Mitsubishi Hitachi Power Systems, Ltd. (MHPS) has carried out the development of the
700°C class A-USC steam turbine through the auspices of a Japanese national project since 2008.
We have developed a mainly Ni-based material with a high-temperature creep strength exceeding
100 MPa at 700°C for 100,000 hours with the successful production of a large-scale forged rotor
weighing more than 10 tons, as well as fabrication technology for a dissimilar-material welded
rotor using the Ni-based material and high Cr steel. We then conducted a full-scale, long-term
rotational turbine test to verify these development technologies under test conditions where the
steam turbine with a dissimilar-material welded rotor was utilized at a temperature higher than
700°C at 3600 rpm. This paper describes these development technologies.
