3V Heat Treatment

i4Marc

i4Marc

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Oct 19, 2011
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I did a search but didn't find as much as I'd have liked. The manufacturer's data doesn't mention a sub zero.

Does 3V benefit from a sub zero? If so, is DI sufficient?

If any of you regularly work with CPM 3V do you mind sharing your routine? Otherwise, I'll just follow the manufacturer's instructions.

Also, any recommendations as far as finishing before or after HT? That is to say, will it be too wear resistant after HT to get regular hand sanding done?
 
My recipe is 1955F 30 min (skip the preheat) ---> salt or plate quench to hand warm ---> subzero in dry ice/acetone for an hour then double 400F tempering in salt 1 hour each (2 hours if using oven)= 61HRC.

You can try pre-quenching for properly better grain structure (?) at 1725 for 30 min then plate quench + 1000F tempering for some stress relieving.
 
Sub zero is beneficial, however, Cryo is much preferred. Just grab a 10L Dewar & find a welding supply near you that sells LN2. My local spot sold it cheap! Like $20-$30 I think. And do the Sub Zero or Cryo RIGHT AFTER hardening, and BEFORE tempering. Shoot for 60-61 HRC. Sorry, I can’t give you all the details. I have decided to keep having Brad at Peters take care of all my HT....rather than build an oven & get the LN2 for Cryo....then spend many, many, many hours figuring out the “magic” cycle exactly. Just not worth it to me, with my output. Nathan knows the “secret sauce” recipe as well. But I doubt he will divulge that info. Maybe.
 
I’m surprised you did not find anything on heat treating 3V. It’s been talked about ALOT on here.
 
Preheat at 1550, ramp to 1950-1975, plate quench, then sub zero or cryo. Temper at 400x2hx3.
 
My understanding is that if you want to use the HT recipe that Nate and others use with its low tempering temperatures, then the cold treatment is pretty essential.
 
The way I see it, if the hardening temp is above that 1550/1600f area, employ sub zero. Cryo even better. The more carbon, and the more alloying, the more sub zero or cryo is going to help eleminate retained austenite, which is generally an undesirable structure in a knife.

JDM61s comment is my understanding as well. A fine edge doesn’t do well with high secondary hardening tempers, which is the traditional way of removing RA, but robbing the martensite matrix of carbon by forming carbides. The sub zero or cryo process eliminates RA without robbing the martensite matrix of carbon.
 
A few years back, I was talking to the B-U guy at Blade and he confirmed that with steels like M390 and Elmax, dry ice wasn't quite cold enough to do the full conversion. We know that dry is just fine for very simple steels like AEB-L but I am not sure about steels with a bit less alloying than the crazy steels like say CTS-XHP or 3V.
 
jdm61 said:
My understanding is that if you want to use the HT recipe that Nate and others use with its low tempering temperatures, then the cold treatment is pretty essential.
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BINGO! You are correct my friend. And with that, once again.... it’s *crucial that the Cryo be performed immediately after quenching. Coupled with the low temper temps., we are getting a full 60-61hrc with no loss of impact toughness of origional heat treats at 58-59hrc.

The blades I get back from Brad are unreal! Tough as hell, takes and HOLDS an insane edge. And the steel will barely take more than a surface rust! There is a reason I chose this steel long ago for all my outdoor & combat blades. Hands down my favorite!
 
The cryo as a continuation of the quench has been written about by a number of guys. Roman Landes says that the technique is best for pretty much any of the higher alloy steels. IIRC, his dissertation research was done with RWL34. The other thing that he recommend was WATER quenching coming out of the temper to get the steel though the embrittlement zone quickly, but that may only apply to steel done at the high temper.
One Armed said:
BINGO! You are correct my friend. And with that, once again.... it’s *crucial that the Cryo be performed immediately after quenching. Coupled with the low temper temps., we are getting a full 60-61hrc with no loss of impact toughness of origional heat treats at 58-59hrc.

The blades I get back from Brad are unreal! Tough as hell, takes and HOLDS an insane edge. And the steel will barely take more than a surface rust! There is a reason I chose this steel long ago for all my outdoor & combat blades. Hands down my favorite!
Click to expand...
 
Just consulted my HT book and found the following:

1250f soak for 10min

Ramp to 1550f and soak for 10min

Ramp to 1950f and soak for 30min

Plate quench

12hr cryo in LN

Temper at 400f for three 2hr cycles.


That isn’t exactly what’s reflected in this thread. I think I got the info from Devin Thomas’ recipe, but he uses two ovens. So am I right in assuming that it’s best not to bother with the 1250f pre-heat unless I have two ovens? Being that it takes a while to ramp from 1250f to 1550f, amd again from 1550f to 1950, that’s a long time for the blade to be soaking.

So if you just have one oven, is the consensus to just do the 1550f pre-heat for 10mins and then ramp to 1950f for a 30min soak? I assume it would be best to leave the blade in the oven while it ramped to 1950f. Am I correct in my assumption?
 
Well I spent about 20mins writing up a whole explanation about all the research I did when I was looking for one, and what I settled on. I went and took a couple pics of my ln dewar, loaded them to imgur, and when I came back here all my damn text was gone. God dammit.

So I’ll give you an abbreviated version. No, that isn’t the type of dewar you want. It looks to have little, to no insulation. You want a dewar like this:

EaLd1fe.jpg


This is mine. It’s a 10L but will fit a 15” blade in it. The internal height is 21” from the bottom to the brim. BUT, there’s a 7” cork/cap:

M99wyBW.jpg


So I have around 14” if I want to keep the cap all the way on. With longer knives I leave it sticking up a bit. It’s no big deal, it’s only for 12hrs or so. See the grooves in the styrofoam cork? You can wrap wires through your tang holes and run them up through the cork/ lid, so they will hang vertically into the LN.

Oh and when you’re shopping for dewars, make sure you pay attention to the mouth diameter size. A lot of them are around 1.5”. Mine is only 1.97”
 
Like JG implied, what you want IF you can find it is a dewar with the bigger neck. Yes, in theory, your LN will evaporate more quickly, but you will never find yourself in a position where your beautiful kitchen knife won't fit into your dewar. ;)
 
i4Marc said:
Thanks JG. the mouth opening is a critical area because some of my blades are wider than 2". Most of the dewars I've seen have a mouth opening of 50mm. Does this one look like it has enough insulation? The mouth is nice and wide.


https://www.ebay.com/itm/50L-Liquid...990242?hash=item3d58dea0e2:g:U7MAAOSwmuVae3wt
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Marc I have the typical 10L 50mm $200 dewar because it fits the majority of the knives I cryo. On the few occasions I need to cryo something bigger, I just pour off a couple liters into a cooler. The first liter evaporates quickly as the cooler is brought down to temp, but once it's at temperature, it holds the last bit for over 6 hours. At $2/liter I can do this a lot before it made more sense to buy something like you linked. Especially when you consider that 50L has a 70 day hold time, and my 10L holds for 75-80 days. ($100 every 3 months vs $20) If the majority of your knives wouldn't fit a 10L 50mm then definitely go for something like that big one instead.

xK2mSxP.jpg
 
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