JPH08300228A - Electric discharge machining method for system turbine stationary blade - Google Patents

Abstract

PURPOSE: To improve workability in electric discharge machining method for machining the stationary blade of a partitioning plate. CONSTITUTION: A stationary blade 23 is formed by electric discharge machining from the lower surface side of a partitioning plate disk 21 positioned with the fluid outlet side of the stationary blade as an upper surface, an edge and a different level on the stationary blade outlet side formed by electric discharge machining is finished, and then the detriorated layer on a machining surface made electric discharge machining is removed by an acid bath.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining method for a steam turbine vane of a partition plate used in a steam turbine.

[0002]

2. Description of the Related Art FIG. 3 schematically shows a conventional method for processing a partition plate of a general steam turbine.

Conventionally, a steam turbine partition plate has a pair of half-cracked outer and inner rings 51 and 52 as shown in FIG. 3A, and a large number of stationary blades 53 as shown in FIG. 3B. After cutting, as shown in FIG. 3C, assembly welding is performed with a large number of vanes 53 positioned between the outer ring 51 and the inner ring 52. Then, the half-split mating surfaces 54 of both of them are subjected to finish processing to manufacture a partition plate 50 as shown in FIG. 3 (d).

However, in such a method of processing the partition plate 50, there are many processing steps such as the number of parts of the partition plate 50 and assembly welding, which requires a long processing schedule and a large manufacturing cost. There is a problem of becoming. Therefore, in recent years, it has been considered to form the partition plate by die-sinking electric discharge machining.

FIG. 4 is a schematic diagram showing a conventional method of machining a partition plate of a steam turbine, and FIG. 5 is a schematic diagram showing a conventional method of machining a stationary blade of a steam turbine by electric discharge machining.

That is, as shown in FIG. 4 (a), a disk 61 cut into a perforated disc is discharged so that the fluid inlet side of the vane is the upper surface as shown in FIG. 4 (b). This stationary blade 63 is formed by machining, and the altered layer on the die-sinking electric discharge machined surface of this stationary blade 63 is removed and polished by a pencil grinder. Then, as shown in FIG. 4C, the partition plate 60 is cut into half cracks by wire electric discharge machining, and as shown in FIG.
Produce 0.

In this electric discharge machining of the stationary blade, as shown in FIG.
As shown in FIG. 4, the disk 61 is set in the discharge oil (not shown) with the fluid inlet side of the vane as the upper surface, and first, the large rough machining electrode 11 is fed to the disk 61 from the upper surface while being straightened or swung. Large rough machining is performed by discharging through discharge oil. Next, as shown in FIG. 5B, the medium rough machining is performed by rotating and feeding the medium rough machining electrode 12 from the upper surface side of the disk 61. Finally, as shown in FIG. 5C, the finishing electrode 13 is swung and fed from the upper surface side of the disk 61 for finishing. Then, as shown in FIG. 5 (d), the disk 61 is inverted in the discharge oil so that the fluid outlet side of the vane is the upper surface, and the fluid outlet side is rounded.
Then, the upper blade side is horizontally moved to round the exit edge of the vane 63. Finally, as shown in FIG. 5E, the outlet pressing electrode 15 is lowered on the upper surface side of the disk 61 to smooth the outlet step of the stationary blade 63, thereby forming the stationary blade 63 by die-sinking electric discharge machining. To complete.

[0008]

As described above, in the above-described conventional method for machining the stationary blade of the steam turbine by electric discharge machining, the stationary blade of the partition plate is formed by electric discharge machining, so that the parts of the partition plate are formed. Although it is possible to reduce the processing schedule and the manufacturing cost by reducing the number of points and reducing the number of processing steps such as assembly welding, there are the following problems.

That is, in the conventional electric discharge machining method for the vane of the steam turbine, since the die-sinking electric discharge machining for forming the vane is performed from the upper surface side of the partition plate 61, the curved concave bottom surface is formed during the machining. Sludge accumulates, and this sludge interferes with electrical discharge machining, resulting in a longer machining time. Further, during the die-sinking electric discharge machining process of the stationary blade, it is necessary to perform a setup change operation for inverting the partition plate disk 61 in the electric discharge oil, which makes the operation troublesome. Furthermore, the die-cutting electric discharge machining of the stationary blade creates an altered layer on the machined surface and causes hair cracks. However, this altered layer has high hardness and is difficult to be fluid-polished. It is necessary to remove the deteriorated layer and grind it with a grinder, and the workability is not good. As a result, the machining work of the stationary blades of the steam turbine requires a long machining schedule and the manufacturing cost becomes large.

The present invention is intended to solve such a problem, and an object of the present invention is to provide a method of electric discharge machining of a steam turbine stationary blade, which improves workability.

[0011]

The electric discharge machining method for a steam turbine stationary blade according to the present invention for achieving the above-mentioned object is to machine a stationary blade of a partition plate interposed between a plurality of stages of steam turbine moving blades. In the electric discharge machining method, the stator vane is formed by electrical discharge machining from the lower surface side of the partition plate disk positioned with the fluid outlet side of the vane surface as the upper surface, and the stationary blade is formed by electric discharge machining from the upper surface side. Further, the edge and the step on the outlet side of the stationary blade are subjected to finish machining, and then the deteriorated layer on the machined surface subjected to the electric discharge machining is removed by pickling.

[0012]

When the partition plate of the steam turbine is machined by the electric discharge machining method of the steam turbine vane of the present invention, first, the machined partition plate disk is positioned in the discharge oil so that the fluid outlet side of the vane is the upper surface. Then, the electrodes are discharged from the lower surface side through discharge oil to perform large rough machining, medium rough machining, and finishing machining. Next, the outlet rounding electrode and the pressing electrode are used to discharge the discharge oil from the upper surface side of the partition plate disk,
The outlet side edge of the vane is rounded to smooth the outlet step, and the molding by this discharge is completed. Then, the deteriorated layer formed by electric discharge machining of the stationary blade of the partition plate is removed by pickling, and a fluid abrasive is flown between the stationary blades from which the deteriorated layer has been removed to perform fluid polishing.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic cross section showing a machining procedure for carrying out an electric discharge machining method for a steam turbine stationary blade according to an embodiment of the present invention, and FIG. 2 shows pickling of a stationary blade of a steam turbine partition plate. An outline is shown.

In the electric discharge machining method for the steam turbine vane of this embodiment, the machining procedure will be described. First, as shown in FIG. 1 (a), a disk 21 cut into a disk shape is positioned and set in discharge oil (not shown) so that the fluid outlet side of the vane is the upper surface, and the rough machining electrode 11 is arranged from the lower surface side. Is performed while straightening or turning and is discharged through discharge oil to perform large rough machining. Next, as shown in FIG.
Then, the medium rough machining electrode 12 is swung and fed from the lower surface to perform the medium rough machining. Finally, as shown in FIG. 1 (c), the finishing electrode 13 is swung from the lower surface of the disk 21 while being swung to perform the finishing process.

Then, as shown in FIG. 1D, the outlet rounding electrode 14 is horizontally moved on the upper surface of the disk 21 to round the outlet side edge of the stationary blade 23. Finally, as shown in FIG. 1 (e), the outlet pressing electrode 15 is lowered on the upper surface of the disk 21 to eliminate the step on the outlet side of the stationary blade 23 and smooth it.
Completing the molding of the disk 21 by this die-sinking electric discharge machining,
The partition plate 20 is manufactured.

As shown in FIG. 2, the partition plate 20 manufactured in this manner is used as a pickling solution 32 using dilute hydrochloric acid in the pickling layer 31.
And the stirrer blade 33 provided in the pickling layer 31 is rotated by a stirrer (electric motor) to stir the pickling solution 32 by the rotation of the stirrer blade 33, and the die-sinking discharge of the stationary blade 23. The deteriorated layer and the hair crack on the processed surface are removed by this pickling. Then, a fluid abrasive is flown into the vapor passage 24 between the stationary blades 23 of the partition plate 20 from which the altered layer has been removed to perform fluid polishing. Then, finally, the partition plate 20 is cut into half cracks in electric discharge oil by wire electric discharge machining, and the half-cracked mating surface is finished, and the processing of the partition plate 20 is completed.

[0017]

As described above with reference to the embodiments, according to the electric discharge machining method for a steam turbine stationary blade of the present invention, from the lower surface side of the partition plate disk positioned with the fluid outlet side of the stationary blade as the upper surface. A vane is formed by electrical discharge machining, and the edges and steps on the outlet side of the vane formed by electrical discharge machining are finished from the upper surface of this partition plate disk, and then the deteriorated layer on the electrical discharge machined surface is pickled. Since sludge does not drop downward during machining and does not interfere with electrical discharge machining, the work can be performed smoothly and the partition in the electrical discharge oil is being processed during machining of the stationary blade. There is no need to invert the plate disk, and this setup change operation can be omitted, and the deteriorated layer on the electric discharge machined surface of the stationary blade can be removed by pickling and fluid polishing becomes possible. To improve Door can be. As a result, it is possible to reduce the manufacturing cost of the machining work of the stationary blades of the steam turbine in a short working schedule.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a machining procedure for carrying out an electric discharge machining method for a steam turbine stationary blade according to an embodiment of the present invention.

FIG. 2 is a schematic view showing pickling of a stationary blade of a steam turbine partition plate.

FIG. 3 is a schematic view showing a method of processing a partition plate of a conventional general steam turbine.

FIG. 4 is a schematic view showing a method of processing a partition plate of a conventional steam turbine.

FIG. 5 is a schematic view (VV cross section in FIG. 4) showing a method for processing a vane of a steam turbine by conventional electric discharge machining.

[Explanation of symbols]

 11 Large Roughing Electrode 12 Medium Roughing Electrode 13 Finishing Electrode 14 Outlet Rounding Electrode 15 Outlet Holding Electrode 31 Pickling Tank 32 Pickling Liquid 20 Partition Plate 21 Disk 23 Stator Blade 24 Steam Passage

Claims (1)

[Claims] 1. A discharge machining method for machining a stationary blade of a partition plate interposed between a plurality of stages of steam turbine blades, wherein a lower surface of the partition plate disk is positioned with the fluid outlet side of the stationary blade as an upper surface. From the side to form the stationary blade by electric discharge machining, and finish machining the edges and steps on the side of the stationary blade formed by electric discharge machining from the upper surface side of the partition plate disk, and then the electric discharge machined surface A method for electrical discharge machining of a steam turbine stationary blade, characterized in that an altered layer is removed by pickling.