Patent ID: 7850423

Claim:
A steam turbine having a turbine rotor to which high-temperature steam at 620° C. or higher is introduced, comprising: a high-temperature turbine rotor constituent part positioned in an area extending from a nozzle on a first stage to a moving blade on a stage where temperature of the steam becomes 550° C., the high-temperature turbine rotor constituent part being made of a corrosion and heat resistant material; low-temperature turbine rotor constituent parts connected to and sandwiching the high-temperature turbine rotor constituent part, the low-temperature turbine rotor constituent part being made of a material different from the material of the high-temperature turbine rotor constituent part; a joint portion positioned on an upstream side out of joint portions on an outer surface between the high-temperature turbine rotor constituent part and the low-temperature turbine rotor constituent part, the joint portion positioned on the upstream side being formed at a position corresponding to the nozzle on the first stage; a joint portion positioned on a downstream side out of joint portions on an outer surface between the high-temperature turbine rotor constituent part and the low-temperature turbine rotor constituent part, the joint portion positioned on the downstream side being formed at a position on a downstream side of a nozzle positioned on an immediate downstream side of a moving blade on a stage where temperature of the steam becomes 550° C.; and a cooling part configured to cool the joint portion on the downstream side out of the joint portions, the cooling part supplying a cooling steam to the upstream side of the nozzle positioned on the immediate downstream side of the moving blade on the stage where the steam temperature becomes 550° C.