A method for controlling lateral bending of asymmetric large-section rails during heat treatment

Abstract

This invention discloses a method for controlling lateral bending during the heat treatment of asymmetric large-section rails, comprising: S1. Dividing the rail base of the asymmetric large-section rail into three zones, I, II, and III, and accelerating the cooling of the rail base throughout the entire heat treatment process, wherein the cooling rate of zone I is 1.5–3.5℃ / s, the cooling rate of zone II is 3–5.5℃ / s, and the cooling rate of zone III is 1–3℃ / s; S2. When the rail exits the cooling unit, T II Controlled at 380-420℃, T I Controlled at 365~395℃, T III The temperature should be controlled between 375 and 405℃, and |T II -T I |≤25℃、|T II -T III |≤15℃、|T III -T I |≤20℃. The side bending of the rail after exiting the heat treatment unit of this invention is ≤0.8mm / m, which effectively avoids the situation where the rail side bending is so severe that it cannot pass through the roller conveyor normally or hits the side baffle of the roller conveyor.

Description

[0001] The present application relates to the technical field of steel heat treatment, in particular to a method for controlling side bending of asymmetric large-section steel rail in a heat treatment process. BACKGROUND

[0002] Turnouts are important equipment for realizing railway track conversion, and have the characteristics of complex structure, short service life, and large maintenance and repair investment, so turnouts, curves, and joints are collectively known as the three weak links of railway tracks. Asymmetric large-section steel rails (referred to as AT steel rails) have the characteristics of strong integrity, large rigidity, good smoothness, and high safety, and are widely used in the manufacture of turnout rails. With the development of the railway transportation industry, the performance requirements for turnouts are more stringent, and more and more turnout rails need to be made of AT steel rails after heat treatment.

[0003] The biggest difference between AT steel rails and ordinary steel rails is that the section is large (the weight per meter reaches 82 kg), and the section is asymmetric (one side leg is short and one side leg is long), the short leg length is 62 mm, and the long leg length is 90 mm. This results in that when the AT steel rail is heat treated, because of the asymmetry of the section, there is a difference in heat capacity on both sides of the steel rail, and the cooling speed of each part of the steel rail is very different. The long leg side has a large specific surface area, and the early cooling speed is fast. After the steel rail exits the heat treatment unit, it appears as a full-length side bending in the length direction. When the side bending is serious (up to 2-3 mm / m), the steel rail cannot normally pass through the roller and proceed forward, and the end of the steel rail may even hit the side baffle of the roller, thereby causing the production to stop or causing a dangerous accident.

[0004] The patent "Steel rail online heat treatment flatness control method" (CN 109182715 B) provides a steel rail online heat treatment flatness control method, which specifically includes two steps of bending treatment and heat treatment. By controlling the acceleration cooling time and the flow ratio of the cooling medium, and the temperature of the steel rail after heat treatment, the flatness of the steel rail after heat treatment is controlled to be 0.9-1.2 mm / 1.5 m. The patent "Production control method for improving the flatness of online heat treated steel rails after quenching" (CN 112877531 A) provides a production control method for improving the flatness of heat treated steel rails after quenching. This method controls the cooling intensity and temperature difference of the rail head and the rail bottom to ensure that the overall heat treated steel rail is basically flat, and the rail end has a certain degree of warping towards the rail head. The height of the 100m long steel rail end upwarping is within the range of 19mm. Both of these methods are only suitable for flatness control of symmetric section steel rails, and cannot effectively control the side bending phenomenon of asymmetric large-section AT steel rails in the heat treatment process.

[0005] The patent "Heat treatment method of switch rail" (CN 103898303 B) provides a heat treatment method of switch rail, which comprises accelerating cooling of the switch rail with a rail head tread temperature of 650-900 DEG C to obtain a full pearlite structure switch rail, and the acceleration cooling speed of the working side of the rail head of the switch rail is higher than that of the non-working side of the rail head of the switch rail. The method does not consider the asymmetric characteristics of the rail bottom of the switch rail (one side is short, and the other side is long), and the cooling speed of the two sides of the rail bottom is different after the rail leaves the heat treatment unit, so that the rail will be bent on the side.

[0006] Therefore, it is necessary to develop a control method for side bending in the heat treatment process of asymmetric large-section rails, effectively solve the problem of serious side bending in the heat treatment process of asymmetric large-section rails, avoid the situation that the rail cannot normally pass through the roller way or hit the side baffle of the roller way after leaving the heat treatment unit, and facilitate the safe and smooth production of the heat treatment process of asymmetric large-section rails. SUMMARY

[0007] The purpose of the present application is to solve the problems in the prior art, and provide a control method for side bending in the heat treatment process of asymmetric large-section rails, which can effectively solve the problem of serious side bending in the heat treatment process of asymmetric large-section rails, and avoid the situation that the rail cannot normally pass through the roller way or hit the side baffle of the roller way.

[0008] The technical scheme of the present application is as follows: a control method for side bending in the heat treatment process of asymmetric large-section rails, characterized by comprising the following steps:

[0009] S1. The rail bottom of the asymmetric large-section rail is divided into I, II and III regions, the II region is distributed in the middle part of the rail bottom, and the I region and the III region are respectively located on both sides of the II region, the II region is distributed from the vertical edge opposite the short leg side of the rail waist to the edge opposite the long leg side of the rail waist connected to the rail bottom, the I region is distributed from the boundary of the II region to the short leg side edge of the rail bottom, and the III region is distributed from the boundary of the II region to the long leg side edge of the rail bottom,

[0010] accelerating cooling of the rail bottom in the heat treatment unit, wherein the cooling speed of the I region is 1.5-3.5 DEG C / s, the cooling speed of the II region is 3-5.5 DEG C / s, and the cooling speed of the III region is 1-3 DEG C / s;

[0011] S2. The temperature at the 1 / 3 distance of the short leg side edge of the rail bottom from the central axis of the rail bottom is taken as the rail bottom short leg side temperature T I The temperature at the central axis of the rail bottom is taken as the rail bottom temperature T IIThe temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0012] When the rails exit the cooling unit, T II Controlled at 380-420℃, T I Controlled at 365~395℃, T III The temperature should be controlled between 375 and 405℃, and |T II -T I |≤25℃、|T II -T III |≤15℃、|T III -T I ≤20℃. That is, T II With T I The absolute value of the difference between them is ≤25℃, T II With T III The absolute value of the difference between them is ≤15℃, T III With T I The absolute value of the difference between them is ≤20℃.

[0013] Preferably, in step S1, the temperature at which the rail begins to be accelerated cooled in the heat treatment unit is 690–860°C.

[0014] Preferably, in step S1, the rail head and rail base of the rail are simultaneously accelerated and cooled in the heat treatment unit. The same cooling rate of 3-7°C / s is applied to both sides of the rail head, and the temperature at the center axis of the rail head tread is taken as the tread temperature T. IV T IV When the temperature drops to 430-525℃, the rail head stops accelerating cooling.

[0015] Furthermore, in step S1, the temperature at which the rail begins to be accelerated to cool in the heat treatment unit is 790–840°C.

[0016] Furthermore, in step S1, accelerated cooling begins simultaneously on both the rail head and the rail base within the heat treatment unit, with the same cooling rate of 5.5–6.5 °C / s applied to both sides of the rail head. IV When the temperature drops to 470-515℃, the rail head stops accelerating cooling.

[0017] Preferably, in step S1, the cooling rate of zone I is 2.9–3.3 °C / s, the cooling rate of zone II is 4.9–5.2 °C / s, and the cooling rate of zone III is 2.1–2.6 °C / s.

[0018] Preferably, in step S2, when the rail exits the cooling unit, T II Controlled at 405~413℃, T I Controlled at 389–391℃, T IIIThe temperature should be controlled between 395 and 402℃, and |T II -T I |≤25℃、|T II -T III |≤15℃、|T III -T I ≤20℃.

[0019] Preferably, it includes the following steps:

[0020] S1. The rail base of the asymmetric large-section rail is divided into three regions: I, II, and III. Region II is located in the middle of the rail base, with Regions I and III located on either side of Region II. Region II extends from the vertical edge directly opposite the short leg side of the rail web to the edge directly opposite the connection point between the long leg side of the rail web and the rail base. Region I extends from the boundary of Region II to the edge of the short leg side of the rail base. Region III extends from the boundary of Region II to the edge of the long leg side of the rail base.

[0021] The rail base undergoes accelerated cooling throughout the entire heat treatment process. The cooling rate is 3.3℃ / s in zone I, 5.2℃ / s in zone II, and 2.6℃ / s in zone III. The rail begins accelerated cooling at 840℃ within the heat treatment unit. Accelerated cooling begins simultaneously on both the rail head and the rail base, with the same cooling rate of 6.5℃ / s applied to both sides of the rail head. The temperature at the centerline of the rail head tread is defined as the tread temperature T. IV T IV The rail head stops accelerating cooling when the temperature drops to 513℃.

[0022] S2. The temperature at the centerline of the rail base in Zone II is taken as the rail base temperature T. II The temperature T on the short leg side of the rail is defined as the temperature at approximately 1 / 3 of the distance between the edge of the rail base and the centerline of the rail base on the short leg side of section I. I The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0023] When the rails exit the cooling unit, T II Controlled at 409℃, T I Controlled at 389℃, T III Control the temperature at 401℃.

[0024] Preferably, the lateral bending of the asymmetric large-section steel rail after exiting the heat treatment unit is ≤0.8mm / m.

[0025] The technical principle of this invention is as follows: The essence of rail heat treatment is an accelerated cooling process. When heat-treating symmetrical cross-section rails, because the left and right sides of the rail are symmetrical, after accelerated cooling and exiting the heat treatment unit, the temperature and cooling rate on both sides of the rail are essentially the same, thus preventing lateral bending. However, when heat-treating asymmetrical large-section rails, due to the asymmetry of the two sides, if conventional methods are used, the longer leg side of the rail base has a relatively smaller heat capacity and a larger specific surface area after exiting the heat treatment unit. The longer leg side cools faster than the shorter leg side, causing the rail to bend towards the longer leg side. Experimental research has shown that when the rail base area of ​​asymmetrical large-section rails is cooled in sections with different cooling rates, and the temperatures of the longer and shorter leg sides of the rail base, as well as the temperature difference between them, are controlled, the lateral bending phenomenon after exiting the heat treatment unit can be reduced or even eliminated.

[0026] Based on the different relative heat capacities of various regions at the bottom of asymmetric large-section rails, the cooling rate is 1.5–3.5℃ / s for the short leg side, 1–3℃ / s for the long leg side, and 3–5.5℃ / s for the center of the rail bottom. When the rails exit the heat treatment unit, the rail bottom temperature is controlled at 380–420℃, the short leg side temperature at 365–395℃, and the long leg side temperature at 375–405℃; the temperature difference between the short leg side and the rail bottom is less than 25℃, the temperature difference between the long leg side and the rail bottom is less than 15℃, and the temperature difference between the short leg side and the long leg side is less than 20℃. This ensures that the cooling rate difference between the two sides of the rail bottom is minimal after exiting the heat treatment unit, preventing severe lateral bending of the rail.

[0027] The same cooling rate of 3-7°C / s is applied to both sides of the rail head in this invention, and the temperature at the center axis of the rail head tread is taken as the tread temperature T. IV T IV When the temperature drops to 430-525℃, the rail head stops accelerating cooling. At this point, the pearlite transformation has been completed, resulting in a fine lamellar pearlite structure.

[0028] The beneficial effects of this invention are:

[0029] Compared with existing technologies, this invention proposes a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. The lateral bending of the rail after exiting the heat treatment unit is ≤0.8mm / m, which effectively avoids the situation where the rail is unable to pass through the roller conveyor normally or collides with the side baffle of the roller conveyor due to severe lateral bending. This is conducive to the safe and smooth operation of the heat treatment production process of asymmetric large-section rails. Moreover, this control method is convenient, efficient, highly operable, and easy to promote and apply. Attached Figure Description

[0030] Figure 1 This is a cross-sectional view of an asymmetric large-section rail. Detailed Implementation

[0031] To further understand the present invention, preferred embodiments are described below with reference to examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims. Unless otherwise specified, the pharmaceuticals used in the examples are commercially available products, and the methods used are conventional methods in the art.

[0032] The following specific embodiments will provide a more detailed description of the present invention.

[0033] This invention discloses a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. This method can be used to control lateral bending during the heat treatment of asymmetric large-section rails of any composition. To better understand this invention, the following embodiments further illustrate its content.

[0034] The rails produced by the method of this invention undergo accelerated cooling of the rail base throughout the entire heat treatment process, dividing the rail base of the asymmetric large-section rail into three regions: I, II, and III (e.g., Figure 1 As shown), Zone II is located in the middle of the rail bottom, with Zones I and III located on the left and right sides of Zone II, respectively. Zone II is located directly opposite the vertical edge from the short leg side of the rail web (i.e., Figure 1 The point directly opposite the edge where the long leg of the rail meets the bottom of the rail (i.e., the dotted line on the left side of the middle rail) is located. Figure 1 (The right side of the image shows a dashed line). Zone I is located from the boundary of Zone II to the edge of the short leg side of the rail base, and Zone III is located from the boundary of Zone II to the edge of the long leg side of the rail base. The cooling rate of Zone I is 1.5–3.5℃ / s, the cooling rate of Zone II is 3–5.5℃ / s, and the cooling rate of Zone III is 1–3℃ / s. When the rail exits the heat treatment unit, the rail base temperature is controlled at 380–420℃, the short leg side temperature is controlled at 365–395℃, and the long leg side temperature is controlled at 375–405℃. The temperature difference between the short leg side and the rail base is less than 25℃, the temperature difference between the long leg side and the rail base is less than 15℃, and the temperature difference between the short leg side and the long leg side is less than 20℃. The rail begins accelerated cooling in the heat treatment unit at a temperature of 690–860℃. The same cooling rate of 3–7℃ / s is applied to both sides of the rail head, and accelerated cooling stops when the rail head tread temperature drops to 430–525℃.

[0035] Example 1

[0036] This embodiment provides a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. The specific steps are as follows:

[0037] S1. Divide the bottom of the asymmetric large-section rail into three regions: I, II, and III (e.g., Figure 1As shown), the rail base undergoes accelerated cooling throughout the entire heat treatment process. The rail begins accelerated cooling at 695℃ within the heat treatment unit, with cooling rates of 1.6℃ / s in zone I, 3.2℃ / s in zone II, and 1.2℃ / s in zone III. Accelerated cooling begins simultaneously on both sides of the rail head. Figure 1 The same cooling rate of 3.3℃ / s is applied to both sides of the rail head, and the temperature at the center axis of the rail head tread is taken as the tread temperature T. IV T IV When the temperature drops to 439℃, the rail head stops accelerating cooling (in the heat treatment unit, rail head cooling and rail bottom cooling are controlled separately).

[0038] S2. The temperature at the point approximately 1 / 3 of the distance between the edge of the short-leg side rail base and the centerline of the rail base is defined as the short-leg side rail base temperature T. I The temperature at the centerline of the rail base is taken as the rail base temperature T. II The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0039] When the rails exit the cooling unit, T I Controlled at 369℃, T II Controlled at 386℃, T III Controlled at 378℃, and T II -T I =17℃≤25℃、T II -T III =8℃≤15℃、T III -T I =9℃≤20℃.

[0040] Example 2

[0041] This embodiment provides a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. The specific steps are as follows:

[0042] S1. Divide the bottom of the asymmetric large-section rail into three regions: I, II, and III (e.g., Figure 1 As shown), the rail base undergoes accelerated cooling throughout the entire heat treatment process. The rail begins accelerated cooling at 736℃ within the heat treatment unit, with cooling rates of 2.3℃ / s in zone I, 3.9℃ / s in zone II, and 1.7℃ / s in zone III. Accelerated cooling begins simultaneously on both sides of the rail head. Figure 1 The same cooling rate of 4.6℃ / s is applied to both sides of the rail head, and the temperature at the center axis of the rail head tread is taken as the tread temperature T. IV T IV The rail head stopped accelerating cooling when the temperature dropped to 451°C.

[0043] S2. The temperature at the point approximately 1 / 3 of the distance between the edge of the short-leg side rail base and the centerline of the rail base is defined as the short-leg side rail base temperature T. I The temperature at the centerline of the rail base is taken as the rail base temperature T. II The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0044] When the rails exit the cooling unit, T I Controlled at 372℃, T II Controlled at 391℃, T III Controlled at 383℃, and T II -T I =19℃≤25℃、T II -T III =8℃≤15℃、T III -T I =11℃≤20℃.

[0045] Example 3

[0046] This embodiment provides a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. The specific steps are as follows:

[0047] S1. Divide the bottom of the asymmetric large-section rail into three regions: I, II, and III (e.g., Figure 1 As shown), the rail base undergoes accelerated cooling throughout the entire heat treatment process. The rail begins accelerated cooling at 750℃ within the heat treatment unit, with cooling rates of 2.6℃ / s in zone I, 4.2℃ / s in zone II, and 1.9℃ / s in zone III. Accelerated cooling begins simultaneously on both sides of the rail head. Figure 1 The same cooling rate of 5.1℃ / s is applied to both sides of the rail head, and the temperature at the center axis of the rail head tread is taken as the tread temperature T. IV T IV The rail head stops accelerating cooling when it drops to 460°C.

[0048] S2. The temperature at the point approximately 1 / 3 of the distance between the edge of the short-leg side rail base and the centerline of the rail base is defined as the short-leg side rail base temperature T. I The temperature at the centerline of the rail base is taken as the rail base temperature T. II The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0049] When the rails exit the cooling unit, T I Controlled at 376℃, T IIControlled at 398℃, T III Controlled at 391℃, and T II -T I =22℃≤25℃、T II -T III =7℃≤15℃、T III -T I =15℃≤20℃.

[0050] Example 4

[0051] This embodiment provides a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. The specific steps are as follows:

[0052] S1. Divide the bottom of the asymmetric large-section rail into three regions: I, II, and III (e.g., Figure 1 As shown), the rail base undergoes accelerated cooling throughout the entire heat treatment process. The rail begins accelerated cooling at 858℃ within the heat treatment unit, with cooling rates of 3.5℃ / s in zone I, 5.5℃ / s in zone II, and 2.9℃ / s in zone III. Accelerated cooling begins simultaneously on both sides of the rail head. Figure 1 The same cooling rate of 6.9℃ / s is applied to both sides of the rail head, and the temperature at the center axis of the rail head tread is taken as the tread temperature T. IV T IV The rail head stops accelerating cooling when the temperature drops to 520°C.

[0053] S2. The temperature at the point approximately 1 / 3 of the distance between the edge of the short-leg side rail base and the centerline of the rail base is defined as the short-leg side rail base temperature T. I The temperature at the centerline of the rail base is taken as the rail base temperature T. II The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0054] When the rails exit the cooling unit, T I Controlled at 393℃, T II Controlled at 416℃, T III Controlled at 405℃, and T II -T I =23℃≤25℃、T II -T III =11℃≤15℃、T III -T I =12℃≤20℃.

[0055] Example 5

[0056] This embodiment provides a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. The specific steps are as follows:

[0057] S1. Divide the bottom of the asymmetric large-section rail into three regions: I, II, and III (e.g., Figure 1 As shown), the rail base undergoes accelerated cooling throughout the entire heat treatment process. The rail begins accelerated cooling at 840℃ within the heat treatment unit, with cooling rates of 3.3℃ / s in zone I, 5.2℃ / s in zone II, and 2.6℃ / s in zone III. Accelerated cooling begins simultaneously on both sides of the rail head. Figure 1 The same cooling rate of 6.5℃ / s is applied to both sides of the rail head, and the temperature at the center axis of the rail head tread is taken as the tread temperature T. IV T IV The rail head stopped accelerating cooling when the temperature dropped to 513℃.

[0058] S2. The temperature at the point approximately 1 / 3 of the distance between the edge of the short-leg side rail base and the centerline of the rail base is defined as the short-leg side rail base temperature T. I The temperature at the centerline of the rail base is taken as the rail base temperature T. II The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0059] When the rails exit the cooling unit, T I Controlled at 389℃, T II Controlled at 409℃, T III Controlled at 401℃, and T II -T I =20℃≤25℃、T II -T III =8℃≤15℃、T III -T I =12℃≤20℃.

[0060] Example 6

[0061] This embodiment provides a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. The specific steps are as follows:

[0062] S1. Divide the bottom of the asymmetric large-section rail into three regions: I, II, and III (e.g., Figure 1 As shown), the rail base undergoes accelerated cooling throughout the entire heat treatment process. The rail begins accelerated cooling at 797℃ within the heat treatment unit, with cooling rates of 2.9℃ / s in zone I, 4.5℃ / s in zone II, and 2.1℃ / s in zone III. Accelerated cooling begins simultaneously on both sides of the rail head. Figure 1 The same cooling rate of 5.6℃ / s is applied to both sides of the rail head, and the temperature at the center axis of the rail head tread is taken as the tread temperature T.IV T IV The rail head stopped accelerating cooling when the temperature dropped to 473°C.

[0063] S2. The temperature at the point approximately 1 / 3 of the distance between the edge of the short-leg side rail base and the centerline of the rail base is defined as the short-leg side rail base temperature T. I The temperature at the centerline of the rail base is taken as the rail base temperature T. II The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0064] When the rails exit the cooling unit, T I Controlled at 391℃, T II Controlled at 405℃, T III Controlled at 395℃, and T II -T I =14℃≤25℃、T II -T III =10℃≤15℃、T III -T I =4℃≤20℃.

[0065] Example 7

[0066] This embodiment provides a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. The specific steps are as follows:

[0067] S1. Divide the bottom of the asymmetric large-section rail into three regions: I, II, and III (e.g., Figure 1 As shown), the rail base undergoes accelerated cooling throughout the entire heat treatment process. The rail begins accelerated cooling at 812℃ within the heat treatment unit, with cooling rates of 3.1℃ / s in zone I, 4.9℃ / s in zone II, and 2.3℃ / s in zone III. Accelerated cooling begins simultaneously at the rail head and rail base, with both sides of the rail head ( Figure 1 The same cooling rate of 6.0℃ / s is applied to both sides of the rail head, and the temperature at the center axis of the rail head tread is taken as the tread temperature T. IV T IV The rail head stopped accelerating cooling when the temperature dropped to 492°C.

[0068] S2. The temperature at the point approximately 1 / 3 of the distance between the edge of the short-leg side rail base and the centerline of the rail base is defined as the short-leg side rail base temperature T. I The temperature at the centerline of the rail base is taken as the rail base temperature T. II The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0069] When the rails exit the cooling unit, T I Controlled at 389℃, T II Controlled at 413℃, T III Controlled at 402℃, and T II -T I =19℃≤24℃、T II -T III =11℃≤15℃、T III -T I =13℃≤20℃.

[0070] Example 8

[0071] This embodiment provides a method for controlling lateral bending during the heat treatment of asymmetric large-section rails. The specific steps are as follows:

[0072] S1. Divide the bottom of the asymmetric large-section rail into three regions: I, II, and III (e.g., Figure 1 As shown), the rail base undergoes accelerated cooling throughout the entire heat treatment process. The rail begins accelerated cooling at 718℃ within the heat treatment unit, with cooling rates of 2.1℃ / s in zone I, 3.5℃ / s in zone II, and 1.5℃ / s in zone III. Accelerated cooling begins simultaneously on both sides of the rail head. ​ The same cooling rate of 3.8℃ / s is applied to both sides of the rail head, and the temperature at the center axis of the rail head tread is taken as the tread temperature T. IV T IV The rail head stopped accelerating cooling when the temperature dropped to 443°C.

[0073] S2. The temperature at the point approximately 1 / 3 of the distance between the edge of the short-leg side rail base and the centerline of the rail base is defined as the short-leg side rail base temperature T. I The temperature at the centerline of the rail base is taken as the rail base temperature T. II The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III ,

[0074] When the rails exit the cooling unit, T I Controlled at 370℃, T II Controlled at 388℃, T III Controlled at 380℃, and T II -T I =18℃≤25℃、T II -T III =8℃≤15℃、T III -T I =10℃≤20℃.

[0075] Comparative Example 1

[0076] This comparative example follows the conventional heat-treated rail production method, with the following specific steps:

[0077] S1. The rail begins accelerated cooling in the heat treatment unit at 735℃; the rail head and rail base begin accelerated cooling simultaneously, with a cooling rate of 3.8℃ / s on both sides of the rail head and 3.1℃ / s on the rail base. The temperature at the centerline of the rail head tread is taken as the tread temperature T. IV T IV When the temperature drops to 469℃, both the rail head and the rail base stop accelerating cooling simultaneously.

[0078] Comparative Example 2

[0079] This comparative example follows the conventional heat-treated rail production method, with the following specific steps:

[0080] S1. The rail begins accelerated cooling in the heat treatment unit at a temperature of 783℃; the rail head and rail base begin accelerated cooling simultaneously, with a cooling rate of 4.9℃ / s on both sides of the rail head and 3.5℃ / s on the rail base. The temperature at the centerline of the rail head tread is taken as the tread temperature T. IV T IV When the temperature drops to 510℃, both the rail head and the rail base stop accelerating cooling simultaneously.

[0081] The heat treatment process parameters of the rails in the embodiments and comparative examples of this invention are shown in Table 1. Comparative examples 1 and 2 can be produced by following the conventional rail heat treatment process described above.

[0082] Table 1. Heat treatment processes for the rails in the examples and comparative cases.

[0083]

[0084] The side bending of the rails after exiting the heat treatment unit and the passage of the rails on the roller conveyor in the examples and comparative examples are shown in Table 2 below.

[0085] Table 2. Lateral bending of the rails and roller conveyor traffic conditions in various embodiments and comparative examples of the present invention.

[0086]

[0087] It can be seen that the lateral bending of the asymmetric large-section steel rail produced by the method of the present invention after exiting the heat treatment unit is within 0.8 mm / m, and the optimal lateral bending reaches 0.3 mm / m. This effectively avoids the situation where the steel rail is unable to pass through the roller conveyor normally or hits the side baffle of the roller conveyor due to severe lateral bending, thus ensuring the safe and smooth operation of the heat treatment production process of the asymmetric large-section steel rail.

Claims

1. A method for controlling lateral bending during heat treatment of asymmetric large-section rails, characterized in that, Includes the following steps: S1. The rail base of the asymmetric large-section rail is divided into three regions: I, II, and III. Region II is located in the middle of the rail base, and regions I and III are located on either side of region II. Region II is distributed from the vertical edge directly opposite the short leg side of the rail web to the edge directly opposite the connection between the long leg side of the rail web and the rail base. Region I is distributed from the boundary of region II to the edge of the short leg side of the rail base. Region III is distributed from the boundary of region II to the edge of the long leg side of the rail base. The rail base undergoes accelerated cooling throughout the entire heat treatment process. The cooling rate is 1.5–3.5℃ / s in Zone I, 3–5.5℃ / s in Zone II, and 1–3℃ / s in Zone III. The rail begins accelerated cooling at 690–860℃ within the heat treatment unit. Accelerated cooling begins simultaneously on both sides of the rail head, with the same cooling rate of 3–7℃ / s applied to both sides. The temperature at the centerline of the rail head tread is taken as the tread temperature T. IV T IV The rail head stops accelerating cooling when the temperature drops to 430–525°C. S2. The temperature T on the short leg side is defined as the temperature located at approximately 1 / 3 of the distance between the edge of the rail base and the centerline of the rail base. I The temperature at the centerline of the rail base is taken as the rail base temperature T. II The temperature T on the long-leg side is defined as the temperature located at approximately 1 / 3 of the distance between the bottom edge of the long-leg side rail and the centerline of the rail bottom. III , When the rails exit the cooling unit, T I Controlled at 365~395℃, T II Controlled at 380-420℃, T III The temperature should be controlled between 375 and 405℃, and |T II -T I |≤25℃、|T II -T III |≤15℃、|T III -T I ≤20℃.

2. The method for controlling lateral bending during the heat treatment of asymmetric large-section rails as described in claim 1, characterized in that, In step S1, the temperature at which the rail begins to be accelerated to cool in the heat treatment unit is 790–840°C.

3. The method for controlling lateral bending during the heat treatment of asymmetric large-section rails as described in claim 1, characterized in that, In step S1, accelerated cooling begins simultaneously on both the rail head and the rail base within the heat treatment unit, with the same cooling rate of 5.5–6.5 °C / s applied to both sides of the rail head. IV When the temperature drops to 470-515℃, the rail head stops accelerating cooling.

4. The method for controlling lateral bending during the heat treatment of asymmetric large-section rails as described in claim 1, characterized in that, In step S1, the cooling rate of zone I is 2.9–3.3 °C / s, the cooling rate of zone II is 4.9–5.2 °C / s, and the cooling rate of zone III is 2.1–2.6 °C / s.

5. The method for controlling lateral bending during heat treatment of asymmetric large-section rails as described in claim 1, characterized in that, In step S2, when the rail exits the cooling unit, T I Controlled at 389–391℃, T II Controlled at 405~413℃, T III The temperature should be controlled between 395 and 402℃, and |T II -T I |≤25℃、|T II -T III |≤15℃、|T III -T I ≤20℃.

6. The method for controlling lateral bending during heat treatment of asymmetric large-section rails as described in claim 1, characterized in that, Includes the following steps: S1. The rail base of the asymmetric large-section rail is divided into three regions: I, II, and III. Region II is located in the middle of the rail base, with Regions I and III located on either side of Region II. Region II extends from the vertical edge directly opposite the short leg side of the rail web to the edge directly opposite the connection point between the long leg side of the rail web and the rail base. Region I extends from the boundary of Region II to the edge of the short leg side of the rail base. Region III extends from the boundary of Region II to the edge of the long leg side of the rail base. The rail base undergoes accelerated cooling throughout the entire heat treatment process. The cooling rate is 3.3℃ / s in zone I, 5.2℃ / s in zone II, and 2.6℃ / s in zone III. The rail begins accelerated cooling at 840℃ within the heat treatment unit. Accelerated cooling begins simultaneously on both the rail head and the rail base, with the same cooling rate of 6.5℃ / s applied to both sides of the rail head. The temperature at the centerline of the rail head tread is defined as the tread temperature T. IV T IV The rail head stops accelerating cooling when the temperature drops to 513℃. S2. The temperature at the centerline of the rail base in Zone II is taken as the rail base temperature T. II The temperature T on the short leg side of the rail is defined as the temperature at approximately 1 / 3 of the distance between the edge of the rail base and the centerline of the rail base on the short leg side of section I. I The temperature at approximately 1 / 3 of the distance between the edge of the long-leg side rail and the centerline of the rail in Zone III is defined as T. III , When the rails exit the cooling unit, T II Controlled at 409℃, T I Controlled at 389℃, T III Control the temperature at 401℃.

7. The method for controlling lateral bending during the heat treatment of asymmetric large-section rails as described in claim 1, characterized in that, The lateral bending of asymmetric large-section steel rails after exiting the heat treatment unit is ≤0.8mm / m.

Images