Friction stir welding seam quality inspection method

Abstract

The invention relates to a friction stir welding seam quality inspection method, which is characterized in that by analyzing elements and components of an aluminum alloy raw material, mixed acid exists in a Kailer reagent, and the mixed acid can chemically react with aluminum and silicon elements in the aluminum alloy, that is, the welding boundary of friction stir welding can be clearly displayed. Aiming at friction stir welding quality control requirements of parts such as a new energy automobile motor shell and the like, the problem of accurately guaranteeing the depth and quality of a welding seam is solved, effective welding seam quality inspection and molten pool center offset inspection are realized through an innovative detection method, the strength of the motor shell is improved, cracking and cooling liquid outflow caused by the welding seam problem are reduced, and the welding quality of the motor shell is improved. And the vehicle cannot run normally due to short circuit of the motor stator and rotor.

Description

Technical fields:

[0001] This invention belongs to the field of new energy vehicle parts manufacturing, and specifically relates to a method for inspecting the quality of friction stir welds. Background technology:

[0002] In the manufacturing of components such as motor housings for new energy vehicles, friction stir welding (FSW) is gradually being adopted due to its advantages in solid-state joining. As the core component of the electric drive system, the performance of the motor housing directly affects the reliability of the entire vehicle. Consequently, quality control for the new FSW process has become more stringent. Simply relying on calipers for depth comparison is far from sufficient. Developing weld pool detection technology to identify incomplete fusion at the interface and weld surface quality, and to achieve effective management of production process data, is urgently needed. However, achieving accurate weld measurement requires destructive processing of the product, increasing inspection costs and hindering quality control. Furthermore, processing planed products requires the use of reagents to reveal the outline; however, conventional methods using 0.5% hydrofluoric acid solvent fail to produce a clear outline. Summary of the Invention:

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for inspecting the quality of friction stir welds.

[0004] The objective of this invention is achieved through the following technical solution: a method for inspecting the quality of friction stir welds, characterized by comprising the following steps:

[0005] A. Sampling: Take a workpiece of friction stir welding and cut a sample along the vertical direction of the weld to ensure that it includes the weld, heat-affected zone and base material. The size should be controlled within 10mm×10mm×15mm to ensure the integrity of microstructure analysis.

[0006] B. Grinding: Use 80#, 400# and 800# sandpaper in sequence to coarsely grind the sample surface to make it flat and the scratches are in one direction, laying the foundation for metallographic observation;

[0007] C. Corrosion treatment: Keller's reagent is selected. The cotton swab is moistened and wiped evenly on the surface to be tested. The wiping is repeated 5 to 6 times and then left to stand. The standing time is 30 seconds ≤ T ≤ 60 seconds. Through the element and composition analysis of aluminum alloy raw materials, Keller's reagent contains mixed acid. This mixed acid can react chemically with aluminum and silicon elements in aluminum alloy, which can clearly show the welding boundary of friction stir welding.

[0008] D. Contour curve formation: After the sample is etched, it is leveled and corrected under a microscope; the sample contour is automatically identified by constructing 3 points on the same horizontal line.

[0009] E. Inspection: Weld inspection steps:

[0010] e1. Prepare the equipment:

[0011] Optical microscope: Select a low-magnification objective lens of 0.5X or 0.7X, which is suitable for observing the overall morphology of the weld.

[0012] Calibrate the scale: Ensure the microscope is equipped with a measuring scale or software measurement function;

[0013] Sample fixation: Place the weld sample stably on the stage and adjust the focus to make the image clear;

[0014] e2. Observe the overall morphology of the weld:

[0015] Macroscopic morphology: Observe the defects of the weld, such as the continuity of the weld, surface smoothness, presence of cracks, porosity, and undercut;

[0016] Heat-affected zone: Inspect the microstructure changes in the transition area between the weld and the base metal;

[0017] e3. Measure the weld dimensions:

[0018] Weld offset dimension: According to the set offset distance, an axial detection line is generated and compared with the center line formed by the test sample to generate data, namely the offset dimension of the weld.

[0019] Molten pool depth: According to the different requirements of each project, the effective depth is set as a measurement segment, and after verification and confirmation, the dimensional results are output.

[0020] e4. Recording and Analysis:

[0021] Photo archiving: Use a microscope and its accompanying camera to photograph the weld morphology and mark key dimensions;

[0022] Data comparison: Compare the measurement results with the process requirements to determine whether they are qualified;

[0023] Based on the theoretical standards established in the early stages of different projects, comparative charts are generated to compare and analyze the detection graphics and scale results, confirm the changes in offset, and form continuous monitoring.

[0024] A further improvement of the present invention is that, when sampling, if it is necessary to observe the cross-section, the weld seam needs to be cut, ground, and polished to avoid measurement errors.

[0025] A further improvement of the present invention is that, when observing with a microscope, the light source angle can be adjusted to within 5 Lux and a darkroom atmosphere can be created to enhance the clarity of the weld outline.

[0026] A further improvement of the present invention is that: after the product completes the friction stir welding process, the weld quality and the offset of the molten pool center are detected. In order to improve the measurement accuracy, the same block surface is measured three times, and the test results are obtained by equalizing the data from the three measurements, which serve as the basis for judgment.

[0027] A further improvement of the present invention is as follows: offset of the center of the molten pool: draw a vertical line at the junction of the friction weld, draw a 1mm parallel line to the right at the lower end of the vertical line, draw another vertical line at the end of the 1mm line, and connect the two vertical lines with a parallel line to obtain the offset of the center of the molten pool.

[0028] A further improvement of the present invention is that the depth of the weld pool is the connection between the highest and lowest points of the weld.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. This invention requires no complex equipment, has strong operational controllability, and can accurately measure the depth and width of friction stir welds, quantifying the data;

[0031] 2. Real-time feedback on welding quality, optimization of welding process, improvement of product reliability, adaptation to the high-quality and mass production needs of new energy vehicles, and provision of key quality assurance means for the in-depth application of friction stir welding technology in the automotive industry;

[0032] 3. The main purpose of this invention is to use Keller's reagent to verify the time, which can clearly show the boundary contour, accurately locate the measured curve, and use a microscope to automatically correct the measurement through three-point measurement to obtain the measurement method of the weld depth and molten pool depth of friction stir welding. Attached image description:

[0033] Figure 1 After the sample is processed, adjust the sample block and draw a schematic diagram of the horizontal line at the bottom of the sample.

[0034] Figure 2 This diagram illustrates how to draw two parallel lines on a sample block, calculate the average value of the two parallel lines, and then connect the line segments with the average values ​​using a perpendicular line.

[0035] Figure 3 Draw a vertical line at the joint of the friction stir weld. Offset the lower end of the vertical line according to the product technical specifications. After offsetting, draw a vertical line at the end of the line according to the offset dimension. Finally, connect the two vertical lines with parallel lines to output a schematic diagram of the corresponding weld size. Detailed implementation method:

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Elements and features described in one embodiment of the present invention can be combined with elements and features shown in one or more other embodiments. It should be noted that, for clarity, representations and descriptions of components and processes unrelated to the present invention and known to those skilled in the art are omitted in the description. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] A method for inspecting the quality of friction stir welds includes the following steps:

[0038] A. Sampling: Take a sample from the friction stir welded workpiece and cut it along the direction perpendicular to the weld to ensure that it includes the weld, heat-affected zone and base material. The size should be controlled within 10mm×10mm×15mm to ensure the integrity of the microstructure analysis. If it is necessary to observe the cross section when sampling, the weld should be cut, ground and polished to avoid measurement errors.

[0039] B. Grinding: Use 80#, 400# and 800# sandpaper in sequence to coarsely grind the sample surface to make it flat and the scratches are in one direction, laying the foundation for metallographic observation;

[0040] C. Corrosion Treatment: Use Keller's reagent. Moisten a cotton swab and wipe the surface to be tested evenly. Repeat the wiping motion 5-6 times, then allow it to stand for 30 seconds ≤ T ≤ 60 seconds. The test procedure is as follows:

[0041]

[0042] D. Contour curve formation: After the sample is etched, it is leveled and corrected under a microscope; by constructing 3 points on the same horizontal line, the contour of the sample is automatically identified after leveling and correction; when observing with a microscope, the light source angle can be adjusted within 5 Lux and a dark room atmosphere can be created to enhance the clarity of the weld contour.

[0043] E. Inspection: Weld inspection steps:

[0044] e1. Prepare the equipment:

[0045] Optical microscope: Select a low-magnification objective lens of 0.5X or 0.7X, which is suitable for observing the overall morphology of the weld.

[0046] Calibrate the scale: Ensure the microscope is equipped with a measuring scale or software measurement function, such as metallographic analysis software;

[0047] Sample fixation: Place the weld sample stably on the stage and adjust the focus to make the image clear;

[0048] e2. Observe the overall morphology of the weld:

[0049] Macroscopic morphology: Observe the defects of the weld, such as the continuity of the weld, surface smoothness, presence of cracks, porosity, and undercut;

[0050] Heat-affected zone: Inspect the microstructure changes in the transition area between the weld and the base metal;

[0051] e3. Measure the weld dimensions:

[0052] Weld offset dimension: According to the set offset distance (e.g., 1mm), an axial detection line is generated and compared with the center line formed by the test sample to generate data, i.e., the offset dimension of the weld.

[0053] Melt pool depth: According to the different requirements of each project, the effective depth is set as a measurement segment. After verification and confirmation, the dimensional result is output. The connection between the highest and lowest points of the weld is the molten pool depth.

[0054] Molten pool center offset: Draw a vertical line at the friction weld joint, and draw a 1mm parallel line to the right from the lower end of the vertical line. Draw another vertical line at the end of the 1mm line. Connect the two vertical lines with the parallel line to get the molten pool center offset.

[0055] e4. Recording and Analysis:

[0056] Photo archiving: Use a microscope and its accompanying camera to photograph the weld morphology and mark key dimensions;

[0057] Data comparison: Compare the measurement results with process requirements (such as ISO 5817, AWSD1.1, etc.) to determine whether they are qualified;

[0058] Based on the theoretical standards established in the early stages of different projects, comparative charts are generated to compare and analyze the detection graphics and scale results, confirm the changes in offset, form continuous monitoring, and facilitate the optimization and improvement of the production process.

[0059] After the friction stir welding process is completed, the weld quality and the offset of the weld pool center are inspected. To improve measurement accuracy, three measurements are performed on the same sample surface, and the test results are calculated by averaging the data from the three measurements, serving as the basis for judgment. If more precise microstructure analysis is required, the magnification can be switched to a higher level (e.g., 50X–1000X) to observe the grain structure. Using an optical microscope (0.5X or 0.7X), the overall morphology of the weld is observed, and the weld width and depth are measured.

[0060] This invention addresses the quality control requirements of friction stir welding for components such as motor housings in new energy vehicles, solving the problem of accurately ensuring weld depth and quality. Through innovative testing methods, it achieves effective weld quality inspection, improves the strength of the motor housing, and reduces cracking caused by weld problems, coolant leakage, and short circuits in the motor stator and rotor that could prevent the vehicle from operating normally.

[0061] Finally, it should be noted that although the present invention and its advantages have been described in detail above, it should be understood that various changes, substitutions, and modifications can be made without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the invention is not limited to the specific embodiments of the processes, apparatus, means, methods, and steps described in the specification. Those skilled in the art will readily understand from the disclosure of this invention that existing and future processes, apparatus, means, methods, or steps that perform substantially the same function or obtain substantially the same results as the corresponding embodiments described herein can be used according to the present invention. Therefore, the appended claims are intended to include such processes, apparatus, means, methods, or steps within their scope.

Claims

1. A method for inspecting the quality of friction stir welds, characterized in that: Includes the following steps: A. Sampling: Take a workpiece of friction stir welding and cut a sample along the vertical direction of the weld to ensure that it includes the weld, heat-affected zone and base material. The size should be controlled within 10mm×10mm×15mm to ensure the integrity of microstructure analysis. B. Grinding: Use 80#, 400# and 800# sandpaper in sequence to coarsely grind the sample surface to make it flat and the scratches are in one direction, laying the foundation for metallographic observation; C. Corrosion treatment: Use Keller's reagent, moisten a cotton swab, wipe the surface to be tested evenly, repeat the wiping back and forth 5 to 6 times, and then let it stand. Standing time: 30 seconds ≤ T ≤ 60 seconds. D. Contour curve formation: After the sample is etched, it is leveled and corrected under a microscope; by constructing 3 points on the same horizontal line, the sample contour is automatically identified after leveling and correction. E. Inspection: Weld inspection steps: e1. Prepare equipment: Optical microscope: Select a low-magnification objective lens of 0.5X or 0.7X, which is suitable for observing the overall morphology of the weld. Calibrate the scale: Ensure the microscope is equipped with a measuring scale or software measurement function; Sample fixation: Place the weld sample stably on the stage and adjust the focus to make the image clear; e2. Observe the overall morphology of the weld: Macroscopic morphology: Observe the defects of the weld, such as the continuity of the weld, surface smoothness, presence of cracks, porosity, and undercut; Heat-affected zone: Inspect the microstructure changes in the transition area between the weld and the base metal; e3. Measure the weld dimensions: Weld offset dimension: According to the set offset distance, an axial detection line is generated and compared with the center line formed by the test sample to generate data, namely the offset dimension of the weld. Molten pool depth: According to the different requirements of each project, the effective depth is set as a measurement segment, and after verification and confirmation, the dimensional results are output. e4. Recording and Analysis: Photo archiving: Use a microscope and its accompanying camera to photograph the weld morphology and mark key dimensions; Data comparison: Compare the measurement results with the process requirements to determine whether they are qualified; Based on the theoretical standards established in the early stages of different projects, comparative charts are generated to compare and analyze the detection graphics and scale results, confirm the changes in offset, and form continuous monitoring.

2. The method for inspecting the quality of friction stir welds according to claim 1, characterized in that: When taking samples, if it is necessary to observe the cross-section, the weld should be cut, ground, and polished to avoid measurement errors.

3. The method for inspecting the quality of friction stir welds according to claim 1, characterized in that: When observing with a microscope, the light source angle can be adjusted within 5 Lux and a darkroom atmosphere can be created to enhance the clarity of the weld outline.

4. The method for inspecting the quality of friction stir welds according to claim 1, characterized in that: After the product completes the friction stir welding process, the weld quality and the offset of the molten pool center are tested. To improve the accuracy of the measurement, the same block surface is measured three times. The test results are obtained by averaging the data from the three measurements and used as the basis for judgment.

5. The method for inspecting the quality of friction stir welds according to claim 4, characterized in that: Molten pool center offset: Draw a vertical line at the friction weld joint, and draw a 1mm parallel line to the right from the lower end of the vertical line. Draw another vertical line at the end of the 1mm line. Connect the two vertical lines with the parallel line to get the molten pool center offset.

6. The method for inspecting the quality of friction stir welds according to claim 1, characterized in that: Melt pool depth: The depth of the weld pool is the connection between the highest and lowest points of the weld.

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