A method for welding a large gas turbine low pressure turbine guide vane

Abstract

The present application relates to the field of aircraft engine blade processing, and discloses a welding preparation method for a large gas turbine low-pressure turbine guide vane, which utilizes matched tooling positioning to ensure the relative position accuracy of the inner flow channel profiles of two single-union vanes, so that the step of the inner flow channel profiles of the two vanes and the overall fluctuation after welding meet the design requirements, smooth transition of the airflow channel is realized, unnecessary loss in the airflow flow process is avoided, meanwhile, the matched tooling can stably constrain the vane during welding, the influence of welding deformation on the vane profile accuracy is reduced, the welding preparation accuracy and product qualification rate of the large double-union low-pressure turbine guide vane are effectively improved, and the preparation and processing cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of aero-engine blade processing, and discloses a welding preparation method for low-pressure turbine guide blades of large gas turbines. Background Technology

[0002] Large gas turbines, as core equipment in the fields of energy power and ship propulsion, directly determine their power generation efficiency, range, and reliability. Low-pressure turbine guide vanes are key components in the hot-end of gas turbines, responsible for smoothly guiding high-temperature gas into subsequent moving blades and achieving aerodynamic acceleration. Their machining accuracy and consistency have a significant impact on the overall lifespan and economic efficiency of the turbine. Currently, these blades are mostly manufactured using a machining followed by welding process, which presents the following machining challenges in actual production:

[0003] (1) The undulation of the internal flow channel surface of low-pressure turbine guide vanes is difficult to control, resulting in poor matching consistency and a lack of quick matching methods. After grinding, the internal flow channel surface of single low-pressure turbine guide vanes exhibits varying degrees of machining deformation and dimensional fluctuations. Direct pairing and welding can easily lead to excessive height differences in the flow channel surface, resulting in increased airflow loss. Traditional methods lack quantitative control and matching means, and relying solely on experience for matching makes it difficult to guarantee the aerodynamic performance of each pair of blades.

[0004] (2) The wear-resistant layer welded on the radial surface of the lower edge plate requires high precision, and it is easy to leave residue or overcut when removing the solder. In order to ensure the quality of the wear-resistant layer repair welding, the original solder must be completely removed before repair welding, but the precision requirements of the part to be processed are extremely high. If traditional single-pass milling is used, it is difficult to ensure the integrity of the removal without damaging the substrate, and solder residue or dimensional deviations often occur, leading to the failure of subsequent repair welding or scrapping of the blade.

[0005] (3) When welding thin-walled baffles, deformation is prone to occur, and dimensional deviations are difficult to correct. The front and rear thin-walled baffles are affected by thermal stress during the brazing process, which can easily cause shrinkage or tensile deformation, causing critical dimensions to deviate from design requirements. Existing processes lack a dedicated correction method for the deformation of thin-walled baffles, and can only be corrected by repeated disassembly and welding or scrapping, which is costly and inefficient. Summary of the Invention

[0006] The purpose of this invention is to provide a welding preparation method for low-pressure turbine guide vanes of large gas turbines, which utilizes paired tooling to realize the steps and undulations of the inner flow channel surface of the double low-pressure turbine guide vanes, ensuring a smooth transition of the airflow channel.

[0007] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows: A method for welding and fabricating guide vanes for low-pressure turbines of large gas turbines, used to weld two single-unit low-pressure turbine guide vanes into a double-unit low-pressure turbine guide vane, includes the following steps: The surfaces to be brazed and the clamping and positioning surfaces are ground and machined on the upper and lower edge plates of the two single-stage low-pressure turbine guide vanes, respectively. According to the design position relationship of the low-pressure turbine guide vanes, two single low-pressure turbine guide vanes are paired and welded together using matching tooling to obtain a double low-pressure turbine guide vane semi-finished product. Thin-walled baffles and honeycomb are welded onto the lower edge plate of the semi-finished twin low-pressure turbine guide vane to obtain the finished twin low-pressure turbine guide vane.

[0008] Furthermore, it also includes: after obtaining the semi-finished product of the double low-pressure turbine guide vane, if there is a defect in the weld overlay wear-resistant layer on the radial surface of the lower edge plate of the semi-finished product of the double low-pressure turbine guide vane, the semi-finished product of the double low-pressure turbine guide vane is clamped on a milling fixture, and the existing weld overlay wear-resistant layer on the radial surface of the lower edge plate is removed by milling according to a preset number of passes and a preset feed amount per pass, and then the weld overlay wear-resistant layer is repaired by welding.

[0009] Furthermore, after the two single-unit low-pressure turbine guide vanes are paired and clamped on the pairing fixture, the height difference between the upper inner flow channel edge and the lower inner flow channel edge is measured between the two single-unit low-pressure turbine guide vanes. If the height difference between the upper inner flow channel edge and the lower inner flow channel edge is not greater than a preset threshold, the two single-unit low-pressure turbine guide vanes are welded into a double-unit low-pressure turbine guide vane semi-finished product. Otherwise, the two single-unit low-pressure turbine guide vanes are processed and re-measured until a double-unit low-pressure turbine guide vane semi-finished product is obtained.

[0010] Furthermore, the milling fixture includes a base, an X-axis positioning device, a Y-axis positioning device, and a Z-axis positioning device; the X-axis positioning device, the Y-axis positioning device, and the Z-axis positioning device are all mounted on the base and are used to position the semi-finished double low-pressure turbine guide vane on the base along the X-axis, Y-axis, and Z-axis directions after clamping the semi-finished double low-pressure turbine guide vane.

[0011] Furthermore, the X-axis positioning device includes a semi-finished inner flow channel surface positioning component; the inner flow channel surface positioning component is fixed on the base, and the semi-finished inner flow channel surface positioning component is provided with a positioning top post, the tip of which abuts against the inner flow channel surface of the upper edge plate of the low-pressure turbine guide vane.

[0012] Furthermore, the Z-axis positioning device includes a first positioning block for the upper edge plate of the semi-finished product and a clamping assembly for the upper edge plate of the semi-finished product; the first positioning block for the upper edge plate of the semi-finished product is fixed on the base, and the first positioning block for the upper edge plate of the semi-finished product is provided with an upper edge plate positioning surface that contacts the radial end face of the upper edge plate of the low-pressure turbine guide vane; the clamping assembly for the upper edge plate of the semi-finished product includes a pressure plate for the upper edge plate of the semi-finished product and a first locking bolt, one end of the pressure plate for the semi-finished product is connected to the base, the other end of the pressure plate for the semi-finished product is abutting against the upper edge plate of the double low-pressure turbine guide vane semi-finished product, and the pressure plate for the semi-finished product is provided with a first slotted hole, the first locking bolt passes through the first slotted hole and is threadedly connected to the base, for forcing the pressure plate for the semi-finished product to clamp the upper edge plate of the double low-pressure turbine guide vane semi-finished product, so as to clamp the upper edge plate of the low-pressure turbine guide vane by the first positioning block for the upper edge plate of the semi-finished product and the pressure plate for the upper edge plate of the semi-finished product.

[0013] Furthermore, the Z-axis positioning device also includes a first positioning block for the lower edge plate of the semi-finished product and a first clamping assembly for the lower edge plate of the semi-finished product; the first positioning block for the lower edge plate of the semi-finished product is fixed on the base, and the first positioning block for the lower edge plate of the semi-finished product has a lower edge plate positioning surface that contacts the radial end face of the lower edge plate of the double low-pressure turbine guide vane semi-finished product. A preset height difference is provided between the upper edge plate positioning surface and the lower edge plate positioning surface, which is used to ensure that the center plane of the double low-pressure turbine guide vane semi-finished product is parallel to the upper surface of the base after clamping the double low-pressure turbine guide vane semi-finished product; the first clamping assembly for the lower edge plate of the semi-finished product includes a lower edge plate positioning block for the semi-finished product. The lower edge plate consists of a first pressure plate, a second locking bolt, and a pad. The pad is fixed to the base. One end of the first pressure plate of the semi-finished lower edge plate abuts against the pad, and the other end of the first pressure plate of the semi-finished lower edge plate abuts against the lower edge plate of the double low-pressure turbine guide vane semi-finished product. The first pressure plate of the semi-finished lower edge plate is provided with a second slotted hole. The second locking bolt passes through the second slotted hole and is threadedly connected to the pad, which is used to force the first pressure plate of the semi-finished lower edge plate to press against the lower edge plate of the double low-pressure turbine guide vane semi-finished product, so as to clamp the lower edge plate of the low-pressure turbine guide vane by the first positioning block of the semi-finished lower edge plate and the first pressure plate of the semi-finished lower edge plate.

[0014] Further, the Y-axis positioning device includes a second positioning block for the upper edge plate of the semi-finished product, a second positioning block for the lower edge plate of the semi-finished product, and a second clamping assembly for the lower edge plate of the semi-finished product; both the second positioning blocks for the upper edge plate and the lower edge plate are fixed to the base, the second positioning block for the upper edge plate abuts against the radial end face of the upper edge plate, and the second positioning block for the lower edge plate abuts against the radial end face of the lower edge plate; the second clamping assembly for the lower edge plate includes a second pressure plate and a third locking bolt for the lower edge plate. One end of the second pressure plate abuts against the pad block, and the other end of the second pressure plate of the semi-finished product lower edge plate abuts against the radial end face of the lower edge plate of the double low-pressure turbine guide vane semi-finished product. The second pressure plate of the semi-finished product lower edge plate is provided with a third strip hole. The third locking bolt passes through the third strip hole and is threadedly connected to the pad block. This is used to force the second pressure plate of the semi-finished product lower edge plate to press against the radial end face of the lower edge plate of the double low-pressure turbine guide vane semi-finished product, so as to clamp the lower edge plate of the double low-pressure turbine guide vane semi-finished product through the second positioning block of the semi-finished product lower edge plate and the second pressure plate of the semi-finished product lower edge plate.

[0015] Furthermore, the thin-walled baffle includes a front thin-walled baffle and a rear thin-walled baffle; The lower edge plate includes an upper connecting plate, a web plate, and a lower connecting plate; the upper connecting plate is connected to the blade body of the low-pressure turbine guide vane; the lower connecting plate is connected to the upper connecting plate through the web plate and forms an H-shaped structure; one end of the lower connecting plate facing the leading edge of the low-pressure turbine guide vane is welded to the front thin-walled baffle, and one end of the lower connecting plate facing the trailing edge of the low-pressure turbine guide vane is welded to the rear thin-walled baffle.

[0016] Compared with the prior art, the beneficial effects of this invention are: This invention utilizes paired tooling for positioning to ensure the relative positional accuracy of the inner flow channel surfaces of two single-section blades. This ensures that the steps and overall undulations of the inner flow channel surfaces of the two blades meet design requirements after welding, achieving a smooth transition of the airflow channel and avoiding unnecessary losses during airflow. Simultaneously, the paired tooling can provide stable constraints on the blades during welding, reducing the impact of welding deformation on the blade surface accuracy. This effectively improves the welding preparation accuracy and product qualification rate of large twin-section low-pressure turbine guide blades, and reduces manufacturing and processing costs. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the welding and fabrication method for the guide vanes of a large gas turbine low-pressure turbine in this embodiment. Figure 2 This is a schematic diagram of the back radial end face and exhaust side end face of the upper and lower edge plates of the single-stage low-pressure turbine guide vane in the embodiment. Figure 3 This is a schematic diagram of the radial end face of the upper and lower edge plates of the single-stage low-pressure turbine guide vane in the embodiment. Figure 4 This is a schematic diagram of the radial end face of the upper and lower edge plates of the double low-pressure turbine guide vanes in the embodiment. Figure 5 This is a schematic diagram of the intake side end face of the upper and lower edge plates of the dual low-pressure turbine guide vanes in the embodiment; Figure 6 This is a schematic diagram of the exhaust edge end face of the upper and lower edge plates of the dual low-pressure turbine guide vanes in the embodiment; Figure 7 This is a schematic diagram of the upper inner flow channel surface of the upper and lower edge plates of the double low-pressure turbine guide vanes in the embodiment. Figure 8 This is a schematic diagram of the weld overlay surface of the lower edge plate of the dual low-pressure turbine guide vane in the embodiment; Figure 9 This is a schematic diagram of the milling fixture in the embodiment; Figure 10 This is a front view schematic diagram of the milling fixture in the embodiment; Figure 11 This is a top view of the milling fixture in the embodiment; Figure 12 This is a schematic diagram of the structure of the mating tooling in the embodiment; Figure 13 This is a front view schematic diagram of the milling fixture clamping the blade in the embodiment; Figure 14 This is a rear view schematic diagram of the milling fixture clamping the blade in the embodiment; Figure 15 This is a top view of the milling fixture clamping the blade in the embodiment; Figure 16 This is a schematic diagram of the alignment process using a jig after the front and rear thin-walled baffles of the low-pressure turbine guide vanes are welded in the embodiment. Figure 17 This is a schematic diagram of the fixture structure used for correcting the thin-walled baffle in the embodiment; Figure 18 This is a schematic diagram of the fixture structure used for correcting the thin-walled baffle in the embodiment; Figure 19 This is a schematic diagram of the finished double-unit low-pressure turbine guide vanes in the embodiment; Among them, 11-upper edge plate, 12-lower edge plate, 13-upper connecting plate, 14-web plate, 15-lower connecting plate, 16-front thin-walled baffle, 17-rear thin-walled baffle, 18-honeycomb, 21-base, 22-semi-finished product inner flow channel surface positioning component, 23-positioning top column, 24-first positioning block of semi-finished product upper edge plate, 25-semi-finished product upper edge plate pressure plate, 26-first locking bolt, 27-first positioning block of semi-finished product lower edge plate, 28-first pressure plate of semi-finished product lower edge plate, 29-second locking bolt, 30-pad, 31-semi-finished product 32-Finished upper edge plate second positioning block, 33-Semi-finished lower edge plate second positioning block, 34-Semi-finished lower edge plate second pressure plate, 35-Third locking bolt, 46-Semi-finished upper edge plate ejector pin, 47-Base, 48-Upper edge plate first positioning block, 49-Upper edge plate pressure plate, 50-First support block, 60-Second support block, 41-Inner flow channel surface positioning ejector pin, 41-Upper edge plate second positioning block, 42-Upper edge plate second positioning block, 43-First support block, 44-Lower edge plate first positioning block, 45-Lower edge plate pressure plate, 46-Second support block, 47-Inner flow channel surface positioning ejector pin, 48-Upper edge plate second positioning block, 49-Lower edge plate second positioning block, 50-Pressure clamp, 60-Gesture. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0019] See Figure 1 This invention provides a method for welding and manufacturing guide vanes for low-pressure turbines of large gas turbines, used to weld two single low-pressure turbine guide vanes into a double low-pressure turbine guide vane, comprising the following steps: The brazing surface and the clamping and positioning surface are respectively ground on the upper edge plate 11 and lower edge plate 12 of the two single-stage low-pressure turbine guide vanes; the clamping and positioning surface includes the basin radial end face and the exhaust side end face of the lower edge plate 12, and the brazing surface is the back radial end face of the lower edge plate 12. According to the design position relationship of the low-pressure turbine guide vanes, two single low-pressure turbine guide vanes are paired and welded together using matching tooling to obtain a double low-pressure turbine guide vane semi-finished product. Thin-walled baffles and honeycomb 18 are welded onto the lower edge plate 12 of the semi-finished twin low-pressure turbine guide vane to obtain the finished twin low-pressure turbine guide vane.

[0020] This invention utilizes paired tooling for positioning to ensure the relative positional accuracy of the inner flow channel surfaces of two single-section blades. This ensures that the steps and overall undulations of the inner flow channel surfaces of the two blades meet design requirements after welding, achieving a smooth transition of the airflow channel and avoiding unnecessary losses during airflow. Simultaneously, the paired tooling can provide stable constraints on the blades during welding, reducing the impact of welding deformation on the blade surface accuracy. This effectively improves the welding preparation accuracy and product qualification rate of large twin-section low-pressure turbine guide blades, and reduces manufacturing and processing costs.

[0021] Example This embodiment further elaborates on the welding and fabrication method of the guide vanes for low-pressure turbines of large gas turbines, as detailed below.

[0022] See Figures 1 to 18 A method for welding and fabricating guide vanes for low-pressure turbines of large gas turbines, used to weld two single low-pressure turbine guide vanes into a double low-pressure turbine guide vane, includes the following steps: Step 1: Grind the surfaces to be brazed and the clamping and positioning surfaces on the upper edge plate 11 and lower edge plate 12 of the two single-stage low-pressure turbine guide vanes, respectively. For one of the single-stage low-pressure turbine guide vanes, the clamping and positioning surfaces include the basin radial surface, the exhaust edge end face, and the upper inner flow channel surface on the upper edge plate 11 and lower edge plate 12, and the surfaces to be brazed are the back radial surfaces of the upper edge plate 11 and lower edge plate 12 of the single-stage low-pressure turbine guide vane; for the other single-stage low-pressure turbine guide vane, the clamping and positioning surfaces include the back radial surface and the exhaust edge end face on the upper edge plate 11 and lower edge plate 12, and the surfaces to be brazed are the basin radial end faces of the upper edge plate 11 and lower edge plate 12 of the single-stage low-pressure turbine guide vane.

[0023] Specifically, this step involves grinding two single-unit low-pressure turbine guide vanes: the two single-unit low-pressure turbine guide vanes are divided into a left low-pressure turbine guide vane and a right low-pressure turbine guide vane. On both the left and right low-pressure turbine guide vanes, the end faces of the upper edge plate 11 and lower edge plate 12 of the blank material have a allowance of 1.5mm. The surfaces to be brazed and the reference surfaces need to be machined separately for use in the subsequent machining of the double-unit low-pressure turbine guide vane semi-finished product. When machining the left low-pressure turbine guide vane, firstly, a high-powered grinding machine is used to machine the radial end face dimension of the basin, leaving a 1mm allowance, which will be used as the subsequent clamping and positioning surface; then, a high-powered grinding machine is used to machine the exhaust edge end face dimension, leaving a 1mm allowance, which will also be used as the subsequent clamping and positioning surface; finally, a high-powered grinding machine is used to machine the back radial end face dimension, machining to the finished size, for subsequent brazing.

[0024] When machining the right guide vane of the low-pressure turbine, the radial end face of the basin is first machined to the finished size using a high-power grinding machine for subsequent brazing; then the exhaust side end face is machined to the size using a high-power grinding machine, with a machining allowance of 1mm, for subsequent clamping and positioning; finally, the back radial end face is machined to the size using a high-power grinding machine, with a machining allowance of 1mm, for subsequent clamping and positioning.

[0025] Step 2: According to the design positional relationship of the low-pressure turbine guide vanes, use a pairing fixture to pair and weld the two single-unit low-pressure turbine guide vanes together to obtain a semi-finished double-unit low-pressure turbine guide vane. On the semi-finished double-unit low-pressure turbine guide vane, the radial end face, upper inner flow channel surface, exhaust side end face, and intake side end face of the upper edge plate 11 and lower edge plate 12 are as follows... Figures 4 to 8 As shown.

[0026] The specific implementation steps are as follows: Low-pressure turbine guide vane inner flow channel surface undulation control pairing: One low-pressure turbine guide vane (left) and one low-pressure turbine guide vane (right) processed in step 1 are used. The blades, back radial end faces, and inner flow channel surfaces of the ground low-pressure turbine guide vanes (left and right) are then paired on a pairing fixture. The pairing fixture is as follows: Figures 12 to 15 As shown, during pairing, a feeler gauge is used to measure the height difference between the upper inner flow channel edges and the lower inner flow channel edges of the two blades. If both the upper and lower inner flow channel edge height differences are not greater than 0.15 mm, the low-pressure turbine guide left blade and the low-pressure turbine guide right blade are successfully paired. If the height difference between the upper and / or lower inner flow channel edges is greater than 0.15 mm, the upper and lower inner flow channel surfaces of the two blades are machined until the 0.15 mm requirement is met, thus completing the blade pairing. After pairing, the sequence numbers of the paired low-pressure turbine guide left blade and low-pressure turbine guide right blade are recorded, and they are brazed together to form a semi-finished twin low-pressure turbine guide blade. It should be noted that the upper inner flow channel surface refers to the wall surface where the upper edge plate 11 connects to the blade body, and the lower inner flow channel surface refers to the wall surface where the lower edge plate 12 connects to the blade body.

[0027] Step 3: Machining the upper edge plate 11 and lower edge plate 12 of the semi-finished twin low-pressure turbine guide vane to ensure that the dimensions of each end face of the upper edge plate 11 and lower edge plate 12 meet the design tolerance requirements. After obtaining the semi-finished twin low-pressure turbine guide vane, if there are defects in the weld overlay wear-resistant layer on the radial surface of the lower edge plate 12, the semi-finished twin low-pressure turbine guide vane is clamped on a milling fixture, and the existing weld overlay wear-resistant layer on the radial surface of the lower edge plate 12 is removed according to a preset number of passes and a preset feed rate per pass, and then the weld overlay wear-resistant layer is repaired by welding.

[0028] This step specifically involves a three-stage progressive milling process for the wear-resistant layer welded onto the radial surface of the lower edge plate: For the semi-finished twin-tube low-pressure turbine guide vane obtained in step 2, if quality issues arise with the wear-resistant layer welded onto the radial end face of the lower edge plate 12 after the machining process is completed, re-welding is permitted. However, before re-welding, the semi-finished twin-tube low-pressure turbine guide vane needs to be clamped onto a milling fixture, and the existing wear-resistant layer welded onto the radial end face of the lower edge plate needs to be completely removed using milling, thus creating conditions for re-welding. The milling fixture is as follows: Figures 9 to 11 As shown, during the milling process before welding repair, the depth dimension of the weld repair area in the inlet and outlet directions is 70 ± 0.2 mm on the radial end face (limit dimension 69.8 mm ~ 70.2 mm) and 67 mm ± 0.2 mm on the back radial end face (limit dimension 67.2 mm ~ 66.8 mm), with high tolerance accuracy of only 0.4 ± 0.2 mm. Based on this, this embodiment distributes the tolerance to three milling operations, with the depth dimension increasing progressively with each operation to ensure complete removal of the existing weld overlay wear-resistant layer, leaving no weld overlay wear-resistant layer residue. Specifically, after clamping and positioning the semi-finished twin low-pressure turbine guide vanes using milling fixtures, for the radial end face of the lower edge plate 12: after the first gradual milling of the wear-resistant layer on the radial end face of the basin, the depth is 69.8~69.85mm; after the second gradual milling of the wear-resistant layer on the radial end face of the basin, the depth is 69.97~70.02mm, which is 0.12~0.22mm deeper than the first milling; after the third gradual milling of the wear-resistant layer on the radial end face of the basin, the depth is 70.14~70.2mm, which is 0.12~0.23mm deeper than the second milling. For the radial end face of the lower edge plate 12: After the first gradual milling of the wear-resistant layer on the radial end face, the depth is 67.2~67.15mm; after the second gradual milling of the wear-resistant layer on the radial end face, the depth is 67.02~66.97mm, an increase of 0.13~0.23mm from the first milling; after the third gradual milling of the wear-resistant layer on the radial end face, the depth is 66.86~66.8mm, an increase of 0.11~0.22mm from the second milling. This three-step progressive milling method, with a progressive increase in depth of 0.11~0.23mm, ensures complete removal of the existing weld overlay wear-resistant layer, leaving no weld overlay wear-resistant layer residue. This provides a good surface condition for subsequent repair welding, ensuring the quality of the blade after repair welding.

[0029] Step 4: Weld thin-walled baffles and honeycomb onto the lower edge plate 12 of the semi-finished twin low-pressure turbine guide vane to obtain the finished twin low-pressure turbine guide vane, as shown below. Figures 16 to 18 .

[0030] The thin-walled baffle includes a front thin-walled baffle 16 and a rear thin-walled baffle 17; the lower edge plate 12 includes an upper connecting plate 13, a web plate 14, and a lower connecting plate 15; the upper connecting plate 13 is connected to the blade body of the low-pressure turbine guide vane; the lower connecting plate 15 is connected to the upper connecting plate 13 through the web plate 14, forming an H-shaped structure; one end of the lower connecting plate 15 facing the leading edge of the low-pressure turbine guide vane is welded to the front thin-walled baffle 16, and one end of the lower connecting plate 15 facing the trailing edge of the low-pressure turbine guide vane is welded to the rear thin-walled baffle 17. In this step, the front thin-walled baffle 16 and the rear thin-walled baffle 17 are brazed onto the lower edge plate 12 of the semi-finished double low-pressure turbine guide vane, and the honeycomb 18 is simultaneously welded to the arc-shaped end face of the lower edge plate 12 to obtain the finished double low-pressure turbine guide vane. Figure 19 .

[0031] Furthermore, since both the front thin-walled baffle 16 and the rear thin-walled baffle 17 are thin-sheet structures, they are prone to deformation after brazing. Therefore, in this embodiment, a jig 6 is used to correct the front thin-walled baffle 16 and the rear thin-walled baffle 17. Specifically, if the front thin-walled baffle 16 and the rear thin-walled baffle 17 deform and shrink, and the measured value of dimension L1 between the front thin-walled baffle 16 and the upper connecting plate 13, and the measured value of dimension L2 between the rear thin-walled baffle 17 and the upper connecting plate 13 are smaller than the design value, then an enlarging correction jig is inserted between the front thin-walled baffle 16 and the upper connecting plate 13, and between the rear thin-walled baffle 17 and the upper connecting plate 13. The enlarging correction jig enlarges dimensions L1 and L2 to achieve correction. If the measured values ​​of dimensions L1 and L2 are larger than the design value, a shrinkage correction jig is inserted to support the brazed front thin-walled baffle. Then, a force is applied in the opposite direction of deformation, and the jig shrinks the dimensions to achieve correction.

[0032] In this embodiment, the mating fixture mentioned in step 2 includes a base 40, an x-axis positioning device, a y-axis positioning device, and a z-axis positioning device, such as... Figures 12 to 15 As shown. The base 40 is a horizontally placed square plate. The upper surface of the base 40 is the xy plane, one corner of the base 40 is the origin, the direction along the blade height of the low-pressure turbine guide blade is the x-axis, the direction perpendicular to the blade height is the y-axis in the xy plane, and the direction of the xy plane is the z-axis, thus establishing a three-dimensional xyz coordinate system.

[0033] Furthermore, such as Figures 12 to 15As shown, the z-axis positioning device includes an upper edge plate first positioning block 41 and two upper edge plate clamping assemblies, as well as a lower edge plate first positioning block 44 and a lower edge plate first clamping assembly. The upper edge plate first positioning block 41 is fixed on the base 40, and the upper edge plate first positioning block 41 has an upper edge plate positioning surface that contacts the radial end face of the upper edge plate 11 of the low-pressure turbine guide vane. The lower edge plate first positioning block 44 is fixed on the base 40, and the lower edge plate first positioning block 44 has a lower edge plate positioning surface that contacts the radial end face of the lower edge plate 12 of the low-pressure turbine guide vane. A preset height difference is provided between the upper edge plate positioning surface and the lower edge plate positioning surface to ensure that the center plane of the low-pressure turbine guide vane is horizontal after the low-pressure turbine guide vane is clamped. The two upper edge plate clamping assemblies have the same structure and correspond to a low-pressure turbine guide vane. Each upper edge plate clamping assembly includes an upper edge plate clamping plate 42, a locking bolt, and a first support block 43. The first support block 43 is fixed on the base 40. One end of the upper edge plate clamping plate 42 abuts against the first support block 43, and the other end of the upper edge plate clamping plate 42 abuts against the upper edge plate 11 of the low-pressure turbine guide vane. The upper edge plate clamping plate 42 is provided with a strip hole. The locking bolt passes through the strip hole and is threaded to the first support block 43. When the locking bolt is loosened, the upper edge plate clamping plate 42 can rotate around the locking bolt or slide along the length of the strip hole. The lower edge plate first clamping assembly includes a lower edge plate clamping plate 45, a locking bolt, and a second support block 46. The second support block 46 is fixed on the base 40. Two lower edge plate clamping plates 45 are provided and both are connected to the second support block 46. Each lower edge plate clamping plate 45 corresponds to one low-pressure turbine guide vane. One end of each lower edge plate clamping plate 45 abuts against the second support block 46, and the other end abuts against the lower edge plate 12 of the low-pressure turbine guide vane. Each lower edge plate clamping plate 45 is provided with a strip-shaped hole. The locking bolt passes through the strip-shaped hole and is threadedly connected to the second support block 46. When the locking bolt is loosened, the lower edge plate clamping plate 45 can rotate around the locking bolt or slide along the length of the strip-shaped hole. In this embodiment, tightening the locking bolts forces the upper edge plate pressure plate 42 to press against the upper edge plate 11 of the low-pressure turbine guide vane, thereby clamping the upper edge plate 11 of the low-pressure turbine guide vane by the first positioning block 41 of the upper edge plate and the upper edge plate pressure plate 42. At the same time, tightening the locking bolts forces the lower edge plate pressure plate 45 to press against the lower edge plate 12 of the low-pressure turbine guide vane, thereby clamping the lower edge plate 12 of the low-pressure turbine guide vane by the first positioning block 44 of the lower edge plate and the lower edge plate pressure plate 45, thus fixing the low-pressure turbine guide vane on the base 40 and achieving positioning in the z-axis direction.

[0034] Furthermore, the x-axis positioning device includes two inner flow channel surface positioning pins 47 fixed on the base 40, with each inner flow channel surface positioning pin 47 corresponding to one low-pressure turbine guide vane. When clamping the low-pressure turbine guide vane, the tip of the inner flow channel surface positioning pin 47 abuts against the inner flow channel surface of the upper edge plate 11 to achieve positioning in the x-axis direction.

[0035] Furthermore, the y-axis positioning device includes an upper edge plate second positioning block 48, a lower edge plate second positioning block 49, and a clamping device 50. Both the upper edge plate second positioning block 48 and the lower edge plate second positioning block 49 are fixed to the base 40. When clamping the low-pressure turbine guide vane, the radial end face of the upper edge plate 11 abuts against the upper edge plate second positioning block 48, and the radial end face of the lower edge plate 12 abuts against the lower edge plate second positioning block 49. The clamping device 50 is disposed on the base 40 and is used to apply a force to the blade basin of one of the low-pressure turbine guide vanes after the two single-unit low-pressure turbine guide vanes are combined and placed on the tooling, causing the two single-unit low-pressure turbine guide vanes to press against the upper edge plate second positioning block 48 and the lower edge plate second positioning block 49, thereby achieving positioning in the y-axis direction.

[0036] When clamping two single-unit low-pressure turbine guide vanes, loosen the upper edge plate pressure plate 42, the lower edge plate pressure plate 45, and the clamping device 50. Then, place the radial end face of the upper edge plate 11 of the low-pressure turbine guide vane on the first positioning block 41 of the upper edge plate, and place the radial end face of the lower edge plate 12 of the low-pressure turbine guide vane on the first positioning block 44 of the lower edge plate. Then, make the inner flow channel surface of the upper edge plate 11 abut against the tip of the positioning pin 47 of the inner flow channel surface. Then, use the clamping device 50 to apply force to the blade basin of one of the low-pressure turbine guide vanes, so that the two single-unit low-pressure turbine guide vanes abut against the second positioning block 48 of the upper edge plate and the second positioning block 49 of the lower edge plate. Finally, make the upper edge plate pressure plate 42 press the upper edge plate 11 and the lower edge plate pressure plate 45 press the lower edge plate 12 to achieve the positioning and clamping of the two single-unit low-pressure turbine guide vanes for pairing.

[0037] The milling fixture includes a base 21, an X-axis positioning device, a Y-axis positioning device, and a Z-axis positioning device. Specifically, as shown... Figures 9 to 11 The base 21 is a square plate with a preset tilt angle relative to the horizontal plane. The upper surface of the base 21 is defined as the XY plane. With one corner of the base 21 as the origin, the direction along the blade height of the low-pressure turbine guide blade is the X-axis direction. In the XY plane, the direction perpendicular to the blade height direction is the Y-axis direction, and the direction perpendicular to the XY plane is the Z-axis direction, thus establishing an XYZ three-dimensional coordinate system.

[0038] Furthermore, the Z-axis positioning device includes a first positioning block 24 for the upper edge plate of the semi-finished product and a pressing assembly for the upper edge plate of the semi-finished product, as well as a first positioning block 27 for the lower edge plate of the semi-finished product and a first pressing assembly for the lower edge plate of the semi-finished product. The first positioning block 24 for the upper edge plate of the semi-finished product is fixed on the base 21, and the first positioning block 24 for the upper edge plate of the semi-finished product has an upper edge plate positioning surface that contacts the radial end face of the basin of the upper edge plate 11 of the semi-finished product of the double low-pressure turbine guide vane. The first positioning block 27 for the lower edge plate of the semi-finished product is fixed on the base 21, and the first positioning block 27 for the lower edge plate of the semi-finished product has a lower edge plate positioning surface that contacts the radial end face of the basin of the lower edge plate of the semi-finished product of the double low-pressure turbine guide vane. There is a preset height difference between the upper edge plate positioning surface and the lower edge plate positioning surface, which is used to make the center plane of the semi-finished product of the double low-pressure turbine guide vane parallel to the upper surface of the base 21 after clamping the semi-finished product of the double low-pressure turbine guide vane. The semi-finished product upper edge plate clamping assembly includes a semi-finished product upper edge plate clamping plate 25 and a first locking bolt 26. One end of the semi-finished product upper edge plate clamping plate 25 is connected to the base 21, and the other end of the semi-finished product upper edge plate clamping plate 25 abuts against the upper edge plate 11 of the double low-pressure turbine guide vane semi-finished product. The semi-finished product upper edge plate clamping plate 25 is provided with a first strip hole, and the first locking bolt 26 passes through the first strip hole and is threadedly connected to the base 21. The semi-finished product lower edge plate first clamping assembly includes a semi-finished product lower edge plate first clamping plate 28, a second locking bolt 29, and a pad 30. The pad 30 is fixed on the base 21. One end of the semi-finished product lower edge plate first clamping plate 28 abuts against the pad 30, and the other end of the semi-finished product lower edge plate first clamping plate 28 abuts against the lower edge plate of the double low-pressure turbine guide vane semi-finished product. The semi-finished product lower edge plate first clamping plate 28 is provided with a second strip hole, and the second locking bolt 29 passes through the second strip hole and is threadedly connected to the pad 30. In this embodiment, tightening the first locking bolt 26 forces the upper edge plate pressure plate 25 of the semi-finished product to press against the upper edge plate 11 of the double low-pressure turbine guide vane semi-finished product, thereby clamping the upper edge plate 11 of the double low-pressure turbine guide vane semi-finished product through the first positioning block 24 and the upper edge plate pressure plate 25 of the semi-finished product; at the same time, the second locking bolt 29 forces the lower edge plate pressure plate 28 of the semi-finished product to press against the lower edge plate 12 of the double low-pressure turbine guide vane semi-finished product, thereby clamping the lower edge plate 12 of the double low-pressure turbine guide vane semi-finished product through the first positioning block 27 and the first pressure plate 28 of the lower edge plate of the semi-finished product, thus fixing the double low-pressure turbine guide vane semi-finished product on the base 21 and achieving positioning in the Z-axis direction.

[0039] Furthermore, the X-axis positioning device includes a semi-finished product inner flow channel surface positioning component 22 fixed on the base 21. A positioning top post 23 is provided on the semi-finished product inner flow channel surface positioning component 22. When clamping the semi-finished product of the double low-pressure turbine guide vane, the tip of the positioning top post 23 abuts against the inner flow channel surface of the upper edge plate 11 to achieve positioning in the X-axis direction.

[0040] Furthermore, the Y-axis positioning device includes a second positioning block 31 for the upper edge plate of the semi-finished product, a second positioning block 32 for the lower edge plate of the semi-finished product, a pin 35 for the upper edge plate of the semi-finished product, and a second clamping assembly for the lower edge plate of the semi-finished product. Both the second positioning block 31 and the second positioning block 32 for the upper edge plate of the semi-finished product are fixed to the base 21. When clamping the semi-finished double-section low-pressure turbine guide vane, the radial end face of the upper edge plate 11 abuts against the second positioning block 31 for the upper edge plate of the semi-finished product, and the radial end face of the lower edge plate 12 abuts against the second positioning block 32 for the lower edge plate of the semi-finished product. The pin 35 for the upper edge plate of the semi-finished product is threaded onto the positioning component 22 of the inner flow channel surface of the semi-finished product, and is used to apply pressure to the exhaust side end face of the upper edge plate 11 of the semi-finished product, so that the intake side end face of the upper edge plate 11 of the semi-finished product abuts against the second positioning block 31 for the upper edge plate of the semi-finished product. The second clamping assembly for the lower edge plate of the semi-finished product includes a second pressure plate 33 for the lower edge plate of the semi-finished product and a third locking bolt 34. One end of the second pressure plate 33 abuts against the pad 30, and the other end of the second pressure plate 33 abuts against the radial end face of the lower edge plate 12 in the semi-finished product of the double low-pressure turbine guide vane. The second pressure plate 33 of the semi-finished product is provided with a third strip hole. The third locking bolt 34 passes through the third strip hole and is threadedly connected to the pad 30. By tightening the third locking bolt 34, the second pressure plate 33 of the lower edge plate of the semi-finished product is forced to press against the radial end face of the lower edge plate 12 in the semi-finished product of the double low-pressure turbine guide vane. The lower edge plate 12 in the semi-finished product of the double low-pressure turbine guide vane is clamped by the second positioning block 32 and the second pressure plate 33 of the lower edge plate of the semi-finished product, thereby achieving positioning in the Y-axis direction.

[0041] When clamping the semi-finished twin low-pressure turbine guide vanes, loosen the upper edge plate pressure plate 25, the first pressure plate 28, and the second pressure plate 33 of the lower edge plate. Then, place the inlet side end face of the upper edge plate 11 of the semi-finished twin low-pressure turbine guide vane on the first positioning block 24 of the upper edge plate, and place the inlet side end face of the lower edge plate 12 of the semi-finished twin low-pressure turbine guide vane on the first positioning block 27 of the lower edge plate. Then, make the inner flow channel surface of the upper edge plate 11 abut against the tip of the positioning top post 23. Finally, make the upper edge plate pressure plate 25 press the upper edge plate 11, and make the first pressure plate 28 and the second pressure plate 33 of the lower edge plate press the lower edge plate 12 to achieve the positioning and clamping of the semi-finished twin low-pressure turbine guide vane, so as to facilitate the grinding of the defective welded wear-resistant layer on the radial surface of the lower edge plate 12.

[0042] This invention utilizes a pairing fixture to achieve high-quality pairing of two low-pressure turbine guide vanes simply and quickly, solving the problem of uncontrollable undulations in the inner flow channel surface between two low-pressure turbine guide vanes in existing technologies. This invention quantitatively measures the height difference between the upper and lower flow channel surfaces using the pairing fixture, and then selects and records the pairing sequence number before brazing. Compared to the traditional experience-based selection method, this method eliminates the need for complex testing equipment, is simple and quick to operate, and effectively ensures a smooth transition of the inner flow channel surface in the finished twin low-pressure turbine guide vanes, improving consistency and aerodynamic performance.

[0043] This invention employs a milling fixture to clamp semi-finished double-section low-pressure turbine guide vanes. Through a three-stage progressive milling process on the radial surface of the lower edge plate to deposit a wear-resistant layer, it achieves the high precision required by the design, rationally allocates machining allowance, and completely removes the wear-resistant layer, creating favorable conditions for subsequent welding. This solves the problems of strict tolerances and difficulty in ensuring complete removal of solder in a single milling operation when depositing the wear-resistant layer on the radial surface of the lower edge plate in existing technologies. This invention distributes the total tolerance of 0.4mm across three progressive milling steps, removing solder gradually in each step. Compared to the traditional single-milling method, this avoids solder residue or over-cutting of the substrate, ensuring a clean and dimensionally precise surface, providing an ideal surface for subsequent welding, and significantly reducing the scrap rate.

[0044] This invention utilizes a jig to correct the dimensions of the thin-walled baffles before and after welding, even after obtaining a brazed complete body. This simple and quick method overcomes brazing deformation and solves the problem in existing technologies where the thin-walled baffles on the guide vanes of twin low-pressure turbines are prone to deformation after welding and are difficult to correct. The invention employs either an enlarged or contracted correction jig, applying insertion and reverse force to precisely correct critical dimensions to within tolerance range. Compared to traditional disassembly or scrapping methods, it eliminates the need for re-welding, is simple and quick to operate, and offers high correction accuracy, significantly improving repair efficiency and dimensional stability.

[0045] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for welding two single low pressure turbine guide vanes into a double low pressure turbine guide vane for a large gas turbine, characterized in that Includes the following steps: The surfaces to be brazed and the clamping and positioning surfaces are ground on the upper edge plate (11) and lower edge plate (12) of the two single-stage low-pressure turbine guide vanes, respectively. According to the design position relationship of the low-pressure turbine guide vanes, two single low-pressure turbine guide vanes are paired and welded together using matching tooling to obtain a double low-pressure turbine guide vane semi-finished product. Thin-walled baffles and honeycomb (18) are welded onto the lower edge plate (12) of the semi-finished twin low-pressure turbine guide vane to obtain the finished twin low-pressure turbine guide vane.

2. The method for welding and preparing guide vanes for low-pressure turbines of large gas turbines according to claim 1, characterized in that, Also includes: After obtaining the semi-finished product of the double low-pressure turbine guide vane, if there is a defect in the weld overlay wear-resistant layer on the radial surface of the lower edge plate (12) of the semi-finished product of the double low-pressure turbine guide vane, the semi-finished product of the double low-pressure turbine guide vane is clamped on a milling fixture, and the existing weld overlay wear-resistant layer on the radial surface of the lower edge plate (12) is removed by milling according to the preset number of passes and the preset feed amount for each pass, and then the weld overlay wear-resistant layer is repaired by welding.

3. The method of claim 1, wherein the method further comprises: After two single-unit low-pressure turbine guide vanes are paired and clamped on the pairing fixture, the height difference between the upper inner flow channel edge and the lower inner flow channel edge is measured. If the height difference between the upper inner flow channel edge and the lower inner flow channel edge is not greater than a preset threshold, the two single-unit low-pressure turbine guide vanes are welded into a double-unit low-pressure turbine guide vane semi-finished product. Otherwise, the two single-unit low-pressure turbine guide vanes are processed and re-measured until a double-unit low-pressure turbine guide vane semi-finished product is obtained.

4. The method of claim 2, wherein the method further comprises: The milling fixture includes a base (21), an X-axis positioning device, a Y-axis positioning device, and a Z-axis positioning device; the X-axis positioning device, the Y-axis positioning device, and the Z-axis positioning device are all installed on the base (21) and are used to position the semi-finished product of the double low-pressure turbine guide vane on the base (21) along the X-axis, Y-axis, and Z-axis directions after clamping the semi-finished product of the double low-pressure turbine guide vane.

5. The method of claim 4, wherein the method further comprises: The X-axis positioning device includes a semi-finished inner flow channel surface positioning component (22); the inner flow channel surface positioning component is fixed on the base (21), and the semi-finished inner flow channel surface positioning component (22) is provided with a positioning top post (23), the tip of the positioning top post (23) abuts against the inner flow channel surface of the upper edge plate (11) of the low-pressure turbine guide vane.

6. The method of claim 5, wherein the method further comprises: The Z-axis positioning device includes a first positioning block (24) for the upper edge plate of the semi-finished product and a clamping assembly for the upper edge plate of the semi-finished product; the first positioning block (24) for the upper edge plate of the semi-finished product is fixed on the base (21), and the first positioning block (24) for the upper edge plate of the semi-finished product is provided with an upper edge plate positioning surface that contacts the radial end face of the upper edge plate (11) of the low-pressure turbine guide vane; the clamping assembly for the upper edge plate of the semi-finished product includes a pressure plate (25) for the upper edge plate of the semi-finished product and a first locking bolt (26), one end of the pressure plate (25) for the upper edge plate of the semi-finished product is connected to the base (21), and the semi-finished product... The other end of the upper edge plate pressure plate (25) abuts against the upper edge plate (11) of the double low-pressure turbine guide vane semi-finished product, and the upper edge plate pressure plate (25) of the semi-finished product is provided with a first strip hole. The first locking bolt (26) passes through the first strip hole and is threadedly connected to the base (21) to force the upper edge plate pressure plate (25) of the semi-finished product to press the upper edge plate (11) of the double low-pressure turbine guide vane semi-finished product, so as to clamp the upper edge plate (11) of the low-pressure turbine guide vane through the first positioning block (24) of the upper edge plate and the upper edge plate pressure plate (25) of the semi-finished product.

7. The method of claim 6, wherein the method further comprises: The Z-axis positioning device further includes a first positioning block (27) for the lower edge plate of the semi-finished product and a first clamping assembly for the lower edge plate of the semi-finished product; the first positioning block (27) for the lower edge plate of the semi-finished product is fixed on the base (21), and the first positioning block (27) for the lower edge plate of the semi-finished product is provided with a lower edge plate positioning surface that contacts the radial end face of the lower edge plate of the double low-pressure turbine guide vane semi-finished product. A preset height difference is provided between the upper edge plate positioning surface and the lower edge plate positioning surface, which is used to make the center plane of the double low-pressure turbine guide vane semi-finished product parallel to the upper surface of the base (21) after clamping the double low-pressure turbine guide vane semi-finished product; the first clamping assembly for the lower edge plate of the semi-finished product includes a first pressure plate (28) for the lower edge plate of the semi-finished product, a second locking bolt (29) and a pad (30). The pad (30) is fixed on the base (21). One end of the first pressure plate (28) of the semi-finished product lower edge plate abuts against the pad (30), and the other end of the first pressure plate (28) of the semi-finished product lower edge plate abuts against the lower edge plate of the double low-pressure turbine guide vane semi-finished product. The first pressure plate (28) of the semi-finished product lower edge plate is provided with a second strip hole. The second locking bolt (29) passes through the second strip hole and is threadedly connected to the pad (30) to force the first pressure plate (28) of the semi-finished product lower edge plate to press the lower edge plate (12) of the double low-pressure turbine guide vane semi-finished product, so as to clamp the lower edge plate (12) of the double low-pressure turbine guide vane semi-finished product through the first positioning block (27) of the semi-finished product lower edge plate and the first pressure plate (28) of the semi-finished product lower edge plate.

8. The method of claim 7, wherein the method further comprises: The Y-axis positioning device includes a second positioning block (31) for the upper edge plate of the semi-finished product, a second positioning block (32) for the lower edge plate of the semi-finished product, and a second clamping assembly for the lower edge plate of the semi-finished product; both the second positioning block (31) for the upper edge plate of the semi-finished product and the second positioning block (32) for the lower edge plate of the semi-finished product are fixed to the base (21), the second positioning block (31) for the upper edge plate of the semi-finished product abuts against the radial end face of the upper edge plate (11), and the second positioning block (32) for the lower edge plate of the semi-finished product abuts against the radial end face of the lower edge plate (12); the second clamping assembly for the lower edge plate of the semi-finished product includes a second clamping plate (33) for the lower edge plate of the semi-finished product and a third locking bolt (34), the second positioning block (31) for the upper ... of the semi-finished product. One end of the second pressure plate (33) of the edge plate abuts against the pad (30), and the other end of the second pressure plate (33) of the semi-finished product lower edge plate abuts against the radial end face of the lower edge plate of the double low-pressure turbine guide vane semi-finished product. The second pressure plate (33) of the semi-finished product lower edge plate is provided with a third strip hole. The third locking bolt (34) passes through the third strip hole and is threadedly connected to the pad (30) to force the second pressure plate (33) of the semi-finished product lower edge plate to press against the radial end face of the lower edge plate of the double low-pressure turbine guide vane semi-finished product, so as to clamp the lower edge plate of the double low-pressure turbine guide vane semi-finished product by the second positioning block (32) of the semi-finished product lower edge plate and the second pressure plate (33) of the semi-finished product lower edge plate.

9. The method of claim 1 wherein the large gas turbine low pressure turbine guide vane is welded. The thin-walled baffle includes a front thin-walled baffle (16) and a rear thin-walled baffle (17); The lower edge plate (12) includes an upper connecting plate (13), a web plate (14), and a lower connecting plate (15); the upper connecting plate (13) is connected to the blade body of the low-pressure turbine guide vane; the lower connecting plate (15) is connected to the upper connecting plate (13) through the web plate (14) and forms an H-shaped structure; one end of the lower connecting plate (15) facing the leading edge of the low-pressure turbine guide vane is welded to the front thin-walled baffle (16), and one end of the lower connecting plate (15) facing the trailing edge of the low-pressure turbine guide vane is welded to the rear thin-walled baffle (17).

Images