In this paper,master curve of plane strain fracture toughness,
KIc,for used turbine rotors subjected to temper embrittlement is studied by rearranging a total of 64 data. Fracture appearance transition temperature,
FATT,of 2mm V-notch Charpy impact test of the target material was 99 to 181°C,and the thickness,
B,of the fracture toughness test specimens used was 200,100,50 and 25mm. When the test temperature,
T,is arranged by excess temperature,
Te,(=
T-
FATT),
KIc data have small variation regardless of the
FATT value and the intermediate
KIc value is represented by the same formula as the master curve of ASTM E1921. The relationship between
Kc,1T data,which are fracture toughness for 1CT specimens (
B=25mm) converted from each
KIc data of
B=200,100,50 and 25mm according to ASTM E1921,and
Te was also obtained. The variation of
Kc,1T data is larger than that of
KIc data. The nine pieces of
Kc,1T data converted from ten
KIc data of
B=200 and 100mm are located around the upper limit of the variation,and 6 pieces of them exceeded the 95% confidence limit obtained according to ASTM E1921. The reason for the small variation in
KIc data of the used turbine rotors was also discussed.
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