Thread: Heat-Treating Basics

foil wrap is not used for the most part on oil quench or water quench steels
most makers i know leave a bit of extra thickness on the blade before heat treat and then grind clean
alot of production knife makers grind there blanks full hard and not even part ground before heat treat (shaped yes but not beveled )


for the more simple steels 10xx and the like the quench from temp is only around 1500 ish and soak times are short so decarb may not be a big deal

not like when i do SS at 2050f for a 30 min soak. with out foil there would be nothing left of the blade to use

Originally Posted by Joed

To reduce the loss of carbon to the atmosphere furnaces have an atmosphere control. I believe they flood the furnace chamber with nitrogen but it may be some other inert gas that is used. These furnaces are more expensive and typically not in smaller machine shops that do their own heat treating. To avoid the carbon loss the items being heat threated are put in a metal foil pouch that is sealed by folding the edges over several times.

The gas is argon. It is actually available in small kilns too. Flooding of the chamber tends to ruin the elements quickly and most manufacturers warn against this. I've known knifemakers who have tried HT with and without the argon flood... Without works better. Butch is right that the foil is only really used on Stainless.

So, when quenching, if you were to use something really cold, it would trap more of the carbon, right? Leaving you with a harder steel?

That is logical thinking but it is the wrong thing to do. Think in terms of thermal shock. If you take a high carbon steel and quench it in cold water then it will most likely crack the blade or warp it.
Generally speaking I have the quench at 100 degrees or better for 1095 steel.

You will learn, as I did, the hard way!

Can a benefit be had in quenching in steps or would the stress added to the metal just stack up? Would you be able to use a progression, like kiln to 100 degree water, 100 degree water to ice water, ice water to ?, or some other kind of progression? Or do the effects of the thermal shock remain within the steel forever, leaving you always worried about further stress?

The stress would not add up.

What kind of steel are you talking about?

Originally Posted by randydance062449

What kind of steel are you talking about?

I'm not sure. I really don't know that much about steel. This post has gotten me to think about it a bit. On that thought, everything being steel, is there a huge difference in the tolerances of different types of steel in the quenching process (do they all like to be quenched in something that is above 100 degrees)? Is it safe to say that a more brittle steel would be more prone to cracking while a milder steel would like to warp? Does the metal warp because that is how the steel wants to naturally line itself up, or does it warp because the metal is cooling at different rates in different spots? Is there a case where warping could be a good thing? I was asking about the quench because I have a stainless dovo that says that it is ice hardened or ice tempered, or something of that nature on the blade. For some reason I was under the impression that it had to do with the quenching process. I don't know where else ice could be added to the process.

ice hardening is a marketing catch term
as if truly ice hardened would refer to a cryo of the blades at some point in the tempering

in truth ice will not help the blade in a way that you could tell in most any testing
dry ice could but thats not the same
and LN has shown that it can help some steels

the more complex the steel / heat treatment the more likely that a cryo would help the blade
i do not cryo any of the 10xx steels as there is little to no help by doing it
im still testing cryo on O1 and 52100
i do cryo every blade in cpm154 and cpm3v s30v D2 and M4
im sure i have done other steels also that i forgot to list

If you really want to learn about steels then a good starting point is Bladeforums.com. Look for posts by Kevin Cashen. he also has a website with a lot of good info. Your getting into a lot of technical detail here.