Creep-Fatigue Strength of SUS304 Welded Joints at 550°C and the Evaluation on the Basis of Strain Concentration

Abstract

Strain controlled fatigue and creep-fatigue tests at 550°C were carried out on two kinds of SUS304 welded joints. The results obtained are summarized as follows;
(1) Fatigue strength reduction factor of welded joints, in the case without strain holding, shows a maximum value at the strain range of 0.3%, and decreases rapidly with a decrease in strain range.
(2) Creep-fatigue strength of welded joints, in the case of strain range of more than 0.5%, can be reasonably evaluated by strain concentration in a weld metal region, which is strongly affected by thermal softening and/or dynamic strain aging behaviors of weld metal and base metal.
(3) Creep-fatigue strength of welded joints in a low strain range region is considerably affected by creep damage, which increases due to elastic follow-up during strain holding period.