Patent ID: 7794208

Claim:
A steam turbine rotor having rotor hooks and rotor necks which have an attachment structure with respect to an inverted fir-tree blade root having blade hooks and blade necks, wherein a rotor material has lower tensile strength than a blade material, and a rotor radial-direction hook length (Hri) of said rotor hook from an interface between a rotor hook contact surface contacting with said blade hook and an inscribed circular surface of said rotor neck is larger than a blade radial-direction hook length (Hbi) of said blade hook from an interface between a blade hook contact surface contacting with said rotor hook contact surface and an inscribed circular surface of said blade neck, and a rotor circumferential-direction neck width (Wri) of said rotor neck at a predetermined position counting from the outermost circumference of the rotor is larger than a blade circumferential-direction neck width (Wbi) of said blade neck at a corresponding position of the same number as said rotor neck counting from the innermost circumference of the blade.