Creep and rupture characteristics of high-temperature steels in cases of characteristic variable fatigue stress

With the help of the creep-resistant steels 15 Mo 3, 13 CrMo 4 4, 10 CrMo 9 10, 21 CrMoV 5 11, GS-17 CrMoV 5 11, 28 CrMoNiV 4 9, X 22 CrMoV 12 1 and X 6 CrNiMo 17 13, creep behaviour was studied under varying stress conditions. Emphasis was laid on investigations under single-stage, rectangular-cyclical stress or temperature change with low cycle numbers, covering cases of rupture within the range of 3 to 30. Complementary to this, a high-cycle subprogram was applied to attain about 1 000 cycles till rupture. The peak period as the ratio of the period under peak stress in the cycle to the cycle time was varied during the tests from 0.3 to 80%, while the stress crack under changed stress was varied from 25 to 100%, and at changed temperatures from 25 to 100 K. The low-cycle tests which had begun earlier continued, lasting for very long periods of about 35 000 hours; the newly started high-cycle tests, which were performed in testing machines specially developed for them, lasted for periods of up to about 10 hours. In addition, tests were made with low-cycle stress and temperature variation, with two-staged stress variation, and with acyclic stress. (orig./MM)