JPH06221104A - Production of steam turbine spool nozzle diaphragm - Google Patents

Abstract

PURPOSE:To reduce shrinkage deformation in welding so as to improve accuracy in combination by closely sticking components such as a nozzle ring in which a nozzle plate is incorporated in holes of back plates or diaphragm inner and outer rings, etc., to each other while keeping clearance between both faces and being jointed by electron beam welding. CONSTITUTION:Back plates 21a, 21b on an inner ring side and an outer ring side are combined together, both ends of a nozzle plate 22 are inserted into a number of support holes and fixed by spot welding so as to form a nozzle ring 23. The nozzle ring 23 and an end block 24 are closely stuck to a diaphragm inner and outer ring 26, which has finishing process allowance 25 in only the minimum range, in such a manner as setting the interval between respective faces to be 0-0.2mm so as to joint its close contact part by electron beam welding. Welding face between a strip holder 27 and diaphragm inner and outer ring 26, and welding face between a cover plate 28 and diaphragm inner and outer ring 26 are processed in the same way. Thus quality of welding parts of respective components is improved so as to shorten working time of machine processing., etc.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for manufacturing a spool nozzle diaphragm in a steam turbine.

[0002]

2. Description of the Related Art A conventional steam turbine spool nozzle diaphragm is, as shown in FIGS. 5 and 6, provided between an outer peripheral portion of a diaphragm inner ring 1 and an inner peripheral portion of a diaphragm outer ring 2.
A nozzle ring 5 in which a large number of nozzle plates 3 and the corresponding plate 4 are joined by seal welding and an end block 6 forming a horizontal joint surface of a steam passage portion are joined by submerged arc welding. Then, the strip holder 7 having tip fins for reducing the tip leakage loss at the tip of the blade on the steam outlet side of the outer ring of the diaphragm is joined by submerged arc welding. Further, a cover spray 8 having a window for guiding the steam flowing out of the spool valve to the steam inlet side of the inner and outer rings of the diaphragm to the spool nozzle diaphragm, and a rib plate 9 and an end plate 10 for partitioning the chamber of each valve are fillet welded or a submerged arc. Join by welding. In FIG. 5, the hatched portion is the portion where submerged arc welding or fillet welding is performed.

As a manufacturing procedure of a conventional steam turbine spool nozzle diaphragm, first, an inner ring side contact plate 4a and an outer ring side contact plate 4b are concentrically combined, and a large number of holes are laser-perforated in the radial direction of the contact plate. Both ends of the multiple nozzle plates 3 are inserted into the support holes. Next, by sealingly welding the end portion of the nozzle plate and the support hole of the plate, the nozzle ring 5
To form. The hatched portion in FIG. 6 is a seal-welded portion.

The nozzle ring 5 and the end block 6 are fitted to the outer peripheral portion of the diaphragm inner ring 1 and the inner peripheral portion of the diaphragm outer ring 2 which have been grooved in advance, and the groove portions are fixed by submerged arc welding. Further, the steam outlet side of the outer ring of the diaphragm is shaped, and the strip holder 7 which has been grooved in advance is fixed by submerged arc welding. Further, the steam inlet side of the inner and outer rings of the diaphragm is shaped, and the cover plate 8, the rib plate 9, and the end plate 10 are fixed by fillet welding or submerged arc welding.

[0005]

However, according to the conventional method of manufacturing the spool nozzle diaphragm as described above,
Submerged arc welding or fillet welding has a total of 10 or more points, and the heat input during welding is large, so that welding deformation easily occurs and the thermal stress generated in each part such as the nozzle plate is large. Therefore, in consideration of welding deformation, a finishing machining allowance of about 10 mm must be provided over the entire circumference and the entire surface, and a large amount of machining is required to finish the intended final shape 11. Further, the residual stress is large and it is necessary to anneal to remove the stress, and there are drawbacks such that the anneal causes deformation and an oxide film. Furthermore, the fact that there are many welding points means that the manufacturing process becomes frequent and the working time becomes long, and there is a high possibility that welding defects will remain, which may cause cracks due to long-term use. .

The present invention has been made in view of the above-mentioned circumstances, and uses electron beam welding to reduce the amount of welding and heat input during welding, thereby reducing shrinkage deformation during welding and finishing. The manufacturing method of the steam turbine spool nozzle diaphragm that can reduce the assembly / disassembly process and the number of parts processing man-hours, and improve the accuracy of combining each part by manufacturing a circular ring shape throughout the entire manufacturing process. It is intended to be provided.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a nozzle plate is inserted into a hole of a corresponding plate and fixed by spot welding to a minimum to form a nozzle ring. The strip holder, cover plate, rib plate, and end plate are not groove-processed, but they are closely attached so that the gap between the surfaces is 0 to 0.2 mm, they are joined by electron beam welding, and the finishing machining allowance is added. Provided only in the minimum range of welding surface, joining surface, etc., and manufactured in a circular ring shape throughout the entire manufacturing process,
It is characterized in that it is divided into a half ring shape by a method such as wire cutting at the final processing stage.

[0008]

The present invention reduces the amount of welding and the heat input during welding to reduce shrinkage deformation during welding, minimizes finishing work, and produces a circular ring shape throughout the entire manufacturing process. , Reduce the assembly / disassembly process and part processing man-hours, and improve the accuracy of combining each part.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

Inner ring side contact plate 21a and outer ring side contact plate 21b are concentrically combined, and both ends of many nozzle plates 22 are inserted into many support holes formed by laser in the radial direction of this contact plate. Nozzle ring 23
To form. This nozzle ring 23 and end block 24
The finishing cost is limited to the minimum range such as the welding surface and the mating surface.
A circular ring-shaped diaphragm inner and outer ring 26 with 25 is closely attached to each other so that the clearance between the surfaces is 0 to 0.2 mm. The contact portions thus combined are joined by electron beam welding. In electron beam welding, as shown in Fig. 4, the incidence of internal defects such as cracks and blowholes due to welding becomes extremely high when the gap between the weld surfaces is 0.2 mm or more, and phenomena such as dents in the weld occur. Since the reliability of the welded joint is impaired, the gap between the welding surfaces should be 0 to 0.2 mm. The hatched portion in FIG. 1 is a portion to be electron beam welded.

A circular ring-shaped strip holder
Regarding the welding surface of 27 and the diaphragm inner / outer ring 26, and the welding surface of the circular ring-shaped cover plate 28 and the diaphragm inner / outer ring 26 as well, the gap is maintained at 0 to 0.2 mm and brought into close contact, and they are joined by electron beam welding. .

The rib plate 29 and the end plate 30 are butted in a T-shape with the cover plate 28, and the gap between the joint surfaces is maintained at 0 to 0.2 mm for close contact, and the ribs 29 and end plates 30 are joined by electron beam welding from the direction perpendicular to the joint surfaces. To do.

When a nozzle diaphragm is manufactured by electron beam welding in which an electron beam having a high energy density is applied to each component and welded together, the range of the heat-affected zone due to welding is narrow, and the circumferential and radial directions during welding are small. Since the amount of shrinkage deformation and the amount of swing in the axial direction are about 1 mm or less, which is extremely small compared to the conventional welding method, the finishing machining allowance 25 is welded at the material stage,
Limiting to the minimum range such as the mating surface, machining is made as unnecessary as possible.

Further, as shown in FIG. 3, by manufacturing in a circular ring shape over the entire manufacturing process, the conventional upper and lower half-fitting,
It is possible to omit the process of semi-disassembly of the upper air, improve the work efficiency of parts processing, and improve the accuracy of combination of parts. The nozzle diaphragm manufactured in the circular ring shape as described above is cut by a method such as wire cutting in the final processing stage to manufacture a semi-ring product having an initial target shape.

[0015]

As described above, according to the present invention, the quality and reliability of the welded portion of each component of the electron beam welded steam turbine spool nozzle diaphragm are high, and machining, assembly and disassembly, etc. are performed. Excellent effects such as a significant reduction in working time can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a steam turbine spool nozzle diaphragm of the present invention.

FIG. 2 is a perspective view of a steam turbine spool nozzle diaphragm of the present invention.

FIG. 3 is a top view of a steam turbine spool nozzle diaphragm of the present invention.

FIG. 4 is a characteristic diagram showing a relationship between an internal defect occurrence rate and a welding surface gap.

FIG. 5 is a cross-sectional view showing a conventional steam turbine spool nozzle diaphragm.

FIG. 6 is a configuration diagram showing a conventional steam turbine spool nozzle diaphragm.

[Explanation of symbols]

1 ... Diaphragm inner ring, 2 ... Diaphragm outer ring, 3 ... Nozzle plate, 4a ... Inner ring side contact plate, 4b ... Outer ring side contact plate, 5 ... Nozzle ring, 6 ... End block, 7 ... Strip holder, 8 ... Cover plate, 9 ... rib plate, 10 ... end plate, 11 ... final finish shape, 21a ... inner ring side contact plate,
21b ... Outer ring side contact plate, 22 ... Nozzle plate, 23 ... Nozzle ring,
24 ... End block, 25 ... Finishing allowance, 26 ... Diaphragm inner and outer rings, 27 ... Strip holder, 28 ... Cover plate, 29 ... Rib plate, 30 ... End plate.

Claims (3)

[Claims] 1. A nozzle ring or a diaphragm inner / outer ring formed by incorporating a nozzle plate into a hole of a corresponding plate, an end block, a strip holder, a cover plate, a rib plate, an end plate, and other components are provided with a gap between their surfaces. A method for manufacturing a steam turbine spool nozzle diaphragm, characterized in that the steam turbine spool nozzle diaphragm is held by closely holding it at 0 to 0.2 mm and joined by electron beam welding. 2. The method of manufacturing a steam turbine spool nozzle diaphragm according to claim 1, wherein a finishing machining allowance is provided only in a minimum range such as an electron beam welding surface or a joining surface. 3. The steam turbine spool nozzle diaphragm according to claim 1, wherein the steam turbine spool nozzle diaphragm is manufactured in a circular ring shape during the entire manufacturing process, and is divided into a half ring shape by a method such as wire cutting in a final processing step. Method.