BCMW ht 3V chopping tests

ht cpm 10V paring blade today. Snapped twice when attempt to straighten prior to Mf (martensite finish) - end up with around ~4" worth of OAL to test (about 2.5" cutting edge).
This blade is very brittle in conventional sense. Virtually no plastic deformation zone, i.e. anything past yield = chip or snap. Yes, like glass.

Test edge geometry: 0.007"BET/ 14dps, finished with dmt extra fine (a few strokes) - phone book slicing edge

Cut tests: 1/2" dia sisal rope, whittle african blackwood, beef rib bone, nail - passed
Chop 16d nail: chip, chip, chip, chip, chip, ....

Tested at 68rc.

My assessment: Failed ht!
 
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Not test s35vn yet but hrc met my expectation.

20CV/M390, 0.02" BET / 15dps
Passed - whittled: AB, CRB, 16d nail
Rippled - chopped 16d nail.

tested hrc 65.

Assessment: Good ht.
 
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Dang!!!! You are really running up some of those steels to about as high or higher than they are supposed to go, Luong!!!!! By the way, I noticed that something was mentioned in the talk from both you and Nathan that probably didn't get enough time. Both of you guys have gone with immediate cryo AND the low temperature tempering cycle. Nathan has been taking about that for a while. Some will tell you that the secondary hardening hump you get from the high temperature temper is a good thing, but you two guys have cast some SERIOUS doubt on that theory. What should not be left out of the discussion is that it appears that immediate post quench cryo is an absolute MUST if you want to do the low temp tempering right in order to avoid high levels of RA.
 
Retraction - this tip is partially carburized (i.e. softer). Plastic zone is much narrower than shown by this image.

bluntcut said:
I guess best for me to 'Almost-show' better than 'tell' - so here is the tip of a 66rc 3v paring/util blade bent(~5mm radius) past yield into plastic/set zone. Welcome to imagine a much longer radius where the bent blade make at least a complete circle.

5RA6ziI.jpg


Fun read - some basics on crystal structure - http://engineering.unt.edu/material...f/MTSE 3010/Class7_handout MTSE 3010 2013.pdf
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CPM Rex 121 @ 67rc shows micro ripples, sign of good edge stability. I will use 67rc as its working edge hrc.

QYf19ef.jpg
 
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CPM 10v 65.5rc hammered through 16d nail - oh, there is a ripple transitioning to fracture/chip. Working hrc = 65.5rc

tj3Xt4T.jpg
 
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We are on the same page, Joe:thumbup:

Cryo + low temper is a low hanging fruit for high alloy heat treaters however outcome still in grey area depend on dislocation & post-tempered ra%. Edge with easy roll & chip at the same time are tell tale of high RA%.

SH (secondary hardening) can be great beneficial for when coarse wear resistance required. The whole SH temperature range can be utilize for fine cutting edge tools if mart matrix has mostly lath structure. Otherwise, more loss than gain to use SH.

jdm61 said:
Dang!!!! You are really running up some of those steels to about as high or higher than they are supposed to go, Luong!!!!! By the way, I noticed that something was mentioned in the talk from both you and Nathan that probably didn't get enough time. Both of you guys have gone with immediate cryo AND the low temperature tempering cycle. Nathan has been taking about that for a while. Some will tell you that the secondary hardening hump you get from the high temperature temper is a good thing, but you two guys have cast some SERIOUS doubt on that theory. What should not be left out of the discussion is that it appears that immediate post quench cryo is an absolute MUST if you want to do the low temp tempering right in order to avoid high levels of RA.
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Bluntcut, if you tempered your 4V back from 67.5 down to 65-66 HRc, would it have better toughness, less rippling on the nail chop?
 
I don't think going lower rc would help but actually worsen. Rippled is a sign lacked of sufficient strength to resist deformation, thus permanent deformed/rippled. In this case, thicken geometry is the answer. As a repeat - 20dps is 2.3x time stronger/stiffness than 15dps. So increase this edge by 2-3dps probably would suffice for chopping at 16d nail. Need tune geometry to apply to hammer through 16d nail situation.

black mamba said:
Bluntcut, if you tempered your 4V back from 67.5 down to 65-66 HRc, would it have better toughness, less rippling on the nail chop?
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There pros/cons on Secondary Hardening Temper. If microstructure is bad/messed up to start with at low temper, SH hurt because Cons would get amplify while Pros are muted.

Let's do a quick hypothetical journey through of tempering a 65rc 3V - OK, at least this is my thinking anyway +- fuzz factors.

Start - 65rc high strength with good toughness.

400F - 63rc still high but loss some strength, gain nano wear resistant from precipitated fine cementites, gained some ductility. together = gain some toughness.

500F - 61rc macro hardness but nano hardness is substantially lower, cementite slightly coarsened, gain more ductility. Coarsened cementite cancel out ductility. Threshold point of more loss than gain in both strength & toughness

500-700F - Meh per above

700-800F - 60rc matrix won't get any softer until 950+F, Cr grab C to form fine Cr7C3, gain fine wear resistant (much more than Fe3C/cementitie), loose corrosion resistant proportional to amt Cr locked in CrC.

950F - 61rc added 1rc because of particle/carbide strengthening form slightly coarsen CrC. **NOTE** carbide volume is now almost double to ~6%. I definitely can feel it on sharpening stone.

960+F - Carbon leak out of matrix to rapidly coarsen CrC. Loss of strength, loss more corrosion resistant, loss sub micron edge stability, actually on degrading slope of toughness.

OK, I did tried those scenarios above. Anyway, here some pics for you

RbuA2DN.jpg
 
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Epoxy curing - natural curly mango handle 3V chopper (to cross-eval with Nathan). Just want to see finished look of curly mango before have them stabilize (clear & dye). Yep, natural wood is light, soft and low weather durability but hey it's mushy tough.

In the next few days, I will ht s110v, elmax, cpm-m4, cts-xhp, 10V(again) and maybe k390 & zfinit. Ht research addiction continue but will stop as soon as addiction cease:p

edit: ugh - band saw won't bite pg s110v. Skip it for now, will use angle grinder next time. Substitute with cheapy A2.
 
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I pondered then just tried...

What if I use halt-tang 66rc 3V, 65rc aebl and Mora carbon knives chop edge of a large TiN (titanium nitride) coated drill bit?

3V(chipped) & aebl(smushed & sort of chipped) = 0.025" up from apex. Drill bit chipped highly visible (10x larger than Mora case). i.e. destruction craters on blade & drill bit. crater on drill bit has smaller radius.

Mora = 0.03" up from apex. Drill bit has hardly visible chips. Destruction crater is mostly on Mora.

This is like an explosion from impact, where impulse force vastly exceeded UTS (ultimate tensile strength). Destruction radius outlined the perimeter surface at UTS threshold. Brittle (can be soft but brittle as well) steels propagate the impulse - instead of disperse like the 3 blades above. If this propagation go all the way to the spine = break the blade. Partial = long crack + some chip at apex.

IDK what severity of damage when this impulse has high sheer component, e.g. a chopper chops metal cutting blade -> momentum pivot at edge2edge.
 
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Wow man, that's some awesome work! Keep it up... you are like a hero, hehe!

Do you think you can also test Infi, Z wear and Z tuff? (with Infi it will be a bit harder, i know)
 
Thanks. I've tested zwear & spectrumwear here & there but not with my latest ht yet. High alloy steels with low carbon% are not on my radar now and foreseeable future.

Salival said:
Wow man, that's some awesome work! Keep it up... you are like a hero, hehe!

Do you think you can also test Infi, Z wear and Z tuff? (with Infi it will be a bit harder, i know)
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gmail
flexdog
2008

noob93 said:
do you have an email I could reach you at?
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Ht 3 times + long sequences of tempering - max hrc = 59.5

Edge stability is quite good at 59.5rc but below my target 62rc, thus failed objective.
 
Tested (yesterday)

S35VN 64rc, hollow grind (broadened from 10" wheel), sub 0.005"BET, 13-14dps

Whittled
AB - passed
CRB - rippled & micro chips
Nail (LOL) - big ripple (silly lateral on something this thin)

Non-bone cut 2 whole chickens for bbq: passed. Press-cut through bones (no legs/thights) - small ripple.

Assessment: Good ht
 
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