Correcting distortion in aluminium casting after welding

[Flowboy]

Hi. I have an old (70 years) aluminium casting about 12"" diameter, that has been repaired but has distorted about 1mm out of true on a flat machined face.
Has anyone experience of getting this back to true again & how? Other than machining the face as a last resort.
I'm thinking heat from a gas torch or some other heat related way at present.

 

[minimutly]

Heating and pulling with a well designed fixture is worth a thought - but you'll need a big torch?

 

[anto44]

Sometimes a well placed weld can be used to distort back in the other direction, if that makes sense. A few pics of the part would help