BCMWn690

HeavyHanded

HeavyHanded

Joined
Jun 4, 2010
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Had a chance to run a SuperQuench n690 on the Edge Inquisitor for some initial numbers. Edge was finished on 4k Norton waterstone, test rope is 3/8 Manila.

Edge was breezing through newsprint and shaving to the clean.

10lbs of static load with 2" of travel it managed 92 passes before skipping three in a row, this puts it more or less in line with BarkRiver n12 on this device.

Initial push cut was an impressive 12.5 lbs, even after reaching failure for the draw cut test it still made a pressure cut with 16 lbs. I intend to resharpen and retest but might be a few days and will include a few pics. Grind work on the blade is top notch in terms of geometry and aesthetics.

Martin
 
The Bark River made 86 and 98. Deviation on this unit is not very much, so confidently I'd imagine a second run would be close to the first, maybe a 10-15% deviation, usually upward. If its off more than that in either direction I'll run a third test.

I didn't have my stones at the bench today, so will have to take it home, touch it up and retest on Wednesday. Takes a wicked catchy edge!

Also, I cannot recall the RC of the n690, 62 rings a bell...
 
63-64 on N690? Just making sure I understand that correctly. Non of the information I have ever seen on N690 states that HRC is even possible. What heat treatment protocol did you use?
 
I should make a couple more of n690 knives and keep better experiment notes. I didn't transfer hrc# @ temp from (what written on) blade to lab-note then to document.

Like many mid to high alloy steels, there is plenty of carbon available. So just matter of put enough C in solution, prevent carbide precip while in aust and induce low RA%. BCMW ht includes high aust temp + super quench + cryo + low temper and other steps.
marthinus said:
63-64 on N690? Just making sure I understand that correctly. Non of the information I have ever seen on N690 states that HRC is even possible. What heat treatment protocol did you use?
Click to expand...
 
And the traditional plate quench allows MC precip? What about warm medium speed oil? You think THAT would allow MC precip as well? What makes you think a brine solution is the correct way to deal with carbide precip in such a steel?
 
Not MC but Cr7C3 + variations precip due to race toward elements fraction equilibrium along the cooling curve. At end of soak at aust temp has certain equilibrium (and distribution) of elements. Higher temperature = more energy(aust dislocation) and higher instability of solution during cooling. I use SQ to minimize this cooling time from aust to near Ms phase. Cooling is quite tricky when aust matrix excessively saturated with carbon. e.g. N690 aust 2000+F 20-30minutes soak, precip is a primary and RA is secondary problem. Hence, must take care both problems, otherwise end up with poor result. Of course, my ht try to produce lath martensite as well (plate martensite is a 3rd problem).

samuraistuart said:
And the traditional plate quench allows MC precip? What about warm medium speed oil? You think THAT would allow MC precip as well? What makes you think a brine solution is the correct way to deal with carbide precip in such a steel?
Click to expand...
 
Brine quenching N690 to prevent carbide precip and to create lathe martensite??? I'm not a metallurgist, but I would think superquenching such an alloy steel to prevent carbide precip (or any reason) is just asking for it. You are able to get away with this? No stress cracks? Are you able to check for this in the microstructure? I recall you SQ 52100 and CFV, with cracks in your samples.
 
...ecc...
samuraistuart said:
brine quenching n690 to prevent carbide precip and to create lathe martensite??? I'm not a metallurgist, but i would think superquenching such an alloy steel to prevent carbide precip (or any reason) is just asking for it. You are able to get away with this? No stress cracks? Are you able to check for this in the microstructure? I recall you sq 52100 and cfv, with cracks in your samples.
Click to expand...
 
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Quick update on this blade and some pics. Disclaimer, the handle is my own work, based on an end for end symmetrical concept for EDU knife but I applied it to this one that Luong supplied with a blank handle. I include these to show the very nice grind work on the blade and for reference, not to show off my wood-working... :eek:

I had suspicions following the last test that based only on RC, the edge should have held up longer, add the fact that in the past my Norton waterstone had trouble making longer lasting edges on higher alloy steel. So, used a Washboard with 800 grit wet/dry instead, finished with some stropping/burnishing on plain paper. Under the loupe and for impromptu cutting these edge finishes look and behave very similar, but there were some differences making me believe the 4k Norton is a fair amount more refined than the 800 wet/dry.

Initial static load for a pressure cut was 17lbs. Static load for a pressure cut upon finishing was 30 lbs - so a notable shift from the first numbers, though anything under 20lbs initially is pretty good for this test. Also, it now completed 158 passes before failing three in a row, a very large difference necessitating a third round of testing early next week.

The new number puts it much further up the chart than the initial value.

BCMW_N690_zpsa2wwa7nu.jpg~original


BCWM_N690_2_zps6blh7w2h.jpg~original
 
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Martin, I am sure the handle is very comfortable to use. :thumbup:
The grind is indeed very nice, is it tapered to very thin tips?

On the performance, can you help explaining the performance difference, perhaps I can pick up my lesson for VG10 ...
 
Chris, do you mean the diff between the 4k Norton and the 800 wet/dry, or this steel vs others I've tested?

It distal tapers to a very thin tip. Being mostly used to BCMW trial run knives, the aesthetic and functional quality of the grind is first rate.

I find it very interesting that the initial and finishing pressure cutting numbers were off that far. Cutting newsprint, three finger sticky, shaving a bit of arm hair all seemed very similar. Also, the longevity numbers followed inverse.

I noticed in my initial set-up of the Edge Inquisitor that across several steel types too high a polish did not cut well at 10lbs/2" draw, nor did too low of a finish. So there are some (currently) sparse but interesting performance metrics that indicate (to me) my gut feelings about 600-800 grit finish edges being best for EDU draw/press intersection are somewhat validated. I haven't been keeping these numbers religiously as I went, I need to be better disciplined about this in the future.

The N690 at this RC sharpened up with less burring compared to Spyderco VG10 though still more than one might expect from other steels at >60 RC, especially compared to plain carbon steels.

This steel makes for a real catchy edge at medium high finish, but also very good push cutting. Around the kitchen it held up very well even with lots of pulling cuts on the board. I would be very happy with one of these in a Chef's pattern and hope Luong considers that - for the performance characteristics of his HT and the RC values, a big chopper with super thin geometry would seem to be a perfect fit. In that role I'd likely move to a brighter finish and go right to 6k-8k JWS.
 
Martin - you sure did a good job sculptured an artistic handle:thumbup: I like how it could be comfortably cradle in hand and firmly stay in fast slash & stab actions.

Good to see your finding high correlation between edge refinement/grit finished and retention testing with your EI2000 rig. 'Refinement' probably more accurate than grit because hardness; carbide volume+type; edge geometry (implicit pressure); abrasive type+size - are major factors determine the edge refinement (irregularities: amplitudes+frequency+constituent of protruding parts)

I am still in tinkering-mode with stainless steels with carbon > 0.9% :p

For stainless steel with carbon between 1.0-1.2%, I would like to try CTS-B75 and RWL-34. 1.5% Cobalt in N690/VG-10 sure help with high working hardness.
http://zknives.com/knives/steels/st...,CPM154,VG-10&ni=,1410,521,52,4001&hrn=1&gm=0

SS 1.4-1.5%C: cts-xhp
SS 1.6-2%C: elmax & 20cv/m390
SS 2+%C: s110v
 
bluntcut said:
Martin - you sure did a good job sculptured an artistic handle:thumbup: I like how it could be comfortably cradle in hand and firmly stay in fast slash & stab actions.

Good to see your finding high correlation between edge refinement/grit finished and retention testing with your EI2000 rig. 'Refinement' probably more accurate than grit because hardness; carbide volume+type; edge geometry (implicit pressure); abrasive type+size - are major factors determine the edge refinement (irregularities: amplitudes+frequency+constituent of protruding parts)

I am still in tinkering-mode with stainless steels with carbon > 0.9% :p

For stainless steel with carbon between 1.0-1.2%, I would like to try CTS-B75 and RWL-34. 1.5% Cobalt in N690/VG-10 sure help with high working hardness.
http://zknives.com/knives/steels/st...,CPM154,VG-10&ni=,1410,521,52,4001&hrn=1&gm=0

SS 1.4-1.5%C: cts-xhp
SS 1.6-2%C: elmax & 20cv/m390
SS 2+%C: s110v
Click to expand...

Agreed, I generally refer to edges in a bunch of scales but most often ANSI or CAMI standards. One of the best things about those standards in regards to wet/dry, is different makers silicon carbide "A" weight papers will all be very similar and usually do a consistent job on many steels. Possibly allowing others to duplicate with some confidence a described finish...

Once you get into finer finishes, using waterstones, dealing with high Vanadium content or large carbides, the "grit" value and edge produced will begin to vary more from sample to sample (in my experience).

So I try to refer to stuff as being "extra coarse, coarse, medium, medium fine, fine, extra fine" etc. More of an impression unfortunately. If I'm diligent with my note taking, I should be able to come up some good intersection values and see where they fall with various steel types as prep'd by me. Always coming up with new ways to keep me honest!
 
Martin,

Thank you. It's this steel from earlier test and later one when finished differently.
It seems the general sharpness test by feel and light use (three fingers sticky and slicing paper) wouldn't tell the full story of how the edge and apex will behave during more extended use.

I recalled discussion with Jason on polished bevel + coarser microbevel VS coarser bevel vs polished microbevel. In his opinion, the coarser bevel with more polished microbevel lasts longer in random EDU duty.

I'm feeling that there's still so much to learn .. Sorry for OT on this.
 
Chris, that goes with what I have found. Years ago I used to do the fine polish and few passes on coarse diamond. Then found no difference between just stopping at the coarse diamond. Then learning various microbevel methods on coarse edge. This lets you touch up a number of times before needing to recondition the edge.

With a bit of noodling you can also find the finish this most approximates and go right to that, maintain at a constant level. A zillion variations that work. I need to do a lot more with my EI3K widget as it really is a nice tool to detect subtle start/stop cutting effects and direct compare to pressure/draw results at given finish.
 
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