Study of crack growth under operational conditions in steam turbine steel: phase I report. Technical report 9

Fatigue crack growth and plane strain fracture toughness have been examined in three 1 Cr--Mo--V bainitic steam generator rotor steels. The effects of inclusion content, manufacturing processes, and repeated aging on the rate of subcritical crack growth at room temperature have been investigated using compact tension specimens. The impact properties of these steels above the temperature range of -62 - +100/sup 0/C have also been determined using both standard and precracked Charpy specimens. In addition the tensile properties above the temperature range of 0/sup 0/ to 538/sup 0/C have been evaluated using cylindrical tensile specimens. Variation in inclusion content, microstructure, yield and tensile strengths, and ductile to brittle transition temperature had no effect on the crack growth rate of 1 Cr--Mo--V rotor steels; brittle cleavage modes of fatigue were not observed in either continuous or intermittently strain aged specimens tested at ambient temperature. However, unstable cleavage crack extension can be initiated during cold starts if a sufficiently long crack is present.