You can also use old files. Truck leaf springs. Or old knives (meat cleavers).
You can make a blade out of anything, but it's nice to know what kind of steel it is so you can properly treat it.
My first knife, made from a file, I never got it too hot to hold, never heat treated it. It would not stand a chance in the torture test of bending it in a vise, but it will gut 2 deer and still shave hair, which is good enough for most of us.
Dan