Method for evaluating performance of phosphating film on surface of steel plate by using scanning electron microscope

Abstract

The invention provides a method for evaluating the performance of a steel plate surface phosphating film by using a scanning electron microscope, and relates to the field of material analysis and testing, and the method comprises the following steps: S1, sample preparation: selecting a sample with a main working surface of a detected steel plate as a surface phosphating film, and cutting to obtain a measurement sample; s2, evaluating the phosphating film coverage rate: acquiring the phosphating film coverage rate of the sample, comparing the phosphating film coverage rate of the sample with a preset coverage rate standard index, when the phosphating film coverage rate of the sample is judged to meet the requirement, executing S3, and otherwise, judging that the performance of the phosphating film on the surface of the steel plate is unqualified; and S3, wear resistance evaluation: carrying out phosphating film crystal size extraction on the sample with the phosphating film coverage rate meeting the requirement, and comparing the phosphating film crystal size with a preset wear resistance standard index so as to output an evaluation result. According to the evaluation method, damage is not needed, measurement is accurate, accurate phosphating film thickness information can be obtained, and the evaluation method can be applied to detection and analysis practice in the future to improve the research and development capacity.

Description

Technical Field

[0001] The invention relates to the field of material analysis and testing, and in particular to a method for evaluating the performance of a phosphating film on a steel plate surface by using a scanning electron microscope. Background Art

[0002] Phosphate coating is widely used in the surface treatment of transmission gears, engine pistons, shafts and other parts. This process can eliminate microscopic defects and processing stress on the surface of parts, enhance the lubrication performance of the surface of parts, reduce initial wear and extend the service life of parts.

[0003] Through the analysis of a large number of failure cases of gearbox, engine and axle shaft components, it was found that the effect of phosphate film on improving the lubrication performance of component surface is mainly related to three factors: whether the phosphate film is completely covered, the thickness of the phosphate film, and the degree of depression formed by phosphating on the surface of the component.

[0004] Traditional wear-resistant phosphate film performance evaluation indicators and methods include appearance, phosphate film unit area quality and wear resistance. The appearance evaluation index mainly evaluates the continuity of the phosphate film. Since visual observation or a magnifying glass of less than 6 times is used during observation, only a rough macroscopic judgment can be made. In addition, different evaluators have different understandings of the evaluation standards, and it is impossible to accurately evaluate the actual coverage level of the phosphate film on the surface of the parts. The phosphate film unit area quality evaluation index indirectly evaluates the thickness of the phosphate film, and the evaluation method is mainly the weighing method. The result of this method reflects the average thickness of the phosphate film on the surface of the sample. The problem is that if the local phosphate film is too thick or too thin, or even partially uncovered, the result will be misjudged.

[0005] Therefore, compared with the traditional phosphate film evaluation method, it is necessary to explore a more effective and reasonable phosphate film performance evaluation method and index. Using a scanning electron microscope, we can not only observe the microscopic morphology of the phosphate film, but also measure its size to evaluate the performance of the phosphate film. Summary of the invention

[0006] According to the above technical problem that the traditional phosphating evaluation method cannot reasonably reflect the performance of the phosphating film, a method for evaluating the performance of the phosphating film on the surface of the steel plate using a scanning electron microscope is provided. Using a scanning electron microscope, the microscopic morphology of the phosphating film can be observed, and its size can be measured to evaluate the performance of the phosphating film.

[0007] The technical means adopted by the present invention are as follows:

[0008] A method for evaluating the performance of a phosphate coating on a steel plate surface using a scanning electron microscope comprises:

[0009] S1. Sample preparation: Select a sample whose main working surface of the steel plate to be tested is a phosphating film on the surface and cut it to obtain a measuring sample;

[0010] S2, phosphate film coverage evaluation: on the one hand, it is used to obtain the phosphate film coverage of the measurement sample, and on the other hand, it is used to compare the phosphate film coverage of the measurement sample with the preset coverage standard index. When it is judged that the phosphate film coverage of the measurement sample meets the requirements, S3 is executed, otherwise it is judged that the performance of the phosphate film on the surface of the steel plate is unqualified;

[0011] S3. Wear resistance evaluation: On the one hand, it is used to extract the crystal size of the phosphate film for the measurement samples whose phosphate film coverage meets the requirements; on the other hand, it is used to compare the crystal size of the phosphate film with the preset wear resistance standard index, so as to output the evaluation results.

[0012] Further, obtaining the phosphate film coverage of the measurement sample includes: placing the measurement sample under a first magnification of a scanning electron microscope to observe the phosphate film coverage.

[0013] Furthermore, the preset coverage standard indicator is set to a coverage of 100%.

[0014] Furthermore, observe the coverage of the phosphate film in no less than 10 fields of view.

[0015] Furthermore, the phosphate film crystal size extraction is performed on the measurement sample whose phosphate film coverage meets the requirements, including:

[0016] The measurement sample is placed under the second magnification of the scanning electron microscope for observation, and the sizes of the largest grain and the smallest grain are measured in each field of view, so as to calculate the average crystal size of the phosphate film, and the average crystal size is used to characterize the thickness of the phosphate film on the surface of the steel plate in the current field of view;

[0017] The second magnification is greater than the first magnification.

[0018] Furthermore, under the premise of complete coverage of the phosphate film, the wear resistance of the phosphate film is best when the crystal size of the phosphate film is 4 to 10 μm.

[0019] Furthermore, no less than 10 crystal size measurement points are selected in each sample and each field of view.

[0020] Furthermore, in S1, the length, width and height of the sample are cut by wire cutting to obtain a measurement sample.

[0021] Furthermore, the crystal size reflects the thickness of the phosphate film on the surface of the inspected steel plate in a certain field of view. Under the premise that the phosphate film covers completely, the calculated average crystal size is the true thickness of the phosphate film on the surface of the inspected steel plate.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The present invention uses a scanning electron microscope to observe the microscopic morphology of the phosphating film, observes the coverage of the phosphating film in no less than 10 fields of view, and then after magnification, measures its crystal size to evaluate the performance of the phosphating film, and evaluates the performance of the phosphating film by the coverage and crystal size of the phosphating film. This microscopic measurement and evaluation method of the phosphating film does not require destruction, has accurate measurement, and can obtain accurate phosphating film thickness information, which can be applied to detection and analysis practices in the future to improve research and development capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 The figure is a flow chart of the method of the present invention.

[0026] Figure 2 This is a schematic diagram of the phosphate film coverage of the first sample in the present invention.

[0027] Figure 3 Schematic diagram of the phosphate film coverage of the second sample in the present invention

[0028] Figure 4 This is a schematic diagram of the average crystal size of the first sample in the present invention.

[0029] Figure 5 This is a schematic diagram of the average crystal size of the second sample in the present invention. DETAILED DESCRIPTION

[0030] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] like Figure 1As shown, the present invention provides a method for evaluating the performance of the phosphate film on the surface of a steel plate using a scanning electron microscope, a method for evaluating the performance of the phosphate film on the surface of a steel plate using a scanning electron microscope, and the specific scheme is as follows:

[0033] 1. Sample preparation: Select the main working surface of the steel plate to be tested with phosphating film on the surface, and cut a sample of appropriate length, width and height by wire cutting method.

[0034] 2. Coverage measurement: Place the sample under a scanning electron microscope and observe it at a magnification of 50 to 200 times, and observe the coverage of the phosphate film in no less than 10 fields of view.

[0035] 3. Measurement of crystal size of phosphate film: The sample is observed under a scanning electron microscope, magnified 1000-2000 times, the largest grain and the smallest grain are selected in each field of view and their sizes are measured, and no less than 10 crystal size measurement points are selected for each sample to calculate the average crystal size of the phosphate film.

[0036] 4. Phosphate film performance evaluation: 4.1 Phosphate film coverage: In order to avoid differences in observation, calculation and different inspection personnel's grasp of the calculation standard, the phosphate film coverage requirement is strictly stipulated to be 100% to eliminate uncertain factors and facilitate accurate evaluation of the coverage of the phosphate film. 4.2 Phosphate film crystal size: Calculate the average crystal size based on the measurement results. The thickness of the phosphate film becomes thicker as the crystal size of the phosphate film increases. Although it is a nonlinear relationship, a certain range of phosphate film crystal size can correspond to a certain range of phosphate film thickness; and the crystal size reflects the thickness of the phosphate film on the surface of the inspected steel plate in a certain field of view. Under the premise of complete coverage of the phosphate film, the calculated average crystal size is the true thickness of the phosphate film on the surface of the inspected steel plate. It was found from a large number of failure analysis cases that the phosphate film crystal size is 4 to 10 μm, and the wear resistance of the phosphate film is the best. Therefore, as an evaluation index, the phosphate crystal size can effectively evaluate the performance of the phosphate film.

[0037] Example 1

[0038] like Figure 2-5 As shown, a method for evaluating the performance of phosphate film on the surface of steel plate by scanning electron microscopy is provided, taking the phosphate film sample on the surface of high-strength automobile plate as an example; including:

[0039] 1. Sample preparation:

[0040] Select the phosphate film sample on the surface of high-strength automobile plate, and cut a suitable sample with a length of 20mm, a width of 20mm and a height of 2mm by wire cutting method.

[0041] 2. Observe the phosphating film coverage under scanning electron microscope:

[0042] Observe under a scanning electron microscope, select an acceleration voltage of 15-20 kV, a working distance of 9-10 mm, and an appropriate magnification of 200 times. Obtain high-definition electron images at a scanning speed of 16 seconds / frame to observe the coverage of the phosphate film in each field of view.

[0043] 3.Measure the crystal size of phosphate film under scanning electron microscope:

[0044] Observe under a scanning electron microscope, select an acceleration voltage of 15-20 kV, a working distance of 9-10 mm, and a suitable magnification of 1000 times, and obtain a high-definition electron image at a scanning speed of 32 seconds / frame. Save the image, use the measurement tool (point to point) in the toolbar, select the largest grain and the smallest grain in each field of view and measure their size, select no less than 10 crystal size measurement points for each sample, and calculate the average crystal size of the phosphate film.

[0045] 4. Phosphate film performance evaluation:

[0046] 4.1 Phosphate coating coverage: Figure 2 , Figure 3 The phosphate film coverage of the samples was 100% and was judged to be qualified.

[0047] 4.2 Phosphate crystal size: According to the measurement results, the average crystal size is 16.684μm for the first sample and 7.911μm for the second sample. The crystal size of the phosphate film of the second sample is 4-10μm, and the wear resistance of the phosphate film is the best. The performance of the phosphate film of the first sample is poor.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the performance of phosphate film on the surface of steel plate using scanning electron microscopy, characterized in that: include: S1. Sample preparation: Select a sample whose main working surface of the steel plate to be tested is a phosphating film on the surface and cut it to obtain a measuring sample; S2, phosphate film coverage evaluation: on the one hand, it is used to obtain the phosphate film coverage of the measurement sample, and on the other hand, it is used to compare the phosphate film coverage of the measurement sample with the preset coverage standard index. When it is judged that the phosphate film coverage of the measurement sample meets the requirements, S3 is executed, otherwise it is judged that the performance of the phosphate film on the surface of the steel plate is unqualified; S3. Wear resistance evaluation: On the one hand, it is used to extract the crystal size of the phosphate film for the measurement samples whose phosphate film coverage meets the requirements; on the other hand, it is used to compare the crystal size of the phosphate film with the preset wear resistance standard index, so as to output the evaluation results.

2. The method for evaluating the performance of the phosphate film on the surface of a steel plate by using a scanning electron microscope according to claim 1, characterized in that: Obtaining the phosphate film coverage of the measurement sample includes: placing the measurement sample under a first magnification of a scanning electron microscope to observe the phosphate film coverage.

3. The method for evaluating the performance of the phosphate film on the surface of a steel plate by using a scanning electron microscope according to claim 1, characterized in that: The default coverage standard indicator is set to 100% coverage.

4. The method for evaluating the performance of the phosphate film on the surface of a steel plate by using a scanning electron microscope according to claim 2, characterized in that: Observe the coverage of the phosphate film in no less than 10 fields of view.

5. The method for evaluating the performance of the phosphate film on the surface of a steel plate by using a scanning electron microscope according to claim 1, characterized in that: For the measurement samples whose phosphate coating coverage meets the requirements, the phosphate coating crystal size is extracted, including: The measurement sample is placed under the second magnification of the scanning electron microscope for observation, and the sizes of the largest grain and the smallest grain are measured in each field of view, so as to calculate the average crystal size of the phosphate film, and the average crystal size is used to characterize the thickness of the phosphate film on the surface of the steel plate in the current field of view; The second magnification is greater than the first magnification.

6. The method for evaluating the performance of the phosphate film on the surface of a steel plate by using a scanning electron microscope according to claim 1, characterized in that: On the premise that the phosphate film covers completely, the wear resistance of the phosphate film is best when the crystal size of the phosphate film is 4 to 10μm.

7. The method for evaluating the performance of the phosphate film on the surface of a steel plate by using a scanning electron microscope according to claim 5, characterized in that: No less than 10 crystal size measurement points shall be selected in each sample and each field of view.

8. The method for evaluating the performance of the phosphate film on the surface of a steel plate by using a scanning electron microscope according to claim 1, characterized in that: In S1, the length, width and height of the sample are cut by wire cutting method to obtain the measurement sample.

9. The method for evaluating the performance of phosphate film on the surface of steel plate by scanning electron microscope according to claim 1, characterized in that: The crystal size reflects the thickness of the phosphate film on the surface of the tested steel plate in a certain field of view. Under the premise that the phosphate film covers completely, the calculated average crystal size is the true thickness of the phosphate film on the surface of the tested steel plate.

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