JP4703901B2 - How to make erosion prevention coating - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of forming a coating for preventing erosion on the surface of a turbine rotor blade on the steam inlet side or the surface of a steam inlet of a main steam control valve of a steam turbine. The present invention relates to a novel improvement for facilitating ensuring quality such as adhesion without lowering the fatigue limit of the moving blade portion.
[0002]
[Prior art]
FIG. 5 is a configuration diagram schematically showing a moving blade of a conventional steam turbine.
FIG. 6 is a configuration diagram illustrating an enlarged main part of a moving blade of a conventional steam turbine.
FIG. 7 is a cross-sectional view schematically showing a CC cross section in FIG. 6.
As shown in FIG. 5, a plurality of moving blades 1 </ b> A to 1 </ b> G are implanted around the turbine rotor 2, and steam g indicated by an arrow passes through the main steam control valve 3 to the plurality of moving blades 1 </ b> A to 1 </ b> G. The turbine rotor 2 is rotated by being applied, and this rotational power is used for the operation of a generator, a compressor, and the like.
[0003]
As shown in FIGS. 6 and 7, the steam g flows as indicated by an arrow, thereby rotating the turbine rotor 2 via the moving blade 1.
As described above, the high-temperature / high-pressure steam g introduced through the main steam control valve 3 flows into the low-pressure stage-side moving blades 1E-1G through the high-pressure stage-side moving blades 1A-1D. At this time, the low-pressure stage side becomes a low-temperature / low-pressure steam g ′ in which erosion easily occurs.
Therefore, conventionally, a method of preventing erosion by sticking a stellite plate 1b with silver brazing to the surface 1a on the steam inlet side of the low-pressure stage blades 1E to 1G has been generally performed.
[0004]
[Problems to be solved by the invention]
Since the conventional apparatus is configured as described above, the following problems exist. In other words, since silver brazing is performed at a high temperature, the fatigue limit of the rotor blade base material (stainless steel) is greatly reduced (1/2 to 1/3), resulting in design restrictions, Since the profile shapes of the moving blades 1A to 1G are complicated, there is a problem that it is difficult to ensure quality such as adhesion of the stellite plate in the moving blades 1E to 1G on the low pressure side.
[0005]
The present invention has been made to solve the above-described problems, and in particular, by forming a stellite film at a low temperature in a temperature range in which the fatigue limit of the rotor blade base material is not significantly reduced, It is an object of the present invention to provide a method for producing an erosion-preventing coating for facilitating ensuring quality such as adhesion without lowering the fatigue limit.
[0006]
The method for producing an erosion-preventing film of the present invention comprises a step of forming a notch on the steam inlet side surface of a rotor blade of a turbine rotor, a step of spraying a stellite material on the notch, and a step of annealing. A method for producing an erosion-preventing film for forming a stellite film on a surface of a moving blade on a steam inlet side, wherein the thermal spraying process uses a low current of 20 A or less and prevents excessive heat input during thermal spraying. Transferred Arc) method is a step of filling the notch with stellite material with said annealing step is a construction is a step of annealing 1 hour the blades at 550 to 650 ⁰ C. Further, the method for creating an erosion prevention film according to another embodiment of the present invention includes a step of forming a notch on the surface of the steam inlet of the main steam control valve of the steam turbine, and a step of spraying a stellite material on the notch. and a step of annealing a, to a method of making an erosion prevention film for forming a stellite film on the surface of the steam inlet portion of the main steam control valve, wherein the spray process uses the following low current 20A, during spraying Is a step of filling the notch with a stellite material using a PTA (Plasma Transferred Arc) method for preventing excessive heat input , and the annealing step is a step of annealing the main steam control valve at 550 to 650 ⁰ C for 1 hour. It is the composition which is.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a method for producing an erosion-preventing film according to the present invention will be described in detail with reference to the drawings.
In addition, the same code | symbol is attached | subjected to the same or equivalent part as a conventional apparatus, and the description is abbreviate | omitted.
[0008]
Embodiment 1 FIG.
FIG. 1 is a configuration diagram schematically showing a main part of a moving blade 1 machined by the method for producing an erosion-preventing film of the present invention.
In the method for producing an erosion-preventing film of the present invention, as shown in the figure, a stellite film is formed as a erosion-preventing film by spraying a stellite material on the surface 1a on the steam inlet side of the low-pressure stage rotor blades 1E to 1G. Is. The thermal spraying is performed by a method such as PTA (Plasma Transferred Arc).
The formation of the stellite coating 1d by such thermal spraying is performed mainly for the low pressure stage where erosion is likely to occur, for example, the moving blades 1E, 1F, and 1G shown in FIG.
[0009]
FIG. 2 is a conceptual diagram showing step-by-step the stellite film forming process by the erosion-preventing film forming method of the present invention.
First, as shown in FIG. 2A, a notch 1c having a predetermined depth is formed on the surface 1a on the steam inlet side of the target low-pressure stage blades 1E to 1G. Next, as shown in FIG. 2 (b), a stellite material is sprayed from the thermal spray nozzle 4 to the notch 1c, but the fatigue limit of the rotor blade base material is not significantly reduced (as in the conventional case 1 / PTA method using a low current of 20 A or less is used for this thermal spraying so that the thermal spraying is performed in a temperature range in which the temperature does not drop significantly as 2 to 1/3. Further, if the rotor blade is annealed at a temperature of 550 to 650 ⁰ C for about 1 hour, air-cooled and then the surface of the portion sprayed with the stellite material is polished and finished, the stellite film 1d is completed.
[0010]
As described above, according to the method for creating an erosion-preventing film of the present invention, a stellite material is sprayed on the surface 1a on the steam inlet side of the low-pressure stage moving blades 1E to 1G where erosion is likely to occur using a low current. Then, since the stellite film 1d is formed by annealing, the stellite plate 1b is not affected by heat at a high temperature by silver brazing as in the prior art, and the hardness of the rotor blade base material can be ensured to be normal. The fatigue limit is less likely to occur. Further, deformation due to thermal spraying hardly occurs and there is no fear of stress corrosion cracking. Compared to the case where the stellite plate 1b is pasted as in the prior art, there is an advantageous effect such as low cost, and the stellite film 1d as a high-quality and economical erosion-preventing film can be produced.
[0011]
In the turbine rotor 2 shown in FIG. 1, for convenience of explanation, the rotor blades 1 </ b> A to 1 </ b> D are described as high-pressure stages and the rotor blades 1 </ b> E to 1 </ b> G are separately described as low-pressure stages. The range of the stages is different, and here, only the case where the stellite film is formed on the low-pressure stage of the plurality of moving blades 1A to 1G is described. Therefore, if necessary, all the moving blades 1A to 1G may be provided with a stellite film by the production method of the present invention.
[0012]
In addition, although the case where the thermal spraying process is performed using the PTA method has been described here, the thermal spraying process is performed to such an extent that the fatigue limit of the rotor blade base material is not significantly reduced (1/2 to 1/3 as in the prior art). Other methods may be used as long as the method is performed in a temperature range that does not significantly decrease the temperature of the moving blade base material so that it is not affected by heat.
[0013]
Embodiment 2. FIG.
The method for creating an erosion-preventing film according to Embodiment 2 of the present invention is to create a stellite film 3d on the surface 3c of the steam inlet portion of the main steam control valve 3 of the steam turbine.
FIG. 3 is a side view schematically showing a configuration of a steam inlet portion of a main steam control valve that forms a stellite film by the method for creating an erosion-preventing film according to Embodiment 2 of the present invention.
4 is a cross-sectional view schematically showing a BB cross section of the steam inlet portion of the main steam control valve shown in FIG. 3.
[0014]
As shown in FIGS. 3 and 4, the surface 3c around the steam inlet of the valve seat 3b with which the valve body 3a of the main steam control valve 3 (see FIG. 5) engages is stellite as in the first embodiment. After the material is sprayed at a low current of 20 A, the periphery of the sprayed portion is annealed at a temperature of 550 to 650 ⁰ C for about 1 hour, air cooled, and then finish-polished to complete the stellite film 3d.
[0015]
Thus, if the method for producing an erosion-preventing film of the present invention is used, the fatigue limit of the valve seat base material is not significantly reduced (as in the conventional case, it is greatly reduced to 1/2 to 1/3). In other words, the stellite film 3d having a high erosion prevention effect can be formed at a low cost on the surface 3c around the steam inlet of the valve seat 3b with which the valve body 3a of the main steam control valve 3 of the steam turbine is engaged.
[0016]
【The invention's effect】
According to the method for producing an erosion-preventing film of the present invention, the thermal spraying process is a process performed in a temperature range where the fatigue limit of the rotor blade base material is not significantly reduced, and the annealing process is performed at 550 to 650 ⁰ C. Because it is a process of annealing for about 1 hour, it is not affected by heat at high temperatures due to silver brazing as in the past, and the hardness of the rotor blade base metal can ensure the normal hardness, and the fatigue limit is unlikely to decrease. Thus, deformation due to thermal spraying hardly occurs, and a low-cost erosion-preventing film that does not cause stress corrosion cracking can be produced.
Further, according to the method for creating an erosion-preventing film according to another embodiment of the present invention, the thermal spraying process is a process performed in a temperature range in which the fatigue limit of the valve seat base material is not significantly reduced, and the annealing process is the main steam. Since the adjusting valve is a step of annealing at 550 to 650 ⁰ C for about 1 hour, the valve seat with which the valve body of the main steam control valve of the steam turbine is engaged without significantly reducing the fatigue limit of the valve seat base material. A stellite film having a high erosion-preventing effect can be produced at a low cost on the surface around the steam inlet.
[Brief description of the drawings]
FIG. 1 is a configuration diagram schematically showing a main part of a moving blade 1 machined by a method for producing an erosion prevention film of the present invention.
FIG. 2 is a conceptual diagram showing step by step a stellite film creation process by the erosion prevention film creation method of the present invention.
FIG. 3 is a side view schematically showing a configuration of a steam inlet portion of a main steam control valve for forming a stellite film by a method for creating an erosion prevention film according to Embodiment 2 of the present invention.
4 is a cross-sectional view schematically showing a BB cross section of a steam inlet portion of the main steam control valve shown in FIG. 3;
FIG. 5 is a configuration diagram schematically showing a moving blade of a conventional steam turbine.
FIG. 6 is an enlarged configuration diagram showing a main part of a moving blade of a conventional steam turbine.
7 is a cross-sectional view schematically showing a CC cross section in FIG. 6;
[Explanation of symbols]
1A to 1G Rotor blade 1a Steam inlet side surface 1c Notch 1d Stellite coating 2 Turbine rotor 3 Main steam control valve 3a Valve body 3b Valve seat 3c Surface around steam inlet 3d Stellite coating 4 Thermal spray nozzles g, g 'steam

Claims (2)

A step of forming a notch portion on the steam inlet side surface of the rotor blade of the turbine rotor, a step of spraying a stellite material on the notch portion and a step of annealing, and a step of forming a stellite on the surface of the rotor blade on the steam inlet side. A method for creating an erosion-preventing film that forms a film,
The thermal spraying step is a step of filling the notch with a stellite material using a PTA (Plasma Transferred Arc) method using a low current of 20 A or less and preventing excessive heat input during thermal spraying ,
The method for producing an erosion-preventing film, wherein the annealing step is a step of annealing the blade at 550 to 650 ⁰ C for 1 hour. A step of forming a notch on the surface of the steam inlet of the main steam control valve of the steam turbine, a step of spraying a stellite material to the notch, and a step of annealing, comprising the step of forming the steam inlet of the main steam control valve A method of creating an erosion-preventing film that forms a stellite film on the surface,
The thermal spraying step is a step of filling the notch with a stellite material using a PTA (Plasma Transferred Arc) method using a low current of 20 A or less and preventing excessive heat input during thermal spraying ,
The method for producing an erosion-preventing film, wherein the annealing step is a step of annealing the main steam control valve at 550 to 650 ⁰ C for 1 hour.

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