Competition Chopper M4, 3V, or Z-Wear

Kevin McGovern said:
Nathan,

When you say "relatively fast quench" are you talking aaa? also, when you refer to cryo, is DI bath cold enough, or is LN2 required?
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I won’t speak for Nathan , but plate quench is fast enough, from what I understand. And dry ice is ok, but Ln is better, plus you don’t get eta carbides with dry ice!
 
ShannonSteelLabs said:
Hopefully I will be making a competition knife in Zwear for 2019. Still need to come up with a design and grind it out. But I will likely be using a low temper as suggested by Willie71 Willie71

Currently sent another camp knife there to test the low temper.
Willie71 Willie71 this should hopefully be an awesome test!
Click to expand...


Even the 1975/cryo/400f temper protocol gave up nothing in toughness to lower temp heat treats in terms of toughness (see Larrin’s Charpy testing.) I’ve had zero knives returned with chipped edges or any form of damage, and a few users have told me the accidentally hit steel or rocks with the fine edges, with no damage. One user skinned four gritty moose, and it still shaves hair. One user used an Rc63 knife as a throwing knife. Didn’t even break the tip. This stuff is amazing with the standard heat treat, and just that bit better with the low temper protocol.

I’ll try to push the hardness up a few more notches, and send samples to Larrin to see when the toughness drops.
 
rodriguez7 said:
I won’t speak for Nathan , but plate quench is fast enough, from what I understand. And dry ice is ok, but Ln is better, plus you don’t get eta carbides with dry ice!
Click to expand...

It depends on the knife. My quench rate was fine with plates in my development work but it was done on this pattern that was relatively thin and had big parallel flats that really lends itself to plate quenching:

11.jpg~original


That pattern ended up being a test mule for my 4V V4E development work. But the real purpose of that work was a comp chopper:


^that pattern does not plate quench effectively. There's almost no contact out in the blade. My attempts to heat treat those here with plates didn't work as well as the test mule. This illustrates the importance of testing, evaluating with control samples (standards) and reproducible test processes. Imagine how bad it would have been to assume I'd get the same results.

I think a slow oil isn't a bad idea (and I wouldn't interrupt at 900, I might go all the way to Ms) but we ended up using a modified process

As far as dry ice or LN, I use LN. Could you figure out a workable process with dry ice? possibly. Would it be optimal? Probably not.

rodriguez7 said:
plus you don’t get eta carbides with dry ice!
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I expect most custom makers aren't getting much eta carbide with LN either. In my opinion most makers using LN aren't using it for much more than completing the quench. However that's one of its most important functions.
 
I suspect that the martensitic structures that form in the quench are not completely cohesive to the martensite that forms during and after temper, hence the need to use LN and complete the quench without delay. I haven't ready this anywhere and I'm not a metallurgist, I'm just basing this theory as a possible explanation for things I have observed, so I could be totally off.

I think that something like an 80% martensite (that would be pretty typical) going into temper softens at the edges and moves carbon and the RA conversion and new martensite does not interact with the original structures the same as if it were all formed at the same time. I think that experimental heat treats like Luong (Bluntcut) has done is interesting because the very high amount of RA going into temper and the subsequent formation of martensite from tempering is another way (perhaps a better way?) of achieving the same thing, which is a structure that is largely formed complete and at the same time. I think this contributes to the combination of strength and ductility necessary for edge stability in thin sections. Mixed structures (and I consider converted RA to possibly be part of that) play hell in a thin edge, the same as perforations in a sheet of postage stamps.

Regardless, wonky theory aside, it is a demonstrable fact that completing the quench as a smooth continuous reduction in temperature down to Mf (wherever that may be) is important to the durability of an edge, particularly in a thin section. And even if the finished amount of RA is the same for LN or DI, I think LN might do a better job of doing it the first time.
 
Eta carbide is much different than other regular secondary carbide. For starters is it much smaller and can be much more plentiful (numerically, not in volume). And it's function is not like most carbide, to enhance abrasion resistance, but rather to pin "the grid". This is why heating it up ruins it. The little carbide is still there, but the matrix around it relaxes so it looses its effect. The beauty of eta is it doesn't propagate cracking like a normal carbide, but it might actually help arrest them.

Contrary to some misconception it is not formed during cryo. Well, some of it might be formed during cryo because as the highly tetragonal pure un-tempered martensite contracts the elongated crystals might actually squeeze and "pop" a carbon atom out (cryogenic tempering) where it might react (even at that low temperature) in a non-metallic bond to a surrounding metal (iron, chrome whatever) and form a nanoscopic cementite or whatever, but the real formation of eta carbide happens in temper. It is the changes to the lattice caused by cryo that enable that (tiny little gaps from minute rearrangement), but it is not as simple as just dunking your knife into LN and TADA! eta. These gaps require movement and movement requires time. A quick dunk into LN runs across these temperatures where thing can and will move too quickly, it takes a little more time and temp control than that. If you're a custom knife maker using LN and you'd like to experiment with eta carbide formation you would experiment with your quench rate going down and back up and the timing and number of your cryo and temper steps. I think eta carbide is a poorly understood subject that may or may not be important to knife makers. I don't know much about it except that one steel does not react the same as another. Since most of us don't have an SEM in our shop (I don't) we're really just throwing darts in the dark. Hence the need to experiment with reproducible testing techniques. At the end of the day it may not matter why your process works, just as long as it does and you can reproduce it. But I suspect that eta carbide might be an important ingredient in the soup.
 
Would a set of plates with a hinge on one side holding the plates in a v, like a book, work for quenching large blades like choppers or kitchen knives? You couldn’t quench the ricasso or tang very well this way, but the blade and edge would have good contact. It would be nice to do some grinding pre heat treat on high vanadium steels to keep belt costs down.
 
Willie71 said:
Even the 1975/cryo/400f temper protocol gave up nothing in toughness to lower temp heat treats in terms of toughness (see Larrin’s Charpy testing.) I’ve had zero knives returned with chipped edges or any form of damage, and a few users have told me the accidentally hit steel or rocks with the fine edges, with no damage. One user skinned four gritty moose, and it still shaves hair. One user used an Rc63 knife as a throwing knife. Didn’t even break the tip. This stuff is amazing with the standard heat treat, and just that bit better with the low temper protocol.

I’ll try to push the hardness up a few more notches, and send samples to Larrin to see when the toughness drops.
Click to expand...
I’m going to be trying this heat treat for a customer this week. I’ve never heat treated zwear. I’m actually excited to try it. I may build me a small caper for my elk hunt to try out!
 
Nathan the Machinist said:
Eta carbide is much different than other regular secondary carbide. For starters is it much smaller and can be much more plentiful (numerically, not in volume). And it's function is not like most carbide, to enhance abrasion resistance, but rather to pin "the grid". This is why heating it up ruins it. The little carbide is still there, but the matrix around it relaxes so it looses its effect. The beauty of eta is it doesn't propagate cracking like a normal carbide, but it might actually help arrest them.

Contrary to some misconception it is not formed during cryo. Well, some of it might be formed during cryo because as the highly tetragonal pure un-tempered martensite contracts the elongated crystals might actually squeeze and "pop" a carbon atom out (cryogenic tempering) where it might react (even at that low temperature) in a non-metallic bond to a surrounding metal (iron, chrome whatever) and form a nanoscopic cementite or whatever, but the real formation of eta carbide happens in temper. It is the changes to the lattice caused by cryo that enable that (tiny little gaps from minute rearrangement), but it is not as simple as just dunking your knife into LN and TADA! eta. These gaps require movement and movement requires time. A quick dunk into LN runs across these temperatures where thing can and will move too quickly, it takes a little more time and temp control than that. If you're a custom knife maker using LN and you'd like to experiment with eta carbide formation you would experiment with your quench rate going down and back up and the timing and number of your cryo and temper steps. I think eta carbide is a poorly understood subject that may or may not be important to knife makers. I don't know much about it except that one steel does not react the same as another. Since most of us don't have an SEM in our shop (I don't) we're really just throwing darts in the dark. Hence the need to experiment with reproducible testing techniques. At the end of the day it may not matter why your process works, just as long as it does and you can reproduce it. But I suspect that eta carbide might be an important ingredient in the soup.
Click to expand...
Thanks for weighing in! It’s always good to hear from you on these things. I’ve learned a hell of a lot from your posts!
 
Willie71 said:
Would a set of plates with a hinge on one side holding the plates in a v, like a book, work for quenching large blades like choppers or kitchen knives? You couldn’t quench the ricasso or tang very well this way, but the blade and edge would have good contact. It would be nice to do some grinding pre heat treat on high vanadium steels to keep belt costs down.
Click to expand...
Would be something to try!
 
Nathan the Machinist said:
I suspect that the martensitic structures that form in the quench are not completely cohesive to the martensite that forms during and after temper, hence the need to use LN and complete the quench without delay. I haven't ready this anywhere and I'm not a metallurgist, I'm just basing this theory as a possible explanation for things I have observed, so I could be totally off.

I think that something like an 80% martensite (that would be pretty typical) going into temper softens at the edges and moves carbon and the RA conversion and new martensite does not interact with the original structures the same as if it were all formed at the same time. I think that experimental heat treats like Luong (Bluntcut) has done is interesting because the very high amount of RA going into temper and the subsequent formation of martensite from tempering is another way (perhaps a better way?) of achieving the same thing, which is a structure that is largely formed complete and at the same time. I think this contributes to the combination of strength and ductility necessary for edge stability in thin sections. Mixed structures (and I consider converted RA to possibly be part of that) play hell in a thin edge, the same as perforations in a sheet of postage stamps.

Regardless, wonky theory aside, it is a demonstrable fact that completing the quench as a smooth continuous reduction in temperature down to Mf (wherever that may be) is important to the durability of an edge, particularly in a thin section. And even if the finished amount of RA is the same for LN or DI, I think LN might do a better job of doing it the first time.
Click to expand...
What kind of delay between plates to LN would be adequate? What would be to long? I usually plate quench for 40 seconds in the plates, then remove the foil and let the blades air cool for around an hour, then into LN.
 
I wouldn't wait an hour to get it into LN. I also wouldn't dunk it straight into LN. You want a smooth continuous quench to Mf without pause.
 
Nathan the Machinist said:
I wouldn't wait an hour to get it into LN. I also wouldn't dunk it straight into LN. You want a smooth continuous quench to Mf without pause.
Click to expand...
I usually don’t wait quite that long, after they’re cool I usually put them in the freezer, then I ease them into the LN. Just the other day, I had to much going on, and had them hanging for around an hour before LN.
 
rodriguez7 said:
I’m going to be trying this heat treat for a customer this week. I’ve never heat treated zwear. I’m actually excited to try it. I may build me a small caper for my elk hunt to try out!
Click to expand...

Take your edge down to 0.005” before sharpening. For that application, you are fine that thin.
 
Willie71 said:
Even the 1975/cryo/400f temper protocol gave up nothing in toughness to lower temp heat treats in terms of toughness (see Larrin’s Charpy testing.) I’ve had zero knives returned with chipped edges or any form of damage, and a few users have told me the accidentally hit steel or rocks with the fine edges, with no damage. One user skinned four gritty moose, and it still shaves hair. One user used an Rc63 knife as a throwing knife. Didn’t even break the tip. This stuff is amazing with the standard heat treat, and just that bit better with the low temper protocol.

I’ll try to push the hardness up a few more notches, and send samples to Larrin to see when the toughness drops.
Click to expand...
Thanks!!
Maybe I will call up Brad and see if he can do that.
I'm just trying to get the best possible HT for the project. Obviously this will be a process to get it dialed in. And I dont have an oven to mess with heats.

How many tempers? 3 or 4?
 
ShannonSteelLabs said:
Thanks!!
Maybe I will call up Brad and see if he can do that.
I'm just trying to get the best possible HT for the project. Obviously this will be a process to get it dialed in. And I dont have an oven to mess with heats.

How many tempers? 3 or 4?
Click to expand...

I’m doing four. Larrin said the difference is results could be just noise in the data. The four temper samples had less variance is toughness than the samples with two or three tempers. I should do larger batches to tease this out.
 
Willie71 said:
I’m doing four. Larrin said the difference is results could be just noise in the data. The four temper samples had less variance is toughness than the samples with two or three tempers. I should do larger batches to tease this out.
Click to expand...
Got my blade back from heat treat and did some testing.
Came back at 63HRC (as tested by Brad at PHT)
I had asked for 3 or more tempers. Hoping for 4. He had told me that 2 was always standard. No way for me to tell if he did more than 2.

I did a bunch if testing this past weekend camping. Batoning and chopping hardwood, whittling cutting up food. Full convex grind, and 600 grit edge and stripped with 1 micron diamond emulsion. Scary sharp! This steel really wants to get sharp. Sharpens up much different than the 62HRC with standard HT.

One or 2 tiny nicks in the edge appeared over the weekend. I'm sure it was from the chopping or batoning. But other than that it stayed shaving sharp the whole time. Got back home and restropped it. Black, white, and finished on green. Retested it. No dings in edge, back to scary sharp.

I will definitely be using the 63HRC Zwear for blade sports. Very impressed.
I have a playlist on my YouTube channel. Labeled Vermont camping with Zwear I believe. (YouTube gave me issues last night couldn't make one long vid, so many many small ones)
 
ShannonSteelLabs said:
Got my blade back from heat treat and did some testing.
Came back at 63HRC (as tested by Brad at PHT)
I had asked for 3 or more tempers. Hoping for 4. He had told me that 2 was always standard. No way for me to tell if he did more than 2.

I did a bunch if testing this past weekend camping. Batoning and chopping hardwood, whittling cutting up food. Full convex grind, and 600 grit edge and stripped with 1 micron diamond emulsion. Scary sharp! This steel really wants to get sharp. Sharpens up much different than the 62HRC with standard HT.

One or 2 tiny nicks in the edge appeared over the weekend. I'm sure it was from the chopping or batoning. But other than that it stayed shaving sharp the whole time. Got back home and restropped it. Black, white, and finished on green. Retested it. No dings in edge, back to scary sharp.

I will definitely be using the 63HRC Zwear for blade sports. Very impressed.
I have a playlist on my YouTube channel. Labeled Vermont camping with Zwear I believe. (YouTube gave me issues last night couldn't make one long vid, so many many small ones)
Click to expand...

I agree that the low temper protocol takes an edge very easily, almost as easily as W2 or 52100. Plus, it holds that edge for a very long time.

I’m glad the blade performs as you expected it to.
 
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