Method and device for treating welded joints of hot-rolled and heat-treated steel rails

Abstract

The present application belongs to the field of rail manufacturing, and discloses a processing method and device for a welded joint of a hot-rolled rail and a heat-treated rail. The method comprises: performing regional controlled cooling on a hot-state welded joint formed by welding a hot-rolled eutectoid pearlite rail and a heat-treated eutectoid pearlite rail; slowly cooling a hot-affected zone on one side of the hot-rolled eutectoid pearlite rail under the condition of heating temperature compensation; accelerating cooling of a hot-affected zone on one side of the heat-treated eutectoid pearlite rail under the action of a cooling medium until the surface temperature of the welded joint is reduced to a temperature threshold; and cooling the welded joint subjected to the regional controlled cooling in the environment until the surface temperature is reduced to the ambient temperature. The device is used to implement the above-mentioned regional controlled cooling. The method and device can improve the matching of hardness between the hot-affected zones on both sides of the weld and between the hot-affected zones on both sides and the base material of the rails with different strengths.

Description

Technical Field

[0001] This invention relates to the field of railway rail manufacturing technology, and in particular to a method and apparatus for processing welded joints of hot-rolled rails and heat-treated rails. Background Technology

[0002] Based on differences in manufacturing processes, rails can be subdivided into hot-rolled rails and heat-treated rails. For hot-rolled eutectoid pearlitic rails, the rails are cooled to ambient temperature after rolling. For heat-treated eutectoid pearlitic rails, after rolling, a rapid cooling heat treatment using compressed air or a water mist mixture as the cooling medium is applied. This process, with its strong grain-refining effect under high supercooling, refines the austenite grains and pearlite lamellar spacing, further enhancing the strength, hardness, and toughness of the rails compared to hot-rolled rails. Therefore, the tensile strength of heat-treated eutectoid pearlitic rails is typically 180-220 MPa higher than that of hot-rolled eutectoid pearlitic rails of the same composition. Correspondingly, under the same testing conditions, the average hardness of the base material of heat-treated eutectoid pearlitic rails is 30-50 HV higher than that of hot-rolled eutectoid pearlitic rails of the same composition.

[0003] Different railway line conditions impose varying requirements on rail materials and performance. For straight sections and large-radius curves on conventional railways (operating speeds below 200 km / h) and high-speed railways (operating speeds between 200 and 350 km / h), hot-rolled rails are more suitable, while heat-treated rails with better wear resistance are typically used for sections with small-radius curves. On some railways with complex track conditions, the use of high-strength heat-treated rails may lead to deeper contact fatigue crack propagation, which could actually reduce the rail's service life. While the use of hot-rolled rails, with their slightly lower wear resistance, increases wear, it also significantly reduces the damage caused by the deeper propagation of contact fatigue cracks. Therefore, currently, both hot-rolled and heat-treated rails are commonly used on conventional and high-speed railways in China, which involves welding between rails of different strength grades.

[0004] Currently, mobile flash welding has become the mainstream online rail welding technology at railway construction sites both domestically and internationally. For hot-rolled rails, the heat-affected zone (HAZ) is essentially subjected to heat treatment due to the welding thermal cycle. Combined with the effects of multiple alloys in the rail steel, the overall hardness of the weld HAZ is higher than that of the base rail material used for welding; that is, the overall hardness of the weld HAZ of hot-rolled rails is higher than that of the base rail material used for welding. When the hardness of the weld HAZ of hot-rolled rails reaches more than 1.2 times the hardness of the base rail material, damage is more likely to occur preferentially in the base rail area due to the lower hardness of the base rail. For heat-treated rails, under the welding thermal cycle, the hardened layer that originally belonged to the base rail material is damaged, resulting in coarser austenite grains and a larger pearlite lamellar spacing in the weld HAZ than in the base rail material. Consequently, the overall hardness of the HAZ of heat-treated rails is lower than that of the base rail material used for welding. When the hardness of the heat-affected zone (HAZ) of a heat-treated rail is less than 0.9 times that of the rail base material, damage is more likely to occur preferentially in the HAZ due to its lower hardness. Furthermore, when the hardness of the HAZ of a heat-treated rail reaches more than 1.0 times (e.g., 1.1 to 1.2 times) of the rail base material, it is likely due to the formation of high-hardness martensite within the HAZ. Martensite exhibits high internal stress, making it prone to crack formation under wheel-rail contact pressure, which is detrimental to the overall service safety of the rail welded joint. In addition, martensite can also easily cause overall flaking of the rail head tread.

[0005] The difference in mechanical properties between hot-rolled eutectoid pearlitic steel rails and heat-treated eutectoid pearlitic steel rails presents challenges to their bonding. Achieving a balance in hardness between the heat-affected zones on both sides of the weld, and between these zones and the base steel materials of different strengths, is a pressing issue that needs to be addressed in this field. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method and apparatus for treating welded joints of hot-rolled and heat-treated steel rails. This method improves the hardness matching between the heat-affected zones on both sides of the weld and between the heat-affected zones and the base steel rails of different strengths.

[0007] According to one aspect of the present invention, a method for processing welded joints of hot-rolled steel rails and heat-treated steel rails is provided, comprising the following steps:

[0008] Step S1: The hot-state welded joint formed by welding hot-rolled eutectoid pearlitic steel rail and heat-treated eutectoid pearlitic steel rail is subjected to zoned controlled cooling. The heat-affected zone on the hot-rolled eutectoid pearlitic steel rail side is cooled slowly at a low cooling rate under the condition of heating temperature compensation, while the heat-affected zone on the heat-treated eutectoid pearlitic steel rail side is cooled accelerated under the action of cooling medium. The welded joint is subjected to the zoned controlled cooling until the surface temperature of the welded joint is reduced to the first temperature threshold.

[0009] Step S2: Cool the welded joint, which has undergone the controlled cooling in the divided areas, in an air environment until the surface temperature of the welded joint drops to the ambient temperature.

[0010] According to one embodiment of the present invention, the components of both the hot-rolled eutectoid pearlitic rail and the heat-treated eutectoid pearlitic rail are selected from the following range by weight percentage: 0.75%~0.82% C, 0.50%~0.80% Si, 0.70%~1.0% Mn, 0.30%~0.50% Cr, 0.04%~0.08% V, with the balance being Fe and unavoidable impurities.

[0011] According to one embodiment of the present invention, the slow cooling rate is 3.0~5.0℃ / s, and the accelerated cooling rate is 6.0~10.0℃ / s.

[0012] According to one embodiment of the present invention, the boundary line between the heat-affected zone on one side of the hot-rolled eutectoid pearlitic steel rail and the heat-affected zone on one side of the heat-treated eutectoid pearlitic steel rail is the weld center of the welded joint, wherein the tensile strength of the hot-rolled eutectoid pearlitic steel rail base material at room temperature is 1100~1180MPa and the hardness is 310~350HV, and the tensile strength of the heat-treated eutectoid pearlitic steel rail base material at room temperature is 1300~1380MPa and the hardness is 370~400HV.

[0013] According to one embodiment of the present invention, the processing method makes the hardness of the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail 1.0 to 1.1 times the hardness of the hot-rolled eutectoid pearlitic rail base material, and the hardness of the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail 0.9 to 1.0 times the hardness of the heat-treated eutectoid pearlitic rail base material.

[0014] According to one embodiment of the present invention, the first temperature threshold is 400~500°C, and the start temperature of the controlled cooling is 1000~1100°C.

[0015] According to another aspect of the present invention, a processing apparatus for welded joints of hot-rolled and heat-treated steel rails is provided, the apparatus being used to implement zoned controlled cooling in any of the above-described processing methods, comprising:

[0016] The first half has a first outer shell resembling the shape of a steel rail. The inner wall of the first outer shell is provided with multiple heating elements. Inside each heating element is an insulation layer resembling the shape of a steel rail, and the insulation layer is connected to the outer shell.

[0017] The second half has a second outer shell similar in shape to the rail head of the rail. The second outer shell forms a chamber for containing a cooling medium, and the side wall of the chamber near the rail head tread has cooling medium injection holes.

[0018] According to one embodiment of the present invention, the first half includes a front portion and a rear portion that are rotatably connected together, the front portion and the rear portion being symmetrically arranged and pivotally connected together at the top.

[0019] According to one embodiment of the present invention, both the front portion and the rear portion include a rail head covering, a rail web covering, and a rail bottom covering, wherein the rail head covering provides more heat than the rail web covering and the rail bottom covering.

[0020] According to one embodiment of the present invention, in use, the insulation layer is attached to the outer surface of the rail.

[0021] By adopting the above technical solutions, the method for processing welded joints of hot-rolled and heat-treated steel rails provided by this invention, on the one hand, slowly cools the heat-affected zone on one side of the hot-rolled eutectoid pearlitic steel rail under temperature compensation conditions, controlling its grain size and pearlite lamellar spacing within a predetermined range different from the base material of the hot-rolled eutectoid pearlitic steel rail, so that the hardness of the heat-affected zone on one side of the hot-rolled eutectoid pearlitic steel rail is 1.0 to 1.1 times the hardness of the corresponding base material of the rail; on the other hand, it accelerates the cooling of the heat-affected zone on one side of the heat-treated eutectoid pearlitic steel rail under the action of a cooling medium, thereby reducing the coarsening caused by the welding thermal cycle. The grain size and pearlite lamellar spacing are further refined to ensure that the hardness of the heat-affected zone on one side of the heat-treated eutectoid pearlite rail is 0.9 to 1.0 times that of the corresponding rail base material. At the same time, since the hardness of the heat-affected zone on one side of the hot-rolled eutectoid pearlite rail is strengthened relative to the base material, while the hardness of the heat-affected zone on one side of the heat-treated eutectoid pearlite rail is weakened relative to the base material, the hardness difference between the heat-affected zones on both sides of the weld is reduced. The hardness difference between the heat-affected zones on both sides of the rail weld joint can be controlled within 21 HV, which helps to reduce the damage to the rail weld joint caused by excessive hardness difference between the heat-affected zones on both sides of the weld and ensures the safety of railway operation. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the longitudinal section of a welded rail joint.

[0023] Figure 2 This is a schematic diagram showing the location of the metallographic sample cut in each embodiment and comparative example;

[0024] Figure 3 A flowchart of a method for processing welded joints of hot-rolled steel rails and heat-treated steel rails according to an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of a processing device for the welded joint of hot-rolled steel rail and heat-treated steel rail according to an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram showing the distribution of heating elements in the first half of a processing device for the welded joint of hot-rolled steel rail and heat-treated steel rail according to an embodiment of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] To facilitate understanding and description of the technical solution of the present invention, the distribution relationship of the various regions of the rail welding joint will be briefly explained first. Figure 1 This is a schematic diagram of the longitudinal section of a welded rail joint. In the diagram, a represents a hot-rolled eutectoid pearlitic rail located on the left side of the weld joint, b represents the heat-affected zone of the joint, c represents a heat-treated eutectoid pearlitic rail located on the right side of the weld joint, d represents the rail head tread of the welded rail joint, and e represents the center of the weld.

[0029] Figure 2 This diagram illustrates the sampling locations of metallographic specimens in each embodiment and comparative example. Point e in the diagram represents the weld center, and point f represents the sampling location of the metallographic specimen from the rail head tread of the rail welded joint. The metallographic structure of the rail joint specimens was examined according to GB / T13298-2015 "Metallic Microstructure Examination Methods". A 3% nitric acid alcohol solution was used to etch the specimens, and a Leica MeF3 optical microscope was used to observe the metallographic structure of the rail joint.

[0030] Figure 3 A flowchart illustrating a method for processing a welded joint between a hot-rolled steel rail and a heat-treated steel rail according to an embodiment of the present invention is shown. As shown, the method generally includes:

[0031] Step S1: The hot-state welded joint formed by welding hot-rolled eutectoid pearlitic steel rail and heat-treated eutectoid pearlitic steel rail is subjected to zoned controlled cooling. The heat-affected zone on the hot-rolled eutectoid pearlitic steel rail side is cooled slowly at a low cooling rate under the condition of heating temperature compensation, while the heat-affected zone on the heat-treated eutectoid pearlitic steel rail side is cooled faster under the action of cooling medium. The welded joint is subjected to zoned controlled cooling until the surface temperature of the welded joint is reduced to the first temperature threshold.

[0032] Step S2: Cool the welded joint, which has undergone zoned controlled cooling, in an air environment until the surface temperature of the welded joint drops to the ambient temperature.

[0033] The steps in this method are described in detail below by way of example.

[0034] In some embodiments, the rail welded joint used in the above method is a joint formed by welding hot-rolled eutectoid pearlitic steel rails of the same type and specifications of 60~75kg / m and heat-treated eutectoid pearlitic steel rails of the same specifications using a rail moving flash welding machine. The welded joint refers to a region with a length of 60~80mm, including the weld and / or heat-affected zone, with the weld at the center of this region.

[0035] In some embodiments, the compositions of both hot-rolled and heat-treated eutectoid pearlitic rails are selected from the following ranges by weight: 0.75%–0.82% C, 0.50%–0.80% Si, 0.70%–1.0% Mn, 0.30%–0.50% Cr, 0.04%–0.08% V, with the balance being Fe and unavoidable impurities. The mechanical properties of hot-rolled and heat-treated eutectoid pearlitic rails containing the composition ranges given in this embodiment meet the wear resistance and strength requirements for rails.

[0036] Hot-rolled eutectoid pearlitic steel rails, after being cooled to ambient temperature following rolling, exhibit a tensile strength of 1100–1180 MPa and a hardness of 310–350 HV at room temperature. Heat-treated eutectoid pearlitic steel rails, after rolling, undergo a rapid cooling heat treatment using compressed air or a water mist mixture as the cooling medium. This process, with its strong grain-refining effect under significant supercooling, refines the austenite grains and pearlite lamellar spacing, further enhancing the strength, hardness, and toughness of the rail compared to hot-rolled steel. The base material for heat-treated eutectoid pearlitic steel rails has a tensile strength of 1300–1380 MPa and a hardness of 370–400 HV at room temperature. Therefore, the tensile strength of heat-treated eutectoid pearlitic steel rails is typically 180–220 MPa higher than that of hot-rolled eutectoid pearlitic steel rails of the same composition, and their average hardness is 30–50 HV higher. Two types of rails whose mechanical properties meet this range are easy to match after welding, and both their strength and hardness meet the requirements of the rails.

[0037] Optionally, in some embodiments, hot-rolled eutectoid pearlitic steel rails and heat-treated eutectoid pearlitic steel rails have the same composition, but due to differences in their processing technology, their hardness and strength differ.

[0038] In embodiments of the present invention, "room temperature" refers to a temperature in the range of 20~30°C.

[0039] In some embodiments, a hot welded joint refers to a welded joint where the rail surface remains at a high temperature after welding. The residual temperature of the rail welded joint surface can be adjusted by changing process parameters such as the rail welding heat input, thereby extending or shortening the high-temperature dwell time. This embodiment utilizes the residual heat from rail welding to perform post-weld treatment, improving energy utilization and shortening the processing flow and time. In some embodiments, controlled cooling in different zones begins when the temperature of the hot welded joint reaches 1000~1100°C.

[0040] In some embodiments, the zoned controlled cooling includes slow cooling of the heat-affected zone on one side of the hot-rolled eutectoid pearlitic steel rail at a low cooling rate under conditions of heating temperature compensation, while accelerating cooling of the heat-affected zone on the other side of the heat-treated eutectoid pearlitic steel rail under the action of a cooling medium. Specifically, the slow cooling rate of the heat-affected zone on the hot-rolled eutectoid pearlitic steel rail side can be controlled at 3.0~5.0℃ / s, and the accelerated cooling rate of the heat-affected zone on the heat-treated eutectoid pearlitic steel rail side can be controlled at 6.0~10.0℃ / s.

[0041] For the heat-affected zone (HAZ) on one side of the hot-rolled eutectoid pearlitic steel rail, slow cooling is performed under temperature compensation conditions. The grain size and pearlite lamellar spacing are controlled within a predetermined range compared to the base material of the hot-rolled eutectoid pearlitic steel rail. This ensures that the hardness of the HAZ on one side of the hot-rolled eutectoid pearlitic steel rail is 1.0 to 1.1 times that of the corresponding base material. Consequently, the difference in wear resistance between the base material and the welded HAZ is minimized, preventing damage accumulation in the base material area due to its lower hardness.

[0042] For heat-treated eutectoid pearlitic rails, the heat-affected zone (HAZ) on one side is accelerated cooling under the action of the cooling medium. Based on metallurgical principles, the rail weld joint exhibits a certain degree of dynamic undercooling under the high-temperature rapid cooling conditions after welding. This causes the phase transformation temperature of austenite to pearlite in the non-equilibrium state to shift downward, and the phase transformation temperature gradually decreases with increasing undercooling. As the undercooling increases, the pearlite formation temperature tends to occur at lower temperatures. At lower temperatures, the diffusion rate between carbon atoms and solute atoms slows down, and the migration distance becomes shorter, resulting in a decrease in the interlamellar spacing of pearlite. This further refines the coarsened grains and pearlite interlamellar spacing caused by the welding thermal cycle, ensuring that the hardness of the HAZ on one side of the heat-treated eutectoid pearlitic rail is 0.9 to 1.0 times the hardness of the corresponding rail base material. Therefore, the difference in wear resistance between the base material and the welded HAZ is small, avoiding damage accumulation in the HAZ due to low hardness. Moreover, since the hardness of the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail is strengthened relative to the base material, while the hardness of the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail is weakened relative to the base material, the hardness difference between the heat-affected zones on both sides of the weld is reduced and transitions slowly. The hardness difference between the heat-affected zones on both sides of the rail weld joint can be controlled within 21 HV, which helps to reduce the damage to the rail weld joint caused by excessive hardness difference between the heat-affected zones on both sides of the weld and ensures the safety of railway operation.

[0043] The above-mentioned zoned controlled cooling adopts, for example Figure 4 The treatment device shown is used to process the welded joint of hot-rolled steel rail and heat-treated steel rail. As shown, the treatment device generally includes a first half 100 and a second half 200. In this embodiment, the first half 100 is the left half and the second half 200 is the right half.

[0044] The first half 100 has a first outer shell 110 that resembles the shape of a rail. Multiple heating elements 120 are provided on the inner wall of the first outer shell 110. An insulation layer 130, also resembling the shape of a rail, is provided inside each heating element 120 and is connected to the outer shell 110. The first half 100 is used to wrap around the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail to heat and compensate the temperature of that heat-affected zone, allowing it to cool slowly at a set rate.

[0045] The second half 200 has a second outer shell 210 that resembles the shape of the rail head. The second outer shell 210 forms a chamber 220 for containing cooling medium. Cooling medium injection holes 230 are provided on the side wall of the chamber 220 near the rail head tread. The second half 200 is used to spray cooling medium onto the rail head tread of the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail to rapidly cool the heat-affected zone on that side.

[0046] The first half 100 is used for full-section temperature compensation of the heat-affected zone of the rail. Therefore, the first half 100 includes a rail head cover, a rail web cover, and a rail bottom cover. To facilitate the installation and removal of the device on the outer periphery of the rail, the first half 100 may include a front part and a rear part that are rotatably connected together. The front and rear parts are symmetrically arranged and pivotally connected at the top. Both the front and rear parts include a rail head cover, a rail web cover, and a rail bottom cover.

[0047] The first outer casing 110 can be a metal casing, welded from thin metal sheets. Multiple ceramic heating elements 120 are installed on the inner wall of the metal casing. The ceramic heating element on the left side of the device is connected to terminals H11 and H12, forming a circuit. Several parallel-arranged ceramic heating elements are connected in parallel and electrically connected to terminals H11 and H12, heating after being energized. An asbestos insulation layer is placed inside the heating element 120 and adjacent to the rail surface. The embedded asbestos insulation layer and ceramic heating elements can slowly cool the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail joint. The asbestos insulation layer has the functions of heat preservation and slowing down cooling, while the resistance heat released by the ceramic heating elements can compensate for the heat during the post-weld cooling process of the rail welded joint, thereby achieving slow cooling of the first half of the rail welded joint.

[0048] The second half 200 is used to spray cooling medium onto the rail head tread surface in the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail. Therefore, the second half 200 only includes the portion that conforms to the shape of the rail head. The second outer shell 210 can be welded from thin metal sheets, forming a chamber 220 for containing the cooling medium. Cooling medium injection holes 230 are opened on the side wall of the chamber 220 near the rail head tread surface. Compressed air channels I11 and I12 are provided inside the second half 200. A telescopic spring K1 can also be welded to the side wall of the second half 200 opposite to the rail head tread surface, which can maintain the distance between the air jet channel and the rail head tread surface at a set distance, such as 15 mm. The second half 200 can also include a front part and a rear part, which are pivotally connected together. Their pivot is coaxial with the pivot of the first half 100 (axis along the X direction in the figure), allowing the front and rear parts of the device to rotate up to 90°. The top connection between the first half 100 and the second half 200 of the device is fixed together by manual arc welding. The diameter of the injection hole 230 can be designed and processed according to actual needs to achieve cooling of different intensities. The compressed air flowing through channels I11 and I12 has the same gas pressure, which can be monitored by a pressure gauge and adjusted as needed. In addition, rubber sealing gaskets are provided at the mating positions of the front and rear parts of the second half 200. When the front and rear parts of the second half 200 are rotated to the same horizontal position, the rubber sealing gaskets can be used to seal the cooling device and prevent compressed air from escaping from the mating / joining positions of the second half 200.

[0049] In some embodiments, the pressure of the compressed air ejected by the second half 200 of the device during rapid cooling is 0.6 to 1.0 MPa, resulting in a cooling rate of 6.0 to 10.0 °C / s.

[0050] Furthermore, the asbestos insulation layer of the first half of the device 100 can fully adhere to the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail joint, meaning the asbestos insulation layer can separate the heat-affected zones on both sides of the rail welded joint. This ensures that the slow cooling of the heat-affected zone on the hot-rolled eutectoid pearlitic rail side of the rail welded joint does not interfere with the rapid cooling of the heat-treated eutectoid pearlitic rail side. Additionally, because the rail head is thicker and has slower heat transfer, the number of ceramic heating elements covering the rail head is greater than the number of ceramic heating elements in the rail web and rail base areas, ensuring that the entire cross-section of the first half of the rail welded joint is fully heated.

[0051] The first half of the device, 100, can be powered by a diesel generator or a 220V power supply, with a rated power of 10kW. The device uses commercial LCD track-type ceramic heating elements as the heat source; the heating elements are ceramic sheets measuring 10mm (length) × 10mm (width) × 5mm (thickness). Equipped with insulation material and a steel outer shell, it is designed as a ring-shaped, split heater for easy assembly and disassembly, suitable for full-section heating of the first half of the rail welded joint. The actual dimensions of the heating device, as well as the specifications and distribution of the heaters, can be adjusted according to the actual dimensions of the rail profile. It should be noted that the device can achieve slow cooling and isothermal (constant temperature) heat treatment of the rail welded joint through program settings and continuous heat compensation during power-on. In the device design, multiple sets of ceramic heating elements are evenly fixed inside the device, which has a similar profile to the rail, so that the heating device covers and fully adheres to the rail surface to achieve good heat conduction during heating. This device can achieve slow cooling and isothermal (constant temperature) heat treatment of the rail welded joint. During the experiment, a temperature controller was used to control the heating temperature. The operating temperature range of this device is 200~800℃. This split-type device can rotate a maximum of 90° around its center line.

[0052] Figure 5 This is a schematic diagram of the partial distribution of heating elements in the first half 100 of the processing device for the welded joint of a hot-rolled rail and a heat-treated rail according to an embodiment of the present invention. This part corresponds to the rail head region of the first half of the rail welded joint. In the figure, A2 corresponds to the rail head tread area of ​​the first half of the rail welded joint; B2 corresponds to the rail head side area of ​​the first half of the rail welded joint; C2 corresponds to the rail head lower jaw area of ​​the first half of the rail welded joint; D2 is an asbestos insulation layer; and F1 is a ceramic heating element distributed in the rail head tread area, rail head side area, and rail head lower jaw area of ​​the first half of the rail welded joint. Because the rail head side area is larger, the number of ceramic heating elements covering the rail head side area is greater than the number of ceramic heating elements covering the rail head tread area and rail head lower jaw area to ensure that the rail head of the first half of the rail welded joint is fully heated.

[0053] For the zoned controlled cooling in step S1, the heat-affected zone of the hot-rolled eutectoid pearlitic rail is enclosed in the first half 100 of the treatment device. Relatively slow cooling of the first half of the rail weld joint is achieved through resistance heating of the ceramic heating elements embedded in the first half 100, with the cooling rate controlled at 3.0~5.0℃ / s. The second half 200 of the treatment device is 15mm away from the weld joint surface. During rapid cooling, the pressure of the compressed air ejected is 0.6~1.0MPa, and the cooling rate is 6.0~10.0℃ / s. For the first half 100, the cooling rate is 3.0~5.0℃ / s. For the second half 200, the cooling rate is 6.0~10.0℃ / s. The cooling rate used in this stage is higher than the critical martensitic transformation cooling rate of the two rail steels by 2.1~3.0℃ / s, thereby refining the pearlite lamellar spacing and achieving the goal of increasing the hardness of the heat-affected zone of the rail weld joint. The final cooling temperature in this stage is controlled at 100°C above the martensitic transformation initiation temperature (i.e., 180~230°C) of both types of rail steel to avoid martensite formation due to improper cooling temperature control during the cooling process. Therefore, the end temperature of the zoned controlled cooling is when the surface temperature of the heat-affected zone on both sides of the weld decreases to 400~500°C. For example, the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail will cool to this threshold temperature first due to its faster cooling rate. At this point, the second half of the treatment device 200 can be shut down and the spraying of cooling medium stopped, allowing the heat-affected zone on the heat-treated eutectoid pearlitic rail side of the welded joint to cool with the environment. When the surface temperature of the welded heat-affected zone on the hot-rolled eutectoid pearlitic rail side decreases to 400~500°C, the heating elements of the first half of the treatment device 100 are shut down, and the entire device is dismantled.

[0054] Return to reference Figure 3 In step S2, the welded joint, which has undergone controlled cooling in designated areas, is cooled in air until the surface temperature of the welded joint drops to ambient temperature. The initial cooling temperature for this stage is 400-500°C. During the cooling process, the power input of the first half 100 and the compressed air input of the second half 200 of the processing device are turned off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in air to an ambient temperature of 20-30°C at a cooling rate of approximately 0.2-1.1°C / s. In this invention, when the rail welded joint is cooled in an environment of 20-30°C without any cooling equipment, the cooling rate is approximately 0.2-0.7°C / s. When industrial blowers, electric fans, or other equipment are used to assist in cooling the rail welded joint, the cooling rate can reach 0.8-1.1°C / s.

[0055] This stage employs a cooling rate lower than that of the zoned controlled cooling stage to cool the rail welded joint. The cooling rate in this stage is below the critical cooling rate for the martensitic transformation of the two types of rail steel, to avoid the formation of brittle and harmful martensite structures during cooling. Under the conditions of rapid cooling at high temperatures after welding, the rail welded joint exhibits a certain degree of dynamic undercooling, causing the phase transformation temperature of austenite to pearlite in the non-equilibrium state to shift downwards. Furthermore, as the undercooling increases, the phase transformation temperature gradually decreases. Therefore, in step S2, even with a relatively low initial cooling temperature, the transformation from austenite to pearlite can still occur within the joint.

[0056] The present invention will be further illustrated by the following examples, but the scope of protection of the present invention is not limited thereto.

[0057] The following examples and comparative examples illustrate the methods for hardness testing and metallographic analysis: The post-weld treated rail welded joint was machined into longitudinal hardness test specimens. A HBV-30A hardness tester (Shandong Laizhou Testing Machine Factory) was used to perform longitudinal Vickers hardness testing on the specimens at a distance of 5 mm below the rail head tread, with measuring points spaced 2 mm apart. The measuring points were symmetrically arranged to the left and right sides centered on the weld. The Vickers hardness testing method was performed according to GB / T 4340.1-2009 "Metallic materials - Vickers hardness testing - Part 1: Test methods", using the HV scale. (Refer to...) Figure 2 The sampling method shown is to conduct metallographic examination of rail welded joint metallographic specimens in accordance with GB / T13298-2015 "Metallic Microstructure Examination Method". The metallographic specimens of rail welded joints are etched with 3% nitric acid alcohol solution, and the metallographic structure of rail welded joints is observed using a German Leica MeF3 optical microscope.

[0058] Example 1

[0059] In this embodiment, the hot-rolled eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, 0.04% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1100 MPa and a hardness of 310 HV at room temperature (20°C). The heat-treated eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, 0.04% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1300 MPa and a hardness of 370 HV at room temperature (20~30°C).

[0060] After the upsetting and slugging processes are completed in the moving flash welding process, the 60kg / m steel rail is then subjected to... Figure 4The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1100°C. During cooling, the first half of the device wraps and heats the heat-affected zone (HAZ) on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 5.0°C / s. For the rail head of the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail, the second half of the device sprays cooling medium at a compressed air pressure of 1.0 MPa, cooling it at a rate of 10.0°C / s until the surface temperature of both HAZs drops to 400°C, then proceeds to the next cooling stage. When the left and right sides of the welded area reach the set end temperature, the compressed air input of the second half of the rail profiler and the power input of the first half are sequentially shut off, and the processing device is separated from the rail welded joint. The welded joint is then cooled in the air at a rate of 1.1°C / s until the surface temperature of the welded joint reaches the ambient temperature of 20°C.

[0061] For the welded joints processed by the method and apparatus of this invention, the longitudinal average hardness of the rail welded joint in the 15mm area on the left side of the weld is approximately 341 HV, which is 110% of the average hardness of the corresponding hot-rolled rail base material. The longitudinal average hardness of the rail welded joint in the 15mm area on the right side of the weld is approximately 355 HV, which is 96% of the average hardness of the corresponding heat-treated rail base material. Furthermore, the average hardness difference between the heat-affected zone on the hot-rolled eutectoid pearlitic rail side and the heat-affected zone on the heat-treated eutectoid pearlitic rail side is 14 HV. Simultaneously, the metallographic structure of the heat-affected zones on both sides of the weld is visible pearlite, without martensite or other abnormal structures. Moreover, the pearlite lamellar spacing gradually decreases from left to right, achieving a smooth transition in hardness between the rail base material and the heat-affected zone of the welded joint.

[0062] Example 2

[0063] In this embodiment, the hot-rolled eutectoid pearlitic rail base material contains 0.82% C, 0.80% Si, 1.0% Mn, 0.50% Cr, 0.08% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1180 MPa and a hardness of 350 HV at room temperature (20°C). The heat-treated eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, 0.04% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1300 MPa and a hardness of 370 HV at room temperature (20~30°C).

[0064] After the upsetting and slugging processes are completed in the moving flash welding process, the 68kg / m steel rail is then subjected to... Figure 4The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1100℃. During the cooling process, the first half of the processing device wraps and heats the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 5.0℃ / s. For the rail head on the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail, the second half of the processing device sprays cooling medium at a pressure of 1.0MPa, cooling it at a rate of 10.0℃ / s until the surface temperature of both heat-affected zones drops to 400℃, then proceeds to the next stage of cooling. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiling device and the power input of the first half are sequentially turned off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in the air at a rate of 1.1℃ / s until the surface temperature of the welded joint reaches the ambient temperature of 20℃.

[0065] For the welded joints processed by the method and apparatus of this invention, the longitudinal average hardness of the rail welded joint in the 15mm area on the left side of the weld is about 371 HV, which is 106% of the average hardness of the corresponding hot-rolled rail base material. The longitudinal average hardness of the rail welded joint in the 15mm area on the right side of the weld is about 355 HV, which is 96% of the average hardness of the corresponding heat-treated rail base material. The average hardness of the heat-affected zone on the hot-rolled eutectoid pearlitic rail side differs from that on the heat-affected zone on the heat-treated eutectoid pearlitic rail side by 16 HV. At the same time, the metallographic structure of the rail weld heat-affected zone on both sides of the weld is visible pearlite, without abnormal structures such as martensite.

[0066] Example 3

[0067] In this embodiment, the hot-rolled eutectoid pearlitic rail base material contains 0.82% C, 0.80% Si, 1.0% Mn, 0.50% Cr, 0.08% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1180 MPa and a hardness of 350 HV at room temperature (20°C). The heat-treated eutectoid pearlitic rail base material contains 0.82% C, 0.80% Si, 1.0% Mn, 0.50% Cr, 0.08% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1380 MPa and a hardness of 400 HV at room temperature (20°C).

[0068] After the upsetting and slugging processes are completed during the moving flash welding of 75kg / m steel rails, the steel rails are then subjected to... Figure 4The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1100℃. During the cooling process, the first half of the processing device wraps and heats the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 5.0℃ / s. For the rail head on the heat-affected zone of the heat-treated eutectoid pearlitic rail, the second half of the processing device sprays cooling medium at a pressure of 1.0 MPa, cooling it at a rate of 10.0℃ / s until the surface temperature of both heat-affected zones drops to 400℃, then proceeds to the next cooling stage. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiling device and the power input of the first half are sequentially shut off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in the air at a rate of 0.2℃ / s until the surface temperature of the welded joint reaches the ambient temperature of 30℃.

[0069] For the welded joints processed by the method and apparatus of this invention, the longitudinal average hardness of the rail welded joint in the 15mm area on the left side of the weld is about 371HV, which is 106% of the average hardness of the corresponding hot-rolled rail base material. The longitudinal average hardness of the rail welded joint in the 15mm area on the right side of the weld is about 376HV, which is 94% of the average hardness of the corresponding heat-treated rail base material. The average hardness of the heat-affected zone on the hot-rolled eutectoid pearlitic rail side differs from that on the heat-affected zone on the heat-treated eutectoid pearlitic rail side by 5HV. At the same time, the metallographic structure of the rail weld heat-affected zone on both sides of the weld is visible pearlite, without abnormal structures such as martensite.

[0070] Example 4

[0071] In this embodiment, the hot-rolled eutectoid pearlitic rail base material contains 0.82% C, 0.80% Si, 1.0% Mn, 0.50% Cr, 0.08% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1180 MPa and a hardness of 350 HV at room temperature (20°C). The heat-treated eutectoid pearlitic rail base material contains 0.82% C, 0.80% Si, 1.0% Mn, 0.50% Cr, 0.08% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1380 MPa and a hardness of 400 HV at room temperature (20°C).

[0072] After the upsetting and slugging processes are completed during the moving flash welding of 75kg / m steel rails, the steel rails are then subjected to... Figure 4The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1100℃. During the cooling process, the first half of the processing device wraps and heats the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 3.0℃ / s. For the rail head on the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail, the second half of the processing device sprays cooling medium at a pressure of 0.6MPa, cooling it at a rate of 6.0℃ / s until the surface temperature of both heat-affected zones drops to 500℃, then proceeds to the next stage of cooling. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiling device and the power input of the first half are sequentially turned off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in the air at a rate of 1.1℃ / s until the surface temperature of the welded joint reaches the ambient temperature of 25℃.

[0073] For the welded joints processed by the method and apparatus of this invention, the longitudinal average hardness of the rail welded joint in the 15mm area on the left side of the weld is about 350 HV, which is 100% of the average hardness of the corresponding hot-rolled rail base material. The longitudinal average hardness of the rail welded joint in the 15mm area on the right side of the weld is about 368 HV, which is 92% of the average hardness of the corresponding heat-treated rail base material. The average hardness difference between the heat-affected zone on the hot-rolled eutectoid pearlitic rail side and the heat-affected zone on the heat-treated eutectoid pearlitic rail side is 18 HV. At the same time, the metallographic structure of the rail weld heat-affected zone on both sides of the weld is visible pearlite, without abnormal structures such as martensite.

[0074] Example 5

[0075] In this embodiment, the hot-rolled eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, 0.04% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1100 MPa and a hardness of 310 HV at room temperature (20°C). The heat-treated eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, 0.04% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1300 MPa and a hardness of 370 HV at room temperature (20°C).

[0076] After the upsetting and slugging processes are completed in the moving flash welding process, the 60kg / m steel rail is then subjected to... Figure 4The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1000℃. During the cooling process, the first half of the processing device wraps and heats the heat-affected zone (HAZ) on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 3.0℃ / s. For the rail head on the HAZ of the heat-treated eutectoid pearlitic rail, the second half of the processing device sprays cooling medium at a pressure of 0.6MPa, cooling it at a rate of 6.0℃ / s until the surface temperature of both HAZs drops to 500℃, then proceeds to the next cooling stage. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiler and the power input of the first half are sequentially shut off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in the air at a rate of 0.8℃ / s until the surface temperature of the welded joint reaches the ambient temperature of 20℃.

[0077] For the welded joints processed by the method and apparatus of the present invention, the longitudinal average hardness of the rail welded joint in the 15mm area on the left side of the weld is about 335HV, which is 108% of the average hardness of the corresponding hot-rolled rail base material. The longitudinal average hardness of the rail welded joint in the 15mm area on the right side of the weld is about 344HV, which is 93% of the average hardness of the corresponding heat-treated rail base material. The average hardness of the heat-affected zone on the hot-rolled eutectoid pearlitic rail side differs from that on the heat-affected zone on the heat-treated eutectoid pearlitic rail side by 9HV. At the same time, the metallographic structure of the heat-affected zones on both sides of the weld is visible pearlite, without abnormal structures such as martensite.

[0078] Example 6

[0079] In this embodiment, the hot-rolled eutectoid pearlitic rail base material contains 0.78% C, 0.70% Si, 0.80% Mn, 0.40% Cr, 0.05% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1130 MPa and a hardness of 326 HV at room temperature (20°C). The heat-treated eutectoid pearlitic rail base material contains 0.80% C, 0.70% Si, 0.90% Mn, 0.40% Cr, 0.06% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1360 MPa and a hardness of 390 HV at room temperature (20°C).

[0080] After the upsetting and slugging processes are completed in the moving flash welding process, the 60kg / m steel rail is then subjected to... Figure 4The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1000℃. During the cooling process, the first half of the processing device wraps and heats the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 3.0℃ / s. For the rail head on the heat-affected zone of the heat-treated eutectoid pearlitic rail, the second half of the processing device sprays cooling medium at a pressure of 0.6MPa, cooling it at a rate of 6.0℃ / s until the surface temperature of both heat-affected zones drops to 500℃, then proceeds to the next cooling stage. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiling device and the power input of the first half are sequentially shut off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in the air at a rate of 0.5℃ / s until the surface temperature of the welded joint reaches the ambient temperature of 25℃.

[0081] For the welded joints processed by the method and apparatus of this invention, the longitudinal average hardness of the rail welded joint in the 15mm area on the left side of the weld is about 346 HV, which is 106% of the average hardness of the corresponding hot-rolled rail base material. The longitudinal average hardness of the rail welded joint in the 15mm area on the right side of the weld is about 367 HV, which is 94% of the average hardness of the corresponding heat-treated rail base material. The average hardness of the heat-affected zone on the hot-rolled eutectoid pearlitic rail side differs from that on the heat-affected zone on the heat-treated eutectoid pearlitic rail side by 21 HV. At the same time, the metallographic structure of the rail weld heat-affected zone on both sides of the weld is visible pearlite, without abnormal structures such as martensite.

[0082] Comparative Example 1

[0083] In this comparative example, the hot-rolled eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1100 MPa and a hardness of 310 HV at room temperature (20℃). The heat-treated eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1300 MPa and a hardness of 370 HV at room temperature (20~30℃).

[0084] After the upsetting and push-off processes of the moving flash welding process are completed, the welded joint of the rail with a specification of 60kg / m is directly air-cooled to the ambient temperature (20℃) at an residual temperature of 1100℃, thus obtaining the welded joint of this comparative example.

[0085] For the welded joints obtained in this comparative example, the heat-affected zone (HAZ) on one side of the heat-treated eutectoid pearlitic rail exhibits a softened state, with an average hardness of 88% of the average hardness of the corresponding base material. The average hardness of the HAZ on one side of the hot-rolled eutectoid pearlitic rail is 113% of the average hardness of the corresponding base material. Simultaneously, the microstructure of the HAZ on both sides of the weld is pearlitic, without martensite or other abnormal structures. Under this process, the hardness of the HAZ on the hot-rolled eutectoid pearlitic rail side of the rail welded joint is significantly higher than that of the base material, which can easily cause damage to the base material area during service. The significant softening of the HAZ in the heat-treated eutectoid pearlitic rail can easily lead to wear on this side of the rail welded joint during subsequent service, which is detrimental to railway operation safety.

[0086] Comparative Example 2

[0087] In this comparative example, the hot-rolled eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1100 MPa and a hardness of 310 HV at room temperature (20℃). The heat-treated eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1300 MPa and a hardness of 370 HV at room temperature (20~30℃).

[0088] After the upsetting and slugging processes are completed in the moving flash welding process, the 60kg / m steel rail is then subjected to... Figure 4 The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1100°C. During cooling, the first half of the device wraps and heats the heat-affected zone (HAZ) on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 5.0°C / s. For the rail head of the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail, the second half of the device sprays cooling medium at a compressed air pressure of 1.0 MPa, cooling it at a rate of 10.0°C / s until the surface temperature of both HAZs drops to 220°C, then proceeds to the next cooling stage. When the left and right sides of the welded area reach the set end temperature, the compressed air input of the second half of the rail profiler and the power input of the first half are sequentially shut off, and the processing device is separated from the rail welded joint. The welded joint is then cooled in the air at a rate of 0.9°C / s until the surface temperature of the welded joint reaches the ambient temperature of 20°C.

[0089] For the rail welded joints in this comparative example, because the final cooling temperature of the first cooling stage was within the martensitic transformation initiation temperature range of 180~230℃ for both types of rails, and because the cooling rates were higher than the critical cooling rates for martensitic transformation in both types of rails, martensitic structures appeared in the heat-affected zones (HAZs) of both the hot-rolled eutectoid pearlitic rail and the heat-treated eutectoid pearlitic rail. Hardness tests showed that for the rail welded joints in this comparative example, the longitudinal hardness of the rail welded joint within a ±15mm radius of the weld center met 115% and 98% of the average hardness of the corresponding hot-rolled and heat-treated eutectoid pearlitic rail base materials, respectively. Furthermore, the average hardness difference between the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail and the heat-treated eutectoid pearlitic rail was 6 HV. The presence of brittle and hard martensitic structures in the HAZs of both rails on both sides of the weld is detrimental to the service safety of the rail welded joints in railway operations.

[0090] Comparative Example 3

[0091] In this comparative example, the hot-rolled eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1100 MPa and a hardness of 310 HV at room temperature (20℃). The heat-treated eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1300 MPa and a hardness of 370 HV at room temperature (20~30℃).

[0092] After the upsetting and slugging processes are completed in the moving flash welding process, the 60kg / m steel rail is then subjected to... Figure 4The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1100°C. During cooling, the first half of the device wraps and heats the heat-affected zone (HAZ) on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 5.0°C / s. For the rail head of the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail, the second half of the device sprays cooling medium at a compressed air pressure of 1.0 MPa, cooling it at a rate of 10.0°C / s until the surface temperature of both HAZ zones drops to 175°C, then proceeds to the next cooling stage. When the left and right sides of the welded area reach the set end temperature, the compressed air input of the second half of the rail profiler and the power input of the first half are sequentially shut off, and the processing device is separated from the rail welded joint. The welded joint is then cooled in the air at a rate of 1.0°C / s until the surface temperature of the welded joint reaches the ambient temperature of 20°C.

[0093] For the rail welded joints in this comparative example, because the final cooling temperature of the first cooling stage was below the martensitic transformation initiation temperature range of 180-230℃ for both types of rails, and because the cooling rates were higher than the critical cooling rates for martensitic transformation in both types of rails, martensitic structures appeared in the heat-affected zones (HAZs) of both the hot-rolled eutectoid pearlitic rail and the heat-treated eutectoid pearlitic rail. Hardness tests showed that for the rail welded joints in this comparative example, the longitudinal hardness of the rail welded joint within a ±15mm radius of the weld center met 120% and 105% of the average hardness of the corresponding hot-rolled and heat-treated eutectoid pearlitic rail base materials, respectively. Furthermore, the average hardness difference between the heat-affected zones on one side of the hot-rolled eutectoid pearlitic rail and the heat-treated eutectoid pearlitic rail was 18 HV. The presence of brittle and hard martensitic structures in the HAZs on both sides of the weld is detrimental to the service safety of the rail welded joints in railway operations.

[0094] Comparative Example 4

[0095] In this comparative example, the hot-rolled eutectoid pearlitic rail base material contains 0.82% C, 0.80% Si, 1.0% Mn, 0.50% Cr, 0.08% V, with the balance being Fe and unavoidable impurities. The tensile strength of the hot-rolled eutectoid pearlitic rail base material at room temperature (20℃) is 1180 MPa, and the hardness is 350 HV. The heat-treated eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, 0.04% V, with the balance being Fe and unavoidable impurities. The tensile strength of the heat-treated eutectoid pearlitic rail base material at room temperature (20~30℃) is 1300 MPa, and the hardness is 370 HV.

[0096] After the upsetting and slugging processes are completed in the moving flash welding process, the 68kg / m steel rail is then subjected to... Figure 4 The processing device shown performs zoned controlled cooling of a rail welded joint with a residual surface temperature of 1100°C. During cooling, the first half of the processing device wraps around and compensates for the heat-affected zones (HAZs) on both sides of the weld, cooling both sides at a rate of 5.0°C / s until the surface temperature of the HAZs on both sides drops to 400°C, then proceeds to the next cooling stage. When the set end temperature is reached on both sides of the welded area, the power input to the first half of the rail profiler is turned off, and the processing device is separated from the rail welded joint. The welded joint is then cooled in air at a rate of 0.4°C / s until the surface temperature of the welded joint reaches the ambient temperature of 20°C.

[0097] For the rail welded joints in this comparative example, the cooling rate of the heat-affected zone (HAZ) on one side of the heat-treated eutectoid pearlitic rail was relatively low during the controlled cooling phase, resulting in a minimal increase in hardness. Hardness tests showed that the longitudinal average hardness of the rail welded joint within a 15mm area on the left side of the weld was approximately 371 HV, which is 106% of the average hardness of the corresponding hot-rolled rail base material. The longitudinal average hardness of the rail welded joint within a 15mm area on the right side of the weld was approximately 315 HV, which is 85% of the average hardness of the corresponding heat-treated rail base material. The difference in average hardness between the HAZ on the hot-rolled eutectoid pearlitic rail side and the heat-treated eutectoid pearlitic rail side was 56 HV. Furthermore, the microstructure of the HAZ on both sides of the weld was pearlitic, without any abnormal structures such as martensite. The significant difference in average hardness between the heat-affected zone on one side of hot-rolled eutectoid pearlitic steel rails and the heat-treated eutectoid pearlitic steel rails results in a lower average hardness on the heat-treated eutectoid pearlitic steel rail side, which is detrimental to the service safety of rail welded joints in railways.

[0098] Comparative Example 5

[0099] In this comparative example, the hot-rolled eutectoid pearlitic rail base material contains 0.82% C, 0.80% Si, 1.0% Mn, 0.50% Cr, 0.08% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1180 MPa and a hardness of 350 HV at room temperature (20°C). The heat-treated eutectoid pearlitic rail base material contains 0.82% C, 0.80% Si, 1.0% Mn, 0.50% Cr, 0.08% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1380 MPa and a hardness of 400 HV at room temperature (20°C).

[0100] After the upsetting and slugging processes are completed during the moving flash welding of 75kg / m steel rails, the steel rails are then subjected to... Figure 4 The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 900°C. During the cooling process, the first half of the device wraps and heats the heat-affected zone (HAZ) on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 3.0°C / s. For the rail head on the HAZ of the heat-treated eutectoid pearlitic rail, the second half of the device sprays cooling medium at a pressure of 0.6 MPa, cooling it at a rate of 6.0°C / s until the surface temperature of both HAZs drops to 500°C, then proceeds to the next cooling stage. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiler and the power input of the first half are sequentially shut off, and the processing device is separated from the rail welded joint. The welded joint is then cooled in the air at a rate of 1.1°C / s until the surface temperature of the welded joint reaches the ambient temperature of 20°C.

[0101] For the rail welded joint in this comparative example, the surface temperature of the rail welded joint was slightly lower before the start of the controlled cooling stage, resulting in insufficient driving force for pearlite phase transformation during subsequent cooling, insufficient refinement of pearlite lamellar spacing, and insufficient hardness improvement in the heat-affected zones on both sides of the weld. Hardness tests showed that the longitudinal hardness of the rail welded joint within a range of ±15mm from the weld center met 99% and 87% of the average hardness of the corresponding hot-rolled eutectoid pearlitic rail and heat-treated eutectoid pearlitic rail base materials, respectively. Furthermore, the average hardness difference between the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail and the heat-treated eutectoid pearlitic rail was 2HV. Simultaneously, the metallographic structure of the heat-affected zones on both sides of the weld was visible pearlite, without any abnormal structures such as martensite. Because the hardness of the heat-affected zone on both sides of the weld joint of the rail obtained in this comparative example is lower than the average hardness of the base material of the corresponding hot-rolled eutectoid pearlitic rail and heat-treated eutectoid pearlitic rail, especially the heat-treated eutectoid pearlitic rail, the hardness of the heat-affected zone is significantly reduced, which makes it easy to cause damage in the weld heat-affected zone, which is not conducive to its service safety in railways.

[0102] Comparative Example 6

[0103] In this comparative example, the hot-rolled eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1100 MPa and a hardness of 310 HV at room temperature (20℃). The heat-treated eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1300 MPa and a hardness of 370 HV at room temperature (20~30℃).

[0104] After the upsetting and slugging processes are completed in the moving flash welding process, the 60kg / m steel rail is then subjected to... Figure 4 The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1100°C. During cooling, the first half of the device wraps and heats the heat-affected zone (HAZ) on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 2.0°C / s. For the rail head of the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail, the second half of the device sprays cooling medium at a compressed air pressure of 0.6 MPa, cooling it at a rate of 6.0°C / s until the surface temperature of both HAZs drops to 500°C, then proceeds to the next cooling stage. When the left and right sides of the welded area reach the set end temperature, the compressed air input of the second half of the rail profiler and the power input of the first half are sequentially shut off, and the processing device is separated from the rail welded joint. The welded joint is then cooled in the air at a rate of 1.1°C / s until the surface temperature of the welded joint reaches the ambient temperature of 20°C.

[0105] For the rail welded joint in this comparative example, the longitudinal hardness of the rail welded joint within a range of ±15mm from the weld center meets 99% and 93% of the average hardness of the corresponding hot-rolled eutectoid pearlitic rail and heat-treated eutectoid pearlitic rail base materials, respectively. Furthermore, the average hardness of the heat-affected zone on the heat-treated eutectoid pearlitic rail side is 37 HV higher than that on the heat-affected zone on the hot-rolled eutectoid pearlitic rail side. Simultaneously, the microstructure of the heat-affected zones on both sides of the weld is visible pearlite, without any abnormal structures such as martensite. Since the average hardness of the heat-affected zone on the hot-rolled eutectoid pearlitic rail side of the rail welded joint obtained in this comparative example is significantly lower than that on the heat-affected zone on the heat-treated eutectoid pearlitic rail side, the rail welded joint obtained by this method is detrimental to the service safety of the railway.

[0106] Comparative Example 7

[0107] In this comparative example, the hot-rolled eutectoid pearlitic rail base material contains 0.78% C, 0.70% Si, 0.80% Mn, 0.40% Cr, and 0.05% V, with the balance being Fe and unavoidable impurities. The tensile strength of the hot-rolled eutectoid pearlitic rail base material at room temperature (20℃) is 1130 MPa, and its hardness is 326 HV. The heat-treated eutectoid pearlitic rail base material contains 0.80% C, 0.70% Si, 0.90% Mn, 0.40% Cr, and 0.06% V, with the balance being Fe and unavoidable impurities. The tensile strength of the heat-treated eutectoid pearlitic rail base material at room temperature (20℃) is 1360 MPa, and its hardness is 390 HV.

[0108] After the upsetting and slugging processes are completed in the moving flash welding process, the 60kg / m steel rail is then subjected to... Figure 4 The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1000℃. During the cooling process, the first half of the processing device wraps and heats the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 3.0℃ / s. For the rail head on the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail, the second half of the processing device sprays cooling medium at a pressure of 0.6MPa, cooling it at a rate of 6.0℃ / s until the surface temperature of both heat-affected zones drops to 550℃, then proceeds to the next stage of cooling. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiling device and the power input of the first half are sequentially turned off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in the air at a rate of 1.0℃ / s until the surface temperature of the welded joint reaches the ambient temperature of 20℃.

[0109] For the rail welded joint in this comparative example, the higher final cooling temperature during the controlled cooling phase resulted in insufficient refinement of the pearlitic structure and a less significant increase in hardness. Hardness tests showed that the longitudinal hardness of the rail welded joint within a ±15mm radius of the weld center was 98% and 89% of the average hardness of the corresponding hot-rolled eutectoid pearlitic rail and heat-treated eutectoid pearlitic rail base materials, respectively. Furthermore, the average hardness of the heat-affected zone (HAZ) on the heat-treated eutectoid pearlitic rail side was 28 HV higher than that on the hot-rolled eutectoid pearlitic rail side. Simultaneously, the microstructure of the HAZ on both sides of the weld was visible pearlite, without any abnormal structures such as martensite. Because the hardness of the HAZ on both sides of the weld of the rail welded joint obtained in this comparative example is lower than the average hardness of the corresponding hot-rolled and heat-treated eutectoid pearlitic rail base materials, damage is likely to occur in the weld HAZ. Therefore, this comparative example is not conducive to the safe service of the rail welded joint in railways.

[0110] Comparative Example 8

[0111] In this comparative example, the hot-rolled eutectoid pearlitic rail base material contains 0.78% C, 0.70% Si, 0.80% Mn, 0.40% Cr, and 0.05% V, with the balance being Fe and unavoidable impurities. The tensile strength of the hot-rolled eutectoid pearlitic rail base material at room temperature (20℃) is 1130 MPa, and its hardness is 326 HV. The heat-treated eutectoid pearlitic rail base material contains 0.80% C, 0.70% Si, 0.90% Mn, 0.40% Cr, and 0.06% V, with the balance being Fe and unavoidable impurities. The tensile strength of the heat-treated eutectoid pearlitic rail base material at room temperature (20℃) is 1360 MPa, and its hardness is 390 HV.

[0112] After the upsetting and slugging processes are completed in the moving flash welding process, the 60kg / m steel rail is then subjected to... Figure 4 The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1000℃. During the cooling process, the first half of the processing device wraps and heats the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 3.0℃ / s. For the rail head on the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail, the second half of the processing device sprays cooling medium with compressed air at a pressure of 1.2MPa, cooling it at a rate of 12.0℃ / s until the surface temperature of both heat-affected zones drops to 500℃, then proceeds to the next stage of cooling. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiling device and the power input of the first half are sequentially turned off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in the air at a rate of 0.3℃ / s until the surface temperature of the welded joint reaches the ambient temperature of 20℃.

[0113] For the rail welded joint in this comparative example, the longitudinal average hardness of the rail welded joint in the 15mm area on the left side of the weld is about 346 HV, which is 106% of the average hardness of the corresponding hot-rolled rail base material. The longitudinal average hardness of the rail welded joint in the 15mm area on the right side of the weld is about 394 HV, which is 101% of the average hardness of the corresponding heat-treated rail base material. The average hardness of the heat-affected zone on the hot-rolled eutectoid pearlitic rail side is 48 HV lower than that on the heat-affected zone on the heat-treated eutectoid pearlitic rail side. The large difference in average hardness between the heat-affected zones on both sides of the weld is not conducive to the service safety of the railway.

[0114] Comparative Example 9

[0115] In this comparative example, the hot-rolled eutectoid pearlitic steel rail base material contains 0.88% C, 0.80% Si, 1.0% Mn, 0.50% Cr, and 0.08% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic steel rail base material has a tensile strength of 1250 MPa and a hardness of 375 HV at room temperature (20°C). The heat-treated eutectoid pearlitic steel rail base material contains 0.82% C, 0.80% Si, 1.0% Mn, 0.50% Cr, and 0.08% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic steel rail base material has a tensile strength of 1380 MPa and a hardness of 400 HV at room temperature (20°C).

[0116] After the upsetting and slugging processes are completed during the moving flash welding of 75kg / m steel rails, the steel rails are then subjected to... Figure 4 The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1100℃. During the cooling process, the first half of the processing device wraps and heats the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 5.0℃ / s. For the rail head on the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail, the second half of the processing device sprays cooling medium at a pressure of 1.0MPa, cooling it at a rate of 10.0℃ / s until the surface temperature of both heat-affected zones drops to 400℃, then proceeds to the next stage of cooling. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiling device and the power input of the first half are sequentially turned off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in the air at a rate of 1.1℃ / s until the surface temperature of the welded joint reaches the ambient temperature of 20℃.

[0117] For the rail welded joint in this comparative example, the longitudinal hardness of the rail welded joint within a range of ±15mm from the weld center meets 112% and 94% of the average hardness of the corresponding hot-rolled eutectoid pearlitic rail and heat-treated eutectoid pearlitic rail base materials, respectively. Furthermore, the average hardness of the heat-affected zone (HAZ) on the hot-rolled eutectoid pearlitic rail side is 44 HV higher than that on the heat-treated eutectoid pearlitic rail side. Simultaneously, the microstructure of the HAZ on both sides of the weld is pearlitic, without any abnormal structures such as martensite. However, due to the excessively high C content in the HAZ on the hot-rolled eutectoid pearlitic rail side of the rail welded joint obtained in this comparative example, its average hardness is significantly higher than that of the heat-treated eutectoid pearlitic rail HAZ. This large difference in hardness between the HAZ on both sides of the weld is detrimental to the service safety of the railway.

[0118] Comparative Example 10

[0119] In this comparative example, the hot-rolled eutectoid pearlitic rail base material contains 0.75% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The hot-rolled eutectoid pearlitic rail base material has a tensile strength of 1100 MPa and a hardness of 310 HV at room temperature (20℃). The heat-treated eutectoid pearlitic rail base material contains 0.70% C, 0.50% Si, 0.70% Mn, 0.30% Cr, and 0.04% V, with the balance being Fe and unavoidable impurities. The heat-treated eutectoid pearlitic rail base material has a tensile strength of 1220 MPa and a hardness of 340 HV at room temperature (20~30℃).

[0120] After the upsetting and slugging processes are completed in the moving flash welding process, the 60kg / m steel rail is then subjected to... Figure 4 The processing device shown performs zoned controlled cooling of rail welded joints with a residual surface temperature of 1000℃. During the cooling process, the first half of the processing device wraps and heats the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail, cooling it at a rate of 5.0℃ / s. For the rail head on the heat-affected zone of the heat-treated eutectoid pearlitic rail, the second half of the processing device sprays cooling medium with compressed air at a pressure of 1.0MPa, cooling it at a rate of 10.0℃ / s until the surface temperature of both heat-affected zones drops to 400℃, then proceeds to the next stage of cooling. When the left and right sides of the welding area reach the set end temperature, the compressed air input of the second half of the rail profiling device and the power input of the first half are sequentially turned off, and the processing device is separated from the rail welded joint, allowing the welded joint to cool in the air at a rate of 1.1℃ / s until the surface temperature of the welded joint reaches the ambient temperature of 20℃.

[0121] For the rail welded joint in this comparative example, the longitudinal hardness of the rail welded joint within a range of ±15mm from the weld center meets 110% and 91% of the average hardness of the corresponding hot-rolled eutectoid pearlitic rail and heat-treated eutectoid pearlitic rail base materials, respectively. Furthermore, the average hardness of the heat-affected zone on the hot-rolled eutectoid pearlitic rail side is 32 HV higher than that on the heat-treated eutectoid pearlitic rail side. Simultaneously, the microstructure of the heat-affected zones on both sides of the weld is visible pearlite, without any abnormal structures such as martensite. However, due to the low C content of the heat-treated eutectoid pearlitic rail base material in this comparative example, the average hardness of the heat-affected zone on the heat-treated eutectoid pearlitic rail side of the resulting rail welded joint is lower, and the hardness difference between the heat-affected zones on both sides of the weld is significant, which is detrimental to the service safety of the welded joint in railway operations.

[0122] By comparing the longitudinal hardness of the rail head tread and the metallographic structure of the welded joint obtained from various embodiments and comparative examples, it can be seen that the processing method provided by this invention can ensure that the heat-affected zone structure on both sides of the rail weld joint is only pearlite, without abnormal structures such as martensite. Simultaneously, the longitudinal hardness of the rail weld joint within ±15mm of the weld center can reach 100-110% and 90-100% of the average hardness of the base material of the corresponding hot-rolled eutectoid pearlite rail and heat-treated eutectoid pearlite rail, respectively. The hardness difference between the heat-affected zones on both sides of the rail weld joint is within 21 HV, which helps to reduce rail weld joint damage caused by excessive hardness differences between the heat-affected zones on both sides of the weld and the base material, or excessive hardness differences between the heat-affected zones on both sides of the weld, thus ensuring railway operation safety.

[0123] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for treating the welded joint between a hot-rolled steel rail and a heat-treated steel rail, characterized in that, Includes the following steps: Step S1: The hot-state welded joint formed by welding hot-rolled eutectoid pearlitic steel rail and heat-treated eutectoid pearlitic steel rail is subjected to zoned controlled cooling. The heat-affected zone on the hot-rolled eutectoid pearlitic steel rail side is cooled slowly at a low cooling rate under the condition of heating temperature compensation, while the heat-affected zone on the heat-treated eutectoid pearlitic steel rail side is cooled accelerated under the action of cooling medium. The welded joint is subjected to the zoned controlled cooling until the surface temperature of the welded joint is reduced to the first temperature threshold. Step S2: Cool the welded joint that has undergone the controlled cooling in the sub-regions in an air environment until the surface temperature of the welded joint drops to the ambient temperature; The slow cooling rate is 3.0~5.0℃ / s, and the accelerated cooling rate is 6.0~10.0℃ / s; The boundary line between the heat-affected zone on one side of the hot-rolled eutectoid pearlitic steel rail and the heat-affected zone on one side of the heat-treated eutectoid pearlitic steel rail is the weld center of the welded joint. The tensile strength of the hot-rolled eutectoid pearlitic steel rail base material at room temperature is 1100~1180MPa, and the hardness is 310~350HV. The tensile strength of the heat-treated eutectoid pearlitic steel rail base material at room temperature is 1300~1380MPa, and the hardness is 370~400HV. The first temperature threshold is 400~500℃, and the start temperature of the controlled cooling is 1000~1100℃.

2. The method according to claim 1, characterized in that, The components of both the hot-rolled eutectoid pearlitic steel rail and the heat-treated eutectoid pearlitic steel rail are selected from the following range by weight percentage: 0.75%~0.82% C, 0.50%~0.80% Si, 0.70%~1.0% Mn, 0.30%~0.50% Cr, 0.04%~0.08% V, with the balance being Fe and unavoidable impurities.

3. The method according to claim 1, characterized in that, The processing method results in the hardness of the heat-affected zone on one side of the hot-rolled eutectoid pearlitic rail being 1.0 to 1.1 times the hardness of the base material of the hot-rolled eutectoid pearlitic rail, and the hardness of the heat-affected zone on one side of the heat-treated eutectoid pearlitic rail being 0.9 to 1.0 times the hardness of the base material of the heat-treated eutectoid pearlitic rail.

4. A treatment apparatus for welded joints of hot-rolled steel rails and heat-treated steel rails, the apparatus being used to implement zoned controlled cooling in the treatment method according to any one of claims 1-3, characterized in that, include: The first half has a first outer shell resembling the shape of a steel rail. The inner wall of the first outer shell is provided with multiple heating elements. Inside each heating element is an insulation layer resembling the shape of a steel rail, and the insulation layer is connected to the outer shell. The second half has a second outer shell similar in shape to the rail head of the rail. The second outer shell forms a chamber for containing a cooling medium, and the side wall of the chamber near the rail head tread has cooling medium injection holes.

5. The treatment device for the welded joint of hot-rolled steel rail and heat-treated steel rail according to claim 4, characterized in that, The first half includes a front portion and a rear portion that are rotatably connected together, the front portion and the rear portion being symmetrically arranged and pivotally connected together at the top.

6. The treatment device for the welded joint of hot-rolled steel rail and heat-treated steel rail according to claim 5, characterized in that, Both the front and rear portions include a rail head cover, a rail web cover, and a rail bottom cover. The rail head cover provides more heat than the rail web cover and the rail bottom cover.

7. The treatment device for the welded joint of hot-rolled steel rail and heat-treated steel rail according to claim 4, characterized in that, During use, the insulation layer is attached to the outer surface of the rail.

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