Patent ID: 6123504
Filing Date: 2000-09-26
Classification: B23K,C21D,F01D

Abstract:
A steam turbine comprisinga rotor shaft;movable blades assembled on the rotor shaft;fixed blades for guiding inflow of steam to the moving blades; andan inner casing for holding the fixed blades,said rotor shaft and at least a first stage of said movable blades being made of high-strength martensitic steel comprising 0.05-0,20% of C, at most 0.15% of Si, 0.3-0.7% of Mn, 9.5-13% of Cr, 0.3-0.7% of Ni, 0.05-0.35% of V, 0.02-0.15% of Nb, 0.01-0.06% of N, 0.050.5% of Mo, 1.0-3.5% of W, 2-10% of Co and 0.0005-0.03% of B, and at least 78% of Fe, the percentages being given in terms of weight,said inner casing being made of martensitic cast steel comprising 0.06-0.16% of C, at most 0.5% of Si, at most 1% of Mn, 0.2-1.0% of Ni, 8-12% of Cr, 0.05-0.35% of V, 0.01-0.15% of Nb, 0.01-0.1% of N, at most 1.5% of Mo, 1-4% of W and 0.0005-0.03% of B, and at least 85% of Fe, the percentages being given in terms of weight,said rotor shaft having a length of at least 5 m and a minimum diameter of at least 600 mm at a portion where said fixed blades are assembled, andsaid first stage of said moving blades having a length of at least 35 mm at a blade portion thereof.