80crv2 chopper: heat treat aspects

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Revolverrodger, Jun 23, 2018.

  1. Revolverrodger

    Revolverrodger

    Jul 23, 2007
    I’m starting to use 80crv2 and plan to make a chopper to work in the woods

    I think the steel I have is spheroidized
    After a bunch of research I came up with the following HT protocol:

    1- Heat to 1600 for 5 min cool to black (should I water quench?) to break spheroids
    2- Heat to 1550 for 5 min cool to black (quench?) to normalize
    3- heat to 1475 for 5 min cool to back and water quench to normalize
    4- heat to 1530 for 5 min and quench in canola at 130 to austenize
    5- temper 400 and water quench twice for 2 hours

    Is this a good protocol for a tough chopper
    Please add your suggestions based on your experience with large knives in this steel

    Thanks
     
  2. scott.livesey

    scott.livesey

    Nov 10, 2011
    is a simple steel, needs a simple heat treat. pre- heat furnace to 1475-1500F. heat for 5-10 minutes. 5 minutes for 1/16", 10 minutes for 1/8" or thicker. quench in 115-120F canola(won't burn you if it splashes). one hour at 400F, quench. one hour at 375F. quench. you want to do all the extra heats, knock yourself out, but won't change final outcome.
     
    DanF likes this.
  3. Salem Straub

    Salem Straub

    Oct 20, 2008
    Some people, myself included, have had trouble getting good hardness from 80crv2 with the large spheroidized structure... mostly it seems to come from Aldo. This does require the extra thermal cycles to get it to respond right IME.
    Scott, what is the provenance of the 80crv2 you've used? AKS has it too, theirs does better when HT'ed as is.
     
    Ken H> likes this.
  4. Revolverrodger

    Revolverrodger

    Jul 23, 2007
    I get mine from canadian knife maker who imports it from NJSB
    Several people have stated that thermal cycling id a good idea
     
  5. Ken H>

    Ken H>

    Dec 31, 2011
    Salem (or others), Is there any way to tell if the metal is large spheroidized structure vs the "good stuff" from AKS? Other than heat to 1500⁰F, soak for 8 minutes, quench and check hardness. If 65, then it's good, but if only 61-62, then it requires normalizing?

    If there is no good way, then is there any harm in going thru the normalizing heats for 80CRV2 even if it doesn't require it? Say, 1600F, 1250F cooling to black between each? Then 1475⁰F to 1500⁰F and quench?
     
  6. Salem Straub

    Salem Straub

    Oct 20, 2008
    The only definite ways i can think of are to know where it came from and how the steel from that source has acted for others, or to harden a coupon and test it as you mention. The rockwell reading would come in 3-4 points lower than expected, or more.
    The OP's thermal cycling listed above is approximately what I've seen recommended/done myself to prepare for hardening. In my case, normally I'd do that anyway since I'm forging, but in the rare instance I've hardened a stock removal blade, I've take the additional steps as if I'd forged it.
    Other than the additional time taken, I don't see there being ill effects from the extra steps taken, even if perhaps not needed. But I think it would take you less time to run a coupon once than to take those extra cycles on more than one blade.
     
    Ken H> likes this.
  7. skillgannon

    skillgannon

    991
    Apr 27, 2009
    I found that I can get good results with aldos 80CRV2 if I do the cycling right. It seems like a better steel for large knives than 1084 but with my little Atlas forge it is a lot more work.
     
    DanF likes this.
  8. scott.livesey

    scott.livesey

    Nov 10, 2011
    several different buys from AKS when then still called it 1080+. HT'd as I posted above yielded Rc62. I have never worked with any of NJSB 80CrV2. I followed recommendations of Roman Landes on the HF forum which has gone away so I can no longer link to the post.
     
  9. bondoo7

    bondoo7

    8
    Mar 1, 2018
    Well Scott, fortunately I've saved a few of Roman's posts (by the way I am Alexandru Bondoc from the late HFB forum). That one you're pointed to is this:

    "Re: AKS 1080+ HEAT TREAT 80CrV2

    Postby Roman Landes » Mon Jul 29, 2013 2:42 am

    800°C with a holding time of around 5-8 minutes does not create retained austenite in a 0,8C steel.

    It will create fine austenite ad thus fine martensite after oil quench in an section smaller or equal to 5mm max. so the only thing you need to do is to temper the virgin martensite after the quench.
    This would be finished after a few minutes in a preconditioned cline.
    But, I would make the few minutes a half an h. to be sure all, even the thicker crossections, have reached the tempering temp. of 180-200°C.

    The thing to watch with a plain carbon steel like 1080 is the grain growth, since it has nothing in it to prevent grain growth at higher temps or longer soak times.

    So prolonged soak times or high aus temps will need to be watched.

    Tempering 160°-170° for a kitchen knife is a bit eager.

    You better leave it with 180-200°C since you will hit the toughness hardnes ratio maximum much better, with little less than a HRC lost in the final blade."

    Hope this is usefull!"
     
    scott.livesey likes this.
  10. Rick Marchand

    Rick Marchand Donkey on the Edge Moderator

    Jan 6, 2005
    I would do this BEFORE grinding, drilling, etc... or after forging, if you forge.

    - Raise that initial normalizing cycle(only the first cycle is considered normalizing) to 1650-1700F to break up the spheroids. Important if you do stock removal.
    - Heat to 1500F, hold for a couple minutes and cool to magnetic.
    - Heat to 1500F and oil quench
    - Heat to 1300F(dull red, still magnetic) a few times
    - Grind, drill, etc..
    - Heat to 1475F, hold for a couple minutes, quench in oil.
    - Temper between 400F-450F

    I really don't think the high-range austenitizing is necessary if you're doing the thermal cycling.

    If you have no idea what the internal structure of your steel is... the high heats make more sense, I suppose. If i can't get it in writing from the supplier, I like to wipe the slate clean.

    Aw, heck... I do it anyway... can't blame anyone but yourself, I say.
     
    Last edited: Jun 25, 2018
    Salem Straub and Don Hanson III like this.
  11. skillgannon

    skillgannon

    991
    Apr 27, 2009
    Isn't the V in 80CrV2 supposed to help reduce grain growth?
     
  12. Rick Marchand

    Rick Marchand Donkey on the Edge Moderator

    Jan 6, 2005
    From what I understand, it "pins the grain boundaries", helping to prevent grain growth.
     
  13. Revolverrodger

    Revolverrodger

    Jul 23, 2007
    Thanks for the info
    I thought spheroidized steel was good fir grinding
     
  14. Rick Marchand

    Rick Marchand Donkey on the Edge Moderator

    Jan 6, 2005
    It is... but finely spheroidized martensite is easier to work with than coarse spheroidizing from mixed structures.

    The way I see it, the idea is to set your steel up for success, without having to resort to extremes.
     
    kuraki likes this.
  15. Revolverrodger

    Revolverrodger

    Jul 23, 2007
    Thank you Rick
    I was wondering if you could help me with a few points:
    1- why is 1530 to high for aust?
    2- for normalizing I have heard peoplr use three temperatures 50 above aust, aust and 50 below aust... does that make sense?
    3- during normalizing is it necessary to quench in water after all heats ?

    Thanks and sorry for the noob questions
     
  16. Rick Marchand

    Rick Marchand Donkey on the Edge Moderator

    Jan 6, 2005
    It isn't "too" high. but it is on the high end of the spectrum, especially when soaking. What we did in those initial cycles to refine grain and distribute carbides can be undone with high heat at extended soak times. If your last cycle was at 1450F and you did your best to "lock it in", I would not want to push my luck.
    It doesn't... Ha!... I'll try to explain it the way I interpret egg-heads like Cashen, Mete and Larrin... no offence, Nerds. Maybe my dumbereded version sings to someone. Hopefully, it isn't too far gone to be useful. Let me know if there is any treacherous metallurgical misinformation.

    Austenitizing temperature is a "phase" not a set temperature. Once you get above critical, you are austeniting. Normalizing is just that... making everything even and normal. That happens with your first high heat at 1650F or so. You are breaking up carbides and growing the grain evenly across the structure. The subsequent heats are refining the grain and referred to as "thermal cycling", not normalizing... but folks know what you mean when you simply call it all normalizing.

    You use descending heats so you don't undo what you've accomplished in the previous cycle. I choose to quench on the last cycle because I feel that working from fine martensite with good carbide distribution is better than a mixed structure with possible segregation and other not so fun stuff. The last dull red heats are kind of a redneck spheroidizing/subcritical anneal. It creates fine spheroids and makes the steel easier to machine, grind and drill. Some steels need this to be done at exact temperature for extended soaks and cooling rates, 80CrV2 is fairly straight forward.
    No. When thermal cycling, you only need to have the steel go from austenite to "another phase". When the steel becomes magnetic again, you've accomplished that and can ramp back up to the next heat. Only on your final heat do you want to mess with the cooling. As I explained above, I quench to martensite. Some don't and that is okay, but you don't want it to run away on you. As it cools naturally, austenite transforms to coarse pearlite, pearlite and fine perlite... if slowed even further, it forms other stuff that I won't get into. Fine pearlite is stronger than coarse and more difficult to machine/drill, so essentially we are avoiding the fine stuff(and other nasties) by quenching in water/oil once it gets below 900F or so.

    *** I have to ask this***
    What are you using as a heat source? All this talk of 1450F, 1530F, 5 minute soaks and such are for nothing if you are using an open forge without a PID. YOU CANNOT "EYEBALL" EXACT TEMPERATURES. There are ways to do it in an open forge but don't fool yourself into thinking you can hold for 5 minutes at 1530F, by eye.

    These are my conclusions, based on the info I have gathered, thus far. Other folks may do it differently and i'd happily change my ways if I felt it would improve my own method.

    That's how this Caveman sees it.
     
    Last edited: Jun 26, 2018
  17. kuraki

    kuraki Fimbulvetr Knifeworks

    Jun 17, 2016
    Everything else aside this is something I've been curious about. @Larrin has commented he didn't see a reason for using descending heats in the past. I've wondered why 3 subsequent thermal cycles at say, 1450F would not have the same effect on grain formation as 3 descending heats. Once you've normalized, and have even grain distribution, what structure is being protected (and through what mechanism?) by descending heats?

    Descending heat seems to be SOP and therefore has been "proven" at least in all of our anecdotal experimentation to create the fine grain we want, I'm not questioning that. I haven't yet, but want to do some coupons to see if 3x1450 had the same effect as 1550 1500 1450 (or whatever descending schedule).

    Again, just for discussion, I know what we're doing works, just wondering if we're doing more work than necessary to achieve that goal.
     
  18. Rick Marchand

    Rick Marchand Donkey on the Edge Moderator

    Jan 6, 2005
    You make a valid point... aside from that first normalizing heat at 1600F+, the subsequent re-nucleation heats for refinement wouldn't appear to be dependent on descending temps. You may have just rocked my world, brother.

    Perhaps, we've just taken the "don't undue what you've done" a bit too far?

    I don't see how 1650F, 1450F, 1450F wouldn't work for normalization and refinement. A couple points you made, though.

    I don't think there is such a thing as "grain distribution"... it would be "carbide distribution"... and that is what the subsequent heats do along with refinement and is also what we are trying to protect from excessive heat.
     
    Last edited: Jun 26, 2018
    kuraki likes this.
  19. Larrin

    Larrin KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jan 17, 2004
    Yes I did mention that I'm not sure what the benefit would be of descending rather than a high temperature normalize followed by "low" temperature grain refinement cycles. That is the recommendation that Cashen gives in the new DVD as well.
     
  20. kuraki

    kuraki Fimbulvetr Knifeworks

    Jun 17, 2016
    Sorry, could you clarify which is the recommendation he gives? Static temp grain refinement?


    Right on. I continue to mix up grain and carbide in my head for some reason.


    ETA: My theory is that the descending heats are a carryover "best practice" from doing it by sight in a forge. In that it would be easier to "undo" your grain refinement by over heating, but by doing descending heats, it's "safer."
     

Share This Page