Straightening the front bumper

[wrndln]

I have a front bumper in good replated condition. However, it is bowed in about 1/2" inward. I don't know why the plating company didn't straighten it before replating, but they didn't. I believe bumpers are made of spring steel, so they would tend to return to the original bent inward position when straightening is attempted. Does anyone know a good way to straighten an original replated bumper?
Thank for any suggestions
Rusty Nelson