triple quench

When doing a triple quench,what is gained?
What is going on inside the steel?
Testing I have done shows that reheating the blade burns out carbon for zero gain(most times loss) of Rockwell hardness.
Doesn't a single quench,done properly,result in maximum hardness?
 
M

magnum .44

Joined
Jun 12, 1999
Messages
1,110
i think it's triple tempering that they're doing. the first temper is to get the blade down to a certain hardness, then the extra two (at the same temp) are for stress relief.
 
My impression is that multiple quenching refines the grain structure of the steel which both toughens it and makes it take a sharper edge. Ed Caffrey really works on the multiple quench process. Below is a quote from a previous thread:

"Although I have not tested all the steels with a multiple quench (and most likely never will), I have found that those steels that possess a mild to moderate (moderate meaning not more than 5%) Cr. content respond very well to this type of process. There are a couple of very simple steps that actually serve to enhance grain structure during the multiple quench process. When I first started this process on my cutlery, I thought that the steel was getting "softer" after each quench cycle, but after having several samples spectrographed, I discovered that the grain was being refined with each successive quench cycle.....up to general number of quench cycles. I can't present you with undisputable scientific proof, but I certainly believe in it. During these tests I was so certain that there was something major, that I was either doing right, or wrong, and only when the spectrograph results came in, did I realize that in knifemaking, it is more often than not the "little" steps that make either monumental improvements, or heartbreaking failures."

 
Adding to what Jeff posted.......one of the "little steps" that I spoke about in that post was the fact of never removing the blade being quenched from the oil. Once the blade has cooled to the point where no further transformation takes place (once no more fumes are rising from the blade), I simply slide the blade off the limiter plate in my quench tank, and allow it to cool overnight in the oil. From experiments conducted by quenching two blades, and leaving one in the oil to cool, and the other left in the open air overnight, it is a fact that the one cooled int the oil with exhibit a finer grain structure. I'm not really sure how to term this.........but in my mind, I view it as a reaction on the grain sturcture, similar to that which annealing provides. Sort of like a hardening/grain refinment in one operation.
To respond to Rex's initial question......Maximum hardness is not the objective when seeking what I call "The Overall package" in a blade. It's more a search for "happy mediums". Having a blade that is at it's maximum hardness creates other difficulties with durability, sharpening, and flexibility.....Things that over the years people have told me that they despise in a blade. Most bladesmiths can produce a blade that would literally be capable of cutting another knife blade in half, but in order to do that, the blade would be as brittle as glass, and be like sharpening a diamond. All I can say is by listening to my customers (actual and potential), along with the drive to never stop improving, I keep experimenting, and discovering new things with each trip to the forge.

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
Thanks for the replies.
Ed, I realize that maximum hardness is not the goal.My question is,if multiple quench causes carbon burnout,{and it does, I have the test data to show it,}what is gained?
I believe you and others who say that they get a better cuttiing blade.Too many prople have had similar results to disbelieve.
If its not a question of hardness,than what causes the improvment?
 
Rex,
I follow your thinking on the decarb. The rate at which this occurs depends greatly on the temp, and the duration that temp is maintained (or exceeded). When using steels that respond well to the mulitple quench, soak times are certainly a "no, no", as it will degrade carbon content, particularly in the thinner cross sections of the blade. When using this method of hardending, the blade should be at critical not longer than necessary, and all dimensions of the blade should be left over sized by around 10%. By limiting the time the steel is exposed to critical temp you limit the possible decarb to just a couple of thousandths, and with the 10% oversize, you have the room to grind away that portion which may have decarbed. The most benificial part of the multiple quench from my veiw point, is the reduction in grain size that can be achieved when the blade is allowed to cool in the oil between quenches. Not sure if I mentioned it before, but when I harden in this manner, it is a three day process, with approx. 24 hours between each quench. Take Care,

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
Ed I agree with you but what do you say to the guys that say the only reason that a triple quench seems to work is that you are not doing the annealing and normalizing right. NOT my words. I would like to know so I can discuss(argue) it with them.
wink.gif


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-Greg Johnson
ICQ#4236341

 
Greg,
I usually tell those folks that they need to do a little more experimenting, and see for themselves. I have done the experiments.....and I can promise that two blades, all of the steps are identical, on the steel (5160 or 52100) with the exception of one blade being multiple quench, and the other being single quenched, the multiple quenched blade will out perform it's counterpart every time. Until a person takes the time to conduct the experiments (which I feel is a very important aspect of knifemakeing) he or she simply has no first hand knowledge to dispute. When, and if folks start talking about so called "facts" that they have read of heard, I usually just shut up, and figure it's like trying to teach a pig to fetch........it wastes your time, and annoys the pig.

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
Ed, I agree with you completly about testing.
I have worked in R+Dlabs doing metallurigal/chemical testing for 20 + years. I am trying to approach this in a scientific manner and quantify what is happening inside the steel to make it perform better.
I would love to see the testing and results you have done and compare to what I am doing.
I would be willing to collaborate with SERIOUS makers who would like to try some experiments to find out what is going on and also find THE PROCESS,the one which blows all the others out of the water.
I personnally feel that the full potential of 52100 has not yet been achieved!
 
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