Patent ID: 7651318
Filing Date: 2010-01-26
Classification: C22C,F01D,F05D

Abstract:
1. A steam turbine, comprising: an inner steam pipe which is disposed through an inner casing and an outer casing and connected to a nozzle box; an outer steam pipe which is welded to the outer casing and disposed outside of the inner steam pipe along the inner steam pipe with a prescribed space between them; and a radiation heat shielding pipe which is disposed between the inner steam pipe and the outer steam pipe along the inner steam pipe to face a welded portion of at least the outer steam pipe, wherein cooling steam is flown between the inner steam pipe and the outer steam pipe, and high-temperature steam of 650° C. or more is introduced into the steam turbine; wherein the outer casing is formed of a cast steel which contains in percent by weight C: 0.05 to 0.15, Si: 0.3 or less, Mn: 0.1 to 1.5, Ni: 1.0 or less, Cr: 9 or more and less than 10, V: 0.1 to 0.3, Mo: 0.6 to 1.0, W: 1.5 to 2.0, Co: 1.0 to 4.0, Nb: 0.02 to 0.08, B: 0.001 to 0.008, N: 0.005 to 0.1, Ti: 0.001 to 0.03, and the balance of Fe and unavoidable impurities; wherein the inner casing, the inner steam pipe and the outer steam pipe are formed of at least one heat-resisting steel selected from wherein the radiation heat shielding pipe is formed of heat-resisting steel which contains in percent by weight C: 0.25 or less, Si: 1.5 or less, Mn: 2.0 or less, Ni: 19 to 22, Cr: 24 to 26, and the balance of Fe and unavoidable impurities, and the unavoidable impurities including P: 0.045 or less and S: 0.03 or less.