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Triple Quenching and Triple Tempering


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#1 ScottB

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Posted 30 January 2004 - 07:29 AM

Not sure what the triple quenching does, even though I practice it.  It was suggested that it refines the grain a bit more, but I'm not learned enough to be sure.  I just follow the advice of guys that have spent more time than I have in this game (though that doesn't always make them right, ofcourse.  Still, got to start somewhere).  

The triple tempering, though, I can explain a bit.  The first draw is  
more or less stress relief.  The second and third serve that purpose as well, but also serve to temper any new martensite that may have been tripped over from retained austinite in the first quench.  The new martensite, ofcourse, would add more stresses and some brittleness back in.  So the cycles do have a reason.  Some only do 2.  I've seen that some don't do more than one tempering cycle.  I do the 3... I just like to be sure.

Now, having said all that, I've got to add that I know nothing about anything, so I will allow smarter folks than I to confirm or deny what I've just said.  :)


#2 Andy Prisco

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Posted 30 January 2004 - 02:45 AM

What performance advantage(s) does Triple Quenching provide?  Are they significant in terms of the user's awareness?

Also, I've heard and read some ad copy about "triple tempering" among custom and factory knifemakers...what the heck does THAT do?  Does it just keep drawing the hardness back or does it relieve stress or ???

Thanks in advance...


#3 Bearpaw

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Posted 30 January 2004 - 08:34 PM

Andy,

As the steel comes from the mill, it has a small grain structure. Stock removing a blade does not change the grain. Forging a blade will enlarge the grain growth, although using lower temps with each heat helps reduce the grain growth. After forging, thermal cycling will reduce the grain in the blade. Bring the blade to non-magnetic and quench in preheated oil, completeing this proceedure 3 times. Sam Currie demonstrated this with a forged bar of high carbon steel. After the first cycle, he put the bar in a vise and snapped off a piece. The grain was large. Second cycle and breaking off another piece showed a finer grain and after the third cycle, the piece showed a fine grain.
Bearpaw





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