Question: When To Use HT Foil?

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gocopss

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Nov 10, 2014
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My question is when should you use foil for heat treating? I heard that it shouldn't be used on some knives like 10xx, but what about stainless? Also what about tempering? This might be a stupid question, but I am new to making knives.

I am asking the first part for everyone else that is curious (unless I am the only moron) because I did not see a answer. I want to know if I should wrap S35vn in foil during heat treatment (maybe I should phrase this as a question).

I apologize if this is a stupid thread, useless, offensive, immoral, repost, or in the wrong location.
 
When you heat the steel above decarburizing temp (700c) for long period of time such as heat treating stainless/high alloy. You don't need to wrap low alloy which need short time of soaking like 10xx, W2, O1, 52100.
 
It's also just logistically a pain for anything other than air quenching steels. It's one thing to unwrap a piece of A2 knowing you have the time. It's impossible to unwrap something like 1095 fast enough, or close enough to impossible as to not be worth the effort.
 
Yes....for S35vn foil is required for high heat and time at Austinizing temp (1900-2000F..15-30 minute hold time). There are 2 stainless foils available Low temp-1800 degrees and High Temp 2300 degrees you need the 2300 degree which will cover all high alloys you may use in the future. Foil is not required during the tempering cycles.

To reach those temps you need a Furnace/kiln to regulate and hold constant temps.
 
Wrap air hardening steels that harden simply by slow cooling after removing from oven.
Do not wrap steels that require quenching in liquid/oil quenchants. These steels need to be at full oven temp when quenched in the oil and it would be nearly impossible to remove them from the foil packet soon enough.

The reason for the foil in the first place is to protect the steel's surface from extreme oxidation/scaling as a result of being in contact with high heat oxygen. The foil packet is an oxygen free environment which protects the steels surface while sitting at very high heats for long periods of time.
Think of the burnt surface of a piece of toast left in the toaster too long.
Air hardening steels often require heats in excess of 1900 for long, long periods of time, which can result in excessive scaling, so they need to be protected.
The simple carbon steels may only need to be in temps of 1500 for a few minutes before quenching, which results in much less scaling. In these situations, extra steel is left on the blade to be ground off to clean steel below.
 
I use it for spheroidizing or stress relieving carbon steel.
 
Thanks for the replies! I didn't know how many would reply or how long it would take.
Forgot to mention this: I heard about heat treating before grinding since you would remove oxidation after heat treating. This makes some sense, but that makes it harder to remove steel...
 
gocopss said:
Thanks for the replies! I didn't know how many would reply or how long it would take.
Forgot to mention this: I heard about heat treating before grinding since you would remove oxidation after heat treating. This makes some sense, but that makes it harder to remove steel...
Click to expand...

They usually do that with really thin kitchen knives. You have to be careful about wetting the blade so it doesn't ruin the HT. A bunch of people has systems set up that keep the belt wet, sponge dripper or something like that.
 
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