Nachbehandlung von Halbzeugen und Apparaten aus austenitischen Stählen zur Vermeidung von Spannungsrißkorrosion

After‐treatment of semifinished products and equipment made of austenitic steel to avoid stress corrosion . Among the factors initiating stress corrosion, the extent and distribution of internal tensile stress are the least tractable. Unknown internal stresses are always superposed on the estimable operational stresses. If they arise from distortions or welding, the former are distributed throughout the entire cross‐section. The action of tools, e.g. on turning or grinding, can also lead to high internal tensile stresses in a thin surface zone. Such stresses are of particular significance because stress corrosion is initiated on the surface. In this article, it is shown that it is usually sufficient to adequately reduce these surface‐proximate internal tensile stresses, e.g. by a pickling process removing a surface layer of material, in order to eliminate stress corrosion and thus to extend the scope of austenitic steels. Should the internal tensile stresses due to distortion and welding suffice to initiate stress corrosion under particularly aggressive conditions, one can attempt to reduce the stress by suitable heat treatment; however, no impermissable change in the microstructure of the steel may occur. Finally, it is also possible to produce compressive stress in a thin surface zone by shot peening so that no stress corrosion can take place. The advantages and disadvantages of the various possibilities are illustrated with the aid of examples.