You really need a through-hardenable alloy for knife blades. So you are going to be looking for tool steels, as an example. This would include discarded punch tools (punches and dies for poking holes in steel), shear blades, coining tools, metal dies, etc.
Frequently in press tools, the only bits that are tool steel are the small pieces that actually form the metal. The rest of the tool is made of common steel, where enough of it is used to provide the required underlying structure.
Look to industries in your area that work with sheet metal or produce part "blanks". Generally, these folks will, at some point, discard edge tools that can no longer be worked into a workable edge or device, and you may be able to get them.
The other thing I would suggest is automotive leaf springs. These can be had at the local salvage yard and are started down the road of being the right shape. They are high enough carbon content to hold a decent edge (especially for more decorative blades).
After working into your desired blade - heat to "red hot" and oil quench. Then reheat to about 800°F (this can be done by eyeball with a little practice) and cool slowly to temper a bit.
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