Patent ID: 7459035

Claim:
A rotor of a steam turbine of which main steam temperature is 675° C. or more, wherein the rotor weighs 8 ton or more and is made from a forged material of NiFe-base alloy consisting of: Cr of 14 to 18 weight %; Fe of 15 to 45 weight %; Al of 1.0 to 2.0 weight %; Ti of 1.0 to 1.8 weight %; C and N of which the sum is 0.05 or less weight %; Nb within the range defined by the formula; 3.5−(Fe weight %)/20<(Nb weight)<4.5−(Fe weight %)/20; and the balance essentially Ni; wherein a γ′ phase is precipitated in the NiFe-base alloy, the γ′ phase being Ni 3 A1; and wherein the NiFe-base alloy does not contain γ″ phase.