A method for detecting nanoscale precipitation phases in steel based on scanning electron microscopy

Abstract

The present application provides a method for detecting nanoscale precipitates in steel based on a scanning electron microscope, comprising the following steps: pre-treating a graphite block to obtain a graphite base sample; polishing the sample and then deep etching it to obtain a deep etching sample; covering the surface of the deep etching sample with an acetone solution and then covering it with a cellulose acetate film, waiting for the cellulose acetate film to dissolve and solidify again to form a thin film, removing the film and spraying carbon on the inner side of the film to obtain a cellulose acetate carbon film; placing the cellulose acetate carbon film in an acetone solution until the cellulose acetate in the cellulose acetate carbon film is completely dissolved to obtain a carbon film; flattening the carbon film in deionized water, using a graphite base sample to fish out the film, and then drying and cleaning to obtain a sample to be detected; placing the sample to be detected under a scanning electron microscope for precipitate phase detection and statistics. The present application can detect nanoscale precipitates with a size of ≥10 nm, while effectively improving the statistical efficiency of the precipitate phase and ensuring the accuracy of the statistical results.

Description

Technical Field

[0001] The present application relates to the technical field of steel material detection methods, and in particular to a method for detecting nano-scale precipitation phases in steel based on a scanning electron microscope. Background Art

[0002] In the development and production of steel materials, the desired microstructure and properties are generally achieved through the rational design and control of composition, process, and heat treatment. The core mechanism is the dissolution and precipitation behavior of alloying elements. Therefore, the detection, analysis, and control of precipitates in steel materials to adjust their product quality are essential in the development and production of steel materials. Currently, the detection and analysis of nanoscale precipitates in steel materials mainly rely on transmission electron microscopy. However, transmission electron microscopy cannot automatically count precipitates. This is mainly due to the small depth of field of transmission electron microscopy. Even very small bumps require manual focus adjustment of the sample before analysis. Moreover, it is impossible to ensure that the sample is in the same plane during sample preparation. Therefore, when moving samples over a large range for statistics, statistics can only be performed on each single field of view after manually adjusting each field of view. At the same time, the maximum sample size for transmission electron microscopy is a circle with a diameter of 3 mm, which limits the size of the sample for statistics. While scanning electron microscopy can perform large-scale statistics and analysis on the composition, morphology, quantity, and size of inclusions in a sample, it can currently only perform statistics on specific steel samples with an analysis size of 50nm or larger. Furthermore, because the support for the precipitates during the statistical process is a steel matrix, the iron signal will be very strong, and the precipitate signal obtained will be misinterpreted as background. Furthermore, the single-point acquisition time is longer than conventional statistical time, and the total statistical time will be longer. This method also requires the sample to be corroded, and when using energy spectrum analysis to analyze precipitates and inclusions, the sample must be polished. The corroded sample surface will not only have convex ridges from the precipitates, but also convex ridges from interfaces such as the microstructure and grain boundaries, which seriously affects the accuracy of the collected signals and the statistical results, resulting in poor statistical accuracy. Summary of the Invention

[0003] In order to solve the technical problems in the prior art that the method for detecting precipitation phases of steel materials based on transmission electron microscopy cannot realize large-area automatic statistics, and the method for detecting precipitation phases of steel materials based on scanning electron microscopy can only be used for statistical analysis of precipitation phases of specific steel types with a size of more than 50nm, and the statistical time is long and the accuracy of statistical results is poor; this application proposes a method for detecting nano-scale precipitation phases of steel based on scanning electron microscopy to realize the detection and automatic statistics of nano-scale precipitation phases with a size of ≥10nm, while also improving the statistical efficiency and the accuracy of statistical results.

[0004] In order to achieve the above-mentioned purpose, this application adopts the following technical solutions:

[0005] A method for detecting nanoscale precipitated phases in steel based on a scanning electron microscope comprises the following steps:

[0006] The graphite block is cut once, prepared metallographically to a polished state of 1 μm, vibrated polished, and cut twice to obtain a graphite base sample;

[0007] The one-time cutting process is to process a graphite block (or graphite rod) with a purity higher than 99.9% and a dense interior into a small square graphite block (or a round graphite rod with a diameter of 10 mm) with a length, width and height of 10 mm × 10 mm × 10 mm, and to inlay the processed small square graphite block / round graphite rod with a cold inlay mold with a diameter of 30 mm. The small square graphite block / round graphite rod is inlaid at 1 / 4 of the diameter of the inlay block with a height of not less than 25 mm. The inlaid small square graphite block / round graphite rod is placed on a precision cutting machine for one-time cutting, and a thickness of 1 mm is cut off from the edge.

[0008] The metallographic sample preparation process is to automatically grind and polish the small square graphite / round graphite rod cut once on an automatic grinding and polishing machine to a polished state of 1µm according to the standard metallographic sample preparation process;

[0009] The weight of the auxiliary block used in the vibration polishing process is 300g-500g, and the polishing time is 50min-70min;

[0010] The sample was prepared by metallographic method to a polished state of 5µm and then deep-etched. The sample was then rinsed with running water and then blown dry. During this process, cotton balls or other items should not be used to wipe the sample surface to obtain a deep-etched sample.

[0011] The surface of the deep-etched sample is covered with an acetone solution and then covered with a cellulose acetate film. After the cellulose acetate film is dissolved in the surface of the deep-etched sample and solidified again to form a film, the film is removed and carbon spraying is performed on the side of the film that contacts the deep-etched sample to obtain a cellulose acetate carbon film;

[0012] placing the cellulose acetate carbon film in an acetone solution until the cellulose acetate in the cellulose acetate carbon film is completely dissolved to obtain a carbon film;

[0013] The carbon film is placed in water and flattened, and the graphite substrate is used to fish out the film so that the carbon film is completely spread on the surface of the graphite substrate, and then dried and washed to obtain a sample to be tested;

[0014] The sample to be tested is placed under a scanning electron microscope for precipitated phase detection and statistics; wherein, the detection parameters of the scanning electron microscope for precipitated phase detection and statistics include: acceleration voltage: 10kV, energy spectrum output count rate ≥50000cps, equipment acquisition signal: backscattered electrons, brightness and contrast adjustment method: adjust the brightness to 0, gradually increase the contrast, and it is necessary to open the backscattered signal image and the secondary electron image at the same time. When the bright spot in the backscattered image and the precipitated phase in the secondary electron image correspond one to one, and the rest of the backscattered image is black, the value at this time is the brightness and contrast value of the backscattered image during statistics.

[0015] Furthermore, the graphite block is solid graphite with a purity higher than 99.9% and a dense interior.

[0016] Furthermore, during the vibration polishing, a vibration polishing liquid needs to be added to the polishing disc or polishing cloth; the preparation method of the vibration polishing liquid is: pouring the Al2O3 suspension into the KOH solution, magnetically stirring for 1.5h-2.5h, adding detergent, and continuing to stir until a uniform emulsion is formed; wherein the volume ratio of the Al2O3 suspension, the KOH solution and the detergent is 1:1.5:0.1.

[0017] Furthermore, the particle size of the Al2O3 suspension is 0.02µm.

[0018] Furthermore, the concentration of the KOH solution is 5%.

[0019] Furthermore, the thickness of the graphite base sample is 1 mm.

[0020] Furthermore, the carbon spraying process is as follows: the distance between the carbon rod and the film surface is ≥4 cm, the carbon spraying current is 65 nA, the carbon spraying time is 2 s, and the vacuum degree is ≤9×10 -5 mbar.

[0021] Furthermore, the film-retrieving process includes: maintaining the angle between the graphite base sample and the water surface at 150°-160° and slowly inserting it into deionized water in the direction close to the carbon film; after one edge of the carbon film is completely on the surface of the graphite base sample, slowly lifting the graphite base sample while maintaining no displacement between the carbon film and the graphite base sample; at this time, maintaining the angle between the graphite base sample and the water surface at 150°-160°; after the graphite base sample with the carbon film attached is completely lifted out of the deionized water surface, use filter paper to absorb excess deionized water at the edge of the carbon film.

[0022] Furthermore, the drying process is to place the graphite substrate with the carbon film flatly placed in a vacuum of ≤1×10 -4 Vacuum drying in the equipment at mbar for 0.5h-2h.

[0023] Furthermore, the cleaning process is to place the graphite substrate with the carbon film in a plasma cleaning apparatus and clean it with a mixture of hydrogen and oxygen for 5 minutes to 10 minutes.

[0024] The beneficial effects of this application are:

[0025] This application uses a treated graphite block as a base sample and uses a cellulose acetate membrane to extract the sample to a carbon film to obtain a test sample with a smooth surface, no steel matrix interference, and containing nanoscale precipitated phases in the sample. By adjusting the detection parameters under specific conditions, large-area automatic statistics of nanoscale precipitated phases with a size of ≥10nm can be achieved under a scanning electron microscope, and accurate statistical results can be obtained.

[0026] This application uses a mixture of Al2O3 suspension, KOH solution and detergent as a vibration polishing liquid. Combined with auxiliary blocks of a specific weight and a certain polishing time, the surface of the graphite substrate can be made smooth but with slight convexity (within 10nm), thereby ensuring that the carbon film can be laid flat on the surface of the graphite substrate without damage and wrinkles, and can improve the fit between the carbon film and the graphite substrate without affecting the energy spectrum acquisition efficiency, laying a good foundation for the accuracy of the subsequent test results of the samples to be tested, and ensuring the accuracy of the test results.

[0027] The carbon spraying process used in the present application can form a dense carbon film with moderate thickness on the surface of the film, which is convenient for subsequent film scooping and detection and statistics of precipitated phases.

[0028] The film scooping process used in the present application can effectively ensure that the carbon film can be evenly spread on the graphite matrix, thereby ensuring the accuracy of subsequent test statistical results.

[0029] The drying process used in this application can improve the adhesion between the carbon film and the graphite collective surface, and the cleaning process can remove trace gases and water on the carbon film surface, improve the cleanliness of the sample surface, prevent surface contamination during testing, and improve the conductivity of the sample to avoid thermal drift of the sample, thereby improving the accuracy of subsequent test statistical results. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0031] Figure 1 This is a backscattered photograph of the X70MS sample provided in Example 1 of the present application after adjusting the brightness and contrast;

[0032] Figure 2 for Figure 1 Corresponding secondary electron photograph;

[0033] Figure 3 A comparison chart of the minimum precipitated phase size measured for the X70MS sample provided in Example 1 of the present application;

[0034] Figure 4 The distribution and morphology distribution diagram of the precipitated phase in the entire statistical area after the statistics of the X70MS sample provided in Example 1 of the present application are completed;

[0035] Figure 5 The composition diagram of the statistical precipitated phase corresponding to the X70MS sample provided in Example 1 of the present application;

[0036] Figure 6 The size distribution and number diagram of the precipitated phase statistics corresponding to the X70MS sample provided in Example 1 of the present application;

[0037] Figure 7 The statistical precipitate phase distribution and morphology distribution diagram of the W310 sample provided in Example 2 of the present application;

[0038] Figure 8 This is a statistical composition diagram of the precipitated phase of the W310 sample provided in Example 2 of the present application;

[0039] Figure 9 The size, quantity and distribution of the precipitated phase of the W310 sample provided in Example 2 of this application. DETAILED DESCRIPTION

[0040] The technical solutions of this application will be described clearly and completely below with reference to specific embodiments. Obviously, the embodiments described are only a portion of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are intended to fall within the scope of protection of this application.

[0041] Example 1

[0042] A method for detecting nanoscale precipitated phases in steel based on a scanning electron microscope comprises the following steps:

[0043] Prepare vibration polishing liquid

[0044] Use a measuring cylinder to measure 500 mL of neutral Al2O3 suspension with a particle size of 0.02 µm and pour it into a beaker. Stir with a magnetic stirrer. Then use a measuring cylinder to measure 750 mL of 5% KOH solution and pour it into the beaker containing the neutral Al2O3 suspension. After stirring for 2 hours, use a measuring cylinder to measure 50 mL of dishwashing liquid and pour it into the beaker. Continue stirring for 3 hours until a uniform emulsion is obtained.

[0045] Preparation of graphite sample

[0046] A graphite block with a purity exceeding 99.9% and a dense interior was processed into small squares of graphite measuring 10 mm × 10 mm × 10 mm in length, width, and height. The small squares were then mounted using a 30 mm diameter hot-mounting machine, with the small squares positioned at 1 / 4 of the block diameter and at least 25 mm in height. The mounted small squares were then cut using a precision cutter, with a 1 mm thickness removed from the edge. The cut small squares were then automatically polished to a 1 µm finish using an automatic grinder and polisher according to standard metallographic sample preparation procedures. Vibration polishing was then performed using a vibratory polishing fluid. After polishing, the blocks were placed on a precision cutter for a second cut to produce 1 mm thin slices. The surrounding inlays were removed by hand, resulting in a graphite base sample with a polished surface and a thickness of 1 mm. The auxiliary block used for vibration polishing weighed 400 g and the polishing time was 60 min.

[0047] The vibration polishing liquid used in the vibration polishing process is the vibration polishing liquid configured as described above.

[0048] Prepare the sample to be tested

[0049] The X70MS pipeline steel sample was hot-mounted and then polished to 5µm without scratches according to the standard metallographic sample preparation steps. The sample was deep-etched and then rinsed with running water and the surface was quickly dried to obtain a deep-etched sample.

[0050] The surface of the deep-etched sample was covered with acetone solution and then covered with cellulose acetate film. After the cellulose acetate film dissolved in the surface of the deep-etched sample and solidified again to form a film, the film was taken out and fixed, and then the surface of the film in contact with the deep-etched sample was placed in a high vacuum carbon spraying instrument with the surface facing upward, and carbon spraying treatment was performed on the film to obtain a cellulose acetate carbon film. The carbon spraying process was as follows: the distance between the carbon rod and the film surface was 5 cm, the carbon spraying current was 65 nA, the carbon spraying time was 2 s, and the vacuum degree was 5×10 -5 mbar.

[0051] Using a blade, lightly scratch a 4 mm x 4 mm square on a cellulose acetate carbon film; placing the scratched cellulose acetate carbon film in an acetone solution until the cellulose acetate in the cellulose acetate carbon film is completely dissolved to obtain a carbon film; the carbon film is now in a curled state in the acetone solution; removing the curled carbon film and placing it in a beaker filled with deionized water, whereupon the curled carbon film automatically flattens and suspends on the surface of the deionized water;

[0052] Use tweezers to hold one corner of the graphite base sample, and slowly insert the graphite base sample into the deionized water at a position away from the carbon film, keeping the angle between the graphite base sample and the liquid surface always at 150°. When the depth of the graphite base sample in the water is half the side length of the graphite base sample, slowly move the graphite base sample close to the flattened carbon film, at this time, keep the line where the graphite base sample intersects with the water surface parallel to one edge of the carbon film. When the edge of the carbon film is attached to the surface of the graphite base sample, slowly lift the graphite base sample upwards, and continue to keep the angle between the graphite base sample and the liquid surface at 150°. When both the carbon film and the graphite base sample are separated from the deionized water surface, use filter paper to absorb the deionized water around the carbon film on the graphite base sample;

[0053] The graphite substrate with carbon film was placed in a vacuum device and the vacuum degree was maintained at 4×10 -5 mbar, and after 1 hour, take it out and put it into a plasma cleaning instrument for cleaning with a mixture of hydrogen and oxygen to obtain the sample to be tested; wherein, the gas ratio of hydrogen and oxygen in the mixture is 1:1, and the cleaning time is 5 minutes.

[0054] Precipitation phase detection statistics

[0055] Use glue to fix the sample to be tested on the surface of the standard 10mm circular T-stage of the scanning electron microscope, and apply conductive glue to the connection between the sample to be tested and the T-stage to ensure that there is conductivity between the sample to be tested and the T-stage;

[0056] The sample to be tested was placed in a scanning electron microscope for precipitation phase statistics. The statistical parameters were: 1) acceleration voltage 10 kV; 2) energy spectrum output count rate 65,000 cps; 3) the device collected backscattered electrons as the signal; 4) working distance 8.5 mm; 5) brightness and contrast were adjusted to: brightness 0, contrast 85%;

[0057] The scanning area was set to 30 μm × 30 μm, the magnification was 78704, the minimum acquisition size was 0.01 μm, the single particle pixel number was 30, and the acquisition time was 3 s.

[0058] The final collection results can be found in Figures 1-6 .in, Figure 1 The backscattered photos after adjusting the brightness and contrast for the X70MS sample are statistically analyzed. Figure 2 for Figure 1 The corresponding secondary electron photo, Figure 1 and Figure 2 It can be seen from the comparison that after adjusting the brightness contrast, all the precipitated phases in the steel can be identified. Figure 3 The minimum precipitate size measured for the X70MS sample is given by Figure 3 It can be seen that the present application can detect a precipitate phase with a minimum size of 10 nm based on a scanning electron microscope. Figure 4 This is the distribution and morphology of the precipitated phase in the entire statistical area after the statistics of the X70MS sample are completed. Figure 5 is the composition diagram of the statistical precipitation phase corresponding to the X70MS sample, Figure 6 The size distribution and number diagram of the precipitated phase statistics corresponding to the X70MS sample. Figures 4 to 6 It can be seen that the detection method of the present application can quickly analyze and count the composition, morphology, quantity and other information of the precipitated phase with a minimum size of 10 nm in the steel sample over a large area.

[0059] Example 2

[0060] A method for detecting nanoscale precipitated phases in steel based on a scanning electron microscope comprises the following steps:

[0061] Preparation of graphite sample

[0062] A graphite block with a purity exceeding 99.9% and a dense interior is processed into round graphite rods with a thickness of 10 mm and a diameter of 10 mm. The round graphite rods are then mounted using a 30 mm diameter hot mounting machine. The round graphite rods are mounted at 1 / 4 of the mounting block diameter, with a height of no less than 25 mm. The mounted round graphite rods are then placed on a precision cutter for a primary cut, removing 1 mm from the edge. The primary cut round graphite rods are then automatically polished to a 1 µm polished state on an automatic grinder and polished using a vibratory polishing fluid according to standard metallographic sample preparation procedures. After polishing, the rods are placed on a precision cutter for a secondary cut to produce 1 mm thin slices. The surrounding inlays can be removed by gently breaking them apart by hand, resulting in a graphite base sample with a polished surface and a thickness of 1 mm. The auxiliary block used for vibratory polishing weighs 400 g, and the polishing time is 60 min.

[0063] The vibration polishing liquid used in the vibration polishing process is the vibration polishing liquid configured in Example 1.

[0064] Prepare the sample to be tested

[0065] A W310 non-oriented silicon steel sample was hot-mounted and then polished to 5µm without scratches according to the standard metallographic sample preparation steps. The sample was deep-etched and then rinsed with running water and the surface was quickly dried to obtain a deep-etched sample.

[0066] The surface of the deep-etched sample was covered with acetone solution and then covered with cellulose acetate film. After the cellulose acetate film dissolved in the surface of the deep-etched sample and solidified again to form a film, the film was taken out and fixed, and then the surface of the film in contact with the deep-etched sample was placed in a high vacuum carbon spraying instrument with the surface facing upward, and carbon spraying treatment was performed on the film to obtain a cellulose acetate carbon film. The carbon spraying process was as follows: the distance between the carbon rod and the film surface was 6 cm, the carbon spraying current was 65 nA, the carbon spraying time was 3 s, and the vacuum degree was 4×10 -5 mbar.

[0067] Using a blade, lightly scratch a cellulose acetate carbon film into a 5 mm x 5 mm grid; placing the scratched cellulose acetate carbon film into an acetone solution until the cellulose acetate in the cellulose acetate carbon film is completely dissolved to obtain a carbon film; the carbon film is now in a curled state in the acetone solution; removing the curled carbon film and placing it in a beaker filled with deionized water, whereupon the curled carbon film automatically flattens and suspends on the surface of the deionized water;

[0068] Use tweezers to clamp the edge of the graphite base sample, and slowly insert one side of the graphite base sample into the deionized water at a position away from the carbon film, keeping the angle between the graphite base sample and the liquid surface always at 160°. When the depth of insertion into the water is half the diameter of the graphite base sample, slowly move the graphite base sample close to the flattened carbon film, at this time, keep the line where the graphite base sample intersects with the water surface parallel to one edge of the carbon film. When the edge of the carbon film is attached to the surface of the graphite base sample, slowly lift the graphite base sample upwards, and continue to keep the angle between the graphite base sample and the liquid surface at 160°. When both the carbon film and the graphite base sample are separated from the deionized water surface, use filter paper to absorb the deionized water around the carbon film on the graphite base sample;

[0069] The graphite substrate with carbon film was placed in a vacuum device and the vacuum degree was maintained at 4×10 -5 mbar, and after 1 hour, take it out and put it into a plasma cleaning instrument for cleaning with a mixture of hydrogen and oxygen to obtain the sample to be tested; wherein, the gas ratio of hydrogen and oxygen in the mixture is 1:1, and the cleaning time is 5 minutes.

[0070] Precipitation phase detection statistics

[0071] Use glue to fix the sample to be tested on the surface of the standard 10mm circular T-stage of the scanning electron microscope, and apply conductive glue to the connection between the sample to be tested and the T-stage to ensure that there is conductivity between the sample to be tested and the T-stage;

[0072] The sample to be tested was placed in a scanning electron microscope for precipitation phase statistics. The statistical parameters were: 1) acceleration voltage 10 kV; 2) energy spectrum output count rate 50,000 cps; 3) the device collected backscattered electron signals; 4) working distance 8.5 mm; 5) brightness and contrast were adjusted to: brightness 0, contrast 70%;

[0073] The scanning area was set to 10 μm × 20 μm, the magnification was 78704, the minimum acquisition size was 0.01 μm, the single particle pixel number was 30, and the acquisition time was 3 s.

[0074] The final collection results can be found in Figure 7-Figure 9 .in, Figure 7 This is the distribution diagram of the precipitated phase and morphology after statistics of the W310 sample. Figure 8 is the statistical composition diagram of the precipitated phase of W310 sample, Figure 9 The number and distribution of precipitated phases in W310 sample. Figures 7 to 9 It can be seen that the detection method of the present application can also perform large-scale rapid analysis and statistics on the composition, morphology, quantity and other information of the precipitated phase with a minimum size of 10 nm in the W310 non-oriented silicon steel sample.

[0075] The above is a detailed introduction to a method for detecting nanoscale precipitation phases in steel based on a scanning electron microscope provided in the examples of this application. Specific examples are used herein to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for detecting nanoscale precipitation phases in steel based on scanning electron microscopy, characterized in that: The steps include: The graphite block is cut once, prepared metallographically to a polished state of 1 μm, vibrated polished, and cut twice to obtain a graphite base sample; The sample is polished until the surface is in a polished state, and then deep-etched, cleaned, and blown dry to obtain a deep-etched sample; The surface of the deep-etched sample is covered with an acetone solution and then covered with a cellulose acetate film. After the cellulose acetate film is dissolved in the surface of the deep-etched sample and solidified again to form a film, the film is removed and carbon spraying is performed on the side of the film that contacts the deep-etched sample to obtain a cellulose acetate carbon film; placing the cellulose acetate carbon film in an acetone solution until the cellulose acetate in the cellulose acetate carbon film is completely dissolved to obtain a carbon film; The carbon film is placed in deionized water and flattened, and the graphite substrate is used to fish out the film so that the carbon film is completely spread on the surface of the graphite substrate, and then dried and cleaned to obtain a sample to be tested; The sample to be tested is placed under a scanning electron microscope to perform precipitated phase detection and statistics; During the vibration polishing, a vibration polishing liquid needs to be added to the polishing disc or polishing cloth. The vibration polishing liquid is prepared by pouring an Al2O3 suspension into a KOH solution, magnetically stirring for 1.5 hours to 2.5 hours, adding detergent, and continuing to stir until a uniform emulsion is formed. The volume ratio of the Al2O3 suspension, the KOH solution, and the detergent is 1:1.5:0.

1. The weight of the auxiliary block used in the vibration polishing process is 300g to 500g, and the polishing time is 50min to 70min.

2. The method for detecting nanoscale precipitation phases of steel based on a scanning electron microscope according to claim 1, wherein: The graphite block is solid graphite with a purity higher than 99.9% and a dense interior.

3. The method for detecting nanoscale precipitation phases of steel based on scanning electron microscopy according to claim 1, wherein: The particle size of the Al2O3 suspension is 0.02 μm.

4. The method for detecting nanoscale precipitation phases of steel based on scanning electron microscopy according to claim 1, wherein: The thickness of the graphite base sample is 1 mm.

5. The method for detecting nanoscale precipitation phases of steel based on scanning electron microscopy according to claim 1, wherein: The carbon spraying process is as follows: the distance between the carbon rod and the film surface is ≥4 cm, the carbon spraying current is 65 nA, the carbon spraying time is 2s-3s, and the vacuum degree is ≤9×10 -5 mbar.

6. The method for detecting nanoscale precipitation phases of steel based on scanning electron microscopy according to claim 1, wherein: The film-lifting process includes: maintaining an angle of 150°-160° between the graphite base sample and the deionized water surface and slowly inserting the graphite base sample into the deionized water in a direction close to the carbon film; after the carbon film is completely attached to the surface of the graphite base sample, slowly lifting the graphite base sample while maintaining no displacement between the carbon film and the graphite base sample; at this time, maintaining an angle of 150°-160° between the graphite base sample and the water surface; and after the graphite base sample with the carbon film attached is completely lifted out of the deionized water surface, using filter paper to absorb excess deionized water.

7. The method for detecting nanoscale precipitation phases of steel based on scanning electron microscopy according to claim 1, wherein: The drying process is to place the graphite substrate with the carbon film flatly in a vacuum of ≤1×10 -4 Dry in vacuum for 0.5-2 h in a 100 mbar device.

8. The method for detecting nanoscale precipitation phases of steel based on scanning electron microscopy according to claim 1, wherein: The cleaning process is to place the graphite substrate with the carbon film in a plasma cleaning apparatus and clean it with a mixture of hydrogen and oxygen for 5 minutes to 10 minutes.

9. The method for detecting nanoscale precipitation phases of steel based on scanning electron microscopy according to claim 1, wherein: The detection parameters for the precipitated phase detection statistics using the scanning electron microscope include: acceleration voltage: 10 kV, energy spectrum output count rate ≥ 50,000 cps, device acquisition signal: backscattered electrons, brightness and contrast adjustment method: adjust the brightness to 0 and gradually increase the contrast. It is necessary to open the backscattered signal image and the secondary electron image at the same time. When the bright spots in the backscattered image correspond one-to-one to the precipitated phase in the secondary electron image, and the rest of the backscattered image is black, the values at this time are the brightness and contrast values of the backscattered image during statistics.

Images