| 摘要 |
PROBLEM TO BE SOLVED: To provide a rotor shaft for a steam turbine excellent in strength in a specific range of temperature and time (>=600 deg.C and >=50,000 hours) and to provide a high pressure, medium pressure or high-medium pressure steam turbine and a steam turbine power plant using the same. SOLUTION: The rotor shaft for a steam turbine is composed of martensitic steel having a composition containing 0.05 to 0.20% C, <=0.2% Si, 0.05 to 1.5% Mn, <=0.2% Ni, 9.0 to 13.0% Cr, 0.05 to 0.5% Mo, 0.5 to 5.0% W, 0.05 to 0.30% V, 0.01 to 0.20% Nb, 1.0 to 2.0% Co, 0.01 to 0.1% N, 0.001 to 0.030% B and 0.0005 to 0.006% Al, and in which the (Ni/Co) ratio is <=0.1, and the high pressure, medium pressure or high-medium pressure steam turbine and steam turbine power plant use the same.
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