High strenght heat resisting cast steel, steam turbine casing, steam turbine power plant and steam turbine

摘要

A steam turbine has main components such as rotor shaft exposed to high temperature and intermediate pressure, which are made of a ferritic steel and the main steam temperature and the re-heat steam temperature are 610 DEG C to 660 DEG C, and a steam turbine power plant employs the turbine. Further, the rotating blades are made of only a martensitic steel or a combination of the martensitic steel and a Ni base alloy, the turbine rotor is made of a ferritic forged steel having a creep rupture strength at the operating temperature for 100 thousands hours of above 15 kg/mm<2>, and the casing is made of a ferritic cast steel having a creep rupture strength at the operating temperature for 100 thousands hours of above 10 kg/mm<2>. The ferritic cast steel of the casing contains, in weight percentages, C of 0.06 to 0.16 %, Si of not more than 1 %, Mn of not more than 1 %, Cr of 8 to 12 %, Ni of 0.1 to 1.0 %, V of 0.05 to 0.3 %, Nb of 0.01 to 0.15 %, N of 0.01 to 0.1 %, Mo of not more than 1.5 %, W of 1 to 3 %, B of 0.0005 to 0.003 %, O of not more than 0.015 % and the remainder of Fe and inevitable impurities. Its method of manufacturing features normalizing at 1000 to 1100 DEG C, rapid cooling and tempering twice at 550 to 750 DEG C and at 670 to 770 DEG C.