
  6. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014

    I really can't believe that there are no videos comparing the metals. Honestly so many people resite the chemical competition and other fact sheet info but i think very few do real hardcore testing such as Gough. He is one of the few witha actual scientific method.

    As far a Gough what about 20v or 30v? I assume toughness is a major concern of yours Aaron? I will be waiting for your test as it weighed on buying my cpm.
     
    Last edited: Nov 14, 2014
  7. butcher_block

    butcher_block

    Dec 6, 2004
    i love 3v whan 4v came out i was inteested btu then looked at the alloy and didint liek the direction they took to get higher |RC points PD1 fit me better overall then 4v. im sure greata knives are still being made will all the steels but for me PD1 is my upgrade to 3v. learn your needs and find the steel and HT that fit your grind to max out your knife needs
     
  8. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014
    Ya working on that so far I am focusing on 3/16 10-11 inch overall survival type blades. And for 3V i will stick between 60-61RC
    Also out of flat and convex I will focus on convex.
    Sir would you elaborate on PD1 advantages from CPM3V?
     
  9. aarongough

    aarongough

    Mar 12, 2013
    I wouldn't wait on my testing, as it won't be done until at least february or march next year...

    The outcome of my last round of steel testing was ultimately that any of the steels (even 440C) would make a decent knife blade, the toughness and hardness of the steel combine to allow you to make your bevels thinner, which enhances the cutting ability of the knife. Going with a less tough steel basically just means you have to back off on the hardness and also make your bevel thicker.

    If you were to pick any of the high end steels and then tailor your design to them you'll do very well. CPM154, CPM3V, A2 and many more are all good choices. 3V is a good all-round bet from what I've seen, though I would make sure to only use 400ºF tempers with it (in combination with cryo) as opposed to the 1000ºF temper, as I've heard from a few people I trust that it performs much better when tempered low.
     
  10. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014
    Ya I am not a knife maker by trade just like making what I want. I understand as you use tougher materials you can reduce the material thickness and behind the edge. I would say anyone who has cut aluminum and steel with a band saw understand that concept.
    My question is in regards to the same design hard use knife what steel would hold the best.
    I really have no clue what Peters does but I am pretty sure they know what they are doing. Regardless when you do your test I look forward to your opinion and testing.
    J.P.
     
  11. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014
    What about Z-wear vs 3V? any opinions?
     
  12. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014
    Well... I bought a 12x17 sheet of 0.200 Z-Wear. I got everything cut out with 5 knives being ready for heat treat.
    I as probably everybody is looking for that high toughness along with edge retention and ability to refine the primary bevel.
    I will have 3 cpm3v blades and some z wear also to keep and do some testing.
    I like the 3v knife I have at 61rc and feel the 3v one at 62-63 has more chances of chipping given the extra hardness but I like the ability to go to 62rc as I found I like the baseline retention.
    I guess i will see how the z wear blade stacks up. There really is not a ton of real data yet on the comparison that I have found. Even on 3v vs 4v.
     
  13. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014
    Well I think RC 62-63 on 3V is too high NOW for what I use it for. Maybe I need to use the softer end of what it likes.
    Found a knot in some hard frozen maple that wasn't having it. One reason I had this done harder and tested it quite hard.
    Now I think I may have the other 3v knife I have to get hardened to 60 and may have the z wear done at 60 or 61.
    I assume I weakened the blade via flexing it multiple times.
    [​IMG]
    [​IMG]
     
  14. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Any blade being batoned should be tempered for toughness....not hardness.


    People are all "My blade is RC62-63" and such about hardness. Any blade harder than Rc 56 will cut like a fool. Rc 59-60 is a very good hardness. Toughness at this hardness is magnitudes higher than at 62-63. What good is two pieces of very hard knife blade?

    I would rather have to sharpen the blade every few camping trips than make a new blade every few trips.
     
    jll346 likes this.
  15. aarongough

    aarongough

    Mar 12, 2013
    While I agree with Stacy, I will say that my blades are hardened to 62.5HRC and see batoning all the time with no issues. That said frozen hard maple is likely a serious test for any blade.

    I think there's something else going on here. Do you know the exact hardness of the failed blade (was it tested with a hardness tester?)? What was the heat-treat schedule?

    In my experience CPM3V will never show a brittle failure like this unless something was badly wrong in the heat-treat. It should show massive amounts of deformation before failing like you saw. Failing like this at all is weird given that the blade is being stressed along it's strongest axis...

    The datasheets for CPM3V show the toughness sharply dropping off after 60HRC. perhaps if it's actually harder than 62HRC, and perhaps CPM3V drops off in toughness quickly after that point...

    I think this failure is very strange given what I've seen 3V do elsewhere, even at high hardness.

    What were you striking the blade with?
     
  16. Nathan the Machinist

    Nathan the Machinist KnifeMaker / Machinist / Evil Genius Moderator Knifemaker / Craftsman / Service Provider

    Feb 13, 2007
    I don't know how cold the knife is in that picture, but cold embrittlement is a very real phenomenon. They say that quenching a blade coming out of temper into water rather than air cool reduces certain precipitants that are supposed to contribute to it. I haven't tested this.
     
  17. aarongough

    aarongough

    Mar 12, 2013
    Yes that's a good point. I hadn't though about the temperature of the blade during use in this case. I've been looking for data on this specific subject for a while, but haven't found anything more than the fact that the toughness will definitely start noticeably dropping by about -20ºC. If anyone has data on this in regards to tool steels I would love to see it!
     
  18. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014
    I appreciate everyones input. If you look at the close up of the picture there is splintering on one half of the blade. I wonder if this is after effects of flex testing the knife ALOT previously. Ya for sure 3V drops off big time after 60RC. I think 62rc is half of what 60RC is as far as toughness. I had made 3 3v knives. I still have the last one to have hardened. I will have it done at 60. So I have the failed 62rc and my current 61rc and will have a 60rc. I did not see a big difference in edge retention between the 61 and 62 so I will see how the 60 does.
    One my z wear stuff I will do either 60 or 61.
    Arron yes the knives were RC tested.
     
  19. aarongough

    aarongough

    Mar 12, 2013
    What heat-treat schedule was used for the knife that failed?

    How much flex testing are we talking here? 45º+ multiple times, or less?
     
  20. gsx-rboy750

    gsx-rboy750

    356
    Jul 3, 2014
    I had it treated by a good company. Known for 3v. I talked to them before and they said to stay at 61 or under but I wanted some test pieces.
    I flexed that knife 4-5times to 50degrees + and probably another five times at around 45.
    I tend to think it was just treated too stiff and abused to the point of failure. It was a learning experience for me.
     

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