A method for preparing an ebsd sample of oriented silicon steel

Abstract

The application discloses a preparation method of an oriented silicon steel EBSD sample. The preparation method comprises the following steps: firstly, mechanically polishing an oriented silicon steel sample, then electrolytically polishing the sample, and improving a polishing liquid in the electrolytic polishing, and then ultrasonic cleaning, and blowing dry to obtain the oriented silicon steel EBSD sample. The preparation method combines the mechanical polishing with the electrolytic polishing, and especially, the electrolytic polishing liquid formula is designed, so that the sample preparation requirements of different processes of the EBSD sample are achieved, and the detection cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of electron microscopy sample preparation technology, and specifically to a method for preparing an oriented silicon steel EBSD sample. Background Technology

[0002] Electron backscatter diffraction (EBSD) is primarily used for characterizing the microstructure and microtexture of materials. Its main advantage is that it can achieve sub-micron spatial resolution diffraction while retaining the conventional characteristics of scanning electron microscopy. EBSD has revolutionized traditional texture analysis methods and created a completely new scientific field.

[0003] Grain-oriented silicon steel is a widely used soft magnetic alloy, playing an important role in power electronics, machinery, and defense industries. In the research of grain-oriented silicon steel, secondary recrystallization is utilized to develop strong {110}... <001> Goss texture results in excellent magnetic properties along the rolling direction. Therefore, in the production process of grain-oriented silicon steel, factors such as grain structure and size, texture, and orientation have a significant impact on the magnetic properties of the finished product, requiring research and analysis for effective control. EBSD grain orientation microscopic imaging technology links microstructure, micro-area composition, and crystallographic data analysis, enabling quantitative and semi-quantitative studies of the boundary characteristics, micro-area orientation, orientation difference, and microtexture of grain-oriented silicon steel. Therefore, EBSD technology can become an important tool for the research of grain-oriented silicon steel.

[0004] Therefore, obtaining EBSD samples with high calibration rates and applicable to different processes is a problem that needs to be solved in the analysis and research of grain-oriented silicon steel. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing EBSD samples from grain-oriented silicon steel through electrolytic polishing. This invention combines mechanical polishing with electrolytic polishing, and particularly through the design of the electrolytic polishing solution formulation, achieves the sample preparation requirements for EBSD samples at different stages, thereby reducing testing costs.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing an EBSD sample of grain-oriented silicon steel includes the following steps: first, mechanically polishing the grain-oriented silicon steel sample, then electrolytically polishing it, followed by ultrasonic cleaning and drying to obtain the EBSD sample of grain-oriented silicon steel; wherein the grain-oriented silicon steel sample is obtained by hot rolling, decarburization annealing, single cold rolling, or double cold rolling.

[0008] Furthermore, the mechanical polishing involves hot-mounting the oriented silicon steel sample, followed by grinding and polishing to obtain a oriented silicon steel sample with a mirror finish.

[0009] Furthermore, the material used for thermal embedding is a black conductive thermal embedding material.

[0010] Furthermore, the polishing process is carried out by sequentially polishing with sandpaper of 240 grit, 400 grit, 800 grit, 1200 grit and 2000 grit.

[0011] Furthermore, the polishing agent is a diamond spray polishing agent, specifically W1.5 or W2.5; the surface roughness of the mirror-finished oriented silicon steel is ≤0.16μm.

[0012] Furthermore, the voltage for electropolishing is 10–30V; the current is 0.15–0.65A; the temperature is 20–28℃; the pump speed is 800–1200 r / min; and the electropolishing time is 15–40 s.

[0013] Furthermore, the polishing solution used in the electropolishing is composed of methanol, glycerol, acetylacetone and tetramethylammonium chloride; the volume ratio of methanol, glycerol, acetylacetone and tetramethylammonium chloride is (420-780):(54-200):(45-120):(5.1-25.7).

[0014] Furthermore, the tetramethylammonium chloride is in powder form, and its volume is determined by the relationship between mass, volume, and density; the density of tetramethylammonium chloride is 1.17 g / cm³. 3

[0015] Furthermore, the glycerol is replaced with ethylene glycol or 1,3-propanediol.

[0016] Further, the polishing solution is prepared by: taking tetramethylammonium chloride and dissolving it in methanol according to the volume ratio of methanol, glycerol, acetylacetone and tetramethylammonium chloride of (420-780):(54-200):(45-120):(5.1-25.7), then adding acetylacetone and glycerol in sequence, mixing evenly to obtain the polishing solution.

[0017] Further, the polishing solution is prepared by: taking tetramethylammonium chloride and dissolving it in methanol according to the volume ratio of methanol, ethylene glycol, acetylacetone and tetramethylammonium chloride of (420-780):(54-200):(45-120):(5.1-25.7), then adding acetylacetone and ethylene glycol in sequence, mixing evenly to obtain the polishing solution.

[0018] Further, the polishing solution is prepared by: taking tetramethylammonium chloride and dissolving it in methanol according to the volume ratio of methanol, 1,3-propanediol, acetylacetone and tetramethylammonium chloride of (420-780):(54-200):(45-120):(5.1-25.7), then adding acetylacetone and 1,3-propanediol in sequence, mixing evenly to obtain the polishing solution.

[0019] An EBSD sample of oriented silicon steel prepared by the aforementioned preparation method.

[0020] In the polishing solution used in this invention, acetylacetone and tetramethylammonium chloride are mainly used to reduce surface stress of the sample, polish the sample surface to remove scratches, and also corrode grain boundaries. Methanol and glycerol act as solvents and promote ion movement, thus improving the electrolysis effect. In the comparative example of this invention, acetylacetone and tetramethylammonium chloride were dissolved solely in methanol. Experiments showed that the electrolysis time was significantly prolonged, resulting in excessive immersion time of the sample in the electrolyte, a severe decrease in sample surface gloss, and affecting subsequent observation. This invention replaces part of the methanol with glycerol to promote electrolysis, reduce electrolysis time, and improve sample gloss.

[0021] The EBSD samples prepared by the electropolishing solution used in this invention have a calibration rate that is more than 2 points higher than that of samples prepared by conventional electropolishing solutions on hot-rolled and decarburized materials, and a calibration rate that is more than 10 points higher for samples prepared by first-roll and second-roll materials.

[0022] The beneficial technical effects of this invention are as follows:

[0023] The preparation method described in this invention addresses the differences in EBSD sample preparation requirements for oriented silicon steel samples from different processes, resulting in a method suitable for preparing EBSD samples of oriented silicon steel from various processes. The EBSD samples obtained by the method described in this invention produce high-quality EBSD analysis images, reduce sample preparation time, improve work efficiency, and allow for the recycling and reuse of the electropolishing solution, thus reducing costs.

[0024] The preparation method described in this invention, by limiting the thermal embedding material used in mechanical polishing, allows for a higher current density during electrolytic polishing of the sample, which helps to shorten the electrolysis time and ensure the gloss of the sample surface. Simultaneously, this invention improves the electrolytic polishing solution used in electrolytic polishing. In the electrolytic polishing solution, acetylacetone acts as an oxidant during electrolysis, and tetramethylammonium chloride acts as a catalyst, which can synergistically promote the electrolysis of metal elements on the sample surface through oxidation and catalysis; methanol and glycerol act as solvents and also promote ion movement, enhancing the electrolysis effect.

[0025] This invention achieves selective dissolution of metals in an electrolyte by controlling parameters such as temperature and current density during electropolishing, with the protruding parts of the metal being more easily dissolved. Attached Figure Description

[0026] Figure 1 EBSD image of the hot rolling process of oriented silicon steel in Embodiment 2 of the present invention.

[0027] Figure 2 EBSD image of the first rolling process of grain-oriented silicon steel in Embodiment 6 of the present invention.

[0028] Figure 3 EBSD image of the decarburization process of oriented silicon steel in Example 12 of this invention.

[0029] Figure 4 EBSD image of the second rolling process of oriented silicon steel in Example 16 of this invention. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Electropolishing can effectively reduce sample preparation time and cost, while obtaining samples with high calibration rate. The success of the electropolishing method is related to the electrolyte and polishing parameters (polishing time, voltage, electrolyte flow rate, temperature, etc.). Therefore, this invention proposes an electropolishing preparation method for oriented silicon steel EBSD samples.

[0032] Common processes in the preparation of grain-oriented silicon steel include hot rolling, first rolling, decarburization, and second rolling. The requirements for EBSD sample preparation typically differ for each process. Hot rolling and decarburization processes result in relatively low surface stress, making it easier to obtain EBSD samples with high calibration rates. However, for samples from the first and second rolling processes, the surface stress is relatively high, significantly impacting EBSD observation; therefore, it is necessary to minimize surface stress. Traditional perchloric acid-alcohol solutions have limited effectiveness in reducing sample surface stress. This invention, through improvements to the electropolishing solution and by increasing the electrolysis voltage and time, effectively reduces sample surface stress, resulting in EBSD samples suitable for different processes and with high calibration rates.

[0033] The process of the present invention will be described in detail below through examples and comparative examples.

[0034] Examples 1-5, Comparative Examples 1-5

[0035] The mechanical polishing process is the same for Examples 1-5 and Comparative Examples 1-5, except for the electrolytic polishing. The mechanical polishing process is as follows:

[0036] A 2.2mm thick hot-rolled material was cut into 10mm (TD) * 20mm (RD) rectangular samples using a laser cutting machine. After mounting the samples with black conductive thermal embedding material, they were mechanically polished sequentially on 240, 400, 800, 1200, and 2000 grit sandpaper to ensure that the final surface scratches were oriented in one direction. The polished samples were then mechanically polished to a mirror finish. The surface roughness of the mirror-finished grained silicon steel was ≤0.16μm, using diamond spray polishing compound W2.5.

[0037] During electropolishing, the electropolishing solution was prepared and the parameters of the electropolishing instrument were selected according to Tables 1 and 2 to obtain Examples 1-5 and Comparative Examples 1-2, in which methanol and acetylacetone were both 98 wt.% reagents, and glycerol, ethylene glycol and 1,3-propanediol were all 99 wt.% reagents.

[0038] The polishing solution described in Examples 1-5 and Comparative Examples 1-2 is prepared as follows: according to the volume or mass in Table 1-2, first take tetramethylammonium chloride, dissolve it in methanol, and then add acetylacetone and glycerol or 1,3-propanediol or ethylene glycol in sequence (glycerol in Examples 1-3 and Comparative Examples 1-2, ethylene glycol in Example 4, and 1,3-propanediol in Example 5), mix evenly, and obtain the polishing solution.

[0039] The formulation of the electropolishing solution and the parameters of the electropolishing instrument for Comparative Examples 3-5 are shown in Table 3. The perchloric acid solution has a specification of 0.1002 mol / L and the ethanol is a 99 wt.% reagent.

[0040] The polishing solution in Comparative Examples 3-5 was prepared by mixing perchloric acid and ethanol evenly according to the amounts specified in Table 3.

[0041] Table 1. Proportioning of electropolishing solution and parameters of electropolishing machine for hot-rolled materials.

[0042]

[0043]

[0044] Table 2. Proportions of electropolishing solution (ethylene glycol and 1,3-propylene glycol) and parameters of electropolishing equipment for hot-rolled materials.

[0045]

[0046] Table 3. Commonly used electropolishing solutions and parameters of electropolishing equipment for hot-rolled materials.

[0047]

[0048] Examples 1-5 and Comparative Examples 1-5 show the following post-mechanical polishing treatment process: The mechanically polished samples were placed in an electrolytic polishing apparatus, and a preset program was started. After electrolytic polishing was completed, the samples were removed, placed in anhydrous ethanol solution, ultrasonically cleaned for 2 minutes, and then dried with a hair dryer to obtain EBSD samples. EBSD observation was then performed to obtain typical hot-rolled process EBSD images, such as... Figure 1 As shown, the calibration rate of Example 2 is 95%.

[0049] Examples 6-10, Comparative Examples 6-10

[0050] The mechanical polishing process is the same for Examples 6-10 and Comparative Examples 6-10, except for the electrolytic polishing. The mechanical polishing process is as follows:

[0051] A laser cutting machine was used to cut 0.625mm thick first-rolled steel material into rectangular samples measuring 10mm (TD) * 20mm (RD). After mounting the samples with black conductive thermal embedding material, they were mechanically polished sequentially on 240, 400, 800, 1200, and 2000 grit sandpaper to ensure that the final surface scratches were oriented in one direction. The polished samples were then mechanically polished to a mirror finish. The surface roughness of the mirror-finished grained silicon steel was ≤0.16μm, using diamond spray polishing agent W1.5.

[0052] During electropolishing, the electropolishing solution was prepared and the parameters of the electropolishing instrument were selected according to Tables 4 and 5 to obtain Examples 6-10 and Comparative Examples 6-7, in which methanol and acetylacetone were both 98 wt.% reagents, and glycerol, ethylene glycol and 1,3-propylene glycol were all 99 wt.% reagents.

[0053] The polishing solution described in Examples 6-10 and Comparative Examples 6-7 is prepared as follows: according to the volume or mass in Table 4-5, first take tetramethylammonium chloride, dissolve it in methanol, and then add acetylacetone and glycerol or 1,3-propanediol or ethylene glycol in sequence (as shown in Table 4-5), mix evenly, and obtain the polishing solution.

[0054] The formulation of the electropolishing solution and the parameters of the electropolishing instrument for Comparative Examples 8-10 are shown in Table 6. The perchloric acid solution has a specification of 0.1002 mol / L and the ethanol is a 99 wt.% reagent.

[0055] The polishing solution in Comparative Examples 8-10 was prepared by mixing perchloric acid and ethanol evenly according to the amounts specified in Table 6.

[0056] Table 4. Proportions of electropolishing solution and parameters of electropolishing machine for first-roll mill materials.

[0057]

[0058] Table 5 shows the proportions of the electropolishing solution (ethylene glycol and 1,3-propylene glycol) and the parameters of the electropolishing machine for the first rolling mill process materials.

[0059]

[0060] Table 6. Commonly used electropolishing solutions and parameters of electropolishing equipment for first-roll mill materials.

[0061]

[0062] Examples 6-10 and Comparative Examples 6-10 show the following post-mechanical polishing processing steps: The mechanically polished samples were placed in an electrolytic polishing apparatus, and a preset program was started. After electrolytic polishing was completed, the samples were removed, placed in anhydrous ethanol solution, ultrasonically cleaned for 2 minutes, and then dried with a hair dryer to obtain EBSD samples. EBSD observation was then performed, yielding typical first-rolling process EBSD images as shown below. Figure 2 The calibration rate of Example 6 was 83%.

[0063] Examples 11-15, Comparative Examples 11-15

[0064] The mechanical polishing process is the same for Examples 11-15 and Comparative Examples 11-15, except that the electropolishing process is different. The mechanical polishing process is as follows:

[0065] A 0.625mm thick decarburized material was cut into rectangular pieces measuring 10mm (TD) * 20mm (RD) using a laser cutter. After mounting the pieces with black conductive thermal embedding material, they were mechanically polished sequentially on 240, 400, 800, 1200, and 2000 grit sandpaper to ensure that the final surface scratches were oriented in one direction. The polished samples were then mechanically polished to a mirror finish. The surface roughness of the mirror-finished grained silicon steel was ≤0.16μm, using diamond spray polishing agent W2.5.

[0066] During electropolishing, the electropolishing solution was prepared and the parameters of the electropolishing instrument were selected according to Tables 7 and 8 to obtain Examples 11-15 and Comparative Examples 11-12, in which methanol and acetylacetone were both 98 wt.% reagents, and glycerol, ethylene glycol and 1,3-propanediol were all 99 wt.% reagents.

[0067] The polishing solution described in Examples 11-15 and Comparative Examples 11-12 is prepared as follows: according to the volume or mass in Table 7-8, first take tetramethylammonium chloride, dissolve it in methanol, and then add acetylacetone and glycerol or 1,3-propanediol or ethylene glycol in sequence (see Table 7-8 for details), mix evenly, and obtain the polishing solution.

[0068] The formulation of the electropolishing solution and the parameters of the electropolishing instrument for Comparative Examples 13-15 are shown in Table 9. The perchloric acid solution has a specification of 0.1002 mol / L and the ethanol is a 99 wt.% reagent.

[0069] The polishing solution in Comparative Examples 13-15 was prepared by mixing perchloric acid and ethanol evenly according to the amounts specified in Table 9.

[0070] Table 7. Proportions of electropolishing solution and parameters of electropolishing machine for decarburization process materials.

[0071]

[0072] Table 8 shows the proportions of the electropolishing solution (ethylene glycol and 1,3-propylene glycol) for decarburization process materials and the parameters of the electropolishing machine.

[0073]

[0074] Table 9. Commonly used electropolishing solutions and parameters of electropolishing equipment for decarburization process materials.

[0075]

[0076]

[0077] Examples 11-15 and Comparative Examples 11-15 follow the following processing steps after mechanical polishing: The mechanically polished samples are placed in an electrolytic polishing apparatus, and a preset program is started. After electrolytic polishing is complete, the samples are removed and placed in anhydrous ethanol solution. They are then ultrasonically cleaned for 2 minutes and dried with a hair dryer to obtain EBSD samples. EBSD observation can then be performed to obtain typical decarburization process EBSD images, as shown below. Figure 3 The calibration rate of Example 12 was 98%.

[0078] Examples 16-20, Comparative Examples 16-20

[0079] The mechanical polishing processes in Examples 16-20 and Comparative Examples 16-20 are the same, the difference being in electrolytic polishing. The mechanical polishing process is as follows:

[0080] A laser cutting machine was used to cut 0.23mm thick double-rolled material into rectangular samples measuring 10mm (TD) * 20mm (RD). After mounting the samples with black conductive thermal embedding material, they were mechanically polished sequentially on 240, 400, 800, 1200, and 2000 grit sandpaper to ensure that the final surface scratches were oriented in one direction. The polished samples were then mechanically polished to a mirror finish. The surface roughness of the mirror-finished grained silicon steel was ≤0.16μm, and the polishing agent was diamond spray polishing agent W1.5.

[0081] During electropolishing, the electropolishing solution was prepared and the parameters of the electropolishing instrument were selected according to Tables 10 and 11 to obtain Examples 16-20 and Comparative Examples 16-17, in which methanol and acetylacetone were both 98 wt.% reagents, and glycerol, ethylene glycol and 1,3-propylene glycol were all 99 wt.% reagents.

[0082] The polishing solution described in Examples 16-20 and Comparative Examples 16-17 is prepared as follows: according to the volume or mass in Table 10-11, first take tetramethylammonium chloride, dissolve it in methanol, and then add acetylacetone and glycerol or 1,3-propanediol or ethylene glycol in sequence (see Table 10-11 for details), mix evenly, and obtain the polishing solution.

[0083] The formulation of the electropolishing solution for Comparative Examples 18-20 and the parameters of the electropolishing apparatus are shown in Table 6. The perchloric acid solution has a specification of 0.1002 mol / L, and the ethanol is a 99 wt.% reagent.

[0084] The polishing solution in Comparative Examples 18-20 was prepared by mixing perchloric acid and ethanol evenly according to the amounts specified in Table 12.

[0085] Table 10: Proportions of electropolishing solution and parameters of electropolishing machine for second-roll mill materials.

[0086]

[0087]

[0088] Table 11 shows the proportions of the electropolishing solution (ethylene glycol and 1,3-propylene glycol) and the parameters of the electropolishing machine for the second rolling mill process materials.

[0089]

[0090] Table 12. Commonly used electropolishing solutions and parameters of electropolishing equipment for second-rolling process materials.

[0091]

[0092] Examples 16-20 and Comparative Examples 16-20 are processed as follows after mechanical polishing: The mechanically polished samples are placed in an electrolytic polishing apparatus, and a preset program is started. After electrolytic polishing is completed, the samples are removed and placed in anhydrous ethanol solution. They are then ultrasonically cleaned for 2 minutes and dried with a hair dryer to obtain EBSD samples. EBSD observation can then be performed to obtain typical EBSD images of the second rolling process, as shown below. Figure 4 Example 16 has a calibration rate of 85%.

[0093] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A method for preparing an EBSD sample of grain-oriented silicon steel, characterized in that, The preparation method is as follows: first, the grain-oriented silicon steel sample is mechanically polished, then electrolytically polished, then ultrasonically cleaned, and dried to obtain a grain-oriented silicon steel EBSD sample; the grain-oriented silicon steel sample is a grain-oriented silicon steel sample obtained by hot rolling process, decarburization annealing process, single cold rolling process, or double cold rolling process. The voltage for electropolishing is 10~30V, and the current is 0.15~0.65A; The polishing solution used for electropolishing is composed of methanol, glycerol, acetylacetone and tetramethylammonium chloride; the volume ratio of methanol, glycerol, acetylacetone and tetramethylammonium chloride is (420~780):(54~200):(45~120):(5.1~25.7); The polishing solution is prepared by dissolving tetramethylammonium chloride in methanol, then adding acetylacetone and glycerol in sequence, mixing thoroughly to obtain the polishing solution.

2. The preparation method according to claim 1, characterized in that, The mechanical polishing involves hot-mounting the grained silicon steel sample, followed by grinding and polishing to obtain a grained silicon steel sample with a mirror finish.

3. The preparation method according to claim 2, characterized in that, The material used for thermal embedding is a black conductive thermal embedding material.

4. The preparation method according to claim 2, characterized in that, The polishing process involves sequentially polishing with sandpaper of grits of 240, 400, 800, 1200, and 2000.

5. The preparation method according to claim 2, characterized in that, The polishing agent used for polishing is a diamond spray polishing agent, specifically W1.5 or W2.5; the surface roughness of the mirror-finished oriented silicon steel is ≤0.16μm.

6. The preparation method according to claim 1, characterized in that, The electropolishing temperature is 20~28℃; the pump speed is 800~1200r / min; and the electropolishing time is 15~40s.

7. The preparation method according to claim 1, characterized in that, The glycerol is replaced with ethylene glycol or 1,3-propanediol.

8. An EBSD sample of oriented silicon steel prepared by the preparation method according to any one of claims 1-7.

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