PURPOSE: To prevent deterioration of corrosion resistance due to local cold working, by applying a suitable cold working previously to the titled steel sheet, forming a member then aging and recrystallization heat treating it, at forming the member by cold working said steel sheet locally.

CONSTITUTION: In the title steel sheet requiring corrosion resistance used after opening a hole by punching at room temp. as member for steam strainer of e.g. geothermal energy turbine, steel plate is cold rolled prior to said punching. The rolling is carried out so that Cr carbides are pptd. uniformly at aging heat treatment after punching, and effective draft is about 30%. Next, the steel sheet is punched by press, then heated at about 675°C for about 15hr as aging heat treatment effective to both of circumferential part of the hole subjected to strong punching and the as rolled part, to ppt. Cr carbides uniformly. Successively, the plate is heated at about 775°C for about 5hr as recrystallization heat treatment, to remove internal strain due to working without dissolving Cr carbides in solid solution.