Here’s another technique you might try.
Clamp one end of the wire in a vise. Clamp a hook in the the
chuck of a drill (electric or manual; electric works easier).
Attach the other end of the wire to the hook. Draw the wire taut
with the drill. While holding the wire taut, start the drill &
run it until the wire breaks. The wire will be hard & straight.
You may see a spiral pattern on the surface of the wire. This is
only a surface condition & comes off when the item is polished.
Any length (several inches to many feet) of wire can be hardened
& straighten this way.