Method for evaluating process weldability of steel rail

Abstract

The invention provides a method for evaluating steel rail process weldability, and belongs to the technical field of railway engineering. The method for evaluating the process weldability of the steel rail comprises the following steps: sampling and selecting the steel rail to be welded, preparing the steel rail to be welded into a detection sample, selecting a plurality of detection points on the detection sample, performing ultrasonic detection on each detection point, collecting corresponding ultrasonic detection echo data, and evaluating the process weldability of the steel rail to be welded according to the ultrasonic detection echo data. According to the method for evaluating the process weldability of the steel rail, the to-be-welded steel rail selected by sampling is subjected to accurate process weldability evaluation through an ultrasonic detection technology, and the influence of the microstructure and defect in the steel rail on welding can be evaluated before welding, so that the quality and reliability of a welding joint are improved, resource allocation is optimized, and the welding quality is improved. The production efficiency is improved, material waste and extra cost caused by unqualified welding are reduced, powerful decision support is provided for steel rail welding construction enterprises, and the welding quality and economic benefits of railway engineering are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of railway engineering, and in particular to a method for evaluating the process weldability of a rail. Background Art

[0002] Welding rails refers to the butt welding of rails, which is the basic work for laying seamless railway lines. At present, the flash butt welding method is mainly used to weld rails. The flash welding joints of rails account for more than 80% of the total number of rail joints in seamless lines, including fixed flash welding carried out at the welding rail base and mobile flash welding carried out on the railway track.

[0003] Ensuring the reliability of rail welding quality is the focus and difficulty of rail welding construction companies. Before formal welding, the welded rails must undergo welding type tests to determine the welding process parameters used for formal welding and ensure that the welding quality is qualified. After welding is completed, the rail weld joints need to be visually inspected, ultrasonically tested or magnetically tested to determine whether the welding quality is qualified. Unqualified rail weld joints must be cut off and re-welded, and are not allowed to be laid on the road.

[0004] However, during the welding production using the welding process parameters determined by the welding type test, the defective rate of the welded joints will still suddenly increase, and this situation generally occurs in a certain batch of rails. Moreover, when the same welding process is used to weld the next batch of rails, the defective rate of the welded joints returns to a normal value of less than 2%. This phenomenon shows that different batches of rails of the same model and brand produced by the same steel plant have different process weldability, which leads to different batches of rails being easy to weld for some batches and difficult to weld for others (high defective rate).

[0005] The sudden increase in the defective rate of welded joints mentioned above will lead to frequent re-welding of sawn joints. Rail welding construction companies can only passively accept this situation, repeatedly sawing and re-welding, achieving qualified welding quality at a high cost and very low production efficiency until the welding of the batch of rails is completed. This seriously reduces welding production efficiency, interferes with railway construction plans and increases construction costs.

[0006] In view of this, the inventor has designed a method for evaluating the process weldability of rails based on many years of experience in production design in this field and related fields and through repeated experiments, in order to solve the problems existing in the prior art. Summary of the invention

[0007] The object of the present invention is to provide a method for evaluating the process weldability of a rail, which can pre-evaluate the welding difficulty of a rail to be welded.

[0008] To achieve the above-mentioned object of the invention, the present invention proposes a method for evaluating the process weldability of rails, wherein rails to be welded are sampled and prepared as test specimens, multiple measuring points are selected on the test specimens, ultrasonic testing is performed on each measuring point and corresponding ultrasonic testing echo data is collected, and the process weldability of the rails to be welded is evaluated based on the ultrasonic testing echo data.

[0009] Compared with the prior art, the present invention has the following characteristics and advantages:

[0010] The method for evaluating the process weldability of rails proposed in the present invention uses ultrasonic testing technology to accurately evaluate the process weldability of rails before welding, thereby predicting the difficulty of welding a batch of rails, significantly improving the predictability and planning of welding production, and enabling construction companies to optimize welding process parameters based on evaluation results, take preventive measures in advance, and avoid production interruptions and delays caused by welding quality problems. The method for evaluating the process weldability of rails proposed in the present invention not only improves welding quality, but also helps reduce risks in the welding process and ensures the smooth progress of railway construction.

[0011] The method for evaluating the process weldability of rails proposed in the present invention can significantly reduce the defective rate of welded joints by analyzing the ultrasonic detection echo data, and reduce the material waste and additional costs caused by sawing and re-welding of unqualified joints. Through the method for evaluating the process weldability of rails proposed in the present invention, the process weldability of rails can be evaluated before welding, the production plan can be reasonably arranged, and rework during the welding process can be reduced, thereby greatly improving the welding production efficiency. This cost-effectiveness optimization not only reduces the economic burden of the enterprise, but also improves the overall efficiency of the welding operation, which can bring significant economic benefits to the enterprise.

[0012] The method for evaluating the process weldability of rails proposed in the present invention can accurately predict the difficulty of rail welding, so as to screen out rails that may be difficult to weld before actual welding, and then can specifically adjust the welding process, optimize welding parameters, and avoid factors that may cause welding quality problems in advance, which not only improves the quality of welded joints, but also enhances the reliability of welded structures, reduces subsequent maintenance costs and risks, and is of great significance for ensuring railway transportation safety and extending the service life of rails. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings described herein are only for explanation purposes and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the various components in the figures are only schematic, used to help understand the present invention, and are not specifically limited to the shapes and proportional dimensions of the various components of the present invention. Those skilled in the art can select various possible shapes and proportional dimensions to implement the present invention according to the teachings of the present invention.

[0014] Figure 1 It is a schematic diagram of the rail cross-section sampling diagram of the present invention;

[0015] Figure 2 It is a schematic diagram of a rail sample of the present invention;

[0016] Figure 3 Schematic diagram of an example of an algorithm for calculating equivalent amplitude of the present invention;

[0017] Figure 4 It is a schematic diagram of a rail head inspection specimen of the present invention;

[0018] Figure 5 It is a schematic diagram of a rail bottom detection sample of the present invention;

[0019] Figure 6 The figure is a schematic flow chart of the method for evaluating the process weldability of rails according to the present invention.

[0020] Description of the accompanying drawings:

[0021] 10. Rail head; 20. Rail bottom; 30. Rail head test specimen;

[0022] 40. Rail bottom inspection sample; 50. Measuring point. DETAILED DESCRIPTION

[0023] The details of the present invention can be more clearly understood with reference to the accompanying drawings and the description of the specific embodiments of the present invention. However, the specific embodiments of the present invention described herein are only used for the purpose of explaining the present invention and cannot be understood as limiting the present invention in any way. Under the guidance of the present invention, technicians can conceive of any possible variations based on the present invention, which should all be considered to belong to the scope of the present invention.

[0024] The present invention proposes a method for evaluating the process weldability of rails. Rails to be welded are sampled and prepared as test specimens. A plurality of measuring points 50 are selected on the test specimens. Ultrasonic testing is performed on each measuring point 50 and corresponding ultrasonic testing echo data is collected. The process weldability of the rails to be welded is evaluated based on the ultrasonic testing echo data.

[0025] The method for evaluating the process weldability of rails proposed in the present invention uses ultrasonic testing technology to accurately evaluate the process weldability of sampled rails to be welded, and can evaluate the influence of the internal microstructure and defects of the rails on welding before welding, thereby improving the quality and reliability of welded joints, optimizing resource allocation, improving production efficiency, and reducing material waste and additional costs caused by unqualified welding. It provides strong decision-making support for rail welding construction companies and significantly improves the welding quality and economic benefits of railway projects.

[0026] In an optional embodiment of the present invention, the process weldability of the to-be-welded rail is evaluated based on the ultrasonic detection echo data, including: calculating the equivalent amplitude of each measuring point 50 based on the ultrasonic detection echo data of each measuring point 50; calculating the average value of the equivalent amplitudes of multiple measuring points 50 based on the equivalent amplitude of each measuring point 50; setting a threshold value, and evaluating the process weldability of the to-be-welded rail based on the difference between the average value of the equivalent amplitude and the threshold value.

[0027] The method for evaluating the process weldability of a to-be-welded rail based on ultrasonic testing echo data of the present invention has an optional implementation process as follows:

[0028] (1) Sample rails, process test specimens according to the preset processing plan, and apply a universal ultrasonic testing coupling agent on the surface of the test specimens;

[0029] (2) Using a general digital ultrasonic flaw detector, setting an appropriate ultrasonic detection sensitivity, placing an ultrasonic detection probe at a test position (measurement point 50) on the surface of the processed test sample, and collecting the ultrasonic detection echo of the measurement point 50;

[0030] (3) Select the ultrasonic detection echo within a certain sound path range and calculate the equivalent amplitude of the measuring point 50;

[0031] (4) According to the above step (3), n measuring points 50 are randomly selected on the test surface, and generally 10 to 20 measuring points 50 are selected for each sample (i.e., n=10 to 20), and the equivalent amplitude of each measuring point 50 is tested and calculated, and the average value of the equivalent amplitudes of the n measuring points 50 is calculated;

[0032] (5) A threshold value of α = 10% is proposed, and the difference between the average value of 50 equivalent amplitudes at n measuring points and the threshold value is used to evaluate the process weldability of the rail:

[0033] (6) When the average value of the equivalent amplitude of the test sample is less than the threshold value, the defective rate of the rail welded joint can be maintained at a normal level (less than 2%); the smaller the average value is than the threshold value, the better the process weldability of the rail is, which is manifested as easier welding; when the average value of the equivalent amplitude of the test sample is greater than the threshold value, the defective rate of the rail welded joint increases, and the larger the average value is than the threshold value, the worse the process weldability of the rail is, which is manifested as a higher defective rate of the rail welded joint and a greater welding difficulty.

[0034] In the present invention, the basic parameters of the ultrasonic flaw detector and the probe, and the sensitivity of ultrasonic detection can be changed. An optional method for setting an appropriate ultrasonic detection sensitivity is:

[0035] (1) Basic parameters of ultrasonic flaw detector and probe:

[0036] Ultrasonic flaw detector: general digital ultrasonic flaw detector, the instrument horizontal distance measurement is set to shear wave sound path 100mm;

[0037] Ultrasonic detection probe: frequency 5MHz, chip size 13mm×13mm, K2.5 (refraction angle 68.2°);

[0038] Calibration test block: GHT-4 test block.

[0039] (2) Setting the ultrasonic detection sensitivity:

[0040] Connect the ultrasonic flaw detector and ultrasonic detection probe, adjust the instrument gain or attenuator, make the maximum echo of the corner on the 2#Φ4mm vertical hole of the GHT-4 test block is 80% of the full screen, and then increase the gain △dB (generally 15dB) as the ultrasonic detection sensitivity.

[0041] In particular, the number of measurement points 50 selected on the test specimen may vary.

[0042] The method for evaluating the process weldability of a steel rail to be welded of the present invention is as follows: Figure 6 As shown, by pre-evaluating the welding performance of the welded rail, the construction enterprise can adjust the welding parameters in time to avoid the production of defective products, thereby reducing costs and improving production efficiency. In addition, the present invention provides a scientific and objective evaluation standard for the method of evaluating the process weldability of the welded rail, making the control of welding quality more accurate, reducing the interference of human factors, and enhancing the adaptability and flexibility of the welding process.

[0043] In an optional example of this embodiment, the smaller the average value of the equivalent amplitude is than the threshold value, the better the process weldability of the steel rail to be welded; the larger the average value of the equivalent amplitude is than the threshold value, the worse the process weldability of the steel rail to be welded. The process weldability of the rail is quantitatively evaluated by ultrasonic detection echo data. First, the sampled steel rail to be welded is subjected to ultrasonic detection to obtain ultrasonic detection echo data of each measuring point 50. Based on the ultrasonic detection echo data, the equivalent amplitude of each measuring point 50 is calculated to obtain the average value of the equivalent amplitude of all measuring points 50. The average value of the equivalent amplitude is compared with the preset threshold value to evaluate the process weldability of the rail. Specifically, if the calculated average value of the equivalent amplitude is lower than the threshold value, it indicates that the internal structure of the steel rail to be welded is relatively uniform, and the risk of defects during welding is low, so the process weldability is good. On the contrary, if the average value of the equivalent amplitude is higher than the threshold value, it means that there may be more unevenness inside the rail, and quality problems are more likely to occur during welding, so the process weldability is poor. This evaluation method provides an intuitive and quantitative welding performance evaluation tool for rail welding construction companies, which helps to optimize the welding process and improve the welding quality.

[0044] In an optional example of this embodiment, when the average value of the equivalent amplitude is greater than a threshold value, the defective rate of the rail welding joint of the to-be-welded rail is greater than a normal level.

[0045] The method for evaluating the process welding of rails of the present invention:

[0046] (1) A threshold value of α = 10% is proposed, and the difference between the average value of the equivalent amplitude and the threshold value is used to evaluate the process weldability of the rail:

[0047] (2) When the average value of the equivalent amplitude is less than the threshold value, the defective rate of the rail welding joint can be maintained at a normal level (less than 2%), and it can be judged that the process weldability of the rail is normal;

[0048] (3) The smaller the average value of the equivalent amplitude is than the threshold value, the better the process weldability of the rail is, which is manifested as being easier to weld;

[0049] (4) When the average value of the equivalent amplitude is greater than the threshold value, the defective rate of the rail welding joint increases, and the process weldability of the rail begins to deteriorate;

[0050] (5) The larger the average value of the equivalent amplitude is than the threshold value, the worse the process weldability of the rail is, which is manifested in the higher rate of unqualified products of the rail welding joint and the greater the welding difficulty;

[0051] (6) The rail head test specimen and the rail bottom test specimen 40 processed from the same rail may have different equivalent amplitude average values, which can respectively reflect the welding difficulty of the rail head 10 and the rail bottom 20.

[0052] In actual quality control, the defective rate of rail welded joints must be less than 2%, which is a strict quality control target, which means that when welding rails, the proportion of unqualified welded joints to the total number of welded joints should be controlled below 2% to ensure the normal production of rail welding and ensure that the welded joints meet the requirements of the railway industry standard TB / T1632.1~.4. According to the provisions of the railway industry standard TB / T1632.1~.4, the quality inspection of welded joints includes multiple aspects, such as appearance, ultrasonic flaw detection, drop hammer, static bending, fatigue, tensile, impact test, etc. These inspection items are all to ensure that the performance of welded joints meets the specified technical requirements. Therefore, a defective rate of less than 2% is a strict quality control target, requiring the welding process to be highly reliable to ensure the normal production of rail welding and ensure that the welded joints meet the requirements of the railway industry standard TB / T1632.1~.4.

[0053] In the method for evaluating the process weldability of rails of the present invention, the method for predicting the defective product rate of the welded joint of the rails to be welded according to the comparison result of the equivalent amplitude average value and the threshold value in the ultrasonic detection echo data can significantly reduce the generation of defective products in the welding process, thereby reducing rework and material waste. By identifying the rails that may have welding quality problems in advance, the enterprise can adjust the welding process parameters in time, optimize the production plan, improve production efficiency, and reduce construction costs.

[0054] In an optional example of this embodiment, the equivalent amplitude is the average value of the height of the ultrasonic detection echo appearing in the predetermined section of the ultrasonic transmission path. In the method for evaluating the process weldability of the rail of the present invention, the sampled rails to be welded are carefully tested by using ultrasonic detection means. The ultrasonic flaw detector is used to scan the test sample of the rail to collect the ultrasonic detection echo signal appearing in the predetermined section of the ultrasonic transmission path. These signals reflect the subtle changes in the internal structure of the rail and are an important basis for evaluating the welding performance. By calculating the height average of these echo signals, that is, the equivalent amplitude, a key parameter representing the welding performance of the rail can be obtained. The equivalent amplitude is the average value of the echo height during the reflection and propagation of the ultrasonic wave inside the rail in a specific section, which provides accurate data support for the optimization of the rail welding process. The method for evaluating the process weldability of the rail of the present invention can reveal the microstructural features inside the rail that may affect the welding quality, such as cracks, pores or other defects. By analyzing these features, it is possible to predict the problems that may occur in the welding process and guide the construction company to take corresponding preventive measures, such as adjusting the welding parameters or pre-treating the rail. .

[0055] In an optional example of this implementation, the calculation formula of the equivalent amplitude is:

[0056]

[0057] Where: h i is the equivalent amplitude of the measuring point 50i; t a is the starting point coordinate for calculating the equivalent amplitude; t b is the coordinate of the end point for calculating the equivalent amplitude; h is the coordinate of the starting point t a To the end point b The ultrasonic test echo height that appears in the test section. The values ​​of ta and tb in the formula can be changed.

[0058] The method for evaluating the process weldability of rails of the present invention proposes a definition and calculation method of equivalent amplitude, which is used to quantitatively calculate the ultrasonic detection echo value in a certain section of the ultrasonic transmission path when the ultrasonic detection probe detects at a certain measuring point 50. An example of an algorithm for calculating the equivalent amplitude is as follows: Figure 3 As shown, Figure 3The lines in the figure are ultrasonic echo images collected at a certain measuring point 50. The physical meaning of the equivalent amplitude calculated by formula (1) is to use Figure 3 The area enclosed by the red line in the calculation is divided by the distance between ta and tb. It should be noted that the denominator "t b —t a " is the calculated length of a certain section of the ultrasonic transmission path, and the numerator of the calculation formula is It is the area enclosed by the ultrasonic echo within the calculation length.

[0059] In an optional example of this implementation, the calculation formula for the average value of the equivalent amplitudes of multiple measuring points 50 is:

[0060]

[0061] Where: h i is the equivalent amplitude of measuring point 50i; n is the number of measuring points 50i, is the average value of 50 equivalent amplitudes at n measuring points. Figure 4 and Figure 5 As shown, on the test surface of the test sample, n test points 50 are randomly selected (generally n=10-20), and each test point 50 is distributed as evenly as possible, and the ultrasonic test probe is placed on the test surface, and ultrasonic test echo images are collected at each test point 50, and the ultrasonic test echo image of a certain test point 50 is collected on the test sample 30. Then, the equivalent amplitude hi of each test point 50 is calculated using the calculation formula of the equivalent amplitude, i=1-n.

[0062] In an optional example of this embodiment, the threshold value ranges from 9% to 11%. In the method for evaluating the process weldability of rails proposed in the present invention, the threshold value set can be changed, for example, the threshold value can be 9% or less, 11% or more, etc. Specifically, through in-depth experimental research and data analysis, a threshold value can be determined to ensure that it accurately reflects the quality of rail welding performance. At the same time, the threshold value also depends on the influence of the set ultrasonic detection sensitivity value. By adjusting the threshold value, construction companies can accurately predict the quality of welded joints and adjust welding process parameters in time, thereby improving the qualified rate of welded joints.

[0063] In an optional embodiment of the present invention, each batch of rails of the same model and brand is sampled and selected separately. It is very important to sample each batch of rails of the same model and brand separately, and separate sampling of each batch of rails provides more accurate data support for the optimization of the welding process of each batch, and specifies optimized welding parameters for each batch of rails, effectively reducing the defective rate of welded joints of each batch of rails.

[0064] In an optional embodiment of the present invention, the test sample includes a rail head test sample 30 and a rail bottom test sample 40, and the rail to be tested is prepared as the test sample, including: sawing a predetermined length of the rail to be tested; cutting the rail head test sample 30 at the rail head 10 of the rail to be tested, so that the rail head test sample 30 is in a rectangular parallelepiped shape, and the two cross sections of the rail to be tested are still the two cross sections of the test sample, the top surface of the rail of the test sample is processed as the top surface of the test sample, and another surface parallel to the top surface of the test sample is used as the bottom surface of the test sample, and the top surface and the bottom surface of the test sample are processed. All of them must be processed to ensure the roughness; a rail bottom test sample 40 is cut at the rail bottom 20 of the rail to be tested, so that the rail bottom test sample 40 is in the shape of a rectangular parallelepiped, and the two sections of the rail to be tested are still the two sections of the test sample. The lower surface of the rail of the test sample is processed as the bottom surface of the test sample, and the other surface parallel to the bottom surface of the test sample is used as the top surface of the test sample. Both the top and bottom surfaces of the test sample must be processed to ensure the roughness; the top surface of the rail head test sample 30 and the top surface of the rail bottom test sample 40 are used as test surfaces, and a plurality of measuring points 50 are respectively set on each test surface.

[0065] like Figure 1 and Figure 2 As shown in FIG. 1 , the preparation of the test sample includes obtaining the rail head test sample 30 and the rail bottom test sample 40. First, a rail is randomly selected from a batch of rails, and a section of the rail with a length of about 200 mm is sawed off as a sample; then, according to Figure 1 and Figure 2 As shown in the sampling diagram, the test sample is prepared, and the top and bottom surfaces of the test sample must be processed to ensure roughness, in order to avoid the surface roughness affecting the coupling of the ultrasonic probe. By specifying the preparation of the test sample and the setting of the measuring point 50 in detail, a comprehensive evaluation of the process weldability of the rail is achieved. The method for preparing the test sample in the present invention can provide detailed information about the rail welding area for evaluating the process weldability of the rail, including the welding performance of the two key parts of the rail head 10 and the rail bottom 20. Through ultrasonic testing of these parts, the uniformity of the internal structure of the rail and the difficulty of welding can be accurately evaluated, thereby predicting possible problems in the welding process.

[0066] In particular, the sampling location and size of the test specimen can be changed.

[0067] In an optional example of this embodiment, the detection surface of the detection sample is ground and the roughness of the detection surface reaches 0.8μm to 0.16μm. In order to eliminate the interference of the surface state of the sample on the ultrasonic detection, ensure good contact between the ultrasonic detection coupling agent and the detection surface, and reduce the energy loss of the ultrasonic wave before entering the rail. The detection surface of the detection sample should be ground by a surface grinder, and the roughness of the detection surface after grinding should reach 0.8μm to 0.16μm, and a universal ultrasonic detection coupling agent should be applied to the detection surface. By specifying the roughness range of the detection surface, the surface treatment of the detection surface reduces signal distortion, improves the accuracy of the detection result, and makes the weldability evaluation more accurate. The detailed explanation of the above-mentioned embodiments is only intended to explain the present invention so as to better understand the present invention. However, these descriptions cannot be interpreted as limiting the present invention for any reason. In particular, the various features described in different embodiments can also be arbitrarily combined with each other to form other embodiments. Unless there is a clear contrary description, these features should be understood to be applicable to any embodiment, and are not limited to the described embodiments.

Claims

1. A method for evaluating the process weldability of a rail, characterized in that: The steel rails to be welded are sampled and prepared as test specimens, a plurality of measuring points are selected on the test specimens, ultrasonic testing is performed on each of the measuring points and corresponding ultrasonic testing echo data is collected, and the process weldability of the steel rails to be welded is evaluated based on the ultrasonic testing echo data.

2. The method for evaluating the process weldability of a rail according to claim 1, characterized in that: Evaluating the process weldability of the to-be-welded rail according to the ultrasonic detection echo data includes: Calculate the equivalent amplitude of each measuring point according to the ultrasonic detection echo data of each measuring point; Calculate the average value of the equivalent amplitudes of the plurality of measuring points according to the equivalent amplitudes of the respective measuring points; A threshold value is set, and the process weldability of the to-be-welded rail is evaluated based on the difference between the average value of the equivalent amplitude and the threshold value.

3. The method for evaluating the process weldability of a rail according to claim 2, characterized in that: The smaller the average value of the equivalent amplitude is than the threshold value, the better the process weldability of the steel rail to be welded; the larger the average value of the equivalent amplitude is than the threshold value, the worse the process weldability of the steel rail to be welded.

4. The method for evaluating the process weldability of a rail according to claim 2, characterized in that: When the average value of the equivalent amplitude is greater than the threshold value, the defective rate of the rail welding joint of the to-be-welded rail is greater than a normal level.

5. The method for evaluating the process weldability of a rail according to claim 2, characterized in that: The equivalent amplitude is the average value of the ultrasonic detection echo height appearing in a predetermined section of the ultrasonic wave conduction path.

6. The method for evaluating the process weldability of a rail according to claim 2, characterized in that: The calculation formula of the equivalent amplitude is: Where: h i —Equivalent amplitude of measuring point i; t a —The coordinates of the starting point for calculating the equivalent amplitude; t b —Calculate the coordinates of the end point of the equivalent amplitude; h—from the starting point t a To the end point b The ultrasonic detection echo height that appears in the detection section.

7. The method for evaluating the process weldability of a rail according to claim 2, characterized in that: The calculation formula of the average value of the equivalent amplitude of multiple measuring points is: Where: h i —equivalent amplitude of measuring point i; n—number of measuring points i, —The average value of the equivalent amplitude of n measuring points.

8. The method for evaluating the process weldability of a rail according to claim 2, characterized in that: The threshold value ranges from 9% to 11%.

9. The method for evaluating the process weldability of a rail according to claim 1, characterized in that: The steel rails of the same model and brand are sampled from each batch separately.

10. The method for evaluating the process weldability of a rail according to claim 1, characterized in that: The test specimens include a rail head test specimen and a rail bottom test specimen. The test rails to be tested are prepared as test specimens, including: Sawing the steel rail to be tested to a predetermined length; The rail head test sample is cut at the rail head of the steel rail to be tested, so that the rail head test sample is in a rectangular parallelepiped shape, and the two cross sections of the steel rail to be tested are still the two cross sections of the test sample. The top surface of the steel rail of the test sample is processed as the top surface of the test sample, and the other surface parallel to the top surface of the test sample is used as the bottom surface of the test sample. Both the top surface and the bottom surface of the test sample must be processed to ensure the roughness; The rail bottom test sample is cut at the rail bottom of the steel rail to be tested, so that the rail bottom test sample is in a rectangular parallelepiped shape, and the two sections of the steel rail to be tested are still the two sections of the test sample. The lower surface of the steel rail of the test sample is processed as the bottom surface of the test sample, and the other surface parallel to the bottom surface of the test sample is used as the top surface of the test sample. Both the top surface and the bottom surface of the test sample must be processed to ensure the roughness; The top surface of the rail head inspection sample and the top surface of the rail bottom inspection sample are used as inspection surfaces, and a plurality of the measuring points are respectively arranged on each of the inspection surfaces.

11. The method for evaluating the process weldability of a rail according to claim 10, characterized in that: The detection surface is ground to a roughness of 0.8 μm to 0.16 μm.

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