Leaf spring re-arching.

The only way I could see making it last long term is with a large forge type planishing hammer and drawing it back and forth several times followed by a cryogenic treatment, as in liquid nitrogen quench immediately after shaping to return the grain structure to normal after the heat the hammer would put into it. I don't know if it would work or not because the last time I checked the "perfessionals" in the spring business use a large slip roll to return the arch to about 98 percent and then put at least one minimally thicker new long leaf towards the middle of the stack with extra arch to return the shape to original and help the stack hold its shape long term.