Hi Stophel. Hope you are well. Mark the apex of the curve in the blade with a marker, pencil, or best guess. polish the apex area to bright metal maybe an inch and a half or so forward and aft of the apex. Put tang, or blade if need be, in vice and flex the blade enough to become straight to eye. Adjust in vice if needed. Heat the polished area of the spine with propane torch and when spine is hot, flex blade to a bit over flexed from dead straight. Do not let any heat colors run down to the edge or even much beyond half way in doing this. While still holding the blade over flexed and spine heated to blue or even neutral, pour water over it to completely cool. Repeat if necessary. The water will lock it in position, or close to, but it may take a few tries to get it where you want or will accept. Hammering on a heat treated blade will make that area brittle. It is breaking the grains and in doing so work hardening the steel which weakens it.