Method for evaluating the scuffing resistance of a wheel-rail material

Abstract

The application provides an evaluation method for the scratch resistance of wheel-rail materials, and relates to the field of wheel-rail material performance evaluation, which comprises the following steps: preparing a rail steel sample and a wheel steel sample; using continuous driving friction welding to weld the rail steel sample and the wheel steel sample together, and forming a weld joint between the rail steel sample and the wheel steel sample; characterizing the microstructure of the weld joint; and evaluating the scratch resistance of the rail steel and the wheel steel according to the characterization. The evaluation method for the scratch resistance of wheel-rail materials can quantitatively evaluate the scratch resistance of wheel-rail materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of railway wheel-rail material performance evaluation, and particularly relates to a method for evaluating the scuffing resistance of wheel-rail material. BACKGROUND

[0002] Wheel-rail components are one of the core key components of rail transit, and their various performances during service directly affect the operation safety of rail transit. In actual service, scuffing is one of the most common damage forms of wheel-rail components, and scuffing is usually caused by abnormal sliding between wheel and rail, such as wheel startup idling or braking skid, and high creep rate destroys the normal rolling and sliding state between wheel and rail, and changes into a sliding-dominant motion state. The sliding friction generates heat to cause the rapid temperature rise of the wheel-rail contact surface and phase change into austenite, and the rapid cooling quenching process changes into martensite structure, and the abnormal structure formed in the scuffing process is usually referred to as white layer structure. The white layer structure is brittle and hard, and cracks are easily generated, forming wheel-rail tread fatigue damage and threatening the safe service of wheel-rail components.

[0003] Using wheel-rail materials with excellent scuffing resistance is a feasible method to reduce the harmfulness of scuffing and prolong the service life, especially for long and steep slopes or station lines prone to scuffing. However, the current wheel-rail material related standards and technical conditions do not involve the test method and evaluation standard of the scuffing resistance of wheel-rail materials, and therefore, how to compare the scuffing resistance of different wheel-rail materials is still in the blank stage.

[0004] Therefore, the present application is designed by the present inventors on the basis of years of production and design experience in the field and related fields, and through repeated experiments, in order to solve the problems in the prior art. SUMMARY

[0005] The present application aims to provide a method for evaluating the scuffing resistance of wheel-rail material, which can quantitatively evaluate the scuffing resistance of wheel-rail material.

[0006] To achieve the above-mentioned application purposes, the present application provides a method for evaluating the scuffing resistance of wheel-rail material, wherein the evaluation method comprises:

[0007] Preparation of a rail steel material sample and a wheel steel material sample;

[0008] Welding the rail steel material sample and the wheel steel material sample together, and forming a weld joint between the rail steel material sample and the wheel steel material sample;

[0009] Characterizing the microstructure of the weld joint, and evaluating the scuffing resistance of the rail steel material and the wheel steel material according to the characterization.

[0010] Compared with the prior art, the application has the following characteristics and advantages:

[0011] The evaluation method for the wear resistance of the wheel-rail material provided by the application simulates the working condition of the combined action of the friction heat and the friction force in the wheel-rail wear process by using the martensite structure formed in the weld structure after cooling, forms the white layer structure basically consistent with the real wear structure in the weld, and can effectively evaluate the wear resistance of the wheel-rail material by characterizing and calculating the key performance indicators and the microstructure of the weld structure. BRIEF DESCRIPTION OF DRAWINGS

[0012] The drawings described herein are only for the purpose of explanation, and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes and scale sizes of the components in the drawings are only illustrative, and are used to help understand the present application, and are not specific limitations on the shapes and scale sizes of the components of the present application. Those skilled in the art can select various possible shapes and scale sizes to implement the present application according to specific circumstances under the teaching of the present application.

[0013] Figure 1 The flowchart of the evaluation method for the wear resistance of the wheel-rail material provided by the application;

[0014] Figure 2 The schematic diagram of the continuous drive friction welding in the present application;

[0015] Figure 3 The schematic diagram of the measurement of the white layer thickness in the present application;

[0016] Figure 4 The schematic diagram of the measurement of the white layer hardness in the present application.

[0017] Explanation of reference signs:

[0018] 10, steel rail steel material sample; 20, wheel steel material sample;

[0019] 30, weld; 1, main drive system;

[0020] 2, rotating side clamping system; 3, moving side clamping system;

[0021] 4, fixed sliding table; 5, hydraulic system. DETAILED DESCRIPTION

[0022] The details of the present application can be more clearly understood in combination with the description of the specific embodiments of the present application and the accompanying drawings. However, the specific embodiments of the present application described herein are only for the purpose of explaining the present application, and cannot be understood in any way as a limitation on the present application. Under the teaching of the present application, those skilled in the art can conceive any possible deformation based on the present application, which should be considered as belonging to the scope of the present application.

[0023] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component. When a component is referred to as "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0024] This invention proposes a method for evaluating the scratch resistance of wheel and rail materials, the evaluation method comprising:

[0025] Prepare rail steel material sample 10 and wheel steel material sample 20;

[0026] The rail steel material sample 10 and the wheel steel material sample 20 are welded together, and a weld 30 is formed between the rail steel material sample 10 and the wheel steel material sample 20.

[0027] The microstructure of weld 30 was characterized, and the scratch resistance of rail steel and / or wheel steel was evaluated based on the characterization.

[0028] The method for evaluating the scratch resistance of wheel and rail materials proposed in this invention utilizes the martensitic structure formed in the weld structure after cooling to simulate the working conditions of frictional heat and frictional force during the wheel and rail scratching process. A white layer structure that is basically consistent with the actual scratch structure is formed in the weld. By characterizing and calculating the microstructure of the key performance indicators of the weld structure, the scratch resistance of wheel and rail materials can be effectively evaluated.

[0029] The method for evaluating the scratch resistance of wheel and rail materials proposed in this invention can quantitatively evaluate the scratch resistance of existing wheel and rail materials, thereby selecting steels with excellent scratch resistance and providing experimental basis for wheel and rail selection. At the same time, it is beneficial for the development of new wheel and rail materials with excellent scratch resistance.

[0030] In an optional embodiment of the present invention, the rail steel material sample 10 is cut 5 mm below the center tread of the actual rail.

[0031] In an optional embodiment of the present invention, the wheel steel material sample 20 is cut 5 mm below the center tread of the actual wheel.

[0032] In an optional embodiment of the present invention, both the rail steel material sample 10 and the wheel steel material sample 20 are rod-shaped.

[0033] In an optional example of this embodiment, the dimensions of the rail steel material sample 10 are: diameter φ16mm±0.05 and length 130±0.1mm.

[0034] In an optional example of this embodiment, the wheel steel material sample 20 has dimensions of φ16mm±0.05 and a length of 65±0.1mm.

[0035] In an optional example of this embodiment, the machining requirements for the rail steel material sample 10 and the wheel steel material sample 20 are: roughness Ra≤3.2μm, no chamfer on the end face, and no pin holes on at least one side.

[0036] In an optional embodiment of the present invention, the welding adopts continuous drive friction welding, which is a mature welding technology. Its welding process is similar to the actual rail wheel scratching process, effectively simulating the working conditions of frictional heat and frictional force acting together in the wheel-rail scratching process. Under the rapid cooling rate, a white layer structure that is basically consistent with the actual scratch structure can be formed.

[0037] In one optional example of this implementation, a gas valve friction welding machine is used for continuous drive friction welding.

[0038] In an optional example, such as Figure 2 As shown, the air valve friction welding machine includes a main drive system 1, a rotating side clamping system 2, a moving side clamping system 3, a fixed slide table 4, and a hydraulic system 5. The wheel steel material sample 20 and the rail steel material sample 30 are clamped in the rotating side clamping system 2 and the moving side clamping system 3, respectively. The main drive system 1 drives the rotating side clamping system 2 to rotate. The wheel steel material sample 20 is clamped in the rotating side clamping system 2 (spindle rotation end) to match the actual working condition of wheel rotation. The rail steel material sample 10 is clamped in the moving side clamping system 3 (sliding end), and the hydraulic system 5 provides upsetting pressure to simulate wheel-rail contact stress.

[0039] The specific welding process can be divided into three stages. First, the main shaft of the main drive system 1 rotates to the target speed. Then, the hydraulic system 5 pushes the rail steel material sample 10 of the moving side clamping system 3 (sliding end) to contact the rotating wheel steel material sample 20 with a first-level pressure. Friction generates heat and melts the metal. Finally, a certain upsetting pressure is used to connect the metal samples on both sides to each other.

[0040] Preferably, the specific experimental parameters for inertial friction welding are: spindle speed 2000 rpm; first-stage pushing pressure 15 kN, holding time 0.4 s; displacement speed 1 mm / s; upsetting pressure 10 kN, holding time 0.6 s; displacement speed 0.5 mm / s.

[0041] In an optional embodiment of the present invention, characterizing the microstructure of the weld includes:

[0042] Measure the thickness of the white layer in the weld; measure the hardness of the white layer in the weld and the hardness of the corresponding base material.

[0043] In this invention, characterization of the microstructure of the abrasion tissue reveals that abrasion mainly involves two phase transformation processes: first, the pearlite matrix transforms into austenite upon heating; second, the austenite transforms into martensite during rapid cooling. The final abrasion white layer is a mixed phase, primarily martensite, but also containing a certain volume fraction of retained austenite and carbides. Evaluating the abrasion resistance essentially involves comparing the thickness of the white layer with its strength and toughness. Under the same conditions, a thinner white layer and better toughness result in better abrasion resistance.

[0044] In this embodiment, the base material refers to the wheel steel base material or the rail steel base material.

[0045] In an optional example, such as Figure 3 As shown, the thickness of the white layer is the distance T from the weld centerline to the corresponding base material boundary line.

[0046] In one optional example, for ease of measurement and to reduce errors, the measurement is uniformly performed at a depth of 1 mm below the surface of the circumferential sample.

[0047] Specifically, the thickness of the white layer of the rail steel material is the distance T from the weld centerline to the boundary line of the rail steel material. 钢轨钢 The thickness of the white layer of the wheel steel material is T, which is the distance T from the weld centerline to the boundary line of the wheel steel material. 车轮钢 .

[0048] In one optional example of this implementation, such as Figure 4 As shown, the hardness of the white layer structure in the weld and the corresponding hardness of the base metal structure were measured. Specifically, micro Vickers hardness measurements were performed at a depth of 1 mm below the surface of the circumferential sample. ≥10 points were measured uniformly along the arrow direction in the white layer structure area, and ≥5 points were measured uniformly in the base metal structure. The average value of the micro Vickers hardness of the white layer structure was calculated to obtain H1, and the average value of the micro Vickers hardness of the base metal structure was H2.

[0049] In an optional example, the hardness of the white layer structure on the wheel steel material side and the hardness of the wheel steel material are measured. Specifically, micro Vickers hardness measurement is performed at a depth of 1 mm below the surface of the wheel steel material sample 10. The white layer structure area is measured at ≥10 points uniformly along the arrow direction, and the wheel steel material structure is measured at ≥5 points uniformly.

[0050] In an optional example, the hardness of the white layer structure on the rail steel material side and the hardness of the rail steel material are measured. Specifically, micro Vickers hardness measurement is performed at a depth of 1 mm below the surface of the rail steel material sample 10. The white layer structure area is measured at ≥10 points uniformly along the arrow direction, and the rail steel material structure is measured at ≥5 points uniformly.

[0051] In an optional embodiment of the invention, evaluating the scratch resistance of rail steel and / or wheel steel materials based on the characterization includes,

[0052] Calculate the hardening coefficient of the base material based on the hardness of the white layer and the hardness of the base material.

[0053] The scratch resistance index of the corresponding base material is calculated based on the thickness of the white layer and the hardening coefficient.

[0054] In one alternative example, the hardening factor H = H1 / H2.

[0055] Specifically, the hardening coefficient H of wheel steel 车轮钢 =H1 hardness of the white layer on the side of the wheel steel material 车轮钢 / Hardness of wheel steel material H2 车轮钢 .

[0056] Hardening coefficient H of rail steel 钢轨钢 = Hardness H1 of the white layer of steel rail material 钢轨钢 / H2 hardness of steel rail material 钢轨 steel.

[0057] In one optional example, the scratch resistance index A = white layer thickness T × hardening coefficient H.

[0058] Specifically, the scratch resistance performance index of wheel steel material A = white layer thickness T 车轮钢 × Hardening coefficient H 车轮钢 The scratch resistance index of rail steel material A = white layer thickness T 钢轨钢 × Hardening coefficient H 钢轨钢 .

[0059] In one alternative example, the lower the value of the abrasion resistance index A, the better the abrasion resistance of the corresponding base material.

[0060] It should be noted that due to the stress characteristics of friction welding, the thickness of the white layer produced on the rotating end and the moving end differs. Therefore, when comparing anti-scratch performance indicators, only comparisons can be made between rail steel or wheel steel, and not between rail steel and wheel steel.

[0061] The following is a detailed description of the specific implementation process of the method for evaluating the scratch resistance of wheel and rail materials proposed in this invention, with reference to an embodiment:

[0062] First, identify the research subjects.

[0063] The material to be evaluated (rail steel or wheel steel) should be clearly identified. In this embodiment, the scratch resistance of rail steel of different materials is evaluated. Therefore, the wheel steel should be of the same material, such as CL60 or ER8.

[0064] Prepare the test specimens according to the above processing dimensions. To ensure the reliability of the test results, at least 3 sets of samples should be prepared for repeated testing.

[0065] Afterwards, the continuous drive friction welding machine was debugged and welding was carried out.

[0066] During the commissioning and testing of the continuous drive friction welding machine, the design commands should be input, and the deviation between the measured pressure value and the design pressure value should be controlled within 10%. After the equipment commissioning is completed, all planned tests should be completed in one go as much as possible to avoid the influence of equipment stability on the test results.

[0067] After welding, the sample was allowed to cool naturally in air at room temperature (20-25°C).

[0068] Finally, laboratory microscopic characterization and calculations were performed.

[0069] The welded specimen was partially cut open using a wire cutting device to prepare a metallographic specimen. The specimen was then etched with a 4% nitric acid alcohol solution. The microstructure of the weld was observed under a metallographic microscope to clarify the boundary between the weld centerline and the base material (rail steel), and the thickness T of the white layer was measured.

[0070] The hardness of the white layer structure and the base material structure (rail steel) was measured using a micro Vickers hardness tester. It is recommended to use a uniform downward pressure of 100gf for testing, record the corresponding data values, and statistically calculate H1 and H2.

[0071] Calculate the scratch resistance index A for different steel grades (rail steel) and compare and evaluate the scratch resistance of different steel grades.

[0072] The present invention proposes two methods for evaluating the scratch resistance of wheel and rail materials. First, based on a continuously driven friction welding machine, friction welding tests are conducted on the wheel and rail materials. The parameters used in the welding tests should ensure that the weld microstructure of the test material is a white layer structure, the weld zone width has certain differences and comparability, and the variance of repeated experiments is small. Second, microstructural analysis is performed on the white layer structure of the weld, key performance indicators are measured, and an evaluation algorithm is designed to form a comprehensive index that can evaluate scratch resistance.

[0073] 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 evaluating the scratch resistance of wheel and rail materials, characterized in that, The evaluation methods include: Prepare rail steel material samples and wheel steel material samples; The rail steel material sample and the wheel steel material sample are welded together, and a weld is formed between the rail steel material sample and the wheel steel material sample. The microstructure of the weld is characterized, and the scratch resistance of the rail steel and wheel steel is evaluated based on the characterization. Characterizing the microstructure of the weld includes: Measure the thickness of the white layer from the weld centerline to the base material; The hardness of the white layer in the weld and the hardness of the corresponding base metal were measured respectively. The scratch resistance of the rail steel and wheel steel materials is evaluated based on the characterization, including: The hardening coefficient of the base material is calculated based on the hardness of the white layer and the hardness of the base material. The scratch resistance index of the corresponding base material is calculated based on the white layer thickness and the hardening coefficient. The hardening coefficient H = H1 / H2; where H1 is the average value of the micro Vickers hardness of the white layer structure, and H2 is the average value of the micro Vickers hardness of the parent material structure. The scratch resistance index A = white layer thickness T × hardening coefficient H; The lower the value of the abrasion resistance index A, the better the abrasion resistance of the corresponding base material.

2. The method for evaluating the scratch resistance of wheel and rail materials as described in claim 1, characterized in that, The steel material sample for the rail was cut 5 mm below the center tread of the actual rail.

3. The method for evaluating the scratch resistance of wheel and rail materials as described in claim 1, characterized in that, The steel material sample for the wheel was cut 5 mm below the center tread of the actual wheel.

4. The method for evaluating the scratch resistance of wheel and rail materials as described in claim 1, characterized in that, Both the rail steel material sample and the wheel steel material sample are rod-shaped.

5. The method for evaluating the scratch resistance of wheel and rail materials as described in claim 1, characterized in that, The welding is performed using continuous drive friction welding.

6. The method for evaluating the scratch resistance of wheel and rail materials as described in claim 5, characterized in that, Continuous friction welding was performed using a gas valve friction welding machine.

7. The method for evaluating the scratch resistance of wheel and rail materials as described in claim 1, characterized in that, The base material is wheel steel or rail steel.

8. The method for evaluating the scratch resistance of wheel and rail materials as described in claim 1, characterized in that, The thickness of the white layer is the distance from the weld centerline to the corresponding base material boundary line.

9. The method for evaluating the scratch resistance of wheel and rail materials as described in claim 1, characterized in that, The lower the value of the scratch resistance index, the better the scratch resistance of the corresponding base material.

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