There is the right way to heat treat O-1, and then there are the hundreds of ways that us folk without the right kit attempt to approximate those results.
Its for that reason than trying to use a "recipe" from someone else who doesn't have the right gear either can be a little dodgy. Their perception of colour will differ (for instance, nothing I have ever hardened has looked cherry red, dull or otherwise, at the time it has become non-magnetic, it all looks orange to me
), their quench media will differ, and the way that their tempering set up works will differ.
Best advice is to get a little bar of steel, whatever you will be working, O-1 or whatever, and do tests. Separate your hardening and tempering processes and just try things. Try cycling, multi-quench, single quench, trying to hold at temperature, and quenching immediately on a rising heat. Tempering is easier to experiment with as long as you start off by aiming low, you can always retemper something that is too hard, but if you use too much heat, and leave it a moment too long, you can't get the hardness back. By testing you will get a feel for the steel without having to wait to make a blade, or risk the grain growing through over heating or decarbing the edge in the fire, or warping or cracking on the quench.
Hillbill
I guess that the reason for foil is to prevent the blade getting hotter, through radiant heat, than the air in the oven, which is probably what the sensor measures. Have you tried it with and without foil? How did it compare? I would have thought that the variability in a forge hardening process would overshadow the effect of radiant heat in tempering
A friend of mine who has an Evenheat oven, and can really control the process, uses a fish steamer full of sand to even out the tempering temperature, but he can control everything to +/- a degree or so.:Wow:
Robin
Interesting way of getting the results you want! Setting a higher temperature of 220C probably gives satisfactory results because you A) don't leave it in there long and B) keep opening the door. So the blades may never get to 220C and if they did, they would be out and cooling immediately. My oven appears to slowly ramp up in temperature so that the longer I leave things in there, the hotter they get, despite the setting on the dial. However, it takes an hour for that to happen, so I am able to leave blades for an hour to an hour ten minutes and they come out fine. My parent's oven on the other hand (its a new fangled fan assisted thing) never gets hot enough to temper anything even slightly
Only after a very frustrating couple of hours was I told that they had never got it to bake bread properly either
I am the sort of person who is never entirely satisfied with my work, I am always aiming to improve and I like to get a head start on experimenting by reading up on stuff first. I found the following information by Kevin Cashen to be very interesting and useful. He has written some really good stuff on the US forums about heat treating in general, and O-1 in particular.
Info on O-1,
http://www.cashenblades.com/Info/Steel/O1.html
In tempering the end result is effected by two factors, time and temperature. Of these temperature has the most immediate and profound affect. Time at temperature has a more subtle effect, relieving stresses and increasing toughness with less loss of hardness.
http://www.cashenblades.com/Info/Tempering.html
An article on metallurgy made easy
http://swordforum.com/metallurgy/ites.html