Generator stator coil connector lug welding method

Abstract

The invention relates to the technical field of hydro-generators, in particular to a generator stator coil connector lug welding method which comprises the steps of cleaning, brazing filler metal and brazing flux selection, assembling and positioning, brazing filler metal presetting, welding, preheating and post-heat treatment, heat preservation treatment, quality inspection and the like. The method solves the problems of unstable welding quality, inaccurate temperature control, improper welding stress treatment and the like in the prior art, and has the advantages of improving the stability of the welding quality, optimizing the welding effect, accurately controlling the welding temperature, comprehensively evaluating the welding quality, ensuring the stability of process parameters, prolonging the service life of a welding joint, and improving the solidification and crystallization quality of brazing filler metal.

Description

Technical Field

[0001] The invention relates to the technical field of hydro-generators, and in particular to a welding method for a stator coil terminal of a generator. Background Art

[0002] At present, the hydro-turbine generator is one of the key equipment in the power system, and its stable operation is crucial to ensure the power supply. The stator coil terminal welding is an important link in the manufacturing process of the hydro-turbine generator, and the quality of welding directly affects the performance and reliability of the hydro-turbine generator. With the continuous development of the power industry, the requirements for hydro-turbine generators are getting higher and higher. Therefore, in-depth research and mastery of the hydro-turbine generator stator coil terminal welding technology has important practical significance.

[0003] Among the existing welding technologies, silver brazing is a commonly used welding method, which uses silver brazing filler metal to melt at high temperature and combine with the base material. This method has high welding quality, but the cost is relatively high; copper-phosphorus brazing is an economical welding method, which uses copper-phosphorus brazing filler metal for welding and has certain welding strength and reliability; resistance welding uses the resistance heat generated by the current passing through the welding part for welding, which is more efficient, but has higher requirements for welding process.

[0004] The above problems affect the welding quality and reliability of the generator stator coil terminal, and increase the potential safety hazards of the generator operation.

[0005] Therefore, a method for welding the stator coil terminal of a generator that can solve the above-mentioned problem is needed. Summary of the invention

[0006] The present invention provides a method for welding terminal ends of stator coils of generators, comprising the steps of cleaning, selecting solder and brazing flux, assembling and positioning, pre-setting solder, welding, preheating and post-heat treatment, heat preservation treatment and quality inspection. Through process control and comprehensive quality inspection, the method solves the problems of unstable welding quality, inaccurate temperature control, improper welding stress treatment and the like in the prior art. The method has the advantages of improving the stability of welding quality, optimizing welding effect, accurately controlling welding temperature, comprehensively evaluating welding quality, ensuring the stability of process parameters, extending the service life of welding joints, and improving the solidification and crystallization quality of solder.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: a method for welding a stator coil terminal of a generator, comprising the following steps:

[0008] Step a. Clean the stator coil joint to remove oil, dust and oxides;

[0009] Step b. Select a solder according to the material of the stator coil and the working environment, wherein the solder includes a silver-based solder and a copper-based solder;

[0010] Step c. using a brazing agent that matches the brazing material to promote wetting and flow of the brazing material, wherein the brazing agent includes borax and boric acid;

[0011] Step d. Assemble the stator coil to the welding position and position it to ensure that the coil does not move or deform during the welding process;

[0012] Step e. pre-setting the solder at the welding position;

[0013] Step f. Using medium frequency induction brazing or resistance brazing to control the welding current, voltage, time and heating power;

[0014] Step g. Preheating and post-heat treatment of the welding part to reduce welding stress and improve the toughness and fatigue resistance of the welding part;

[0015] Step h. After welding is completed, heat preservation treatment is performed to allow the solder in the brazing seam to fully solidify and crystallize;

[0016] Step i. Check welding quality, including appearance inspection, dimension inspection, non-destructive testing and mechanical property testing.

[0017] Furthermore, in step a, alcohol or acetone solvent is used to clean the stator coil joint.

[0018] Furthermore, in step b, when the stator coil is made of copper alloy and the working environment requires high electrical conductivity and thermal conductivity, a silver-based solder is selected.

[0019] Furthermore, in the step c, borax is used as the brazing agent, which is suitable for silver-based brazing alloys; and boric acid is used as the brazing agent, which is suitable for copper-based brazing alloys.

[0020] Furthermore, in the step d, the stator coil head composed of multiple copper wires is sealed to ensure that the copper wires are arranged neatly and fit tightly.

[0021] Furthermore, in the step f, the welding temperature of the silver-based solder is controlled between 600°C and 800°C, and the heating time is determined according to the stator coil size, the heat capacity of the welding part and the power of the welding equipment.

[0022] Furthermore, in the step h, the insulation time of the insulation treatment is 10 seconds to 30 seconds.

[0023] Furthermore, in step i, the nondestructive testing method includes radiographic testing and ultrasonic testing; the mechanical property testing includes tensile testing and bending testing.

[0024] The advantages of the present invention are:

[0025] The present invention provides a method for welding terminal ends of stator coils of generators, comprising the steps of cleaning, selecting solder and brazing flux, assembling and positioning, pre-setting solder, welding, preheating and post-heat treatment, heat preservation treatment and quality inspection. Through process control and comprehensive quality inspection, the method solves the problems of unstable welding quality, inaccurate temperature control, improper welding stress treatment and the like in the prior art. The method has the advantages of improving the stability of welding quality, optimizing welding effect, accurately controlling welding temperature, comprehensively evaluating welding quality, ensuring the stability of process parameters, extending the service life of welding joints, and improving the solidification and crystallization quality of solder. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Embodiment 1:

[0028] The present invention provides a method for welding a stator coil terminal of a generator. The welding of the stator coil terminal of a generator is a key link in the manufacturing process of the generator, and its quality directly affects the performance and reliability of the generator. However, in practical applications, the welding of the stator coil terminal often faces technical problems such as unstable welding quality and insufficient reliability. These problems are mainly manifested in insufficient strength of the welded joint, decreased electrical conductivity, poor fatigue resistance, etc., which seriously affect the overall performance and service life of the generator.

[0029] Specifically, in the manufacturing process of large generators, the technical difficulties in welding stator coil terminals are mainly reflected in the following aspects: First, the stator coil material is usually a high-conductivity copper alloy, and its surface is easily oxidized, which affects the welding quality. Secondly, the welding parts are often in a high-stress, high-temperature environment, requiring the welded joints to have good mechanical strength and thermal stability. Furthermore, due to the complex structure of the stator coil, the welding position is often difficult to accurately locate, which can easily cause welding deviations. Finally, traditional welding methods make it difficult to accurately control welding parameters, resulting in large fluctuations in welding quality.

[0030] If the welding quality and reliability problems of the stator coil terminal heads cannot be effectively solved, it will have a serious impact on the performance and life of the generator. First, unstable welding quality will lead to increased resistance loss during the operation of the generator and reduce the power generation efficiency. Secondly, the insufficient mechanical strength of the welded joint may cause fracture failure, causing the generator to shut down and affecting the stability of the power supply. Furthermore, the poor fatigue resistance of the welded joint will shorten the service life of the generator and increase the cost of maintenance and replacement. In addition, welding quality problems may also cause safety hazards, such as insulation damage caused by local overheating, and even fire. It can be seen that the development of a technical solution that can effectively improve the welding quality and reliability of the stator coil terminal heads is of great significance to improving the performance of the generator, extending its service life, and ensuring the safe and stable operation of the power system.

[0031] In response to the technical issues of welding quality and reliability of generator stator coil terminal heads, this application has formed the following solution exploration process after in-depth analysis and systematic research.

[0032] First, the main technical difficulties faced in welding stator coil terminals are analyzed: surface oxidation, high stress environment, complex positioning, and inaccurate control of welding parameters, etc. These difficulties lead to insufficient strength of welded joints, reduced conductivity, and poor fatigue resistance.

[0033] In response to these problems, this application considers a variety of possible solutions:

[0034] Traditional solution 1: simple cleaning and using fixed welding parameters, but it cannot effectively solve the problems of surface treatment and precise parameter control.

[0035] Traditional solution 2: Mechanical positioning and fixing of the solder is used, but it is difficult to ensure that the coil does not deform and the solder is evenly distributed.

[0036] Innovative solution: systematically design a full-process welding method to fundamentally improve the welding quality. Specifically, in terms of cleaning, choose solvents such as alcohol or acetone to thoroughly remove surface oil and oxides to create a good foundation for welding. In terms of material selection, accurately select solder according to the material of the stator coil and the working environment, such as silver-based solder for high-conductivity copper alloys. In terms of flux configuration, choose borax or boric acid that matches the solder to promote solder wetting and flow and improve welding quality. In terms of positioning and assembly, ensure that multiple copper wires are arranged neatly and fit tightly to prevent movement or deformation during welding. In terms of welding process, medium-frequency induction brazing or resistance brazing is used to accurately control current, voltage, time and heating power. In terms of heat treatment, preheating and post-heat treatment are carried out to effectively reduce welding stress and improve joint toughness and fatigue resistance. In terms of heat preservation treatment, the heat preservation time is controlled to 10-30 seconds to ensure that the solder is fully solidified and crystallized. In terms of quality inspection, a comprehensive use of appearance inspection, dimensional inspection, radiographic inspection, ultrasonic inspection, and tensile and bending tests are used to fully ensure welding quality.

[0037] Therefore, the present application proposes a method for welding the stator coil terminal of a generator, including a series of steps of cleaning the stator coil joint, selecting solder, using flux, positioning and assembling, presetting solder, using medium frequency induction brazing or resistance brazing, performing heat treatment, heat insulation treatment and checking welding quality.

[0038] Among them, cleaning the stator coil joint refers to removing oil, dust and oxides on the joint surface, which can be specifically cleaned with alcohol or acetone solvents. Among them, solder refers to a low-melting-point alloy material used to connect metal parts, and specifically silver-based solder or copper-based solder can be used. Among them, flux refers to an auxiliary material that promotes the wetting and flow of solder, and specifically borax or boric acid can be used. Among them, medium-frequency induction brazing refers to a method of brazing by heating the workpiece with a medium-frequency electromagnetic field, which can be achieved by controlling the welding current, voltage, time and heating power.

[0039] Among them, resistance brazing refers to a method of brazing using the heat generated by electric current passing through the workpiece, which can be achieved by controlling the welding current, voltage and time.

[0040] The core innovation of this application is to propose a systematic and standardized welding method for generator stator coil terminals. This method effectively solves the problems of stator coil terminal welding quality and reliability through fine cleaning, reasonable material selection, precise welding parameter control, scientific heat treatment process and comprehensive quality inspection.

[0041] The working principle of this application can be described in detail as follows:

[0042] First, use alcohol or acetone solvent to thoroughly clean the stator coil joint to remove oil, dust and oxides on the surface. This step creates good surface conditions for subsequent welding and improves the welding quality. Then, according to the material and working environment of the stator coil, select a suitable solder. For example, when the stator coil is made of copper alloy and the working environment requires high electrical conductivity and thermal conductivity, select a silver-based solder. The choice of solder directly affects the performance of the welded joint. Next, use a brazing flux that matches the selected solder. For silver-based solder, use borax as a brazing flux; for copper-based solder, use boric acid as a brazing flux. The function of the brazing flux is to promote the wetting and flow of the solder and improve the welding effect. Before welding, assemble the stator coil to the welding position and accurately position it. For the stator coil head composed of multiple copper wires, ensure that the copper wires are arranged neatly and fit tightly. This step ensures that the coil will not move or deform during welding, improving the welding accuracy. When welding, use medium-frequency induction brazing or resistance brazing methods. For silver-based solder, the welding temperature is controlled between 600℃-800℃. The heating time is determined according to the size of the stator coil, the heat capacity of the welding part and the power of the welding equipment. By precisely controlling the welding parameters, a stable and reliable welding effect is achieved. After welding is completed, preheating and post-heat treatment are carried out to reduce welding stress and improve the toughness and fatigue resistance of the welding part. Subsequently, a 10-30 second insulation treatment is carried out to allow the brazing material in the brazing seam to fully solidify and crystallize, further improving the welding strength. Finally, the welding quality is comprehensively checked through appearance inspection, dimensional inspection, non-destructive testing (such as radiographic inspection, ultrasonic inspection) and mechanical property testing (such as tensile test, bending test) to ensure that the welded joint meets the performance requirements. This systematic welding method effectively improves the welding quality and reliability by finely controlling each link, thereby improving the overall performance and service life of the generator.

[0043] As a preferred implementation, the present application can be specifically implemented as follows:

[0044] First, use 95% alcohol to clean the stator coil connector. When cleaning, pour the alcohol into a clean container, dip a dust-free cloth in an appropriate amount of alcohol, and gently wipe the surface of the stator coil connector to ensure that every part is fully cleaned. After cleaning, use a clean dust-free cloth to wipe the surface of the connector dry and let it dry naturally at room temperature for 10 minutes to ensure that all residual alcohol is completely evaporated.

[0045] Then, a silver-based solder is selected as the soldering material, specifically a silver-copper-zinc alloy solder with a silver content of 45%, a melting point of 665° C., and good electrical conductivity and oxidation resistance.

[0046] Next, use borax as the brazing flux. Mix borax powder and water in a mass ratio of 1:2 to make a paste. Use a small brush to evenly apply the brazing flux on the surface of the joint to be welded, and the thickness should be controlled at 0.2-0.3mm.

[0047] When welding and positioning, a special positioning fixture is used to fix the stator coil. For the stator coil head composed of 20 copper wires with a diameter of 2mm, ensure that these copper wires are arranged neatly in the fixture, with a spacing of no more than 0.1mm between each other and parallel to the axis of the head.

[0048] The welding was performed by medium frequency induction brazing method. A medium frequency induction heating device with a power of 30kW was used, and the welding temperature was set to 720°C. The heating time was set to 45 seconds, which was the optimal time determined after multiple tests based on the heat capacity of the stator coil and the power of the device.

[0049] After welding, post-heat treatment is carried out immediately. The temperature of the welded part is kept at 650℃ for 5 minutes, and then slowly cooled to room temperature at a rate of 50℃ per minute. This process effectively reduces welding stress and improves the toughness of the welded part.

[0050] Then, the temperature of the welding part is kept at 600℃ for 20 seconds. This step ensures that the brazing material in the brazing seam is fully solidified and crystallized, thus improving the welding strength.

[0051] Finally, the welding quality is comprehensively inspected. First, an appearance inspection is performed to ensure that the weld surface is smooth and free of pores or cracks. Then a vernier caliper with an accuracy of 0.01mm is used to check the size to ensure that the size of the welded joint meets the design requirements. Next, an X-ray flaw detection device is used to perform non-destructive testing on the welded joint to check for internal defects. Finally, a tensile test is performed to require that the tensile strength of the welded joint is not less than 90% of the parent material.

[0052] This systematic and standardized welding method effectively improves the welding quality and reliability of the generator stator coil terminal blocks, providing a reliable guarantee for the stable operation of the generator.

[0053] During the implementation of this application, there is still a technical problem of how to solve the cleaning of the stator coil joints.

[0054] In this regard, the present application further proposes to use alcohol or acetone solvent for cleaning when cleaning the stator coil joint. The present application effectively solves the technical problem of cleaning the stator coil joint by using alcohol or acetone solvent to clean the stator coil joint. This cleaning method is simple and easy to operate, and can quickly remove pollutants on the joint surface and improve the cleaning efficiency. At the same time, since alcohol and acetone are both volatile solvents, no residue will be left on the joint surface after cleaning, ensuring the quality of subsequent welding processes. This cleaning method can not only improve the welding quality, but also extend the service life of the generator and improve its reliability. In the present application, the use of alcohol or acetone solvent to clean the stator coil joint can be achieved in a variety of ways. For example, the immersion method can be used to immerse the stator coil joint in the solvent for a period of time, then take it out and wipe it with a clean dust-free cloth. Another method is to use a solvent spray to spray the solvent directly on the joint surface and then wipe it clean with a dust-free cloth. Ultrasonic cleaning equipment can also be used to place the stator coil joint in an ultrasonic cleaning tank filled with solvent, and the cleaning effect is enhanced by the effect of ultrasound. These cleaning methods combined with the above steps can produce better cleaning effects. For example, after cleaning with solvent, preheating can be performed, which not only helps to remove residual solvent, but also prepares for subsequent welding processes. In addition, solvent cleaning is also closely related to the subsequent selection of brazing material and use of brazing flux. A clean joint surface can ensure good adhesion of brazing material and brazing flux, thereby improving the quality of welding. Specifically, when using alcohol for cleaning, ethanol with a concentration of more than 95% can be selected. The cleaning time can be controlled between 30 seconds and 2 minutes, depending on the degree of contamination of the joint. If acetone is chosen, due to its stronger volatility, the cleaning time can be appropriately shortened, and usually 15 seconds to 1 minute can achieve a good cleaning effect. After cleaning, the joint surface should be wiped immediately with a clean dust-free cloth to prevent the solvent from leaving marks on the surface or re-adsorbing pollutants in the air. The present application can effectively remove oil, dust and oxides on the joint surface by using alcohol or acetone solvent to clean the stator coil joint. This cleaning method has multiple advantages: First, alcohol and acetone are both powerful solvents that can quickly dissolve and remove various organic pollutants such as grease and fingerprints. Secondly, these two solvents are highly volatile and will not leave residue on the joint surface after cleaning, thus avoiding the impact on subsequent welding processes. Thirdly, compared with other cleaning methods, such as mechanical cleaning or strong acid and alkali cleaning, solvent cleaning causes minimal damage to the stator coil material and will not cause surface scratches or corrosion. Finally, this cleaning method is simple to operate, does not require complex equipment, and can be easily implemented in various production environments.

[0055] As a preferred implementation, the following steps can be used to clean the stator coil joint:

[0056] 1. Preparation: Choose 95% ethanol as the cleaning solvent, prepare a clean dust-free cloth and personal protective equipment (such as gloves and goggles).

[0057] 2. Preliminary cleaning: Use clean compressed air to blow away loose dust and particles on the surface of the joint.

[0058] 3. Solvent cleaning: Pour ethanol into a clean spray bottle and spray evenly on the surface of the stator coil joint. Make sure the solvent covers all areas that need to be cleaned.

[0059] 4. Wipe: Immediately use a dust-free cloth to gently wipe the surface of the connector. Be careful to use even wiping force to avoid mechanical damage to the connector.

[0060] 5. Repeat cleaning: If there are still obvious stains after the first cleaning, you can repeat steps 3 and 4 until the joint surface is clean.

[0061] 6. Drying: Use clean compressed air to blow dry the surface of the joint to ensure that there is no residual solvent.

[0062] 7. Inspection: Carefully inspect the joint surface under strong light to ensure that all contaminants have been removed and there is no residue on the surface.

[0063] 8. Protection: If the subsequent welding process cannot be carried out immediately, a clean plastic bag or anti-static bag can be used to temporarily wrap the cleaned joint to prevent re-contamination.

[0064] This method can ensure that the surface of the stator coil joint reaches the optimal cleaning state, laying a good foundation for the subsequent welding process.

[0065] Compared with the prior art, the present application has significant advantages in using alcohol or acetone solvents to clean the stator coil joints. Traditional cleaning methods may include the use of water-based cleaning agents or mechanical wiping, which often have problems such as incomplete cleaning effects, possible residues or surface damage. Cleaning with alcohol or acetone solvents can not only quickly and effectively remove various contaminants, but also ensure that there is no residue on the surface of the joint, while maximizing the protection of the integrity of the joint surface. This cleaning method is simple and fast, easy to implement on the production line, and can significantly improve cleaning efficiency and welding quality, thereby improving the efficiency and reliability of the entire generator manufacturing process.

[0066] In the process of implementing the present application, there is still the problem of how to select a solder suitable for the copper alloy stator coil in a high electrical conductivity and thermal conductivity environment. In this regard, the present application further proposes to select a silver-based solder as the welding material.

[0067] It is pointed out in the background technology that the welding of the stator coil terminal of the generator is an important link in the manufacturing process of the generator, and the welding quality directly affects the performance and reliability of the generator. According to the technical information, when the stator coil material is copper alloy and the working environment requires high electrical conductivity and thermal conductivity, it is necessary to select a silver-based solder. The technical problem is how to select a suitable solder for a specific working environment and material. The technical understanding emphasizes the characteristics of the copper alloy stator coil, the working environment requirements and the selection of silver-based solder to ensure the adaptability and performance of the welding material. Based on the technical understanding, the selection of silver-based solder can be achieved in the following ways: first, confirm that the material of the stator coil is copper alloy, secondly, evaluate the electrical conductivity and thermal conductivity requirements of the working environment, and finally, select silver-based solder to meet the above requirements. The good compatibility of silver-based solder and copper alloy ensures the electrical and thermal conductivity of the welding part. The use of silver-based solder can effectively reduce the thermal stress in the welding process and improve the strength and toughness of the welded joint.

[0068] In the process of solving technical problems, the excellent electrical conductivity and thermal conductivity of silver-based solder enables the stator coil to maintain good performance in a complex working environment. Through reasonable welding process, the quality and reliability of the welding parts are ensured, thereby improving the overall performance of the generator.

[0069] In the embodiment, the specific steps of selecting silver-based solder are as follows: first, clean the stator coil joint to remove surface oil and oxides; then, select silver-based solder and use a suitable flux for welding; then, use medium-frequency induction brazing to control welding parameters; finally, perform quality inspection after welding to ensure the strength and conductivity of the welded joint. By comparison with the prior art, the use of silver-based solder shows better welding performance and higher reliability than traditional copper-based solder under high electrical conductivity and thermal conductivity requirements, solving the problem of unstable welding quality in the prior art.

[0070] The present application further proposes to use borax as a brazing agent, which is suitable for silver-based brazing alloys; and to use boric acid as a brazing agent, which is suitable for copper-based brazing alloys. The technical solution of the present application involves the selection of brazing agents, the type of brazing alloys, and the matching relationship between brazing agents and brazing alloys. Specifically, the present application proposes two brazing agent options: borax and boric acid, and two types of brazing alloys: silver-based brazing alloys and copper-based brazing alloys. The present application establishes a matching relationship between brazing agents and brazing alloys, that is, borax is matched with silver-based brazing alloys, and boric acid is matched with copper-based brazing alloys. By reasonably matching brazing agents and brazing alloys, the present application solves the wettability and fluidity problems of different brazing alloys during welding. Borax as a brazing agent can effectively promote the wetting and flow of silver-based brazing alloys, while boric acid can promote the wetting and flow of copper-based brazing alloys. The establishment of this matching relationship ensures that the brazing alloy can fully wet the welding surface and form a good welding joint during welding. Specifically, when borax is used as a brazing agent for silver-based brazing alloys, its working principle is as follows: borax will decompose at high temperature and react with the oxide on the surface of the silver-based brazing alloy to form a protective film. This protective film can reduce the surface tension of the silver-based solder and improve its wettability on the surface to be welded. At the same time, borax can also dissolve the oxides on the welding surface, further improving the fluidity of the solder. For copper-based solders, the mechanism of action of boric acid as a flux is similar. Boric acid will dehydrate to form boron trioxide during the heating process, which can react with copper oxide on the surface of the copper-based solder to form fusible copper borate. This process not only cleans the welding surface, but also lowers the melting point of the solder, promoting the wetting and flow of the solder. The technical solution of the present application can ensure that the solder can fully wet the welding surface and form a good welded joint during the welding process by selecting a suitable flux. The establishment of this matching relationship not only improves the welding efficiency, but also significantly improves the welding quality.

[0071] As a preferred embodiment, the method of using the brazing agent can be further refined. For example, for silver-based brazing materials, borax can be made into powder or paste and evenly applied to the welding part. The amount of borax used can be adjusted according to the welding area and the amount of brazing material, usually 5% to 15% of the weight of the brazing material. For copper-based brazing materials, boric acid can be dissolved in water to make a saturated solution, and then the welding part can be immersed in the solution or applied with a brush. The concentration of the boric acid solution can be adjusted according to actual needs, usually 20% to 30%.

[0072] In practical applications, the technical solution of this application can be implemented through the following steps:

[0073] First, determine the type of solder according to the material of the stator coil. If the stator coil is a silver alloy, select a silver-based solder; if it is a copper alloy, select a copper-based solder. Secondly, select the corresponding brazing flux according to the selected brazing flux type. For silver-based brazing flux, prepare borax powder; for copper-based brazing flux, prepare boric acid solution. Then, clean the welding part before welding to remove oxides and impurities on the surface. You can use fine sandpaper to gently polish the welding surface and then wipe it with anhydrous ethanol. Then, apply the selected brazing flux evenly to the welding part. For borax powder, you can use a small brush to dip an appropriate amount of powder and apply it evenly; for boric acid solution, you can use a brush to dip the solution and apply it or immerse the welding part in the solution. Finally, perform the welding operation. During the heating process, the brazing flux will play a role in promoting the wetting and flow of the brazing flux, thereby forming a good welded joint. In this way, the technical solution of the present application can effectively solve the wetting and flow problems of different types of brazing fluxes during the welding process, and improve the welding quality and efficiency. Compared with the traditional method, the technical solution of the present application has the following advantages: First, by selecting the flux in a targeted manner, the wettability and fluidity of the solder are significantly improved, the occurrence of welding defects is reduced, and the quality and strength of the welded joint are improved. The flux and solder are reasonably matched, the welding process is optimized, the welding efficiency is improved, and the energy consumption during the welding process is reduced. The technical solution of the present application has a wide range of applicability, and the solder and flux can be flexibly selected according to different stator coil materials to meet a variety of welding needs.

[0074] The present application further proposes to ensure that the copper wires are arranged neatly and closely fit for the stator coil heads composed of multiple copper wires. The technical solution of the present application solves the problem of uneven arrangement and loose fit of the coils during welding by ensuring that the stator coil heads composed of multiple copper wires are arranged neatly and closely fit before welding. This method can significantly improve the welding quality and enhance the mechanical strength and electrical performance of the welding part. By accurately controlling the arrangement and fit of the copper wires, defects such as pores and cracks in the welding process can be reduced, thereby improving the overall performance and reliability of the stator coil of the generator. In addition, neat arrangement and close fit also help to optimize welding heat conduction, ensure uniform welding temperature distribution, and further improve welding quality. In the present application, for the stator coil heads composed of multiple copper wires, the specific implementation methods of ensuring that the copper wires are arranged neatly and closely fit can include the following: First, a specially designed fixture or mold can be used to fix and arrange the copper wires. This fixture can have multiple notches, and the size of each notch matches the diameter of a single copper wire, so as to ensure that each copper wire can be accurately positioned. In this way, the neat arrangement of the copper wires can be achieved. Secondly, a pressure device can be used to ensure a tight fit between the copper wires. This pressure device can be hydraulically or pneumatically driven, and can apply uniform pressure to the copper wires in multiple directions, so that the copper wires fit tightly together and eliminate possible gaps. Furthermore, special binding tools or materials can be used to temporarily fix the arranged copper wires. For example, high-temperature resistant insulating tape or wire ties can be used to bundle neatly arranged copper wires together to ensure that they will not shift during the welding process. In addition, preforming technology can also be used. Before welding, multiple copper wires can be preformed using special forming equipment to form an integral, regular-shaped head structure. This method can ensure the neat arrangement and tight fit of the copper wires during the forming process.

[0075] These technical features play an important role in solving the welding problem of stator coil heads composed of multiple copper wires. The stator coil heads composed of multiple copper wires are the objects of welding, and special attention should be paid to their structural characteristics. By ensuring that the copper wires are arranged neatly, the uniformity and stability of welding can be improved, and welding defects can be reduced. Ensuring that the copper wires fit tightly can reduce the welding gap and improve the welding strength and conductivity.

[0076] These features, combined with the aforementioned steps of cleaning, selecting solder and flux, and positioning, form a complete welding process. For example, after the cleaning step, the arrangement of the copper wires can be more easily observed and adjusted. After selecting the appropriate solder and flux, the neatly arranged and tightly fitted copper wires can better combine with the solder to form a uniform welded joint. In the positioning step, the neatly arranged copper wires are easier to be accurately positioned, thereby ensuring the accuracy of the welding position.

[0077] In practical applications, the technical solution of the present application can significantly improve welding quality and efficiency. By ensuring that the copper wires are neatly arranged and tightly fitted, defects in the welding process, such as pores and cracks, can be reduced. This not only improves the mechanical strength of the welded joint, but also improves its electrical properties. Neatly arranged copper wires can form a more uniform welded joint, reduce local stress concentration, and improve the fatigue resistance of the joint. Tightly fitting copper wires can reduce the welding gap, reduce resistance, and improve conductivity.

[0078] In addition, this method can also optimize welding heat conduction. When the copper wires are arranged neatly and fit tightly, the heat can be more evenly distributed in the welding area, avoiding the problem of local overheating or underheating. This not only helps to form a more uniform welded joint, but also reduces the generation of thermal stress and further improves the welding quality. Compared with the prior art, the technical solution of the present application has obvious advantages. Traditional welding methods often ignore the arrangement and fitting state of multiple copper wires, resulting in unstable welding quality and prone to defects such as pores and cracks. The present application significantly improves the welding quality and reliability by precisely controlling the arrangement and fitting state of the copper wires. In addition, the method of the present application can also improve welding efficiency, reduce rework rate, and thus reduce production costs. These advantages make the technical solution of the present application have important application value and innovative significance in the field of generator stator coil terminal welding.

[0079] The present application further proposes a technical solution for the precise control of the welding temperature and heating time of the silver-based solder. In the brazing process of the generator stator coil terminal, the welding temperature and heating time of the silver-based solder are key factors affecting the welding quality. Traditional brazing methods often cannot accurately control the temperature and heating time, which easily leads to unstable welding quality. The present application achieves precise control of the silver-based solder welding process by setting a specific temperature control range and a heating time determination method. Specifically, the welding temperature is strictly controlled between 600°C and 800°C. This temperature range ensures that the silver-based solder can be fully melted and form a good metallurgical bond with the welded material. At the same time, the determination of the heating time takes into account multiple key factors, including the size of the stator coil, the heat capacity of the welding part, and the power of the welding equipment. The key to this method is to dynamically adjust the heating time according to the specific characteristics of different stator coils. For example, for a larger stator coil, a longer heating time is required to ensure uniform heat distribution; while for a welding part with a lower heat capacity, the heating time can be shortened accordingly. Consideration of the power of the welding equipment further optimizes the efficiency of heat transfer. This precise temperature and time control can effectively avoid common problems in traditional brazing methods, such as insufficient brazing material flow, thermal stress concentration or local overheating. This not only improves the consistency and reliability of welding, but also significantly reduces welding defects and extends the service life of the stator coil terminal.

[0080] During specific implementation, medium frequency induction brazing or resistance brazing technology can be used. Taking medium frequency induction brazing as an example, by accurately controlling the size and action time of the induced current, precise control of the welding temperature and heating time can be achieved. In actual operation, a database of the correspondence between the stator coil size, material and optimal welding parameters can be established in advance, so as to achieve more intelligent welding process control. Compared with the traditional fixed parameter brazing method, the technical solution of the present application has higher flexibility and adaptability. By dynamically adjusting the welding parameters, it can adapt to stator coils of different specifications and materials, significantly improving the reliability and scope of application of the brazing process. As a preferred embodiment, for a copper wire stator coil with a diameter of 2-5 mm, a welding temperature of 600-650°C can be used, and the heating time is controlled at 15-25 seconds. For cases where the coil size is larger or the heat capacity is higher, the temperature and time parameters can be adjusted accordingly to ensure the best welding quality.

[0081] In step h, the insulation time of the insulation treatment is 10 seconds to 30 seconds. The technical solution of the present application performs insulation treatment after welding is completed, and the insulation time is controlled between 10 seconds and 30 seconds. This specific time range is the result of careful selection and optimization. Specifically, the insulation treatment time is controlled between 10 seconds and 30 seconds for the following technical considerations: First, 10 seconds is the shortest time to ensure that the brazing material is fully solidified. Below this time, the brazing material may not be completely solidified, thereby affecting the welding strength. Secondly, 30 seconds is the upper limit time to avoid excessive insulation. Exceeding this time may cause changes in material properties or excessive heating of the structure around the welding part. Within this time range, the brazing material can get sufficient time to solidify and crystallize. This process is essential for forming a strong and stable welded joint. By controlling the insulation time, it can be ensured that the brazing material in the brazing seam is evenly distributed and forms a good metallurgical bond with the material being welded. In addition, this insulation time range also takes into account the efficiency requirements of industrial production. A time of 10-30 seconds can ensure the welding quality without significantly extending the production cycle, thus achieving a good balance between ensuring quality and improving efficiency.

[0082] Further, this insulation time range is coordinated with the aforementioned welding temperature and heating time. For example, for the welding temperature of 600°C-800°C for silver-based solder, a insulation time of 10-30 seconds can effectively cooperate with the temperature drop process, so that the solder can complete solidification and crystallization within a suitable temperature range. The specific insulation treatment can be achieved in a variety of ways. For example, a constant temperature box or a heating plate can be used to insulate the welding part immediately after welding. The residual heat of the welding equipment can also be used to achieve the insulation effect by controlling the cooling rate. In actual operation, the most suitable insulation method can be selected according to the specific welding equipment and process requirements. As a preferred embodiment, a programmable automatic insulation device can be used. The device can accurately control the insulation time and automatically adjust the insulation parameters according to different welding materials and workpiece sizes. This can not only ensure the consistency of the insulation effect, but also improve production efficiency. Therefore, through reasonable insulation time control, the present application can effectively reduce welding stress and improve welding quality. This is of great significance to ensure the reliability and safety of the stator coil terminal of the generator. Especially in high-power, high-speed generators, the welding quality of the terminal heads is directly related to the operating stability and life of the entire equipment.

[0083] In a specific embodiment, it is assumed that a copper alloy stator coil terminal with a diameter of 10 mm is welded, and a silver-based solder is used, and the welding temperature is controlled at 750°C. After welding is completed, the welding part is immediately placed in a thermostat preheated to 200°C for insulation treatment. The insulation time is set to 20 seconds. Within these 20 seconds, the solder can fully solidify and crystallize, and the temperature of the welding part can also drop evenly, effectively reducing the generation of thermal stress. After the insulation treatment is completed, the welded joint is inspected. X-ray flaw detection found that the solder in the brazing seam is evenly distributed, and no pores or cracks appear. The tensile test results show that the strength of the welded joint reaches more than 95% of the strength of the parent material, which is much higher than the industry standard requirements. This fully proves the effectiveness of the insulation time control in this application. Compared with the prior art, the insulation treatment time control method of this application has obvious advantages. Traditional methods often ignore the importance of insulation treatment, or use empirical estimation to determine the insulation time, resulting in unstable welding quality. However, this application not only ensures the consistency of welding quality, but also improves production efficiency by accurately controlling the insulation time. Especially in mass production, this advantage is more obvious, which can significantly reduce the welding defect rate and reduce the cost of rework and quality inspection.

[0084] In some of the above embodiments, the present application still has the problem of incomplete welding quality detection during implementation. In this regard, the present application further proposes a non-destructive detection method and a mechanical property test.

[0085] It is pointed out in the background technology that the welding of the stator coil terminal of the generator is an important link in the manufacturing process of the generator, and the quality of welding directly affects the performance and reliability of the generator. Therefore, the use of non-destructive testing methods and mechanical property tests can effectively solve the problem of welding quality detection. Non-destructive testing methods such as radiographic testing and ultrasonic testing can detect internal defects without destroying the welded joint, ensuring the integrity and reliability of the welding. Mechanical property tests directly evaluate the mechanical properties of the welded joint through tensile tests and bending tests to verify whether it can withstand the stress and load in actual operation.

[0086] The technical understanding mentioned that the combination of non-destructive testing methods and mechanical property tests provides a comprehensive means of testing welding quality. During the implementation process, the welded joints are first inspected for appearance and size to ensure that the shape and size of the welded joints meet the design requirements. Next, the welded joints are inspected for internal defects using radiographic and ultrasonic testing to detect potential defects such as pores and slag inclusions. Finally, the strength and toughness of the welded joints are evaluated through tensile and bending tests to ensure that they meet the design requirements.

[0087] Based on the technical understanding, the implementation methods of non-destructive testing and mechanical properties testing are specifically explained. For example, radiographic testing can use X-ray or gamma-ray equipment to detect defects inside welded joints; ultrasonic testing uses ultrasonic probes to determine the quality of welded joints by transmitting and receiving ultrasonic signals. In mechanical properties testing, the specific parameters and standards of tensile tests and bending tests should comply with relevant industry standards to ensure the accuracy and reliability of test results.

[0088] Through the above steps, the technical solution effectively solves the problem of incomplete welding quality inspection. The non-destructive testing method ensures the internal quality of the welded joint, while the mechanical property test ensures the performance of the welded joint in actual operation. This combination improves the efficiency and accuracy of welding quality inspection and ensures the reliability and safety of the generator.

[0089] In the embodiment, during the welding process of the generator stator coil terminal, the stator coil terminal is first cleaned to ensure that there is no oil, dust and oxide. Then, a suitable solder and flux are selected for welding. After welding, the welded joint is non-destructively tested by radiographic and ultrasonic flaw detection methods to ensure that there are no defects inside the welded joint. Subsequently, a tensile test and a bending test are performed to evaluate the strength and toughness of the welded joint to ensure that it meets the design requirements.

[0090] Compared with the prior art, the technical solution of the present application provides a more comprehensive means of welding quality detection through the combination of non-destructive testing and mechanical property testing, solves the problem that traditional detection methods cannot comprehensively detect welding quality, and improves the overall reliability of the generator.

[0091] This application comprehensively evaluates the welding quality from multiple angles such as appearance, internal structure and mechanical properties by comprehensively using a variety of detection methods. This multi-dimensional detection method can effectively identify various types of welding defects and ensure the reliability and safety of the welding of the stator coil terminal of the generator. Surface problems are quickly discovered through appearance inspection and dimensional inspection, non-destructive testing deeply detects internal defects, and mechanical property testing verifies the actual load-bearing capacity of the welded joint, thereby fully ensuring the welding quality and improving the overall performance and service life of the generator. Specifically, this application uses a variety of detection methods when checking the welding quality. Among them, non-destructive testing methods include radiographic testing and ultrasonic testing. Radiographic testing uses X-rays or gamma rays to penetrate the welding part and detects defects such as pores and slag inclusions by analyzing the attenuation of the rays during the penetration process. This method can clearly display the internal structure of the welded joint and is particularly suitable for detecting defects with large density differences. Ultrasonic testing uses the characteristics of ultrasonic waves propagating in materials to detect the continuity and internal defects of welded joints by analyzing the reflection and attenuation of ultrasonic waves. This method is particularly effective for detecting linear defects such as cracks and incomplete penetration. Further, mechanical property tests include tensile tests and bending tests. The tensile test can test the tensile strength of the welded joint. By applying gradually increasing tensile force to the welded sample until the sample breaks, important parameters such as the maximum load-bearing capacity and elongation of the welded joint can be obtained. The bending test can evaluate the plasticity and bending resistance of the welded joint. By applying bending force to the welded sample and observing the deformation of the sample during the bending process and whether cracks appear, the toughness and fatigue resistance of the welded joint can be determined.

[0092] Therefore, the combination of these detection methods can comprehensively evaluate the welding quality. Appearance inspection and dimensional inspection can quickly find surface defects and dimensional deviations, non-destructive testing methods can deeply detect defects inside the weld without destroying the weld structure, and mechanical property testing can directly evaluate the strength and toughness of the welded joint. This multi-dimensional detection method can not only effectively identify various types of welding defects, but also ensure the reliability and safety of the generator stator coil terminal welding.

[0093] As a preferred implementation, welding quality inspection can be performed according to the following steps:

[0094] First, conduct an appearance inspection to observe whether there are obvious defects such as cracks, pores, weld bumps, etc. on the surface of the welded joint, and use a caliper or micrometer to check the size to ensure that the size of the welded joint meets the design requirements.

[0095] Secondly, non-destructive testing is performed using radiographic flaw detection. Using an X-ray source, place the weld joint between the source and the detector, and analyze the image after the rays penetrate to detect whether there are defects such as pores and slag inclusions inside the weld. For example, a 200kV X-ray source can be used, with an exposure time of 60 seconds and a focal length of 700mm.

[0096] Then, use ultrasonic flaw detection equipment for inspection. Select a probe with an appropriate frequency (such as 5MHz), apply coupling agent to the surface of the weld joint, and move the probe to scan the entire weld area. By analyzing the ultrasonic echo signal, determine whether the weld joint has defects such as cracks and incomplete penetration.

[0097] Next, perform a tensile test. Cut a standard specimen from the weld joint and use a universal testing machine to perform a tensile test. For example, the tensile speed can be set to 2mm / min, and the maximum load-bearing capacity and elongation at break of the specimen can be recorded.

[0098] Finally, conduct a bending test. Prepare a bending specimen and use a dedicated bending test device to test it. For example, the bending radius can be set to 4 times the specimen thickness, the bending angle to 180°, and observe whether the specimen cracks or breaks during the bending process.

[0099] Through this series of inspection steps, the quality of the welded joints can be comprehensively evaluated to ensure the reliability and safety of the welding of the generator stator coil terminal blocks.

[0100] Compared with the prior art, the welding quality detection method of the present application has the following advantages:

[0101] First, this application uses a combination of multiple detection methods, which can more comprehensively evaluate the welding quality than a single detection method. For example, traditional methods may only rely on appearance inspection and simple mechanical testing, but cannot detect internal defects. This application can effectively detect hidden defects such as pores and cracks inside the weld by introducing radiographic and ultrasonic flaw detection.

[0102] Secondly, the inspection method of this application covers multiple performance aspects of the welded joint. The surface quality is evaluated by visual inspection and dimensional inspection, the internal structure is evaluated by non-destructive testing, and the actual load-bearing capacity is evaluated by mechanical property testing. This multi-dimensional evaluation method can more accurately judge the overall quality and reliability of the welded joint.

[0103] Finally, the detection methods of this application are non-destructive and repeatable. Except for the mechanical property test, other detection methods will not cause damage to the welded joint, which makes the detection widely used in actual production, not limited to sampling inspection. At the same time, the parameters and processes of these detection methods can be standardized to ensure the consistency and comparability of the test results.

[0104] By adopting this comprehensive welding quality detection method, the present application can significantly improve the reliability and safety of the welding of the generator stator coil terminal heads, reduce generator failures caused by welding defects, extend the service life of the generator, and improve power generation efficiency.

[0105] This application further proposes a technical solution to comprehensively evaluate welding quality through a variety of detection methods. As mentioned in the background technology, the generator is a key device in the power system, and the welding quality of the stator coil terminal directly affects the performance and reliability of the generator. With the development of the power industry, the requirements for welding quality are increasing day by day, so it is particularly important to conduct in-depth research on welding technology.

[0106] The technical means adopted by the present invention include non-destructive testing methods and mechanical property tests. Non-destructive testing methods such as radiographic testing and ultrasonic testing can effectively detect defects inside welded joints, such as pores, slag inclusions and cracks, without causing damage to the welded parts. Mechanical property tests evaluate the strength and ductility of welded joints through tensile tests and bending tests. The present invention uses a combination of multiple detection methods to comprehensively evaluate welding quality and ensure the reliability and safety of welding. The combination of non-destructive testing and mechanical property testing makes the evaluation of welding quality more accurate and comprehensive. Through this comprehensive detection method, the technical problems of welding quality inspection can be effectively solved and the accuracy of welding quality control can be improved.

[0107] In the specific implementation, the key features are implemented in the following ways: nondestructive testing can be performed after welding to avoid damage to the welded structure; mechanical property testing can be performed after welding is completed to ensure the strength and toughness of the welded joint. The correlation between nondestructive testing and mechanical property testing makes the evaluation of welding quality more comprehensive, thereby solving the problem that welding quality is not easy to detect. The present invention first cleans the welded joint to remove oil stains and oxides, and then selects suitable solder and flux for welding. After welding is completed, nondestructive testing and mechanical property testing are used to evaluate the welding quality. The execution logic of each step is interrelated to ensure the reliability of welding quality. In a specific embodiment, silver-based solder is used for welding the stator coil terminal of the generator, and the welding temperature is controlled between 600℃-800℃. After welding, insulation treatment is performed for 15 seconds, followed by nondestructive testing and tensile testing to ensure that the strength and toughness of the welded joint meet the requirements. This application significantly improves the accuracy and comprehensiveness of welding quality evaluation by comprehensively using nondestructive testing and mechanical property testing, solves the problem that traditional detection methods cannot comprehensively evaluate welding quality, and demonstrates the innovation and superiority of this application.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for welding a stator coil terminal of a generator, characterized in that: The following steps are involved: Step a. Clean the stator coil joint to remove oil, dust and oxides; Step b. Select a solder according to the material of the stator coil and the working environment, wherein the solder includes a silver-based solder and a copper-based solder; Step c. using a brazing agent that matches the brazing material to promote wetting and flow of the brazing material, wherein the brazing agent includes borax and boric acid; Step d. Assemble the stator coil to the welding position and position it to ensure that the coil does not move or deform during the welding process; Step e. pre-setting the solder at the welding position; Step f. Using medium frequency induction brazing or resistance brazing to control the welding current, voltage, time and heating power; Step g. Preheating and post-heat treatment of the welding part to reduce welding stress and improve the toughness and fatigue resistance of the welding part; Step h. After welding is completed, heat preservation treatment is performed to allow the solder in the brazing seam to fully solidify and crystallize; Step i. Check welding quality, including appearance inspection, dimension inspection, non-destructive testing and mechanical property testing.

2. A method for welding a generator stator coil terminal according to claim 1, characterized in that: In the step a, alcohol or acetone solvent is used to clean the stator coil joint.

3. A method for welding a generator stator coil terminal according to claim 1, characterized in that: In the step b, when the stator coil is made of copper alloy and the working environment requires high electrical conductivity and thermal conductivity, a silver-based solder is selected.

4. A method for welding a generator stator coil terminal according to claim 1, characterized in that: In the step c, borax is used as the brazing agent, which is suitable for silver-based brazing alloys; boric acid is used as the brazing agent, which is suitable for copper-based brazing alloys.

5. The method for welding the stator coil terminal of a generator according to claim 1, characterized in that: In the step d, the stator coil head composed of multiple copper wires is sealed to ensure that the copper wires are arranged neatly and fit tightly.

6. A method for welding a generator stator coil terminal according to claim 1, characterized in that: In the step f, the welding temperature of the silver-based solder is controlled between 600° C. and 800° C., and the heating time is determined according to the size of the stator coil, the heat capacity of the welding part and the power of the welding equipment.

7. A method for welding a generator stator coil terminal according to claim 1, characterized in that: In the step h, the insulation time of the insulation treatment is 10 seconds to 30 seconds.

8. The method for welding the stator coil terminal of a generator according to claim 1, characterized in that: In the step i, the non-destructive testing method includes radiographic testing and ultrasonic testing; the mechanical property test includes tensile testing and bending testing.