A method for segregation and quantitative characterization of banded tissue

Abstract

This invention discloses a method for the segregation and quantitative characterization of banded structures. The method includes: preparing a cross-sectional sample of a plate; performing component distribution analysis on the cross-sectional sample using X-ray fluorescence spectrometry to obtain a characteristic element content distribution spectrum; based on the characteristic element content distribution spectrum, selecting characteristic elements with obvious banded segregation characteristics for linear distribution quantitative characterization to obtain a characteristic element content line distribution map; and quantitatively calculating the band parameters of the banded structure, wherein the band parameters include the spacing between two adjacent banded structures and the width of the banded structure. This invention uses X-ray fluorescence spectrometry to analyze the elemental composition distribution of the plate, quantitatively calculates the band parameters of the banded structure, simplifies sample preparation, eliminates the need for surface polishing or chemical treatment of the sample, and allows the observation field to cover the entire plate thickness.

Description

Technical Field

[0001] This invention relates to the field of metal material composition and fiber structure analysis technology, and in particular to a method for the segregation and quantitative characterization of banded structures. Background Technology

[0002] During the plastic processing of metallic materials, a segregated structure often exists within the material, consisting of bands arranged roughly parallel to the direction of deformation. For example, in hot-rolled low-carbon structural steel, ferrite and pearlite are arranged parallel to the rolling direction, layered, and banded. This is because during the cooling process after hot rolling, ferrite preferentially forms in bands formed by dendritic segregation and non-metallic inclusions, resulting in ferrite banding. Pearlite lies between the ferrite bands, and the two are distributed alternately in layers. The presence of banded structure makes the microstructure of the metal sheet uneven. Under external force, bands with poorer properties become weak areas, and stress concentration occurs between strong and weak bands, leading to anisotropy. This reduces the material's plasticity, impact toughness, and reduction of area, causing adverse consequences such as incomplete cold bending, high stamping scrap rates, and easy deformation during heat treatment, thus affecting the service life of the finished product. For instance, steel products containing banded structure are prone to cracking along the boundary between ferrite and pearlite bands during service, severely shortening the product's service life. In addition, steel containing banded structures often contains slender inclusions, which can reduce the transverse plasticity and toughness of steel products. Therefore, it is necessary to quantitatively characterize the banded structure segregation and band parameters.

[0003] Currently, the commonly used method for evaluating banded structures is the comparative method and standard rating chart in GB / T 34474.1-2017 "Evaluation of Banded Structures in Steel Part 1: Standard Rating Chart Method". When evaluating banded structures, samples are first cut and subjected to progressive grinding, polishing, and etching to find the field of view where the banded structure is most severe on the test surface. Then, the banded structure level is determined by manual comparison with the standard rating chart. This method often selects a small local metallographic sample, which undergoes coarse grinding, fine grinding, polishing, and chemical etching before observation using an optical microscope. The sample preparation requirements are high, and the observation field of view is limited. Single-field or local multi-field observation cannot reflect the overall degree and characteristics of banded structure segregation in the plate. The evaluation results are affected by factors such as sample selection, corrosion degree, and human evaluation errors, resulting in significant uncertainty and large fluctuations in the banded structure evaluation results. In the analysis of elemental composition distribution of banded structures, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) or electron probe microanalysis (EPMA) is often used to measure the micro-area composition of the banded structure. This method usually requires the sample to undergo coarse grinding, fine grinding, polishing, and chemical etching. At the same time, the surface to be tested must be dry, have good thermal stability, good electrical conductivity, and be free of strong magnetism. The test results are often micro-area compositional distributions, which are difficult to map in situ with the banded structure in metallographic microscopy. Furthermore, because SEM has requirements on sample size, it is impossible to observe the compositional distribution characteristics of the banded structure across the entire cross-section of large-sized plates. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the segregation and quantitative characterization of banded structures, which can effectively solve the above-mentioned problems and perform quantitative statistical characterization of band parameters such as elemental composition distribution, band spacing, and band width of banded structures in metal plates.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A method for segregation and quantitative characterization of banded tissue, comprising the following steps:

[0007] Prepare plate cross-section specimens;

[0008] X-ray fluorescence spectrometry was used to analyze the compositional distribution of the plate cross-section sample, and the characteristic element content distribution spectrum of the plate cross-section sample was obtained.

[0009] Based on the distribution map of characteristic element content, characteristic elements with obvious banded segregation characteristics are selected for quantitative characterization of linear distribution to obtain a linear distribution map of characteristic element content. The band parameters of the banded tissue are quantitatively statistically analyzed, including the band spacing between two adjacent regions and the band width.

[0010] Furthermore, the preparation of the plate cross-section sample includes: cutting the plate cross-section sample and grinding the cross-section of the plate cross-section sample to be tested.

[0011] Furthermore, the thickness range of the plate cross-section sample can reach 0.2 mm to 190 mm, covering the thickness range of thin plates, medium-thick plates, thick plates and extra-thick plates. The test section of the plate cross-section sample is cut along the cross-sectional direction parallel to the forging and rolling direction, or cut along the longitudinal section direction perpendicular to the forging and rolling direction. The size of the test section covers the entire thickness direction of the plate cross-section sample.

[0012] Furthermore, the step of using X-ray fluorescence spectrometry to perform compositional distribution analysis on the plate cross-section sample to obtain a characteristic element content distribution spectrum of the plate cross-section sample includes:

[0013] The cross-section of the plate sample was scanned using an X-ray fluorescence spectrometer.

[0014] The scanning range is either a local area or the entire thickness direction of the plate cross-section sample;

[0015] The characteristic elements in the obtained characteristic element content distribution spectrum include all elements of the plate section sample.

[0016] Furthermore, the step of scanning the test section of the plate cross-section sample using an X-ray fluorescence spectrometer includes:

[0017] The scanning direction is adjusted by adjusting the angle based on the distribution map of characteristic elements so that the boundary of the banded tissue is parallel to the X direction, and the segregation of the banded tissue in the selected area can be obtained in a single measurement.

[0018] Furthermore, the spacing between the banded tissues includes the maximum spacing d between the banded tissues. max Average spacing d ave The width of the band-like tissue includes the maximum width W of the band-like tissue. max Average width W ave .

[0019] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: The method for segregation and quantitative characterization of banded tissue provided by the present invention has the following beneficial effects compared with the prior art:

[0020] First, based on the characteristics of metal sheet processing deformation and the phenomenon that the chemical composition of characteristic elements in local areas differs from that in surrounding areas, this invention calculates the parameters by means of the surface distribution map of characteristic element content. Compared with traditional metallographic and scanning electron microscopy methods, this invention does not have high requirements for the surface condition of the sample being tested, and the sample preparation is simpler. The surface with the required roughness can be ground by a grinding machine, without the need for polishing and chemical etching of the sample surface.

[0021] Secondly, the present invention can obtain the compositional distribution information of characteristic elements over a large range (covering the entire thickness direction of the plate section) using an X-ray fluorescence spectrometer. A single scan can obtain full elemental information, and band parameters can be statistically analyzed based on the surface distribution map of characteristic element content, which greatly improves the detection efficiency of banded tissue segregation. Furthermore, since the surface distribution map of characteristic element content can cover the entire thickness direction of the plate, the detection efficiency is high, the statistical field of view is large, and the information is more comprehensive.

[0022] Third, this invention uses X-ray fluorescence spectroscopy to focus X-rays through a multi-channel capillary, which can produce a very small spot while ensuring fluorescence intensity. It can also achieve high throughput of fluorescence signals without affecting energy resolution, resulting in high spatial resolution and more reliable analysis data. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of the method for segregation and quantitative characterization of banded tissues according to the present invention;

[0025] Figure 2 This is a two-dimensional distribution diagram of the Fe content, a characteristic element in the longitudinal section of the hot-rolled steel plate, in an embodiment of the present invention.

[0026] Figure 3 This is a two-dimensional distribution diagram of the Mn content of the characteristic element in the longitudinal section of the hot-rolled steel plate in an embodiment of the present invention;

[0027] Figure 4 This is a two-dimensional distribution diagram of the Cu content, a characteristic element in the longitudinal section of a hot-rolled steel plate, in an embodiment of the present invention.

[0028] Figure 5 This is a line distribution diagram of Cu element content in the longitudinal section feature map of hot-rolled steel plate in an embodiment of the present invention;

[0029] Figure 6 The metallographic structure of the upper part of the longitudinal section of the hot-rolled steel plate in this embodiment of the invention;

[0030] Figure 7 This is the metallographic structure of the middle section of the longitudinal section of the hot-rolled steel plate in the embodiment of the present invention;

[0031] Figure 8 This is the metallographic structure of the lower part of the longitudinal section of the hot-rolled steel plate in the embodiment of the present invention;

[0032] Figure 9This is a measurement of banded segregation structure in the metallographic structure of hot-rolled steel plate in an embodiment of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The purpose of this invention is to provide a method for the segregation and quantitative characterization of banded structures. The elemental composition distribution of the plate was analyzed by X-ray fluorescence spectrometry, and the band parameters of the banded structures were quantitatively statistically analyzed. The sample preparation is simple, and there is no need to polish or chemically treat the sample. Moreover, the observation field can cover the entire plate thickness.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] like Figure 1 As shown, the method for segregation and quantitative characterization of banded tissue provided by the present invention includes the following steps:

[0037] The preparation of plate cross-section specimens includes: cutting plate cross-section specimens and grinding the test section of the plate cross-section specimens;

[0038] X-ray fluorescence spectrometry was used to analyze the compositional distribution of the plate cross-section sample, and the characteristic element content distribution spectrum of the plate cross-section sample was obtained.

[0039] Based on the characteristic element content distribution map, characteristic elements with obvious banded segregation characteristics are selected for quantitative linear distribution characterization to obtain the characteristic element content line distribution map. The band parameters of the banded tissue are then quantitatively analyzed, including the band spacing between two adjacent regions and the band width. Specifically, based on the characteristic element content line distribution map (e.g., ... Figure 5 Record the location where the content of the characteristic element reaches a regional extreme value. For example, if the location where the content of the characteristic element reaches a maximum value is x1, and the location immediately adjacent to the maximum value is x2, then the band spacing d = x2 - x1 - W ave The maximum spacing of the banded tissues within the entire cross-sectional test area is d. max Within the test area, the distance between the (n-1)th and nth banded tissues is d. n-1 =x n -x n-1 -W ave x nThe x-coordinate value at the nth maximum value represents the average spacing d of the banded tissues within the test area. ave =(d1+d2·····d n-1 ) / (n-1); The intercept W between the peak where the characteristic element maximum value is located and the average content of the characteristic element measured by X-ray fluorescence spectroscopy (for example, 0.43 wt.%) is the width of the banded tissue, and the maximum width of the banded tissue in the test area is W. max Within the test area, the width of the m-th band of tissue is denoted as W. m Average width W of banded tissue ave =(W1+W2+·····+W m ) / m. If there is no intercept with the average content of characteristic elements at the 1st and mth peak positions, it is not counted. Determine the maximum spacing d of the banded tissue. max Average spacing d ave The maximum width W of the banded tissue max Average width W ave Parameters such as band.

[0040] The thickness of the plate cross-section sample can range from 0.2 mm to 190 mm, covering the thickness range of thin, medium, thick, and extra-thick plates. The test section of the plate cross-section sample is taken along a cross-sectional direction parallel to the forging and rolling direction, or perpendicular to the forging and rolling direction. The size of the test section can cover the entire thickness direction of the plate as needed. For example, in a specific embodiment, a longitudinal cross-section sample with a cross-sectional size of 16 mm × 20 mm is selected and taken parallel to the rolling direction of the hot-rolled plate. The test surface is then ground using a grinding machine to achieve a surface roughness R. a ≤0.2.

[0041] The step of using X-ray fluorescence spectrometry to analyze the compositional distribution of the plate cross-section sample and obtaining the characteristic element content distribution spectrum of the plate cross-section sample includes:

[0042] The cross section of the plate sample was scanned using an X-ray fluorescence spectrometer. The scanning direction was adjusted according to the surface distribution map of characteristic element content so that the boundary of the banded structure was parallel to the X-ray direction. The segregation of the banded structure in the selected area could be obtained in a single measurement.

[0043] The scanning range is either a local area or the entire thickness direction of the plate cross-section sample;

[0044] The characteristic elements in the obtained characteristic element content distribution spectrum include all elements of the plate section sample.

[0045] Imaging effects can be optimized and the segregation of banded tissue can be obtained by adjusting parameters such as X-ray tube voltage, current, beam spot scanning interval, and single-pixel acquisition time. For example, the operating parameters for scanning the test section of a plate cross-section sample using an X-ray fluorescence spectrometer are as follows:

[0046] The scanning area was set to 4 mm × 4 mm, the X-ray tube voltage was set to 40 kV, the current to 150 µA, the single pixel acquisition time to 100 ms, the vacuum level to 20 mbar, and the beam spot scanning interval to 40 μm.

[0047] Taking the longitudinal section of hot-rolled steel plate as an example, the obtained characteristic element content distribution map includes: Figure 2-4 As shown, Figure 2 It is a two-dimensional distribution diagram of the Fe content, a characteristic element in the longitudinal section of hot-rolled steel plate; Figure 3 It is a two-dimensional distribution diagram of the Mn content, a characteristic element in the longitudinal section of hot-rolled steel plate; Figure 4 This is a two-dimensional distribution diagram of the Cu content, a characteristic element in the longitudinal section of a hot-rolled steel plate.

[0048] The average content of each characteristic element in the characteristic element content distribution map is shown in Table 1.

[0049]

[0050] Based on the distribution map of characteristic elements, the banded segregation of the tested section can be observed in a single test, according to the line distribution map of characteristic elements (such as Cu). Figure 5 (As shown) Calculate the spacing and width of the banded tissue between two adjacent regions, and quantitatively count the maximum spacing d of the banded tissue. max Average spacing d ave The maximum width W of the banded tissue max Average width W ave The average result contains at least 20 banded tissues, and the quantitative statistical results are shown in Table 2. For plates with a small number of banded tissues in the selected area, quantitative statistics can be performed by selecting characteristic element line distribution maps at different locations, using the same method as described above.

[0051] Comparative example: Metallography

[0052] Step 1: Preparation and surface treatment of hot-rolled sheet samples. A longitudinal section sample with dimensions of 16 mm × 20 mm was cut along the rolling direction of the sheet. The surface to be tested was then ground using a grinding machine to achieve a surface roughness R. a ≤0.2. Grind on a metallographic grinding machine using 60#, 200#, 400#, 800# and 1000# abrasive in successive stages, polish with 2.5 mesh diamond polishing paste, etch with 4% nitric acid alcohol solution, clean and dry for later use.

[0053] Step 2: Observe the metallographic structure under a metallographic microscope, such as... Figures 6-8 As shown, the banded segregation characteristics in the metallographic structure obtained by metallography are basically consistent with the distribution patterns of characteristic elements (Mn, Cu, Fe) obtained by X-ray fluorescence spectroscopy. Therefore, the distribution of these characteristic elements can be used to identify banded segregation.

[0054] Step 3: Select a multi-field metallographic structure and measure the maximum spacing d of the banded structures using metallographic microscope quantitative analysis software. max Average spacing d ave The maximum width W of the banded tissue max Average width W ave (like Figure 9 As shown in Table 2), the average results contain at least 20 band-like tissues, and the quantitative statistical results are shown in Table 2.

[0055]

[0056] As can be seen from Table 2, the maximum spacing d of the banded tissues measured by X-ray fluorescence spectroscopy and metallography... max Minimum spacing d min Average spacing d ave Average width W of banded tissue ave The results are quite close, with an error within 10%, indicating that the X-ray fluorescence spectroscopy method of this invention has good consistency with the metallographic method. The method has good reliability for quantitative characterization of banded tissue segregation and band parameters. Moreover, compared with the metallographic method, it does not require polishing and chemical etching of the sample surface, giving full play to the advantages of X-ray fluorescence spectroscopy and improving analytical efficiency and accuracy.

[0057] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for banding segregation and quantitative characterization, characterized in that, The method comprises the following steps: preparing a plate cross-section sample; performing component distribution analysis on the plate cross-section sample by using an X-ray fluorescence spectrometer to obtain a characteristic element content distribution graph of the plate cross-section sample; Based on the characteristic element content distribution map, the characteristic element with obvious banding segregation characteristics is selected for linear distribution quantitative characterization, the characteristic element content linear distribution map is obtained, and the band parameters of the band structure are quantitatively counted, the band parameters include the band structure spacing of two adjacent regions and the band structure width; wherein, according to the characteristic element content linear distribution map, the position of the extreme value of the characteristic element content appearing region is recorded, and the position of the extreme value of the characteristic element content appearing region is x 1， The position close to the extreme value of the content is x 2， Then the band structure spacing d=x2-x1-W ave， The maximum value of the band structure spacing d in the whole cross-section test area is d max； In the test area, the spacing of the n-1th and nth band structure is d n-1 =x n -x n-1 -W ave , x n is the horizontal coordinate value of the nth maximum value, the average spacing d of the band structure in the test area is d ave = (d1+d2······d n-1 ) / (n-1); the intercept W of the wave peak where the characteristic element maximum value is located and the average content of the characteristic element tested by the X-ray fluorescence spectrometry is the band structure width, the maximum value of the band structure width W in the test area is W max ; in the test area, the width of the mth band structure is recorded as W m , the average width W of the band structure is W ave =(W1+W2+······+W m ) / m, and if there is no intercept with the average content of the characteristic element at the position of the first and mth wave peak, it is not counted; the average result contains at least 20 band structures.

2. The method of banding segregation and quantification according to claim 1, wherein, the plate cross-section sample is prepared by cutting the plate cross-section sample and performing grinding treatment on a to-be-tested cross section of the plate cross-section sample.

3. The method of banding segregation and quantification according to claim 1, wherein The thickness of the plate cross-section sample can range from 0.2 mm to 190 mm, covering the thickness size range of thin plates, medium-thick plates, thick plates and extra-thick plates, the to-be-tested cross section of the plate cross-section sample is cut along a cross section direction parallel to a forging or rolling direction, and the size of the to-be-tested cross section can cover the entire thickness direction of the plate cross-section sample.

4. The method of banding and quantitative characterization according to claim 1, wherein, The component distribution analysis on the plate cross-section sample by using the X-ray fluorescence spectrometer to obtain the characteristic element content distribution graph of the plate cross-section sample comprises the following steps: scanning the to-be-tested cross section of the plate cross-section sample by using the X-ray fluorescence spectrometer; the scanning range is a local area or the entire thickness direction of the plate cross-section sample; the characteristic elements in the obtained characteristic element content distribution graph include all elements of the plate cross-section sample.

5. The method of banding and quantitative characterization according to claim 1, wherein, The banding tissue spacing comprises a banding tissue maximum spacing d max , an average spacing d ave The banding tissue width comprises a banding tissue maximum width W max , an average width W ave .

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