3/8 th inch rebar? I would just bend it cold. You mention both 7 inch
radius and 7 inch diameter, so I am not sure which you mean. But pick
something somewhat smaller as there will be some springback.
Maybe slip a 1/2 inch pipe about three or four feet long over the rebar
so it bends where you want it to bend yet you have a long lever arm.
The piece you bend it around obviously needs to be securely anchored.

Dan