Cut testing, 3V heat treat, ELMAX, D2

Nathan - but if you just cryo to get to Mf and then temper at 205°C, you treat 3V just like any tool steel.
Aren't you "wasting" alloying elements then?
Or do you expect all Mo and V to appear in form of M2,4C after low temperature tempering?
 
idaho said:
Nathan - but if you just cryo to get to Mf and then temper at 205°C, you treat 3V just like any tool steel.
Aren't you "wasting" alloying elements then?
Or do you expect all Mo and V to appear in form of M2,4C after low temperature tempering?
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I don't know.

I expect that the majority of the vanadium remains locked up in carbide, and in fact are probably largely unaffected primary carbides. Without raising the austenitizing temperature I'm not sure we're effecting V much at all.

Mo, I have no idea. I've read that free moly improves pitting resistance. Wasted? Probably. *shrug*

I believe that chromium carbides require the least amount of energy to dissolve, and chromium tends to be a major secondary carbide former. So I expect that chromium is effected more than the other alloying. After a certain extent, depriving the chromium of carbon probably helps edge stability by reducing carbide fraction and probably improves corrosion resistance by allowing more free chrome. I expect this is one of the primary mechanisms that avoiding the secondary hardening hump improves edge stability. Is the chrome wasted? I've read that to a certain point the chrome increases strength, but I don't know why. I do know the 3V is nearly stainless and won't take an etch for me and I expect the free chrome is the reason.

I think you raise a good question. By heat treating a steel differently than it was designed to, does that mean a different chemistry could be more optimal for the application? For example, would a low Mo version of 3V perform better if it is going to be heat treated this way? I don't know the answer to that question. What I do know is that 3V has properties that I wanted in this knife and in my testing those properties are still present after the tweak and a weakness in edge stability that I believe is probably almost universal in secondary hardening steels has been avoided. So, I have come to the conclusion that just because a steel has alloying that creates a secondary hardening hump doesn't mean you have to use that secondary hardening. What roll then does that alloy play is a question for someone like Roman, not me. Sorry, I wish I could be more helpful.
 
My guess is that neither the chrome, vanadium nor molybdenum are being "wasted" by this procedure.

It's important to remember that Cr and Mo aren't just there for carbide formation; even in small amounts they have a positive affect on hardenability (avoiding the need for a severe water or oil quench). That's not being wasted here.

They also add to corrosion resistance, so if Nathan is getting the balance of hardness and carbides he needs with a little free chrome and moly left over, that's certainly not wasted.

As for vanadium... again, it appears this process is developing plenty of small very hard V carbides for wear-resistance, and the V is still doing its job of keeping grain structure small and even for toughness... no waste there.

It seems that rather than "wasting" any of the alloy present in the steel, this process is actually making more efficient use of them for this specific application - well-balanced edge stability.

I have some thoughts on how to explore whether or not that's true, but they're just thoughts at this point... ;)
 
I think there is one more thing.
High speed steels - such like 3V (it exactly fills all requirement of hss standard in Poland) starts with much finer grain (16 up to 22) than tool steel and carbon steel.
With usual high temp austenitizing and tempering grain number falls down to usual values (8 to 12 i would say), while with Nathan way grain will stay small.
 
idaho said:
I think there is one more thing.
High speed steels - such like 3V (it exactly fills all requirement of hss standard in Poland) starts with much finer grain (16 up to 22) than tool steel and carbon steel.
With usual high temp austenitizing and tempering grain number falls down to usual values (8 to 12 i would say), while with Nathan way grain will stay small.
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3V looks a lot like a HSS to me. The techniques and assumptions I'm using have been validated with M2, which has a lot of similarities.

That said, this approach has no effect on grain size, austenitizing time and temp are middle of the road and there is no prequench. I expect it is probably in the neighborhood of 12-14, though I have no way to measure it. I'm not aware of any steel that goes to 22, so we may be talking about different standards.

M2 and D2 are both candidates for prequenching for grain refinement, but in my experience CPM D2 grain size explodes when you try that which is one reason I leave it alone. So based upon that experience I'm leery of trying that with 3V because I'm not equipped to quantify it and I expect similar mechanisms (small carbides) are at play.

Also, within reason, the effect of grain size is easy to over state. Very fine is fine enough for all intents and purposes. I've found what I believe to be advantages to prequenching beyond grain refinement but I don't have a solid hypothesis for what I believe I see so I will leave that alone here.
 
Im not talking about grain refinement, I'm saying that with hss you start with much finer grain. I will try to find proper literature-source material. Cant find any right now...
 
One more question :)

The HT guidelines for some steel says that you should do temper BEFORE steel reaches room temperature (it is not a case in 3v, but is in d2). It protects us from quench cracks
On the other hand it is good to make sub-zero treatment just after quench(in fact as a part of quench). So it is quite the opposite.

Or maybe that first guideline is mainly for large complicated shapes? punching dies and so on?
 
idaho said:
One more question :)

The HT guidelines for some steel says that you should do temper BEFORE steel reaches room temperature (it is not a case in 3v, but is in d2). It protects us from quench cracks
On the other hand it is good to make sub-zero treatment just after quench(in fact as a part of quench). So it is quite the opposite.

Or maybe that first guideline is mainly for large complicated shapes? punching dies and so on?
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Yup, and this is why D2 processed to industry standard guidelines doesn't work very well in a knife edge.

That was one of my points with this thread, to illustrate that some of the industry standard HT guidelines are wrong when applied to cutlery. A knife blade has a relatively uniform cross section, and unlike a stamping die, won't have large sections that cool at a much slower rate and go through the difference phases at hugely different times and try to crack.

In most cutlery applications you shouldn't do any kind of temper, or even a pause or delay, until you've reached Mf. "Room temperature" is a human construct that is meaningless to steel and should have no bearing on what we're doing unless we just happen to be using a steel whose Mf happens to be room temperature.
 
I wrote "room temperature" because I was to lazy to calculate 50-70°C into °F :)
 
Nathan, I would like to know your austenitizing temperature and quench media, thank.
 
I've been working on this a lot over the last few weeks, tweaking 3V for an upcoming project that will require some edge durability in impacts and it got to the point where it was difficult to see differences in performance at the 20 DPS edge angle I had standardized for certain cut tests, so I went back yesterday and adjusted all the samples and standards back to 18 DPS to make any differences more obvious. I thought it might be cool so I shot some video for you guys.

The take away here is the "industry standard" prescribed protocols for this, and other, steels can leave a lot on the table. It is very striking to see two blades of the same material and practically the same hardness behave so dramatically different.

[video=youtube;6imZ4Vo8iwA]https://www.youtube.com/watch?v=6imZ4Vo8iwA[/video]

https://www.youtube.com/watch?v=6imZ4Vo8iwA
 
Did you do a prequench on the HT? Or is it more of a change from a higher tempering temp to a lower one?

Hoss
 
Wow ,I just made my first 3v blades and was getting ready yo have them tested in the field.For years my go to steel for abuse was a2 .I've got one that has been thru 15 deer and still hasn't needed to be resharpened.To see how well it would take the abuse I took a hammer and drove it thru the rib cage and pelvic bones .So far I've had no chipping or deforming on the edge.
 
Good stuff Nathan. I've just started doing the cryo and low temp. tempering HT protocol for 3V and so far the results have been great.
Scott
 
We have been using the sub zero quench and 400° temper for about two years and its been great. I haven't done this type of test but I have chopped plenty of antler, shaved brass and steel with no damage at all..Battoned cross grain through a 1 1/2" chunk of oak and it would still slice paper just fine..It holds an incredible edge. If Im not mistaken Butch told me about that low temper and him using his 3v knife to cut the cans of canister Damascus with no edge damage..
Just another example of how the "industry standard" is not always best for our applications..Just like D2..Good tests Nathan :thumbup:
 
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Nate, is Peters using a version of your secret recipe now?
 
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