Positioning device for installing and welding steam turbine nozzle

Abstract

The utility model relates to the technical field of steam turbine nozzles, and discloses a positioning device for installing and welding a steam turbine nozzle, the positioning device comprises a bottom plate, an arc-shaped positioning plate and an arc-shaped fixing plate, the arc-shaped positioning plate and the arc-shaped fixing plate are concentrically arranged and are arranged on the bottom plate at intervals from inside to outside; an arc-shaped groove with an upward opening is formed in the upper surface of the arc-shaped positioning plate and used for positioning the lower end of the nozzle inner ring, and a pressing block assembly is arranged between the arc-shaped positioning plate and the arc-shaped fixing plate and used for pressing and fixing the lower side of the shroud ring to the arc-shaped positioning plate. The positioning device further comprises a clamping assembly which is arranged between the upper end of the nozzle inner ring and the upper end of the shroud ring and used for clamping and fixing the nozzle inner ring and the upper end of the shroud ring. By means of the positioning device, the assembly positioning accuracy of the nozzle inner ring and the shroud ring can be guaranteed, meanwhile, welding deformation can be prevented in the welding process, and the welding quality of the nozzle is guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of steam turbine nozzles, in particular to a positioning device for assembly welding of steam turbine nozzles. Background Art

[0002] The nozzle is one of the main components of the steam turbine and an important component for realizing the thermal-dynamic conversion of steam. The nozzle steam channel is a multi-cavity curved surface formed by the welding of the inner ring and its blade grid, the shroud and the outer ring. After the high-temperature and high-pressure steam expands and depressurizes through the preset steam flow channel, it forms a high-speed steam flow and is sprayed onto the rotor blades in the preset direction to perform work, converting the thermal energy of the first-stage steam into kinetic energy, realizing efficient functional conversion.

[0003] Combination Figure 1 As shown, the nozzle is generally a welded nozzle inner ring 1 (including the inner ring and its blade grid), a shroud 2 and an outer ring 3. The whole circle is divided into four arc segments. The shroud 2 is assembled in sections on the blade grid of the nozzle inner ring 1, the shaped holes are filled and welded, and then the outer ring 3 is assembled and the main weld is welded.

[0004] In the prior art, the nozzle material is mostly made of high-strength heat-resistant steel with complex alloy composition, which is difficult to weld and easily causes welding quality defects. In addition, the prior art lacks an effective positioning device to position the nozzle parts, and the welding process of the nozzle is cumbersome, which makes it difficult to control welding deformation and seriously affects the welding efficiency and welding quality of the nozzle. Utility Model Content

[0005] The purpose of the utility model is to solve the problem in the prior art that the welding deformation is not controlled due to the lack of an effective positioning device for positioning the nozzle parts, which further affects the welding quality of the nozzle. A positioning device for assembling and welding the steam turbine nozzle is provided. The positioning device for assembling and welding the steam turbine nozzle can improve the positioning accuracy of the nozzle parts, ensure the welding quality of the steam turbine nozzle and help improve the welding efficiency.

[0006] In order to achieve the above-mentioned object, the utility model provides a positioning device for welding a steam turbine nozzle, comprising a bottom plate, an arc-shaped positioning plate and an arc-shaped fixing plate, wherein the arc-shaped positioning plate and the arc-shaped fixing plate are arranged concentrically and are spaced from the inside to the outside on the bottom plate;

[0007] The upper surface of the arc-shaped positioning plate is provided with an arc-shaped groove opening upward for positioning the lower end of the nozzle inner ring, and a pressure block assembly is provided between the arc-shaped positioning plate and the arc-shaped fixing plate, and the pressure block assembly is used to press and fix the lower side of the circumferential belt to the arc-shaped positioning plate. The positioning device also includes a clamping assembly arranged between the upper end of the nozzle inner ring and the upper end of the circumferential belt for clamping and fixing the nozzle inner ring and the upper end of the circumferential belt.

[0008] Preferably, the width of the arc groove is greater than the width of the lower end of the nozzle inner ring, and the positioning device also includes a positioning block arranged between the circumferential belt and the nozzle inner ring, and the circumferential belt is configured to be able to position the nozzle inner ring to the inner groove wall of the arc groove through the positioning block.

[0009] Preferably, a curved positioning platform is provided on one side of the curved positioning plate close to the curved fixing plate for supporting the circumference belt, and the width of the curved positioning platform is smaller than the width of the lower end of the circumference belt.

[0010] Preferably, an inner tie bar is fixed on the bottom plate located on the inner side of the arc-shaped positioning plate, and the inner tie bar is used to block and limit the inner ring of the nozzle.

[0011] Preferably, the pressing block assembly is provided in plurality, and the plurality of pressing block assemblies correspond to the plurality of shrouds one by one, so as to be used for respectively pressing and fixing the lower sides of the plurality of shrouds to the arc-shaped positioning plate;

[0012] Preferably, the pressing block assembly comprises two pressing blocks, a pressing screw is arranged between the two pressing blocks, and the pressing screw is configured to be screwed into between the two pressing blocks so that the two pressing blocks squeeze the arc-shaped fixing plate and the shroud respectively.

[0013] Preferably, the clamping assembly comprises an arch clamp, one end of which is provided with a threaded hole, a freely rotatable clamping screw is provided in the threaded hole, and the clamping screw is arranged to be able to rotate so that its inner end approaches the other end of the arch clamp, so as to clamp and fix the nozzle inner ring and the upper end of the shroud;

[0014] Preferably, the clamping assembly further comprises a limit block, which is arranged between the nozzle inner ring and the upper end of the shroud and can respectively abut the nozzle inner ring and the shroud when the clamping screw rotates close to the other end of the bow clamp.

[0015] Preferably, a lifting screw is provided on the bottom surface of the bottom plate, and the lifting screw is configured to be screwed into the arc-shaped groove from bottom to top, so as to lift the inner ring of the nozzle upward.

[0016] Through the above technical scheme, an arc-shaped positioning plate and an arc-shaped fixing plate are arranged on the bottom plate at intervals, and the lower end of the shroud is positioned in cooperation with the pressing block assembly arranged between the arc-shaped positioning plate and the arc-shaped fixing plate. The arc-shaped groove arranged on the arc-shaped positioning plate can position the lower end of the nozzle inner ring, and a clamping assembly is arranged between the upper end of the nozzle inner ring and the upper end of the shroud, and the clamping assembly can clamp and fix the nozzle inner ring and the upper end of the shroud; thus, the utility model positions and fixes the relative position of the nozzle inner ring and the shroud through multiple positions, thereby ensuring the assembly positioning accuracy of the nozzle inner ring and the shroud, and at the same time can effectively prevent welding deformation during welding, thereby ensuring the welding quality of the nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the steam turbine nozzle in the utility model;

[0018] Figure 2 It is a schematic diagram of the nozzle inner ring and the shroud in the utility model being assembled on the positioning device;

[0019] Figure 3 This is a cross-sectional view of a positioning device provided by the utility model for assembling and positioning the inner ring of the nozzle and the shroud;

[0020] Figure 4 yes Figure 3 A magnified schematic diagram of position A in the middle;

[0021] Figure 5 It is a schematic diagram of a multi-section nozzle welding part provided by the utility model after being assembled into a circle and shrink-fitted onto an outer ring;

[0022] Description of Reference Numerals

[0023] 1. Nozzle inner ring; 2. Belt; 3. Outer ring; 10. Bottom plate; 11. Inner tie bar; 111. Fixing screw; 112. Spacer; 12. Lifting screw; 20. Arc positioning plate; 21. Arc groove; 22. Arc positioning platform; 30. Arc fixing plate; 40. Press block assembly; 41. Press block; 42. Clamping screw; 50. Positioning block; 60. Bow clamp; 61. Clamping screw; 62. Limit block; 70. Strap. DETAILED DESCRIPTION

[0024] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0025] As mentioned above, combined with Figure 2 , Figure 3 and Figure 4As shown, the utility model provides a positioning device for assembling and welding turbine nozzles, comprising a base plate 10, an arc-shaped positioning plate 20 and an arc-shaped fixing plate 30, wherein the arc-shaped positioning plate 20 and the arc-shaped fixing plate 30 are arranged concentrically and are spaced from the inside to the outside on the base plate 10; an arc-shaped groove 21 opening upward is provided on the upper surface of the arc-shaped positioning plate 20 for positioning the lower end of the nozzle inner ring 1, a pressing block assembly 40 is provided between the arc-shaped positioning plate 20 and the arc-shaped fixing plate 30, and the pressing block assembly 40 is used to press and fix the lower side of the shroud 2 to the arc-shaped positioning plate 20, and the positioning device also includes a clamping assembly arranged between the upper end of the nozzle inner ring 1 and the upper end of the shroud 2 for clamping and fixing the nozzle inner ring 1 and the upper end of the shroud 2.

[0026] In the technical solution provided by the utility model, an arc-shaped positioning plate 20 and an arc-shaped fixing plate 30 are arranged on the base plate 10 at intervals, and the lower end of the shroud 2 is positioned by cooperating with the pressing block assembly 40 arranged between the arc-shaped positioning plate 20 and the arc-shaped fixing plate 30. The arc-shaped groove 21 arranged on the arc-shaped positioning plate 20 can position the lower end of the nozzle inner ring 1, and a clamping assembly is arranged between the upper end of the nozzle inner ring 1 and the upper end of the shroud 2, and the clamping assembly can clamp and fix the nozzle inner ring 1 and the upper end of the shroud 2; thus, the utility model positions and fixes the relative position of the nozzle inner ring 1 and the shroud 2 through multiple positions, thereby ensuring the assembly positioning accuracy of the nozzle inner ring 1 and the shroud 2, and can effectively prevent welding deformation during welding, thereby ensuring the welding quality of the nozzle.

[0027] It should be noted that in the present invention, the curvature of the arc groove 21 is equal to the inner curvature of the nozzle inner ring 1, and the outer curvature of the arc positioning plate 20 is equal to the curvature of the shroud 2, so that the nozzle inner ring 1 and the shroud 2 can be positioned respectively.

[0028] It can be understood that in the present invention, when the lower end of the nozzle inner ring 1 is positioned by the arc groove 21, the width of the arc groove 21 can be set to be equal to the width of the lower end of the nozzle inner ring 1, and the positioning is achieved when the lower end of the nozzle inner ring 1 is inserted into the arc groove 21, but this is not conducive to the removal of the nozzle inner ring 1 from the arc positioning plate 20; in some embodiments, the width of the arc groove 21 is greater than the width of the lower end of the nozzle inner ring 1, and the positioning device also includes a positioning block 50 arranged between the shroud 2 and the nozzle inner ring 1, and the shroud 2 is arranged to be able to position the nozzle inner ring 1 to the inner groove wall of the arc groove 21 through the positioning block 50.

[0029] It is understandable that by setting the width of the arc groove 21 to be greater than the lower end width of the nozzle inner ring 1, and by setting the positioning block 50 between the shroud 2 and the nozzle inner ring 1, when the pressing block assembly 40 pushes the shroud 2 to position it, the positioning block 50 pushes the nozzle inner ring 1 to simultaneously position the lower end of the nozzle inner ring 1 to the inner groove wall of the arc groove 21. Through the above-mentioned structural design of the utility model, it is possible to simultaneously realize the assembly and positioning of the shroud 2 and the nozzle inner ring 1, and it is also convenient for subsequent disassembly and assembly. After the assembly and welding are completed, the pressing block assembly 40 is released. Since the width of the arc groove 21 is greater than the lower end width of the nozzle inner ring 1, the nozzle inner ring 1 can be easily removed from the arc positioning plate 20; in addition, it is understandable that by setting the positioning block 50 in the steam passage between the shroud 2 and the nozzle inner ring 1, it is also possible to accurately ensure the height dimension of the steam passage after the nozzle welding is completed.

[0030] In some embodiments, a curved positioning platform 22 is provided on one side of the curved positioning plate 20 close to the curved fixing plate 30 for supporting the shroud 2, and the width of the curved positioning platform 22 is smaller than the width of the lower end of the shroud 2. By forming the curved positioning platform 22 for supporting the shroud 2 on the curved positioning plate 20, it is convenient to position the shroud 2, and the width of the curved positioning platform 22 is set to be smaller than the width of the lower end of the shroud 2, so as to ensure that the pressing block assembly 40 can squeeze the shroud 2 and ensure effective positioning. Figure 4 As shown, when the pressing block assembly 40 is in close contact with the outer side of the circumferential belt 2 , there is a lateral spacing between the pressing block assembly 40 and the outer side of the arc-shaped positioning plate 20 .

[0031] It can be understood that when the width of the positioning block 50 is set to enable the belt 2 to be close to the outer side surface of the positioning block 50, there is a lateral distance between the belt 2 and the arc positioning plate 20, so as to ensure that the belt 2 can position the nozzle inner ring 1 to the inner groove wall of the arc groove 21 through the positioning block 50.

[0032] In some embodiments, an inner tie bar 11 is fixed on the bottom plate 10 located on the inner side of the arc-shaped positioning plate 20 , and the inner tie bar 11 is used to block and limit the nozzle inner ring 1 .

[0033] Specifically, the outer side surface of the inner tie bar 11 is set to an arc shape that matches the inner side surface of the nozzle inner ring 1. It can be understood that the additional inner tie bar 11 is used to stop and limit the nozzle inner ring 1, effectively reducing the stress deformation during the welding process of the nozzle inner ring 1 and the shroud 2. At the same time, the inner tie bar 11 can also be used for subsequent rounding fixation to ensure the welding accuracy with the outer ring 3.

[0034] In a specific embodiment of the utility model, a fixing screw 111 extending in a vertical direction is provided on the inner tie bar 11, the lower end of the fixing screw 111 is passed through the base plate 10, the upper end of the fixing screw 111 is locked to the upper side surface of the inner tie bar 11 by a nut and a gasket, the end face of the inner tie bar 11 close to the nozzle inner ring 1 abuts against the nozzle inner ring 1, and a pad 112 is provided between the end away from the nozzle inner ring 1 and the base plate 10.

[0035] In the present invention, the shroud 2 is assembled in sections on the blade cascade of the nozzle inner ring 1, such as Figure 2 As shown, a single nozzle weldment includes an arc segment nozzle inner ring 1 and four arc segment shrouds 2 .

[0036] In order to ensure the assembly accuracy of the shroud 2 and the nozzle inner ring 1 and prevent welding deformation during welding, a plurality of the pressing block assemblies 40 are provided, and the plurality of the pressing block assemblies 40 correspond to the plurality of shrouds 2 one by one, so as to press and fix the lower sides of the plurality of shrouds 2 to the arc-shaped positioning plate 20 respectively;

[0037] In the present invention, the pressing block assembly 40 can adopt any appropriate structural form, as long as it can press and fix the lower side of the shroud 2 to the arc-shaped positioning plate 20. In some embodiments, the pressing block assembly 40 includes two pressing blocks 41, and a pressing screw 42 is arranged between the two pressing blocks 41. The pressing screw 42 is configured to be screwed into between the two pressing blocks 41, so that the two pressing blocks 41 squeeze the arc-shaped fixing plate 30 and the shroud 2 respectively.

[0038] It is understandable that, since the arc-shaped fixing plate 30 is fixed on the bottom plate 10 , when the two pressing blocks 41 squeeze the arc-shaped fixing plate 30 and the shroud 2 respectively, the lower side of the shroud 2 can be pressed and positioned to the arc-shaped positioning plate 20 .

[0039] Through the above-mentioned structural setting, the assembly accuracy of the belt 2 can be ensured, and disassembly is convenient. After welding is completed, the clamping screw 42 is unscrewed, and the preset gap between the two clamping blocks 41 can facilitate its removal, thereby facilitating the belt 2 to be removed from between the arc-shaped fixing plate 30 and the arc-shaped positioning plate 20, providing favorable conditions for heat treatment immediately after welding.

[0040] In some embodiments, the front end of the clamping screw 42 is provided with a conical chamfer, and the conical chamfer can achieve guiding positioning when the clamping screw 42 is screwed into between the two clamping blocks 41, thereby facilitating the installation of the clamping screw 42.

[0041] In the present invention, the clamping assembly can adopt any appropriate structural form, as long as it can clamp and fix the nozzle inner ring 1 and the upper end of the shroud 2. In some embodiments, the clamping assembly includes an arch clamp 60, one end of which is provided with a threaded hole, and a freely rotatable clamping screw 61 is provided in the threaded hole, and the clamping screw 61 is configured to be able to rotate so that its inner end is close to the other end of the arch clamp 60, so as to clamp and fix the nozzle inner ring 1 and the upper end of the shroud 2.

[0042] In some embodiments, the clamping assembly also includes a limit block 62, which is arranged between the nozzle inner ring 1 and the upper end of the shroud 2, and can abut against the nozzle inner ring 1 and the shroud 2 respectively when the clamping screw 61 rotates close to the other end of the bow clamp 60.

[0043] In some embodiments, a plurality of the limit blocks 62 are provided, and the plurality of limit blocks 62 are arranged at intervals along the gap between the nozzle inner ring 1 and the shroud 2 .

[0044] More preferably, two limit blocks 62 are respectively provided at both ends of the nozzle inner ring 1, and limit blocks 62 are respectively provided at adjacent positions of the two shrouds 2. This can prevent the shroud 2 from being tilted by the tightening screw 61 while positioning the relative positions of the nozzle inner ring 1 and the shroud 2.

[0045] In some embodiments, a jacking screw 12 is provided on the bottom surface of the bottom plate 10, and the jacking screw 12 is configured to be screwed into the arc groove 21 from bottom to top, so as to jack up the nozzle inner ring 1. With the above-mentioned structural arrangement, when the nozzle inner ring 1 and the shroud 2 are stuck due to deformation during the welding process, the nozzle inner ring 1 can be jacked up by the jacking screw 12 provided on the bottom plate 10.

[0046] The second aspect of the utility model provides a method for assembling a turbine nozzle, the method comprising using the above-mentioned positioning device for assembling a turbine nozzle to position and assemble multiple sections of shrouds 2 and a section of nozzle inner ring 1, and then filling and welding the shroud-shaped holes to obtain a section of nozzle welded part.

[0047] Based on the positioning device provided by the utility model, the nozzle inner ring 1 and the shroud 2 are positioned and assembled, and then the shroud-shaped holes are filled and welded, which is beneficial to controlling the dimensional accuracy of the steam channel and reducing the cumulative error of the nozzle steam channel dimension.

[0048] Furthermore, the method also includes performing a first heat treatment on the nozzle welded part obtained by welding to eliminate welding stress. In some embodiments, the conditions of the first heat treatment include: furnace temperature ≤200°C, heating rate ≤55°C / h, insulation temperature 730±10°C, insulation time 6h, cooling rate ≤55°C / h, cooling to 300°C and lifting the furnace cover, and air cooling when the temperature is ≤150°C; it should be noted that the positioning device provided by the utility model can quickly release the nozzle welded part formed by welding the shroud and the inner ring of the nozzle, so as to facilitate the first heat treatment immediately after welding to eliminate welding stress, and cooperate with the conditions of the first heat treatment provided by the utility model to minimize welding quality defects.

[0049] Furthermore, the method further comprises repeating the operations of positioning and assembling, filling and welding the circumferential belt profile hole and the first heat treatment to obtain a plurality of sections of the nozzle welded parts, then assembling and fixing the plurality of sections of the nozzle welded parts together, welding the grooves of the circumferential belt 2 and the outer ring 3, then shrink-fitting the outer ring 3, and then welding the main welds between the outer ring 3 and the plurality of sections of the nozzle welded parts; in actual operation, combined with Figure 5 As shown, a plurality of sections of nozzle welding parts are assembled and fixed on a welding chassis by welding a strap 70 to the inner tie bars 11 of two adjacent nozzle welding parts.

[0050] In order to improve the reliability of the circular fixation of the multi-section nozzle welding parts, the butt plate 70 is welded simultaneously at the joints of the upper end surface and the lower end surface of two adjacent inner tie bars 11 .

[0051] Before the outer ring 3 is heat-shrink-fitted, the welding groove size of the shroud 2 and the outer ring 3 is matched. Specifically, the blunt edge groove of the outer ring 3 and the shroud 2 is designed with an interference fit of 0.2-0.3mm. Through the above operation, when the outer ring 3 is heat-shrink-fitted, the outer ring 3 is tightly attached to the shroud 2 without any gap, thereby ensuring the welding quality of the main weld.

[0052] Furthermore, the method also includes heating the outer ring 3 and the multiple sections of the nozzle welding parts during the main weld to ensure that the temperature between the welding layers is not less than 200°C.

[0053] In the utility model, a plurality of nozzle welding parts are assembled into a full circle, and a groove is provided at the same time to facilitate the welding of the main weld of the full circle, so that the welding process can be carried out continuously, and heating is performed at the same time to ensure the temperature between the welding layers. Compared with the single arc segment welding and multiple arc initiation intermittent welding method, the method provided by the utility model is conducive to ensuring welding quality, reducing welding deformation, reducing pause time and improving welding efficiency.

[0054] In some embodiments, the method further includes alternately welding the main welds on the steam inlet side and the steam outlet side during the main weld welding, thereby reducing welding deformation through alternate welding.

[0055] In some embodiments, the method further includes performing a second heat treatment after the main weld is welded. It is understandable that the welding stress can be eliminated through the second heat treatment to minimize welding quality defects. In some embodiments, the conditions of the second heat treatment include: furnace temperature ≤200°C, heating rate ≤55°C / h, insulation temperature 730±10°C, insulation time 8h, cooling rate ≤55°C / h. Cool down to 300°C and lift the furnace cover, and hang it out for air cooling when the temperature is ≤150°C. It should be noted that through the conditions of the second heat treatment provided by the utility model, reliable heat treatment of welded parts after welding is achieved, and welding stress can be eliminated in time to minimize welding quality defects.

[0056] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A positioning device for welding a steam turbine nozzle, characterized in that: It comprises a bottom plate (10), an arc-shaped positioning plate (20) and an arc-shaped fixing plate (30), wherein the arc-shaped positioning plate (20) and the arc-shaped fixing plate (30) are arranged concentrically and are spaced from the inside to the outside on the bottom plate (10); The upper surface of the arc-shaped positioning plate (20) is provided with an arc-shaped groove (21) opening upward for positioning the lower end of the nozzle inner ring (1); a pressing block assembly (40) is provided between the arc-shaped positioning plate (20) and the arc-shaped fixing plate (30); the pressing block assembly (40) is used to press and fix the lower side of the shroud (2) to the arc-shaped positioning plate (20); the positioning device also includes a clamping assembly provided between the upper end of the nozzle inner ring (1) and the upper end of the shroud (2) for clamping and fixing the nozzle inner ring (1) and the upper end of the shroud (2).

2. The positioning device for welding a steam turbine nozzle according to claim 1, characterized in that: The width of the arc-shaped groove (21) is greater than the width of the lower end of the nozzle inner ring (1), and the positioning device also includes a positioning block (50) arranged between the circumferential belt (2) and the nozzle inner ring (1), and the circumferential belt (2) is arranged to be able to position the nozzle inner ring (1) to the inner groove wall of the arc-shaped groove (21) through the positioning block (50).

3. The positioning device for welding a steam turbine nozzle according to claim 1, characterized in that: A curved positioning platform (22) is provided on one side of the curved positioning plate (20) close to the curved fixing plate (30) for supporting the circumferential belt (2), and the width of the curved positioning platform (22) is smaller than the width of the lower end of the circumferential belt (2).

4. The positioning device for welding a steam turbine nozzle according to claim 1, characterized in that: An inner tie bar (11) is fixed on the bottom plate (10) located on the inner side of the arc-shaped positioning plate (20), and the inner tie bar (11) is used to block and limit the nozzle inner ring (1).

5. The positioning device for welding a steam turbine nozzle according to claim 1, characterized in that: A plurality of the pressing block assemblies (40) are provided, and the plurality of the pressing block assemblies (40) correspond one-to-one to the plurality of circumferential belts (2), so as to be used for respectively pressing and fixing the lower sides of the plurality of circumferential belts (2) to the arc-shaped positioning plate (20).

6. The positioning device for welding a steam turbine nozzle according to claim 5, characterized in that: The pressing block assembly (40) comprises two pressing blocks (41), a clamping screw (42) being arranged between the two pressing blocks (41), and the clamping screw (42) being arranged to be screwed into between the two pressing blocks (41) so that the two pressing blocks (41) can respectively squeeze the arc-shaped fixing plate (30) and the shroud (2).

7. The positioning device for welding a steam turbine nozzle according to claim 1, characterized in that: The clamping assembly comprises a bow-shaped clamp (60), one end of which is provided with a threaded hole, a freely rotatable clamping screw (61) being provided in the threaded hole, and the clamping screw (61) being arranged to be able to rotate so that its inner end approaches the other end of the bow-shaped clamp (60) so as to clamp and fix the nozzle inner ring (1) and the upper end of the shroud (2).

8. The positioning device for welding a steam turbine nozzle according to claim 7, characterized in that: The clamping assembly further comprises a limit block (62), which is arranged between the nozzle inner ring (1) and the upper end of the shroud (2), and is capable of respectively abutting against the nozzle inner ring (1) and the shroud (2) when the clamping screw (61) rotates close to the other end of the bow clamp (60).

9. The positioning device for welding a steam turbine nozzle according to claim 1, characterized in that: A lifting screw (12) is provided on the bottom surface of the bottom plate (10), and the lifting screw (12) is configured to be screwed into the arc-shaped groove (21) from bottom to top, so as to lift the nozzle inner ring (1) upward.

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