Best HT practices for CPM-S35VN?

Bob Ohlemann

Bob Ohlemann

Joined
Dec 5, 2013
Messages
1,180
Okay, I have 18 feet of CPM-S35VN on the way and I need to develop my HT process for it. I've searched the forum and read most of the pertinent threads and I've downloaded the .pdf from Crucible. So, is anybody plate quenching this steel? Can I cryo it in liquid nitrogen since that is easier for me than dry ice? I see that it can loose some of its' corrosion resistance when tempering above 1000°. Beyond that, what are the advantages/disadvantages of higher or lower temp draws? Anything else I should be asking or need to know?

Bob
 
I've used a bit of this stuff. Actually, I just finished an EDC made of S35VN yesterday. You can plate quench it and use LN. The following is how I treat it and the results I get on MY equipment.

1. Double wrap in high temp. foil.
2. Equalize furnace at 1600.
3. Add blade/blades, equalize again, & soak for 5 minutes.
4. Ramp to 1950 and soak for 30 minutes.
5. Plate quench until I can handle with gloves.
6. Remove from foil and correct warpage if necessary.
7. Dry ice & alcohol bath for 15-20 minutes. LN will probably do a better job.
8. Double temper at 400 for 2 hours each cycle.

This yields HRC-61 on my equipment. I'll add that this steel gives the most consistent hardness readings of any steel I've ever used. On every blade I've ever checked the variance is only about the width of the needle on the dial. Most steels will vary between 1/2 & 1 point but this stuff gives almost the exact same reading every time.
If you try it, let me know how it works out for you. Good luck.
 
bladsmth said:
IMHO, the best HT practice for CPM-S35VN is sending it to Brad at Peter's.
Click to expand...

I make one knife at a time, maybe two. This is not practical for me especially since I've invested in everything I need to do my own heat treating. Darrin, that sounds like what I'm looking for. Thanks! I will update this thread when I start getting results. Still open to any other input though.

Bob
 
I use the exact same sequence as Darren. I get Rc60 on the nose every time, but I only use subzero. I am not set up for liquid nitrogen. I temper at 400f, 2h x2. I find S35VN difficult to straighten in temper. Get it straight right off of the plates. Save yourself a headache. Finish sand before HT too. This is my least favorite steel to hand sand after heat treat. (I haven't tried cruforge V yet though.)
 
I was mostly kidding. My HT when I do it myself is pretty much the same as the other chaps.
 
My recipe is pretty similar...

1. Equalize at 1500
2. ramp to 2000 for 15 minutes
3. plate quench
4. temper 2 hours at 400
5. cryo in liquid nitrogen for 2 hours
6. temper 2 hours at 400

Crucible claims this will achieve RC61. I can tell you that it's difficult to finish and sharpen, but holds an edge very well. I've got a few in circulation and all are very happy with them. I think next time I will depart from Crucible recipe and LN cryo before the first temper. I do that with my other high alloy stainless steels. Might give me another point of hardness and provide more complete conversion, as Darrin is getting 61 with a lower austentizing temperature. Without a tester, I'll probably just have to count the number of curse words I utter when finishing and sharpening to guage how hard it is, lol. It's really not that bad to work with...nothing like S90V. I've only used it for thin kitchen knives. Have plans for some thicker knives next since I can't hardly seem to find any Elmax and it's getting so expensive.
 
Darrin, others - Would S30V use the same HT into as S35V?

Thanks for any info.

Ken H>
 
Its my understanding that you only need to reach subzero/cryo temp, no need for long soaks as the changes are almost immediate, unless you are after ETA carbides. Am I wrong?


Pablo
 
PEU said:
Its my understanding that you only need to reach subzero/cryo temp, no need for long soaks as the changes are almost immediate, unless you are after ETA carbides. Am I wrong?


Pablo
Click to expand...

Depends on the steel. The mf temp is -135f on many steels we use, meNing subzero doesn't quite get there.

Conversion is quick, unless you are going for eta carbides, which require 6h+ at cryo temp.
 
Willie71 said:
Depends on the steel. The mf temp is -135f on many steels we use, meNing subzero doesn't quite get there.

Conversion is quick, unless you are going for eta carbides, which require 6h+ at cryo temp.
Click to expand...

Where do you get TTT datasheets for, lets say, cpms35vn or how do you know exactly its Mf temp?


Pablo
 
I generally consider the Mf for stainless and high alloy steels at -100F. For our purposes, dry ice sufficiently reaches Mf on stainless steel knife blades.

The transformation from austenite to martensite is instantaneous, so there is no need for a prolonged soak at -100F. Once the blade reaches the Mf temp, it is done converting.
If using LN, a soak of 6-10 hours is required to allow the eta carbides to form.

PEU - I remember you were looking for those TTT charts a good while back. I would contact Crucible/Niagara tech support directly and see what they have.
 
NOT a dumb question at all. Eta carbides are super super small carbides that precipitate upon tempering. LN2 temps are required for the formation of eta carbides, sub zero temps using dry ice slurry -100F is not cold enough. Recommend this for a quick study...."Comparison of Effects of Cryogenic Treatment on Different Types of Steels: A Review". That paper is very interesting. It goes into soaking times of LN2 cryo, and the varying hardness levels at various holding times.
 
Darrin Sanders said:
I've used a bit of this stuff. Actually, I just finished an EDC made of S35VN yesterday. You can plate quench it and use LN. The following is how I treat it and the results I get on MY equipment.

1. Double wrap in high temp. foil.
2. Equalize furnace at 1600.
3. Add blade/blades, equalize again, & soak for 5 minutes.
4. Ramp to 1950 and soak for 30 minutes.
5. Plate quench until I can handle with gloves.
6. Remove from foil and correct warpage if necessary.
7. Dry ice & alcohol bath for 15-20 minutes. LN will probably do a better job.
8. Double temper at 400 for 2 hours each cycle.

This yields HRC-61 on my equipment. I'll add that this steel gives the most consistent hardness readings of any steel I've ever used. On every blade I've ever checked the variance is only about the width of the needle on the dial. Most steels will vary between 1/2 & 1 point but this stuff gives almost the exact same reading every time.
If you try it, let me know how it works out for you. Good luck.
Click to expand...
I know this is an old thread, but do you blow compressed air on it while plate quenching?
 
Outdoor Gear Dad said:
I know this is an old thread, but do you blow compressed air on it while plate quenching?
Click to expand...


I don’t. Plate quench is fast enough. If you are doing large batches, then keeping the plates cool is important. Otherwise, don’t worry about it.
 
How soon is it recommended to put the blades into the cryo treatment? whether it be dry ice or LN

We talking right after the quench, or if doing a batch of 3-4 blades, is some time before they go into cryo ok? trying to find the most optimal way to perform the cryo with multiple blades seeing how I want them to soak for at least that 6-10 hour mark.

Also, has anyone seen this article?

https://knifesteelnerds.com/2020/01/13/s35vn-steel-properties-and-how-to-heat-treat/

Thanks!
 
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