A welding method for improving the performance of rail joints

Abstract

The application discloses a welding method for improving the performance of a rail joint, and the welding method is realized by moving flash welding of a rail, and the moving flash welding process is carried out in a vacuum state, and the vacuum degree is below 1 Pa; the moving flash welding comprises a flash flattening stage, a preheating stage, a melting stage, a upsetting stage and a nub pushing stage in sequence; wherein the flash flattening voltage of the flash flattening stage is 360-450 V, and the flash flattening time is controlled to be 10-40 s. The welding method can obtain a new method of a low-defect high-performance rail flash welded joint by welding process control in a vacuum state, can avoid the formation of defects such as gray spots and incomplete welding of the rail flash welded joint, the other organization performance of the joint meets TB / T 1632 and is significantly improved, and the defects of the rail flash welded joint are greatly reduced and the comprehensive performance is improved.

Description

Technical Field

[0001] This invention relates to the field of rail smelting technology, and more specifically to a welding method for improving the performance of rail joints. Background Technology

[0002] With the rapid development of the world, rail transit is also evolving towards higher speeds, heavier loads, and greater comfort and safety. Pearlitic steel rails, due to their excellent wear resistance, strength, and toughness, are widely used in railway tracks. Flash welding is currently the most widely used rail welding method. However, during the flash welding process, welding defects are inevitable in the welded joint. Among these, ash spots and incomplete fusion are the most common defects. The presence of ash spots and incomplete fusion defects reduces the mechanical properties of the rail welded joint, seriously affecting the service life of the rail and the safety of railway operation. At the same time, appropriate welding processes and post-weld heat treatment processes are also crucial for obtaining high-quality flash welded joints.

[0003] Studies have found that inclusion formation during welding is the root cause of defects such as ash spots and incomplete fusion. Even with a well-suited welding process, oxygen inevitably enters the weld face during flash welding, forming inclusions. These inclusions not only cause defects like ash spots and incomplete fusion, but their presence also degrades joint performance (because the properties of inclusions differ significantly from the base material, disrupting the continuity of the base material and leading to a decline in its properties). Therefore, preventing inclusion formation during welding is crucial for obtaining high-quality welded joints. Summary of the Invention

[0004] The purpose of this invention is to provide a welding method for improving the performance of rail joints. This method involves controlling the welding process under vacuum conditions to obtain low-defect, high-performance flash-welded rail joints. Using this method, defects such as gray spots and incomplete fusion in the flash-welded rail joints can be avoided. Other microstructures and properties of the joint meet TB / T 1632 and are significantly improved, greatly reducing defects in the flash-welded rail joints and enhancing overall performance.

[0005] To achieve the above-mentioned objectives, this invention provides a welding method for improving the performance of rail joints. The welding method involves moving flash welding of the rail, which is performed under vacuum conditions with a vacuum level below 1 Pa. The moving flash welding process sequentially includes a flash leveling stage, a preheating stage, a burning stage, an upsetting stage, and a stub removal stage. The flash leveling voltage in the flash leveling stage is 360–450 V, and the flash leveling time is controlled between 10 and 40 seconds.

[0006] This invention creates a vacuum chamber by evacuating space, and places the welding machine inside the vacuum chamber, allowing the welding process of the rails to take place within the vacuum chamber. As a specific embodiment, the vacuum chamber of this invention is illustrated below. Figure 1 As shown.

[0007] The aforementioned vacuum chamber is made of stainless steel, which not only creates a vacuum environment but also isolates splashed high-temperature flashing droplets. A door is provided in the vacuum chamber for the steel rails to enter and exit; the door's closing position requires a resilient sealing ring, and an observation window is provided on the door. This window uses high-temperature and impact-resistant glass. After preparation, vacuuming begins, reducing the pressure to below 1 Pa. Too high a vacuum level requires a long time, and once the pressure drops to 1 Pa, the oxygen concentration is extremely low. With appropriate processing, this can significantly reduce or even eliminate defects. Once the required vacuum level is achieved, moving flash welding can begin.

[0008] In this invention, the end faces of two rails to be welded gradually approach each other under the action of electrode clamping. Since the local microscopic surface of the rail to be welded is uneven, the local micro-protrusions first make contact and short-circuit during the approach process, generating a large current and melting and bursting the contact point, thereby producing a flash. Through the continuous forward and backward movement of the rails to be welded, flashes are generated, removing impurities, stains and local unevenness from the end face to be welded, and obtaining a good welding end face, hence the name "flash flattening". At the same time, the rails are heated.

[0009] According to the welding method for improving the performance of rail joints of the present invention, preferably, the preheating voltage of the preheating stage is 300-400V and the preheating time is 40-110s.

[0010] In this invention, the preheating stage of moving flash welding involves repeatedly short-circuiting the two rails to be welded to heat them to a certain temperature and create a suitable temperature gradient, preparing them for subsequent stages. The preheating stage requires a stable flash process to preheat the rails, therefore the voltage is relatively lower than in the flash leveling stage.

[0011] According to the welding method for improving the performance of rail joints of the present invention, preferably, the burning stage includes: applying a voltage of 360-450V to the pearlitic rail to be welded for burning, and the burning time is 10-50s.

[0012] In this invention, the burning stage of the moving flash welding process generates a localized high-pressure protective atmosphere by producing an intense and stable flash at high voltage. Simultaneously, the splashed molten metal droplets reduce the surrounding oxygen concentration. This combined effect prevents oxidation of the metal end face. Furthermore, a vacuuming operation is performed before welding, resulting in an extremely low oxygen concentration in the welding area, significantly reducing or even eliminating defects such as ash spots and incomplete welds. A schematic diagram of the burning stage is shown below. Figure 2As shown. The firing process designed in this invention can produce intense and stable flashes, further improving the performance of the rail.

[0013] According to the welding method for improving the performance of rail joints of the present invention, preferably, the upsetting amount in the upsetting stage is 13-20 mm.

[0014] In this invention, the upsetting stage of moving flash welding involves rapidly bringing the rails closer to contact at a suitable speed at the end of the melting process, applying force to expel the liquid metal and potential defects generated during the flash process from the end face, while simultaneously causing sufficient deformation at the joint to obtain a high-quality welded joint with atomic bonding. The upsetting amount designed in this invention can further improve the quality of the welded joint.

[0015] According to the welding method for improving the performance of rail joints of the present invention, preferably, the weld bead generated during the upsetting stage is removed by a cutting tool, wherein the cutting tool is a profile cutter with the same outline as the rail.

[0016] The above-mentioned moving flash welding stage refers to the process after upsetting, where a contour cutter with the same shape as the rail moves longitudinally along the rail under the action of force to remove the weld beads ejected during the upsetting stage.

[0017] According to the welding method for improving the performance of rail joints of the present invention, preferably, the moving flash welding further includes a heat treatment stage, in which the welded rail is naturally cooled to room temperature, and then the entire cross-section of the welded joint is induction heated by an induction coil.

[0018] According to the welding method for improving the performance of rail joints of the present invention, preferably, the induction heating is stopped after reaching 900-980°C, and then air cooling is adopted.

[0019] According to the welding method for improving the performance of rail joints of the present invention, preferably, the cooling device for air spraying is an air spray box with a width of 90-180mm. The air spray box blows air onto the upper surface and sides of the rail head. The air spray box is 15-60mm away from the rail surface, and the air spray pressure is 0.05-0.5MPa. Air spraying is stopped after the temperature drops below 500℃, followed by natural cooling. A schematic diagram of the air spraying cooling stage is shown below. Figure 3 As shown.

[0020] According to the welding method for improving the performance of rail joints of the present invention, preferably, the rail is a pearlitic rail, and the mass fraction of each element in the pearlitic rail is as follows: C 0.55% to 0.80%, Si 0.10% to 0.90%, Mn 0.55% to 1.20%, V ≤ 0.20%, S ≤ 0.008%, Al ≤ 0.004%, O ≤ 0.003%, with the balance being Fe and unavoidable impurities.

[0021] According to the welding method for improving the performance of rail joints of the present invention, preferably, the pearlitic rail is a heat-treated pearlitic rail with a strength of 60 kg / m.

[0022] The beneficial effects of this invention are: The purpose of this invention is to provide a welding method for improving the performance of rail joints. This method achieves low-defect, high-performance flash welded rail joints by controlling the welding process under vacuum conditions. Using this method, defects such as gray spots and incomplete fusion in the flash welded joints can be avoided. Other microstructures and properties of the joint meet TB / T 1632 and are significantly improved, greatly reducing defects in the flash welded rail joints and enhancing overall performance.

[0023] A better technical solution, combined with a specific welding process, can further improve the performance of the rail. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a vacuum chamber for a welding method to improve the performance of rail joints according to the present invention. Figure 2 This is a schematic diagram of the melting stage of a welding method for improving the performance of rail joints according to the present invention. Figure 3 This is a schematic diagram of the air-cooling stage of a welding method for improving the performance of rail joints according to the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0027] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0028] Performance testing: Analysis of ash spot defects, microstructure, and properties of welded joints. Microstructure and property testing and analysis refer to standard TB / T 1632. The area of ​​ash spot defects is statistically analyzed by drop hammer fracture surface and expressed as the sum of the areas of all ash spots on the fracture surface. Incomplete welding is detected by metallographic method. The rail is cut along the weld, and the entire cross-section is taken for metallographic analysis. After polishing and etching with 4% nitric acid alcohol, it is observed and analyzed by metallographic microscope. Hardness is represented by cross-sectional hardness (HRC, with two hardness points 5mm apart). The microstructure is sampled at standard locations, etched with 4% nitric acid alcohol, and observed and analyzed by metallographic microscope.

[0029] In the following embodiments and comparative examples, the welding machine and the rail are placed in a vacuum chamber for welding operations, and the vacuum chamber can be evacuated.

[0030] Example 1 In this embodiment of the pearlitic steel rail: the mass fraction of C is 0.75%; the mass fraction of Si is 0.53%; the mass fraction of Mn is 0.95%; the mass fraction of V is 0.004%; the mass fraction of S is 0.004%; the mass fraction of Al is 0.002%; and the mass fraction of O is 0.003%.

[0031] The aforementioned rails are connected by moving flash welding. First, the end face and web of the rail to be welded are ground. After grinding, the rail is assembled and clamped on the welding machine in the vacuum chamber. Then, the vacuum chamber is evacuated. Once the pressure drops below 1 Pa, moving flash welding can be performed.

[0032] The aforementioned mobile flash welding process consists of five stages: flash leveling, preheating, melting, upsetting, and stub removal. The flash leveling stage lasts 20 seconds at 405V; the preheating stage lasts 80 seconds at 350V; the melting stage lasts 23 seconds at 390V; and the upsetting stage involves an upsetting depth of 16mm. After the welding process is completed and the welded joint has cooled naturally to room temperature, an induction coil shaped like a rail is used to induction heat the entire cross-section of the flash welded rail joint using electromagnetic induction. Once the heating temperature reaches 950℃, the heating device is immediately removed, and a 120mm wide air jet box is used to blow air onto the upper and side surfaces of the rail head. The air jet box is 40mm away from the rail surface, and the air pressure is 0.25MPa. Air jetting is stopped once the air temperature drops to 450℃, and the rail head is allowed to cool naturally.

[0033] The welded joints obtained using the above method were analyzed for incomplete weld defects, ash spots, microstructure, and properties according to the standard TB / T 1632. Ash spot area was statistically analyzed using drop hammer fracture surface analysis. Incomplete welds were detected using metallographic methods. Hardness was represented by cross-sectional hardness (HRC, with hardness test positions spaced 5 mm apart). The microstructure was analyzed using a metallographic microscope after etching with 4% nitric acid alcohol. Through vacuum treatment and appropriate welding and post-weld heat treatment process control, no ash spots or incomplete weld defects were found in the flash welded joints of the rails. The KU2 was 14.5 J, and the average hardness of the welded joint cross-section was H0.05. J And the average hardness H of the base material p The ratio is 0.96, with no abnormal structures such as martensite and bainite, eliminating gray spots and unwelded defects. The microstructure and properties meet the requirements of the iron standard, while the performance is greatly improved, significantly increasing the service life and driving safety of the flash welded joint.

[0034] Example 2 In this embodiment of the pearlitic steel rail: the mass fraction of C is 0.75%; the mass fraction of Si is 0.53%; the mass fraction of Mn is 0.95%; the mass fraction of V is 0.004%; the mass fraction of S is 0.004%; the mass fraction of Al is 0.002%; and the mass fraction of O is 0.003%.

[0035] The aforementioned rails are connected by moving flash welding. First, the end face and web of the rail to be welded are ground. After grinding, the rails are assembled and clamped. Then, the vacuum chamber is evacuated. Once the pressure drops below 1 Pa, moving flash welding can be performed.

[0036] The aforementioned mobile flash welding process consists of five stages: flash leveling, preheating, melting, upsetting, and stub removal. The flash leveling stage lasts 20 seconds at 405V; the preheating stage lasts 80 seconds at 350V; the melting stage lasts 23 seconds at 380V; and the upsetting stage involves an upsetting depth of 15mm. After the welding process, once the welded joint has cooled naturally to room temperature, an induction coil shaped like a rail is used to induction heat the entire cross-section of the flash welded rail joint using electromagnetic induction. When the heating temperature reaches 980℃, the heating device is immediately removed, and a 120mm wide air jet box is used to blow air onto the upper and side surfaces of the rail head. The air jet box is 36mm away from the rail surface, and the air pressure is 0.22MPa. Air jetting is stopped once the air temperature reaches 450℃, and the rail head is allowed to cool naturally.

[0037] The welded joints obtained using the above method were analyzed for incomplete weld defects, ash spots, microstructure, and properties in accordance with the standard TB / T 1632. Ash spot area was statistically analyzed using drop hammer fracture surface analysis. Incomplete welds were detected using metallographic methods. Hardness was represented by cross-sectional hardness (HRC, with hardness test positions spaced 5 mm apart). The microstructure was analyzed using a metallographic microscope after etching with 4% nitric acid alcohol. Through vacuum treatment and appropriate welding and post-weld heat treatment process control, no ash spots or incomplete weld defects were found in the flash welded joints of the rails. The KU2 was 13.9 J, and the average hardness of the welded joint cross-section was H0.05. J And the average hardness H of the base material p The ratio is 0.95, with no abnormal structures such as martensite and bainite, eliminating gray spots and incomplete welding defects. The microstructure and properties meet the requirements of the iron standard, while the performance is greatly improved, significantly increasing the service life and driving safety of the flash welded joint.

[0038] Example 3 In this embodiment of the pearlitic steel rail: the mass fraction of C is 0.75%; the mass fraction of Si is 0.53%; the mass fraction of Mn is 0.95%; the mass fraction of V is 0.004%; the mass fraction of S is 0.004%; the mass fraction of Al is 0.002%; and the mass fraction of O is 0.003%.

[0039] The aforementioned rails are connected by moving flash welding. First, the end face and web of the rail to be welded are ground. After grinding, the rails are assembled and clamped. Then, the vacuum chamber is evacuated. Once the pressure drops below 1 Pa, moving flash welding can be performed.

[0040] The aforementioned mobile flash welding process consists of five stages: flash leveling, preheating, melting, upsetting, and stub removal. The flash leveling stage lasts 20 seconds at 395V; the preheating stage lasts 80 seconds at 350V; the melting stage lasts 23 seconds at 390V; and the upsetting stage involves an upsetting depth of 16mm. After the welding process is completed and the welded joint has cooled naturally to room temperature, an induction coil shaped like a rail is used to induction heat the entire cross-section of the flash welded rail joint using electromagnetic induction. Once the heating temperature reaches 950℃, the heating device is immediately removed, and a 120mm wide air jet box is used to blow air onto the upper and side surfaces of the rail head. The air jet box is 50mm away from the rail surface, and the air pressure is 0.35MPa. Air jetting is stopped after the air cools to 450℃, and the rail head is allowed to cool naturally.

[0041] The welded joints obtained using the above method were analyzed for incomplete weld defects, ash spots, microstructure, and properties according to the standard TB / T 1632. Ash spot area was statistically analyzed using drop hammer fracture surface analysis. Incomplete welds were detected using metallographic methods. Hardness was represented by cross-sectional hardness (HRC, with hardness test positions spaced 5 mm apart). The microstructure was analyzed using a metallographic microscope after etching with 4% nitric acid alcohol. Through vacuum treatment and appropriate welding and post-weld heat treatment process control, no ash spots or incomplete weld defects were found in the flash welded joints of the rails. The KU2 was 13.6 J, and the average hardness of the welded joint cross-section was H0.05. J And the average hardness H of the base material p The ratio is 0.95, with no abnormal structures such as martensite and bainite, eliminating gray spots and unwelded defects. The microstructure and properties meet the requirements of the iron standard while the performance is greatly improved, significantly increasing the service life and driving safety of the flash welded joint.

[0042] Comparative Example 1 In the pearlitic steel rail of this comparative example: the mass fraction of C is 0.75%, the mass fraction of Si is 0.53%, the mass fraction of Mn is 0.95%, the mass fraction of V is 0.004%, the mass fraction of S is 0.004%, the mass fraction of Al is 0.002%, and the mass fraction of O is 0.003%.

[0043] The aforementioned rails are connected by moving flash welding. First, the end face and web of the rail to be welded are ground. After grinding, the rails are assembled and clamped. After all preparations are completed, moving flash welding is performed directly without vacuuming.

[0044] The aforementioned mobile flash welding process consists of five stages: flash leveling, preheating, melting, upsetting, and stub removal. The flash leveling stage lasts 20 seconds at 405V; the preheating stage lasts 80 seconds at 350V; the melting stage lasts 23 seconds at 370V; and the upsetting stage involves an upsetting depth of 10mm. After the welding process, once the welded joint has cooled naturally to room temperature, an induction coil shaped like a rail is used to induction heat the entire cross-section of the flash welded rail joint using electromagnetic induction. When the heating temperature reaches 950℃, the heating device is immediately removed, and a 120mm wide air jet box is used to blow air onto the upper and side surfaces of the rail head. The air jet box is 40mm away from the rail surface, and the air pressure is 0.25MPa. Air jetting is stopped once the air temperature cools to 450℃, and the rail head is allowed to cool naturally.

[0045] The welded joints obtained using the above method were analyzed for incomplete weld defects, gray spot defects, microstructure, and properties according to the standard TB / T 1632. The gray spot area was statistically analyzed using drop hammer fracture surface analysis. Incomplete welds were detected using metallographic methods. Hardness was represented by cross-sectional hardness (HRC, with hardness test positions spaced 5 mm apart). The microstructure was analyzed using a metallographic microscope after etching with 4% nitric acid alcohol. Two gray spots were found in the flash welded joint of the rail, with a total area of ​​16.5 mm². 2 There is one unwelded defect, KU2 is 8.7J, and the average hardness H of the welded joint cross-section is... J And the average hardness H of the base material p The ratio was 0.94, with no abnormal structures such as martensite or bainite, and the area of ​​gray spots increased significantly.

[0046] Comparative Example 2 In the pearlitic steel rail of this comparative example: the mass fraction of C is 0.75%; the mass fraction of Si is 0.53%; the mass fraction of Mn is 0.95%; the mass fraction of V is 0.004%; the mass fraction of S is 0.004%; the mass fraction of Al is 0.002%; and the mass fraction of O is 0.003%.

[0047] The aforementioned rails are connected by moving flash welding. First, the end face and web of the rail to be welded are ground. After grinding, the rails are assembled and clamped. After all preparations are completed, moving flash welding is performed directly without vacuuming.

[0048] The aforementioned mobile flash welding process consists of five stages: flash leveling, preheating, melting, upsetting, and stub removal. The flash leveling stage lasts 20 seconds at 405V; the preheating stage lasts 80 seconds at 350V; the melting stage lasts 23 seconds at 390V; and the upsetting stage involves an upsetting depth of 16mm. After the welding process is completed and the welded joint has cooled naturally to room temperature, an induction coil shaped like a rail is used to induction heat the entire cross-section of the flash welded rail joint using electromagnetic induction. Once the heating temperature reaches 860℃, the heating device is immediately removed, and a 120mm wide air jet box is used to blow air onto the upper and side surfaces of the rail head. The air jet box is 40mm away from the rail surface, and the air pressure is 0.25MPa. Air jetting is stopped after the air cools to 450℃, and the rail head is allowed to cool naturally.

[0049] The welded joints obtained using the above method were analyzed for incomplete weld defects, gray spot defects, microstructure, and properties according to the standard TB / T 1632. The gray spot area was statistically analyzed using drop hammer fracture surface analysis. Incomplete welds were detected using metallographic methods. Hardness was represented by cross-sectional hardness (HRC, with hardness test positions spaced 5 mm apart). The microstructure was analyzed using a metallographic microscope after etching with 4% nitric acid alcohol. Gray spots were found in the flash welded joint of the rail, with a total area of ​​14.9 mm².2 KU2 is 8.6J, and the average hardness H of the welded joint cross-section is... J And the average hardness H of the base material p The ratio is 0.91, the width of the softened zone exceeds 20cm, which does not meet the standard requirements. The area of ​​gray spots has increased significantly, the performance is low, and it does not meet the standard requirements.

[0050] Comparative Example 3 In this embodiment of the pearlitic steel rail: the mass fraction of C is 0.75%, the mass fraction of Si is 0.53%, the mass fraction of Mn is 0.95%, the mass fraction of V is 0.004%, the mass fraction of S is 0.004%, the mass fraction of Al is 0.002%, and the mass fraction of O is 0.003%.

[0051] The aforementioned rails are connected by moving flash welding. First, the end face and web of the rail to be welded are ground. After grinding, the rails are assembled and clamped. After all preparations are completed, moving flash welding is performed directly without vacuuming.

[0052] The aforementioned mobile flash welding process consists of five stages: flash leveling, preheating, melting, upsetting, and stub removal. The flash leveling stage lasts 20 seconds at 405V; the preheating stage lasts 80 seconds at 350V; the melting stage lasts 23 seconds at 390V; and the upsetting stage involves an upsetting depth of 16mm. After the welding process is completed and the welded joint has cooled naturally to room temperature, an induction coil shaped like a rail is used to induction heat the entire cross-section of the flash welded rail joint using electromagnetic induction. Once the heating temperature reaches 950℃, the heating device is immediately removed, and a 120mm wide air jet box is used to blow air onto the upper and side surfaces of the rail head. The air jet box is 40mm away from the rail surface, and the air pressure is 0.6MPa. Air jetting is stopped once the air temperature drops to 450℃, and the rail head is allowed to cool naturally.

[0053] The welded joints obtained using the above method were analyzed for incomplete weld defects, gray spot defects, microstructure, and properties according to the standard TB / T 1632. Gray spot area was statistically analyzed using drop hammer fracture surface analysis. Incomplete welds were detected using metallographic methods. Hardness was represented by cross-sectional hardness (HRC, with hardness test positions spaced 5 mm apart). The microstructure was analyzed using a metallographic microscope after etching with 4% nitric acid alcohol. Three gray spots were found in the flash welded joint of the rail, with a total area of ​​15.8 mm². 2 The KU2 value is 8.3J. The ratio of the average hardness HJ of the welded joint to the average hardness Hp of the base material is 0.95. Numerous martensitic abnormalities were found on the rail head, failing to meet standard requirements. The area of ​​gray spots has increased significantly, and the joint does not meet standard requirements.

[0054] It should be noted that the components or steps in the above embodiments can be interchanged, substituted, added, or deleted. Therefore, the combinations formed by these reasonable permutations and transformations should also fall within the protection scope of the present invention, and the protection scope of the present invention should not be limited to the above embodiments.

[0055] The above are exemplary embodiments disclosed in this invention. The order of the disclosed embodiments is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. However, it should be noted that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of this invention (including the claims) is limited to these examples. Various changes and modifications can be made without departing from the scope defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular.

[0056] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A welding method for improving the performance of rail joints, characterized in that, The welding method involves moving flash welding of the rails. The moving flash welding process is carried out under vacuum conditions with a vacuum degree of less than 1 Pa. The moving flash welding sequentially includes a flash leveling stage, a preheating stage, a burning stage, an upsetting stage, and a stub pushing stage. The flash leveling voltage in the flash leveling stage is 360–450 V, and the flash leveling time is controlled between 10 and 40 s.

2. The welding method for improving the performance of rail joints according to claim 1, characterized in that, The preheating voltage during the preheating stage is 300–400V, and the preheating time is 40–110s.

3. The welding method for improving the performance of rail joints according to claim 1, characterized in that, The burning stage includes applying a voltage of 360-450V to the pearlitic steel rail to be welded for burning, with a burning time of 10-50 seconds.

4. The welding method for improving the performance of rail joints according to claim 1, characterized in that, The upsetting amount during the upsetting stage is 13-20 mm.

5. The welding method for improving the performance of rail joints according to claim 1, characterized in that, The welding slag produced during the upsetting stage is removed using a cutting tool, which is a profile cutter with the same outline as the rail.

6. The welding method for improving the performance of rail joints according to claim 1, characterized in that, The mobile flash welding also includes a heat treatment stage, in which the welded rail is naturally cooled to room temperature, and then the entire cross-section of the welded joint is induction heated by an induction coil.

7. The welding method for improving the performance of rail joints according to claim 6, characterized in that, The induction heating is stopped after reaching 900-980°C, and then air cooling is used.

8. The welding method for improving the performance of rail joints according to claim 7, characterized in that, The cooling device for air spraying is an air spray box with a width of 90-180mm. The air spray box blows air onto the upper surface and sides of the rail head. The air spray box is 15-60mm away from the rail surface and the air spray pressure is 0.05-0.5MPa. The air spraying stops after the temperature drops below 500℃ and then the rail head cools naturally.

9. A welding method for improving the performance of rail joints according to any one of claims 1-8, characterized in that, The rail is a pearlitic rail, and the mass fraction of each element in the pearlitic rail is as follows: C 0.55%–0.80%, Si 0.10%–0.90%, Mn 0.55%–1.20%, V ≤0.20%, S ≤0.008%, Al ≤0.004%, O ≤0.003%, with the balance being Fe and unavoidable impurities.

10. The welding method for improving the performance of rail joints according to claim 9, characterized in that, The pearlitic steel rail is a heat-treated pearlitic steel rail with a strength of 60 kg / m.

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