Heat treatment method for improving wear resistance and uniformity of end part of steel rail

Abstract

The invention relates to a heat treatment method for improving wear resistance and uniformity of the end part of a steel rail. The heat treatment process of the end part of the steel rail comprises an induction heating process, an air spraying cooling process and a steel rail position adjusting process, according to the use characteristics of the hole rail, the end of the steel rail is heated through an induction heating process, and the requirement for austenite homogenization is met; the wear resistance and the uniformity of the end part of the steel rail are improved by combining an air spraying cooling process and position movement of the steel rail in a unit; the surface hardness of a stable hardening area of the steel rail tread is improved, and the hardness of the cross section is slowly reduced in a gradient manner from outside to inside; the transition between the steel rail end heat treatment performance and the steel rail full-length hot rolling state performance is good, the service life of the steel rail is effectively prolonged, and abrasion under heavy loads is relieved.

Description

Technical Field

[0001] The present invention relates to the technical field of rail production, and particularly relates to a heat treatment method for improving the wear resistance and uniformity of rail ends. Background Art

[0002] With the increasing growth of railway transportation volume and the development of railways towards high speed and heavy haul, the quality requirements for rails are getting higher and higher. When rails are usually used without welding, the connection between each section of the rail is achieved through bolt connection. When the train runs and the wheels pass over the connection seam between two sections of the rail, due to unevenness, the force on the rail ends is often complex and severe, resulting in wear, flattening or crushing. In severe cases, the rail may break. According to statistics, the wear of the rail ends is 5 - 7 times faster than that of the rail body. In order to increase the service life of the rail, improving the wear resistance of the rail ends should be considered first.

[0003] The main factors affecting the wear resistance of rails include the hardness of their treads and the tissue uniformity, and the heat treatment method can improve these two aspects of performance simultaneously. Generally, the heating temperature range, the overall temperature uniformity, and the cooling rate are the main factors affecting the heat treatment effect of rails. Any change in one of these factors will cause corresponding changes in the final performance of the rails.

[0004] There are strict requirements for the hardened layer of rails at home and abroad. The relevant standards stipulate that the shape of the hardened layer is cap-shaped, the depth of the tread hardened layer ≥ 10 mm and the lower jaw part ≥ 6 mm, the tread hardness ≥ 302 HBW, and the stable hardened layer ≥ 60 mm, and its microstructure is pearlite and a small amount of ferrite. However, the surface hardened layer of the rail head produced at present can only reach the middle and lower limits of the standard requirements. During actual service, as the heavy haul degree gradually increases, the surface hardened layer of the rail head is continuously worn and its hardness gradually decreases; at the same time, the different depths of the hardened layer cause uneven stress, and thus the wear resistance also decreases, resulting in a shortened service life of the rail.

[0005] In summary, it is necessary to develop a heat treatment method that can improve the wear resistance and wear uniformity of rail ends to improve the quality of rails and extend the service life of rails, which is also an inevitable trend in the development of rail production technology.

[0006] The Chinese patent application with the application number CN 202110576248.2 discloses "a production method for improving the wear resistance of heat-treated steel rails", which includes dynamically accelerating the cooling heat treatment of the rail head after hot rolling. Among them, the starting cooling temperature is controlled at 720 - 800 °C, and a dynamic phased cooling process is adopted, that is, the entire cooling process of the rail head is divided into 7 stages. The cooling rate in the first stage is 5 - 7 °C / s, the cooling rate in the second stage is 7 - 8 °C / s, the cooling rate in the third stage is 8 - 10 °C / s, the cooling rate in the fourth stage is 1 - 2 °C / s, the cooling rate in the fifth stage is 4 - 6 °C / s, the cooling rate in the sixth stage is 3 - 4 °C / s, and the cooling rate in the seventh stage is 2 - 3 °C / s. When the temperature of the rail head drops below 300 °C, the accelerated cooling is stopped, and finally it is naturally cooled to room temperature. It improves the wear resistance of the steel rail by reasonably controlling the cross-sectional Rockwell hardness distribution, and at the same time ensures that the rail head has good toughness, improving the comprehensive service performance of the steel rail. However, its cooling process is too cumbersome and difficult to implement in actual production.

[0007] The Chinese patent application with the application number CN 202211358587.4 discloses "a production method for improving the wear resistance of steel rails", which includes the smelting production process and rolling process of steel. The temperature of the billet heating preheating section is not greater than 900 °C; the heating duration is not less than 3 hours and 15 minutes; the tapping temperature is not lower than 1150 °C, the rolling start temperature is 1060 °C - 1130 °C, and the finishing rolling temperature is 910 - 940 °C; the online waste heat quenching cooling medium is a mixture of aerosol + air; the heat treatment temperature is determined by combining the phase transformation temperature parameters in the steel and the actual capacity of industrial equipment. The heat treatment temperature at the start after the finishing rolling of the steel rail is 720 °C - 770 °C, and after passing through the cooling equipment, the steel rail undergoes transformation within the pearlite transformation temperature range. After 100 - 120 s of online heat treatment, it exits the heat treatment production line, and the outlet temperature of the steel rail is 520 °C - 600 °C. After exiting the heat treatment production line, it is naturally air-cooled to room temperature. Its purpose is to produce a heat-treated steel rail with higher wear resistance. However, the online waste heat quenching method is not applicable to improving the wear resistance of the rail end. At the same time, performing end quenching and full-length air cooling easily causes the length of the transition zone to exceed the standard, and there are large residual stresses, resulting in an increased tendency of rail breakage during subsequent use.

[0008] The Chinese patent application with application number CN 202211046073.5 discloses "A high-strength, tough, wear-resistant heat-treated rail for high-speed railway and its production method", and the rail composition is C: 0.60%~0.90%, Si: 0.50%~1.00%, Mn: 0.60%~1.90%, P: ≤0.025%, S: ≤0.015%, Cr: 0.10%~0.25%, Sb: 0.001%~0.015%, Cu: 0.01%~0.10%, V: 0.01%~0.20%, Nb: 0.0 At least one of 1% to 0.20%, Ti: 0.01% to 0.10%, the balance is Fe and unavoidable impurities; rail tensile strength 1220 to 1280MPa, yield strength 650 to 750MPa, elongation ≥11%; rail head surface Brinell hardness HBW: 365 to 385, rail head cross-section Rockwell hardness HRC: A1, B1, C1, D1, E1 are 37 to 39, A4, B5, C5, D3, E3 are 35 to 36; -20℃ fracture toughness minimum average value is 32MPa·m1 / 2. It has excellent strength, toughness and hardness indicators, and is suitable for laying high-speed railways with a speed of more than 200 kilometers per hour and a radius of 2800 meters or less, taking into account freight. However, this type of rail is not suitable for heavy-load transportation on non-welded sections.

[0009] The Chinese patent application with application number CN 202311603170.4 discloses "a method for producing a rail with high wear resistance", including adding Nb to the rail, optimizing and controlling the content of Cr, Nb and RE, and combining optimized rail rolling process parameters and heat treatment process parameters to obtain a rail material with high strength and hardness, thereby improving the wear resistance of the rail and avoiding premature wear and failure of the rail. However, improving the wear resistance of the rail by microalloying metallurgical methods has led to a significant increase in production costs.

[0010] The Chinese patent application with application number CN 202311692656.X discloses "a high plasticity wear-resistant rail material and its preparation method". By optimizing and controlling the heating, rolling and heat treatment cooling process system in the rail rolling process, and optimizing and controlling the chemical composition content of the rail, a high plasticity wear-resistant rail material with an elongation δ ≥ 19.5% is provided, which can significantly improve the safety performance of the rail product, and the other mechanical properties of the prepared rail are also relatively good, meeting the following requirements: tensile strength ≥ 1144MPa, average Brinell hardness ≥ 323HB, so it also has high strength and hardness, and good wear resistance. However, this method mainly improves the plastic toughness of the rail, does not reflect the improvement of wear resistance and hardness, and the addition of rare earth increases the production cost. Summary of the invention

[0011] The present invention provides a heat treatment method for improving the wear resistance and uniformity of the rail ends. According to the usage characteristics of the hole rails, the rail ends are heated by an induction heating process to meet the requirements of austenite homogenization; combined with the air-blowing cooling process and the position movement of the rails in the unit, the wear resistance and uniformity of the rail ends are improved; not only the surface hardness of the stable hardening zone on the rail tread is increased, but also the cross-sectional hardness gradually decreases in a gradient from the outside to the inside; the heat treatment performance of the rail ends has a good transition with the hot-rolled state performance of the entire length of the rails, effectively improving the service life of the rails and reducing the wear under heavy loads.

[0012] To achieve the above object, the present invention is implemented by the following technical solutions:

[0013] A heat treatment method for improving the wear resistance and uniformity of the rail ends, the heat treatment process of the rail ends includes an induction heating process, an air-blowing cooling process, and a rail position adjustment process; specifically as follows:

[0014] 1) Induction heating process: The heating temperature on the surface of the rail head is greater than 850 °C. The rail end is pushed into the induction heating device, and the induction coil of the induction heating device is connected to a medium-frequency alternating current of 1.0 - 2.0 kHz. After heating for 24 - 30 s, the austenite homogenization temperature of 900 - 930 °C is reached.

[0015] 2) Air-blowing cooling process: The rail end heated to the austenite homogenization temperature is pushed into the air-blowing cooling device within 10 s, and the air-blowing cooling is carried out in two stages; in the first stage of air-blowing cooling, the temperature is decreased at a cooling rate of 7 - 9 °C / s to 650 - 700 °C, and after stopping the air-blowing, it is maintained for more than 10 s; in the second stage of air-blowing cooling, the temperature is decreased at a cooling rate of 10 - 12 °C / s to 450 - 500 °C. After stopping the air-blowing, the rail end is sent to the cooling bed for air cooling and tempered using the residual heat.

[0016] 3) Rail position adjustment process:

[0017] After the start of the second-stage air-blowing cooling in process 2), the rail end is pushed out of the air-blowing cooling device at a speed of 1.5 - 2.5 mm / s. By means of heat conduction and convective heat transfer, the temperature of the rail end and the heated part of the rail body near the rail end is made to tend to be consistent, and the maximum temperature difference between the two is controlled ≤ 20 °C.

[0018] During the induction heating process, the length of the rail end pushed into the induction heating device is 110 - 120 mm.

[0019] During the induction heating process, the induction coil of the induction heating device is connected to a medium-frequency alternating current of 1.0 - 1.5 kHz.

[0020] The chemical elements of the steel rail are by weight percentage: C: 0.70% - 0.75%, Si: 0.40% - 0.60%, Mn: 0.90% - 1.10%, P ≤ 0.015%, S ≤ 0.010%, and the balance is Fe and inevitable impurities.

[0021] The production process of the steel rail includes vacuum smelting, continuous casting, heating, high-pressure water descaling, rolling, cooling on the cooling bed, straightening, and end heat treatment; after straightening, flaw detection is carried out, and after passing, end heat treatment is carried out.

[0022] The microstructure of the surface hardened layer at the end of the steel rail after end heat treatment is: the surface layer is sorbite structure, and the inner layer is pearlite structure.

[0023] After end heat treatment, the depth of the hardened layer on the tread at the end of the steel rail is ≥ 18 mm; the length of the stable hardening zone is ≥ 90 mm; the length of the transition zone is ≤ 25 mm; the hardness of the tread at the end of the steel rail is ≥ 350 HB; the hardness from the surface to the core of the cross-section at the end of the steel rail decreases step by step within the range of 370 - 280 HV.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) By the heat treatment method of induction heating and air spraying cooling, the present invention forms a surface hardened layer with a depth of more than 18 mm under the tread at the end of the hot-rolled steel rail. Its surface layer is refined pearlite structure, i.e., sorbite structure, and the inner layer is pearlite structure; the hardness of the tread at the end of the rail is ≥ 350 HB, and the plastic toughness is not lost; compared with the hardness of hot-rolled U71Mn (the standard is 260 - 300 HBW), the surface hardness of the stable hardening zone of the rail tread is increased by 20% - 35%, improving the wear resistance and uniformity of the end of the steel rail.

[0026] (2) From the production perspective, the present invention only conducts heat treatment on the rail end, which not only saves the process cost but also improves the processing efficiency; from the service perspective, by increasing the hardness and wear resistance of the rail end, the present invention increases the service life of the steel rail and reduces the wear under heavy loads.

[0027] (3) By adding the process of moving the position of the steel rail in the unit during the heat treatment process, the present invention obtains a surface hardened layer that is all pearlite structure, without abnormal structures such as martensite and bainite; at the same time, the overall hardened layer depth ≥ 18 mm and is uniform, the length of the stable hardening zone is extended (≥ 90 mm), and the length of the transition zone is shortened (≤ 25 mm); in addition, it ensures that the cross-sectional hardness from the surface to the core decreases slowly in a gradient within the range of 370 - 280 HV, and the heat treatment performance at the end of the rail and the hot-rolled performance of the whole length of the rail have a good transition, improving the uniformity of the wear-resistant layer.

[0028] (4) The method of the present invention is applicable to pearlite steel rails connected by bolts. Brief Description of the Drawings

[0029] Figure 1 It is a schematic diagram when the steel rail described in the present invention is subjected to induction heating.

[0030] Figure 2 It is a schematic diagram when the steel rail described in the present invention is subjected to air-blowing cooling.

[0031] Figure 3 It is a schematic diagram of the position movement of the steel rail described in the present invention during heat treatment.

[0032] In the figure: 1. Steel rail; 2. Induction heating device; 3. Air-blowing cooling device Detailed Embodiment

[0033] The following further describes the detailed embodiment of the present invention in conjunction with the drawings:

[0034] As Figures 1 - 3 shown, for a heat treatment method for improving the wear resistance and uniformity of the end of a steel rail described in the present invention, the end heat treatment process of the steel rail 1 includes an induction heating process, an air-blowing cooling process, and a steel rail position adjustment process; specifically as follows:

[0035] 1) Induction heating process: The heating temperature on the surface of the rail head of the steel rail 1 is greater than 850 °C. Push the end of the steel rail 1 into the induction heating device 2. The induction coil of the induction heating device is connected to an intermediate-frequency alternating current of 1.0 - 2.0 kHz (preferably 1.0 - 1.5 kHz). After heating for 24 - 30 s, it reaches the austenite homogenization temperature of 900 - 930 °C;

[0036] 2) Air-blowing cooling process: Push the rail end heated to the austenite homogenization temperature into the air-blowing cooling device 3 within 10 s, and perform air-blowing cooling in two stages; In the first stage of air-blowing cooling, cool down at a cooling rate of 7 - 9 °C / s to 650 - 700 °C, and keep it for more than 10 s after stopping the air-blowing; In the second stage of air-blowing cooling, cool down at a cooling rate of 10 - 12 °C / s to 450 - 500 °C. After stopping the air-blowing, send the rail end into the cooling bed for air cooling and utilize the residual heat for tempering;

[0037] 3) Steel rail position adjustment process:

[0038] After the start of the second-stage air-blowing cooling in process 2), push the rail end out of the air-blowing cooling device 3 at a speed of 1.5 - 2.5 mm / s, and make the temperature of the rail end tend to be consistent with the heated part of the rail body near the rail end by means of heat conduction and convective heat transfer, and control the maximum temperature difference between the two ≤ 20 °C.

[0039] In the said process 1), the length of the end of the steel rail 1 pushed into the induction heating device 2 is 110 - 120 mm.

[0040] In the process 1), the induction coil of the induction heating device is connected to an intermediate frequency alternating current of 1.0 - 1.5 kHz.

[0041] The chemical elements of the steel rail 1 are by weight percentage: C: 0.70% - 0.75%, Si: 0.40% - 0.60%, Mn: 0.90% - 1.10%, P ≤ 0.015%, S ≤ 0.010%, and the balance is Fe and unavoidable impurities.

[0042] The production process of the steel rail 1 includes vacuum smelting, continuous casting, heating, high-pressure water descaling, rolling, cooling on the cooling bed, straightening, and end heat treatment; after straightening, flaw detection inspection is carried out, and after passing, end heat treatment is carried out.

[0043] The microstructure of the surface hardened layer at the end of the steel rail after end heat treatment is: the surface layer is sorbite structure, and the inner layer is pearlite structure.

[0044] After end heat treatment, the depth of the hardened layer on the tread at the end of the steel rail 1 ≥ 18 mm; the length of the stable hardening zone ≥ 90 mm; the length of the transition zone ≤ 25 mm; the hardness of the tread at the end of the steel rail 1 ≥ 350 HB; the hardness of the cross-section of the steel rail 1 from the surface to the core decreases step by step within the range of 370 - 280 HV.

[0045] The design principle of the induction heating process described in the present invention is as follows:

[0046] Due to the temperature difference between the surface and the core during rail end heating, in order to completely austenitize the metal at the rail end core, the heating temperature of the rail end surface must be greater than 850 °C; and from the perspective of production, the shorter the time, the higher the output per unit time. Therefore, after pushing 110 - 120 mm of the rail end into the induction heating device, the induction coil of the induction heating device is connected to an intermediate frequency alternating current of 1.0 - 2.0 kHz, generating a large amount of resistance heat, so that the surface layer of the rail end quickly reaches the quenching temperature. According to the requirement of the hardened layer depth, the intermediate frequency alternating current connected to the induction coil is preferably 1.2 kHz. After heating for 24 - 30 s, the austenite homogenization temperature of 900 - 920 °C is reached, and then the next step of air spraying cooling process is carried out.

[0047] The design principle of the air spraying cooling process described in the present invention is as follows:

[0048] In a relatively wide cooling rate range with a continuous cooling rate V≈10℃ / s, pearlite transformation occurs in the undercooled austenite, resulting in pearlite structures with different fineness and thicknesses of lamellae. At the same time, in order to avoid the formation of bainite and martensite and ensure that only pearlite structure is formed, the accelerated cooling process must avoid the bainite phase transformation region of 350 - 500℃. Therefore, in the present invention, the rail end after being heated to the austenite homogenization temperature is pushed into the air-blowing cooling device within 10 s. First, the first-stage air-blowing cooling is carried out, and the cooling rate V1 is reduced to 650 - 700℃ at a cooling rate of 7 - 9℃ / s and then the air-blowing is stopped and maintained for more than 10 s. While retaining the fine grains of austenite, the temperature inside and outside the rail becomes closer, preventing the appearance of coarse grains inside the rail from affecting plasticity and toughness. Then, the second-stage air-blowing cooling is carried out, and the cooling rate V2 is increased to 10 - 12℃ / s. A finer pearlite lamella is obtained on the surface layer of the rail to improve hardness and wear resistance. The air-blowing cooling ends when the temperature reaches 450 - 500℃. The rail end is sent to the cooling bed for air cooling and tempering using the waste heat to eliminate the residual stress generated due to rapid cooling.

[0049] The design principle of the rail position movement process in the present invention is as follows:

[0050] Due to the existence of the outer end face at the rail end, it comes into contact with the transverse wind during the cooling process, having a larger heat exchange surface compared with other parts of the rail. This not only causes non-uniformity in the overall hardened layer depth and hardness, but also easily generates bad structures such as bainite and martensite. Therefore, after the start of the second-stage air-blowing cooling, the rail end is pushed out of the air-blowing cooling device along the end face-rail body direction at a speed V0 of 1.5 - 2.5 mm / s. By means of heat conduction and convective heat transfer, the temperature of the rail end is made to be consistent with the heated part of the rail body near the rail end, controlling the maximum temperature difference between the two ≤20℃. The overall hardened layer depth is made uniform, and at the same time, the length of the hardened zone is increased and the length of the transition zone is shortened.

[0051] Through the above-mentioned end heat treatment process, the wear resistance and its uniformity of the rail end can be effectively improved.

[0052] The following embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0053]

Embodiment

[0054] In this embodiment, the method of the present invention is adopted to perform end heat treatment on U71Mn steel rails with a model specification of 50 kg / m. Then, the steel rails heat-treated in each embodiment and each comparative example are tested for the size of the hardened zone, metallographic structure, hardness of the tread surface, and hardness of the cross-section in accordance with the standard TB / T 2344.1-2020 "Steel Rails - Part 1: Steel Rails of 43 kg / m to 75 kg / m". The wear experiment is carried out on a hollow circular specimen with a thickness of 6 mm and a diameter of 36 mm. Samples are taken at the tread hardened layer, and the experiment is carried out under a dry friction environment with a test load of 170 kgf and a slip of 10% for 50,000 pairs of abrasions.

[0055] The main process parameters of the end heat treatment of the steel rails in each embodiment and comparative example are shown in Table 1. The temperatures of the rail end and the heated part of the rail body and the temperature difference between the two after the end heat treatment of the steel rails in each embodiment and comparative example are shown in Table 2. The size and structure of the hardened zone of the steel rails in each embodiment and comparative example are shown in Table 3. The hardness of the hardened zone and the weight loss due to wear of the steel rails in each embodiment and comparative example are shown in Table 4.

[0056] Table 1 Main process parameters of the end heat treatment of steel rails

[0057]

[0058] Table 2 Temperatures of the rail end and the heated part of the rail body and the temperature difference between the two after the end heat treatment of steel rails

[0059]

[0060] Table 3 Size and structure of the hardened zone of steel rails

[0061]

[0062] Table 4 Hardness of the hardened zone and weight loss due to wear of steel rails

[0063]

[0064] It can be seen from the experimental results that the increase in induction frequency will lead to a decrease in the hardenability depth, resulting in a reduction in the overall hardened layer depth. It is easy to appear bad bainite structure at a large cooling rate, resulting in a sudden change in hardness. Through the two-stage air-blowing cooling method, the hardness can be significantly increased, realizing the gradient distribution of the hardened layer and the refinement of the structure. After combining the adjustment of the rail position (displacement operation), the overall hardened layer depth is more uniform, the length of the hardened zone is increased, and the length of the transition zone is shortened.

[0065] Conclusion: After adopting the optimized end heat treatment process of the present invention, the wear resistance of the steel rails is significantly improved. The weight loss due to wear is reduced by about 20% under the same conditions, and its overall uniformity is good, which is conducive to improving the good and lasting use performance of the service steel rails during the continuous wear process.

[0066] The heat treatment method for improving the wear resistance and uniformity of the rail end according to the present invention can significantly improve the hardness and wear resistance at the connection of the rail end compared with the conventional rail heat treatment method. Moreover, the heat treatment performance of the rail end has a good transition with the hot-rolled state performance of the rail body. At the same time, the uniformity is good and the plastic toughness is not lost, which can effectively improve the service life of the rail, reduce wear, and is applicable to the heavy-duty transportation rails on special non-welded sections such as mines.

[0067] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered within the protection scope of the present invention.

Claims

1. A heat treatment method for improving the wear resistance and uniformity of the rail end, characterized in that, The end heat treatment process of the rail includes an induction heating process, a jet air cooling process, and a rail position adjustment process; specifically as follows: 1) Induction heating process: The surface heating temperature of the rail head is greater than 850 °C. The end of the rail is pushed into the induction heating device. The induction coil of the induction heating device is connected to an intermediate frequency alternating current of 1.0 - 2.0 kHz. After heating for 24 - 30 s, it reaches the austenite homogenization temperature of 900 - 930 °C; 2) Jet air cooling process: The rail end heated to the austenite homogenization temperature is pushed into the jet air cooling device within 10 s, and jet air cooling is carried out in two stages; In the first stage of jet air cooling, it is cooled at a cooling rate of 7 - 9 °C / s to 650 - 700 °C, and after stopping the jet air, it is maintained for more than 10 s; In the second stage of jet air cooling, it is cooled at a cooling rate of 10 - 12 °C / s to 450 - 500 °C. After stopping the jet air, the rail end is sent to the cooling bed for air cooling and tempered using the waste heat; 3) Rail position adjustment process: After the start of the second stage of jet air cooling in process 2), the rail end is pushed out of the jet air cooling device at a speed of 1.5 - 2.5 mm / s. By means of heat conduction and convective heat transfer, the temperature of the rail end and the heated part of the rail body near the rail end tends to be consistent, and the maximum temperature difference between the two is controlled to be ≤20 °C.

2. The heat treatment method for improving the wear resistance and uniformity of the rail end according to claim 1, characterized in that, During the induction heating process, the length of the rail end pushed into the induction heating device is 110 - 120 mm.

3. A heat treatment method for improving the wear resistance and uniformity of the rail end according to claim 1, characterized in that, During the induction heating process, the induction coil of the induction heating device is connected to an intermediate frequency alternating current of 1.0 - 1.5 kHz.

4. A heat treatment method for improving the wear resistance and uniformity of the rail end according to claim 1, characterized in that, The chemical elements of the rail are by weight percentage: C: 0.70% - 0.75%, Si: 0.40% - 0.60%, Mn: 0.90% - 1.10%, P ≤ 0.015%, S ≤ 0.010%, and the balance is Fe and unavoidable impurities.

5. A heat treatment method for improving the wear resistance and uniformity of the rail end according to claim 1, characterized in that, The production process of the rail includes vacuum smelting, continuous casting, heating, high-pressure water descaling, rolling, cooling bed cooling, straightening, and end heat treatment; After straightening, flaw detection inspection is carried out, and after passing, end heat treatment is carried out.

6. The heat treatment method for improving the wear resistance and uniformity of the rail end according to claim 1, characterized in that, The microstructure of the surface hardened layer at the rail end after end heat treatment is: the surface layer is sorbite structure, and the inner layer is pearlite structure.

7. A heat treatment method for improving the wear resistance and uniformity of the rail end according to claim 1, characterized in that, After end heat treatment, the depth of the hardened layer on the tread of the rail end is ≥18 mm; the length of the stable hardened zone is ≥90 mm; the length of the transition zone is ≤25 mm; the hardness of the tread of the rail end is ≥350 HB; the hardness of the rail end cross-section decreases stepwise from the surface to the core within the range of 370 - 280 HV.

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