Patent ID: 7484926

Claim:
A steam turbine power plant which is provided with an extra-high-pressure turbine, a high-pressure turbine, an intermediate-pressure turbine and a low-pressure turbine, and has high-temperature steam of 650° C. or more introduced into the extra-high-pressure turbine; wherein the extra-high-pressure turbine comprises: a double-structured casing which is comprised of an outer casing and an inner casing; and an outer casing cooling unit which cools the outer casing by introducing cooling steam between the outer casing and the inner casing; a turbine rotor of the extra-high-pressure turbine is formed of a heat-resisting alloy which contains in percent by weight C: 0.10-0.20, Si: 0.01-0.5, Mn: 0.01-0.5, Cr: 20-23, Co: 10-15, Mo: 8-10, Al: 0.01-1.5, Ti: 0.01-0.6, B: 0.001-0.006 and the balance of Ni and unavoidable impurities, and it is suppressed in the unavoidable impurities that Fe is 5 or less, P is 0.015 or less, S is 0.015 or less and Cu is 0.5 or less; the inner casing and a nozzle box of the extra-high-pressure turbine are formed of a heat-resisting alloy which contains in percent by weight C: 0.03-0.25, Si: 0.01-1.0, Mn: 0.01-1.0, Cr: 20-23, Mo: 8-10, Nb: 1.15-3.0, and the balance of Ni and unavoidable impurities, and it is suppressed in the unavoidable impurities that Fe is 5 or less, P is 0.015 or less, S is 0.015 or less, and Cu is 0.5 or less; and the outer casing of the extra-high-pressure turbine is formed of a cast steel which contains in percent by weight C: 0.05-0.15, Si: 0.3 or less, Mn: 0.1-1.5, Ni: 1.0 or less, Cr: 9 or more and less than 10, V: 0.1-0.3, Mo: 0.6-1.0, W: 1.5-2.0, Co: 1.0-4.0, Nb: 0.02-0.08, B: 0.001-0.008, N: 0.005-0.1, Ti: 0.001-0.03 and the balance of Fe and unavoidable impurities.