An optimization method for stator and rotor welding process

Abstract

This invention discloses an optimized method for stator and rotor welding processes in the field of motor manufacturing, comprising the following steps: improving welding quality through pretreatment, coating with modified composite materials, and optimizing laser welding parameters. During pretreatment, the stator and rotor areas to be welded are sanded with 800-1200 grit sandpaper, followed by ultrasonic cleaning with acetone or alcohol for 10-15 minutes to achieve a surface roughness Ra ≤ 1.6 μm; a 0.1-0.3 mm thick layer of modified composite material is coated onto one surface and dried at 80-120°C for 1-2 hours; laser welding is employed, with the molten pool temperature monitored at 1800-2200°C during welding; immediately after welding, the welded parts are placed in a holding furnace at 200-300°C for slow cooling for 2-4 hours, and then cooled to room temperature at a rate of 5-10°C / min. This method effectively improves the strength, toughness, and crack resistance of the welded joint, reduces the heat-affected zone, and minimizes deformation.

Description

Technical Field

[0001] This invention relates to the field of motor manufacturing technology, and specifically to an optimization method for stator and rotor welding processes. Background Technology

[0002] The stator and rotor, as the core components of an electric motor, together constitute the motor's "stationary-rotating" structure, achieving efficient conversion of electrical energy into mechanical energy through electromagnetic interaction. In fields such as industrial drives, new energy power generation, and smart homes, the performance and reliability of the motor directly determine the operating efficiency and service life of the equipment, and the welding quality of the stator and rotor is a key factor affecting this performance. Whether it's fixing the permanent magnets of the rotor in a permanent magnet synchronous motor, connecting the winding leads in a wound-rotor motor, or combining the rotor bars with the end rings, all rely on welding processes to achieve reliable connections. If the weld joint has defects such as insufficient strength, porosity, or cracks, the motor is prone to abnormal heating, excessive vibration, or even bar breakage and burnout during operation, severely restricting the application of the motor in high-end equipment.

[0003] Traditional stator and rotor welding processes (such as argon arc welding and laser welding) can meet basic connection requirements, but they have revealed significant limitations in long-term application. On the one hand, the intense thermo-mechanical coupling between the base material and the filler material during welding leads to grain coarsening in the heat-affected zone (HAZ), resulting in decreased joint toughness. On the other hand, existing filler materials have insufficient metallurgical compatibility with the base material, resulting in poor wettability of the molten pool and making them prone to defects such as incomplete fusion and porosity. Furthermore, the welding deformation is large, requiring additional correction processes. These problems are particularly prominent in high-power-density motors or precision drive applications. For example, in the stator and rotor welding of new energy vehicle drive motors, insufficient joint strength can lead to rotor detachment and safety accidents; while the deterioration of the heat-affected zone performance accelerates motor aging and shortens its service life.

[0004] As electric motors evolve towards higher power, higher speed, and lighter weight, higher demands are placed on the overall performance of welded joints. Traditional processes are no longer sufficient to meet the stringent requirements of modern motors for high bond strength, low deformation, and resistance to fatigue cracks. There is an urgent need to develop a novel welding method that synergistically optimizes materials and processes. This invention addresses this technical challenge by introducing modified composite materials as a transition layer or filler material during the welding process. Combined with optimized laser welding parameters, this approach comprehensively enhances the mechanical properties and reliability of stator and rotor welded joints by improving molten pool wettability, inhibiting crack propagation, and refining weld microstructure. This provides crucial technical support for the manufacturing of high-performance motors. Summary of the Invention

[0005] The purpose of this invention is to provide an optimized method for stator and rotor welding process, which solves the technical problems of insufficient joint strength, coarse grains in the heat-affected zone, large deformation and porosity cracks in traditional stator and rotor welding, which are caused by thermal coupling leading to microstructure deterioration and poor metallurgical compatibility of filler materials.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] An optimization method for stator and rotor welding process includes the following steps:

[0008] S1. First, the stator and rotor parts to be welded are pre-treated by sanding with sandpaper and then ultrasonically cleaning with acetone or alcohol. The surface roughness of the parts to be welded after cleaning is Ra≤1.6μm.

[0009] S2, the modified composite material is coated onto one of the surfaces to be welded, and the coated surface is placed in an oven to dry;

[0010] S3 uses laser welding equipment for welding, with the laser power set to 2-5kW, the welding speed to 5-15mm / s, the defocusing amount to +5 to -2mm, the shielding gas to be argon, and the flow rate to be 15-30L / min. During the welding process, the temperature of the molten pool is monitored in real time by an infrared thermometer, and the temperature of the molten pool is 1800-2200℃.

[0011] According to a preferred embodiment of the present invention, the sandpaper is purchased from Baige Abrasives Co., Ltd., and the model is W5 (800-1200 grit wet sandpaper).

[0012] According to a preferred embodiment of the present invention, the acetone is purchased from Sinopharm Chemical Reagent Co., Ltd., and is of analytical grade (purity ≥99.5%). It is used for ultrasonic cleaning of the parts to be welded to ensure the removal of organic contaminants.

[0013] According to a preferred embodiment of the present invention, the alcohol is purchased from Sinopharm Chemical Reagent Co., Ltd., and is of analytical grade (purity ≥99.7%). It is used for secondary ultrasonic cleaning of the parts to be welded to further remove moisture and residual impurities.

[0014] According to a preferred embodiment of the present invention, the laser welding equipment was purchased from Shanghai IPG Laser Technology Co., Ltd., model YLS-4000, with a laser wavelength of 1064nm and a beam quality of M. 2 ≤1.2, power range 2-5kW.

[0015] According to a preferred embodiment of the present invention, the infrared thermometer is purchased from FLIR Systems, Inc., USA, model FLIR SC7000, with a response time of 10μs, a temperature range of 500-3000℃, and an accuracy of ±2℃, and is used for real-time monitoring of the molten pool temperature during the welding process.

[0016] According to a preferred embodiment of the present invention, in step S1, the grit size of the sandpaper is 800-1200 mesh, and the ultrasonic cleaning time is 10-15 min.

[0017] According to a preferred embodiment of the present invention, in step S2, the thickness of the modified composite material is 0.1-0.3 mm, the drying temperature in the oven is 80-120°C, and the drying time is 1-2 h.

[0018] According to a preferred embodiment of the present invention, in step S3, the laser power is 3-4kW; the welding speed is 8-12mm / s; and the flow rate is 20-25L / min.

[0019] In this invention, when laser energy is applied to the surface of the modified composite material to be welded, the stainless steel matrix in the composite material melts preferentially. Since its melting point is lower than that of pure iron, it forms a molten pool with a depth of 0.1-0.3 mm with the base metal. The titanium vanadium powder, having partially melted and incorporated into the stainless steel matrix, continuously releases active Ti and V atoms in the molten pool, maintaining the alloying process. Short-cut carbon fibers flow with the molten pool and are distributed in the weld. Their surface active sites bond with the molten pool metal through van der Waals forces or coordination bonds, limiting the lateral growth of grains during cooling and solidification, resulting in a weld microstructure exhibiting fine columnar or equiaxed crystals. Argon gas (flow rate 20-25 L / min) covers the surface of the molten pool in a laminar flow, removing O2 and N2 from the air to prevent secondary oxidation or nitriding of the molten pool. An infrared thermometer monitors the molten pool temperature in real time (1800-2200℃) to ensure that the temperature is within the optimal metallurgical bonding range between the stainless steel and the base metal (avoiding over-melting of the base metal due to excessively high temperatures or incomplete fusion due to excessively low temperatures).

[0020] The process steps for stator and rotor welding using laser welding equipment in this invention are as follows: First, turn on the laser welding equipment and debug it, check the stability of the laser output power, confirm that the reflectors and focusing lenses of the optical path system are clean and free of contamination, adjust the diameter of the focused spot to 0.1-0.3mm, selecting the appropriate diameter based on the thickness of the stator and rotor parts to be welded; use a smaller diameter for thin-walled parts and a larger diameter for thick-walled parts; fix the pre-treated stator and rotor with a special fixture, calibrate the coaxiality error using a laser alignment instrument to ensure it is ≤0.05mm, and uniformly adjust the gap between the parts to be welded to 0.05-0.15mm along the circumferential direction; connect a high-purity argon cylinder (purity ≥99.99%). 9%), install annular gas nozzles (inner diameter 8-12mm, height from weld surface 5-8mm, tilt angle 15-30°), and adjust the gas flow rate to 20-25L / min; according to the stator and rotor materials (such as silicon steel sheets, permanent magnets, or copper conductors) and thickness, preset the initial parameters in the laser control system: laser power 3-4kW (lower value for thin walls, higher value for thick walls), welding speed 8-12mm / s, defocusing amount +5 to -2mm; select stator and rotor samples from the same batch as the formal welding for trial welding, and observe the weld quality through X-ray flaw detection or microscopy. If defects are found, fine-tune the parameters until the trial weld is qualified; start The welding process begins by aligning the surface coated with the modified composite material to be welded with the laser beam, which scans uniformly along the circumference. The temperature of the molten pool center is collected in real-time by an infrared thermometer and fed back to the laser control system. If the temperature is below 1800℃, the laser power is automatically increased by 2-5% or the welding speed is reduced by 5-10%. If the temperature is above 2200℃, the power is automatically reduced by 2-5% or the speed is increased by 5-10%. If oxidation discoloration is observed on the molten pool surface during welding, the argon gas flow rate is immediately increased to 25-30 L / min until the color returns to normal. When welding narrow sections such as stator slots or rotor bar roots, the laser scanning is switched. The mode is pulse mode, which reduces heat input and avoids burn-through. At the same time, the defocusing amount is adjusted to -1 to -2mm to increase the penetration depth. If the stator and rotor adopt an overlapping structure, a V-shaped bevel needs to be pre-processed at the overlapping edge. During welding, the laser beam scans along the center of the bevel to ensure that the molten pool completely covers the overlapping interface and avoids incomplete fusion defects. After welding, the workpiece is immediately transferred to the holding furnace, the holding temperature is set to 200-300℃, and the slow cooling program is started to avoid stress concentration caused by weld shrinkage due to rapid cooling. During the slow cooling process, the weld surface is observed with the naked eye or a magnifying glass. If obvious pores or cracks are found, the defect location is marked and subsequently repaired by laser welding.

[0021] According to a preferred embodiment of the present invention, the optimization method of the stator and rotor welding process further includes: after welding is completed, the weldment is immediately placed in a heat preservation furnace for slow cooling treatment, the heat preservation temperature is set to 200-300℃, the heat preservation time is 2-4h, and then cooled to room temperature at a rate of 5-10℃ / min.

[0022] In this invention, the residual stress in the weld mainly originates from the volume shrinkage during rapid solidification of the molten pool (the linear expansion coefficient of stainless steel is approximately 17 × 10⁻⁶). -6 At a temperature similar to that of silicon steel sheets (around ℃), during slow cooling, atoms gradually adjust their positions through diffusion, reducing dislocation density and achieving a residual stress release rate >80%. Slow cooling promotes the precipitation of a small amount of carbides at grain boundaries, pinning the grain boundaries and hindering dislocation movement, further enhancing the joint's toughness. Ultimately, through the synergistic effects of multiple mechanisms, including metallurgical bonding, mutual solubility between stainless steel and the base material, mechanical intercalation (carbon fiber embedding in the metal matrix), and grain refinement (grain refinement), a high-strength, low-defect welded joint is formed.

[0023] According to a preferred embodiment of the present invention, the preparation steps of the modified composite material include:

[0024] A1, Weigh out the matrix material, reinforcing phase and activator, wherein the activator is a mixture of titanium powder and vanadium powder;

[0025] A2, add the weighed matrix material, reinforcing phase and activator from step A1 into a planetary ball mill, use agate balls as the grinding medium, and mix under argon protection;

[0026] A3. The mixed powder is loaded into a graphite mold and pressed into shape in a cold isostatic press, and the pressure is maintained to obtain a blank.

[0027] A4. Place the billet into a vacuum sintering furnace and sinter at 1200-1600℃, then cool it with the furnace.

[0028] According to a preferred embodiment of the present invention, in step A1, the mass ratio of the matrix material, the reinforcing phase, and the activator is (60-80):(10-20):(5-15); the matrix material is stainless steel powder with a particle size ≤50μm; the reinforcing phase is chopped carbon fiber with a diameter of 5-10μm and a length of 0.1-0.5mm; and the mass ratio of titanium powder to vanadium powder is 1:1.

[0029] According to a preferred embodiment of the present invention, the stainless steel powder is purchased from Xi'an Unite Container Manufacturing Co., Ltd., and is of type 304-50μm, meeting the requirements of particle size ≤50μm, purity ≥99.9%, and oxygen content ≤50ppm.

[0030] According to a preferred embodiment of the present invention, the chopped carbon fiber is purchased from Zhongfu Shenying Carbon Fiber Co., Ltd., model SYT49S-T300, with a diameter of 5-10μm, a length of 0.1-0.5mm, and a tensile strength ≥3.5GPa.

[0031] According to a preferred embodiment of the present invention, the titanium powder is purchased from Baoji Titanium Industry Co., Ltd., with model number TA1, purity ≥99.9%, and particle size ≤45μm.

[0032] According to a preferred embodiment of the present invention, the vanadium powder is purchased from Panzhihua Iron and Steel Group Vanadium Industry Co., Ltd., with model number V-45, purity ≥99.9%, and particle size ≤45μm.

[0033] According to a preferred embodiment of the present invention, the planetary ball mill was purchased from Nanjing Kexi Experimental Instrument Co., Ltd., and its model is QM-3SP4.

[0034] According to a preferred embodiment of the present invention, the argon gas is purchased from Air Liquide (China) Investment Co., Ltd., and is of type AR-99.999% (purity ≥99.999%), and is used as a protective gas for laser welding.

[0035] According to a preferred embodiment of the present invention, the graphite mold is purchased from Shanghai Rongrong New Material Technology Co., Ltd., model GF-99.9, with a purity ≥99.9% and a surface roughness Ra≤0.8μm.

[0036] According to a preferred embodiment of the present invention, the cold isostatic press was purchased from Sichuan Aviation Industry Chengdu Aircraft Industry Integration Technology Co., Ltd., model CIP-500, with a pressure range of 0-1000MPa.

[0037] According to a preferred embodiment of the present invention, in step A2, the ball-to-material ratio in the planetary ball mill is (9-10):1; the mixing speed is 200-400 rpm; and the mixing time is 4-8 h.

[0038] According to a preferred embodiment of the present invention, in step A3, the pressure in the cold isostatic press is 500-1000 MPa, and the pressure holding time is 5-10 min.

[0039] In the planetary ball mill of this invention, agate balls (ball-to-material ratio 9-10:1) continuously collide and grind at a speed of 200-400 rpm. First, the surface of stainless steel powder (particle size ≤50μm) undergoes plastic deformation due to mechanical force, increasing the surface energy and expanding the contact interface with short-cut carbon fibers (diameter 5-10μm, length 0.1-0.5mm) and titanium-vanadium powder (titanium powder to vanadium powder mass ratio 1:1). Under argon protection, although severe oxidation is suppressed, trace amounts of water or oxygen adsorbed on the powder surface undergo weak chemical reactions with titanium and vanadium (such as Ti-OH, V-OH), forming active sites such as surface hydroxyl groups, which enhance the physical adsorption between components. During the cold isostatic pressing stage (500-1000MPa, holding pressure for 5-10min), the high pressure forces the powder particles to undergo plastic flow and mechanical interlocking. The grains of stainless steel powder are embedded into the gaps between carbon fibers through dislocation slip, and the titanium vanadium powder particles fill the interface gaps between stainless steel and carbon fibers, forming a dense green body with a three-dimensional interwoven structure of "metal-ceramic-fiber". The porosity is reduced to below 5%, and the uniformity of component distribution is significantly improved.

[0040] According to a preferred embodiment of the present invention, in step A4, the sintering time is 2-4 h, the heating rate is 5-10 °C / min, and the vacuum degree is ≤10 Pa.

[0041] In this invention, as the temperature rises to the melting point of stainless steel, a liquid stainless steel matrix gradually forms and flows, filling the pores of the billet. Titanium, with a lower melting point than vanadium, melts preferentially. When it comes into contact with the base material (such as the Fe-Si alloy in silicon steel sheets), titanium acts as a strong reducing agent, reacting with oxygen and nitrogen in the molten pool to generate fine, dispersed particles such as TiO2 and TiN, reducing the oxygen content of the molten pool. Subsequently, vanadium melts, reacting with carbon in the molten pool to generate vanadium carbide and with nitrogen to generate vanadium nitride, further purifying the melt and reducing welding defects. Short-cut carbon fibers undergo surface oxidation at this stage due to the high temperature (generating CO and CO2), but incompletely oxidized carbon fibers (retaining some sp)... 2 The hybrid carbon structure forms physical adsorption or weak chemical bonds (such as C-Fe, C-Cr) with elements such as iron and chromium in liquid stainless steel through residual hydroxyl and carboxyl groups on its surface. Its high specific surface area (approximately 500 m²) contributes to this structure. 2 / g) acts as a "heterogeneous nucleation point" in the molten pool, hindering grain growth and merging, and promoting the formation of equiaxed crystals. At the same time, the stainless steel matrix and the base material (such as iron-based alloys) become mutually soluble, forming an Fe-Cr-Ni solid solution (the solubility increases with increasing temperature), which enhances the interfacial bonding strength.

[0042] The beneficial effects of this invention are as follows:

[0043] This invention significantly improves the overall performance of stator-rotor welded joints through pretreatment, application of modified composite materials, and optimization of laser welding parameters. The pretreatment stage employs 800-1200 grit sandpaper grinding combined with acetone / alcohol ultrasonic cleaning to effectively remove oxide layers, oil, and impurities from the surface of the areas to be welded, controlling the surface roughness to Ra≤1.6μm. This avoids bonding defects caused by surface contamination and increases the mechanical interlocking area of ​​the welding interface through appropriate roughening. The coated modified composite material uses stainless steel powder as the matrix, chopped carbon fibers as the reinforcing phase, and titanium vanadium powder as the activator. Its active components undergo a metallurgical reaction with the base material at the high welding temperature, forming a transition layer that enhances the bonding force between the molten pool and the base material. The carbon fibers refine the weld microstructure through bridging, further improving the joint toughness. The introduction of this composite material fundamentally improves the problem of insufficient metallurgical compatibility between the base material and filler materials in traditional welding, providing a high-quality interface foundation for subsequent welding.

[0044] Precise optimization of laser welding parameters effectively controls heat input and molten pool behavior. Setting the laser power to 3-4kW, welding speed to 8-12mm / s, and defocusing distance to +5 to -2mm ensures a stable molten pool temperature of 1800-2200℃, preventing grain coarsening due to excessively high temperatures or incomplete fusion defects caused by excessively low temperatures. High-purity argon gas at a flow rate of 20-25L / min effectively isolates the molten pool from air, reducing porosity. Real-time monitoring with an infrared thermometer ensures uniform molten pool temperature, reducing the tendency for cracking due to localized overheating. Furthermore, post-weld slow cooling at 200-300℃ for 2-4 hours at a rate of 5-10℃ / min releases residual welding stress, reducing the heat-affected zone width by 30-50% compared to traditional processes and decreasing welding deformation by over 50%, significantly improving the dimensional accuracy and structural stability of the stator and rotor.

[0045] By combining the above optimizations, this invention improves the tensile strength and significantly enhances the toughness of the stator-rotor welded joints compared to traditional processes, while effectively suppressing defects such as porosity and cracks. Testing shows that welded joints using this method can withstand higher speeds and loads during motor operation, with reduced heat generation and vibration amplitude, significantly extending the motor's service life. Especially in scenarios with stringent welding quality requirements, such as high-power-density motors and new energy vehicle drive motors, the application of this invention significantly improves the reliability and stability of motor operation, providing key technical support for the lightweight and high-performance development of high-end equipment. Attached Figure Description

[0046] Figure 1 This is an optimized flowchart for the stator and rotor welding process. Detailed Implementation

[0047] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0048] I. Implementation Examples

[0049] Example 1

[0050] This embodiment involves the optimization of the welding process for the stator and rotor, using silicon steel sheets. The stator slot wall thickness is 2mm, and the rotor tooth thickness is 1.8mm. The specific steps are as follows: First, the areas to be welded are pre-treated by using 1000-grit wet sandpaper to evenly grind the areas of the stator slot wall and rotor teeth in the same direction, controlling the grinding force at 0.2-0.3 N / cm. 2 The process continues until the surface oxide layer is removed and the metallic luster is exposed. Then, acetone (analytical grade, purity ≥99.5%) is used as the cleaning agent. The area to be welded is immersed in a beaker containing acetone and ultrasonically cleaned for 12 minutes at room temperature using an ultrasonic cleaner with a frequency of 40kHz and a power of 300W. During the cleaning process, the solution temperature is kept below 30℃. After cleaning, the area is rinsed three times with deionized water, and then ultrasonically cleaned for 5 minutes with anhydrous ethanol (analytical grade, purity ≥99.7%) to remove moisture. Finally, it is dried with nitrogen. The surface roughness of the area to be welded is measured using a surface roughness meter (model TR200, resolution 0.1μm), confirming a roughness value of 1.2μm. Next, a modified composite material is prepared. 304 stainless steel powder (purity ≥99.9%, oxygen content ≤50ppm) with a particle size ≤50μm is weighed at a mass ratio of 70:15:7.5. Short-cut carbon fibers (T300 grade, tensile strength ≥3.5GPa) with a diameter of 6μm and a length of 0.5mm, along with titanium powder and vanadium powder (mass ratio 1:1, purity ≥99.9%, particle size ≤45μm), were added to a planetary ball mill (model QM-3SP4, agate ball diameter 7mm, ball-to-material ratio 9.5:1). The mixture was stirred at 300rpm for 6 hours under argon gas protection (purity ≥99.999%), with the mill stopped every 30 minutes for inspection to prevent material agglomeration. The resulting powder was then placed into a graphite mold (purity ≥99.9%, surface roughness Ra ≤0.8μm) with a diameter of 50mm and a thickness of 10mm. The mixture was then pressed at 750MPa for 7.5 minutes using a cold isostatic press (model CIP-500, pressure range 0-1000MPa) to obtain a density of 2.8g / cm³. 3The preform was placed in a vacuum sintering furnace (model VFS-1200, vacuum degree ≤10Pa) and heated from room temperature to 1300℃ at a rate of 5℃ / min, held for 3 hours, and then demolded after cooling to room temperature in the furnace to obtain the modified composite material. The modified composite material was cut into thin sheets (thickness 0.2mm) with dimensions matching the area to be welded on the rotor teeth using a wire cutting machine (model DK7735, accuracy ±0.02mm). A scraper with a cutting edge width of 1mm and a hardness of HRC60-62 was used to evenly coat the surface to be welded on the rotor teeth. The coating thickness was controlled to 0.2mm using a micrometer (accuracy 0.01mm). After coating, the material was placed in a forced-air drying oven (model DHG-9070A, temperature control accuracy ±2℃) and dried at 100℃ for 1.5 hours. After drying, the surface of the composite material was free of cracks and bubbles. A fiber laser welding device (model IPG YLS-4000, laser wavelength 1064nm, beam quality M) was used. 2 Welding was performed on surfaces ≤1.2) with a laser power of 3.5kW, a welding speed of 10mm / s, and a defocusing distance of +2mm (i.e., the laser focus was located 2mm above the surface to be welded). The shielding gas was argon with a purity ≥99.999%, and the flow rate was controlled at 22L / min using a mass flow meter (model D07-19, accuracy ±0.5%). During the welding process, an infrared thermometer (model FLIR SC7000, response time 10μs) was used to monitor the molten pool temperature in real time. The molten pool temperature was stabilized at 2000℃ by adjusting the welding speed. Immediately after welding, the workpiece was placed in a box-type holding furnace (model RJX-45-13, temperature control accuracy ±5℃) and held at 250℃ for 2.5h. Then, it was cooled to room temperature at a rate of 7.5℃ / min. Throughout the process, a K-type thermocouple (accuracy ±0.5℃) was used to monitor the furnace temperature in real time.

[0051] Example 2

[0052] The preparation method is the same as in Example 1, except that the stator and rotor are made of copper conductor bars and silicon steel sheets. The pretreatment is carried out by polishing with 800-grit sandpaper and ultrasonic cleaning with acetone for 10 min, with a surface roughness Ra = 1.5 μm. The modified composite material formula is 60g stainless steel powder, 10g short-cut carbon fiber, 5g titanium powder, and 5g vanadium powder. The mixture is ball-milled (ball-to-material ratio 9:1, speed 200 rpm, time 4 h), cold isostatically pressed at 500 MPa for 5 min, sintered for 2 h (heating to 1200℃ at 5℃ / min), with a thickness of 0.1 mm. The mixture is dried at 80℃ for 1 h. Laser parameters: power 2kW, speed 5mm / s, defocusing amount +5mm, argon flow rate 15L / min, melt pool temperature 1800℃. After welding, the mixture is held at 200℃ for 2 h and cooled at 5℃ / min.

[0053] Example 3

[0054] The preparation method is the same as in Example 1, except that the stator and rotor are permanent magnets and silicon steel sheets. The pretreatment is carried out by polishing with 1200-grit sandpaper and ultrasonic cleaning with alcohol for 15 min, with a surface roughness Ra = 1.1 μm. The modified composite material formula is 80g stainless steel powder, 20g short-cut carbon fiber, 15g titanium powder + 15g vanadium powder, ball milling (ball-to-material ratio 10:1, speed 400 rpm, time 8h), cold isostatic pressing at 1000MPa for 10 min, sintering for 4h (heating to 1600℃ at 7.5℃ / min), the thickness of the modified composite material is 0.3mm, and drying at 120℃ for 2h. Laser parameters: power 5kW, speed 15mm / s, defocusing amount -2mm, argon flow rate 30L / min, melt pool temperature 2200℃. After welding, the temperature is held at 300℃ for 4h and cooled at 10℃ / min.

[0055] Implement column 4

[0056] The preparation method is the same as in Example 1, except that the welding process of the stator (made of 45 steel) and rotor (made of gray cast iron) is optimized. The specific steps are as follows: During pretreatment, the area to be welded is polished with 1150-grit sandpaper until there is no obvious oxide layer on the surface, and ultrasonically cleaned with acetone for 12 minutes, with a surface roughness Ra = 1.25 μm; the modified composite material is prepared by taking stainless steel powder, short-cut carbon fiber, titanium powder and vanadium powder (mass ratio 1:1) in a mass ratio of 78:18:8 and mixing them in a planetary ball mill (ball material) The rotor was pressed at 600 MPa for 8 minutes using a cold isostatic press (9:1 ratio, 300 rpm, 6 hours) to form a billet. The billet was then sintered at 1400℃ for 3 hours in a vacuum sintering furnace. A 0.2 mm thick layer of modified composite material was coated onto the rotor's welding surface and dried at 100℃ for 1.5 hours. Laser welding was performed at a power of 3 kW, a speed of 8 mm / s, a decoking depth of +3 mm, an argon flow rate of 20 L / min, and a molten pool temperature of 1900℃. After welding, the rotor was held at 250℃ for 3 hours and then cooled to room temperature at a rate of 5℃ / min.

[0057] Comparative Example 1

[0058] The preparation method is the same as in Example 1, except that the pretreatment is only polished with 1000-grit sandpaper (without ultrasonic cleaning), and the surface roughness Ra = 3.0 μm.

[0059] Comparative Example 2

[0060] The preparation method is the same as in Example 1, except that the modified composite material is not coated, and laser welding is performed directly on the pretreated surface to be welded.

[0061] Comparative Example 3

[0062] The preparation method is the same as in Example 1, except that after welding, slow cooling is not performed, and the material is directly air-cooled to room temperature.

[0063] II. Performance Testing

[0064] The performance of the welded joints of Examples 1-4 and Comparative Examples 1-3 was tested using the following methods:

[0065] 1. Joint tensile strength test: Prepare specimens according to GB / T 2651-2021 "Metallic materials welds tensile test method". The specimen size is 150mm long × 20mm wide × 3mm thick (cut along the longitudinal direction of the weld). Use an electronic universal testing machine (model: Instron 5967, load accuracy ±0.5%) to perform tensile tests at a loading rate of 1mm / min. Record the maximum breaking load and calculate the tensile strength of the joint (σb = maximum load / original cross-sectional area of ​​the specimen).

[0066] 2. Microstructure observation: The sample was cut, ground, and polished along the weld cross-section until the surface roughness Ra ≤ 0.5 μm. It was then etched with a 4% nitric acid alcohol solution for 15-20 s. The microstructure of the weld center, fusion zone, and heat-affected zone was observed using a scanning electron microscope (model: ZEISSGemini300, accelerating voltage 5kV, magnification 500-2000x). The grain size was statistically analyzed (the average size of 100 grains was measured using ImageJ software).

[0067] 3. Molten pool temperature stability test: An infrared thermal imager (model: FLIR T440sc, temperature range 500-3000℃, accuracy ±2℃) was used to record the surface temperature field of the molten pool in real time during the welding process. Data was collected at a sampling frequency of 100Hz, and the temperature fluctuation range of the molten pool (ΔT = highest temperature - lowest temperature) and the stabilization time (duration of temperature fluctuation ≤ ±50℃) were calculated.

[0068] 4. Residual Stress Test: The residual stress on the weld surface was measured using an X-ray diffractometer (model: Bruker D8 Advance, Cu target Kα radiation, wavelength 0.15406 nm, scan step 0.02°) with the tilt-fixed ψ method (ψ = 0°, 30°, 45°). The stress was determined based on sin... 2 The magnitude and direction of the principal stresses are calculated using the ψ method, and the average value of the three measuring points is taken as the residual stress value.

[0069] 5. Corrosion resistance test: Neutral salt spray test (NSS) was conducted according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". The test chamber (model: Q-LAB QFog SSP-600) was set at 35℃, the NaCl solution concentration was 5% (mass fraction), and the pH was 6.5-7.2. After continuous spraying for 240 hours, the sample was taken out, rinsed with deionized water and dried. The corrosion weight loss (Δm = initial mass - post-corrosion mass) was measured, and the corrosion rate (v = Δm / (S×t), where S is the sample surface area and t is the test time) was calculated.

[0070] 6. Performance test results:

[0071] Table 1: Performance test results of each embodiment and comparative example

[0072]

[0073]

[0074] As can be seen from Table 1, by comparing the performance test data of Examples 1-4 and Comparative Examples 1-3, it can be seen that the stator and rotor welding process optimization method of the present invention effectively solves the problems of insufficient joint strength, coarse grains in the heat-affected zone, large deformation and porosity cracks in traditional stator and rotor welding. Its core lies in improving the microstructure deterioration caused by thermo-mechanical coupling through multi-dimensional technology improvement system and enhancing the metallurgical compatibility between the filler material and the base material.

[0075] In traditional stator and rotor welding, the thermo-coupling effect (high welding temperature and cooling contraction) often leads to abnormally large grains in the heat-affected zone due to rapid heating and cooling (e.g., grains in Comparative Example 2 reach 28.0 μm). Simultaneously, the filler material and base material suffer from weak metallurgical bonding due to compositional differences or interface contamination (e.g., surface roughness Ra = 3.0 μm in Comparative Example 1), resulting in defects such as porosity and cracks at the interface. Ultimately, this manifests as insufficient joint strength (only 410 MPa in Comparative Example 1). Furthermore, thermal stress concentration (the residual stress in Comparative Example 3 is tensile stress of 20-40 MPa) further exacerbates deformation and crack propagation. This invention addresses the aforementioned problems one by one through the following mechanisms: First, meticulous pretreatment (e.g., in Example 1, 1000-grit sandpaper polishing + acetone ultrasonic cleaning resulted in a surface roughness Ra = 1.2 μm) significantly reduced the roughness of the surface to be welded (Comparative Example 1 had Ra = 3.0 μm), reduced interfacial oxides and contaminants, and enhanced the mechanical and metallurgical bonding between the filler material and the base material, avoiding weak bonding caused by interfacial contamination (Comparative Example 1 had a bonding strength of only 410 MPa). Second, the introduction of modified composite materials (containing chopped carbon fibers and Ti and V activators) refined the grain size of the heat-affected zone through the grain-refining effect of carbon fibers (the grain size in Example 1 was only 12.5 μm, much smaller than the 28.0 μm in Comparative Example 2). Simultaneously, the Ti and V activators promoted the diffusion and metallurgical reaction of interfacial elements, forming a more stable transition layer, thus resolving the metallurgical incompatibility problem caused by compositional differences between the filler material and the base material. Third, laser parameter optimization (such as 3.5kW power, 10mm / s speed, and +2mm defocusing in Example 1) combined with real-time infrared monitoring (temperature fluctuation ±30℃, far lower than ±50℃ in Comparative Example 3) precisely controlled the molten pool temperature and heat input, reduced thermal stress concentration, and suppressed grain coarsening and crack initiation caused by drastic temperature fluctuations. Finally, the post-weld slow cooling process (Example 1 used 250℃ holding for 2.5h + 7.5℃ / min cooling) allowed thermal stress to be slowly released through plastic deformation (residual stress was -80 to -120MPa compressive stress), avoiding crack propagation caused by tensile stress (Comparative Example 3 had tensile stress of 20-40MPa due to air cooling, which easily led to cracking), while also reducing the amount of deformation.

[0076] In summary, this invention comprehensively solves the core defects in traditional stator and rotor welding caused by thermal coupling-induced microstructural degradation and poor metallurgical compatibility of filler materials through pretreatment to enhance interface cleanliness and activity, optimized metallurgical bonding of composite materials, parameter control to suppress thermal damage, and slow cooling to release stress. This significantly improves the joint strength (up to 585 MPa in Example 1) and corrosion resistance (corrosion rate of only 0.8 mg / (dm³) in Example 1). 2 •h)) and dimensional stability (Example 1: molten pool temperature fluctuation ±30℃, deformation is controllable).

[0077] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An optimization method for stator and rotor welding process, characterized in that, Includes the following steps: S1. Pre-treat the stator and rotor parts to be welded by sanding with sandpaper and then ultrasonically cleaning with acetone or alcohol. The surface roughness of the parts to be welded after cleaning is Ra≤1.6μm. S2, the modified composite material is coated onto one of the surfaces to be welded, and the coated surface is placed in an oven to dry; S3 uses laser welding equipment for welding, with the laser power set to 2-5kW, the welding speed to 5-15mm / s, the defocusing amount to +5 to -2mm, the shielding gas to be argon, and the flow rate to be 15-30L / min. During the welding process, the temperature of the molten pool is monitored in real time by an infrared thermometer, and the temperature of the molten pool is 1800-2200℃. The preparation steps of the modified composite material include: A1, Weigh out the matrix material, reinforcing phase and activator, wherein the activator is a mixture of titanium powder and vanadium powder; A2, add the weighed matrix material, reinforcing phase and activator from step A1 into a planetary ball mill, use agate balls as the grinding medium, and mix under argon protection; A3. The mixed powder is loaded into a graphite mold and pressed into shape in a cold isostatic press, and the pressure is maintained to obtain a blank. A4. Place the billet in a vacuum sintering furnace and sinter at 1200-1600℃, then cool it with the furnace. In step A1, the mass ratio of the matrix material, reinforcing phase, and activator is (60-80):(10-20):(5-15); the matrix material is stainless steel powder with a particle size ≤50μm; the reinforcing phase is chopped carbon fiber with a diameter of 5-10μm and a length of 0.1-0.5mm; and the mass ratio of titanium powder to vanadium powder is 1:

1.

2. The method for optimizing the stator and rotor welding process according to claim 1, characterized in that, In step S1, the sandpaper has a grit size of 800-1200 mesh, and the ultrasonic cleaning time is 10-15 minutes.

3. The method for optimizing the stator and rotor welding process according to claim 1, characterized in that, In step S2, the thickness of the modified composite material is 0.1-0.3 mm, the drying temperature in the oven is 80-120℃, and the drying time is 1-2 h.

4. The method for optimizing the stator and rotor welding process according to claim 1, characterized in that, In step S3, the laser power is 3-4kW; the welding speed is 8-12mm / s; and the flow rate is 20-25L / min.

5. The method for optimizing the stator and rotor welding process according to claim 1, characterized in that, The optimization method for the stator and rotor welding process further includes: after welding, the weldment is immediately placed in a heat preservation furnace for slow cooling treatment. The heat preservation temperature is set to 200-300℃ and the heat preservation time is 2-4h. Then, it is cooled to room temperature at a rate of 5-10℃ / min.

6. The method for optimizing the stator and rotor welding process according to claim 1, characterized in that, In step A2, the ball-to-material ratio in the planetary ball mill is (9-10):1; the mixing speed is 200-400 rpm; and the mixing time is 4-8 h.

7. The method for optimizing the stator and rotor welding process according to claim 1, characterized in that, In step A3, the pressure in the cold isostatic press is 500-1000 MPa, and the holding time is 5-10 min.

8. The method for optimizing the stator and rotor welding process according to claim 1, characterized in that, In step A4, the sintering time is 2-4 hours, the heating rate is 5-10℃ / min, and the vacuum degree is ≤10Pa.

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