Heat Treat Foil

Peter Atwood · Feb 11, 2002

OK, I finally ordered 10 ft of this stuff from TKS. I have read the how to's on wrapping the blade, including some cardboard to burn out remaining oxygen, double folding, etc. My question: Can you just dunk the whole package into your oil quench or do you have to take it out of the wrap? I'm doing O1 and also some 440C in a later and different heat cycle. I already am aware of the proper procedures for heat treating these steels just want to know about the foil. It seems to me like you don't want to take it out or you ruin the whole effect of keeping it out of the air. On the other hand, maybe you don't get a good quench with that metal skin wrapped around it. SO what's the deal here?

GavinD · Feb 12, 2002

Peter

You need to remove the blade from the foil before you quench it in the oil. If you leave the blade in the foil envelope, it acts as a shield and you don't quench the knife as fast as you should. All the foil is for is to prevent a thermal shock to your blade when putting it in the oven and it also creates a oxygine free environment to eliminate scale on the blade.

CJM · Feb 12, 2002

take the blade out of the foil- i always have everything ready to cut the foil and pull the blade out as quickly as i can for the quench. i did read somewhere that you should leave it in the foil but i use air hardening steel most of the time and i want to expose the steel as quickly as i can- i have enjoyed good results fro this practice.

Danbo · Feb 12, 2002

Excuse my ignorance, but I thought that the heat treating foil was only for the air hardening steels. ???

Peter Atwood · Feb 12, 2002

OK, so the idea here is to cut down on the amount of scale, not too eliminate it altogether. Dang! And here I was hoping for a fairly clean blade...

Epsilon · Feb 12, 2002

Heat treating foil is primarily designed to prevent oxidation (scale) and decarburization (loss of carbon at the very surface). In some cases it may prevent it completely, in many cases it simply cuts back on most of it. This is the primary reason there are vacuum and controlled atmosphere kilns. All to keep the oxygen out.

As far as quenching with the foil on, it was not designed for that. However, it can be done very successfully. Success will largely depend on the steel type you are using and how thick the steel and amount of foil also. Example: With carbon steels I would not recommend it. Carbon steels are shallow hardening. They need to be quenched fast to fully harden in the cross section of a knife blade. I feel the insulation of the foil will give unequal or insufficient cooling rates and result in spotty hardness. It is recommended to use bare steel or have a way to be absolutely sure the surface is cooling equally. That brownells stuff might work, but talk to someone who has tried it for hardening carbon steel first. --- Now, with most martensitic stainless steels, they are relatively deep hardening, so an oil quench is typically more than enough cooling rate. In other words, the insulation caused by the foil will not (adversely) effect the through hardening characteristics (for knife cross sections). With the stainless steels and other steel that highly "recommend" an air quench with their respective heat treatment - they are essentially even more prone to deep hardening and this includes thermal shock, so oil would be too fast. In other words you can hold that air hardening steel in the foil, in front of a forced air stream and it will harden plenty sufficient.

I'm speaking very generally here guys. So don't jump on me for being non-specific... which would take up waaay to much space otherwise.

ha ha

L6steel · Feb 12, 2002

Peter, I've been wondering the same thing. I can't get a difinitive answer so I'm just going to do some tests. I'm going to take a section of each steel I use and try quenching in oil in the wrap, then take them out and break them to check the grain structure. I would like to send them off to have them tested on a hardness tester too.

Epsilon · Feb 13, 2002

I would really like to hear about your results should you conduct that breaking test L6. It will be interesting I'm sure. And fun.

Bart student · Feb 15, 2002

hello folks,

I've done lots of D2 lately, and I have stainless steel foil here (the darn stuff cuts me more then i actually use it), but all I really use it for is for making cups to catch the molten salt from my salt baths for Heat-treathing.

No kidding .. zero decarb, zero scaling. And heck, you can even quench you knives with the salt on it !

I got myself HTíng foil a while back for D2 and A2... then I began experimenting with saltbaths, and I found them to be a way better alternative. But more dangerous tough, because the stuff boils easy and likes to splatter around when inserting/removing stuff. I can tell, the burn a drop of molten salt makes, is very painfull, and doesn't heal in two days.

Just my opinion

greetz and take care, bart.