Recommend a heat treat for 4v

#1
Does anyone have a heat treat similar to what Carothers is using? I’m looking more for toughness, I’m building a “survival knife” out of this steel, and looking for a good tough heat treat, with minimal chipping. From what I’ve read on Nathan’s forum, the industry standard heat treat leaves a chippy edge! That’s why he developed his proprietary heat treat. Thanks
 

samuraistuart

Well-Known Member
#2
You can try what he (Nathan) does with 3v. I don't know if he does any pre-quenching, cycling, or other pre-hardening operations, but basically you go straight from quench to cryo (no snap temper), and use the low temperature tempers (avoid the secondary hardening tempers). The secondary hardening tempers rob carbon from the martensite to form carbides. While this aids wear resistance, it's not ideal for a chopping knife, where a higher apex stability is more important than wear resistance. The clincher is this, tho....with a fairly highly alloyed steel like 4v, the LN2 alone may not convert the RA% one might seek. That is why secondary hardening is almost a must for RA reduction on such highly alloyed steels, the LN2 doesn't convert enough of it (surprising to me). Sometimes 2 LN2 cycles are used, as in one post quench, and another after the first temper. That gives you an idea of the basics of the delta HT, but that was tuned for 3v, not 4v (or even M4). I had Peters' do the Delta heat treatment on a CPM M4 hunter for me a few years ago, and it seems to work great. But that's a hunter, not a chopper.
 

Andre Grobler

Well-Known Member
#3
The delta ht should work for added toughness, just use the lowest austenitizing temp with a good oil quench, then liquid nitrogen, then a 300F temper some more Liquid nitrogen then some more 350f temper - I use this for a related but not the same steel... k490... and it comes out at rc63 and very tough. I have to say though... experiment with your furnace on some samples beforehand... in my oven the lowest aus temp and this recipe gave the highest hardness... which implies RA was at the lowest and quite manageable... make no mistake though it will still be a bear to grind... also keep in mind that people leverage the high temper to make more carbides which MIGHT give a stiffer edge... i can not comment on this, but if it works it means that the edge will not wobble in a competition, but it will fail more dramatically, also be aware that dialing that secondary hardening curve in might be harder than expected... and i suspect you do not want to use cryo if you go secondary hardening curve... my heat treat experiment with k490 is on @GroblerCutlery some time last year... but use temps for m4 not what i used
 
#4
Thanks for the replies, I just got my rc tester, so now, I’ll make up some coupons and try a few different things. I’ll test with oil, plates, prequenching, and maybe a few other things. The only problem is finding the time to do this.
 
#5
The delta ht should work for added toughness, just use the lowest austenitizing temp with a good oil quench, then liquid nitrogen, then a 300F temper some more Liquid nitrogen then some more 350f temper - I use this for a related but not the same steel... k490... and it comes out at rc63 and very tough. I have to say though... experiment with your furnace on some samples beforehand... in my oven the lowest aus temp and this recipe gave the highest hardness... which implies RA was at the lowest and quite manageable... make no mistake though it will still be a bear to grind... also keep in mind that people leverage the high temper to make more carbides which MIGHT give a stiffer edge... i can not comment on this, but if it works it means that the edge will not wobble in a competition, but it will fail more dramatically, also be aware that dialing that secondary hardening curve in might be harder than expected... and i suspect you do not want to use cryo if you go secondary hardening curve... my heat treat experiment with k490 is on @GroblerCutlery some time last year... but use temps for m4 not what i used
I am surprised on the oil quench. I can’t find much on this! I usually use frozen quench plates. What kind of quench oil are you using? I have parks 50 on hand.
 

Andre Grobler

Well-Known Member
#6
Just any old medium oil should be fine, iso 32 parks might be too fast but if you use the low temp it may be fine medium oil got the hardnes really good without having to resort to high temper to get max hardness
 

Andre Grobler

Well-Known Member
#7
P.s. high aus temp pieces of steel would tend to flame parks 50 which would degrade it quite fast, so just make sure you have a lot of it to quench deep...
 

scott.livesey

Dealer - Purveyor
#8
#10
I don't see the need to oil quench 4V. I've been using it since it first became available and have always plate quenched with excellent results. If you can get max. AQ hardnesses with plates, what do you gain by oil quenching?
 
#11
I’m gonna try this with a prequench, between plates, then a final plate quench at higher aust temp, followed by cryo, and low temp temper! See how that goes first. I’m guessing 1750 for 30 minute soak, plate quench, then back in, followed by another 20-30 minute soak at 1950. Cryo, then triple temper at 400. This is guessing. I might buy some more steel, and run some coupons, see what I get. What should I be looking at, as far as rc as quenched? Around 66-67?
 

Andre Grobler

Well-Known Member
#12
I don't see the need to oil quench 4V. I've been using it since it first became available and have always plate quenched with excellent results. If you can get max. AQ hardnesses with plates, what do you gain by oil quenching?
If you are at max hardness with a plate quench and a low temper like 350 or 400f then there is no point, unless you grind pre heat treat of course...

If
 
#13
I’m gonna try this with a prequench, between plates, then a final plate quench at higher aust temp, followed by cryo, and low temp temper! See how that goes first. I’m guessing 1750 for 30 minute soak, plate quench, then back in, followed by another 20-30 minute soak at 1950. Cryo, then triple temper at 400. This is guessing. I might buy some more steel, and run some coupons, see what I get. What should I be looking at, as far as rc as quenched? Around 66-67?
I've never tried a pre-quench on 4V so I would love to hear your thoughts after testing. With my equip. I get max. AQ hardness (65-65.5) with a 1965 hardening temp, plate quench, & overnight LN2 soak. I triple temper between 350 & 450 depending on the application. Your equip. may give different numbers so play with it until you find what works best.
I really like 4V. I've made several hunters for guides/PH's that advised me up front that they would see hard/rough use such as splitting Elk Sternum, pelvis, ribs, etc. and they have all held up perfectly. A few of them have even ordered other knives in either smaller or larger sizes but they all stress the importance of them being made in 4V. As long as they're happy, I'm happy. LOL
 
#14
I've never tried a pre-quench on 4V so I would love to hear your thoughts after testing. With my equip. I get max. AQ hardness (65-65.5) with a 1965 hardening temp, plate quench, & overnight LN2 soak. I triple temper between 350 & 450 depending on the application. Your equip. may give different numbers so play with it until you find what works best.
I really like 4V. I've made several hunters for guides/PH's that advised me up front that they would see hard/rough use such as splitting Elk Sternum, pelvis, ribs, etc. and they have all held up perfectly. A few of them have even ordered other knives in either smaller or larger sizes but they all stress the importance of them being made in 4V. As long as they're happy, I'm happy. LOL
What are you keeping your rc at for your hunting blades. I’m looking for around 61 rc I think! I just ordered a couple more bars of 4v and vanadis 4e, So after I profile these, I’ll be trying that heat treat! I’ve been told by people that work with this steel a lot, that this looks like a solid heat treat. So I’ll keep you posted after some testing. I’m wanting to build one knife, just for hard use testing! So I’ll update on this post when it’s done!
 
#15
I run 4V hunters at 62. Its almost as tough as 3V when both are at 62. I've never had a problem or a complaint. This stuff is tough and has excellent edge stability. Don't be afraid to run it hard and grind it thin. Make a couple of test blades and try it out. I betcha a coke that you like it.
 
#16
I run 4V hunters at 62. Its almost as tough as 3V when both are at 62. I've never had a problem or a complaint. This stuff is tough and has excellent edge stability. Don't be afraid to run it hard and grind it thin. Make a couple of test blades and try it out. I betcha a coke that you like it.
I was able to hit 66-67 rc after quench, followed by a 30 minute cryo. Final rc after my tempering process turned out 61 rc. Which is what I was looking for! I’ll let you know how they turn out after I test them.
 
#17
The delta ht should work for added toughness, just use the lowest austenitizing temp with a good oil quench, then liquid nitrogen, then a 300F temper some more Liquid nitrogen then some more 350f temper - I use this for a related but not the same steel... k490... and it comes out at rc63 and very tough. I have to say though... experiment with your furnace on some samples beforehand... in my oven the lowest aus temp and this recipe gave the highest hardness... which implies RA was at the lowest and quite manageable... make no mistake though it will still be a bear to grind... also keep in mind that people leverage the high temper to make more carbides which MIGHT give a stiffer edge... i can not comment on this, but if it works it means that the edge will not wobble in a competition, but it will fail more dramatically, also be aware that dialing that secondary hardening curve in might be harder than expected... and i suspect you do not want to use cryo if you go secondary hardening curve... my heat treat experiment with k490 is on @GroblerCutlery some time last year... but use temps for m4 not what i used
I tried the plate quench, with a 1950 aus temp. My blades turned out at 61 rc after temper, which is exactly what I was looking for. I’ll let you know how my testing turns out. I have one blade I made that I will be doing a standard cut test, and end up destroying it. We’ll see how it turns out.
 
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