Cut testing, 3V heat treat, ELMAX, D2

alrob said:
Great thread,that little d2 knife deserves a proper handle though lol
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That's, uh, tactical uh, tape. It's, uh, 600V dielectric. So it's, uh, high speed low drag. 3M product, you know. It's, uh, "electrical"...

I think I made that prison shank for Rick Marchand. But then I had trouble shipping it to the Paleolithic Era...

...lol...
 
Fascinating stuff. Thank you both for bringing this up specifically regarding 3V (my favorite steel, if I could only have one).

I've been pleasantly surprised with Elmax's blend of toughness and edge-holding, too. The particle metallurgy aspect is the only explanation for it that I can think of... the stuff definitely works, though. I've been having mine tempered back to 58Rc, trying to maximize the toughness... I think I need to have some run at 60 or 62 and see how much I lose.
 
Nathan the Machinist said:
I think I made that prison shank for Rick Marchand. But then I had trouble shipping it to the Paleolithic Era...
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That's the one... remember I tried to smuggle it into the prison cafeteria and lost it for a day? I keep telling ya that I washed it... why you won't sell it, I don't know. You can brag that it went though cryo and bio treatments.
 
Rick Marchand said:
That's the one... remember I tried to smuggle it into the prison cafeteria and lost it for a day? I keep telling ya that I washed it... why you won't sell it, I don't know. You can brag that it went though cryo and bio treatments.
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That's the first and the LAST 'delivery' I make to you when you're inside.
 
Nathan the Machinist said:
That thread of yours is what motivated me to document this test for the forum in the first place. :thumbup:
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Thanks! but your thread is better,LOL..If it helps your thread about D2 that you did motivated me to try that heat treat with 3V and not be confined with "industry" specs..I found a whole new love for D2 after that.
 
Really fascinating stuff. Thanks for posting this. I just noticed you are practically in my back yard!
 
Thanks for the info. Nathan. When you say "rapid quench" I assume you mean plate quench. Please correct me if I'm wrong.
I've never been a fan of high temp. tempering in any steel. After talking with several knowledgeable people regarding high alloy steels I also believe that its best to keep the temp. moving either up or down after the quench. The only time it should be at a static temp. is during the soak in the tempering oven or in the ice bath/dewar. Otherwise the steel temp. needs to be either rising or falling until tempering is complete.
I guess the shorter way to describe it is not to let the steel sit on a shelf at room temp. waiting for the next step. Anyway, its good to know I've been doing something right. Even a blind hog finds an acorn every now and then right?
 
One more knifemaker here thanking Nathan for the info on D2 heat treat- "It doesn't behave like D2!"
I get a VERY nice edge on mine.
 
alfred mcdougal said:
Off to read more about RA!
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I'm convinced that RA is the Devil for cutlery purposes. It's clear to me that Nathan's tweaks to convert RA to stable martensite are a worthwhile improvement on steels that are frankly, already pretty dang good even with just "industry standard" HT :thumbup:

It's worthwhile to note that these tweaks don't seem to involve any extra expense or hocus pocus, just bearing in mind the concepts of continuous quenching and avoiding overly-high tempers.
 
Nathan, would you, or do you have a compilation of your test results and revised HT schedules hosted any place? After your D2 test I converted to your method from the industry standard... I don't use 3V much, but if I did I'd be changing that too after those results. And I second James' comment whole-heartedly.

I'm a nut for testing too, as I'm in the Murphy's Law camp when it comes to training and equipment. But I don't have the time or resources to come close to what you're able to accomplish. I don't know if I've said this before but I value your metallurgical opinion up there with the top of the heap. Especially since you test, test, and retest.

Thanks for posting this and all the other stuff up.

-Eric
 
Hmm... I was hoping to be more entertained by this thread...

:foot: ;) :D


Super thread Nathan!!! I really appreciate you taking the time to put this together... obviously it was a lot of work to do the testing and to document it for this thread!

Thanks man!!! :cool: :thumbup:
 
LucyCustomKnives said:
Nathan, would you, or do you have a compilation of your test results and revised HT schedules hosted any place?
-Eric
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No I don't. And I don't want to give the misimpression that there is this deep body of work that I've done that you're missing out on, there isn't.

Truly knowledgeable people like Kevin Cashen laid the ground work on this forum and set the tone and introduced me to resources that a dumb machinist can read and sort of understand. I wish he did more work in complex steels because I'm sure it would have saved me a lot of trouble trying to understand how to apply these things to my work.


About 10 years ago I ran into problems with D2 and the information I needed simply wasn't published (that I could find anyway) and practically all of the published information I could find was wrong (RA) or missing important details in a few areas important to fine edge stability, (the effects of normal variations in alloying and their effect on prequenching and success with a 2nd austenitizing, and hey there's a reason CPM D2 isn't a blockbuster). So without knowing what I was doing, but encouraged by some things that Cliff Stamp told me to try, I experimented with it until I got something that worked that I can explain now but I couldn't at the time and that contradicted the standard literature at the time. I'm vindicated by some of the current literature and folks like Roman who is now participating with us in America and say similar things, so rapid quenching an air steel to sub zero and avoiding the secondary hardening hump etc is no longer fringe. But I'm not one of the guys that thoroughly understands this stuff.

James,

Yes, RA is a bigger problem than people realized and it does play hell with fine edge stability. So for most of my work I want to keep it to a minimum. But I think it is important to realize that there can be benefits to it. Your blades warp less, and potentially crack less. Both in HT and in big knives. RA improves impact strength in thick sections. Something to think about. I like that my edges doesn't roll but I may have made that knife less durable than it might have been with more RA. There's a balance there and I don't honestly always know where it is. I shot this durability demonstration of the tweaked 3V this morning : http://youtu.be/IcovoTyGiRg . That's hellacious for a small thin knife so I'm going to call it good. But would a little RA make it even more durable and would the subsequent loss of edge durability be a good tradeoff? I know what judgment call I've made, but I have to recognize that it is simply a judgment call. *shrug*
 
Nathan the Machinist said:
I shot this durability demonstration of the tweaked 3V this morning : http://youtu.be/IcovoTyGiRg . That's hellacious for a small thin knife so I'm going to call it good. But would a little RA make it even more durable and would the subsequent loss of edge durability be a good tradeoff? I know what judgment call I've made, but I have to recognize that it is simply a judgment call. *shrug*
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Thanks for addressing that. As you've discussed before, RA is actually a good thing in pieces like dies...

I certainly agree, the impact strength is looking pretty darn good. I prefer a knife that rolls rather than breaks out in chunks, so I really like what I'm seeing there - very little chipping or deformation.

I'm also interested in lateral/prying type toughness, and how/whether RA might affect that. For some applications, I would be happy to accept "normal" edge durability in 3V if it means greater resistance to snapping off the tip in abusive situations.

Another question I have is, have you re-sharped those two 3V blades yet, and can you tell a difference between them? I'm wondering, since the steel matrix is at the same overall Rc hardness and the carbide content is the same, what effect does RA have on pure wear-resistance?

I realize that may be pretty hard to ascertain and document just by sharpening a knife or two, but clients do love to ask "how easy is this knife to sharpen?", so I thought I'd throw it out there.
 
Nathan the Machinist said:
No I don't. And I don't want to give the misimpression that there is this deep body of work that I've done that you're missing out on, there isn't.

Truly knowledgeable people like Kevin Cashen laid the ground work on this forum and set the tone and introduced me to resources that a dumb machinist can read and sort of understand. I wish he did more work in complex steels because I'm sure it would have saved me a lot of trouble trying to understand how to apply these things to my work.


About 10 years ago I ran into problems with D2 and the information I needed simply wasn't published (that I could find anyway) and practically all of the published information I could find was wrong (RA) or missing important details in a few areas important to fine edge stability, (the effects of normal variations in alloying and their effect on prequenching and success with a 2nd austenitizing, and hey there's a reason CPM D2 isn't a blockbuster). So without knowing what I was doing, but encouraged by some things that Cliff Stamp told me to try, I experimented with it until I got something that worked that I can explain now but I couldn't at the time and that contradicted the standard literature at the time. I'm vindicated by some of the current literature and folks like Roman who is now participating with us in America and say similar things, so rapid quenching an air steel to sub zero and avoiding the secondary hardening hump etc is no longer fringe. But I'm not one of the guys that thoroughly understands this stuff.

James,

Yes, RA is a bigger problem than people realized and it does play hell with fine edge stability. So for most of my work I want to keep it to a minimum. But I think it is important to realize that there can be benefits to it. Your blades warp less, and potentially crack less. Both in HT and in big knives. RA improves impact strength in thick sections. Something to think about. I like that my edges doesn't roll but I may have made that knife less durable than it might have been with more RA. There's a balance there and I don't honestly always know where it is. I shot this durability demonstration of the tweaked 3V this morning : http://youtu.be/IcovoTyGiRg . That's hellacious for a small thin knife so I'm going to call it good. But would a little RA make it even more durable and would the subsequent loss of edge durability be a good tradeoff? I know what judgment call I've made, but I have to recognize that it is simply a judgment call. *shrug*
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Well, I too consider Kevin and his kinsmen up there in the stratosphere and a source for a lot of what I know, but from my POV there is quite a lot of stratification in the metallurgical world. There are those that have learned from reading and doing, and are at a point where they are actively tweaking, testing, reevaluating what we do and then hopefully passing that knowledge down the line. Then there are those who are learned, have learned and are experimenting with maybe one steel, or one Ti alloy at a time while still working to learn more about other alloys etc. They too are hopefully teaching that to the rest of us.

Honestly I consider you in the next tier down from that. Definitely higher up that ladder than most. Taking what is and what just recently was fringe thinking with our craft and putting it to the test. And I know, in your case you are passing it down the line to the rest of us. Your testing is thoroughly documented and following the scientific method better than most, hence why I wondered if there was a repository of the datum from that somewhere aside from here. Don't confuse that with thinking I am not satisfied with what you have posted here, as I said your test with D2 was at leaet enough to sway me from the commonly posted schedule. Thanks for that. And don't think so diminutively about your position, I know a lot of us here look up to you especially when concerning the machining of metals, as we also look up to Stacy, Nick, Page, James, Rich, Frank, Salem, Charlie, et al (not trying to leave anyone out just not gonna list you all. You hopefully know who you are...) for each thing that they offer. I'll encourage you to continue to do your tests and post them up. Like I said above, they are appreciated by those of us who don't have the time or resources to do so ourselves.

And I think that's the goal and the great resource this place is. Maybe I can spend a lot of time doing/making and testing item X. And you can do item Y. Throw in a few more makers who focus on things we do not, and you can round out your skillset pretty quick. I know it isn't quite the same as doing it, but I know a thorough WIP or How To can get me past a whole lot of crap I may F up if I didn't have that knowledge. That saves me time. And my shop time is valuable as I don't get near as much of it as I need. And I also suspect it is the reason for the very high standard set these days, and the outstanding 'firsts' seen fairly commonly around here as well.

So I guess it's really a thank you to all of you who contribute what you do. I consider myself pretty versed, and pretty handy, but always like the opinions of those who are vastly more so.

-Eric
 
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Thanks for this great thread!So do you mean the type A HT is quench at a relatively low temperature than the inustry HT,and immediately cryo treatment without any quick temper to make it minimum RA .Then you select the lower temper temperature to avoid the secondary hardening hump.Is this the type A,and Type B is in the same quenching temperature as type A?but in a higher temper temperature by secondary hardening to reach the same hardness at 60HRC.

Your testing shows the Tpye A performs better in every project,so If I can come to the conclusion that the quenching then cryo immediately to minimum the retain austenite can refined grain ,so the toughness is better.

J.bin
 
nextmission said:
Thanks for this great thread!So do you mean the type A HT is quench at a relatively low temperature than the inustry HT,and immediately cryo treatment without any quick temper to make it minimum RA .Then you select the lower temper temperature to avoid the secondary hardening hump.Is this the type A,and Type B is in the same quenching temperature as type A?but in a higher temper temperature by secondary hardening to reach the same hardness at 60HRC.

Your testing shows the Tpye A performs better in every project,so If I can come to the conclusion that the quenching then cryo immediately to minimum the retain austenite can refined grain ,so the toughness is better.

J.bin
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No, not exactly. There is no grain refinement that I'm aware of and I have no reason to believe that the gross toughness is improved. The tweaks are being done to improve edge toughness, or specifically edge stability. And for that it clearly works.

What is all boils down to is avoiding the secondary hardening hump because that reduces the strength of the martensite in the matrix and instead brings the hardness back up with a combination of RA conversion and precipitation of secondary carbides. And, while RA conversion is a good thing, using the secondary hardening hump to achieve that gives you carbon lean martensite and a larger secondary carbide fraction, both of which reduce edge stability. So, to avoid the need for the secondary hardening hump we're addressing the RA by maximizing strain energy going into Mf with a rapid quench and no snap temper in the middle of the quench. We can deviate from the industry standard HT in this way because the relatively thin even section of a knife blade, particularly one with no sharp corners, will tolerate it whereas a stamping die (which 3V was developed for) will not due to dimensional changes (that we care nothing about) and tendency to crack (which is not a danger in our section).

Reduced RA, stronger martensite and fewer carbides probably increases the total strength of the matrix, it certainly improves the strength of the edge, but this may come at the cost of impact resistance. It certainly would on a thick part like a stamping die, but thin things like knife blades behave a little different in impacts. A big fat dies needs local yielding in the case of a large impact and RA acts like little circuit breakers preventing a gross failure. A knife is much thinner and more flexible and reacts differently to large impacts so it may be possible that the RA that is helpful in thick sections may be less importaint in thinner sections - I don't know.

I did do this durability demonstration of the tweaked 3V to show that it appears to have retained the considerable gross toughness 3V is known for: http://youtu.be/IcovoTyGiRg That a relatively thin blade at HRC 60 will do that says a lot about CPM 3V.
 
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