Pretreatment method before detection of weld penetration and weld width of laser welding bead of lithium battery

Abstract

The invention discloses a lithium battery laser welding bead penetration depth and width detection pretreatment method, which comprises the following steps of: cutting a to-be-detected sample bead position to expose a bead section, and obtaining a pole column bead sample and an aluminum shell bead sample; weld bead sections of the pole column weld bead sample and the aluminum shell weld bead sample are polished; soaking the pole welding bead sample and the aluminum shell welding bead sample in a chemical reagent, or performing electrolytic polishing on the pole welding bead sample and the aluminum shell welding bead sample; and cleaning and drying. According to the method, corrosion or electrolytic polishing treatment is conducted on the grinding surface of the welding bead through the chemical reagent, an oxide layer and impurities on the metal surface can be removed, the surface smoothness can be improved, the brightness and reflectivity of the metal surface can be improved, the microstructure of the welding bead can be clearly displayed, parameters such as the penetration depth and the penetration width can be analyzed conveniently, and the welding quality can be evaluated conveniently; and the accuracy of measurement and calibration of the fusion depth and the fusion width is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a pretreatment method for detecting the weld penetration and width of laser welds in lithium batteries. Background Technology

[0002] Laser welding of the positive and negative electrode connecting pieces of the aluminum shell and cover plate is a crucial step in lithium battery production, and the welding quality directly affects battery quality. Therefore, it is necessary to measure the width and depth of the weld bead after laser welding during production. Based on the width and depth of the weld bead, the rationality of process parameters is determined, and these parameters are adjusted during production as a reference to ensure battery quality. However, the reliability of currently advanced online weld penetration detection systems is still under development and optimization. Due to limitations in macroscopic sampling methods, it is impossible to effectively separate mesoscopic signals with weld penetration characteristics from other interfering signals (such as radiation signals from the keyhole inner wall), resulting in a low proportion of effective signals in the detection data and increased difficulty in extracting weld penetration information. Furthermore, existing data analysis methods struggle to effectively handle complex and drastically fluctuating mesoscopic signals, making weld penetration feature extraction difficult.

[0003] Patent CN114812426A describes treating the aluminum casing welding area of ​​a battery with 5%-8% dilute nitric acid before testing the welding depth. Patent CN117259976B employs a signal preprocessing method that superimposes data over a period of time and then homogenizes it. This method accurately obtains trend-based characteristic data within that time period, effectively ignoring the interference caused by rapid fluctuations in keyhole depth on weld penetration detection, and enabling effective judgment of the welding penetration trend.

[0004] However, in the current production process, the welding inspection at the battery cell end is quite complicated. The real-time weld depth monitoring results of the entire welding trajectory cannot be used as a basis for judging the normal flow of products. Therefore, it is necessary to manually perform longitudinal cutting tests on the weld after welding. Thus, it is very necessary to use simple, intuitive and quick methods to measure the weld depth and width, characterize the effect after laser welding, and explore the weld pretreatment method before the weld depth test. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a pretreatment method for detecting the weld penetration and width of laser welding in lithium batteries. This method can remove the oxide layer and impurities on the metal surface, improve surface smoothness, increase the brightness and reflectivity of the metal surface, and improve the accuracy of weld penetration and width measurement calibration.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a pretreatment method for detecting the weld penetration and width of laser welds in lithium batteries, which includes the following steps: S1. Cut the weld bead at the weld bead position of the sample to be tested to expose the weld bead cross section and obtain the pole weld bead sample and the aluminum shell weld bead sample; S2. Grind the weld cross-section of the pole weld sample and the peripheral weld sample; S3. Immerse the electrode weld sample and the aluminum shell weld sample in a chemical reagent or perform electrolytic polishing; clean and dry.

[0007] Etching time control: Different reagents and weld beads require different etching times, and the appropriate etching time needs to be determined through experiments. If the etching time is too short, the microstructure will not be clearly displayed; if the etching time is too long, it will lead to over-etching of the microstructure, affecting the observation results.

[0008] As a further improvement to the above-mentioned solution of the present invention, the grinding in step S2 is to first use a rubber stopper to grind the longitudinal section of the weld bead with 500# or 1000# sandpaper, which can quickly and easily obtain a weld bead sample of aluminum electrode tab with uniform thickness, consistent surface scratch direction, and clear display of the copper-aluminum composite material joint. Then, an MP-2B grinding and polishing machine is used for fine grinding, using 1500# sandpaper, setting the speed to 500 rpm, and grinding the longitudinal section of the weld bead perpendicular to the grinding disc until the surface is smooth and free of burrs.

[0009] As a further improvement of the above-mentioned solution of the present invention, when the electrode of the sample to be tested is a copper electrode, the electrode weld sample is immersed in a chemical reagent for 180~300s, wherein the chemical reagent is selected from one of FeCl3 solution, a mixture of nitric acid and ethanol, and a mixture of ammonia and hydrogen peroxide.

[0010] For copper electrodes: When using FeCl3 solution, the iron ions in the ferric chloride can undergo a displacement reaction with copper, dissolving the copper and forming copper ions. Simultaneously, it corrodes the weld bead structure, highlighting the microstructure. It is often used for deeper corrosion of copper weld beads to observe more detailed microstructure. However, it is important to control the reaction time to avoid over-corrosion. In a mixture of nitric acid and ethanol, nitric acid, with its strong oxidizing properties, reacts chemically with copper, dissolving some of its components. This creates a contrast between the weld bead and the base metal structure, clearly revealing the microstructure. It is a commonly used reagent, effective for corroding most copper and copper alloy weld beads, and relatively simple and safe to operate. In a mixture of ammonia and hydrogen peroxide, hydrogen peroxide has strong oxidizing properties and can oxidize the copper surface, while ammonia can act as a complexing agent, stabilizing the reaction products and allowing the reaction to continue. This enables the corrosion display of the weld structure. For some copper alloy welds containing special elements (such as nickel and zinc), this reagent can better display their microstructure characteristics. However, safety precautions should be taken when using it because hydrogen peroxide has certain corrosiveness and instability.

[0011] As a further improvement to the above-described scheme of the present invention, the concentration of the FeCl3 solution is 10%~40%; And / or, the mixture of nitric acid and ethanol is generally prepared by nitric acid (HNO3) and ethanol (mass fraction of 95%-98%), with a volume ratio of nitric acid to ethanol of 1:5, 1:10 or 4:96, etc. And / or, the mixture of ammonia and hydrogen peroxide is usually made by mixing ammonia and hydrogen peroxide in a certain proportion, for example, the volume ratio of ammonia to hydrogen peroxide is 1:1, and an appropriate amount of deionized water may also be added for dilution.

[0012] As a further improvement of the above-mentioned solution of the present invention, when the electrode of the sample to be tested is an aluminum electrode, the electrode weld sample is immersed in a chemical reagent for 60-180 seconds. The chemical reagent is selected from NaOH solution, or a mixture of hydrochloric acid, nitric acid and deionized water, or a mixture of picric acid, hydrochloric acid, ethanol and deionized water.

[0013] As a further improvement to the above-mentioned solution of the present invention, the aluminum shell weld sample is immersed in a chemical reagent for 60-180 seconds. The chemical reagent is selected from NaOH solution, or a mixture of hydrochloric acid, nitric acid and deionized water, or a mixture of picric acid, hydrochloric acid, ethanol and deionized water.

[0014] For aluminum electrodes and aluminum shells: Sodium hydroxide reacts chemically with aluminum, dissolving it and generating sodium aluminate and hydrogen gas, thus corroding the weld bead structure. It is suitable for observing weld bead structures of pure aluminum and some specific aluminum alloys. However, the corrosion effect may be poor for aluminum alloys with high silicon content; therefore, it is important to control the concentration and time to prevent excessive corrosion. In a mixture of hydrochloric acid, nitric acid, and deionized water, hydrochloric acid undergoes a displacement reaction with aluminum, while the oxidizing properties of nitric acid help remove surface impurities and oxide layers, making the structure clearer. It has a good corrosion effect on some aluminum alloy weld bead structures containing copper, magnesium, and other alloying elements. However, ventilation is important during use to avoid inhaling harmful gases. A mixture of picric acid, hydrochloric acid, ethanol, and deionized water selectively corrodes certain phases in aluminum alloys, causing different phases to exhibit different colors and contrasts, facilitating observation and analysis of the microstructure. It is often used to analyze the phase composition and microstructure of aluminum alloy weld bead structures and is of great significance for studying the welding performance of aluminum alloys. However, it is important to note that picric acid has a certain degree of toxicity, and caution must be exercised during operation.

[0015] As a further improvement to the above-described scheme of the present invention, the concentration of the NaOH solution is 5%~10%; And / or, in the mixture of hydrochloric acid, nitric acid and deionized water, the volume ratio of hydrochloric acid, nitric acid and deionized water is 2:1~3:2~3; And / or, in the mixture of picric acid, hydrochloric acid, ethanol and deionized water, the mass-to-volume ratio of picric acid, hydrochloric acid, ethanol and deionized water is 1g:3~5mL:45~50mL:45~50mL.

[0016] After the electrode weld bead samples and aluminum shell weld bead samples have been soaked in chemical reagents, they need to be cleaned with deionized water or alcohol and dried to avoid reagent residue affecting subsequent observation.

[0017] As a further improvement to the above-mentioned solution of the present invention, the electropolishing is performed using a mixture of perchloric acid and anhydrous ethanol as the electropolishing solution and an electropolishing machine.

[0018] As a further improvement to the above-mentioned solution of the present invention, liquid nitrogen or dry ice is added to the electrolytic polishing solution to control the temperature of the electrolytic polishing solution to -10~-20℃.

[0019] As a further improvement to the above-mentioned solution of the present invention, the mass percentage of perchloric acid in the electrolytic polishing solution is 10%~15%.

[0020] As a further improvement to the above-mentioned solution of the present invention, for the aluminum electrode post and aluminum shell, the parameters for electrolytic polishing are: voltage of 15~20V, and current density maintained at 0.5A / cm². 2 Optimal polishing time is 30-60 seconds, and the area of ​​the weld bead section exposed in the electrolytic polishing solution is 0.5-1 cm². 2 For copper electrodes, the electropolishing parameters are: voltage of 15~20V, and current density maintained at 0.5A / cm². 2 Optimal polishing time is 60-180 seconds, and the area of ​​the weld bead section exposed in the electrolytic polishing solution is 0.5-1 cm². 2 After polishing, remove the electrode weld sample and the aluminum shell weld sample, rinse them with cold water, and then dry them in a drying oven.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention uses chemical reagents to corrode or electropolish the weld bead's ground surface, removing oxide layers and impurities from the metal surface, improving surface smoothness, increasing the brightness and reflectivity of the metal surface, clearly displaying the weld bead's microstructure, facilitating the analysis of parameters such as weld penetration and weld width, and evaluating welding quality, thereby improving the accuracy of weld penetration and weld width measurement and calibration. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the center line marking of the aluminum electrode weld in Example 1; Figure 2This is a schematic diagram of the longitudinal section of the aluminum electrode weld bead in Example 1; Figure 3 This is a photograph of the aluminum electrode weld bead after chemical treatment in Example 1; Figure 4 Metallographic image of the aluminum electrode weld bead in Example 1; Figure 5 Metallographic image of the weld bead around the aluminum cover plate in Example 2; Figure 6 Metallographic image of the aluminum electrode weld bead in Example 3; Figure 7 Metallographic image of the aluminum electrode weld bead in Example 4; Figure 8 Metallographic image of the copper electrode weld bead in Example 5; Figure 9 Metallographic image of the copper electrode weld bead in Example 6; Figure 10 Metallographic image of the copper electrode weld bead in Example 7; Figure 11 Metallographic image of the aluminum electrode weld bead in Example 8; Figure 12 Metallographic image of the copper electrode weld bead in Example 9. Detailed Implementation

[0023] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0025] Example 1 This embodiment takes the treatment of aluminum electrode weld beads with NaOH solution as an example to perform pretreatment before detecting the penetration depth and penetration width of lithium battery laser weld beads, including the following steps: Take the laser-welded battery cover plate, locate the weld bead on the aluminum electrode post. The weld bead is circular. Mark the center line of this circle. Figure 1 As shown.

[0026] Place the battery cover plate into the metallographic cutting machine, align the aluminum electrode weld bead with the cutting wheel of the metallographic cutting machine, and start the metallographic cutting machine to cut the battery cover plate vertically, resulting in the following: Figure 2 The longitudinal section of the weld bead is shown.

[0027] Using a rubber stopper to grind the longitudinal section of the weld with 500# sandpaper can quickly and easily obtain a weld sample of aluminum tab with uniform thickness, consistent surface scratch direction, and clear visibility of the copper-aluminum composite material joint. Then, use an MP-2B grinding and polishing machine for fine grinding, select 1500# sandpaper, set the speed to 500 rpm, and grind the longitudinal section of the weld perpendicular to the grinding disc until the surface is smooth and burr-free.

[0028] Sodium hydroxide and deionized water were mixed in a beaker at a mass ratio of 1:9 to obtain a sodium hydroxide solution. The polished aluminum electrode sample was then immersed in the sodium hydroxide solution for 60 seconds. If the molten pool was not clear after 60 seconds, the sample was continued to be immersed in the sodium hydroxide solution until the molten pool became clear.

[0029] After removing the aluminum electrode sample, clean it with alcohol and then blow-dry it until the sample surface is matte. Figure 3 As shown.

[0030] The weld penetration and weld width corresponding to the aluminum electrode post were tested and calibrated using a two-dimensional microscope. Figure 4 The metallographic diagram shown is from Figure 4 The weld pool after welding is clearly visible, and the microstructure of the weld bead is clearly displayed, indicating a good processing effect. The weld penetration is the depth of the formed weld pool (e.g., point BD), and the weld width is the width of the weld pool from left to right (e.g., point AC). The distance measured from the weld pool depth is the weld penetration, and it is determined whether this value is within the standard range. Similarly, the distance measured from the weld width is used to determine whether it is within the standard range.

[0031] Example 2 The difference between this embodiment and Embodiment 1 is that in this embodiment, NaOH solution is used to treat the weld bead around the aluminum cover plate; the results are obtained using a two-dimensional microscope. Figure 5 The metallographic diagram shown is from Figure 5 The weld pool is clearly visible after welding, and the microstructure of the weld bead is clearly displayed, indicating a good processing effect. The longitudinal depth and transverse width are marked, and the two values ​​are judged to be qualified according to the standard.

[0032] Example 3 The difference between this embodiment and Embodiment 1 is that the aluminum electrode weld bead is treated with a mixture of hydrochloric acid, nitric acid, and deionized water, with a volume ratio of 2:1:3; the results are obtained using a two-dimensional microscope as shown below. Figure 6 The metallographic image of the weld bead shown is from Figure 6 The weld pool is clearly visible after welding, and the microstructure of the weld bead is clearly displayed, indicating a good processing effect. The longitudinal depth and transverse width are marked, and the two values ​​are judged to be qualified according to the standard.

[0033] Example 4 The difference between this embodiment and Embodiment 1 is that the aluminum electrode weld bead is treated with a mixture of picric acid, hydrochloric acid, ethanol, and deionized water, with a mass-to-volume ratio of picric acid, hydrochloric acid, ethanol, and deionized water of 1g:5mL:45mL:50mL; the results were obtained using a two-dimensional microscope as shown below. Figure 7 The metallographic image of the aluminum electrode weld bead shown is from... Figure 7 The weld pool is clearly visible after welding, and the microstructure of the weld bead is clearly displayed, indicating a good processing effect. The longitudinal depth and transverse width are marked, and the two values ​​are judged to be qualified according to the standard.

[0034] Example 5 The difference between this embodiment and Embodiment 1 is that the copper electrode weld bead is treated with FeCl3 solution at a concentration of 0.25 g / mL for 300 seconds; the results are obtained using a two-dimensional microscope as follows: Figure 8 The metallographic image of the weld bead shown is from Figure 8 The weld pool is clearly visible after welding, and the microstructure of the weld bead is clearly displayed, indicating a good processing effect. The longitudinal depth and transverse width are marked, and the two values ​​are judged to be qualified according to the standard.

[0035] Example 6 The difference between this embodiment and Embodiment 1 is that the copper electrode weld bead is treated with a mixture of nitric acid and ethanol, with a volume ratio of nitric acid to ethanol of 1:5 and an immersion time of 300 seconds; the results are obtained using a two-dimensional microscope as shown below. Figure 9 The metallographic image of the weld bead shown is from Figure 9 The weld pool is clearly visible after welding, and the microstructure of the weld bead is clearly displayed, indicating a good processing effect. The longitudinal depth and transverse width are marked, and the two values ​​are judged to be qualified according to the standard.

[0036] Example 7 The difference between this embodiment and Embodiment 1 is that: the copper electrode weld bead is treated with a mixture of ammonia and hydrogen peroxide, with a volume ratio of ammonia to hydrogen peroxide of 1:1, and the immersion time is 300 seconds; the results are obtained using a two-dimensional microscope as shown below. Figure 10 The metallographic image of the weld bead shown is from Figure 10 The weld pool is clearly visible after welding, and the microstructure of the weld bead is clearly displayed, indicating a good processing effect. The longitudinal depth and transverse width are marked, and the two values ​​are judged to be qualified according to the standard.

[0037] Example 8 This embodiment takes the electrolytic polishing of aluminum electrode weld seams as an example, and performs pre-processing before detecting the weld penetration depth and width of lithium battery laser weld seams, including the following steps: Take the laser-welded battery cover plate, locate the weld bead on the aluminum electrode post. The weld bead is circular, and mark the center line of the circle.

[0038] Place the battery cover plate into the metallographic cutting machine, align the aluminum electrode weld bead with the cutting wheel of the metallographic cutting machine, and start the metallographic cutting machine to cut the battery cover plate vertically to obtain the longitudinal section of the weld bead.

[0039] Using a rubber stopper to grind the longitudinal section of the weld with 500# sandpaper can quickly and easily obtain a weld sample of aluminum tab with uniform thickness, consistent surface scratch direction, and clear visibility of the copper-aluminum composite material joint. Then, use an MP-2B grinding and polishing machine for fine grinding, select 1500# sandpaper, set the speed to 500 rpm, and grind the longitudinal section of the weld perpendicular to the grinding disc until the surface is smooth and burr-free.

[0040] A mixture of perchloric acid and ethanol was used as the electropolishing solution, with the perchloric acid comprising 15% by mass. An electropolishing machine was used, and liquid nitrogen was added to the solution to achieve sub-zero temperatures. The aluminum electrode weld sample was then fixed in place, ensuring the polished area was larger than the etched hole. The panel displayed the temperature as "External cooling," the mode as "PolishingOnly," the "Electrolyte" setting as "A2," and the area as "1 / 2."

[0041] Polishing parameters: Voltage selected is 15V, current density is maintained at 0.5A / cm². 2 The polishing time was 50 seconds, and the area of ​​the weld bead section exposed in the electrolytic polishing solution was 1 cm². 2 .

[0042] The weld penetration and weld width corresponding to the aluminum electrode post were tested and calibrated using a two-dimensional microscope. The results obtained using the two-dimensional microscope are shown below. Figure 11 The metallographic image of the weld bead shown is from Figure 11 It can be seen that the weld track forms a clear molten pool after processing, which can clearly show the microstructure of the weld bead. The processing effect is good. The longitudinal depth and transverse width are marked, and the two values ​​are judged to be qualified according to the standard.

[0043] Example 9 The difference between this embodiment and Embodiment 8 is that this embodiment involves electrolytic polishing of the copper electrode post, with the following polishing parameters: voltage selected as 15V, and current density maintained at 0.5A / cm². 2 The polishing time was 150 seconds, and the area of ​​the weld bead section exposed in the electrolytic polishing solution was 1 cm². 2 ; obtained through a two-dimensional microscope, such as Figure 12 The metallographic image of the weld bead shown is from Figure 12It can be seen that the weld track forms a clear molten pool after processing, which can clearly show the microstructure of the weld bead. The processing effect is good. The longitudinal depth and transverse width are marked, and the two values ​​are judged to be qualified according to the standard.

[0044] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] The embodiments described above are merely illustrative 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 invention patent. 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 all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A pretreatment method for detecting the weld penetration depth and width in laser welding of lithium batteries, characterized in that, It includes the following steps: S1. Cut the weld bead at the weld bead position of the sample to be tested to expose the weld bead cross section and obtain the pole weld bead sample and the aluminum shell weld bead sample; S2. Grind the weld cross-section of the pole weld sample and the peripheral weld sample; S3. Immerse the electrode weld sample and the aluminum shell weld sample in a chemical reagent or perform electrolytic polishing; clean and dry.

2. The pretreatment method for detecting weld penetration depth and width in lithium battery laser welding according to claim 1, characterized in that, When the electrode of the sample to be tested is a copper electrode, the electrode weld sample is immersed in a chemical reagent for 180-300 seconds. The chemical reagent is selected from one of FeCl3 solution, a mixture of nitric acid and ethanol, or a mixture of ammonia and hydrogen peroxide.

3. The pretreatment method for detecting weld penetration depth and width in lithium battery laser welding according to claim 2, characterized in that, The concentration of the FeCl3 solution is 10%~40%; And / or, in the mixture of nitric acid and ethanol, the volume ratio of nitric acid to ethanol is 1~4:5~96, and the concentration of ethanol is 95%~98%; And / or, in the mixture of ammonia and hydrogen peroxide, the volume ratio of ammonia to hydrogen peroxide is 1:

1.

4. The pretreatment method for detecting weld penetration depth and width in lithium battery laser welding according to claim 1, characterized in that, When the electrode of the sample to be tested is an aluminum electrode, the electrode weld sample is immersed in a chemical reagent for 60-180 seconds. The chemical reagent is NaOH solution, or a mixture of hydrochloric acid, nitric acid and deionized water, or a mixture of picric acid, hydrochloric acid, ethanol and deionized water.

5. The pretreatment method for detecting weld penetration depth and width in lithium battery laser welding according to claim 1, characterized in that, The aluminum shell weld sample is immersed in a chemical reagent for 60-180 seconds. The chemical reagent may be NaOH solution, or a mixture of hydrochloric acid, nitric acid and deionized water, or a mixture of picric acid, hydrochloric acid, ethanol and deionized water.

6. The pretreatment method for detecting weld penetration depth and width in lithium battery laser welding according to claim 4 or 5, characterized in that, The concentration of the NaOH solution is 5%~10%; And / or, in the mixture of hydrochloric acid, nitric acid and deionized water, the volume ratio of hydrochloric acid, nitric acid and deionized water is 2:1~3:2~3; And / or, in the mixture of picric acid, hydrochloric acid, ethanol and deionized water, the mass-to-volume ratio of picric acid, hydrochloric acid, ethanol and deionized water is 1g:3~5mL:45~50mL:45~50mL.

7. The pretreatment method for detecting weld penetration depth and width in lithium battery laser welding according to claim 1, characterized in that, The electropolishing process uses a mixture of perchloric acid and anhydrous ethanol as the electropolishing solution and an electropolishing machine for electropolishing.

8. The pretreatment method for detecting weld penetration depth and width in lithium battery laser welding according to claim 7, characterized in that, The temperature of the electrolytic polishing solution is -10 to -20°C.

9. The pretreatment method for detecting weld penetration depth and width in lithium battery laser welding according to claim 7, characterized in that, In the electrolytic polishing solution, the mass percentage of perchloric acid is 10%~15%.

10. The pretreatment method for detecting weld penetration depth and width in lithium battery laser welding according to claim 7, characterized in that, The parameters for the electropolishing are: voltage 15~20V, current density 0.5A / cm². 2 The polishing time is 30-180 seconds, and the area of ​​the weld cross-section exposed in the electrolytic polishing solution is 0.5-1 cm². 2 .

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