Quantitative evaluation method for martensite structure of ground rail head

Abstract

The application provides a quantitative evaluation method for martensite structure of a ground rail surface, and belongs to the technical field of rail maintenance. The quantitative evaluation method comprises the following steps: selecting a ground rail, cutting a sample with a predetermined length along the longitudinal direction of the rail, and dividing a plurality of evaluation regions in the head part of the sample; observing the sample under a metallographic microscope, for each evaluation region, counting the total length of the martensite structure in the evaluation region, and calculating the ratio of the total length to the total length of the contour of the evaluation region to obtain the length proportion of the martensite structure in the evaluation region; and / or measuring the thickness of the martensite structure in the evaluation region and calculating the average value to obtain the average thickness of the martensite structure in the evaluation region; and drawing a distribution characteristic map or performing quantitative comparison according to the length proportion of the martensite structure in each evaluation region and / or the average thickness. The application can significantly improve the scientificity and accuracy of rail maintenance, and effectively guarantee the safety and economy of railway operation.

Description

Technical Field

[0001] This invention relates to the field of rail maintenance technology, and in particular to a method for quantitatively evaluating the martensitic structure of the rail surface after grinding. Background Technology

[0002] Rail grinding is a key technology in modern railway maintenance for eliminating and mitigating surface damage to rails. Its main goal is to remove wear and damage, repair the rail profile, improve contact performance, enhance wheel-rail relationships, and extend rail service life. However, traditional rail grinding methods, such as large-machine grinding, small-machine grinding, and high-speed grinding (except for rail milling), remove wear and damage through friction between a high-speed rotating grinding stone and the rail surface. This process generates localized high temperatures, which can induce changes in the material's microstructure, forming a hard and brittle white layer—a thin layer of martensite. This white layer is typically formed by the rapid cooling of the rail material under high temperatures, primarily consisting of high-carbon martensite (twinned martensite), which is highly hard and brittle. During subsequent service, the mismatch in mechanical properties between the white layer and the matrix often leads to significant plastic deformation zones beneath it, making it prone to microcracks. These microcracks gradually expand under stress, which may eventually lead to spalling damage on the rail surface.

[0003] A study by Delft University in the Netherlands suggests that the formation of martensitic structure on the rail surface should be avoided during rail grinding, especially for harder heat-treated rails. A joint study by the University of Sheffield in the UK and the National University of Columbia investigated the thickness of a thin layer of martensitic structure on the rail surface of three different grades (R260, R350HT, and R400HT) after the same grinding process.

[0004] Existing technologies also lack systematic research and quantitative evaluation methods for the surface white martensite structure generated on the rail surface after grinding. Due to the inability to quantify the influence of the white martensite structure, there is a lack of targeted data support when selecting and adjusting grinding methods and process parameters (such as grinding pressure, speed, and particle size).

[0005] In view of this, based on years of experience in production and design in this and related fields, the inventor has developed a quantitative evaluation method for the martensitic structure of the rail surface after grinding through repeated experiments, in order to solve the problems existing in the prior art. Summary of the Invention

[0006] The purpose of this invention is to provide a quantitative evaluation method for the martensitic structure of rail surface after grinding, which can determine the degree of martensitic structure produced under different grinding equipment and grinding processes, and provide a scientific basis for selecting grinding equipment and grinding processes.

[0007] To achieve the above objectives, this invention proposes a quantitative evaluation method for the martensitic structure of the rail surface after grinding, wherein the quantitative evaluation method includes:

[0008] Select a section of polished rail, cut a sample of a predetermined length along the longitudinal direction of the rail, and divide the rail head portion of the sample into multiple evaluation areas.

[0009] The sample is observed under a metallographic microscope. For each evaluation region, the total length of the martensite structure within the evaluation region is counted, and the ratio of the total length to the total outline length of the evaluation region is calculated to obtain the length ratio of the martensite structure in the evaluation region; and / or, the thickness of the martensite structure within the evaluation region is measured and the average value is calculated to obtain the average thickness of the martensite structure in the evaluation region.

[0010] Based on the length proportion and / or average thickness of the martensitic structure in each of the evaluation regions, a distribution feature map is drawn or a quantitative comparison is performed.

[0011] Compared with the prior art, the present invention has the following features and advantages:

[0012] The quantitative evaluation method for the martensitic structure of the rail surface after grinding proposed in this invention constructs a regional division system based on the rail grinding profile acceptance standard and simultaneously conducts multi-dimensional metallographic observations. This achieves accurate quantitative characterization of the thin-layer martensitic structure of the rail surface in each evaluation area. The generated distribution characteristic data and quantitative comparisons can intuitively and systematically reflect the distribution pattern and severity of martensitic structure in the key contact area of ​​the rail head. This allows the evaluation results to be closely linked with the rail grinding quality acceptance system. It can be directly used for objective comparison of the efficiency of different grinding equipment, scientific optimization of grinding process parameters, accurate determination of the suitability of rail materials, and forward-looking assessment of service status evolution. This provides comprehensive, reliable, and quantifiable data support for the quality control and process decision-making of rail grinding operations, significantly improving the scientificity and accuracy of rail maintenance and effectively ensuring the safety and economy of railway operation. Attached Figure Description

[0013] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. Those skilled in the art, guided by the teachings of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances.

[0014] Figure 1 This is a schematic diagram of the quantitative evaluation area in the quantitative evaluation method of the present invention;

[0015] Figure 2 This refers to the specific quantitative analysis location in the quantitative evaluation method of the present invention;

[0016] Figure 3 This is a schematic diagram of the quantitative evaluation method of the present invention.

[0017] Explanation of reference numerals in the attached figures

[0018] 100. Specimen; 20. Evaluation area; 110. Cross section; 120. Longitudinal section Detailed Implementation

[0019] The details of the present invention can be more clearly understood by referring to the accompanying drawings and the description of specific embodiments. However, the specific embodiments of the present invention described herein are for illustrative purposes only and should not be construed as limiting the invention in any way. Under the teachings of this invention, those skilled in the art can conceive of any possible modifications based on the invention, and these should all be considered to fall within the scope of the invention.

[0020] like Figures 1 to 3 As shown, this invention proposes a quantitative evaluation method for the martensitic structure of the rail surface after grinding, wherein the quantitative evaluation method includes:

[0021] Select a section of polished rail, cut a sample 100 of a predetermined length along the longitudinal direction of the rail, and divide the rail head portion of the sample 100 into multiple evaluation areas 20.

[0022] Under a metallographic microscope, the sample 100 is observed. For each evaluation region 20, the total length of the martensite structure within the evaluation region 20 is counted, and the ratio of the total length to the total outline length of the evaluation region 20 is calculated to obtain the length ratio of the martensite structure in the evaluation region 20; and / or, the thickness of the martensite structure within the evaluation region 20 is measured and the average value is calculated to obtain the average thickness of the martensite structure within the evaluation region 20.

[0023] Based on the length proportion and / or average thickness of the martensitic structure in each evaluation region 20, a distribution characteristic map is drawn or a quantitative comparison is performed.

[0024] The quantitative evaluation method for the martensitic structure of the rail surface after grinding proposed in this invention divides the rail head after grinding into multiple evaluation regions 20, and observes it with a metallographic microscope to statistically analyze the length ratio and average thickness of the martensitic structure in each evaluation region 20. This enables a systematic quantification of the spatial distribution and morphological characteristics of the martensitic structure on the rail surface. By integrating the two parameters of length and thickness, this quantitative evaluation method forms a comparable distribution feature map or quantitative data, thereby providing a unified and reliable evaluation basis for objectively comparing the merits of different grinding processes, equipment, and rail materials.

[0025] In one optional embodiment of the present invention, the polished rail is either a polished rail that has not yet been put into service or a polished rail that has already been put into service.

[0026] Specifically, this quantitative evaluation method uses a wide range of rail samples, applicable to two states: first, rails that have just undergone grinding and have not yet been put into use on the track; and second, rails that have been ground and have been in service on the track for a period of time before being taken off the track for various reasons. For newly ground rails, the evaluation results directly reflect the immediate impact of specific grinding processes and equipment on the rail surface microstructure. For ground rails already in service, the evaluation results reflect the state and distribution characteristics of martensite microstructure under subsequent wheel-rail loads, helping to trace the long-term effects of the grinding process. This selection of these two types of samples allows this quantitative evaluation method to be used for both immediate optimization of the grinding process and for condition assessment and maintenance decisions during rail service.

[0027] In an optional embodiment of the present invention, the sample 100 is inlaid, ground, polished and etched before being observed under a metallographic microscope.

[0028] Specifically, when mounting the cut sample 100, either cold mounting or hot mounting can be used to protect the edge structure of the sample 100 from damage during subsequent processing. Then, the mounted sample 100 is polished with sandpaper to remove cutting marks and surface impurities. Next, the polished sample 100 is finely polished with a polishing machine until the surface of the sample 100 is smooth and free of scratches. Finally, a 2%~10% nitric acid alcohol solution is used as the etching solution, and the polished sample 100 is immersed in the etching solution for 5~10 seconds. After the treatment is completed, the sample 100 can be placed under a metallographic microscope for observation.

[0029] Through a series of processes including inlaying, grinding, polishing, and etching, the integrity of the edge structure of sample 100 can be effectively protected, and the surface of sample 100 can meet the flatness requirements for metallographic observation. At the same time, it allows the martensite structure to form a clear contrast with the matrix structure, which facilitates the accurate identification and statistical analysis of the martensite structure under a metallographic microscope. This provides a reliable sample basis for the quantitative calculation of the martensite length ratio and average thickness, ensuring the accuracy of the quantitative evaluation results.

[0030] In an optional embodiment of the present invention, the quantitative evaluation method further includes:

[0031] When observing sample 100 under a metallographic microscope, the maximum thickness of the martensitic structure in each field of view is recorded. Then, the average value of multiple maximum thicknesses in each evaluation area is calculated to obtain the average value of the maximum thickness.

[0032] In an optional embodiment of the present invention, a plurality of evaluation regions 20 are divided in the railhead portion of the sample 100, including:

[0033] According to the rail grinding profile acceptance standard, along the direction from the working edge to the non-working edge of the rail head, the cross section 110 of the sample 100 is divided into N continuous evaluation areas 20, where N≥7; the above steps are mapped to the longitudinal section 120 of the sample 100, and the longitudinal section 120 of the sample 100 is divided into N continuous evaluation areas 20.

[0034] Specifically, based on the GQI index used for rail profile in the rail grinding profile acceptance standard TJGW170-2021, the rail head is divided into 4 regions according to the horizontal axis. These 4 regions are then divided into 7 evaluation regions 20 with a scale value of 10mm each. They are numbered sequentially from the working side to the non-working side of the rail head as 1# to 7#, where 1# is located on the working side and 7# is located on the non-working side. A 15mm length is cut along the longitudinal direction of the rail as a sample 100. The above cross-sectional division method is mapped onto the longitudinal section 120 of the sample 100, and the longitudinal section 120 is divided into 7 consecutive evaluation regions 20, which are marked as L1 to L7 respectively. The length of each evaluation region 20 in the longitudinal section 120 is constant at 15mm.

[0035] It should be noted that, in this application, the longitudinal section refers to the surface along the length of the rail, and the cross section refers to the profile section of the rail.

[0036] In this embodiment, by dividing the evaluation area 20 according to the rail grinding profile acceptance standard, and setting no less than 7 continuous evaluation areas 20 in both the cross section 110 and the longitudinal section 120, it is possible to fully cover the rail head wheel-rail contact area and non-contact area, accurately capture the distribution of martensite structure in different positions of the rail, and provide a regular and unified evaluation benchmark for the subsequent quantitative calculation of martensite length ratio and average thickness.

[0037] In one alternative embodiment of this implementation, the total profile length of each evaluation region 20 on the cross-section 110 is:

[0038]

[0039] In the formula, T is the total length of the evaluation area in mm, n is the central angle of the corresponding rail head arc in °, and R is the radius of the rail head in mm.

[0040] By employing a calculation formula based on the geometric parameters of the rail head arc, the contour length of each evaluation area 20 can be accurately quantified, avoiding errors that may arise from manual measurement and significantly improving data accuracy. Furthermore, the formula involves only two parameters: the rail head radius R and the central angle n, making the calculation process simple and efficient, suitable for rapid analysis of rails of different specifications. In addition, the standardized calculation method based on geometric relationships ensures the repeatability of the evaluation results, providing an objective and reliable quantitative basis for rail grinding quality assessment, thereby effectively supporting the prediction of rail service performance and the formulation of maintenance decisions.

[0041] In an optional example, the proportion of martensite in the evaluation region 20 along cross section 110 is:

[0042] P Tj = (i = 1,2,…,n; j=1,2,…,7)

[0043] In the formula, j represents the j-th evaluation region, P Tj For length percentage, l ij Tj represents the total length of the profile of the evaluation region, where Tj is the length of each martensitic structure seen in each window under the microscope within the evaluation region.

[0044] Specifically, the cross-section of sample 100 was observed under a metallographic microscope at 200x magnification. For each evaluation region 20, the length of the martensite structure observed in each window within the evaluation region 20 was counted and summed. The total length of the martensite structure in each evaluation region 20 was divided by the total outline length Tj of the corresponding evaluation region 20 to calculate the length proportion P of the martensite structure in that evaluation region 20. Tj By calculating the length ratio of 20 martensite in each evaluation region on the cross-section, the distribution ratio of martensite in each region along the rail head can be obtained, forming a quantitative characteristic of the transverse distribution of thin-layer martensite on the rail surface.

[0045] In one alternative embodiment of this implementation, the total length of the profile of each evaluation region on the longitudinal section 120 is a predetermined length.

[0046] Since the longitudinal section 120 has a straight profile along the longitudinal direction of the rail, and the sample 100 has been cut to a predetermined length during the sampling process, the total length of the profile in each evaluation area 20 divided by the longitudinal section 120 is consistent with the predetermined length. This length value serves as the benchmark denominator parameter for calculating the proportion of martensite length on the longitudinal section 120. There is no need to measure or perform complex calculations on the profile of each area separately, which simplifies the quantitative evaluation process and effectively improves the efficiency and accuracy of characterizing the longitudinal distribution characteristics of martensite in the rail. At the same time, it enhances the consistency of the quantitative data of the cross section 110 and the longitudinal section 120 in terms of calculation logic and result comparison.

[0047] In an optional example, on longitudinal section 120, the length percentage of martensite in the evaluation region is:

[0048] P Lj = (i = 1,2,…,n; j=1,2,…,7)

[0049] In the formula, j represents the j-th evaluation region, P Lj For length percentage, i Lj To evaluate the length of each martensitic structure seen in each window under the microscope within the region, L is a predetermined length.

[0050] In practice, the j-th evaluation region 20 is determined according to the 120-region division scheme of the longitudinal section. The region is then observed under a metallographic microscope, moving along its contour. The length value i of the martensite structure observed in each window is recorded. ij The total length of martensite within the evaluation region 20 is obtained by summing the values, and then divided by the predetermined length L of the region to obtain the proportion P of martensite length in the evaluation region 20. Lj This calculation process can be performed independently for each evaluation region 20, forming a systematic quantitative dataset. This calculation method enables the distribution characteristics of martensite in each evaluation region 20 on the longitudinal section 120 to be accurately characterized by standardized quantitative parameters. The generated length proportion data intuitively reflects the distribution density of martensite at different positions in the longitudinal direction of the rail, providing an accurate and reliable data basis for analyzing the extension law of martensite along the longitudinal direction of the rail. At the same time, it complements the quantitative index of the cross section 110, jointly constructing a complete evaluation system for the two-dimensional spatial distribution of martensite on the rail surface.

[0051] In an optional embodiment of the present invention, drawing a distribution feature map includes:

[0052] The length proportion and / or average thickness of each evaluation region 20 are plotted in a graph with the evaluation region number as the x-axis and the length proportion and / or average thickness as the y-axis to characterize the distribution characteristics of martensite structure along the transverse direction of the guide head.

[0053] Specifically, the evaluation area 20 is numbered by dividing the rail head into multiple continuous evaluation areas 20 based on the transverse geometric characteristics of the rail head, and each evaluation area 20 is uniquely assigned a number. Then, through microscopic observation and image analysis techniques, the length percentage and / or average thickness data of the martensitic structure within each evaluation area 20 are obtained. The resulting chart uses the evaluation area 20 number as the x-axis and the corresponding length percentage and / or average thickness as the y-axis, generating a two-dimensional coordinate chart using data visualization tools (such as Excel, Origin, etc.). By connecting the data points or using a bar chart, the distribution characteristics of the martensitic structure along the transverse direction of the rail head are visually presented. By transforming the quantitative data into a visual chart, the intuitiveness and interpretability of the martensitic structure distribution characteristics are significantly improved.

[0054] In an optional embodiment of the present invention, quantitative comparison includes at least one of the following methods:

[0055] Method 1: Compare the length ratio and / or average thickness of martensite structure between different evaluation areas 20 of the same type of rail under the same grinding equipment and mode;

[0056] Method 2: Compare the length proportion and / or average thickness of martensitic structure in each evaluation area 20 for different types of rails under the same grinding equipment and mode;

[0057] Method 3. Compare the length proportion and / or average thickness of martensite in each evaluation area of ​​the same type of rail under the same grinding equipment and different grinding modes;

[0058] Method 4: Compare the length ratio and / or average thickness of martensitic structure in each evaluation area 20 under different grinding equipment for the same type of rail.

[0059] Through the above-mentioned multiple optional quantitative comparison methods, this quantitative evaluation method constructs a flexible and systematic analytical framework, which can conduct in-depth and targeted comparative studies on the formation characteristics of martensitic structure after grinding from multiple key dimensions such as regional distribution, rail material, process parameters and equipment type.

[0060] Specifically, Method 1, by fixing the type of rail, grinding equipment and grinding mode, and comparing the length ratio or average thickness data of different evaluation areas 20 of the rail head under this condition, can analyze the uneven distribution of martensite on the rail surface in the transverse direction.

[0061] Method 2: By using fixed grinding equipment and grinding mode, compare the length ratio or average thickness of the corresponding evaluation area 20 of different types of rails under the same process to evaluate the differences in the ability of different rail materials to resist the formation of grinding martensite.

[0062] Method 3: By fixing the type of rail and the grinding equipment, compare the length ratio or average thickness of each evaluation area 20 under different grinding modes (such as different pressure and speed parameters) to evaluate the influence of grinding process parameters on the formation of martensite structure.

[0063] Method 4: By fixing the type of rail, compare the length ratio or average thickness of each evaluation area 20 under different grinding equipment (such as large grinding machine and small grinding machine) to assess the differences in the impact of different grinding equipment on the rail surface structure.

[0064] Example

[0065] The following is a detailed description of the specific implementation process of the quantitative evaluation method for the martensitic structure of the rail surface after grinding, as proposed in this invention, with reference to an embodiment.

[0066] Step 1: Sampling

[0067] Select a section of ground rail, either freshly ground or already ground and in service. According to the TJGW170-2021 rail grinding acceptance standard, the rail profile is accepted using the GQI (Grinding Quality Index) method. The GQI calculation divides the rail head into four regions along the horizontal axis. Following the rail grinding profile acceptance standard, these four regions are further subdivided into seven evaluation areas (20) with 10mm increments. Cut a 15mm section longitudinally along the rail, 10mm deep from the highest point of the rail top surface. Number the working side section #1, and sequentially number the sections up to #7 on the non-working side. The outermost eighth section on the non-working side is rarely considered in rail grinding and is therefore not included in the evaluation.

[0068] Step 2: Metallographic sample preparation:

[0069] The rail sample is inlaid (either cold or hot inlay is acceptable) to protect the edge structure, and then polished with sandpaper and a polishing machine. It is then etched with 2%–10% nitric acid alcohol for 5–10 seconds to prepare a metallographic specimen.

[0070] Step 3: Quantitative Calculation Method

[0071] The morphology and distribution characteristics of the white layer on the rail surface were observed in the rail cross-section. The length of the white layer was counted under 200x magnification using a metallographic microscope and divided by the total length of the corresponding evaluation area 20. This yielded the ratio of the white layer structure in different regions of cross-section 110 and longitudinal section 120 to the total length of the evaluation area 20. The maximum thickness of the white martensite structure was recorded within the field of view where it was observed under a metallographic microscope. The sum of the maximum thicknesses recorded in multiple fields of view where white martensite was found, divided by the number of fields of view containing white martensite, yielded the average thickness of the white martensite structure.

[0072] like Figure 1 As shown, Region I to Region IV are the four main regions for evaluating the grinding profile, and are also the areas that are basically covered by rail grinding. They are further subdivided into 7 smaller evaluation regions 20 as quantitative evaluation regions for the white martensite structure of rail grinding 20.

[0073] like Figure 2 As shown, the specific quantitative analysis locations of different evaluation regions 20 labeled T1 to T7 within cross section 110, and the quantitative analysis locations of different evaluation regions 20 labeled L1 to L7 within longitudinal section 120 are also shown.

[0074] The calculation method for the transverse length of each evaluation area (labeled T1-T7) of the new steel rail is as follows:

[0075] (2-1)

[0076] In the formula: T represents the length of each region (T1-T7, in mm), n represents the central angle of different arcs of the rail head (in °), R represents the radius (in mm), and the length of the transverse region (T1-T7) is as follows. Figure 2 As shown.

[0077] Calculation of the length of each evaluation area (20 mm) in the transverse direction after the old rail grinding experiment: Measure the actual rail profile using a rail profiler, and import the transverse and longitudinal coordinates of the profile into CAD, such as... Figure 1 and Figure 2 The evaluation area 20 is divided as shown, and the arc length of each evaluation area 20 is measured as the area length of T1~T7.

[0078] The longitudinal length of the rail is constant at 15mm for each evaluation area (L1-L7), such as... Figure 2 As shown.

[0079] Coverage percentage of each evaluation region:

[0080] Cross section: P Tj = (i = 1,2,…,n; j=1,2,…,7)

[0081] Longitudinal section: P Lj = (i = 1,2,…,n; j=1,2,…,7)

[0082] Among them, P Tj This indicates the proportion of the length of the white martensite structure in the cross-section regions 1# to 7# in each evaluation region 20. Tj represents the length of each white martensite structure seen in each window under the microscope within each evaluation region. Tj represents the outline length of the different evaluation regions numbered 1# to 7#, where j = 1, 2, 3, 4, 5, 6, 7.

[0083] Among them, P Lj This indicates the percentage of the length of the white martensite structure in each evaluation region (numbered 1# to 7#) within a longitudinal section of 120 mm. This represents the length of each white martensite structure seen within each window of the microscope in each evaluation region 20, where j = 1, 2, 3, 4, 5, 6, 7.

[0084] Step 4: Track surface white layer tissue distribution characteristics map

[0085] By plotting line graphs or bar charts showing the proportion of thin martensite on the rail surface in different evaluation regions 20 of cross-section 110, the coverage percentage of the quantified white layer structure in each evaluation region 20 (numbered T1~T7 and L1~L7) and the maximum average thickness of the white layer structure in each evaluation region 20 can be obtained. This yields a trend diagram of the overall distribution characteristics of the white layer martensite structure in different regions.

[0086] Step 5: Quantitative comparison of the martensitic structure of the white layer on the track surface

[0087] (1) By comparing the same grinding equipment, the same grinding mode, and the same type of rail, the quantitative differences in the white martensite structure between different areas of the rail can be compared.

[0088] (2) Using the same grinding equipment and the same grinding mode, different types of rails can be compared to compare the quantitative differences in the white martensite structure between different rails.

[0089] (3) By comparing different grinding modes with the same grinding equipment and the same type of rail, the quantitative differences in the white martensite structure between different grinding processes can be compared.

[0090] (4) Different grinding equipment, for the same type of rail, can be used to compare the quantitative differences in the white martensite structure between different grinding equipment.

[0091] By quantifying the white martensite structure, we can explore the types of rails that produce less martensite during the grinding process, as well as the grinding techniques and equipment.

[0092] The detailed explanations of the above embodiments are intended only to explain the present invention so as to facilitate a better understanding of the present invention. However, these descriptions should not be construed as limiting the present invention for any reason. In particular, the various features described in different embodiments can be arbitrarily combined with each other to form other embodiments. Unless there is an explicit description to the contrary, these features should be understood to be applicable to any embodiment, and not limited to the described embodiments.

Claims

1. A method for quantitatively evaluating the martensitic structure of a steel rail surface after grinding, characterized in that, The quantitative evaluation method includes: Select a section of polished rail, cut a sample of a predetermined length along the longitudinal direction of the rail, and divide the rail head portion of the sample into multiple evaluation areas. The sample is observed under a metallographic microscope. For each evaluation region, the total length of the martensite structure within the evaluation region is counted, and the ratio of the total length to the total outline length of the evaluation region is calculated to obtain the length ratio of the martensite structure in the evaluation region; and / or, the thickness of the martensite structure within the evaluation region is measured and the average value is calculated to obtain the average thickness of the martensite structure in the evaluation region. Based on the length proportion and / or average thickness of the martensitic structure in each of the evaluation regions, a distribution feature map is drawn or a quantitative comparison is performed.

2. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 1, is characterized in that... The polished rails are either rails that have not yet been put into service or rails that have already been put into service.

3. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 1, is characterized in that... Before observing the sample under a metallographic microscope, the sample is inlaid, ground, polished and etched.

4. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 1, is characterized in that... The quantitative evaluation method also includes: When observing the sample under a metallographic microscope, the maximum thickness of the martensitic structure in each field of view is recorded, and then the average value of multiple maximum thicknesses in each evaluation area is calculated.

5. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 1, is characterized in that... The railhead portion of the specimen is divided into multiple evaluation areas, including: According to the rail grinding profile acceptance standard, the cross section of the sample is divided into N consecutive evaluation areas along the direction from the working edge to the non-working edge of the rail head, where N≥7; the above division process is mapped to the longitudinal section of the sample, and the longitudinal section of the sample is divided into N consecutive evaluation areas.

6. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 5, is characterized in that... On the cross-section, the total length of the contour of each evaluation region is: In the formula, T is the total length of the evaluation area, in mm, n is the central angle of the corresponding rail head arc, in °, and R is the radius of the rail head, in mm.

7. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 6, is characterized in that... On the cross-section, the length percentage of martensitic structure in the evaluation region is: PTj = (i = 1,2,……,n; j=1,2,……,7) In the formula, j represents the j-th evaluation region, P Tj For length percentage, i ij Tj is the total length of the evaluation region, representing the length of each martensitic structure seen in each window under the microscope within the evaluation region.

8. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 5, is characterized in that... On the longitudinal section, the total length of the outline of each of the evaluation regions is the predetermined length.

9. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 8, is characterized in that... On the longitudinal section, the length percentage of martensitic structure in the evaluation region is: P Lj = (i = 1,2,……,n; j=1,2,……,7) In the formula, j represents the j-th evaluation region, P Lj For length percentage, i Lj L is a predetermined length used to evaluate the length of each martensitic structure seen in each window under a microscope within the region.

10. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 1, is characterized in that... Drawing distribution feature maps includes: The length proportion and / or average thickness of each evaluation region are plotted in a graph with the evaluation region number as the horizontal axis and the length proportion and / or average thickness as the vertical axis to characterize the distribution characteristics of martensite structure along the transverse direction of the rail head.

11. The method for quantitatively evaluating the martensitic structure of the rail surface after grinding, as described in claim 1, is characterized in that... Quantitative comparisons can be conducted in at least one of the following ways: Method 1: Compare the length ratio and / or the average thickness of the martensitic structure between different evaluation areas of the same type of rail under the same grinding equipment and mode; Method 2: Compare the length ratio and / or average thickness of the martensitic structure of each evaluation area for different types of rails under the same grinding equipment and mode; Method 3. Compare the length ratio and / or average thickness of the martensitic structure of each evaluation area of ​​the same type of rail under the same grinding equipment and different grinding modes; Method 4: Compare the length ratio and / or average thickness of the martensitic structure of each evaluation area under different grinding equipment for the same type of rail.

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