CPM 3V: High temper(1000°) vs low temper(400°) and sub zero quench

Kentucky

Kentucky

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Dec 13, 2008
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Just curious, do you guys think or have you noticed a difference between cpm 3v blades that are done with the 1000° temper and no sub zero quench and the ones done with a 400° tempers after sub zero quench????
 
I kind of understand the question about high/low tempering ranges, but why would you want to skip the sub-zero quench? It's my understanding that it's pretty much necessary to deal with retained austenite.
 
You don't need the 1000 F temper unless you work in a really hot place !!! I have mine tempered at 400 F.
Do you mean sub-zero , -100 F
Do you mean cryogenic , -300 F , liquid nitrogen
Please use proper definitions.
 
With 3V being right at the eutectoid, and having about 10% total alloy content, I don't know that sub-zero or cryo will greatly add to it. It won't hurt, though.

If doing a 1000F temper ( which would not normally be used on a knife) the effects of cryo would be reversed, anyway.

Sub zero quench is to finish the conversion from austenite to martensite. With 3V, IIRC, the end of the transformation is around 100F, so even sub-zero is probably of no use. If I had it available, I would use it, but I wouldn't spend any money on getting dry ice for 3V.

mete probably has the charts handy to check the TTT curve for 3V.
 
mete said:
You don't need the 1000 F temper unless you work in a really hot place !!! I have mine tempered at 400 F.
Do you mean sub-zero , -100 F
Do you mean cryogenic , -300 F , liquid nitrogen
Please use proper definitions.
Click to expand...

I was using proper(I didn't mention the dry ice), I use dry ice and acetone..gets down to about -104° on my thermocouple. I was wondering because Ive read and heard a lot of conflicting info on the subject but Ive been leaning towards 400° tempers with sub zero quench.
 
i do the cryo and 400f but if i didnt have cryo i woudl run as per the data sheet at 1000f. its all about RA reduction
 
3V looks a lot like a HSS to me on paper. And, like a HSS, even though it can be air quenched the manufacturer recommends a salt or interrupted oil quench in order for it to achieve the best properties.

Given that current metallurgical texts today show HSS having over 20% stabilized RA in the finished, tempered condition (the actual cutting tool) it stands to reason that 3V might also benefit from techniques used to minimize stabilized RA when used in a cutting tool. These techniques include rapid quench and cryo before temper. I wonder if anyone has done any solid comparative testing of this specifically on 3V?
 
I normally cool my plates before use..I use 1" aluminum. Ive read about the need for a fast quench on 3v so I was going to lay my plates in the freezer to be honest and try that. Ive talked to a couple guys that did that with great results. Im leaning towards the sub zero quench and 400° temper..Im just waiting on one more blank so we can get a couple knives out of the dry ice bath instead of one.
 
Kentucky said:
I normally cool my plates before use..I use 1" aluminum. Ive read about the need for a fast quench on 3v so I was going to lay my plates in the freezer to be honest and try that. Ive talked to a couple guys that did that with great results. Im leaning towards the sub zero quench and 400° temper..Im just waiting on one more blank so we can get a couple knives out of the dry ice bath instead of one.
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Cool, I can't wait to hear the results. Thanks for anything you decide to share.
 
I don't remember TTT for 3V. This past summer someone ,Microsoft or Yahoo mail, wiped out all my pictures and many documents !!! The 1000 F temper is for stability in dies .Yes it has other uses besides knives .Some corrosion resistance is lost. The 400 F is all you need for knives.This coupled with cryo gives further reduction in retained austenite and the formation of eta carbides on tempering . My 3V blades are treated with cryo and 400 F tempers [ two] .
Nathan , I wonder if jerry hossom has done that experiment.
 
Nathan the Machinist said:
I wonder if anyone has done any solid comparative testing of this specifically on 3V?
Click to expand...

I don't know. Next time I talk to Brad Stallsmith at Peters', I'll ask him about all this and see what he thinks. AFAIK he cryo's pretty much everything, having found that it doesn't hurt and most often helps quite a bit.
 
I just picked up some dry ice at the grocery store..Im letting the heater warm up before I wade through the snow to get at it..Im setting it on 1500° equalize for 5 minutes and then aust. @ 1950° for 30 minutes..Plate quench then into the sub zero..Then three two hour tempers @ 400°..
 
Not done the experiment. Always have had mine cryo'd and tempered at 950F. Rc61. Very much like what I have and never ventured further. Is there an advantage to 400F? Would certainly make finishing easier, but I'd be seriously hesitant to mess with what I have had working with 3V for the past dozen years.
.
 
i think the biggest thing is not having to run the kiln that hot and the risk of over shooting the tempering temp. the drop off in a spike over 1050f is drastic running 950 will keep plenty safe.

one thing that the high temper give you tho is option of some cool coatings that will alll fall under 1000f

Jerry like you i found a HT that is working well and while i have done the no cryo and high temper i have not tested the high temper with cryo. in my talks with a few far more knolagable then me on steel the high temper is for size change in die work and as long as one way or the other we get rid of the RA we are good to go.
 
I guess I'm a little perplexed by this discussion. Crucible Steel has never recommended a low temper for CPM-3V, and while they are today just a shadow of their former technical expertise they were once very knowledgeable, and having invented 3V and holding the patent on same I would expect they know what should be used. I do know this, they never intended 3V to be used for knives and when I first tried to buy it the service center told me they didn't want to sell it for that purpose. I had to call a VP in NY to get approval. In some respects it was a brilliant invention without an application - it was good at everything and best at nothing, and at the time Crucible didn't know the knife business existed. I don't believe it was used in dies originally, but later evolved into that roll in applications where D2 was experiencing microchipping. In fact that was the subject of a long dialog I had with the then chief metallurgist at Crucible, after I had told him I felt microchipping was the source of most dulling in hard use knives and a significant contributor in most. We had had that discussion for awhile when he told me they had done a study of D2 die failures and discovered that microchipping was indeed a problem in many cases. It was then I believe, probably around 2002/03 that 3V began getting more attention for that application. My brother was running a very large stamping company in Ohio at the time and they had never used it. nor any of the CPM steels for that matter. I've been told that 3V has less RA than other high alloy steels because of its eutectic nature, but cryo is a little like chicken soup - can't hurt. I will say this, using the HT I get from Paul Bos I have seen my 3V blades used and abused in ways I couldn't possibly have imagined. Except for a case where one was used to chop most of the way through a thick walled steel gas pipe, the only failure I have seen is minor plastic deformation (edge flattening or rolling) from encounters with very hard objects. The gas pipe guy did manage to create a small chip on the edge, but I suspect that was from fatigue since he was doing more cold forging than cutting by the time it happened. He was able to sharpen it out without much difficulty. It's major failing in my opinion is its lack of corrosion resistance, and even that can likely be attributed, at least in part, to oxide contamination at the mill. It's ugly. I either passivate or DLC coat all my 3V blades.

Now you know everything I know on the subject. I need to go grind some stuff. :)
 
I asked Scott Devanna about this subject a week or two ago and he said that he had very little info. on the subject. He said that it may be good for knives and was pretty sure that corrosion resistance would be at least a little better and possibly significantly better.
I'll be trying 3V for the first time in the near future and unless he offers a good reason not to I think I will try the method Kentucky described in post #13.
 
Jerry Hossom said:
I do know this, they never intended 3V to be used for knives...
Click to expand...

I've read and re-read your comments on 3V many times (thank you very much for sharing your findings, BTW!), and I find that particular fact amusing... simply because I've found 3V to be a truly well-balanced steel for knives thick or thin. I guess we just got lucky.

darrin sanders said:
I'll be trying 3V for the first time in the near future and unless he offers a good reason not to I think I will try the method Kentucky described in post #13.
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The "curious cat" part of me kinda wants to try it as well.

The "I know how well 3V performs with a 'standard' LN cryo and tempering, because I've personally beaten the daylights out of blades HT'ed that way" part of me says.... y'all go ahead and try that, let me know what happens. ;)

Obviously, none of us will be able to tell for sure unless we make two identical blades, HT them differently, and test/use them equally.

I frankly don't give a hoot in heck about increasing 3V's corrosion-resistance. Reports of it rusting are vastly over-blown in my experience, and the experiences of my clients... even with coarse finishes and without passivation (I am a huge fan of fine finishes and passivation on 3V, for obvious reasons... but they're not strictly necessary).

I find it odd that people rave about D2 as being "almost stainless", and complain about 3V being "rust-prone", when in fact their corrosion-resistance properties are very nearly the same... :confused:

Anyhow, my only interest in different HT protocols for 3V than Peters' and Bos use, is if they can increase edge-stability and overall toughness without sacrificing wear-resistance... which I doubt.
 
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