種々の熱処理を行なった2 1/4% Cr-1% Mo鋼のクリープ破断強度と電子顕微鏡による組織

抄録

The relation between creep rupture strength and the electron microstructures of 2 1/4% Cr-1% Mo steel in heat-treatment conditions were investigated. The results are summarized as follows:
(1) Curves of creep stress-time are linear or almost linear in stabilized and semistabilized structures and that of unstabilized structure shows knick point in curve at 600°C, 1000hrs.
(2) There is no change in the microstructure of stabilized specimens during the creep test at 600°C, but that of unstabilized specimens changes to match the gradient of stress-rupture curves.
(3) The interactions between one dislocation and another or between dislocation and the precipitates are important factors of creep rupture strength.
(4) The activation energy of creep calculated by Zener-Hollomon parameter, agrees well with that of diffusion of Cr atom when the structure is stabilized by long time annealing.
(5) The recovery and recrystallization are observed at creep deformed zones preferentially.
(6) From the facts (4) and (5), the creep deformation is supposed to be accelerated by recovery and recrystallization which are processed by dislocation movement accompanied with diffusion of Cr atom.
(7) The long time rupture strength of the test specimen will be easily and accurately estimated by annealing it for a long time and so stabilizing its structure. The plot calculated by Dorn parameter with the experimental values of the stabilized specimen agrees with Dorn master curve.