Heat treatment for Blades

Joined
Nov 14, 2000
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This is my first post so I wanted to ask a question I that I'm interested in but have seen no discustion about.
Does anyone know about heat treatments and how they effect blade performance? Also which woke best with what kind of steel. I would imagin the case hardened wouldn'y be good becouse you could sharpen though the treatment. Also does anyone know about cryogen treatment for blades, I've never heard about it and I am interested in hearing more about it.

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In battle, use the common to engage the enemy and the uncommon to gain victory. - Sun Tzu
 
Joined
Nov 6, 1999
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Saberman, this is a good question for the shop talk forum. It is also a good question for the general forum. Your question is a little open ended however. I could go on for hours about the complexity of heat treatment and the effect of alloys on steel as blade material. I'll get back to this thread a little later. Anyone else want to tackle this complex question?

Paracelsus
 
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Oct 9, 2000
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Yeah, if I had 2 or 3 days, good luck Saberman, your in for alot of GOOD reading.
Welcome Aboard!!
 
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Nov 14, 2000
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I have an old Machinist's Handbook, and looked though alot on the stuff in there. But it doesn't have anything on the newer materials. I think what I'm looking for is a site or something that I can look at and learn more on the new blade steels and processes on their heat treatment.
 
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You really need to correspond with a knifemaker who will be able to help you more, but this site has good information on the standard heat treatments for a large number of different blade steels.

Heat treatment actually implys several different steps. Annealing, or softening, is done by heating to the critical temperature (maybe 1800 degrees) and cooling very slowing. This results in the softest steel that can be cut and shaped more easily.

Normalization is a different process whose goal is to remove internal stresses after grinding.

Hardening is done near the end of blade production by heating to the critical temperature and cooling (quenching) very rapidly. How fast to cool the blade depends greatly on the alloy. The goal here is to make the blade as hard as the alloy will allow, to maximize the formation of martensite crystals (the really hard stuff).

The final heat-treatment step is tempering. This step involves lowering the hardness by heating the blade at lower temperatures (a few hundred degrees) to melt down some of the martensitic matrix into a more pliable (tougher) material that will hold an edge but is not to brittle.

Heat treatment is the Most important aspect of blade making. It is far more important than the mixture of elements in the steel (the alloy). Unfortunately, it is also the hardest thing to measure in a finished blade. The RC (hardness) will give you some indication of how well a blade was heat-treated, but that is a very imprecise measurement of blade performance. Some makers also use cold treatments (cryo) on some blade steels to refine the crystalline nature of the hardened steel.

Case hardening is completely unsuitable for knife blades.

The best way to heat any particular steel is a matter of opinion. Many makers will heat treat the same steel in different ways. The proper heat-treatment for different steels can be quite different. Some steels benifit from rapid quenching from the critical temperature. Others need to air harden. And I have not even mentioned differential heat treatments (making the edge hard, and the spine soft to balance edge holding and toughness).

Anyway, that is a quick review of the major heat treating steps and their purpose. I sense that you already understand these processes and seek more detailed information on how to treat particular steels. Look at the link I provided and see what develops from your thread in the shop talk forum. Good luck!
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Paracelsus

[This message has been edited by Paracelsus (edited 11-17-2000).]
 
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Paracelsus,
Thanks alot, that is a great site with a lot of good information
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. I think that it will give me the types of information I am looking for. Again, Thanxs for the help

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In battle, use the common to engage the enemy and the uncommon to gain victory. - Sun Tzu
 
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