Sub-Zero quench & ATS-34

I wouldn't like to spend hard earned money on a ATS-34 blade quenched in H2O. You're begging for the blade to break under semi-harsh working conditions by doing that.

Just because he's been doing it that way for a long time doesn't mean he knows what he's talking about. The fact that he blows off cryogenics without even considering the process shows me he's narrow minded. Most people who claim vehemently that they are masters are usually idiots in disguise.
 
fenixforge:
Another source for LN is your local dairy farmer supply, they also have containers for storage etc.

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P.J.
YES,it is sharp, just keep your fingers out of the way!
www.silverstar.com/turnermfg


 
mr martin is very thorough..its all about complete martensite transformation....and liquid nitrogen is a key element..or should i say the 300 degrees below zero is. heat treating is not just making steel hard, it is a complete transformation of the molecules....and there is a lot that does not meet the eye....a lot of guys who are sticking their knives in their 500 dollar oven and then some dry ice are kidding themselves...even if the finished product comes out to Rc 59, or whatever they are hoping for....

[This message has been edited by tom mayo (edited 12 May 1999).]

[This message has been edited by tom mayo (edited 12 May 1999).]
 
All the tests I've seen have indicated no effect on low-alloy steels. If anybody has evidence cryo can make a detectable difference with steels such as 1095 I'm interested.

I'm not trying to start a flame war -- I don't claim to have seen every test that's been done....

-Cougar Allen :{)
 
Cougar: As I indicated, low alloy steels have significantly higher Martensite Finish Temperatures than higher alloyed steels, so, it doesn't surprise me that the data is inconclusive-properly heat treated low alloy steels should transform more thoroughly without the cryo. However, you should also remember that it is very difficult to collect data on the qualities of toughness, wear resistance, flexibility etc.
Real scientific data required MANY data points in order to weed out the scatter, and, setting up tests that actually tell you what you want is difficult and costly.
My thought, as a professional knifemaker, is that, if I can perform this treatment at a reasonable cost, and it offers some benefit, however small, then, why not JUST DO IT!

RJ Martin
 
So, if I get this straight, I can just take a completed blade, like on my ATS-34 Pioneer, and stick it in liquid nitrogen, and the performance will improve? Or does the cry treatment need to be done at the same time as the heat treat? (By the way, my Pioneer has the best ATS-34 blade I've ever seen).
 
Cougar brings up a question that just started to form in my mind. Is there a "sliding scale" of how much improvement you'll see by using a cryo process on a blade, ie. the higher the percentage of alloy content of the steel, the greater the effects of the cold treatment? Or does one sort of steel family (air, oil, or water quench) show a different range of martensite conversion? For example, will it help oil quenched steels 5-8%, water quenched 12-15%, but only 2-4% for air? I don't know if I'm expressing the question properly, maybe someone can interpret or translate my babble.

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Don LeHue

The pen is mightier than the sword...outside of arm's reach. Modify radius accordingly for rifle.


 
Guys: I think you are overanalyzing the issue! Cryo treatment can be done any time after the first temper. Treatment should last 24 hours, minimum, although some may dispute this. A stress relief at 300F is VERY desireable after LN2 treatment. I perform 2 additional full tempers on my blades. Remember, if you are forming more Martensite during cryo treatment, that Martensite is useless to you unless it's tempered/stress relieved.

RJ Martin
 
All the evidence I've seen shows cryo treatment of finished products long after heat-treatment has no effect. You have to start the heat-treatment all over again for it to work.

I've never seen any evidence cryo can do any harm -- there's surely no harm in cryo-treating low-alloy steels or doing it to a knife or rifle barrel you have around ... it just won't do any good.

I think there is a "sliding scale".... I think it depends on just what heat-treatment you're comparing to; cryo may produce better results than one non-cryo procedure but not better than another non-cryo procedure with a given steel. Some steels definitely respond better to cryo than to any non-cryo treatment. I think low-alloy steels such as 1095 and O-1 are off the scale completely and are not affected by cryo treatment, unless in comparison to a badly done non-cryo treatment.

As rj martin pointed out, absolute truth isn't easy to determine. Hucksters are taking advantage of the present uncertainty to market treatments that pretty definitely have no effect whatever. Others such as rj martin (he's no huckster) are experimenting with cryo and trying it on everything and why not? Once you set up for it it isn't expensive and you might as well throw some O-1 blades into the liquid nitrogen too, and see what happens. If it seems to come out a little better than the treatment you were using before -- well, a scientist might want to conduct exhaustive experiments to determine whether he can get as good results with another non-cryo treatment, but a knifemaker just tries this and that and uses the best heat-treatment he currently knows of, and often keeps experimenting and looking for a better way throughout his career.

I am suspicious of advertisers who claim their low-alloy blades are better than the competition because they use cryo and I am more than suspicious of companies who claim paying them to dunk your old knife in liquid nitrogen will accomplish anything, but I'm not suspicious of rj martin at all.

-Cougar Allen :{)
 
Cougar: Thanks for your kind words. I believe you aptly stated the difference between a Scientist and an Engineer. While the Scientist is debating the issue, the Engineer is out putting it in practice-and reaping the benefits.

However, as I understand it, Cryo treatment DOES NOT need to be performed within a certain time of the initial heat treatment. This was the old way of thinking I mentioned from my college textbooks. It will have a positive effect when performed any time AFTER the first temper. Additional tempers, or a stress relief at 300F as a minimum, should be performed after the cryo treatment. You will see great performance improvements in gun barrels, for example. these barrels can be barrels that were removed from finished guns, cryo treated, and reassembled. They shoot better-even though the initial barrel might have been heat treated years before, when the gun was built at the factory.

What IS critical in heat treatment is that the first temper be performed IMMEDIATELY after the quench, preferably starting when the blades reach about 150F. Allowing the quenched blades to go untempered for longer than an hour or two will diminish the results. I'm sure that many will dispute this, as it is sometimes very convenient not to temper immediately, but, it is the better approach.

Stay Cool, REALLY COOL!

RJ Martin
 
That's interesting. All those negative results I mentioned were from just dunking it in liquid nitrogen without retempering afterward, so they're irrelevant. Dunking and tempering is a little more work than just dunking, but much less than starting the whole process over....

-Cougar Allen :{)
 
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