Abstract: In the case of a method for the heat treatment of erected, preferably large-area tube wall regions or tube wall segments, in particular of a diaphragm wall, of a steam generator, in particular of a power plant, in the installed state, it is sought to provide a solution which permits the use of steel types which are more problematic with regard to power plant operation with elevated steam parameters, in particular the steels T23 and T24, in the erection of steam generators. This is achieved in that the tube wall regions or tube wall segments for heat treatment are subjected, in the installed state in the steam generator, and in particular over a large area, to a stress-relief annealing process.