Turnout steel rail with low rail bottom center residual stress and production method thereof
By combining online heat treatment and asymmetric accelerated cooling with straightening, the problem of uneven residual stress at the center of the rail base of turnout rails was solved, resulting in longer service life and safety, and simplifying the production process for large-scale promotion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
- Filing Date
- 2026-02-27
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies are insufficient to achieve a uniform reduction of residual stress at the center of the rail base in turnout rails, resulting in a reduced service life of the rails. Furthermore, existing methods are complex and difficult to promote on a large scale or guarantee consistent performance.
An online heat treatment process is adopted to perform asymmetric accelerated cooling on the rolled rails, combined with straightening. Specifically, different accelerated cooling rates are used on the long and short rail bases, and air cooling is performed after accelerated cooling to control the residual stress at the center of the rail base.
This method achieves a uniform reduction in residual stress at the center of the rail base of turnout rails, improving the service life and safety of the rails, while simplifying the production process and facilitating large-scale application.
Smart Images
Figure CN122012899A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of rail production technology, specifically to a turnout rail with low residual stress at the center of the rail base and its production method. Background Technology
[0002] Globally, with the rapid economic development of various countries, railway construction has entered a new peak period. Train speeds and load capacities, as well as the volume and frequency of train services, have all increased significantly. This has made the operating conditions of railway tracks more demanding and has also placed higher requirements on the quality of steel rails, a crucial component of railway tracks.
[0003] Turnout rails, as the core material of turnouts—a crucial component of railway tracks—directly affect the safety and stability of train operation. Furthermore, turnout rails typically require assembly by specialized manufacturers before being used on railways. Therefore, the performance and service life of turnout rails have always been a key focus in the railway industry. Performance requirements for turnout rails are gradually increasing, and the scope of performance attention is expanding. For example, residual stress at the rail base center, due to its impact on rail service life, has become a new focus for domestic and international rail manufacturers in improving the performance of turnout rails.
[0004] In recent years, domestic and international rail manufacturers have primarily employed methods such as straightening and constrained heat treatment to reduce residual stress at the center of the rail base. These methods control the residual stress at the center of the final rail product by applying external forces during production, thereby achieving lower residual stress test results in finished product inspection. The relevant patented technologies for controlling residual stress in rails are as follows: Patent CN201610479176.9 – "A Method for Reducing Residual Stress in Rails and the Obtained Rails and Their Applications" discloses a method for reducing residual stress in rails. This method involves sequentially subjecting the center of the rail head tread, both sides of the rail head, and the center of the rail base of the rolled rail to accelerated cooling, slow cooling, and air cooling. The accelerated cooling starts at 650-950℃ with a cooling rate of 2-8℃ / s and ends at 400-600℃. The slow cooling starts at 0.1-1.5℃ / s and ends at 180-300℃. During the heat treatment process, full-process straightening is performed to control straightness and torsion. Straightening is then performed after heat treatment. The residual stress in the rails obtained by this patent is significantly reduced compared to comparative examples and is suitable for high-speed railways. However, the rail production method described in this patent is only applicable to rails with symmetrical cross-sections. Furthermore, its method of controlling rail straightness through constrained heat treatment and straightening can only control the residual stress value of the final product. This can lead to uneven distribution of residual stress in areas outside the rail base center, such as the rail base corners, causing stress concentration during rail service and ultimately reducing the rail's service life. Simultaneously, the constrained heat treatment method requires highly specialized equipment and skilled personnel, and is prone to surface defects such as scratches on the rail surface, making large-scale adoption difficult.
[0005] Patent CN202310397360.9, entitled "Preparation Method of Low Residual Stress Corrosion-Resistant Rail at Rail Bottom," discloses a method for preparing a low residual stress corrosion-resistant rail at rail bottom. This method includes cooling, straightening, heating, and straightening the rolled rail. It claims to achieve a longitudinal residual stress at the center of the rail bottom ≤150MPa, with a residual stress fluctuation range ≤30MPa, while also improving the rail's corrosion resistance. However, the method described in this patent is complex and difficult to implement in practice. Furthermore, the repeated heating, cooling, and straightening processes can easily cause unpredictable changes in the mechanical properties of the rail base material, making this patented method unsuitable for use on turnout rails operating in harsh environments.
[0006] Patent CN 20121059.0752.9 – "A Heat Treatment Method for Turnout Rails and Turnout Rails" discloses a heat treatment method for turnout rails. This method includes accelerating the cooling of turnout rails with a rail head tread temperature of 650-900℃ to obtain a turnout rail with a full pearlitic microstructure. The accelerated cooling rate of the working side of the rail head is higher than that of the non-working side. The method also includes producing turnout rails with a working side having a hardness 1-3 HRC higher and a tensile strength 20-50 MPa higher than the non-working side. However, this invention employs a technique to avoid the risk of abnormal microstructure in the rail when the cooling rates on both sides of the rail head are the same. This results in turnout rails with inconsistent hardness and strength on both sides of the rail head, which is insufficient to meet the high performance consistency requirements in current turnout manufacturing and cannot be widely applied in actual turnout rail production.
[0007] Patent CN 202411097828.3 – “A Hypoeutectoid Turnout Rail for High-Altitude Cold Regions and its Heat Treatment Production Method” discloses a method for producing hypoeutectoid turnout rails for high-altitude cold regions. This patent uses steel billets with a C content of 0.5-0.7%, 0.25%≤Cr+V≤0.50%, Cu≥2.5% or Ni≤3.5% to heat-roll the turnout rails. An online heat treatment device is used, employing a multi-stage heat treatment and step-by-step cooling process to cool the rails to 450-550℃ before cooling them to room temperature. After straightening and processing, the resulting turnout rails are manufactured for high-altitude cold regions. The tensile strength of these turnout rails is 1105-1212 MPa, the elongation is 12-18%, and the surface hardness is 320-360 HB. However, the online heat treatment production method described in the patent uses four different processes in the accelerated cooling stage, which has high requirements for equipment, personnel and operation level, making production organization difficult. Moreover, the produced hypoeutectoid turnout rails have low strength and hardness, making it difficult to promote and apply them on a large scale in domestic and foreign markets.
[0008] In summary, most of the currently published patents related to reducing residual stress in rails employ constrained heat treatment combined with straightening or multiple straightening processes to control the residual stress at the rail base center. While this method can reduce the measured residual stress value at the rail base center of the final rail product, its production process is complex, and the straightening process can easily lead to uneven distribution of residual stress, which in turn reduces the service life of the rail. Furthermore, most of the currently published patents related to improving the performance of turnout rails using online heat treatment can only differentiate the performance of the working and non-working sides of the turnout rail, failing to achieve uniform performance on both sides through technical means. Therefore, it is difficult to ensure stable service performance of turnout rails during the turnout manufacturing process and online service. Simultaneously, existing rail production technologies and equipment for controlling residual stress are developed for symmetrical cross-section rails, making them difficult to apply to asymmetrical cross-section turnout rails. Significant shortcomings remain in the exploration of production methods for turnout rails with low residual stress at the rail base center. Summary of the Invention
[0009] To overcome the aforementioned defects of existing rails, this invention provides a turnout rail with low residual stress at the center of the rail base and its manufacturing method.
[0010] To achieve the above objectives, the present invention adopts the following technical solution.
[0011] According to a first aspect of the present invention, a method for producing a turnout rail with low residual stress at the center of the rail base is provided, comprising: sequentially subjecting the rolled rail to online heat treatment and straightening, wherein the online heat treatment includes: Accelerated cooling stage: When the temperature of the top surface of the rolled rail is between 740 and 880°C, the bottom of the long leg side rail and the bottom of the short leg side rail are accelerated to 450 to 550°C / s. The accelerated cooling rate of the bottom of the long leg side rail is 1.5 to 2.0°C / s, and the accelerated cooling rate of the bottom of the short leg side rail is 1.8 to 2.5°C / s. The accelerated cooling rate of the bottom of the short leg side rail is higher than that of the bottom of the long leg side rail. Air cooling stage: The rails that have undergone accelerated cooling stage are air cooled to room temperature.
[0012] As a further implementation, the difference between the accelerated cooling rate of the short-leg side rail bottom and the accelerated cooling rate of the long-leg side rail bottom is 0.3~0.5℃ / s.
[0013] As a further implementation method, during the accelerated cooling stage, when the temperature of the top surface of the rolled rail is between 740 and 880°C, the top surface of the rolled rail and both sides of the rail head are accelerated to 450 to 550°C / s, wherein the accelerated cooling rate of the top surface is 1.5 to 2.5°C / s, and the accelerated cooling rate of both sides of the rail head is 2.0 to 3.0°C / s.
[0014] As a further implementation, the cooling medium used in the accelerated cooling stage is compressed air and / or water mist.
[0015] As a further implementation method, the air cooling stage is carried out by placing the rails on a cooling bed.
[0016] As a further embodiment, the production method further includes, prior to online heat treatment, sequentially performing converter smelting, LF furnace refining, RH vacuum treatment, continuous casting, and rolling.
[0017] As a further implementation method, a horizontal-vertical composite straightening machine is used for straightening.
[0018] As a further embodiment, the chemical composition of the turnout rail, by weight percentage, is: C: 0.70~0.90%, Si: 0.15~0.80%, Mn: 0.75~1.20%, Cr: 0.01~0.20%, V: 0.001~0.030%, P: 0.005~0.015%, S: 0.005~0.015%, with the balance being Fe and unavoidable impurities.
[0019] According to a second aspect of the present invention, a turnout rail with low residual stress at the center of the rail base is provided, which is obtained by the above-described production method.
[0020] As a further implementation method, the residual stress at the center of the rail base after straightening of the turnout rail is 120~150MPa, the residual stress at the bottom of the long leg side rail is 90~130MPa, the residual stress at the bottom of the short leg side rail is 80~120MPa, the tensile strength of the turnout rail is ≥1200MPa, the elongation after fracture is ≥10%, the surface hardness is ≥340HB, and the microstructure of the entire cross section of the rail is pearlite.
[0021] By adopting the above technical solution, the present invention can achieve the following technical effects: This invention optimizes the online heat treatment process, enabling the production of turnout rails with low residual stress at the rail base center without restricting other rail manufacturing processes. The resulting turnout rails, after straightening, exhibit a residual stress of 120-150 MPa at the rail base center, 90-130 MPa on the long-leg side, and 80-120 MPa on the short-leg side. Even before straightening, the obtained turnout rails have lower residual stress than similar rails, resulting in a more uniform distribution of residual stress. In addition to lower residual stress values after straightening, the reduced stress concentration at the rail base contributes to extending the rail's service life and improving the safety of the turnout rails during service.
[0022] Furthermore, the production method provided by this invention is simple and easy to operate, which is conducive to large-scale promotion and application. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1 A schematic diagram showing the location of the cooling medium spraying during the accelerated cooling stage of the turnout rails. Figure 2 This is a schematic diagram showing the location for inspecting residual stress at the bottom of the turnout rail. Detailed Implementation
[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.
[0026] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0027] This invention proposes a method for producing turnout rails with low residual stress at the center of the rail base, comprising: sequentially performing online heat treatment and straightening on the rolled rail, wherein the online heat treatment includes: an accelerated cooling stage: when the temperature of the top surface of the rolled rail is between 740 and 880°C, the long leg side rail base and the short leg side rail base of the rolled rail are accelerated to 450 to 550°C / s, wherein the accelerated cooling rate of the long leg side rail base is 1.5 to 2.0°C / s, the accelerated cooling rate of the short leg side rail base is 1.8 to 2.5°C / s, and the accelerated cooling rate of the short leg side rail base is higher than that of the long leg side rail base; an air cooling stage: the rail cooled in the accelerated cooling stage is air cooled to room temperature.
[0028] The inventors of this invention discovered through extensive research that: ① Only when the starting temperature of accelerated cooling of the rail (i.e., the center surface temperature of the rail top after rolling) is between 740 and 880℃, and the accelerated cooling rates of the long-leg side rail bottom and the short-leg side rail bottom are 1.5~2.0℃ / s and 1.8~2.5℃ / s respectively, and the accelerated cooling rate of the short-leg side rail bottom is higher than that of the long-leg side rail bottom, can it be ensured that the rail bottom of the asymmetrical turnout rail is uniformly cooled during the heat treatment process, the deformation distribution difference between the long-leg side and the short-leg side rail bottom during the cooling process is small, the residual stress at the center of the rail bottom is controlled to be at a low level, and the other mechanical properties and microstructure of the rail meet the requirements. ② When the rail cools to 450~550℃, the pearlite transformation inside the rail head is completed. Continuing to accelerate cooling will not improve the rail performance. On the contrary, it will greatly increase the possibility of abnormal structures such as martensite appearing on the rail surface. Therefore, at this temperature, accelerated cooling should be stopped. ③ After the accelerated cooling of the rails is stopped, in order to reduce the deformation and residual stress changes of the rails during the subsequent cooling process, air cooling is used to continue cooling the rails to room temperature without any other heat preservation measures.
[0029] The accelerated cooling start temperature can typically, but not limited to, be set to 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, or 880℃; the accelerated cooling stop temperature can typically, but not limited to, be set to 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, or 5... 30℃, 540℃, 550℃; the accelerated cooling rate of the long-leg side rail bottom can typically, but not limited to, be set to 1.5℃ / s, 1.6℃ / s, 1.7℃ / s, 1.8℃ / s, 1.9℃ / s, 2.0℃ / s; the accelerated cooling rate of the short-leg side rail bottom can typically, but not limited to, be set to 1.8℃ / s, 1.9℃ / s, 2.0℃ / s, 2.1℃ / s, 2.2℃ / s, 2.3℃ / s, 2.4℃ / s, 2.5℃ / s.
[0030] In some embodiments, the difference between the accelerated cooling rate of the short-leg side rail base and the accelerated cooling rate of the long-leg side rail base is 0.3~0.5℃ / s. The difference between the accelerated cooling rate of the short-leg side rail base and the accelerated cooling rate of the long-leg side rail base can typically, but not limitedly, be set to 0.3℃ / s, 0.35℃ / s, 0.4℃ / s, 0.45℃ / s, or 0.5℃ / s.
[0031] In some embodiments, during the accelerated cooling stage, when the temperature of the top surface of the rolled rail is between 740 and 880°C, the top surface of the rolled rail and both sides of the rail head are accelerated to 450 to 550°C / s, wherein the accelerated cooling rate of the top surface is 1.5 to 2.5°C / s and the accelerated cooling rate of both sides of the rail head is 2.0 to 3.0°C / s. The accelerated cooling rate of the rail top surface can typically, but not limited to, be set to 1.5℃ / s, 1.6℃ / s, 1.7℃ / s, 1.8℃ / s, 1.9℃ / s, 2.0℃ / s, 2.1℃ / s, 2.2℃ / s, 2.3℃ / s, 2.4℃ / s, or 2.5℃ / s; the accelerated cooling rate of the two sides of the rail head can typically, but not limited to, be set to 2.0℃ / s, 2.1℃ / s, 2.2℃ / s, 2.3℃ / s, 2.4℃ / s, 2.5℃ / s, 2.6℃ / s, 2.7℃ / s, 2.8℃ / s, 2.9℃ / s, or 3.0℃ / s.
[0032] The production method described in this invention is applicable to asymmetric cross-section turnout rails. Asymmetric cross-section turnout rails have a short leg side and a long leg side, and the rail head correspondingly has a short leg side and a long leg side, and the rail base correspondingly has a short leg side rail base and a long leg side rail base. In this invention, accelerated cooling is achieved by spraying a cooling medium onto the corresponding parts. Specifically, as... Figure 1 As shown, accelerated cooling of these parts is achieved by spraying cooling medium onto the top surface of the rail, both sides of the rail head (i.e., the short leg side and the long leg side of the rail head), the bottom of the long leg side rail, and the bottom of the short leg side rail.
[0033] In some embodiments, the cooling medium used in the accelerated cooling phase is compressed air and / or water mist.
[0034] In some embodiments, the air-cooling stage is performed by placing the rails on a cooling bed.
[0035] In some embodiments, prior to online heat treatment, the production method further includes: sequentially performing converter smelting, LF furnace refining, RH vacuum treatment, continuous casting, and rolling. After straightening, the production method further includes: machining. That is, the production method sequentially includes: converter smelting, LF furnace refining, RH vacuum treatment, continuous casting, rolling, online heat treatment, straightening, and machining.
[0036] For example, the complete manufacturing process of turnout rails can be as follows: using low-sulfur vanadium-containing molten steel, smelting it in a converter or electric furnace, refining it with LF, vacuum treating it with RH, and continuously casting it with large billet protection to obtain steel billets. After the steel billets are heated in a heating furnace, they undergo high-pressure water descaling before rolling, rolling on a universal rolling mill, online heat treatment of the rails, room temperature and air cooling on a walking beam cooling bed, flat and vertical composite straightening, rail specification inspection, processing line treatment, surface inspection, and warehousing.
[0037] In some embodiments, the chemical composition of the turnout rail, by weight percentage, is: C: 0.70~0.90%, Si: 0.15~0.80%, Mn: 0.75~1.20%, Cr: 0.01~0.20%, V: 0.001~0.030%, P: 0.005~0.015%, S: 0.005~0.015%, with the balance being Fe and unavoidable impurities.
[0038] The following details the reasons for limiting the content of the main chemical elements in the rails of this invention.
[0039] Carbon (C) is a key element in the formation of pearlite. Through the formation of a lamellar structure of cementite (Fe3C) and ferrite, it directly determines the lamellar spacing and cementite thickness, thus affecting strength and hardness. When the C content is <0.70%, the proportion of pearlite in the rail is insufficient, resulting in low strength and hardness, affecting wear resistance. When the C content is >0.90%, the cementite lamellars thicken, the pearlite becomes brittle, the elongation after fracture decreases, increasing the risk of rail fracture and affecting the rail's fatigue performance and safety. Therefore, the C content in this invention is limited to 0.70~0.90%.
[0040] As a solid solution strengthening element, silicon (Si) can improve the strength of the ferrite matrix, reduce oxide inclusions in steel, and optimize the pearlite microstructure. When the Si content is <0.15%, its solid solution strengthening effect is insufficient; when the Si content is >0.80%, it increases carbon activity, promotes premature precipitation of vitamin C, affects the effect of subsequent heat treatment, and reduces weldability. Therefore, the Si content in this invention is limited to 0.15~0.80%.
[0041] Mn significantly improves the hardenability of steel by lowering the austenite transformation temperature and increasing undercooling, and can refine the pearlite lamellar spacing, thereby enhancing the mechanical properties of rails. When the Mn content is <0.75%, insufficient pearlite refinement and reduced hardenability result in insufficient improvement in the strength and hardness of the steel. When the Mn content is >1.20%, the risk of grain coarsening increases, which may reduce the toughness and plasticity of the rail, and bainite or martensite may form in the Mn segregation zone, affecting weldability. Therefore, the Mn content in this invention is limited to 0.75~1.20%.
[0042] As a carbide-forming element, Cr can form various carbides with carbon in steel, while also improving hardenability, strength, and wear resistance of the rail. When the Cr content is <0.01%, hardenability is insufficient, and the strengthening effect is not obvious; when the Cr content is >0.20%, a σ phase may form, causing a sharp decrease in impact toughness and affecting the safe use of the rail. Therefore, the Cr content in this invention is limited to 0.01~0.20%.
[0043] V (V) inhibits austenite grain growth and refines pearlite lamellar spacing by forming carbonitrides, significantly improving the strength and toughness of rails. When the V content is <0.001%, the grain refinement effect is insufficient, the pearlite lamellar spacing is large, and the strength and wear resistance of the rail decrease. When the V content is >0.030%, excessive carbonitride precipitation may reduce plasticity and toughness and affect the processing performance of the rail. Therefore, the V content in this invention is limited to 0.001~0.030%.
[0044] Phosphorus (P) is a harmful element that is difficult to completely remove from steel. It tends to segregate at grain boundaries, reducing the toughness of the rail. Therefore, the P content in this invention must be strictly controlled below 0.015% to ensure the impact toughness of the rail.
[0045] Sulfide (S) readily forms MnS inclusions in steel, affecting the fatigue performance and wear resistance of rails. Therefore, the S content in this invention needs to be controlled below 0.015% to reduce the size and quantity of sulfide inclusions.
[0046] This invention also proposes a turnout rail with low residual stress at the center of the rail base, which is obtained using the above-described production method. After straightening, the resulting turnout rail has a residual stress of 120-150 MPa at the center of the rail base, 90-130 MPa on the long-leg side, and 80-120 MPa on the short-leg side. The inspection locations for the residual stress at the center of the rail base, the long-leg side, and the short-leg side are as follows... Figure 2 As shown, the obtained turnout rail has a tensile strength ≥1200MPa, elongation after fracture ≥10%, surface hardness ≥340HB, and the microstructure of the entire rail section is pearlite.
[0047] In summary, this invention, through optimization of the online heat treatment process and combined with a redesigned content of key reinforcing elements in the rail, achieves turnout rails with low residual stress at the rail base center without restricting other rail production processes. The resulting turnout rails exhibit lower residual stress even before straightening compared to similar rails, with a more uniform distribution of residual stress. In addition to lower post-straightening residual stress values, the reduced stress concentration at the rail base contributes to extending the rail's service life and improving the safety of the turnout rails during service. Furthermore, the production method provided by this invention is simple, easy to operate, and conducive to large-scale application.
[0048] The present invention will be described in detail below through embodiments, but the scope of the present invention is not limited thereto.
[0049] Examples 1-3 and Comparative Examples 1-3 use steel rails with chemical compositions of A, B, and C, respectively, as shown in Table 1.
[0050] Table 1
[0051] The balance is Fe and unavoidable impurities.
[0052] Examples 1-3 and Comparative Examples 1-3 used chemical components A, B, and C, respectively. The process comparisons are shown in Table 2. The differences between the remaining processes of the examples and comparative examples are negligible.
[0053] Table 2
[0054] The tensile properties, surface hardness, microstructure, and cross-sectional hardness of Examples 1-3 and Comparative Examples 1-3 are shown in Table 3. This invention measures the tensile strength and elongation after fracture of rails according to GB / T 228.1 "Metallic materials, tensile testing—Part 1: Test method at room temperature"; measures the surface hardness of rails using the Brinell hardness test method as specified in GB / T 231.1 "Metallic materials, Brinell hardness test—Part 1: Test method"; determines the microstructure of rails according to TB / T 2344.2-2020 "Rails—Part 2: Asymmetric section rails for turnouts" and GB / T 13298-2015 "Metallic materials, microstructure test method"; and examines the residual stress at the bottom of rails according to TB / T 2344.1-2020 "Rails—Part 1: 43kg / m~75kg / m rails" and TB / T 2344.2-2020 "Rails—Part 2: Asymmetric section rails for turnouts".
[0055] Table 3
[0056] Comparing the embodiments and comparative examples, it can be seen that, under the same process conditions, the online heat treatment process of the rail significantly affects the residual stress at the center of the rail base. The rail obtained using the method described in this invention has lower residual stress at the center of the rail base and more stable microstructure and other mechanical properties compared to the comparative example.
[0057] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Those skilled in the art should understand that various modifications can be made to the present invention without departing from the spirit and scope thereof. All such modifications fall within the protection scope of the present invention.
Claims
1. A method for producing turnout rails with low residual stress at the center of the rail base, characterized in that, include: The rolled rails undergo sequential online heat treatment and straightening, with the online heat treatment including: Accelerated cooling stage: When the temperature of the top surface of the rolled rail is between 740 and 880°C, the bottom of the long leg side rail and the bottom of the short leg side rail are accelerated to 450 to 550°C / s. The accelerated cooling rate of the bottom of the long leg side rail is 1.5 to 2.0°C / s, and the accelerated cooling rate of the bottom of the short leg side rail is 1.8 to 2.5°C / s. The accelerated cooling rate of the bottom of the short leg side rail is higher than that of the bottom of the long leg side rail. Air cooling stage: The rails that have undergone accelerated cooling stage are air cooled to room temperature.
2. The production method according to claim 1, characterized in that, The difference between the accelerated cooling rate of the short-leg side rail and the accelerated cooling rate of the long-leg side rail is 0.3~0.5℃ / s.
3. The production method according to claim 1, characterized in that, During the accelerated cooling stage, when the temperature of the top surface of the rolled rail is between 740 and 880°C, the top surface and both sides of the rail head of the rolled rail are accelerated to 450 to 550°C / s. The accelerated cooling rate of the top surface is 1.5 to 2.5°C / s, and the accelerated cooling rate of both sides of the rail head is 2.0 to 3.0°C / s.
4. The production method according to claim 1, characterized in that, The cooling medium used in the accelerated cooling stage is compressed air and / or water mist.
5. The production method according to claim 1, characterized in that, The air-cooling stage is carried out by placing the rails on a cooling bed.
6. The production method according to claim 1, characterized in that, Prior to online heat treatment, the production method further includes: sequentially performing converter smelting, LF furnace refining, RH vacuum treatment, continuous casting, and rolling.
7. The production method according to claim 1, characterized in that, A combined horizontal and vertical straightening machine was used for straightening.
8. The production method according to claim 1, characterized in that, The chemical composition of the turnout rail, by weight percentage, is as follows: C: 0.70~0.90%, Si: 0.15~0.80%, Mn: 0.75~1.20%, Cr: 0.01~0.20%, V: 0.001~0.030%, P: 0.005~0.015%, S: 0.005~0.015%, with the balance being Fe and unavoidable impurities.
9. A turnout rail with low residual stress at the center of the rail base, characterized in that, Obtained by the production method according to any one of claims 1-8.
10. The turnout rail according to claim 9, characterized in that, After straightening, the residual stress at the center of the rail base of the turnout rail is 120~150MPa, the residual stress at the bottom of the long leg side rail is 90~130MPa, and the residual stress at the bottom of the short leg side rail is 80~120MPa. The tensile strength of the turnout rail is ≥1200MPa, the elongation after fracture is ≥10%, the surface hardness is ≥340HB, and the microstructure of the entire rail section is pearlite.