Method for controlling vertical flatness of large-section turnout rail in on-line heat treatment

Abstract

The application discloses a control method for vertical straightness of large-section turnout rail on-line heat treatment, which comprises the following steps: after the turnout rail enters a heat treatment unit, the rail head and the rail bottom are simultaneously subjected to accelerated cooling, the cooling time is 80-110s, the cooling speed of the rail head is 2-4 DEG C / s, the cooling speed of the rail bottom is 1.5-2 DEG C / s, and the temperature of the rail head is controlled at 510-530 DEG C when the accelerated cooling is finished; only the rail bottom is subjected to accelerated cooling, the cooling time is 5-10s, and the cooling speed is 1.0-1.5 DEG C / s; the rail head and the rail bottom are simultaneously subjected to accelerated cooling for 10-15s, the cooling speed of the rail head is 0.8-1.3 DEG C / s, and the cooling speed of the rail bottom is 0.6-1.0 DEG C / s. The application can reduce the adverse effect caused by high return temperature of the large-section turnout rail, keep good straightness in the vertical direction, and is beneficial to the continuity of the on-line heat treatment operation of the large-section turnout rail, and the control method is convenient, efficient, easy to operate and easy to popularize and apply.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgical heat treatment, and particularly relates to a control method for vertical straightness of large-section turnout rail online heat treatment. BACKGROUND

[0002] Turnout rails have the characteristics of strong integrity, large rigidity, good smoothness and high safety, and are widely used in the production of turnout points on lines. With the development of China's railway transportation towards high speed and heavy load, the performance requirements for turnout rails are becoming higher and higher, and the lines require the use of online heat treatment turnout rails for the production of turnout points.

[0003] The online heat treatment production process of turnout rails is to utilize the residual heat of the rails after rolling to enter the heat treatment unit (which is essentially an accelerated cooling process), and after the rails leave the heat treatment unit, they are cooled on the cooling bed on the transportation roller way in an air cooling state. The entire temperature change of the rails is divided into three stages: in the first stage, the temperature of the rails continuously decreases during the accelerated cooling process; in the second stage, the temperature of the rails increases after the accelerated cooling is stopped; and in the third stage, the temperature of the rails gradually decreases to room temperature in the subsequent air cooling state after the temperature of the rails reaches a peak.

[0004] During the heat treatment process of large-section turnout rails, due to the large specification section, especially the rail waist thickness of 44mm, which is increased by 175% compared to ordinary rails, the internal heat capacity of the rails is higher. When the rails stop accelerating cooling, the rail head return temperature is high. In the subsequent air cooling process, the rails are prone to upward bending in the vertical direction. In severe cases (the maximum bending amount reaches 4-5mm / m), the rails will run out of the roller way beyond the side baffle, causing the rails to fail to normally travel to the cooling bed and affecting the continuity of the production line.

[0005] The patent "Production control method for improving straightness of online heat treatment rails after quenching" (CN 112877531B) provides a production control method for improving the straightness of heat treated rails after quenching, which controls the cooling intensity and temperature difference of the rail head and rail bottom to ensure the straightness of the rails after heat treatment. The patent "Straightness control method for online heat treatment of rails" (CN 109182715B) provides a straightness control method for online heat treatment of rails, which includes two steps of bending treatment and heat treatment, and controls the straightness of the rails after heat treatment by controlling the accelerated cooling time, the flow ratio of the cooling medium and the temperature of the rails after heat treatment. These two methods are only applicable to the straightness control of ordinary rails and do not consider the adverse effects of high return temperature of large-section turnout rails on straightness control. SUMMARY

[0006] The purpose of the present application is to provide a large-section turnout rail online heat treatment vertical direction flatness control method, reduce the adverse effects of large-section turnout rail reheat high, make the turnout rail keep good flatness in the vertical direction after the heat treatment unit and in the subsequent cooling process, be beneficial to the continuity of large-section turnout rail online heat treatment operation, and the control method is convenient, efficient, and easy to operate and promote application.

[0007] The technical scheme adopted by the present application is:

[0008] A large-section turnout rail online heat treatment vertical direction flatness control method, comprising the following steps:

[0009] Step 1, after the turnout rail enters the heat treatment unit, the rail head and the rail bottom are simultaneously subjected to accelerated cooling, the cooling time is 80-110s, the rail head cooling speed is 2-4℃ / s, the rail bottom cooling speed is 1.5-2℃ / s, and the rail head temperature is controlled at 510-530℃ when the accelerated cooling is finished;

[0010] Step 2, only the rail bottom is subjected to accelerated cooling, the cooling time is 5-10s, and the cooling speed is 1.0-1.5℃ / s;

[0011] Step 3, the rail head and the rail bottom are simultaneously subjected to accelerated cooling for 10-15s, the rail head cooling speed is 0.8-1.3℃ / s, and the rail bottom cooling speed is 0.6-1.0℃ / s.

[0012] Preferably, in the step 1, the temperature of the rail starting accelerated cooling in the heat treatment unit is 740-800℃.

[0013] Preferably, in the step 2, the rail head starts to enter the reheat stage because the accelerated cooling is stopped, and the rail head reheat reaches the peak value within 5-10s.

[0014] Preferably, after the step 3, when the rail exits the heat treatment unit, the rail head temperature is 30-60℃ lower than the rail bottom temperature.

[0015] Preferably, the accelerated cooling medium for heat treatment of the heat treatment unit includes but is not limited to compressed air and water mist.

[0016] Preferably, in the step 1, the rail head and the rail bottom are simultaneously subjected to accelerated cooling for 85s, the rail head cooling speed is 2.8℃ / s, and the rail bottom cooling speed is 1.8℃ / s; the rail head temperature is 522℃ when the accelerated cooling in the step 1 is finished;

[0017] In the step 2, only the rail bottom is subjected to accelerated cooling for 8s, the cooling speed is 1.2℃ / s, and the rail head reheat increases by 26℃;

[0018] In the step 3, the rail head and the rail bottom are simultaneously accelerated cooling for 10s, the cooling speed of the rail head is 1.2℃ / s, and the cooling speed of the rail bottom is 0.8℃ / s.

[0019] Preferably, in the step 1, the rail head and the rail bottom are simultaneously started to be accelerated cooling for 91s, the cooling speed of the rail head is 3.0℃ / s, and the cooling speed of the rail bottom is 2.0℃ / s; when the accelerated cooling in the step 1 is finished, the temperature of the rail head is 517℃;

[0020] In the step 2, only the rail bottom is accelerated cooling for 9s, the cooling speed is 1.5℃ / s, and the temperature increment of the rail head is 31℃;

[0021] In the step 3, the rail head and the rail bottom are simultaneously accelerated cooling for 10s, the cooling speed of the rail head is 1.2℃ / s, and the cooling speed of the rail bottom is 0.8℃ / s.

[0022] Preferably, in the step 1, the rail head and the rail bottom are simultaneously started to be accelerated cooling for 82s, the cooling speed of the rail head is 2.8℃ / s, and the cooling speed of the rail bottom is 1.9℃ / s; when the accelerated cooling is finished, the temperature of the rail head is 515℃;

[0023] In the step 2, only the rail bottom is accelerated cooling for 6s, the cooling speed is 1.1℃ / s, and the temperature increment of the rail head is 23℃;

[0024] In the step 3, the rail head and the rail bottom are simultaneously accelerated cooling for 12s, the cooling speed of the rail head is 0.8℃ / s, and the cooling speed of the rail bottom is 0.7℃ / s.

[0025] Further, the difference between the cooling speeds of the rail head and the rail bottom in the air cooling process after the heat treatment unit is reduced, so that the switch rail keeps good straightness in the vertical direction; through the control method, the straightness in the vertical direction of the switch rail after the heat treatment unit and in the subsequent air cooling process is less than or equal to 0.35mm / m, and the switch rail can smoothly pass through the transport roller and move to the cooling bed.

[0026] The beneficial effects of the present application are:

[0027] The present application controls the process reasonably, differentiates the cooling of the rail head and the rail bottom, advances the temperature increment stage of the large-section switch rail to be completed in the heat treatment unit, reduces the adverse effects caused by the high temperature increment of the large-section switch rail, keeps good straightness of the switch rail in the vertical direction after the heat treatment unit and in the subsequent cooling process, and enables the switch rail to normally move to the cooling bed; the straightness in the vertical direction of the switch rail after the heat treatment unit and in the subsequent air cooling process is less than or equal to 0.35mm / m, which is beneficial to the continuity of the online heat treatment of the large-section switch rail, and the control method is convenient, efficient, and easy to operate and popularize. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flow chart of the control method of the vertical flatness of the large-section turnout rail on-line heat treatment in the embodiments of the application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0030] In the description of the present application, it should be understood that if the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation of the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features limited by "first", "second" can be explicitly or implicitly included one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0031] In the description of the present application, it should be noted that unless otherwise specifically specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected. It can be mechanically connected, or electrically connected. It can be directly connected, or indirectly connected through an intermediate medium. It can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0032] In order to solve the problem of serious bending of large-section turnout rail on-line heat treatment in the vertical direction, the present application provides a control method for the flatness of the large-section turnout rail on-line heat treatment in the vertical direction. Through reasonable cooling process, the flatness of the turnout rail in the vertical direction is ≤0.35mm / m. The preferred mode of the present application will be described in detail through specific embodiments.

[0033] Example 1 : The switch rail starts to accelerate cooling at 760°C in the heat treatment unit, the rail head and the rail bottom start to accelerate cooling at the same time for 85s, the cooling speed of the rail head is 2.8°C / s, the cooling speed of the rail bottom is 1.8°C / s, at the end of the acceleration cooling, the temperature of the rail head is 522°C; the acceleration cooling is started only for the rail bottom for 8s, the cooling speed is 1.2°C / s, the temperature increment of the rail head is 26°C; the acceleration cooling is started for the rail head and the rail bottom at the same time for 10s, the cooling speed of the rail head is 1.2°C / s, the cooling speed of the rail bottom is 0.8°C / s. When the rail leaves the heat treatment unit, the temperature of the rail head is 53°C lower than the temperature of the rail bottom. After the switch rail leaves the heat treatment unit and during the subsequent air cooling process, the vertical straightness is 0.29mm / m, and the rail passes through the transportation roller way to the cooling bed smoothly.

[0034] Example 2: The switch rail starts to accelerate cooling at 790°C in the heat treatment unit, the rail head and the rail bottom start to accelerate cooling at the same time for 91s, the cooling speed of the rail head is 3.0°C / s, the cooling speed of the rail bottom is 2.0°C / s, at the end of the acceleration cooling, the temperature of the rail head is 517°C; the acceleration cooling is started only for the rail bottom for 9s, the cooling speed is 1.5°C / s, the temperature increment of the rail head is 31°C; the acceleration cooling is started for the rail head and the rail bottom at the same time for 10s, the cooling speed of the rail head is 1.2°C / s, the cooling speed of the rail bottom is 0.8°C / s. When the rail leaves the heat treatment unit, the temperature of the rail head is 51°C lower than the temperature of the rail bottom. After the switch rail leaves the heat treatment unit and during the subsequent air cooling process, the vertical straightness is 0.23mm / m, and the rail passes through the transportation roller way to the cooling bed smoothly.

[0035] Example 3: The switch rail starts to accelerate cooling at 745°C in the heat treatment unit, the rail head and the rail bottom start to accelerate cooling at the same time for 82s, the cooling speed of the rail head is 2.8°C / s, the cooling speed of the rail bottom is 1.9°C / s, at the end of the acceleration cooling, the temperature of the rail head is 515°C; the acceleration cooling is started only for the rail bottom for 6s, the cooling speed is 1.1°C / s, the temperature increment of the rail head is 23°C; the acceleration cooling is started for the rail head and the rail bottom at the same time for 12s, the cooling speed of the rail head is 0.8°C / s, the cooling speed of the rail bottom is 0.7°C / s. When the rail leaves the heat treatment unit, the temperature of the rail head is 45°C lower than the temperature of the rail bottom. After the switch rail leaves the heat treatment unit and during the subsequent air cooling process, the vertical straightness is 0.21mm / m, and the rail passes through the transportation roller way to the cooling bed smoothly.

[0036] Example 4: The switch rail starts accelerated cooling at 750℃ in the heat treatment unit, the rail head and the rail bottom start accelerated cooling at the same time for 92s, the cooling speed of the rail head is 2.6℃ / s, the cooling speed of the rail bottom is 1.6℃ / s, at the end of the accelerated cooling, the temperature of the rail head is 511℃; the accelerated cooling is started for the rail bottom only for 9s, the cooling speed is 1.3℃ / s, the temperature of the rail head increases by 25℃; the accelerated cooling is started for the rail head and the rail bottom at the same time for 13s, the cooling speed of the rail head is 1.1℃ / s, the cooling speed of the rail bottom is 0.9℃ / s. When the rail is out of the heat treatment unit, the temperature of the rail head is 58℃ lower than the temperature of the rail bottom. After the switch rail is out of the heat treatment unit and during the subsequent air cooling process, the flatness in the vertical direction is 0.34mm / m, and the rail smoothly passes through the transportation roller and moves to the cooling bed.

[0037] Example 5: The switch rail starts accelerated cooling at 795℃ in the heat treatment unit, the rail head and the rail bottom start accelerated cooling at the same time for 81s, the cooling speed of the rail head is 3.3℃ / s, the cooling speed of the rail bottom is 2.0℃ / s, at the end of the accelerated cooling, the temperature of the rail head is 528℃; the accelerated cooling is started for the rail bottom only for 10s, the cooling speed is 1.5℃ / s, the temperature of the rail head increases by 37℃; the accelerated cooling is started for the rail head and the rail bottom at the same time for 14s, the cooling speed of the rail head is 0.9℃ / s, the cooling speed of the rail bottom is 1.0℃ / s. When the rail is out of the heat treatment unit, the temperature of the rail head is 52℃ lower than the temperature of the rail bottom. After the switch rail is out of the heat treatment unit and during the subsequent air cooling process, the flatness in the vertical direction is 0.35mm / m, and the rail smoothly passes through the transportation roller and moves to the cooling bed.

[0038] It can be seen that the flatness in the vertical direction of the switch rail produced by the method of the present application is controlled below 0.35mm / m after the rail is out of the heat treatment unit and during the subsequent air cooling process, and the rail smoothly passes through the transportation roller and moves to the cooling bed, which guarantees the safe and smooth operation of the online heat treatment of the switch rail.

[0039] The working principle of the present application is: after the turnout rail enters the heat treatment unit, the accelerated cooling process is carried out in three steps, the first step is to start accelerated cooling of the rail head and the rail bottom at the same time for 80-110s, the cooling speed of the rail head is 2-4℃ / s, and the cooling speed of the rail bottom is 1.5-2.0℃ / s, at the end of the accelerated cooling, the rail head temperature is controlled at 510-530℃, at this time the rail head part has completed the organization transformation and obtained the ideal organization; the second step is to only accelerate the cooling of the rail bottom for 5-10s, the cooling speed is 1.0-1.5℃ / s, the rail head stops accelerated cooling and starts to enter the reheat stage in the heat treatment unit in advance, in 5-10s, the rail head reheat reaches the peak, the temperature increases by 20-40℃; the third step is to accelerate the cooling of the rail head and the rail bottom at the same time for 10-15s, the cooling speed of the rail head is 0.8-1.3℃ / s, and the cooling speed of the rail bottom is 0.6-1.0℃ / s. When the rail exits the heat treatment unit, the rail head temperature is controlled to be 30-60℃ lower than the rail bottom temperature, so as to reduce the difference between the cooling speeds of the rail head and the rail bottom in the air cooling process after exiting the heat treatment unit, and the turnout rail maintains good straightness in the vertical direction.

[0040] It should be noted that the relational terms herein such as first and second and the like are used solely to distinguish one entity or action from another, without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0041] It should be understood that, for those skilled in the art, improvements or changes can be made according to the above description, and all these improvements and changes shall fall within the protection scope of the appended claims of the present application.

Claims

1. A method for controlling the vertical straightness of large-section turnout rails during online heat treatment, characterized in that: Includes the following steps: Step 1: After the turnout rails enter the heat treatment unit, the rail head and rail base of the turnout rails are simultaneously subjected to accelerated cooling. The cooling time is 80~110s, the cooling rate of the rail head is 2~4℃ / s, and the cooling rate of the rail base is 1.5~2℃ / s. When the accelerated cooling is finished, the rail head temperature is controlled at 510~530℃. Step 2: Accelerate cooling only on the rail base, with a cooling time of 5-10 seconds and a cooling rate of 1.0-1.5℃ / s; Step 3: Simultaneously accelerate the cooling of the rail head and rail base for 10-15 seconds, with the rail head cooling rate being 0.8-1.3℃ / s and the rail base cooling rate being 0.6-1.0℃ / s.

2. The method for controlling the vertical straightness of large-section turnout rails during online heat treatment as described in claim 1, characterized in that: In step 1, the temperature at which the rail begins to be accelerated cooled in the heat treatment unit is 740–800°C.

3. The method for controlling the vertical straightness of large-section turnout rails during online heat treatment as described in claim 1, characterized in that: In step 2, the rail head begins to warm up after the accelerated cooling stops, and the rail head reaches its peak temperature within 5-10 seconds.

4. The method for controlling the vertical straightness of large-section turnout rails during online heat treatment as described in claim 1, characterized in that: After step 3, the rail head temperature is 30-60°C lower than the rail bottom temperature.

5. The method for controlling the vertical straightness of large-section turnout rails during online heat treatment as described in claim 1, characterized in that: Accelerated cooling media used in heat treatment include, but are not limited to, compressed air and water mist.

6. The method for controlling the vertical straightness of large-section turnout rails during online heat treatment as described in claim 1, characterized in that: In step 1, the rail head and rail bottom are simultaneously subjected to accelerated cooling for 85 seconds, with the rail head cooling rate being 2.8℃ / s and the rail bottom cooling rate being 1.8℃ / s. In step 2, the rail bottom is accelerated and cooled for 8 seconds, with a cooling rate of 1.2℃ / s. In step 3, the rail head and rail bottom are simultaneously subjected to accelerated cooling for 10 seconds, with the rail head cooling rate being 1.2℃ / s and the rail bottom cooling rate being 0.8℃ / s.

7. The method for controlling the vertical straightness of large-section turnout rails during online heat treatment as described in claim 1, characterized in that: In step 1, the rail head and rail bottom are simultaneously subjected to accelerated cooling for 91 seconds, with the rail head cooling rate at 3.0℃ / s and the rail bottom cooling rate at 2.0℃ / s. In step 2, only the rail base is accelerated to cool for 9 seconds, with a cooling rate of 1.5℃ / s, and the rail head temperature rise is increased by 31℃. In step 3, the rail head and rail bottom are simultaneously subjected to accelerated cooling for 10 seconds, with the rail head cooling rate at 1.2℃ / s and the rail bottom cooling rate at 0.8℃ / s.

8. The method for controlling the vertical straightness of large-section turnout rails during online heat treatment as described in claim 1, characterized in that: In step 1, the rail head and rail bottom are simultaneously subjected to accelerated cooling for 82 seconds, with a rail head cooling rate of 2.8℃ / s and a rail bottom cooling rate of 1.9℃ / s. In step 2, only the rail base is accelerated to cool for 6 seconds, with a cooling rate of 1.1℃ / s, and the rail head temperature rise is increased by 23℃. In step 3, the rail head and rail base are simultaneously subjected to accelerated cooling for 12 seconds, with the rail head cooling rate at 0.8℃ / s and the rail base cooling rate at 0.7℃ / s.

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