A method for welding repair of a rectifier vane

Abstract

A rectifier blade welding repair method, comprising the following steps: step S1: based on the finite element method, a thermal coupling numerical model of the rectifier welding process is established, and a heat source model of argon arc welding and laser welding is established; step S2: setting the argon arc welding numerical simulation parameters and the laser welding numerical simulation parameters, respectively adopting the argon arc welding and the laser welding mode to carry out numerical simulation welding on the rectifier; step S3: comparing the temperature field at the moment of welding completion, the residual stress field after welding and the residual axial deformation after welding by using the two welding modes; step S4: according to the comparison result in step S3, the suitable welding mode is determined; step S5: through the actual welding test, the feasibility of the suitable welding mode determined in step S4 is verified; step S6: if the feasibility verification in step S5 is passed, the rectifier is clamped by using the welding tooling, and the blade to be welded is welded on the outer ring by using the welding mode determined in step S4.

Description

Technical Field

[0001] This invention relates to the field of aero-engine repair technology, and in particular to a method for welding repair of rectifier blades. Background Technology

[0002] Aero-engine blades operate under harsh environments of high temperature, high pressure, and high speed for extended periods, making them highly susceptible to damage. Welding repair of blades is a critical technology in aero-engine maintenance and repair. Because welding is a localized, unsteady-state thermal process, repairing a single blade can lead to a series of problems, including a decrease in the overall dimensional and positional accuracy of the engine stator and rotor, and deterioration of their microstructure and properties. Researching welding repair processes for engine blades is of great significance for improving the level of aero-engine maintenance technology.

[0003] like Figure 1 The diagram shows the structure of a rectifier and the welding area of ​​the blades to be welded. The rectifier consists of an outer ring 1 and multiple blades brazed together. During operation, blade damage and cracking are prone to occur. To reduce engine repair costs, welding repair of the rectifier is essential. Currently, the commonly used welding methods for blades include laser welding and argon arc welding. During repair, the joint between the blade 2 and the outer ring 1 is a butt joint with a locking base. Weld A must be located on the back side of the outer ring 1, and the warping variation of the rectifier's front and rear ends before welding must not exceed 0.1 mm.

[0004] Due to the special geometry of the rectifier's outer ring 1 and the high requirements for fit between them, and especially the difficulty in controlling the weld penetration (the base material thickness at the weld joint is over 3.5mm), achieving sufficient penetration requires relatively large parameters or a slow welding speed. This would significantly impact the thermal impact on the entire semi-ring and hinder deformation control. Therefore, determining the welding method and the appropriate welding technique are pressing issues that need to be addressed. Summary of the Invention

[0005] The main objective of this invention is to propose a welding repair method for rectifier blades, aiming to solve the aforementioned technical problems.

[0006] To achieve the above objectives, this invention proposes a method for welding repair of rectifier blades, comprising the following steps:

[0007] Step S1: Establish a thermo-mechanical coupling numerical model of the rectifier welding process based on the finite element method, and establish heat source models for argon arc welding and laser welding;

[0008] Step S2: Set the numerical simulation parameters for argon arc welding and laser welding, and perform numerical simulation welding on the rectifier using argon arc welding and laser welding methods respectively;

[0009] Step S3: Compare the temperature field, residual stress field, and residual axial deformation at the instant of welding completion using the two welding methods;

[0010] Step S4: Based on the comparison results in step S3, determine the appropriate welding method;

[0011] Step S5: Verify the feasibility of the suitable welding method determined in Step S4 through actual welding tests;

[0012] Step S6: If the feasibility verification in step S5 is successful, the rectifier is clamped using a welding fixture, and the blade (2) to be welded is welded onto the outer ring (1) using the welding method determined in step S4.

[0013] Preferably, the thermo-mechanical coupling numerical model established in step S1 is as follows:

[0014] ;

[0015] in: r Density, unit: kg / m³ 3 ;

[0016] C p This is the heat capacity at constant pressure, expressed in J / (kg·K).

[0017] T Temperature, in Kelvin (K).

[0018] t Time, in seconds;

[0019] l x for x Thermal conductivity in the directional direction, expressed in W / (m·K);

[0020] l y for y Thermal conductivity in the directional direction, expressed in W / (m·K);

[0021] l z for z Thermal conductivity in the directional direction, expressed in W / (m·K);

[0022] Q arc Heat generated by the welding heat source, unit: W / m 3 ,

[0023] ;

[0024] in: qc Heat loss due to convective heat transfer at the workpiece surface, expressed in W / m². 2 ;

[0025] h c The convective heat transfer coefficient is expressed in W / (m³). 2 ·K);

[0026] T s The surface temperature of the workpiece is expressed in Kelvin (K).

[0027] T 0 The ambient air temperature, in Kelvin (K).

[0028] ;

[0029] in, Q c This represents the total radiative heat loss from the workpiece surface, expressed in W.

[0030] A The total surface area of ​​the welded workpiece, in meters (m²). 2 ,

[0031] ;

[0032] in, q r The heat loss due to radiation from the workpiece surface is expressed in W / m². 2 ;

[0033] e Emissivity of the workpiece surface;

[0034] s It is the Stefan-Boltzmann constant;

[0035] F The shape factor of the workpiece surface.

[0036] ;

[0037] in, Q r This represents the total convective heat loss on the workpiece surface, expressed in W.

[0038] A The total surface area of ​​the welded workpiece, in meters (m²). 2 ,

[0039] ;

[0040] Wherein, the left side of the equal sign represents the strain rate of the workpiece during the fusion welding process;

[0041] The first term on the right side of the equation is the elastic strain rate;

[0042] The second term is the plastic strain rate;

[0043] The third item is thermal strain rate;

[0044] The fourth item is the creep strain rate;

[0045] The fifth item is the phase transition strain rate.

[0046] ;

[0047] in, α This is the coefficient of thermal expansion, with units of 1 / K;

[0048] Ṫ This is the rate of temperature change, expressed in K / s.

[0049] d ij for kroneckerd function,

[0050] ;

[0051] in, n The Poisson's ratio of the material;

[0052] E This refers to the elastic modulus of the material, expressed in Pa.

[0053] l This is the scaling factor;

[0054] s ij For Cauchy stress tensor;

[0055] s kk It is the sum of the three normal stresses in the Cauchy stress tensor.

[0056] Preferably, in step S1, the argon arc welding uses a double ellipsoidal heat source, the heat source model of which is:

[0057] ;

[0058] ;

[0059] in, Q The power of the welding arc is expressed in watts (W).

[0060] a , b , c For the shape parameters of the double ellipsoid;

[0061] f 1 and f 2 Let be the heat distribution function of the front and rear ellipsoids. f 1 + f 2 =2.

[0062] Preferably, in step S1, the laser welding uses a conical heat source, the heat source model of which is:

[0063] ;

[0064] in, The volumetric heat flux density of the cone-shaped heat source;

[0065] η is the efficiency value;

[0066] P It is the energy of the laser beam, measured in J;

[0067] z e and z i These are the maximum and minimum values ​​in the Z direction, respectively, in mm;

[0068] r e and r i These are the maximum and minimum radii, in mm;

[0069] r It is a radius function with respect to x and y. r The radial distance from the central axis of the heat source is r. 2 = x 2 + y 2 .

[0070] Preferably, in step S1, when establishing the thermo-coupling numerical model, it is necessary to consider the influence of the two blades adjacent to the blade to be welded (2), use full tetrahedral Tet elements, take an average element size of 0.5 mm, and connect the blade to be welded and the outer ring model by adhesive contact.

[0071] Preferably, in step S2: the numerical simulation parameters for argon arc welding are: current 30A, voltage 10V, welding speed 60mm / min, and thermal efficiency 0.75; the numerical simulation parameters for laser welding are: laser power 600W, defocusing amount 10mm, welding speed 600mm / min, and thermal efficiency 0.86.

[0072] Preferably, in step S4, laser welding is selected as the welding method; in step S5, when verifying the feasibility of the laser welding method, the laser welding system used includes: a JPT 4KW fiber laser with a fiber diameter of 100µm; a KUKA six-axis linkage robot with a positioning accuracy of 0.1mm; and a HIGHYAG laser head.

[0073] Preferably, in step S6, the welding fixture includes two side support plates arranged at intervals and a top block disposed between the two side support plates; arc-shaped grooves are respectively provided on the inner surfaces of the two side support plates, which are used to engage the two sides of the outer ring; a tightening screw is provided on the top block, and the top end of the tightening screw is used to tighten against the inner side of the edge plate of the blade to be welded; the two side support plates are connected by bolts.

[0074] Preferably, a U-shaped groove for heat dissipation is provided in the upper middle part of the side support plate, and a heat dissipation cover is installed on the U-shaped groove; the heat dissipation cover is made of aluminum alloy.

[0075] Preferably, a stop bar is provided at the bottom of the U-shaped groove, and a slot is provided at the lower part of the heat dissipation cover plate. When the heat dissipation cover plate is assembled, the slot is engaged with the stop bar, and the two heat dissipation cover plates are fastened to the U-shaped groove of the side support plate by C-clamps.

[0076] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0077] (1) In this invention, a thermo-mechanical coupling numerical model of the rectifier welding process is established, as well as heat source models for argon arc welding and laser welding. Numerical simulation welding of the rectifier is performed, and a suitable welding method is selected after comparison. The feasibility of using laser welding for rectifier repair is fully demonstrated through numerical simulation and actual welding tests, and a radial welding repair method for rectifier blades is established. For argon arc welding simulation, the double ellipsoidal heat source model used abstracts the heat input in the welding process into two ellipsoidal heat sources. Its heat flux density distribution exhibits non-uniform and non-linear characteristics with spatial position, which can well reflect the characteristics of short head and long tail of the molten pool, and can also reflect the energy distribution of the heat source in the plate thickness direction. In argon arc welding simulation, the double ellipsoidal heat source can capture the local characteristics of the weld joint, thus more accurately reflecting the temperature distribution and morphological evolution of the heat-affected zone in the welding process. At the same time, the model can accurately analyze the stress and deformation behavior in the welding process, which helps to predict the performance and reliability of the weld joint. For laser welding simulation, a conical heat source is used to abstract the heat input during the laser welding process into a conical heat source. Its energy density distribution exhibits spatial non-uniformity and non-linearity, enabling it to effectively simulate the thermal history of the weld, the morphological evolution of the heat-affected zone (HAZ), and the dynamic changes of the molten pool. Furthermore, this heat source model can more accurately reveal the temperature gradient, residual stress distribution, and deformation behavior during laser welding, thus providing strong support for evaluating the performance and reliability of welded joints. The thermo-mechanical coupled numerical model combines heat conduction and mechanical response, accurately simulating and predicting temperature distribution, stress distribution, deformation behavior, and the morphological evolution of the HAZ during the welding process. This is significant for predicting the comprehensive performance of welded joints, such as residual stress, deformation, crack tendency, and the size of the HAZ, providing a reliable method for welding process optimization.

[0078] (2) In this invention, the welding fixture structure is simple, with few parts, and is easy to process, assemble and maintain; the arc-shaped groove on the side support plate is used to install the two sides of the outer ring to ensure the axial position accuracy of the outer ring; the front of the blade to be welded is tightened with a pre-tightening force in the radial direction, which is convenient and simple to clamp; by setting a U-shaped groove on the side support plate, the heat dissipation cover plate is used to dissipate heat during welding, which can reduce welding deformation and warping. Attached Figure Description

[0079] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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 the structures shown in these drawings without creative effort.

[0080] Figure 1 This is a schematic diagram of the structure of a rectifier and the welding area of ​​the blades to be welded.

[0081] Figure 2 Schematic diagrams of heat sources for argon arc welding and laser welding;

[0082] Figure 3 The mesh model of the blade to be welded and the two adjacent blades is used to establish the thermo-coupling numerical model.

[0083] Figure 4 The temperature field comparison diagrams at the moment of welding completion are used for numerical simulation, where (a) is the front of the argon arc welding, (b) is the back of the argon arc welding, (c) is the front of the laser welding, and (d) is the back of the laser welding.

[0084] Figure 5 The images show a comparison of residual stress fields after welding, as simulated numerically. (a) is the front side of the TIG weld, (b) is the back side of the TIG weld, (c) is the front side of the laser weld, and (d) is the back side of the laser weld.

[0085] Figure 6 The images show a comparison of residual axial deformation after numerical simulation welding, where (a) is the side of the argon arc weld, (b) is the back of the argon arc weld, (c) is the side of the laser weld, and (d) is the back of the laser weld.

[0086] Figure 7 This is an exploded view of the welding fixture in this invention;

[0087] Figure 8 This is a schematic diagram of the welding fixture in this invention;

[0088] Figure 9 This is a schematic diagram of the welding fixture used in this invention for welding the rectifier after clamping it.

[0089] The reference numerals in the attached diagrams are as follows: 1. Outer ring; 2. Blade to be repaired; 3. Side support plate; 3a. Arc-shaped groove; 3b. Square groove; 3c. Stop bar; 3d. U-shaped groove; 4. Top block; 5. Small fixing screw; 6. Large fixing screw; 7. Large nut; 8. Heat dissipation cover plate; 8a. Groove; 9. Tightening screw; 10. Small nut; A. Weld seam. Detailed Implementation

[0090] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0091] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0092] A method for welding repair of rectifier blades includes the following steps:

[0093] Step S1: Establish a thermo-mechanical coupling numerical model of the rectifier welding process based on the finite element method, and establish heat source models for argon arc welding and laser welding;

[0094] Step S2: Set the numerical simulation parameters for argon arc welding and laser welding, and perform numerical simulation welding on the rectifier using argon arc welding and laser welding methods respectively;

[0095] Step S3: Compare the temperature field, residual stress field, and residual axial deformation at the instant of welding completion using the two welding methods;

[0096] Step S4: Based on the comparison results in step S3, determine the appropriate welding method;

[0097] Step S5: Verify the feasibility of the suitable welding method determined in Step S4 through actual welding tests;

[0098] Step S6: If the feasibility verification in step S5 is successful, the rectifier is clamped using a welding fixture, and the blade 2 to be welded is welded onto the outer ring 1 using the welding method determined in step S4.

[0099] In step S1, the established thermo-mechanical coupling numerical model is as follows:

[0100] ;

[0101] in: r Density, unit: kg / m³ 3 ;

[0102] C p This is the heat capacity at constant pressure, expressed in J / (kg·K).

[0103] T Temperature, in Kelvin (K).

[0104] t Time, in seconds;

[0105] l x for x Thermal conductivity in the directional direction, expressed in W / (m·K);

[0106] l y for y Thermal conductivity in the directional direction, expressed in W / (m·K);

[0107] l z for z Thermal conductivity in the directional direction, expressed in W / (m·K);

[0108] Q arc Heat generated by the welding heat source, unit: W / m 3 ,

[0109] ;

[0110] in: q c Heat loss due to convective heat transfer at the workpiece surface, expressed in W / m². 2 ;

[0111] h c The convective heat transfer coefficient is expressed in W / (m³). 2 ·K);

[0112] T s The surface temperature of the workpiece is expressed in Kelvin (K).

[0113] T 0 The ambient air temperature, in Kelvin (K).

[0114] ;

[0115] in, Q c This represents the total convective heat loss on the workpiece surface, expressed in W.

[0116] A The total surface area of ​​the welded workpiece, in meters (m²). 2 ,

[0117] ;

[0118] in, q r The heat loss due to radiation from the workpiece surface is expressed in W / m². 2 ;

[0119] e Emissivity of the workpiece surface;

[0120] s It is the Stefan-Boltzmann constant;

[0121] F The shape factor of the workpiece surface.

[0122] ;

[0123] in, Q r This represents the total radiative heat loss from the workpiece surface, expressed in W.

[0124] A The total surface area of ​​the welded workpiece, in meters (m²). 2 ,

[0125] ;

[0126] Wherein, the left side of the equal sign represents the strain rate of the workpiece during the fusion welding process;

[0127] The first term on the right side of the equation is the elastic strain rate;

[0128] The second term is the plastic strain rate;

[0129] The third item is thermal strain rate;

[0130] The fourth item is the creep strain rate;

[0131] The fifth item is the phase transition strain rate.

[0132] ;

[0133] in, α This is the coefficient of thermal expansion, with units of 1 / K;

[0134] Ṫ This is the rate of temperature change, expressed in K / s.

[0135] d ij for kroneckerd function,

[0136] ;

[0137] in, n The Poisson's ratio of the material;

[0138] E This refers to the elastic modulus of the material, expressed in Pa.

[0139] l This is the scaling factor;

[0140] s ij For Cauchy stress tensor;

[0141] s kk It is the sum of the three normal stresses in the Cauchy stress tensor.

[0142] The thermo-mechanical coupling numerical model combines heat conduction and mechanical response, which can accurately simulate and predict temperature distribution, stress distribution, deformation behavior, and morphological evolution of the heat-affected zone during the welding process. It is of great significance for predicting the comprehensive performance of welded joints, such as residual stress, deformation, crack tendency, and the size of the heat-affected zone, thus providing a reliable method for welding process optimization.

[0143] In step S1, the argon arc welding uses a double ellipsoidal heat source, the heat source model of which is as follows:

[0144] ;

[0145] ;

[0146] in, Q The power of the welding arc is expressed in watts (W).

[0147] a , b , c For the shape parameters of the double ellipsoid;

[0148] f 1 and f 2 Let be the heat distribution function of the front and rear ellipsoids. f 1 + f 2 =2.

[0149] The dual-ellipsoidal heat source model abstracts the heat input during welding into two ellipsoidal heat sources. Its heat flux density distribution exhibits non-uniform and non-linear characteristics with spatial position, effectively reflecting the short head and long tail characteristics of the molten pool and the energy distribution of the heat sources along the plate thickness. In TIG welding simulation, the dual-ellipsoidal heat source can capture the local characteristics of the weld joint, thus more accurately reflecting the temperature distribution and morphological evolution of the heat-affected zone during welding. Furthermore, this model can accurately analyze stress and deformation behavior during welding, helping to predict the performance and reliability of the weld joint.

[0150] In step S1, laser welding uses a conical heat source, the heat source model of which is:

[0151] ;

[0152] in, The volumetric heat flux density of the cone-shaped heat source;

[0153] η is the efficiency value;

[0154] P It is the energy of the laser beam, measured in J;

[0155] z e and z i These are the maximum and minimum values ​​in the Z direction, respectively, in mm;

[0156] r e and r i These are the maximum and minimum radii, in mm;

[0157] r It is a radius function with respect to x and y. r The radial distance from the central axis of the heat source is r. 2 = x 2 + y 2 .

[0158] The cone-shaped heat source used abstracts the heat input in the laser welding process into a cone-shaped heat source. Its energy density distribution exhibits spatial non-uniformity and non-linearity, which can effectively simulate the thermal history of the weld, the morphological evolution of the heat-affected zone, and the dynamic changes of the molten pool. In addition, this heat source model can more accurately reveal the temperature gradient, residual stress distribution, and deformation behavior during the laser welding process, thus providing strong support for evaluating the performance and reliability of the welded joint.

[0159] In step S1, since the welding operation area is small, the impact on the surrounding blades and rectifier half-ring is limited. Therefore, when establishing the thermo-mechanical coupling numerical model, it is necessary to consider the influence on the two blades adjacent to the blade to be welded. Tet elements with an average element size of 0.5 mm, 251,171 elements, and 57,481 nodes are used. The model of the blade to be welded and the outer ring are connected by adhesive contact.

[0160] In step S2: the numerical simulation parameters for argon arc welding and laser welding are shown in Table 1 and Table 2, respectively.

[0161] Table 1 Numerical simulation parameters for argon arc welding

[0162]

[0163] Table 2 Numerical Simulation Parameters for Laser Welding

[0164]

[0165] Combination Figure 4The figure shows a comparison of the temperature field at the instant of welding completion in a numerical simulation. As can be seen from the figure, due to the slower welding speed of argon arc welding and the dispersed heat source energy, the molten pool size is significantly larger than that of laser welding. The heat-affected zone of the weld on one side almost covers the entire rectifier half-ring in width, generating a large heat input near the root of the replaced blade. In contrast, laser welding, due to its higher energy density, reduces the heat-affected zone by more than half, which is beneficial for controlling deformation.

[0166] Meanwhile, the simulation results also show that even for laser welding, an energy-controllable welding method, the thermal impact of the welding process on the rectifier half-ring is still significant. In actual welding, local heat dissipation measures can be considered on both sides of the rectifier half-ring.

[0167] Combination Figure 5 The diagram shows a comparison of residual stress fields after welding in a numerical simulation. The residual stress in the welded area after argon arc welding is lower than that after laser welding. This is because the two weld seams of the rectifier blade are closer together, while the heat-affected zone of argon arc welding is larger. The second weld seam has an annealing effect on the first weld seam, relaxing some of the residual stress. In contrast, the interaction between the two weld seams in laser welding is weaker, so the high residual stress areas on both sides remain at room temperature after welding. Although the overall residual stress level decreases after argon arc welding, it causes significant residual stress concentration at the root of the replaced blade, which may affect the performance of the blade.

[0168] Combination Figure 6 The figure shows a comparison of residual axial deformation after numerical simulation welding. The black solid line box represents the rectifier's pre-weld outline. For easier observation, the deformations in the figure are magnified three times. It can be seen that the overall deformation of the rectifier after welding is a radial outward warping of the semi-ring. Due to the good radial stiffness of the rectifier, the axial warping caused by the asymmetry of the weld position in the circumferential direction is very small. The difference in overall axial deformation of the rectifier semi-ring after argon arc welding and laser welding is small, with laser welding reducing deformation by only about 23% compared to argon arc welding.

[0169] Numerical simulation results of the welding process show that using laser welding as a repair technique can control the deformation of the rectifier half-ring to varying degrees, which is beneficial for meeting technical requirements. Therefore, laser welding is selected as the main repair technique in step S4.

[0170] In step S5, when verifying the feasibility of the laser welding method, the laser welding system used includes: a JPT 4KW fiber laser with a fiber diameter of 100µm; a KUKA six-axis linkage robot with a positioning accuracy of 0.1mm; and a HIGHYAG laser head.

[0171] To fully verify the deformation control capability of the laser welding scheme, the rectifier was welded under the simplest mounting conditions with almost no constraints. Before welding, the blades to be welded were tack-fixed onto the semi-ring, with only necessary positional constraints applied to the semi-ring. Welding was then performed using the process parameters shown in Table 2. After welding, the deformation of the rectifier's welded rear face was measured using the pressure block method and was less than 0.05 mm. The joint weld was uniform in size, smooth, and bright, with no spatter. The local argon gas protection was effective, and the weld surface was free of surface defects such as undercut, weld beads, and cracks. The post-weld deformation met the technical requirements.

[0172] Combination Figure 7 , Figure 8 As shown, in step S6, the welding fixture includes two relatively spaced side support plates 3 and a top block 4 disposed between the two side support plates 3; arc-shaped grooves 3a are respectively provided on the inner surfaces of the two opposing side support plates 3, and the arc-shaped grooves 3a are used to engage the two sides of the outer ring 1; the size of the arc-shaped grooves is the same as the size of the outer ring 1 of the rectifier along the contact surface, so as to ensure the axial positioning accuracy of the outer ring 1 of the rectifier; a tightening screw 9 is provided on the top block 4, and the top end of the tightening screw 9 is used to tighten against the inner side of the edge plate of the blade 2 to be welded; the two side support plates 3 are connected by bolts. A U-shaped groove 3d for heat dissipation is opened at the upper part of the middle of the side support plate 3, and a heat dissipation cover plate 8 is installed on the U-shaped groove 3d; the heat dissipation cover plate 8 is made of aluminum alloy. A baffle 3c is provided at the bottom of the U-shaped groove 3d, and a slot 8a is provided at the lower part of the heat dissipation cover plate 8. When the heat dissipation cover plate 8 is assembled, the slot 8a is engaged with the baffle 3c, and the two heat dissipation cover plates 8 are fastened to the U-shaped groove 3d of the side support plate 3 by C-clamps. The U-shaped groove 3d should avoid the welding parts to prevent interference, and at the same time play a role in heat dissipation.

[0173] In this embodiment, the bolt connection between the two side support plates 3 is specifically achieved using small fixing screws 5, large fixing screws 6, large nuts 7, and small nuts 10. Four large holes are symmetrically opened at the lower end of the side support plates for fixing with the large fixing screws 6, and two small holes are symmetrically opened at the upper end for fixing with the small fixing screws 5. The use of small fixing screws 5 and large fixing screws 6 to evenly distribute the stress on the bolt connection structure ensures the reliability of the connection. A square groove 3b is opened in the side support plate, and the top block 4 is rectangular, with both sides of the top block 4 inserted into the square groove 3b.

[0174] Combination Figure 9As shown, during welding, the rectifier is clamped using the aforementioned welding fixture. The size of the arc-shaped groove 3a is the same as the size of the contact surface of the outer edge of the rectifier semi-ring, which is used to ensure the axial positioning accuracy of the rectifier semi-ring. An M4 tightening screw 9 is used to apply a radially outward preload to the front of the blade 2 to be welded. After the blade 2 is fully tightened, the heat dissipation covers 8 on both sides are installed, and the slots 8a of the heat dissipation covers 8 are engaged with the stop bars 3c at the bottom of the U-shaped groove 3d, and tightened using C-clamps. The heat dissipation covers 8 are used to dissipate heat from the rectifier end face to the semi-ring.

[0175] During clamping, ensure that the assembly gap between the blade bottom edge plate and the rectifier outer ring is less than 0.05mm, and tack-fix the four corners where the edge plate and the rectifier contact.

[0176] During welding, weld one side first, and then weld the other side after the rectifier and welding fixture have completely cooled to room temperature. After the rectifier and welding fixture have completely cooled to room temperature, remove the rectifier to complete one blade replacement.

[0177] In step S6, the contact surfaces of the blade 2 to be welded and the bladed disk are thoroughly cleaned to remove oil, rust, dust, and other impurities. Use sandpaper and alcohol for polishing and cleaning. Ensure the welding surface is smooth, flat, dry, and free of any dirt or oxides.

[0178] The specific clamping and welding process is as follows:

[0179] 1. Place the workpiece to be repaired into the welding fixture, so that the two sides of the outer ring 1 are engaged in the arc-shaped grooves 3a on the side support plate 3. Rotate the workpiece to position the part to be repaired in the middle of the side support plate 3 with the U-shaped groove 3d.

[0180] 2. Initial fixation is achieved by tightening the small fixing screw 5 and the large fixing screw 6;

[0181] 3. Tighten the top screw 9 so that the top screw 9 fully supports the bottom edge of the blade 2 to be welded;

[0182] Fourth, finally tighten the small fixing screw 5 and the large fixing screw 6 to ensure reliable fixing;

[0183] 5. Insert the heat dissipation cover 8 into the U-shaped groove 3d on the side support plate and clamp it in place with C-type pliers.

[0184] VI. The selected laser welding system includes: a JPT 4KW fiber laser with a fiber diameter of 100µm; a KUKA six-axis linkage robot with a positioning accuracy of 0.1mm; and a HIGHYAG laser head.

[0185] 7. Adjust the welding parameters as follows: laser power 600W, defocusing amount 10mm, welding speed 600mm / min, thermal efficiency 0.86;

[0186] 8. Weld the part to be repaired, and weld the blade 2 to be welded onto the outer ring 1;

[0187] 9. Repeat the above steps to complete the repair of all blades.

[0188] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for welding repair of rectifier blades, characterized in that, Includes the following steps: Step S1: Establish a thermo-mechanical coupling numerical model of the rectifier welding process based on the finite element method, and establish heat source models for argon arc welding and laser welding; Step S2: Set the numerical simulation parameters for argon arc welding and laser welding, and perform numerical simulation welding on the rectifier using argon arc welding and laser welding methods respectively; Step S3: Compare the temperature field, residual stress field, and residual axial deformation at the instant of welding completion using the two welding methods; Step S4: Based on the comparison results in step S3, determine the appropriate welding method; Step S5: Verify the feasibility of the suitable welding method determined in Step S4 through actual welding tests; Step S6: If the feasibility verification in step S5 is successful, the rectifier is clamped using a welding fixture, and the blade (2) to be welded is welded onto the outer ring (1) using the welding method determined in step S4. The thermo-mechanical coupling numerical model established in step S1 is as follows: ； in: ρ Density, unit: kg / m³ 3 ; C p This is the heat capacity at constant pressure, expressed in J / (kg·K). T Temperature, in Kelvin (K). t Time, in seconds; λ x for x Thermal conductivity in the directional direction, expressed in W / (m·K); λ y for y Thermal conductivity in the directional direction, expressed in W / (m·K); λ z for z Thermal conductivity in the directional direction, expressed in W / (m·K); Q arc Heat generated by the welding heat source, unit: W / m 3 , ； in: q c Heat loss due to convective heat transfer at the workpiece surface, expressed in W / m². 2 ; h c The convective heat transfer coefficient is expressed in W / (m³). 2 ·K); T s The surface temperature of the workpiece is expressed in Kelvin (K). T 0 The ambient air temperature, in Kelvin (K). ； in, Q c This represents the total convective heat loss on the workpiece surface, expressed in W. A The total surface area of ​​the welded workpiece, in meters (m²). 2 , ； in, q r The heat loss due to radiation from the workpiece surface is expressed in W / m². 2 ; ε Emissivity of the workpiece surface; σ It is the Stefan-Boltzmann constant; F The shape factor of the workpiece surface. ； in, Q r This represents the total radiative heat loss from the workpiece surface, expressed in W. A The total surface area of ​​the welded workpiece, in meters (m²). 2 , ； Wherein, the left side of the equal sign represents the strain rate of the workpiece during the fusion welding process; The first term on the right side of the equation is the elastic strain rate; The second term is the plastic strain rate; The third item is thermal strain rate; The fourth item is the creep strain rate; The fifth item is the phase transition strain rate. ； in, α This is the coefficient of thermal expansion, with units of 1 / K; Ṫ This is the rate of temperature change, expressed in K / s. δ ij for kroneckerδ function, ； in, ν The Poisson's ratio of the material; E This refers to the elastic modulus of the material, expressed in Pa. λ This is the scaling factor; σ ij For Cauchy stress tensor; σ kk It is the sum of the three normal stresses in the Cauchy stress tensor; In step S1, the argon arc welding uses a double ellipsoidal heat source, the heat source model of which is as follows: ； ； in, Q The power of the welding arc is expressed in watts (W). a , b , c For the shape parameters of the double ellipsoid; f 1 and f 2 Let be the heat distribution function of the front and rear ellipsoids. f 1 + f 2 =2; In step S1, laser welding uses a conical heat source, the heat source model of which is: in, The volumetric heat flux density of the cone-shaped heat source; η is the efficiency value; P It is the energy of the laser beam, measured in J; z e and z i These are the maximum and minimum values ​​in the Z direction, respectively, in mm; r e and r i These are the maximum and minimum radii, in mm; r It is a radius function with respect to x and y. r The radial distance from the central axis of the heat source is r. 2 = x 2 + y 2 .

2. The rectifier blade welding repair method as described in claim 1, characterized in that, In step S2: The numerical simulation parameters for argon arc welding are: current 30A, voltage 10V, welding speed 60mm / min, and thermal efficiency 0.

75. The numerical simulation parameters for laser welding are: laser power 600W, defocusing amount 10mm, welding speed 600mm / min, and thermal efficiency 0.

86.

3. The rectifier blade welding repair method as described in claim 1, characterized in that, In step S4, laser welding is selected as the welding method; In step S5, when verifying the feasibility of the laser welding method, the laser welding system used includes: a JPT 4KW fiber laser with a fiber diameter of 100µm; and a KUKA six-axis linkage robot with a positioning accuracy of 0.1mm. HIGHYAG laser head.

4. The rectifier blade welding repair method as described in claim 1, characterized in that, In step S6, the welding fixture includes two side support plates (3) arranged at intervals and a top block (4) arranged between the two side support plates (3); arc-shaped grooves (3a) are respectively provided on the inner surfaces of the two side support plates (3), and the arc-shaped grooves (3a) are used to engage the two sides of the outer ring (1); a tightening screw (9) is provided on the top block (4), and the top of the tightening screw (9) is used to tighten the inner side of the flange of the blade (2) to be welded; the two side support plates (3) are connected by bolts.

5. A rectifier blade welding repair method as described in claim 4, characterized in that, A U-shaped groove (3d) for heat dissipation is provided in the upper middle part of the side support plate (3), and a heat dissipation cover plate (8) is installed on the U-shaped groove (3d); the heat dissipation cover plate (8) is made of aluminum alloy.

6. The rectifier blade welding repair method as described in claim 5, characterized in that, A baffle (3c) is provided at the bottom of the U-shaped groove (3d), and a slot (8a) is provided at the lower part of the heat dissipation cover (8). When the heat dissipation cover (8) is assembled, the slot (8a) is engaged with the baffle (3c), and the two heat dissipation covers (8) are fastened to the U-shaped groove (3d) of the side support plate (3) by C-type clamps.

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