Delta heat treat, cpm3v pre quench question.

[rodriguezryan14]

I’m not asking for exacts on Nathan’s heat treat. But has anyone been using a pre quench? Currently I’m using 1950 aus, 40 minute soak, plate quench in frozen plates, straight into the freezer for 30 minutes, over night cryo, and triple temper at 400. 61rc. Is there any way to improve on this? Any trade secrets anyone is willing I share? I’m planning on trying a pre quench on this and ztuff to see if I can gain any toughness! Anyone have a suggestion as to when I should perform my pre quench? What temps? I’ve read 1700, soak 10 minutes, pre quench then ramp to full aus temp! Any help would be appreciated!!

 

[JoeBusic]

How much toughness do you want more? I don't use 3V so no advice on that from me. Prime advice in general would be "Do it your way, yourself!". Ergo, make a bunch of testers and go for it.
But there are some simple steel logics to abide before. I would lose the freezer before cryo. Austenite stabilizes at hold. 30 min in the freezer will hold temp majority of that time. Freezing plates gives to little to care. Prequenches are used to prepare the steel for a different than standard quench. So, what is the difference than standard you want to take? Start there and how to prequench will reveal itself.

 

[hugofeynman]

Roman Landes Heat Treatment recomendation

:Now this is what I would recommend for heat treat cpm 3v:



1st preheat: 500-600°C, equalize

2nd preheat:800-900°C, equalize

Autenize: 1060-1070°C, equalize, soak 30-35min

Quench in Oil preheated 60-80°C

Cryo: immediately after cleaning, minimum -80°C or lower soak 30min

1st Temper: 150°C equalize, soak 2hrs, quench in water

Cryo: immediately after temper

2nd Temper: 180-200°C equalize, soak 2hrs

should give you 60+ and a fine durable grain.



RGDS Roman

This is why i would do it like this.



the "receipt" suitable is for a vacuum furnace (Quench with maximum pressure) or a regular cline, but surface protection has to be assured.



Salt bath will cut the soak time appx. by 1/3 and thus give better aus-grain.



The preheating steps will assure the the austenization steps can be done quick. Quicker speed >> smaller grain



Austenization temperature is dedicated to dissolve Chrome and Molybdenum >> fair hardness and some enhanced "Stainresistance" is to be expected.

The vanadium will remain in the steel bond as carbide, hence aus-grain cant really grow



The oil quench is suitable for any steel out of the air hardening classes. The thin cross sections get higher hardness after quench (greater volume fraction of martensite) and a less stabilized volume fraction retained austenite. (The volume fraction of RA can be expected (near guess) between 20 and 30% or even higher)



Warping of the blade shall not be an issue with these materials.

If you have done allot of hard mechanical work before hardening (milling, grinding,)than do a stress relief so warping gets less likely.



The cryo needs to be done as quick as possible below -80°C.

RA tends to stabilize rather quick after the quench (some reports speak of minutes)

The longer you wait, the less efficient the transformation to untempered martensite will be.

And a minimum of -70°C is necessary to get enough stress into the micro structure, so the transformation (RA>>Martensite) process can restart again.

Extensive soak time is not necessary since the process runs at hyper sonic speed.

But still there will be remains of RA that need to be addressed by the 2nd cryo.



The first temper is a low temper so the remaining RA is stabilized at the lowest level possible and at the same time there is enough stress relief in the martensite that has been build and furthermore the transformation from tetragonal to cubic matensite is started.

The water quench speeds the whole thing up and avoids precipitation of embrittleling phases.



Than the rest of the remaining RA will be attacked by the 2nd cryo (usually the RA will drop below 5% volume fraction) so burr formation is less likely.



2nd temper will now temper the untempered martensite build up by the cryo and bring the blade to a fully tempered matensitic structure with a low volume fraction of RA and a fair amount of carbides undissolved.



Of course there is the question why not temper it at 540°C?



1st of all, if you don't have access to cryo than this is your way to go.

In my studies of edge stability a did extensive work to compare secondary hardening and low temper with cryo.

The results (reference is my graduate thesis 1999 Munich University of Applied Sciences) i found considerable higher edge stability with the samples that had low temper/cryo The material used at the time was ATS-34 all with the same charge and thus the same condition of austinization, but with different temper cycles.



RGDS Roman

 

[hugofeynman]

It’s you, Ryan! Only now I’ve noticed. That receipt I’ve published is from PHD Roman Landes regarding cpm3v heat treatment. It was public on the unfortunately long gone hypefreeblades forum. Hope it helps!

 

[shqxk]

The recipe you using is already very balance so nothing to be improved. You better think about the overall design of the knife, ergonomic, blade geometry or even the sharpening quality.

I used to chase the be all end all HT protocol but now realize that there are others more important aspects to be thought of to make a better knife.

 

[rodriguezryan14]

How much toughness do you want more? I don't use 3V so no advice on that from me. Prime advice in general would be "Do it your way, yourself!". Ergo, make a bunch of testers and go for it.
But there are some simple steel logics to abide before. I would lose the freezer before cryo. Austenite stabilizes at hold. 30 min in the freezer will hold temp majority of that time. Freezing plates gives to little to care. Prequenches are used to prepare the steel for a different than standard quench. So, what is the difference than standard you want to take? Start there and how to prequench will reveal itself.

My whole reasoning for freezing the plates is to get the fastest quench possible, colder plates will remove heat quicker of course. Going into the freezer after quench in my mind will reduce shock and get temps down better before the main cryo shock. It makes sense to me, but of course I don’t know for sure, that’s why I mentioned it. I mean, a slightly warm blade being dunked into ln2 would put a massive shock on the steel I would think. And we are always chasing the best of the best, at least I am. I read all the time about delta heat treat, longer aus holds, pre quench, quicker quench etc. so that’s why I’m asking these. In theory of course, a pre quench should help with grain refinement. When I have more time on hand, I am planning on trying a few tweaks and sending Larrin some charpy samples, 3v and ztuff. Those are my favorite and most used steels. Possibly some experimenting with A8 mod.

 

[rodriguezryan14]

It’s you, Ryan! Only now I’ve noticed. That receipt I’ve published is from PHD Roman Landes regarding cpm3v heat treatment. It was public on the unfortunately long gone hypefreeblades forum. Hope it helps!

Yup, it’s me, I’m kinda back. Not to much free time these days, but I am making a few blades again. I’ve seen that heat treat, and would like to try it and compare it to what I’ve been doing so far. By no means is my heat treat bad in any way I’ve noticed. But there’s probably always room for improvement!

 

[rodriguezryan14]

The recipe you using is already very balance so nothing to be improved. You better think about the overall design of the knife, ergonomic, blade geometry or even the sharpening quality.

I used to chase the be all end all HT protocol but now realize that there are others more important aspects to be thought of to make a better knife.

Ive been working on all those things. And I have it down to where I like. But I always feel I can improve on heat treat, considering in my opinion that’s the most important aspect of a good blade. What are you’re thoughts on the freezer pre cryo? Any benefit?

 

[JoeBusic]

My whole reasoning for freezing the plates is to get the fastest quench possible, colder plates will remove heat quicker of course. Going into the freezer after quench in my mind will reduce shock and get temps down better before the main cryo shock. It makes sense to me, but of course I don’t know for sure, that’s why I mentioned it. I mean, a slightly warm blade being dunked into ln2 would put a massive shock on the steel I would think. And we are always chasing the best of the best, at least I am. I read all the time about delta heat treat, longer aus holds, pre quench, quicker quench etc. so that’s why I’m asking these. In theory of course, a pre quench should help with grain refinement. When I have more time on hand, I am planning on trying a few tweaks and sending Larrin some charpy samples, 3v and ztuff. Those are my favorite and most used steels. Possibly some experimenting with A8 mod.

Freezed plates will give you 3-4% faster quench.
Freezing before cryo is good but not 30min as it will stabilize way before that. I would go max 10min or even cca 5min. I have an Al plate in my freezer to get things going faster.
Prequench for grain refinement is good as long as you modify the aus temp and soak times (lower and shorter). Using same temp and soak will eliminate prequench benefits. This one is tricky and is to be tested with your equipment to find the best scenario.
Nice planning.

 

[rodriguezryan14]

Freezed plates will give you 3-4% faster quench.
Freezing before cryo is good but not 30min as it will stabilize way before that. I would go max 10min or even cca 5min. I have an Al plate in my freezer to get things going faster.
Prequench for grain refinement is good as long as you modify the aus temp and soak times (lower and shorter). Using same temp and soak will eliminate prequench benefits. This one is tricky and is to be tested with your equipment to find the best scenario.
Nice planning.

What I was planning on doing, larrins suggestion, is soak at 1700 for 10-15 minutes, pre quench, ramp to 1950, put blade back in, soak 30 minutes final quench. Then my typical routine!

 

[rodriguezryan14]

Freezed plates will give you 3-4% faster quench.
Freezing before cryo is good but not 30min as it will stabilize way before that. I would go max 10min or even cca 5min. I have an Al plate in my freezer to get things going faster.
Prequench for grain refinement is good as long as you modify the aus temp and soak times (lower and shorter). Using same temp and soak will eliminate prequench benefits. This one is tricky and is to be tested with your equipment to find the best scenario.
Nice planning.

By the way, thanks for you’re help