Heat treating CPM 3V to 63 rc

AcridSaint said:
I really don't understand the hangup on HRC. It's only one value and most useful to tell you if you're heat treating the steel correctly. There have been many many knives made for many many years that would RC in the low 50's and were still thought to be "good". CPM3V in the low 50's would probably be "better" than many of those old knives. What are you getting with the extra 1-3 points of hardness?

You're approaching file hardness at 63. Why would one strive to get "better than average steel" results with a steel that can perform exceptionally just to get a couple rockwell points?

Maybe you're onto something, but the only real way to find out would be to do several at different hardnesses and put together a standardized testing method to see if full hard 3V performs better than the others in your application. If not, then you'll never really know if you got a better knife, or just a harder one.
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The hardness allows the knife to hold thinner edges. Each point in hardness adds 20-30% better edge retention and allows 2° degrees more acute edge bevel which translates to a very significant difference in actual use. These are my own estimated numbers based on actual experience. 63 rc is not very hard, it's a compromise that actually favors toughness as far as small knives are concerned.

Again, the difference in just 1 point difference in hardness is very noticeable if you thin down the edge. If you're using greater than 30° degree bevel, you might not ever notice the difference.

I'm interested in hearing other peoples' experience in this though.
 
For the darksiders and other sharpening junkies, it is very noticeable. I forget who, maybe gator97, posted that he had a couple knives rockwell tested after having used them for a while. He noted that the harder knife was one that he could sharpen to a more acute angle and have the edge hold up, while a softer one needed a relatively more obtuse angle to get decent longevity. The hardness testing after the practical use possibly demonstrates that higher hardness improves the ability to take thinner edges, which in turn of course means more efficient cutting.

I believe Phil Wilson has also stated that he feels increasing hardness is one of the most important factors in increasing edge retention, as he has observed in his manila rope cutting tests on the steels he uses for knives.

It really depends on what the owner is doing with the knife. How often it is used to cuts things, and what kind of edge is being applied.
 
I will also be interested to see how this turns out. I'd like to know where the 20-30% comes from and if that's across the board for steels and materials cut. We're talking about a ~70-100%+ increase in cutting ability in three points on the top end of the steel.

I'd also like to see more about the sharpening angle and how constant that is from steel to steel. I'd be very interested in some measurements of this.

Always open minded, I can be won over with results.
 
hardheart said:
It really depends on what the owner is doing with the knife.
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and that right there is the key
i run 3v at 62rc no problem and i run cpm154 at 63 rc
i tend to run steel a little harder and let the buyer knife its a cuttign tool not a hammer or pry bar
not that said most of my work is kitchen knives adn razors with a few hunters in the mix
no big choppers
i would not ever run a chopper at the same heat treat i use for a necker or kitchen knife
 
Thanks Mete. I will check it out. We have just used the same ovens to heat treat some blades using CPM S30V and CPM M4. Both have hit the numbers we expected. So we are comfortable with the temperatures we are using on the ovens. The CPM 3V didn't harden like we expected at all. I'm not sure what is happening with it. I'm going to try another blade tomorrow. We would really like to be able to do our own heat treatment on 3V, but so far we can't get the hardness necessary at all.
 
Hmathews said:
Thanks Mete. I will check it out. We have just used the same ovens to heat treat some blades using CPM S30V and CPM M4. Both have hit the numbers we expected. So we are comfortable with the temperatures we are using on the ovens. The CPM 3V didn't harden like we expected at all. I'm not sure what is happening with it. I'm going to try another blade tomorrow. We would really like to be able to do our own heat treatment on 3V, but so far we can't get the hardness necessary at all.
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Are you planning to try the Bos/Hossom recipe for 3V? If so, tell us how it turns out.

AcridSaint said:
I will also be interested to see how this turns out. I'd like to know where the 20-30% comes from and if that's across the board for steels and materials cut. We're talking about a ~70-100%+ increase in cutting ability in three points on the top end of the steel.

I'd also like to see more about the sharpening angle and how constant that is from steel to steel. I'd be very interested in some measurements of this.

Always open minded, I can be won over with results.
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Sure, I'll do some testing when I make the knives. I would push-cut through drywall and see how many inches the blade cuts until it can no longer shave. Slicing is a different beast, that depends more on the carbides than the hardness.
 
Hardheart and Butch pretty much said it all. Not that there aren't benefits to an extra point in hardness but it will come at a cost. That cost could be negligible depending on the type of knife you are making and the intended use. If impact toughness is of little concern to your applications than I say max it out and let us know what you find upon testing.
 
Yep! Soak time we used was longer 30 minutes at 1950. We didn't check the hardness until after tempering three times at 1000 for two hours each time. Hardness came out at54. So we also tried it at 2000 and checked the hardness right after the quench and it was 60. Tomorrow we will hit his numbers and see how it turns out.
 
Hmathews said:
Yep! Soak time we used was longer 30 minutes at 1950. We didn't check the hardness until after tempering three times at 1000 for two hours each time. Hardness came out at54. So we also tried it at 2000 and checked the hardness right after the quench and it was 60. Tomorrow we will hit his numbers and see how it turns out.
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thing to keep in mind the drop off in hardness after 1025 is steep and one to look out for
that was one or the reasons that i started the testing of a LN cryo then 400 temper
 
The steel we tested was not hard as we thought it should be after quench. Only 60. We don't mind a cryo in LN and then a temper at 400 since we use the LN for our S30V. We just don't have the hardness with 3V that we need to start with.
 
We are using 2 inch thick aluminum plates 6 inches wide and 18 inches long. Other than using salt I don't know anything that will get it done faster and I don't have a salt pot......yet. We like this 3v too much and have too much of it to not be able to do our own heat treatment. We also don't like sending our blades to anybody else for anything except engraving and we are working on that.
 
Charlie is thinking about drilling holes in our quench plates and plumbing them so that he can pump LN through the plates while we are quenching the 3V.:D

This is what we did last time to harden the 3V and it worked well, but is a little cumbersome and probably dangerous since it wasn't all that stable.

CAUTION ANVIL PORN not for the faint of heart

335614517.jpg
 
my plates are the same size but only 1 inch thick
i also haveaq HF 12 ton shop press that i clamp with

how thick blade stock are you working with
 
Harry that is some hot anvil on anvil action, LITERALLY! :D

You should caption it "how little anvils are made"
 
The 3V is about 5/32" thick. We apply about 200lbs of pressure to the plates and blow air on it. Most of the pressure is me. We might try a modified anvil quench by placing an anvil on top of the plates. The 3V that was quenched with the two anvils was 1/4" thick. I was really surprised the amount of heat the anvils took. You could feel the heat above the lettering on the top anvil. I'm making a new blade out of a different piece of 3V that we got on a different order to see how it hardens. Might be something with the steel. Looks to me like every thing else should be working.

We like going by the book when we heat treat and this stuff is the only steel that has given us any problems. We refuse to be beaten by it!
 
I like the anvil-quench idea. The compression from the anvil should help convert some of the retained austenite.
 
Anvil quench is a two man operation though. One moves the blade from the oven to the bottom anvil and the other places the other anvil on top. The first guy has to be quick because the anvil weighs 150 lbs and the guy holding it has a time limit imposed by the weight. A press might be more practical if pressure on the plates is that important.
 
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