foil wrapping 440c blades

E

elementfe

Joined
May 3, 2008
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I've read about 35 discussions of how to heat treat 440c, and not once has anyone mentioned whether they take the foil off for the air quench.
With carbon steels, a more or less rapid quench is the objective- can anyone point me toward a chart for 440c, so I can see what it wants in terms of cooling times?
Thanks!
Andy G.
 
Andy: The more rapid the quench, the better, up until the point where you cool so fast the blade cracks. For Martensitic stainless steels like 440C, most knifemakers will press quench, using aluminum plates. Leave the blade in the packet when you quench, the idea is to get it right from the furnace to between the plates as quickly as possible.

Even if you decide to air cool, and you can do it that way, leave it in the packet to prevent decarb. If you want to air quench, I'd suggest using a fan. Just hold the blade so the edge of the knife faces the fan so that the air blows evenly over both sides of the blade.
 
Thanks for the info!
So the foil doesn't interfere with airflow over the thinner sections enough to worry about, it sounds like.
I'm thinking you'd want to have your folded over part (of the foil) on the spine of the knife, so that the edge would cool the quickest.
 
With a true air quenching steels and a plate quench the foil does not retard the cooling enough to have much effect. I did find that it made a difference with 3v, but a plate quench really needs all the help it can get with that steel, including cold or frozen plates, and cold forced air, in order to get close to the spec'd hardness. Removing the foil on the way to the quench is a hassle best avoided if possible, it introduces an unwanted variable at the most critical juncture of the process.
 
If using plates, I leave it in the packet, if quenching in air, I've always removed it. One reason to do this is that you can check the blade and do any straightening that it might need. With the plates, they tend to come out straight and I don't worry about it.
 
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