A variable straightening fixture for cast steam turbine straight-welded stationary blades

Abstract

This invention discloses a variable straightening fixture for cast steam turbine straight-welded stationary blades, belonging to the technical field of steam turbine blade casting fixtures. This invention aims to solve the problems of poor versatility, low precision, and easy damage to workpieces in existing straightening fixtures. This fixture includes a fixture base, an adjustable positioning clamping assembly, a multi-directional variable straightening positioning system, and a limit protection assembly. The fixture base is a base plate with adjustable holes. The adjustable positioning clamping assembly includes a fixed block whose position can be adjusted along the base plate. The multi-directional variable straightening positioning system includes replaceable upper and lower movable blocks that cooperate with the fixed block, with a clearance allowance at the part that conforms to the curved surface of the blade. Through its modular and adjustable structural design, this invention can adapt to various specifications of straight-welded stationary blades, achieving high-precision, low-damage straightening of blade deformation. It has the advantages of strong versatility, high straightening efficiency, and high product qualification rate, and is suitable for batch straightening processes of cast straight-welded stationary blades for various thermal power, nuclear power, and industrial steam turbines.

Description

Technical Field

[0001] This invention belongs to the technical field of tooling for the forming stage of steam turbine blade castings. Specifically, it relates to a special variable tooling for deformation correction after casting straight welded stationary blades of steam turbines. It is mainly used in the deformation correction, dimensional calibration and precision repair processes after casting straight welded stationary blades of medium and large steam turbines. Background Technology

[0002] Cast straight-welded stationary blades are core power-generating components of steam turbines, typically formed using precision investment casting. During production, due to wax pattern shrinkage, mold shell expansion, molten steel shrinkage, and residual casting stress, deformation problems such as blade profile bending, edge warping, and positioning surface misalignment are prone to occur, directly affecting the stability of blade machining accuracy.

[0003] Currently, blade straightening in the industry mostly adopts fixed mold straightening, manual tapping straightening, or simple top-pressing tooling straightening methods. Among them, fixed molds have extremely poor versatility, only suitable for blades of a single specification. For straight welded stationary blades of different sizes and curvatures, multiple sets of molds need to be customized, resulting in high production costs and low changeover efficiency. Manual straightening relies on the operator's experience, and it is difficult to control the straightening force and precision, which easily leads to problems such as over-straightening, under-straightening, and damage to the blade surface, resulting in low product qualification rates. Conventional simple tooling has a fixed structure and cannot adapt to the fine deformation straightening of blades at multiple angles and points, making it difficult to meet the processing standards of high-precision steam turbine blades. At the same time, the straightening process has poor stability and is prone to secondary deformation, which seriously restricts the mass production and high-precision processing of steam turbine stationary blades. Summary of the Invention

[0004] The present invention aims to solve the technical defects of existing technologies, such as poor versatility, low correction accuracy, and easy damage to workpieces, and provides a variable correction tooling for cast steam turbine direct-welded stationary blades, which can realize adaptive and precise correction of blades of various specifications.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A variable straightening fixture for cast steam turbine straight-welded stationary blades, characterized in that it comprises: The tooling base serves as the overall load-bearing structure; An adjustable positioning clamping assembly is adjustablely disposed at both ends of the tooling base, used to adaptively adjust the clamping spacing according to the blade length, so as to quickly clamp and fix cast straight welded stationary blades of different specifications. A multi-directional variable correction and positioning system includes replaceable or adjustable movable blocks that cooperate with the adjustable positioning clamping assembly, used for precise point-to-point, quantitative, and directional correction of different deformation areas of the blade; and The limiting and protective component has a curved limiting and protective structure designed to fit the irregular curved surface of the blade, which is used to evenly distribute pressure and protect the blade surface during the correction process.

[0006] Preferably, the tooling base is a base plate with multiple bottom adjustment holes along its length for bolting to the adjustable positioning clamping assembly, thereby adjusting its clamping distance.

[0007] Preferably, the adjustable positioning clamping assembly includes two fixing blocks, each of which is detachably fixed to the bottom adjustment hole on the base plate by a bottom bolt and a nut.

[0008] Preferably, the multi-directional variable correction and positioning system includes a lower block at the small end, a lower block at the large end, an upper block at the small end, and an upper block at the large end, wherein: The small end lower block and the large end lower block are respectively installed in the two fixed blocks through a matching slot, and are used to support the back of the blade from below; The small end upper block and the large end upper block are respectively fixed above the two fixing blocks by top bolts, which are used to press the blade's leaf basin part from above.

[0009] Preferably, the fixing block is provided with multiple sets of top adjustment holes for connecting top bolts, and the top adjustment holes and top bolts are used to install large end blocks and small end blocks of different sizes.

[0010] Preferably, the limiting and protective assembly includes a curved surface structure disposed on the upper small end block, the upper large end block, the lower small end block, and the lower large end block, at the point where it contacts the blade profile, wherein: The curved surfaces of the upper small end block and the upper large end block are recessed by 1.5~2.0mm relative to the leaf base area, and the curved surfaces of the lower small end block and the lower large end block are recessed by 3.0~5.0mm relative to the back of the leaf.

[0011] Preferably, the curved surface structure of the limiting and protective component is further provided with an elastic contact pad.

[0012] Preferably, the upper small end block, upper large end block, lower small end block, and lower large end block are all made of forged aluminum; the fixing block is made of 45 steel; the base plate is made of P20 material; the groove clearance between the fixing block and the lower small end block and the lower large end block is 3.0mm; the bolt holes on the base plate for installing the two fixing blocks are spaced 440±0.1mm apart in the length direction and 186±0.1mm apart in the width direction; the base plate also has 18 adjustable holes with a diameter of 23~29mm; the thickness of the upper small end block and the upper large end block is ≥30mm; the external width of the lower small end block and the lower large end block is 230~310mm.

[0013] The present invention also provides a method for straightening cast steam turbine straight-welded stationary blades using the above-mentioned tooling, comprising the following steps: S1) Tooling preset and adjustment: Based on the theoretical length and profile data of the blade to be corrected, select and install the corresponding lower positioning block and upper pressure block; adjust the distance between the two fixing block units on the tooling base so that the blade is inserted and its two ends protrude from the fixing block by a predetermined distance. S2) Blade positioning and pre-clamping: Insert the lower positioning block into the slot of the fixing block unit; place the blade to be corrected on the contoured surface of the lower positioning block for initial alignment; S3) Full clamping and alignment: Install the upper pressure block and use fasteners to initially lock it, so that the blade is gently clamped between the upper pressure block and the lower positioning block; by tapping the blade or finely adjusting the position of the lower positioning block in the slot, ensure that the blade body is in uniform contact with the contoured surface, and after the steam inlet and steam outlet edges of the blade are parallel to the tooling reference surface or meet the preset angle, fully lock the fasteners. S4) Gradual force application correction: Place the tool with the clamped blades in the center of the press table; start the press and slowly and steadily press the pressure head vertically down onto the upper pressure block; the force application process adopts a step-by-step loading method, first loading to 50%-70% of the predetermined correction force, holding the pressure for 10-30 seconds, and observing the pressure gauge reading and the blade condition; if there is no abnormality, continue loading to 100% of the predetermined correction force and hold the pressure for 30-60 seconds; S5) Unloading and stress relaxation: After the corrective force is maintained, control the press head to release the pressure at a uniform speed and slowly; after the pressure is released, keep the blade in the clamped state in the tooling for 5-15 minutes to release elastic deformation and reduce stress rebound. S6) Unloading and Inspection: Loosen the fasteners of the upper pressure block, remove the upper pressure block, and take out the corrected blade; use an inspection template or a coordinate measuring machine to inspect the blade profile, torsion angle and key dimensions, and record the correction effect.

[0014] Preferably, the following steps are also included: S7) Iterative correction: If the accuracy requirements are not fully met after the first correction, the installation position of the lower positioning block or the upper pressure block can be finely adjusted according to the test results. By using the slot gap or selecting positioning / pressure blocks with different clearance values, repeat steps S3 to S6 to perform localized and precise correction.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1) Highly versatile and significantly reduces costs: The tooling of this invention breaks through the limitations of traditional fixed tooling that adapts to a single specification. Through a multi-directional variable adjustment structure (adjustable base plate, replaceable upper and lower blocks), it can adapt to various models and sizes of cast steam turbine direct-welded stationary blades. No special molds are required, which greatly reduces the tooling manufacturing cost and shortens the product changeover and debugging cycle.

[0016] 2) Precise Correction for Guaranteed Accuracy: Employing a progressive fine-tuning movable block correction method allows for precise control and repair of blade casting deformation and residual casting deformation. This effectively solves the problems of poor accuracy and uneven correction associated with manual correction, ensuring significantly improved blade dimensional accuracy and surface finish. Combined with the aforementioned progressive, step-by-step loading correction method, it enables more precise control of the material's plastic deformation process, effectively repairing casting deformation and residual stress deformation, significantly improving blade dimensional accuracy and surface finish, and exhibiting good repeatability.

[0017] 3) Comprehensive protection to prevent damage: Equipped with a dedicated curved surface limiting and protective structure, it conforms to the irregular curved surface design of the blade and is made of forged aluminum. This evenly distributes the straightening pressure, preventing surface damage and scratches caused by hard contact between the tooling and the blade. It also effectively suppresses stress rebound during the straightening process, eliminating secondary deformation. Combined with the pressure holding and static placement steps in the straightening method, this further promotes stress homogenization, effectively suppressing straightening rebound and preventing secondary deformation.

[0018] 4) Convenient operation and improved efficiency: The tooling is easy to clamp and adjust, and can quickly complete the entire process of blade positioning, fine-tuning and correction, and positioning and locking, reducing the difficulty of manual operation, greatly improving the efficiency of blade correction and processing, and adapting to industrial mass production. Attached Figure Description

[0019] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a front structural diagram of the straightening fixture in an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the top surface structure of the straightening fixture in an embodiment of the present invention.

[0022] Figure 3 This is a three-dimensional structural diagram of the straightening fixture in an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the top adjustment hole and elastic contact pad structure in an embodiment of the present invention.

[0024] In the diagram: 1-base plate; 2-fixing block; 3-lower small end block; 4-upper small end block; 5-lower large end block; 6-upper large end block; 7, 8-bolts; 9-bolts; 10-nuts; 11-bottom adjustment hole; 12-top adjustment hole; 13-elastic contact pad. Detailed Implementation

[0025] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0026] The present invention will now be described in detail with reference to the accompanying drawings.

[0027] Example 1: Tooling Structure Example This embodiment provides a variable straightening fixture for cast steam turbine straight-welded stationary blades, the specific structure of which is as follows: Please see Figures 1 to 4 This fixture includes a base plate 1, two fixing blocks 2, a small end lower block 3, a small end upper block 4, a large end lower block 5, a large end upper block 6, and multiple bolts and nuts.

[0028] Base plate 1: Serving as the base for the tooling, it is made of P20 mold steel and has external dimensions of 1220*600*60mm. Multiple sets of bolt holes are provided on its top surface, specifically including 18 adjustable holes with diameters of 23~29mm, and holes for precisely positioning the fixing blocks, with a length spacing of 440±0.1mm and a width spacing of 186±0.1mm.

[0029] Two fixing blocks 2: Made of 45 steel, with external dimensions of 263*505*77mm. Each fixing block is equipped with a vertical slot and a horizontal bolt hole. The two fixing blocks are fixed to the corresponding adjustment hole positions on the base plate 1 using bottom bolts 7 and 8 and nuts 10, according to the length of the blade to be corrected. After fixing, ensure that the blade end face protrudes at a distance of ≥10mm to facilitate the correction operation.

[0030] Small-end lower block 3 and large-end lower block 5: Made of forged aluminum, they support the blade back from below. Their upper surfaces have curved surfaces designed according to the curvature of the blade back. To prevent damage, these curved surfaces are recessed by 3.0~5.0mm relative to the theoretical blade profile. Their bottoms have raised slots that fit with slots on the fixing block 2 with a clearance of 3.0mm to ensure smooth insertion and stable positioning. The width of these two lower blocks is selected within the range of 230~310mm depending on the blade size. In this embodiment, the small-end lower block 3 is 230mm wide, and the large-end lower block 5 is 310mm wide.

[0031] Small end upper block 4 and large end upper block 6: Also made of forged aluminum, they are used to press the blade's blade head from above. Their lower surfaces have curved surfaces designed according to the curvature of the blade's blade head, recessed by 1.5~2.0mm relative to the theoretical blade profile; in this embodiment, 1.8mm is used. To ensure sufficient strength to resist deformation during pressurization, their thickness is designed to be ≥30mm; in this embodiment, 35mm is used. They are fixed to the top of the two fixing blocks 2 respectively using #9 bolts.

[0032] Specifically, the curved surface structure of the limiting and protective component is also provided with an elastic contact pad 13, which can be made of silicone or rubber material, to further buffer pressure, prevent slippage, and make the pressure distribution more uniform. In addition, the fixing block 2 is provided with multiple sets of top adjustment holes 12 for connecting top bolts 9. The top adjustment holes 12 and the top bolts 9 are used to install the large end upper block 6 and the small end upper block 4 of different sizes.

[0033] It should be noted that the contoured curved surface with a specific clearance, composed of a lower positioning block and an upper pressure block made of forged aluminum, together form the limiting and protective component of this invention. The hardness of forged aluminum is much lower than that of cast blade material, and it has good plasticity, which can effectively protect the blade profile during correction; while the precise contoured curved surface and clearance design constitute a multi-directional variable correction and positioning system, ensuring uniform pressure distribution.

[0034] Example 2: Correction Method Example This embodiment, in conjunction with the above-mentioned tooling, takes a straight-welded stationary blade of a certain type of steam turbine with slight bending deformation in the middle as an example to explain in detail the correction method of the present invention.

[0035] Step S1: Tooling preset and adjustment. Measure the theoretical length of the blade as 850mm. Select the corresponding adjustment hole 101 on the base plate 1, and use bolts 7 and 8 and nuts 10 to initially fix the two fixing blocks 2, with a preset spacing of 860mm to allow the ends to protrude. Select forged aluminum lower positioning blocks 3 and 5 and upper pressure blocks 4 and 6 that match the blade profile data.

[0036] Step S2: Blade positioning and pre-clamping. Place the lower positioning blocks 3 and 5 into the slot 201 of the fixing block 2. Place the blade to be corrected stably on the contoured surface of the lower positioning blocks 3 and 5, visually inspecting that the blade back and the contoured surface are basically in contact.

[0037] Step S3: Full clamping and alignment. Install pressure blocks 4 and 6, and screw in bolt 9 but do not tighten it yet. Gently tap the ends and middle of the blade with a rubber mallet, while observing the contact gap between the blade and the upper and lower contoured surfaces. Use a feeler gauge to check and ensure that the parallelism error between the blade's steam inlet edge length direction and the preset reference line on the base plate 1 is less than 0.1 mm / m. Then, tighten bolt 9 diagonally in two steps to the specified torque.

[0038] Step S4: Gradual Force Application and Correction. Move the fixture to the center of the 500-ton hydraulic press. Set the target correction pressure to 200 tons, calculated based on the blade cross-section and deformation. First, control the pressure head to press down, slowly loading to 70% of 140 tons, holding the pressure for 15 seconds until the pressure gauge remains stable without dropping. Then, continue loading to 200 tons, holding the pressure for 45 seconds. Step S5: Unloading and Stress Relaxation. After holding the pressure, slowly depressurize to zero at a rate of 5mm per minute. After depressurization, keep the fixture locked and let it stand for 10 minutes.

[0039] Step S6: Unloading and Inspection. Loosen and remove bolt 9 and upper pressure blocks 4 and 6, and carefully remove the blade. Using the theoretical model of the blade, test it on a three-dimensional measuring machine. The results show that the maximum bending deformation in the middle has been reduced from 2.3mm before correction to 0.15mm, the profile is qualified, and there are no indentations or scratches on the surface.

[0040] Step S7: Iterative Correction. In this example, the requirement is met with a single correction, without the need for iteration. If the local profile still exceeds the tolerance, the bolt 9 can be slightly loosened, and the angle or position of the lower positioning block 3 or 5 can be finely adjusted within the 3mm gap range of the slot 201, and a small force value can be used for supplementary correction again.

[0041] It should be noted that, through the combination of the above structure and method, this tooling achieves efficient, high-precision, and non-destructive correction of straight-welded stationary blades of different lengths and surface curvatures, greatly improving production efficiency and product qualification rate.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A variable straightening fixture for cast steam turbine straight-welded stationary blades, characterized in that, include: Tooling base (1) serves as the overall load-bearing structure; An adjustable positioning clamping assembly is adjustablely disposed at both ends of the tooling base (1) for adaptively adjusting the clamping spacing according to the blade length, so as to quickly clamp and fix cast straight welded stationary blades of different specifications. The multi-directional variable correction and positioning system includes a replaceable or adjustable movable block that cooperates with the adjustable positioning clamping assembly, for precise point-to-point, quantitative, and directional correction of different deformation areas of the blade. as well as The limiting and protective component has a curved limiting and protective structure designed to fit the irregular curved surface of the blade, which is used to evenly distribute pressure and protect the blade surface during the correction process.

2. The variable straightening fixture for cast steam turbine straight-welded stationary blades according to claim 1, characterized in that, The tooling base (1) is a base plate with multiple bottom adjustment holes (11) along its length direction for bolting to the adjustable positioning clamping assembly, thereby adjusting its clamping distance.

3. The variable straightening fixture for cast steam turbine straight-welded stationary blades according to claim 2, characterized in that, The adjustable positioning clamping assembly includes two fixing blocks (2), each of which is detachably fixed to the bottom adjustment hole (11) on the base plate (1) by bottom bolts (7, 8) and nuts (10).

4. The variable straightening fixture for cast steam turbine straight-welded stationary blades according to claim 3, characterized in that, The multi-directional variable correction and positioning system includes a small-end lower block (3), a large-end lower block (5), a small-end upper block (4), and a large-end upper block (6), wherein: The small end lower block (3) and the large end lower block (5) are respectively installed in the two fixed blocks (2) through matching slots, and are used to support the back of the blade from below; The small end upper block (4) and the large end upper block (6) are respectively fixed above the two fixing blocks (2) by top bolts (9) to press the blade basin part from above.

5. The variable straightening fixture for cast steam turbine straight-welded stationary blades according to claim 4, characterized in that, The fixing block (2) is provided with multiple sets of top adjustment holes (12) for connecting top bolts (9). The top adjustment holes (12) and top bolts (9) are used to install large end blocks (6) and small end blocks (4) of different sizes.

6. The variable straightening fixture for cast steam turbine straight-welded stationary blades according to claim 5, characterized in that, The limiting and protective assembly includes a curved surface structure disposed on the upper small end block (4), upper large end block (6), lower small end block (3), and lower large end block (5) at the contact point with the blade profile, wherein: The curved surfaces of the small end upper block (4) and the large end upper block (6) are recessed by 1.5~2.0mm relative to the leaf base area, and the curved surfaces of the small end lower block (3) and the large end lower block (5) are recessed by 3.0~5.0mm relative to the leaf back area.

7. The variable straightening fixture for cast steam turbine straight-welded stationary blades according to claim 6, characterized in that, The curved surface of the limiting and protective component is also provided with an elastic contact pad (13).

8. The variable straightening fixture for cast steam turbine straight-welded stationary blades according to claim 7, characterized in that, The small end upper block (4), large end upper block (6), small end lower block (3) and large end lower block (5) are all made of forged aluminum; the fixing block (2) is made of 45 steel; the base plate (1) is made of P20 material. The slot clearance between the fixing block (2) and the small end lower block (3) and the large end lower block (5) is 3.0 mm. The bolt holes on the base plate (1) for installing the two fixing blocks (2) are spaced 440±0.1 mm in length and 186±0.1 mm in width. The base plate (1) is also provided with 18 adjustable holes with a diameter of 23~29 mm. The thickness of the small end upper block (4) and the large end upper block (6) is ≥30 mm. The outer width of the small end lower block (3) and the large end lower block (5) is 230~310 mm.

9. A method for straightening cast steam turbine straight-welded stationary blades using the variable straightening fixture for any one of claims 1 to 8, characterized in that, Includes the following steps: S1) Tooling preset and adjustment: Based on the theoretical length and profile data of the blade to be corrected, select and install the corresponding lower positioning block and upper pressure block; adjust the distance between the two fixing block units on the tooling base so that the blade is inserted and its two ends protrude from the fixing block by a predetermined distance. S2) Blade positioning and pre-clamping: Insert the lower positioning block into the slot of the fixed block unit; Place the leaf to be corrected on the contoured surface of the lower positioning block for initial alignment; S3) Full clamping and alignment: Install the upper pressure block and use fasteners to initially lock it, so that the blade is gently clamped between the upper pressure block and the lower positioning block; by tapping the blade or finely adjusting the position of the lower positioning block in the slot, ensure that the blade body is in uniform contact with the contoured surface, and after the steam inlet and steam outlet edges of the blade are parallel to the tooling reference surface or meet the preset angle, fully lock the fasteners. S4) Gradual force application correction: Place the tool with the clamped blades in the center of the press table; start the press and slowly and steadily press the pressure head vertically down onto the upper pressure block; the force application process adopts a step-by-step loading method, first loading to 50%-70% of the predetermined correction force, holding the pressure for 10-30 seconds, and observing the pressure gauge reading and the blade condition; if there is no abnormality, continue loading to 100% of the predetermined correction force and hold the pressure for 30-60 seconds; S5) Unloading and stress relaxation: After the corrective force is maintained, control the press head to release the pressure at a uniform speed and slowly; after the pressure is released, keep the blade in the clamped state in the tooling for 5-15 minutes to release elastic deformation and reduce stress rebound. S6) Unloading and Inspection: Loosen the fasteners of the upper pressure block, remove the upper pressure block, and take out the corrected blade; use an inspection template or a coordinate measuring machine to inspect the blade profile, torsion angle and key dimensions, and record the correction effect.

10. The correction method according to claim 9, characterized in that, It also includes the following steps: S7) Iterative correction: If the accuracy requirements are not fully met after the first correction, the installation position of the lower positioning block or the upper pressure block can be finely adjusted according to the test results. By using the slot gap or selecting positioning / pressure blocks with different clearance values, repeat steps S3 to S6 to perform localized and precise correction.

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