If one is set up to forge, any old leaf spring is excellent. I prefer the “found on the side of the road” brand.
Be warned, leaf spring is tough and if not annealed working it can wear one out
If no forge is available, I recommend, and use, old wore out lawn mower blades . My preferred brands are “free for the taking” and “I’m throwing it out anyway” .
lawn mower blades, while soft by modern standards, are better steel than the originals, and yet are still easily worked with a hack saw, files, and a bench grinder.
I found that old circular saw blades are “iffy” . they are thinner than mower blades or leaf spring, if thinner is desired, so less work. Modern 7 1/4 inch or 10 inch either have hardened teeth or carbide tooth “inserts“ . one should anneal The body of the blade for ease of cutting, but due to the shape and size it can be a chore compared to mower blades….
oh, any old fire that will heat the metal up to the point that a magnet wont stick will work for annealing.
then bury the metal in ashes or hot sand so as to cool it slowly.
yhs
shunka