Steam turbine facility

1. A steam turbine facility in which steam having temperature of 650° C. or higher is used, the steam turbine facility comprising:

a first member and a second member whose base material is formed of cast material composed of at least one of Ni-based alloy, austenite steel, or high-chrome steel, the first member and the second member forming a space where the steam flows;

a metal gasket provided between the first member and the second member, the metal gasket having a plurality of portions in line contact with the first member and the second member; and

a first high-hardness layer which is harder than the base material, the first high-hardness layer being provided on the first member and the second member at least in a portion where each of the first member and the second member is in line contact with the metal gasket.

2. The steam turbine facility according to claim 1 ,

wherein on an outer circumferential side of the metal gasket, an annular projection formed in the first member is fitted to an annular depression formed in the second member,

wherein the metal gasket is held between a projection seal surface formed on the annular projection and a depression seal surface formed on the annular depression to be in line contact with each of the projection seal surface and the depression seal surface,

wherein an outer circumference of the metal gasket is in line contact with a wall surface of the second member which forms an outer circumferential edge of the annular depression, and

wherein the first high-hardness layer is provided on the projection seal surface, the depression seal surface and the wall surface.

3. The steam turbine facility according to claim 2 ,

wherein the metal gasket has a slit in cross-section, and

wherein the metal gasket is arranged so that the slit faces toward the space and a portion other than the slit is in line contact with the projection seal surface, the depression seal surface and the wall surface.

4. The steam turbine facility according to claim 2 ,

wherein the first member contacts the second member in an annular area which is on an outer circumferential side of a fitting position where the annular projection is fitted to the annular depression, the first member being fastened to the second member in a fastening area which is on an outer circumferential side of the annular area, and

wherein the steam turbine facility further comprises:

a second high-hardness layer which is harder than the base material, the second high-hardness layer being provided in a portion where the first member contacts the second member in the annular area.

5. The steam turbine facility according to claim 1 ,

wherein the first high-hardness layer is formed of Co-based alloy.

6. The steam turbine facility according to claim 1 ,

wherein one of the first member or the second member is a valve casing of a steam valve, and

wherein the other of the first member or the second member is a bonnet of the steam valve which is attached to the valve casing.

7. The steam turbine facility according to claim 1 ,

wherein the first member and the second member form flange connection parts of a pair of pipes in which the steam flows.

8. The steam turbine facility according to claim 1 ,

wherein one of the first member or the second member is an upper half of a turbine casing, and

wherein the other of the first member or the second member is a lower half of the turbine casing.