>>893507Saw blades and other tools tend to be made of hardenable carbon steel, with the exception of files from China or India, which are usually only case hardened and not suitable for making a blade. Although like everyone else said, the steel is way too thin for the type of blade you are makinag.
As far as hardening and heat treatment is concerned, since you are working with a "mystery metal", it's next to impossible to tell you exactly how to quench and temper it, but there are some basics you can follow. You're going to want to heat the blade until it reaches the point that it loses its magnetism, which of course you can check with a magnet.
Once it the blade has reached the critical point you are going to want to submerge it entirely in oil very quickly. There is definitely a chance of flames, so use a long set of tongs along with welding or Blacksmithing gloves, and make sure there is nothing flammable nearby. Warmed peanut oil will work as a quenchent with the added bonus of smelling delicious. You are going to want to leave the blade in the oil until it cools down to a temperature that you can hold with your hands.
To temper it, stick the blade in an oven pre-heated to 400F as soon as it's cooled down, but be careful because the blade is going to be very brittle. Bake it for atleast two hours.
After all this is done, there should be a little bit more of cleaning and sharpening to go, but it's pretty much done.
If you decide to make another knife, if it's possible buy something like O-1 tool steel, which will be easy enough to find out the hardening temperature, quenchent, and temper temperatures.
