Abstract
Mechanical properties of steam turbine casing and rotor materials serviced for 13 years were investigated. The results obtained are summarized as follows.
(1) The creep rupture strength of the materials used in steam at 538°C showed a little decrease.
(2) The value of KIc of the rotor material used at 480°C was 65% of that of the same material used at 70°C.
(3) Embrittlement during service occurred at 400∼522°C, but not below 300°C. It is considered that the main factor of embrittlement is the segregation of impurities such as phosphor to the grain boundary.
(4) The FATT of embrittled materials was recovered by the de-embrittle treatment at 650°C.
