K390 Toughness Data or Comparisons? (Any Charpy Info?)

C

cm_bushman

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Oct 22, 2012
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K390 is a pretty sweet steel on paper, and I am very excited to be getting the chance to test it in an incoming Mule Team knife. From what I've read on the forum, it's a modified version of A11 (k294/10V), designed to improve toughness while maintaining nearly the same wear resistance. What I am wondering is just how "improved" the impact resistance is vs. steels like 10V (it's parent alloy), CPM-M4 (famous for it's balance of toughness and great edge retention, and my favorite user steel), and s90v (the next step down as far as I can see in edge retention).

The Bucorp lit (here in .pdf) shows the impact resistance of 10V to be about 75% that of K390 at 61HRc, with ~44J or 34.45 ft/lb of force used for the K390. I can't really compare this directly, since I'm not sure that Charpy standards were used, but using other sources to place the toughness of 10V @60HRc at ~20 ft/lbs, this data seems a bit optimistic for Charpy numbers. These results would mean M4-class toughness with s110v/10v class wear resistance. My money is on a slightly lower Charpy result of around ~25ft/lbs. at this hardness, placing K390 close to M390 as far as impact resistance goes.

Of course, this is all conjecture with a dash of slipshod detective work. This data is also for a hardness (61HRc) that is quite a bit lower than the usual target hardness of 10V ad K390, which is around 63-64HRc. Does anyone have any concrete data on K390's impact resistance (toughness)? Charpy c-notch results would be grand.
 
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Bump this decade old question because I'm curious too (I'm sure the OP has figured it out by now).

If calculating from 10V, Larrin plots 10V at 7-8 ft lbs (unknown test) across 61-65 Rc. If that's 75%, then K390 would calc to 9-11 ft lbs by that same test.

Anybody have better data?
 
Larrin Larrin wrote about it - in his article here https://knifesteelnerds.com/2021/10...ness-edge-retention-and-corrosion-resistance/

but here is the graph - m390 toughness is junk, as one should expect from steel with 2.5% carbon lol it's just too much imho, I won't touch it personally
stainless-toughness-10-19-21.jpg
 
sorry, the m390 got me confused --- thought I was looking at k390

funny how no 3rd party has done any direct testing... but bohler has this published: https://www.bohler-edelstahl.com/en/products/k390-microclean/

k390_diagramm2-768x380.jpg


Specimens taken from rolled steel bar in longitudinal direction, centre
Source material dimensions: 40.8 mm round
Specimen size: 7 x 10 x 55 mm per SEP 1314
 
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Yes Bohler has claimed that K390 has superior toughness to 10V but I haven’t seen independent testing to confirm or deny that. The K390 I used for CATRA testing was too thin for my standard toughness test. If someone can get me some 1/8” stock I can test it.
 
Thanks for the info everyone. After reviewing the info, an educated guess would probably put K390 somewhere between Vanadis 8 and S110V, maybe somewhere around ~10 ft-lbs (dependent on heat treat)?
 
Rooster81 said:
Thanks for the info everyone. After reviewing the info, an educated guess would probably put K390 somewhere between Vanadis 8 and S110V, maybe somewhere around ~10 ft-lbs (dependent on heat treat)?
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Between Vanadis 8 and 10V, yes.
 
Larrin said:
Between Vanadis 8 and 10V, yes.
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Thanks Dr. Thomas. Really enjoy all the data, history, and general info on your site. So much so that I ordered your book.

Kind of a side note, is your data available for download, for personal use? Basically I'm thinking it'd be great to have a spreadsheet with the actual numbers for each specific steel.

Regards.
 
Rooster81 said:
Thanks Dr. Thomas. Really enjoy all the data, history, and general info on your site. So much so that I ordered your book.

Kind of a side note, is your data available for download, for personal use? Basically I'm thinking it'd be great to have a spreadsheet with the actual numbers for each specific steel.

Regards.
Click to expand...
I’ve toyed with the idea of an interactive spreadsheet but I’ve never gotten around to actually doing it.
 
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