Steel subsurface defect detection method

Abstract

The invention provides a steel subsurface defect detection method. The method comprises the steps that steel to be detected is divided into two parts in the rolling direction, the divided samples to be detected are marked, the defect positions of the divided samples to be detected have an incidence relation, and the mark of each sample to be detected represents the position state of the sample to be detected before the sample to be detected is divided; dividing the to-be-detected sample into two parts, dividing the two parts into a to-be-oxidized sample and a to-be-analyzed sample, performing oxidation treatment on the to-be-oxidized sample, determining a defect position of the to-be-oxidized sample, and recording the defect position as a defect position A; determining a B defect position of the to-be-analyzed sample according to the position relationship between the to-be-oxidized sample and the mark of the to-be-analyzed sample and the A defect position; and performing subsurface defect detection on the B defect position to obtain a subsurface defect detection result of the steel to be detected.

Description

Technical Field

[0001] The present application relates to the technical field of metal processing, and in particular to a method for detecting sub-surface defects of steel. Background Art

[0002] Cold-rolled steel strip is an important raw material for various processing and manufacturing industries. With the continuous development of industry, the quality requirements for cold-rolled steel strip are becoming more and more stringent. Due to the long production process and thin specifications of cold-rolled steel strip, as well as the reasons of raw materials, rolling equipment, processing technology and system control, various defects are more likely to appear on the surface, the more common ones are linear or strip defects, inclusions, holes and iron oxide scale indentation. Linear defects are one of the most common defects of cold-rolled thin plates. This defect usually extends along the rolling direction and is linear or strip-shaped.

[0003] Since the process from steelmaking to rolling into finished products is long, many factors can cause linear defects in cold-rolled thin plates. Therefore, the causes of linear defects need to be analyzed on a case-by-case basis to determine the cause of the problem and then improve the production line to solve the problem. However, some linear inclusion defects exist on the subsurface after cold rolling and are difficult to locate for detailed inspection. Therefore, the state of the defect is easily destroyed during inspection, resulting in the loss of the true information of the defect, making it difficult to determine the cause of the defect later, resulting in low reliability of defect detection. Summary of the invention

[0004] The embodiment of the present application provides a method for detecting sub-surface defects of steel, which can avoid damage to the defects during detection, thereby obtaining more reliable detection results.

[0005] In a first aspect, the present application provides a method for detecting sub-surface defects of steel, the method comprising:

[0006] The steel to be tested is divided into two parts according to the rolling direction, and the divided samples to be tested are marked, wherein the defect positions of the divided samples to be tested have an associated relationship, and the mark of each sample to be tested represents the position state of the sample to be tested before the division;

[0007] Splitting the sample to be detected into two samples, namely a sample to be oxidized and a sample to be analyzed;

[0008] Performing oxidation treatment on the sample to be oxidized, and determining the defect position of the sample to be oxidized, which is recorded as A defect position;

[0009] Determine the B defect position of the sample to be analyzed according to the positional relationship between the marks of the sample to be oxidized and the sample to be analyzed, and the A defect position;

[0010] Sub-surface defect detection is performed on the B defect position to obtain a sub-surface defect detection result of the steel to be detected.

[0011] In some possible implementations, determining the B defect position of the sample to be analyzed according to the positional relationship between the marks of the sample to be oxidized and the sample to be analyzed, and the A defect position, includes:

[0012] According to the mark, the sample to be oxidized and the sample to be analyzed are matched based on the position state before segmentation;

[0013] Based on the A defect position and the position state before segmentation, the corresponding position of the sample to be analyzed is determined as the B defect position.

[0014] In some possible implementations, the step of matching the sample to be oxidized with the sample to be analyzed based on the position state before segmentation according to the mark includes:

[0015] According to the label, the sample to be oxidized and the sample to be analyzed are spliced;

[0016] According to the positional relationship between the spliced ​​sample to be oxidized and the sample to be analyzed, the sample to be oxidized and the adjacent sample to be analyzed are matched.

[0017] In some possible implementations, the A defect position is a linear defect related to the rolling direction, and based on the A defect position and the position state before segmentation, determining the corresponding position of the sample to be analyzed as the B defect position includes:

[0018] Based on the A defect position, according to the position state before segmentation, an extension line of the A defect position is drawn toward the sample to be analyzed;

[0019] The position of the extended line on the sample to be analyzed is determined as the B defect position.

[0020] In some possible implementations, dividing the steel to be tested into two parts according to the rolling direction and marking the divided samples to be tested include:

[0021] Splitting the sample to be tested into multiple parts perpendicular to the rolling direction;

[0022] The segmented samples to be tested are marked.

[0023] In some possible implementations, the step of performing oxidation treatment on the sample to be oxidized and determining a defect position of the sample to be oxidized, recorded as A defect position, includes:

[0024] When the temperature in the muffle furnace reaches a preset temperature, placing the sample to be oxidized into the muffle furnace;

[0025] While controlling the temperature in the muffle furnace to be within a preset temperature range, heating the sample to be oxidized for a preset time to oxidize the sample to be oxidized;

[0026] According to the surface condition of the sample to be oxidized after oxidation, the defect position of the sample to be oxidized is determined and recorded as A defect position.

[0027] In some possible implementations, when the temperature in the muffle furnace is controlled within a preset temperature range, after heating the sample to be oxidized for a preset time to oxidize the sample to be oxidized, the method further includes:

[0028] The sample to be oxidized is air-cooled to room temperature to stop the oxidation reaction.

[0029] In some possible implementations, the preset temperature range is 500° C. to 700° C., and the preset time length is 3 minutes to 10 minutes.

[0030] In some possible implementations, performing sub-surface defect detection on the B defect position to obtain a sub-surface defect detection result of the steel to be detected includes:

[0031] Embedding a metallographic sample at the B defect position, then grinding to remove the surface coating or metal matrix at the B defect position, and performing a polishing process;

[0032] Performing sub-surface defect detection on the B defect position after polishing through a microscope to obtain sub-surface defect information;

[0033] Based on the sub-surface defect information, a sub-surface defect detection result is determined.

[0034] In some possible implementations, performing sub-surface defect detection on the B defect position after polishing through a microscope to obtain sub-surface defect information includes:

[0035] Performing composition analysis and morphology analysis on the B defect position by electron microscopy;

[0036] Determine the composition of the B defect position according to the component analysis result of the B defect position;

[0037] The determining of the sub-surface defect detection result based on the sub-surface defect information includes:

[0038] The defect type and defect cause are determined based on the component composition in the B defect position.

[0039] The steel sub-surface defect detection method, device, equipment, storage medium and product provided in the embodiment of the present application are as follows: from the steel to be detected, the sample to be detected is cut and divided, and then divided into a sample to be oxidized and a sample to be analyzed, and each divided sample to be detected is marked. In this way, after the subsequent oxidation treatment, it can be ensured that the oxidized and unoxidized sample parts can correspond to each other and be restored to the position state before the segmentation. After the sample to be oxidized is oxidized, its defects are exposed, and the defects of the sample after oxidation are observed to determine the corresponding position on the sample to be analyzed. In this way, even if the defects are not visible in the unoxidized state, they can be located by the marks on the oxidized sample. Afterwards, the possible defect positions on the unoxidized sample are detected, and the defects of the sample to be oxidized are revealed by first performing an oxidation treatment. Then, through the defect position of the sample to be oxidized and the accurate marking and sampling, the defects of the sample to be analyzed are avoided from being destroyed during the detection process, ensuring that the original information of the defects will not be destroyed during the analysis process, thereby obtaining more accurate detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present application can be better understood from the following description of the specific embodiments of the present application in conjunction with the accompanying drawings, in which:

[0041] Other features, objects and advantages of the present application will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings, in which the same or similar reference numerals represent the same or similar features.

[0042] Figure 1 is a flow chart of a steel sub-surface defect detection method provided by an embodiment of the present application;

[0043] Figure 2 This is a schematic diagram of the segmentation mark of the steel to be detected provided in the embodiment of the present application;

[0044] Figure 3 is a schematic diagram of defects of a sample to be detected provided by an embodiment of the present application;

[0045] Figure 4 This is a schematic diagram of determining the position of defect B provided by an embodiment of the present application;

[0046] Figure 5 is an example diagram of an optical microscope image provided in an embodiment of the present application;

[0047] Figure 6 This is an example of a scanning electron microscope image provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] The features and exemplary embodiments of aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0049] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0050] Cold-rolled strip is the main raw material for many industries such as automobile manufacturing, home appliance manufacturing, container manufacturing, and enameled products. With the continuous development of industry, the quality requirements for cold-rolled strip are becoming more and more stringent, and surface defects are an important factor affecting the quality of strip products. However, due to the long production process, thin specifications, and other factors of cold-rolled strip, as well as the reasons of raw materials, rolling equipment, processing technology and system control, various defects are more likely to appear on the surface of cold-rolled strip, the more common ones are linear or strip defects, inclusions, holes, and iron oxide scale indentation. However, some defects exist on the sub-surface after cold rolling, mainly some linear inclusions, which will not be discovered by monitoring means such as surface inspection instruments, and can only be revealed after galvanizing or enameling. However, such linear inclusion defects that occur on the sub-surface and can only be discovered after galvanizing or enameling are often difficult to detect during sampling and testing. On the one hand, it is difficult to select the sampling position for the defect, and on the other hand, due to the presence of coating on the surface, it is easy to destroy the defect when removing the coating from the defect area during detection, and the real information of the defect is lost.

[0051] The inventors have studied the above problems and found that the above problems are caused by the difficulty in locating the defects and selecting the sampling positions. If the sampling positions can be accurately determined, the coating removal in the defect area can be refined to avoid damage to the defects. Therefore, if the positions of sub-surface defects can be accurately determined, the original information of the defects can be preserved, and the defects can be analyzed more accurately.

[0052] In order to solve the problems in the prior art, the present application provides a method for detecting sub-surface defects of steel. The method for detecting sub-surface defects of steel provided in the present application is introduced below.

[0053] Figure 1 FIG. 1 is a flow chart of a method for detecting subsurface defects of steel provided by an embodiment of the present application. Figure 1 As shown, the method includes the following steps S101 to S103.

[0054] Step S101: divide the steel to be tested into two parts according to the rolling direction, and mark the divided samples to be tested. The defect positions of the divided samples to be tested have an associated relationship, and the above mark of each sample represents the position state of the above sample to be tested before the division.

[0055] In the specific implementation, first, the rolling direction of the steel to be tested is determined, and then the steel to be tested is divided into certain lengths according to the rolling direction. Each divided sample to be tested is marked for subsequent testing and data analysis. These marks can be numbers, letters or other symbols, and the position state of the steel before segmentation can be restored according to the marks.

[0056] The defects of the sample to be tested can be linear defects or block defects. Based on a certain sample after segmentation, the location of the defects on other samples can be inferred.

[0057] For example, see Figure 2 ,like Figure 2 As shown, the steel material to be tested is divided into two pieces, wherein the upper sample 201 to be tested is marked with letter "A"; the lower sample 202 to be tested is marked with letter "B". In this way, even if the positions of the two samples to be tested are disrupted in the subsequent processing, the two samples to be tested can be restored to the position state before the division according to the letter markings.

[0058] As another example, the cut samples need to be marked with the upper and lower surfaces, rolling direction and operating side, and marked with restoration marks. After cutting, they need to be spliced ​​and restored and photographed. In addition, the markings of the samples to be oxidized should ensure that they can be identified after oxidation.

[0059] Step S102: dividing the segmented sample to be detected into a sample to be oxidized and a sample to be analyzed.

[0060] The sample to be oxidized may refer to a sample selected to be subjected to surface oxidation treatment to expose defects.

[0061] The sample to be analyzed may be a sample for evaluating the quality of a raw material.

[0062] In a specific implementation, samples that need to be oxidized are randomly determined. Then other samples are classified as samples to be analyzed, or samples that need to be analyzed in detail are selected from samples that have not been oxidized. For example, sample 201 to be detected can be used as a sample to be oxidized; and sample 202 to be detected can be used as a sample to be analyzed.

[0063] Step S103: performing oxidation treatment on the sample to be oxidized, and determining the defect position of the sample to be oxidized, which is recorded as A defect position.

[0064] In a specific implementation, the sample to be oxidized is placed in an appropriate oxidation treatment device, usually a heating furnace or an oxidation chamber. The surface of the sample is exposed to an oxidizing environment, that is, the surface of the sample can be exposed to oxygen, water vapor or other oxidants. The specific oxidation treatment time depends on the required degree of oxidation and the surface characteristics of the sample to be oxidized. After the oxidation treatment, a layer of oxide will form on the surface of the sample, usually showing different colors or textures. After the oxidation treatment is completed, the sample is taken out and the oxidation condition of its surface is observed. By observing the surface of the sample after oxidation treatment, the possible A defect locations are identified. These defects can be surface defects under the oxide layer, such as bubbles, inclusions, etc.

[0065] For example, see Figure 3 ,like Figure 3 As shown, after oxidation, defective portion 2011 and defective portion 2031 appear in the sample 201 to be tested, and the position of this defect is defect position A.

[0066] In some embodiments, in order to quickly oxidize the sample to be oxidized, the above S103 may include steps A1 to C1:

[0067] Step A1: When the temperature in the muffle furnace reaches a preset temperature, the sample to be oxidized is placed in the muffle furnace.

[0068] In the specific implementation, select the samples that need to be surface oxidized from the steel to be tested, and ensure that their surfaces are clean and free of oil or other contaminants. According to the size, material and oxidation requirements of the samples to be oxidized, adjust the heating parameters of the muffle furnace, such as heating power, heating time and heating rate. After the temperature in the muffle furnace reaches the preset temperature, place the samples to be oxidized in the furnace. In order to avoid mutual interference or contact between samples, a suitable sample holder or bracket can be used to place the samples in the furnace.

[0069] Step B1: while controlling the temperature in the muffle furnace to be within a preset temperature range, heating the sample to be oxidized for a preset time to oxidize the sample to be oxidized.

[0070] In a specific implementation, once the temperature in the muffle furnace approaches the preset temperature range, the temperature change is continuously monitored, and the heating power is adjusted as needed to ensure that the temperature can be stabilized within the required range. Once the temperature in the muffle furnace is stabilized within the preset temperature range, a timer is started to ensure that the sample to be oxidized is fully heated within the preset time.

[0071] Step C1: According to the surface condition of the sample to be oxidized after oxidation, the defect position of the sample to be oxidized is determined, and recorded as A defect position.

[0072] In specific implementation, the surface image of the sample to be oxidized can be digitized and defect analysis can be performed using image analysis software. Potential defect locations can be identified by calculating and comparing features such as texture, color change, and concave and convex conditions on the sample surface.

[0073] As another example, surface defect detection equipment, such as an infrared scanner, ultrasonic detection equipment, or magnetic particle detection device, can be used to perform a comprehensive scan and detection on the sample to be oxidized, thereby discovering defects such as cracks, pores, and inclusions on the sample surface.

[0074] The above method of the embodiment of the present application is to place the sample to be oxidized in the muffle furnace when the temperature in the muffle furnace reaches a preset temperature, and then heat the sample to be oxidized by the muffle furnace for a preset time. According to the surface condition of the sample to be oxidized after oxidation, the defect position of the sample to be oxidized can be determined, which is recorded as A defect position. Heating by a muffle furnace can quickly oxidize the sample to be oxidized.

[0075] In some embodiments, in order to reduce the impact of the cooling process on the sample to be oxidized, after step B1, the method further includes:

[0076] The sample to be oxidized is air-cooled to room temperature to stop the oxidation reaction.

[0077] In a specific implementation, the heating system of the muffle furnace is stopped, and after the temperature in the muffle furnace gradually drops to a safe range, the door of the muffle furnace is opened to allow room temperature air to enter the furnace and allow the sample to be oxidized to contact the external environment. The sample to be oxidized is placed in the muffle furnace and allowed to cool naturally to room temperature.

[0078] The above-mentioned method of the embodiment of the present application can reduce the impact of the cooling process on the sample to be oxidized by air cooling the sample to be oxidized to room temperature after heating in the muffle furnace.

[0079] In some embodiments, in order to oxidize the sample to be oxidized to a suitable degree, the preset temperature range is 500° C. to 700° C., and the preset time is 3 minutes to 10 minutes.

[0080] Step S104: according to the positional relationship between the marks of the sample to be oxidized and the sample to be analyzed, and the defect position A, the defect position B of the sample to be analyzed is determined.

[0081] In a specific implementation, the sample to be analyzed is compared with the sample to be oxidized according to the mark, and the corresponding reference point on the sample to be analyzed is determined according to the mark of the sample to be oxidized and the defect position A. Thus, the defect position of the sample to be oxidized is recorded as the defect position A, and the possible defect position B is determined on the sample to be analyzed.

[0082] In some implementations, in order to accurately obtain the B defect position, the above S104 may include steps A2 to B2:

[0083] Step A2: According to the above-mentioned marks, the above-mentioned sample to be oxidized and the above-mentioned sample to be analyzed are matched based on the position state before segmentation.

[0084] In a specific implementation, the segmented sample to be oxidized is matched with the sample to be analyzed according to the previous markings and records, and it is confirmed whether the position state between the sample to be oxidized and the sample to be analyzed is correct.

[0085] Step B2: Based on the above-mentioned defect position A and the position state before segmentation, the corresponding position of the above-mentioned sample to be analyzed is determined as the defect position B.

[0086] In the specific implementation, the possible position of defect B on the sample to be analyzed is determined based on the mark of defect A and the position state before segmentation. Since subsurface defects may be cut off when segmenting steel, the defect at the edge of the sample to be oxidized may be part of a defect, and the other part of the defect is at the corresponding position of the sample to be analyzed. For details, please refer to Figure 4 For the defective part 2011 and the defective part 2031, the possible defective parts 2021 and 2041 can be determined correspondingly, and their positions are the B defect positions.

[0087] In the above method of the embodiment of the present application, according to the previous marking, the above sample to be oxidized and the above sample to be analyzed are matched based on the position state before segmentation, and then based on the position state before segmentation, according to the A defect position, the corresponding position on the sample to be analyzed is determined as the B defect position. The B defect position can be accurately obtained.

[0088] In some embodiments, in order to accurately match the sample to be oxidized with the sample to be analyzed, the above A2 includes steps A3 to B3:

[0089] Step A3: According to the above markings, the sample to be oxidized and the sample to be analyzed are spliced.

[0090] In a specific implementation, the marking positions of the sample to be oxidized and the sample to be analyzed are aligned according to the previous markings, and then the sample to be oxidized and the sample to be analyzed are spliced.

[0091] Step B3: according to the positional relationship between the spliced ​​sample to be oxidized and the sample to be analyzed, the sample to be oxidized and the adjacent sample to be analyzed are matched.

[0092] In a specific implementation, the corresponding relationship between the sample to be oxidized and the adjacent sample to be analyzed is determined according to the actual positional relationship between the spliced ​​sample to be oxidized and the sample to be analyzed.

[0093] The above method of the embodiment of the present application can accurately correspond the sample to be oxidized and the sample to be analyzed by splicing the sample to be oxidized and the sample to be analyzed to the state before the split according to the mark, and then determining the correspondence between the sample to be oxidized and the adjacent sample to be analyzed according to the positional relationship between the spliced ​​sample to be oxidized and the sample to be analyzed.

[0094] In some embodiments, in order to accurately determine the B defect position, when the A defect position is a linear defect related to the rolling direction, the B2 includes steps A4 to B4:

[0095] Step A4: Based on the above-mentioned defect position A, an extension line of the above-mentioned defect position A is made toward the above-mentioned sample to be analyzed according to the position state before segmentation.

[0096] In the specific implementation, the linear defect is generally formed during the rolling movement and is in the same direction as the rolling direction. After determining the position of the A defect, an extension line related to the defect is drawn on the sample to be analyzed in the direction of the A defect position.

[0097] Step B4: Determine the position of the extension line on the sample to be analyzed as defect position B.

[0098] In the above method of the embodiment of the present application, when the defect position A is a linear defect related to the rolling direction, an extension line is drawn from the defect position A to the sample to be analyzed according to the position state before segmentation, and the position of the extension line on the sample to be analyzed is determined as the defect position B. The extension line of the linear defect can accurately determine the defect position B.

[0099] In some embodiments, in order to detect linear defects in the steel to be inspected with the highest probability, the above S101 includes steps A5 to B5:

[0100] Step A5: Split the steel to be tested into two parts perpendicular to the rolling direction.

[0101] In a specific implementation, if the linear defects of the steel need to be detected, that is, the long strip defects in the same rolling direction, the positions to be segmented can be marked on the steel to be detected perpendicular to the rolling direction. Then, the steel to be detected is segmented according to the marked positions.

[0102] Step B5: Mark the segmented samples to be tested.

[0103] In the above-mentioned method of the embodiment of the present application, when the position of the A defect to be detected is a linear defect related to the rolling direction, the steel to be detected is segmented perpendicular to the rolling direction during segmentation, so as to segment the linear defects that may exist in the steel to be detected to the greatest extent, and then mark the segmented samples to be detected. The linear defects in the steel to be detected can be detected with the highest probability.

[0104] Step S105: performing sub-surface defect detection on the above-mentioned B defect position to obtain the sub-surface defect detection result of the above-mentioned steel to be detected.

[0105] In a specific implementation, prepare appropriate equipment for subsurface defect detection. Use the equipment to perform subsurface defect detection. Scan or spot-detect the area around the B defect location to detect possible subsurface defects, such as pores, inclusions, cracks, etc. Analyze and process the data obtained from the detection to identify and evaluate the type, location, size and severity of the subsurface defects. According to the detection results, perform necessary classification and marking for subsequent processing and analysis.

[0106] As another example, if necessary, necessary surface preparation work may be performed around the B defect location, such as cleaning the surface, removing dirt and coatings, adjusting surface roughness, etc.

[0107] In some embodiments, in order to accurately determine the sub-surface defect detection result, the above S105 includes steps A6 to C6:

[0108] Step A6: embedding a metallographic sample at the above-mentioned defect position B, then grinding to remove the surface coating or metal matrix at the above-mentioned defect position B, and performing polishing.

[0109] In the specific implementation, the selected grinding equipment and materials are used to mount the metallographic sample at the B defect position, and then the grinding operation is performed to ensure that the grinding surface is flat and uniform, and the surface coating is gradually removed until the sub-surface below is exposed. The grinding effect is checked regularly to ensure that the coating has been completely removed.

[0110] Step B6: Perform sub-surface defect detection on the B defect position after polishing through a microscope to obtain sub-surface defect information.

[0111] In the specific implementation, according to the type and size of the defect to be detected, a suitable microscope is selected, such as an optical microscope or a microscopic X-ray imaging system. The position of the B defect after polishing is observed through a microscope, and the image of the sub-surface defect is recorded to obtain the sub-surface defect information.

[0112] For example, an optical microscope can be used to observe and obtain an optical image of the defect, such as Figure 5 shown.

[0113] Step C6: Based on the above sub-surface defect information, determine the sub-surface defect detection result.

[0114] In a specific implementation, the defects are classified and evaluated according to the sub-surface defect information observed by the microscope, and the determined sub-surface defect detection results are recorded to obtain the sub-surface defect detection results.

[0115] The above method of the embodiment of the present application is to remove the surface coating or metal matrix of the above B defect position by embedding the metallographic sample at the above B defect position, and then polishing it, so that the sub-surface defect detection can be performed on the polished B defect position using a microscope to obtain sub-surface defect information. Then, based on the above sub-surface defect information, the sub-surface defect detection result is determined. After polishing, the sub-surface defect detection of the B defect position is performed by a microscope, so as to detect and obtain the sub-surface defect information, and then the sub-surface defect detection result can be accurately determined.

[0116] In some embodiments, in order to accurately determine the defect type and defect cause, the above B6 includes steps A7 to B7:

[0117] Step A7: Perform composition analysis and morphology analysis on the above-mentioned B defect position through electron microscopy.

[0118] In the specific implementation, the component analysis results and morphology of the B defect position are collected by using an electron microscope combined with a component analysis result analyzer.

[0119] Step B7: According to the component analysis result of the above-mentioned B defect position, determine the component composition and defect type in the above-mentioned B defect position.

[0120] In the specific implementation, the collected component analysis result data is processed, the peak values ​​of the elements are identified, and their relative intensities are measured. For each identified peak, its area or peak intensity is measured. The peak area is proportional to the amount of the corresponding element present, so it can be used to estimate the content of the element in the sample. The peak area of ​​each element in the B defect position is converted into the corresponding content. In this way, the composition of the component, that is, the ratio of the content of each element, can be determined.

[0121] For example, if Figure 6 As shown, Figure 6 This is the electron image of the B defect position after the composition analysis by scanning electron microscope. According to the spectrum, the specific element content can be obtained, as shown in Table 1.

[0122] Table 1

[0123] Spectrum C O Al Ti Fe total Spectrum Figure 1 0.01 19.12 18.70 1.46 60.71 100.00 Spectrum Figure 2 0.02 44.40 41.24 0.00 14.35 100.00 Spectrum Figure 3 0.03 50.85 46.04 0.65 2.43 100.00 Spectrum Figure 4 0.02 50.20 47.07 0.94 1.77 100.00

[0124] The above-mentioned determination of the sub-surface defect detection result based on the above-mentioned sub-surface defect information includes:

[0125] According to the composition of the above B defect position, the defect type and defect cause are determined.

[0126] In the specific implementation, the possible defect types are inferred based on the analyzed elemental composition and the reference of the steel rolling process. For example, if a high content of alumina is found in the B defect position, it may indicate the presence of surface defects such as alumina inclusions; if an abnormal carbon content occurs, it may involve internal defects such as carbides or carbon segregation. Combined with the inference of the defect type, the possible causes of the defects are analyzed. This requires taking into account factors such as the chemical composition, process parameters, and operating conditions of the material to further infer the causes of the defect formation. For example, a high alumina content may be due to the fact that alumina was not completely removed during the smelting process, floated to the surface or subsurface during the solidification of the slab, or the protective casting was not done well, resulting in aluminum oxidation in the steel; abnormal carbon content may be due to improper process parameters or rolling temperature control errors, etc.

[0127] In the above method of the embodiment of the present application, a scanning electron microscope is used to perform component analysis and morphology analysis on the B defect position, and the component composition in the B defect position is determined by the obtained component analysis result, and then the defect type and defect cause can be determined according to the component composition in the above B defect position. The defect type and defect cause can be accurately determined by analyzing the component analysis result.

[0128] In the embodiment of the present application, a sample to be tested is cut from the target steel material and divided, and then divided into a sample to be oxidized and a sample to be analyzed, and each divided sample to be tested is marked. In this way, after the subsequent oxidation treatment, it can be ensured that the oxidized and unoxidized sample parts can correspond to each other and be restored to the position state before the division. After the sample to be oxidized is oxidized, its defects are exposed, and the defects of the oxidized sample are observed to determine the corresponding position on the sample to be analyzed. In this way, even if the defects are not visible in the unoxidized state, they can be located by the marks on the oxidized sample. Afterwards, the possible defect positions on the unoxidized sample are detected, and the defects of the sample to be oxidized are revealed by first performing an oxidation treatment. Then, through the defect positions of the sample to be oxidized and accurate marking and sampling, the defects of the sample to be analyzed are avoided from being destroyed during the detection process, ensuring that the original information of the defects will not be destroyed during the analysis process.

[0129] It should be clear that the present application is not limited to the specific configuration and processing described above and shown in the figures. For the sake of simplicity, a detailed description of the known method is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present application is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present application.

[0130] It should also be noted that the exemplary embodiments mentioned in this application describe some methods or systems based on a series of steps or devices. However, this application is not limited to the order of the above steps, that is, the steps can be performed in the order mentioned in the embodiment, or in a different order from the embodiment, or several steps can be performed simultaneously.

[0131] The above is only a specific implementation of the present application. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the systems, modules and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here. It should be understood that the protection scope of the present application is not limited to this. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in this application, and these modifications or replacements should be included in the protection scope of this application.

Claims

1. A method for detecting sub-surface defects of steel, characterized in that: include: The steel to be tested is divided into two parts according to the rolling direction, and the divided samples to be tested are marked, wherein the defect positions of the divided samples to be tested have an associated relationship, and the mark of each sample to be tested represents the position state of the sample to be tested before the division; Splitting the sample to be detected into two samples, namely a sample to be oxidized and a sample to be analyzed; Performing oxidation treatment on the sample to be oxidized, and determining the defect position of the sample to be oxidized, which is recorded as A defect position; Determine the B defect position of the sample to be analyzed according to the positional relationship between the marks of the sample to be oxidized and the sample to be analyzed, and the A defect position; Sub-surface defect detection is performed on the B defect position to obtain a sub-surface defect detection result of the steel to be detected.

2. The steel subsurface defect detection method according to claim 1, characterized in that: Determining the B defect position of the sample to be analyzed according to the positional relationship between the marks of the sample to be oxidized and the sample to be analyzed, and the A defect position, comprises: According to the mark, the sample to be oxidized and the sample to be analyzed are matched based on the position state before segmentation; Based on the A defect position and the position state before segmentation, the corresponding position of the sample to be analyzed is determined as the B defect position.

3. The steel subsurface defect detection method according to claim 2, characterized in that: According to the mark, the sample to be oxidized and the sample to be analyzed are matched based on the position state before segmentation, including: According to the label, the sample to be oxidized and the sample to be analyzed are spliced; According to the positional relationship between the spliced ​​sample to be oxidized and the sample to be analyzed, the sample to be oxidized and the adjacent sample to be analyzed are matched.

4. The steel subsurface defect detection method according to claim 2, characterized in that: The A defect position is a linear defect related to the rolling direction, and based on the A defect position and the position state before segmentation, the corresponding position of the sample to be analyzed is determined as the B defect position, including: Based on the A defect position, according to the position state before segmentation, an extension line of the A defect position is drawn toward the sample to be analyzed; The position of the extended line on the sample to be analyzed is determined as the B defect position.

5. The steel subsurface defect detection method according to claim 4, characterized in that: The method of dividing the steel to be tested into two parts according to the rolling direction and marking the divided samples to be tested includes: Split the steel to be tested into two parts perpendicular to the rolling direction; The segmented samples to be tested are marked.

6. The steel subsurface defect detection method according to claim 1, characterized in that: The step of performing oxidation treatment on the sample to be oxidized and determining a defect position of the sample to be oxidized, recorded as A defect position, includes: When the temperature in the muffle furnace reaches a preset temperature, placing the sample to be oxidized into the muffle furnace; While controlling the temperature in the muffle furnace to be within a preset temperature range, heating the sample to be oxidized for a preset time to oxidize the sample to be oxidized; According to the surface condition of the sample to be oxidized after oxidation, the defect position of the sample to be oxidized is determined and recorded as A defect position.

7. The steel sub-surface defect detection method according to claim 6, characterized in that: In the case of controlling the temperature in the muffle furnace within a preset temperature range, after heating the sample to be oxidized for a preset time to oxidize the sample to be oxidized, the method further includes: The sample to be oxidized is air-cooled to room temperature to stop the oxidation reaction.

8. The steel sub-surface defect detection method according to claim 6, characterized in that: The preset temperature range is 500° C. to 700° C., and the preset time length is 3 minutes to 10 minutes.

9. The steel sub-surface defect detection method according to any one of claims 1 to 8, characterized in that: The sub-surface defect detection is performed on the B defect position to obtain the sub-surface defect detection result of the steel to be detected, including: Embedding a metallographic sample at the B defect position, then grinding to remove the surface coating or metal matrix at the B defect position, and performing a polishing process; Performing sub-surface defect detection on the B defect position after polishing through a microscope to obtain sub-surface defect information; Based on the sub-surface defect information, a sub-surface defect detection result is determined.

10. The steel sub-surface defect detection method according to claim 9, characterized in that: The sub-surface defect detection is performed on the B defect position after polishing by a microscope to obtain sub-surface defect information, including: Performing composition analysis and morphology analysis on the B defect position by electron microscopy; Determine the composition of the B defect position according to the component analysis result of the B defect position; The determining of the sub-surface defect detection result based on the sub-surface defect information includes: The defect type and defect cause are determined based on the component composition in the B defect position.

Images