Sample preparation method for observing magnetic domain of cutting line of oriented silicon steel and application of sample preparation method

Abstract

The invention provides a sample preparation method for oriented silicon steel cutting line magnetic domain observation and application of the sample preparation method, and belongs to the field of metal material detection. The method comprises the following steps: cutting an oriented silicon steel sample to obtain a first sample; distinguishing a nicked surface and a non-nicked surface of the first sample, and coating the nicked surface with protective glue to retain stress information and a magnetic domain structure of the nicked surface so as to obtain a second sample; removing the inorganic salt coating on the non-indented surface of the second sample to obtain a third sample; the non-nicking surface of the third sample is sequentially subjected to SiC abrasive paper preliminary grinding, silicon dioxide suspension mechanical polishing and perchloric acid electrolytic polishing, so that the surface smoothness of the non-nicking surface is improved, a stress influence area at the nicking line of the nicking surface is reserved, and the to-be-observed sample is obtained. Through linear cutting sampling, nick surface protection and fine polishing of a non-nick surface, stress information and a magnetic domain structure of a nick line of a sample can be reserved, and magnetic domain information near and inside the nick line can be observed.

Description

Technical Field

[0001] The present application relates to the technical field of metal material detection, and in particular to a sample preparation method for observing magnetic domains of oriented silicon steel score lines and its application. Background Art

[0002] Grain-oriented silicon steel is a key soft magnetic material widely used in electrical equipment such as transformers and motors. Its magnetic properties are influenced by the material's internal magnetic domain structure. Laser scribing, as an important method for refining the magnetic domain width, can effectively reduce iron loss and increase magnetic permeability. Studying the magnetic domain morphology at the laser-scored site is crucial for optimizing the scribing process.

[0003] Currently, the main methods for observing magnetic domains include the powder texture method and scanning electron microscopy (SEM) imaging. While simple to use, the powder texture method suffers from low resolution, and magnetic particles are easily affected by stray magnetic fields near the score line, preventing visualization of the magnetic domains within the score line. Furthermore, it is unable to quantitatively measure key parameters such as the score line width. In contrast, SEM FSD (Forescatter diffuse) imaging offers significant advantages in magnetic domain research due to its high resolution and excellent magnetic domain contrast. However, conventional SEM sample preparation methods easily remove the stress layer near the score line during the electropolishing process, making it impossible to accurately observe the magnetic domain structure in this area, limiting in-depth research on the score effect. Summary of the Invention

[0004] The present application provides a sample preparation method for observing magnetic domains of the score lines of oriented silicon steel and its application to solve the following technical problem: how to retain the stress information and magnetic domain structure of the score lines of oriented silicon steel samples during the electron microscope sample preparation process to observe the magnetic domain information near and inside the score lines.

[0005] In a first aspect, an embodiment of the present application provides a sample preparation method for observing magnetic domains of oriented silicon steel score lines, the method comprising: Cutting the oriented silicon steel sample by wire cutting to obtain a first sample with a set size; Distinguishing the scored surface and the non-scored surface of the first sample, and applying a protective glue on the scored surface to preserve the stress information and magnetic domain structure of the scored surface, thereby obtaining a second sample; wherein the protective glue is AB glue or 502 glue; removing the inorganic salt coating on the non-scored surface of the second sample to obtain a third sample; and The non-grooved surface of the third sample was subjected to preliminary grinding with SiC sandpaper, mechanical polishing with silica suspension, and electrolytic polishing with perchloric acid in sequence to improve the surface finish of the non-grooved surface and retain the stress-affected zone at the groove line of the grooved surface, thereby obtaining a sample to be observed for observing the magnetic domains of the groove lines of oriented silicon steel.

[0006] Optionally, removing the inorganic salt coating on the non-scored surface of the second sample to obtain a third sample comprises: first immersing the second sample in dilute hydrochloric acid to remove the inorganic salt coating on the non-scored surface of the second sample; soaking the second sample after the first soaking in a sodium bicarbonate solution for a second time to remove residual dilute hydrochloric acid; The second sample after the second immersion is washed to obtain a third sample.

[0007] Optionally, the volume fraction of the dilute hydrochloric acid is 8% to 10%, and the first immersion time is 3.5 hours to 4.5 hours; and / or, The volume fraction of the sodium bicarbonate solution is 4% to 6%, and the second soaking time is 8 minutes to 12 minutes.

[0008] Optionally, the step of sequentially performing SiC sandpaper preliminary polishing, silicon dioxide suspension mechanical polishing, and perchloric acid electrolytic polishing on the non-notched surface of the third sample comprises: Using SiC sandpaper, the non-scratched surface of the third sample was preliminarily polished to reduce the surface roughness; the mesh number of the SiC sandpaper was 3000 mesh; The non-grooved surface of the third sample after preliminary grinding is mechanically polished using a SiO2 suspension as a polishing medium; the particle size of the SiO2 is 0.04 μm to 0.06 μm; Electrolytically polishing the non-grooved surface of the third sample after mechanical polishing using a perchloric acid solution; the volume fraction of the perchloric acid solution is 5% to 7%; The third sample after electrolytic polishing is cleaned.

[0009] Optionally, the mechanical polishing uses a Naibo LAP-2SE metallographic polishing machine, the polishing cloth for the mechanical polishing is a velvet cloth, the lubricating medium for the mechanical polishing is anhydrous ethanol, and the grinding direction of the mechanical polishing is along the rolling direction of the material.

[0010] Optionally, the rotation speed of the mechanical polishing equipment is 150 rpm / min to 200 rpm / min, and the polishing time of the mechanical polishing is 8 min to 12 min.

[0011] Optionally, the electrolytic polishing includes the following parameters: voltage is 30V, current is 1A to 2A, and polishing time is 10s to 25s.

[0012] In a second aspect, the present application provides an application of a sample preparation method for observing magnetic domains of oriented silicon steel score lines, the application comprising: Using a powder grain method, the non-scored surface of the sample to be observed obtained in any one of the embodiments of the first aspect is used to preliminarily locate the position of the score line on the scored surface; the score line position is transferred to the non-scored surface by the score line stress effect of the scored surface; The FSD magnetic domain imaging at the position of the score line is performed under a scanning electron microscope to obtain a high-resolution FSD magnetic domain image inside the score line.

[0013] Optionally, the application further includes: Combined with an electron backscatter diffraction probe, the magnetic domain image and crystal orientation information inside the score line can be obtained simultaneously.

[0014] Optionally, the FSD magnetic domain imaging includes the following parameters: a sample tilt angle of 70° to 75°, an acceleration voltage of 30 kV, a working distance of 14 mm to 16 mm, and a distance between the FSD probe and the sample surface of 150 mm.

[0015] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art: An embodiment of the present application provides a sample preparation method for observing magnetic domains of oriented silicon steel score lines, the method comprising: cutting an oriented silicon steel sample by wire cutting to obtain a first sample; distinguishing the score surface and the non-score surface of the first sample, and coating the score surface with a protective glue to retain the stress information and magnetic domain structure of the score surface to obtain a second sample; removing the inorganic salt coating on the non-score surface of the second sample to obtain a third sample; and sequentially performing preliminary polishing with SiC sandpaper, mechanical polishing with a silica suspension, and electrolytic polishing with perchloric acid on the non-score surface of the third sample to improve the surface finish of the non-score surface and retain the stress-affected zone at the score line of the score surface to obtain a sample to be observed for observing magnetic domains of oriented silicon steel score lines. First, sampling through wire cutting can reduce local internal stress at the cutting point and improve sample integrity; second, by protecting the notched surface, the stress information near the notched line can be retained, ensuring the integrity of the magnetic domain structure and improving the authenticity of magnetic domain imaging; third, by fine polishing the non-notched surface, the smoothness of the non-notched surface can be improved, ensuring that the magnetic domain structure is clear and discernible, and realizing fine observation of the magnetic domain structure; finally, the notched line of the notched surface is transferred to the non-notched surface through the stress effect, so that the magnetic domain information near and inside the notched line can be observed on the non-notched surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 A schematic flow chart of a sample preparation method for observing magnetic domains of oriented silicon steel score lines provided in an embodiment of the present application; Figure 2 Magnetic domain morphology diagram of the grooved surface and the non-grooved surface under the powder grain method provided in Example 1 of the present application; Figure 3 This is a sample morphology diagram after applying a protective layer of AB glue on the scored surface of the sample provided in Example 1 of the present application; Figure 4 This is a morphological diagram of the sample provided in Example 1 of the present application after pickling to remove the inorganic salt coating on the non-grooved surface of the sample; Figure 5 This is a sample morphology diagram after the non-grooved surface of the sample is polished with 3000-grit sandpaper provided in Example 1 of the present application; Figure 6 This is a sample morphology diagram of the non-grooved surface of the electrolytically polished sample provided in Example 1 of the present application; Figure 7 The magnetic domain morphology of the sample to be observed provided in Example 1 of the present application at different positions of the inscription. The white dotted box is the magnetic domain inside the inscription line, and the length of the arrow is the width of the laser inscription; Figure 8 The magnetic domain morphology and corresponding crystal orientation information diagram of the sample to be observed provided in Example 1 of the present application; Figure 9 This is a diagram of the magnetic domain morphology and corresponding crystal orientation information of the sample to be observed provided in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0019] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0020] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0021] In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be a single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationships discussed herein, the parameters that need to be described by ratio should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substances A, B, and C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0022] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0023] like Figure 1As shown, the present application provides a sample preparation method for observing magnetic domains of oriented silicon steel score lines, the method comprising: S11, cutting the oriented silicon steel sample by wire cutting to obtain a first sample with a set size; The embodiment of the present application adopts wire cutting to sample the oriented silicon steel sample. Compared with mechanical shearing, wire cutting can significantly reduce the local internal stress at the cutting point and improve the integrity of the sample.

[0024] In some embodiments, the set size includes: a length of the first sample is 5 mm to 15 mm, and a width of the first sample is 5 mm to 15 mm.

[0025] The sampling area depends on the requirements of the electron microscope sample stage and can generally be 5 mm×5 mm to 15 mm×15 mm.

[0026] S12, distinguishing the scored surface and the non-scored surface of the first sample, and applying a protective glue on the scored surface to preserve the stress information and magnetic domain structure of the scored surface, to obtain a second sample; the protective glue is AB glue or 502 glue; In the embodiment of the present application, AB glue or 502 glue is coated on the notched surface to protect the inorganic coating and the notched line on the notched surface during the pickling process, while avoiding erosion during electrolytic polishing, thereby preserving the stress information and magnetic domain structure of the notched surface.

[0027] In the embodiment of the present application, the scored surface and the non-scored surface are distinguished by the powder texture method. The scored surface feels raised when touched, and the powder texture method observes that the magnetic particles are strongly aggregated near the scored line.

[0028] It should be noted that the "powder texture method" reveals the magnetic domain structure by applying fine magnetic powder to the surface of a magnetized sample. After the silicon steel sheet is magnetized by an external magnetic field, the fine magnetic particles are affected by the local magnetic field on the sample surface and align along the boundaries of the magnetic domains or magnetic lines of force, thereby revealing the sample's magnetic domain distribution and structure to the naked eye or a low-magnification microscope.

[0029] AB glue is a common organic adhesive. Glue A is the main component, primarily epoxy resin (such as bisphenol A epoxy resin), and Glue B is the curing agent, primarily polyamide. To use AB glue, mix the two in a 1:1 ratio and apply evenly to the sample surface. After curing for 24 hours, an adhesive layer will form on the sample surface.

[0030] In the adhesive layer formed by the AB glue, the epoxy resin forms a rigid structure after curing, resisting corrosion from pickling (such as 9% dilute hydrochloric acid) and electrolytic polishing (6% perchloric acid solution), effectively protecting the inorganic coating on the notched surface and the notched lines from corrosion. Furthermore, the AB glue forms a uniform insulating layer after curing, isolating the notched surface from the effects of external mechanical stress, preserving the original stress distribution in the notched area and preventing distortion of the magnetic domain structure due to stress perturbations. Furthermore, epoxy resin has strong adhesion to metal substrates (such as silicon steel) and low cure shrinkage, preventing deformation of the notched lines or coating peeling due to adhesive layer shrinkage.

[0031] 502 glue is an instant-curing adhesive with α-ethyl cyanoacrylate as its main ingredient. It is called "universal glue" because of its fast bonding ability and wide applicability.

[0032] S13, removing the inorganic salt coating on the non-scored surface of the second sample to obtain a third sample; It should be noted that the inorganic salt coating of oriented silicon steel is an insulating protective layer mainly composed of inorganic components, which is mainly used to improve the electromagnetic properties, corrosion resistance and processing adaptability of the material.

[0033] In some embodiments, removing the inorganic salt coating on the non-scored surface of the second sample to obtain a third sample comprises: The second sample is first immersed in dilute hydrochloric acid to remove the inorganic salt coating on the non-grooved surface of the second sample; the second sample after the first immersion is second immersed in sodium bicarbonate solution to remove residual dilute hydrochloric acid; the second sample after the second immersion is cleaned to obtain a third sample.

[0034] In some embodiments, the volume fraction of the dilute hydrochloric acid is 8% to 10%, and the first soaking time is 3.5 hours to 4.5 hours; and / or, The volume fraction of the sodium bicarbonate solution is 4% to 6%, and the second soaking time is 8 minutes to 12 minutes.

[0035] The embodiment of the present application uses a dilute hydrochloric acid solution to remove the inorganic salt coating on the non-grooved surface. Compared with mechanical polishing, this method can effectively avoid additional polishing stress, thereby obtaining a higher quality magnetic domain image. In addition, the sample needs to be cleaned with a sodium bicarbonate solution to neutralize the residual acid, prevent material corrosion, and prepare for subsequent fine polishing. For example, the volume fraction of dilute hydrochloric acid can be 8%, 8.5%, 9%, 9.5%, 10%, etc., the time for the first immersion can be 3.5h, 3.7h, 3.9h, 4.1h, 4.3h, 4.5h, etc., the volume fraction of the sodium bicarbonate solution can be 4%, 4.5%, 5%, 5.5%, 6%, etc., and the time for the second immersion can be 8min, 9min, 10min, 11min, 12min, etc.

[0036] S14. The non-notched surface of the third sample is subjected to preliminary grinding with SiC sandpaper, mechanical polishing with silica suspension, and electrolytic polishing with perchloric acid in sequence to improve the surface finish of the non-notched surface and retain the stress-affected zone at the notched line of the notched surface, thereby obtaining a sample to be observed for observing the magnetic domains of the notched line of oriented silicon steel.

[0037] The embodiment of the present application uses AB glue or 502 glue to protect the notched surface, and then polishes the non-notched surface. This avoids the traditional electrolytic polishing to remove the stress layer near the notched line, ensuring the integrity of the magnetic domain structure and improving the authenticity of the magnetic domain imaging.

[0038] In some embodiments, the step of sequentially subjecting the non-grooved surface of the third sample to preliminary polishing with SiC sandpaper, mechanical polishing with a silica suspension, and electrolytic polishing with perchloric acid comprises: The non-grooved surface of the third sample is preliminarily polished using SiC sandpaper to reduce the surface roughness; the mesh size of the SiC sandpaper is 3000 mesh; the non-grooved surface of the third sample after preliminarily polishing is mechanically polished using SiO2 suspension as a polishing medium; the particle size of SiO2 is 0.04μm to 0.06μm; the non-grooved surface of the third sample after mechanical polishing is electrolytically polished using perchloric acid solution; the volume fraction of the perchloric acid solution is 5% to 7%; and the third sample after electrolytic polishing is cleaned.

[0039] In some embodiments, the mechanical polishing uses a Naibo LAP-2SE metallographic polishing machine, the polishing cloth for the mechanical polishing is velvet cloth, the lubricating medium for the mechanical polishing is anhydrous ethanol, and the polishing direction of the mechanical polishing is along the rolling direction of the material.

[0040] In some embodiments, the rotation speed of the mechanical polishing device is 150 rpm / min to 200 rpm / min, and the polishing time of the mechanical polishing is 8 min to 12 min.

[0041] In some embodiments, the electrolytic polishing includes the following parameters: voltage of 30V, current of 1A to 2A, and polishing time of 10s to 25s.

[0042] During the fine polishing process, the non-grooved surface of the sample is first ground using 3000-grit SiC sandpaper to achieve a smooth surface. Subsequently, mechanical polishing is performed using a SiO2 suspension, with the polishing direction aligned with the rolling direction to minimize additional polishing stress and improve the quality of magnetic domain imaging. Finally, electrolytic polishing is performed using a perchloric acid solution, followed by immediate ultrasonic cleaning with alcohol to prevent corrosion from the perchloric acid solution. The non-grooved surface is polished throughout the fine polishing process to preserve the stress-affected zone at the groove line on the grooved surface. For example, the volume fraction of the perchloric acid solution can be 5%, 5.5%, 6%, 6.5%, 7%, etc., the equipment speed of mechanical polishing can be 150rpm / min, 160rpm / min, 170rpm / min, 180rpm / min, 190rpm / min, 200rpm / min, etc., the polishing time of mechanical polishing can be 8min, 9min, 10min, 11min, 12min, etc., the current of electrolytic polishing can be 1A, 1.2A, 1.4A, 1.6A, 1.8A, 2A, etc., and the polishing time of electrolytic polishing can be 10s, 15s, 20s, 22s, 25s, etc.

[0043] In some embodiments, after sequentially subjecting the non-notched surface of the third sample to preliminary polishing with SiC sandpaper, mechanical polishing with a silica suspension, and electrolytic polishing with perchloric acid, the method further comprises: The protective adhesive layer on the scored surface of the third sample is removed.

[0044] In the embodiment of the present application, when the size of the sample is greater than 10 mm × 10 mm, the glue will shrink in volume during curing, which may affect the observation of magnetic domains. Acetone can be used to erase the glue to remove the protective layer.

[0045] Therefore, the embodiment of the present application adopts the method of applying AB glue or 502 glue to protect the scored surface, effectively retaining the coating on the scored surface during the sample preparation process of pickling and removing the coating, thereby retaining the stress information near the score line during the electrolytic polishing process, avoiding the loss of magnetic domains caused by traditional polishing methods. And precisely because the scored surface is protected, the score line effect of the scored surface can be retained during the subsequent electrolytic polishing of the non-scored surface. The score line stress effect of the scored surface can be transmitted through the interior of the material to the non-scored surface, so that the magnetic domain information can be observed on the non-scored surface, and then when observing the magnetic domain, the magnetic domain information near and inside the score line can be observed on the non-scored surface.

[0046] Based on a general inventive concept, the present application provides an application of a sample preparation method for observing magnetic domains of oriented silicon steel score lines, the application comprising: S21. Using a powder grain method, preliminarily locate the position of the score line on the non-scored surface of the sample to be observed obtained in any of the above embodiments; the score line position is transferred to the non-scored surface by the score line stress effect of the scored surface; S22, performing FSD magnetic domain imaging at the position of the score line under a scanning electron microscope to obtain a high-resolution FSD magnetic domain image inside the score line.

[0047] In some embodiments, the application further comprises: Combined with an electron backscatter diffraction probe, the magnetic domain image and crystal orientation information inside the score line can be obtained simultaneously.

[0048] It should be noted that FSD (forward scattered detector) technology is an imaging method used in scanning electron microscopes (SEMs) that primarily constructs images using electrons scattered from a sample. It can reveal magnetic domain information on the sample surface and requires extremely high material surface quality.

[0049] Electron backscatter diffraction (EBSD) is an important technique for microstructural analysis in materials science. It uses a scanning electron microscope (SEM) combined with diffraction patterns to study the crystal structure and orientation of materials.

[0050] In some embodiments, the FSD magnetic domain imaging includes the following parameters: a sample tilt angle of 70° to 75°, an acceleration voltage of 30 kV, a working distance of 14 mm to 16 mm, and a distance between the FSD probe and the sample surface of 150 mm.

[0051] In the examples of this application, the scanning electron microscope (SEM) imaging parameters are optimized, using a tilt angle of 70° to 75°, an accelerating voltage of 30 kV, and a working distance of 14 mm to 16 mm. This not only allows for EBSD information acquisition but also supports the simultaneous observation of magnetic domains and crystal orientation (requiring FSD and EBSD probes). This allows for the combined analysis of magnetic domain and crystal orientation data, providing more accurate microstructural information for studying the stress-affected zone near the score line. For example, the sample tilt angle can be 70°, 71°, 72°, 73°, 74°, 75°, etc., and the working distance can be 14 mm, 15 mm, 16 mm, etc.

[0052] In summary, the embodiments of the present application propose an innovative sample preparation method. Through the steps of wire cutting sampling, AB glue coating to protect the sample score surface (the surface where the score line is located), mechanical polishing, electrolytic polishing, etc., the stress information near the score line is effectively retained to prepare a scanning electron microscope sample for magnetic domain observation. Compared with the traditional powder texture method, this method can not only obtain a high-resolution image of the magnetic domain inside the score line, but also accurately measure microscopic parameters such as the score line width through the magnetic domain image. In addition, combined with the electron backscatter diffraction (EBSD) probe, the magnetic domain image and crystal orientation information can be obtained simultaneously, thereby revealing the microstructural evolution of the stress-affected zone near the score line. This method provides an efficient and accurate experimental means for in-depth research on the microstructure and magnetic properties of oriented silicon steel, and has important technical value for the optimized design and application of oriented silicon steel.

[0053] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0054] Example 1 This embodiment provides a sample preparation method for observing magnetic domains of oriented silicon steel score lines, which may include the following steps: 1. Wire cutting sampling and preliminary observation of magnetic domains ① The oriented silicon steel sample is cut by wire cutting to obtain a first sample; the sampling area depends on the requirements of the electron microscope sample stage. In order to observe the magnetic domains of the scoring line at different positions of the same oriented silicon steel sample, multiple first samples of different sizes are cut.

[0055] ② The powder texture method was used to observe the magnetic domain morphology of the first sample to distinguish the inscribed surface from the non-inscribed surface. The magnetic domain morphology at the inscribed surface can be clearly seen. Figure 2 shown.

[0056] ③ Use AB glue to coat the scratched surface. Take 0.2 ml of A glue and 0.2 ml of B glue respectively. After mixing them evenly, apply them on the scratched surface of the sample and let them stand for 24 hours to solidify to obtain the second sample. The sample morphology after the scratched surface is coated with AB glue protective layer is shown in the figure below. Figure 3 shown.

[0057] 2. Remove the inorganic salt coating on the non-scored surface The second sample was immersed in a 9% dilute hydrochloric acid solution for 3 hours to remove the inorganic salt coating on the non-grooved surface of the sample. The second sample was then taken out and immersed in a 5% sodium bicarbonate solution for 10 minutes to remove the residual dilute hydrochloric acid. Finally, the sample was placed in an alcohol ultrasonic machine for cleaning 2 to 3 times to obtain the third sample. The sample morphology after removing the inorganic salt coating on the non-grooved surface of the sample is shown in the figure below. Figure 4 shown.

[0058] 3. Polishing ① Use 3000 mesh SiC sandpaper to preliminarily grind the non-grooved surface of the third sample to reduce the surface roughness. The sample morphology after sandpaper grinding the non-grooved surface is shown in the figure below. Figure 5 shown.

[0059] ② Mechanical polishing was performed using a Naibo LAP-2SE metallographic polisher, using a SiO2 suspension with a particle size of 0.05 μm. A velvet cloth was used as the polishing cloth, and anhydrous ethanol was used as the lubricant. During the polishing process, the polishing direction should be along the rolling direction of the material, and the machine speed should be controlled at 150 rpm for 10 minutes.

[0060] ③ Use perchloric acid solution (volume fraction 6%) for electrolytic polishing, control voltage 30V, current 1.5A, polishing time 20s, immediately put it into anhydrous ethanol for cleaning, and ultrasonicate for 2min to obtain the sample to be observed for magnetic domain observation of grain-oriented silicon steel score line. The sample morphology after electrolytic polishing of the non-score surface is shown in the figure below. Figure 6 shown.

[0061] 4. Magnetic domain observation after electrolytic polishing ① Observe the magnetic domains of the sample to be observed using the powder texture method. First, prepare the magnetic fluid: weigh 0.3g of commercial ferroferric oxide particles (particle size 800-1000 mesh), dissolve it in 150ml of deionized water, and place it in a rotating water bath for magnetic stirring. Set the stirring speed to 600rpm / min, raise the temperature to 60℃ and keep it warm for 5min. Then, gradually add 10ml of sodium benzenesulfonate activator with a concentration of 0.1mol / L, adjust the stirring speed to 1000rpm / min, and continue to keep it warm for 30 minutes. After the preparation is completed, add the magnetic fluid to the non-grooved surface of the sample to be observed. After standing for 10min, take the magnetic domain image of the powder texture method and record the position of the groove line.

[0062] ② FSD magnetic domain imaging: Magnetic domain imaging is performed using the FSD detector in a scanning electron microscope (SEM). During observation, the sample is tilted within a range of 70° to 75°, the accelerating voltage is set to 30 kV, and the working distance is adjusted to approximately 15 mm. Simultaneously, the distance between the FSD probe and the sample surface is adjusted to 150 mm to obtain high-resolution FSD magnetic domain images, enabling detailed observation of the magnetic domain structure. An EBSD probe can be connected simultaneously to obtain both magnetic domain and crystal orientation information.

[0063] The magnetic domain morphology of the sample to be observed at different positions is shown in the figure Figure 7 As shown, the white dotted box is the magnetic domain inside the scoring line, and the length of the arrow is the width of the laser scoring.

[0064] The magnetic domain morphology and corresponding crystal orientation information of the sample to be observed in Example 1 are shown in FIG. Figure 8 As shown. Figure 8 In the figure, the white dashed line clearly shows the presence of fine comb-like magnetic domains within the laser score, and the scale information provides the width of the score line. This method also produces a high-quality surface, and the inverse pole figure provides information on the crystal orientation.

[0065] Comparative Example 1 This comparative example is modified as follows based on Example 1: In the process of preparing the sample to be observed for observing the magnetic domains of the oriented silicon steel score line, AB glue is not coated on the score surface.

[0066] Comparison 1: The magnetic domain morphology and corresponding crystal orientation information of the sample to be observed are shown in Figure 1. Figure 9 As shown. Figure 9 In the figure, the red box indicates the wedge-shaped magnetic domain near the laser score. Without AB glue to protect the score surface, the added stress from the laser score is almost eliminated due to electropolishing, and the effect of the laser score on the magnetic domain cannot be seen. EBSD crystal orientation information can be obtained from the inverse pole figure.

[0067] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages: In the embodiments of the present application, the stress information of the laser scratches is retained to avoid the loss of magnetic domain information caused by the traditional electrolytic polishing method, thereby ensuring the integrity and authenticity of the magnetic domain structure.

[0068] In the embodiment of the present application, a method of applying AB glue or 502 glue to protect the notched surface is used, which effectively retains the coating on the notched surface during the sample preparation process of pickling and removing the coating, thereby retaining the stress information near the notched line during the electrolytic polishing process, avoiding the magnetic domain loss caused by traditional polishing methods.

[0069] In the examples of this application, the polishing process was optimized, including adjusting the polishing steps and optimizing the polishing solution and electrolyte concentrations to improve polishing quality and make the magnetic domain structure more clearly visible. Using the scanning electron microscope (SEM) FSD imaging mode, high-resolution magnetic domain images can be obtained, and microscopic parameters such as the width of the scribe lines can be accurately measured.

[0070] In the examples of this application, optimized SEM imaging parameters were used, employing a 70° tilt angle, 30 kV accelerating voltage, and a 15 mm working distance. These parameters not only support EBSD acquisition but also enable simultaneous observation of magnetic domains and crystal orientation (requiring FSD and EBSD probes). This allows for combined analysis of magnetic domain and crystal orientation data, providing more accurate microstructural information for studying the stress-affected zone near the score line.

[0071] In the embodiments of the present application, the conventional powder texture method is suitable for magnetic domain observation. The prepared samples can still be used for magnetic domain imaging using the powder texture method and can be compared and analyzed with electron microscope magnetic domain images, thereby enhancing the reliability of magnetic domain research and providing important support for the microstructure optimization and magnetic property analysis of oriented silicon steel.

[0072] In the embodiments of the present application, not only the preparation process of the oriented silicon steel magnetic domain observation sample is optimized, but also the magnetic domain imaging quality is improved. In combination with the crystal orientation information, the application field of magnetic property research is broadened, which has high technical innovation and practical value.

[0073] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A sample preparation method for observing magnetic domains of oriented silicon steel score lines, characterized in that: The method comprises: Cutting the oriented silicon steel sample by wire cutting to obtain a first sample with a set size; Distinguishing the scored surface and the non-scored surface of the first sample, and applying a protective glue on the scored surface to preserve the stress information and magnetic domain structure of the scored surface, thereby obtaining a second sample; wherein the protective glue is AB glue or 502 glue; removing the inorganic salt coating on the non-scored surface of the second sample to obtain a third sample; and The non-grooved surface of the third sample was subjected to preliminary grinding with SiC sandpaper, mechanical polishing with silica suspension, and electrolytic polishing with perchloric acid in sequence to improve the surface finish of the non-grooved surface and retain the stress-affected zone at the groove line of the grooved surface, thereby obtaining a sample to be observed for observing the magnetic domains of the groove lines of oriented silicon steel.

2. The method according to claim 1, characterized in that The step of removing the inorganic salt coating on the non-scored surface of the second sample to obtain a third sample comprises: first immersing the second sample in dilute hydrochloric acid to remove the inorganic salt coating on the non-scored surface of the second sample; soaking the second sample after the first soaking in a sodium bicarbonate solution for a second time to remove residual dilute hydrochloric acid; The second sample after the second immersion is washed to obtain a third sample.

3. The method according to claim 2, characterized in that The volume fraction of the dilute hydrochloric acid is 8% to 10%, and the first soaking time is 3.5 hours to 4.5 hours; and / or, The volume fraction of the sodium bicarbonate solution is 4% to 6%, and the second soaking time is 8 minutes to 12 minutes.

4. The method according to claim 1, wherein The non-grooved surface of the third sample is subjected to SiC sandpaper preliminary polishing, silicon dioxide suspension mechanical polishing, and perchloric acid electrolytic polishing in sequence, comprising: Using SiC sandpaper, the non-scratched surface of the third sample was preliminarily polished to reduce the surface roughness; the mesh number of the SiC sandpaper was 3000 mesh; The non-grooved surface of the third sample after preliminary grinding is mechanically polished using a SiO2 suspension as a polishing medium; the particle size of the SiO2 is 0.04 μm to 0.06 μm; Electrolytically polishing the non-grooved surface of the third sample after mechanical polishing using a perchloric acid solution; the volume fraction of the perchloric acid solution is 5% to 7%; The third sample after electrolytic polishing is cleaned.

5. The method according to claim 4, characterized in that The mechanical polishing uses a Naibo LAP-2SE metallographic polishing machine, the polishing cloth for the mechanical polishing is velvet cloth, the lubricating medium for the mechanical polishing is anhydrous ethanol, and the grinding direction of the mechanical polishing is along the rolling direction of the material.

6. The method according to claim 5, characterized in that The rotation speed of the mechanical polishing equipment is 150 rpm / min to 200 rpm / min, and the polishing time of the mechanical polishing is 8 min to 12 min.

7. The method according to claim 4, characterized in that The electrolytic polishing includes the following parameters: voltage of 30V, current of 1A to 2A, and polishing time of 10s to 25s.

8. An application of a sample preparation method for observing magnetic domains of oriented silicon steel score lines, characterized in that: The applications include: Using a powder grain method, preliminarily locating the position of the score line of the score surface on the non-score surface of the sample to be observed obtained in any one of claims 1 to 7; the score line position is transferred to the non-score surface by the score line stress effect of the score surface; The FSD magnetic domain imaging at the position of the score line is performed under a scanning electron microscope to obtain a high-resolution FSD magnetic domain image inside the score line.

9. The use according to claim 8, characterized in that The application also includes: Combined with an electron backscatter diffraction probe, the magnetic domain image and crystal orientation information inside the score line can be obtained simultaneously.

10. The use according to claim 8, characterized in that The FSD magnetic domain imaging includes the following parameters: the sample tilt angle is 70° to 75°, the acceleration voltage is 30 kV, the working distance is 14 mm to 16 mm, and the distance between the FSD probe and the sample surface is 150 mm.

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