s35v compared to s30v for a hunter

bladsmth said:
The conversion to martensite from austenite happens instantaneously as soon as the steel is fully at -100F. A half hour is more than long enough to assure the steel has dropped to the temp of the bath. The bath will last quite a while in nothing but a steel pan with no insulation. Set the pan on a piece of plywood.
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To my untrained mind, it seems like a minute or two would do it- is a half hour neccessary?
 
David, Roman Landes says that the water quench after the first temper also helps to get you around some of the potential embrittlement issues that some high alloy steels might develop during the process. IIRC, he goes with a first post cryo temper that is about 30C lower than the "regular" one and then does the water quench after that and maybe another short dip in the LN.
David Wesner said:
Hey Trooper :) I've worked with both S30V & S35VN. S35VN is my preferred choice considering the 2 you mentioned, both in performance & upkeep for the user in the field.

Like every blade steel we use, correct grind/edge geometry, combined with proper thermal cycles & heat treat technique is imperative in bringing out the full potential of this material. And for that matter, every other piece of blade stock we use.

Like S30V don't skip the cryo. Although there may be a lot of misinformation on the web regarding cryo, one aspect that's not in dispute is it's ability to transform retained austenite (in steels that are prone to develop it) to untempered martensite.

Per Verhoeven, when using high alloy air harden steels, to help reduce retained austenite :
- avoid the higher Data Sheet listed austenitizing temperatures.
For S35VN HT in my shop …. I use the mean temperature of 1950*F.
- Avoid excessive soak times (for 3/16" stock I soak 20 min at temp)
- Use interrupted oil quench vs. plate or positive pressure air quench (I oil quench the blade to just <1000*F then positive pressure air quench using a cold air gun to ~ 100-150*F)
- Following the quench, move directly to cryo. Don't allow the blade to rest at room temperature for even 5 minutes.
Don't snap temper or "1st cycle" temper prior to cryo. Pre-cryo tempering or "setting the blade down for the night after quench" will most likely result in some stabilizing of the retained austenite. Personally, I always keep the HT cycle moving forward. Again, per Verhoeven, austenite that has been allowed to stabilize can make conversion to martensite very difficult.

If moving from quench directly to cryo concerns you, to decrease the potential risk of fracturing or micro-cracks resulting from going directly to cryo from quench, you can reduce the temp more slowly by placing the blade above the LN prior to full immersion. FWIW, in my first experiments using D2, I did it both ways. After examining samples using fluorescent dye penetration inspection and later, SEM inspection, and finding not a single micro-crack or fracture (as in none) I now go directly to a slow full immersion in the LN following the quench.

As is standard practice, all cold treatments (LN, Dry Ice + Acetone, etc.) should always be followed by tempering. In the case of CPM S35VN I use (3) 2 hr. cycles at 475*F. I quench in water between each cycle (right out of the tempering oven) so that I can go immediately back in for the next cycle.
The end result of the above mentioned procedure for S35VN, in my shop, results in a final HRC of ~60, + or - a point

I always try to give credit to those who paved the way before me, and in the case of Heat Treat, that would be Kevin Cashen. Speaking of custom knife making, Kevin has been a Tour de Force in regards to teaching proper heat treat technique and listing of resources on the subject.
The best he&#8217;s passed on have been:
"Steel Metallurgy for the Non-Metallurgist" by John D. Verhoeven , call # TN705 .V45 2007
&#8220;Fundamentals of Physical Metallurgy&#8221; by John D. Verhoeven, call # TN690 . V46 1975
&#8220;Tool Steel Simplified&#8221; by Frank Palmer, George V. Luerssen, Joseph S. Pendleton Jr. 1978 (sorry, no # for this one)

My final thanks in regards to my extremely anal Heat Treat Procedures go to Nathan Carothers (at BF we know him as &#8220;Nathan the Machinist&#8221;). His ongoing experiments with D2 steel (among others) and his findings related to edge retention and stability following cryo was impossible to ignore, (for me anyway), and the final nudge I needed to pursue further knowledge regarding the subject. Thanks Buddy :thumbup:

There&#8217;s my experience with S35VN Trooper. Sorry for the long winded response &#8211; I hope it helps you :thumbup:


;)
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Perhaps to make sure that the temperature has stabilized throughout the piece. Supposedly, the actual conversion to martensite happens VERY quickly.
elementfe said:
To my untrained mind, it seems like a minute or two would do it- is a half hour neccessary?
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trooperstealth said:
Hey there,
that is no long winded explanation there is a lot of awesome information in all that. Very much appreciated. The expensive thing here is australia is setting up cryo. I am looking at setting up in my shop instead of sending away for cryo. I have traditionally plate quenched and used my plates out of the freezer.
I have just ordered over 1000 dollars worth of steel from Admiral. I would of ordered more but the freight to Australia is almost half the order ! You cant get steel in Australia you have to import it. To get a sheet of Elmax was 5000 ! So all this HT and user input is valuable in more than one way.
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DANG!!!!!! A "standard" 24 x 36 inch 50 lb sheet of .204 thick Elmax is about $950-1000 USD plus shipping from B-U USA last time that I checked!!! Even chopped up by a dealer into smaller bite sized pieces, it would still be less than $1500 for that amount i would think.
 
My EDC for the last 7 years is a Strider SMF with S30V steel that has been DOUBLE cryo treated by BOS. It's used every day for all kinds of odd stuff and you can hardly tell it's been used at all. I also have a Hinderer with a S35V steel blade. No cryo but it too is holding up well. Cutting? I prefer the S30V. It just seems to have a 'micro serrated' edge to it that 'bites' into things better. My 2 cents on the subject.
 
Whenever the blade reaches -100F the conversion is finished. How long it takes to fully cool the blade to -100F is probably only a few minutes, but 10 to 30 minutes will surely allow enough time. The point is that more won't do anything.
 
I am going to have to get some dry ice next time I do a HT of CPM S35VN. Any reason not to do the plate quench though?
 
I austenitize and soak for 30 min. Then plate quench in thick aluminum plates. (some folks do an interrupted oil quench and then stick in the plates). After it reaches room temp, I immediately do dry ice/acetone for 15 minutes or so, then temper twice. I used to do a snap temper at 300F, but have been told it isn't necessary.
 
I have only ever used the aluminium plates. It seems i am not getting all that i can from my steel by not utilizing the dry ice or cryo process??????
 
What will one gain from doing sub-zero quench or cryo?????.......... about 1-1.5 Rockwell points and a bit of toughness.

Will you be able to tell?????......maybe, maybe not. On a chopper, maybe not, on a filet, yes.
 
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