Patent ID: 6182439
Filing Date: 2001-02-06
Classification: C22C,F01D,F05D

Abstract:
A combined cycle power generation system in which a generator is driven by a steam turbine and a gas turbine, wherein said steam turbine comprises a rotor having a mono-block rotor shaft with blades mounted thereon in multi-stages from a high pressure side to a low pressure side and a casing covering said rotor, an inlet temperature of steam to first stage blades being not less than 530.degree. C., and wherein said rotor shaft is made of a Ni--Cr--Mo--V low alloy steel of bainitic structure having a higher creep rupture strength at the high pressure side than at the low pressure side or a higher toughness at the low pressure side than at the high pressure side, and a 538.degree. C. and 10.sup.5 h creep rupture strength of not less than 12 kg/mm.sup.2 at a central portion having mounted thereon first stage blades at the high pressure side or FATT of not more than 20.degree. C. at a central portion, mounting final stage blades at the low pressure side having a room temperature V-notch impact value of not less than 4 kg-m, and wherein blades of at least a final stage have a value of blade length in inches.times.revolution in rpm of not less than 125,000 and are made of martensite stainless steel including 8-13 wt % Cr.