CPM154, 154CM, or ATS-34?

[AcridSaint]

If you get a really good wrap on the blades, the foil will basically vacuum to the knife and you won't have any air space in the foil. These steels will all air harden, so even if the plates are not touching at the edge, they are still pulling heat out faster and giving a better quench than in still or even moving air.

The best solution, however, is just to plate quench them before you grind them, then you don't have to worry about these things

[mete]

The high alloy steels will have RA no matter what is done.Some can have great amounts.The most significant variable is the austenitizing temperature .The higher the hardening temperature the more RA there will be. This is why we insist that these steels be treated with precise temperature and time control.
The quench is important but many makers have gone to plate quench because it rapidly drops the temperature giving proper martensite conversion and is certainly convenient. That so many successfully use it demonstrates that it's very effective.
The quench must be fast enough but also mush reach a low enough temperature to get near complete conversion.That's where cryo comes in.
The RA after quench can be reduced by cryo.But this doesn't make up for excessive austenitizing temperature !! RA is softer and tougher than martensite and in some applications some is desired. Cryo gives you harder more wear resistant blades.
The best blades come from a complete understanding of the whole HT process and precise control.

[Bear_Blade]

Thanks for the lesson Mete, I have more research and reading to do, but this was a good start. Thanks for taking the time to help make this more clear.

[Andrew Garrett]

The plate quench debate raged around here a few years ago. In following that thread, I remember an important lesson which stuck with me and just rang true.

Another poster was concerned that the edge would not quench because it did not have direct contact with the plate.

The fact is that this is the BEST set-up! Think about it like this: It is a heat 'draw'--All of that heat has to pass through the point where the hot steel contacts the 'cold' plates. That means that the point of contact is the LAST place to cool down. The thinnest most distant areas of the steel will surrender retained heat the fastest as the cool plates draw it out.

I think of it like a 'wick' effect. All of the wax burned in a candle passes through the wick. Likewise: all of the ink in a ball point pen must pass through the point of contact. Thus, the first part of the ink-tube to empty, is the part farthest away from the paper.

I hope this helps.

[Bear_Blade]

UPDATE!!

The guys doing the test have decided to do another knife useing CPM154 but this one will benifit from the cryo treatment. Again, tested by people other than the maker.

Will pass along updates, and results.

[CWKnifeman]

I have to agree with Mete The need for Cyro is a must of you plan on obtaining an optinum blade for any high composition steel. If you check with Crucible for the heat treat spec's you will see this. Not only for the cpm154cm, and 154cm that they make , but also for ATS-34. Cyro os actually part of the heat treat process for all of these steels.
Curtis Wilson

[Bear_Blade]

Thanks again Curtis, again, I will pass along this info. Unfortunatly, I will not be able to attend the symposium, but I will get all the "dirt" later.

[Bear_Blade]

UPDATE:
Well guys, I thought it only fitting to let you all in on the results, as unscientific as they may be.

Three knives were constructed as origionaly stated, CPM154 without cryo, CPM154 with cryo, ATS-34 no cryo.
All three constructed as close an possible to the same dimensions/geometry, by one maker. The cutting was done on a new length of 3/4" polly rope, and each knife was pushed to the point that it wouldn't/couldn't cut any more.

The results kinda surprised me, I was unable to make it to the symposium, but here are the results.

CPM154 no cryo: 377 cuts

CPM154 with cryo 454 cuts

ATS-34 no cryo 527 cuts, and still cutting.

The counting stopped with the ATS-34, due to the blisters. Some 18 different cutters pushed the blades through the rope, til they wore out.

Like I said, not really scientific, but a real world test none the less I think.
But I am curious as why the untreated ATS-34 did so well, I had expected the cryo treated CPM154 to be a clear winner.

Any comments welcome.

[Ray Rogers]

Without laboratory testing, I doubt anyone can tell you with certainty what happened with the CPM blades but I do have an opinion (which shouldn't come as a surprise to anyone).

I had worked with ATS-34, BG-42, and 440V for a long time before S30V (another partical metal steel like the CPM steels being tested). When I got my first bar of S30V I read all the factory specs on how to heat treat it and I noticed there were at least three different ways the factory said would work. Naturally, I picked the simplest one and used it on my first blade (with cryo). Lousy. It was a blade and it would cut but not as well as ATS-34 or BG-34 or even 440C (not V). Scratched my head, made another blade and tried H/T version #2. Better, but still disappointing compared to the other steels and not up to the hype on S30V.

Finally, I read between the lines on method #3 (the most difficult) and talked to some other people. In the end, I had to switch quenchants to Brownell's Tough Quench and heat the Tough Quench to 150 F. Hold the steel at 2000 F (the most my oven will do and really not quite enough) for 30 minutes, quench until the steel falls below 1000 F (that's an interrupted quench), then air blast at 2 atmosphere's minimum until the steel reaches 125 F. Into the cryo overnight (more than needed I suppose but convenient for me), then temper two or three times for 2 hours each.

That's a good bit more work than the other steels required and the S30V needed a faster quenchant too. I don't know if my S30V blade would out perform your test blade but they do outperform my ATS-34 blades.

What all this boils down to is that CPM steels can be much more complex to H/T to get the performance everyone brags about out of them. he simple methods make a blade but not a great blade. Maybe your guys did all this sort of thing but if they didn't the answer to your dilemma can probably be found in that area ...

[dbalfa]

...a perfect result means nothing with p=.01

sorry, just had a flashback of statistics class...

[dbalfa]

Originally Posted by AcridSaint

If you get a really good wrap on the blades, the foil will basically vacuum to the knife and you won't have any air space in the foil.

I don't mean to drag anybody off subject here, but this statement by Cap caught my eye because I had an experience this evening with this I planned on discussing:

I HT'd a ATS-34 blade tonight and when I pulled it out, the package was blown up like a baloon. I had wrapped the blade with paper towel and double seemed the wrap, hammering the folds down with a soft rubber hammer. There was absolutely no signs of a hole in the wrap. That would seem to be the opposite of what Cap said above. What is going on, anybody have similar results? I say similar because the last three blades I treated did this. The only one that hasn't I know had a pin-hole because I say the flare-up when I placed it in the oven.

Anyway, I put it between the plates and mashed them down on it. This gave me further proof that it was sealed because it took a bit of weight to collapse the capsule.
The blade seems OK, I file tested it and it was hard. What gives?

[AcridSaint]

Dennis - maybe my wraps are usually less than really good? I've never put paper towel in with the blades, only used paper once that I recall. Generally, when I'm looking for is a tight wrap that has virtually no air space when it goes into the oven, then when it heats up maybe there's slightly less seal and it burns up what little air is left in the pack?

[Ray Rogers]

I'm only guessing here because I've never used a wrap but I'd say the package ballooned up because you succeeded in getting a truly air tight seal and you used the paper towel.

I know you used the towel in an attempt to burn up any remaining air in the package I'll also guess that most times the wrap isn't 100% air tight and it wouldn't matter if it wasn't as long as it kept air from circulating around the steel and it can do that without being a perfect seal. But this time you got a perfect seal, the paper towel scorched which gave off smoke and whatever gasses paper can release and these gasses and smoke inflated your package.

Just a theory but I'd say you don't need to use the paper towel and a perfect seal is good if you can get it but not required ...

[CWKnifeman]

I have been using paper towels for over 10 years to burn off excess gas
(0xygen) from the wrap. I have had some to baloon up but rarley. The reason for the paper towel is to decrease the decarb (carbon pulled out of the blade during the heat treat). I normally will have a very clean blade when it comes out of the wrap. I also have found that I have a less likelyhood of having a blade warp using this process.
Curtis Wilson

[Bear_Blade]

In regard to the foil wrap, at the temp necessary to HT stainless steels, is there a concern that the chrome in the alloy may "boil off" the surface, possibly leaving a not quite as stainless surface? Or maybe better put this way... How do you ensure the finish on a proprely HT'ed blade is not going to rust? When useing a salt bath, a layer of the blade needs to be ground off, to again be stainless, is this also the case when useing foil and an oven? (sorry guys, I don't have much experience with ovens, But I am thinking I want to get one)