A method for flash butt welding of a turnout rail

Abstract

The application discloses a kind of switch rail flash welding construction methods, comprising the following operating steps: S1, construction preparation and switch investigation;S2, rail state inspection and pretreatment;S3, welding machine alignment and clamping;S4, dynamic compensation-based flash welding;S5, postweld normalizing treatment;S6, rough polishing;S7, welding head flaw detection;S8, fine polishing and profile finishing;S9, flatness and appearance inspection;S10, line locking.Effectively improve the consistency of welding quality, enhance the defect prevention capability, optimize the construction organization efficiency, reduce the operation threshold and realize the welding process traceability.

Description

Technical Field

[0001] This invention relates to the field of railway track engineering construction technology, and in particular to a flash welding construction method for turnout rails. Background Technology

[0002] Railway tracks are the core technology of modern high-speed railways, and turnouts, as a critical weak point in the track, have their welding quality directly affecting train safety and operation and maintenance costs. Currently, the welding of rails inside turnouts mainly uses mobile flash welding because it produces high-quality welded joints with stable performance, superior to gas pressure welding and aluminothermic welding.

[0003] However, turnouts have complex structures, including various types of non-standard rails (such as AT rails), such as main rails, switch rails, frog rails, and wing rails, and multiple variable cross-sections. In existing mobile flash welding construction, uniform welding parameters are often used for rail joints in different parts and with different cross-sections within the turnout. This "one-size-fits-all" approach has the following drawbacks: Poor parameter adaptability: AT rails and ordinary rails have large differences in cross-sectional area and thermal conductivity. Using the same parameters can easily lead to uneven heat distribution, resulting in defects such as incomplete penetration or overheating.

[0004] Dynamic adjustment lag: Factors such as network voltage fluctuations and equipment status changes during the welding process can affect welding power. Existing methods are mostly post-process inspections and cannot compensate in real time during the welding process, resulting in large dispersion in the quality of welded joints.

[0005] Reliance on manual experience: The control of melting amount and upsetting force relies heavily on the experience and judgment of operators, resulting in low level of intelligence and difficulty in ensuring the uniformity and high reliability of joints throughout the line.

[0006] Therefore, there is a need for an intelligent welding construction method that can dynamically adjust according to the rail type and real-time working conditions. Summary of the Invention

[0007] The purpose of this invention is to propose a flash welding construction method for turnout rails to improve the quality stability and consistency of turnout welded joints.

[0008] To achieve the objectives of this invention, the following technical solution is adopted: The present invention provides a flash welding construction method for turnout rails, comprising the following steps: S1. Construction preparation and turnout investigation; S2. Rail condition inspection and pretreatment; S3. Welding machine alignment and clamping; S4. Flash welding based on dynamic compensation; S5. Post-weld normalizing treatment; S6, coarse sanding; S7. Weld head flaw detection; S8, fine polishing and contour finishing; S9. Straightness and appearance inspection; S10, Line Lockout; Step S4 includes the following sub-steps: S4.1 Establishment of Welding Parameter Database: Conduct process tests on turnout rail joints with different combinations and establish a database containing standard welding process parameters; S4.2 Automatic identification of welding type and parameter preset: Identify the type of rails on both sides of the current welding head and retrieve the corresponding initial process parameters from the database; S4.3 Real-time monitoring of the welding process: During the welding process, key parameters including dynamic resistance, welding current, and upsetting displacement are collected in real time. S4.4 Dynamic Compensation Calculation and Control: The real-time acquired dynamic resistance curve is compared with the corresponding standard dynamic resistance-time characteristic curve in S4.1, and the burning rate and / or welding current are adjusted in real time according to the comparison results; and the upsetting amount is corrected in real time according to the final burning amount before the upsetting stage. S4.5 Real-time Welding Quality Assessment: After welding is completed, the system automatically compares the collected data with the standard process package and generates a quality assessment report.

[0009] Furthermore, the standard welding process parameters in step S4.1 include preheating current, preheating time, burning rate, burning amount, upsetting force, and upsetting amount.

[0010] Furthermore, the different combinations of turnout rail joints in step S4.1 include three types: ordinary rail-ordinary rail, ordinary rail-AT rail, and AT rail-AT rail.

[0011] Furthermore, the real-time monitoring sampling frequency in step S4.3 is no less than 1000Hz, and the key parameters collected include welding voltage, secondary circuit impedance, and upsetting force.

[0012] Furthermore, the dynamic compensation calculation and control in step S4.4 specifically involves: if the real-time dynamic resistance value deviates from the standard curve threshold by ±5%, the system determines that the welding process is abnormal, and adjusts the burning speed or welding current of the subsequent stages in real time according to the direction and magnitude of the deviation, so that the actual welding process approaches the standard process curve.

[0013] Furthermore, the dynamic compensation calculation and control in step S4.4 also includes: before entering the upsetting stage, the controller dynamically calculates and corrects the final upsetting amount and the energized upsetting time based on the final burning amount and the real-time monitored changes in the secondary circuit impedance.

[0014] Furthermore, the dynamic compensation calculation and control in step S4.4 also includes: when the rate of change of the secondary circuit impedance monitored in real time exceeds the set threshold, the system automatically adjusts the upsetting force to compensate for the energy loss caused by the change in the state of the conductive circuit.

[0015] Furthermore, step S1 includes planning the path for the dual-purpose rail welding machine to enter the turnout in the forward or reverse direction based on the turnout laying conditions of each station, and compiling a flow chart of the rail welding machine entering and exiting the turnout on the station layout plan.

[0016] Furthermore, step S2 includes rust removal and grinding of the end face of the rail to be welded and the contact area of ​​the electrode jaws, and checking that the perpendicularity of the rail end face is ≤0.5mm.

[0017] Furthermore, in step S5, the normalizing temperature is controlled as follows: 900±20℃ for the rail head and 800~850℃ for the rail base. The temperature is monitored in real time using an infrared thermometer, and the rail head is cooled naturally. The rough grinding requirements in step S6 are as follows: the grinding allowance of the rail bottom surface and non-working surface is controlled at 0~+0.5mm, the grinding width of the upper surface of the rail bottom corner is ≥45mm, the longitudinal weld is centered and the grinding width on both sides is ≥85mm, and the grinding surface shall not show blackening or bluening. Step S7 weld head inspection requirements: After the weld has cooled to below 40°C or to natural rail temperature, use an ultrasonic flaw detector to perform a full-length scan. In step S8, the fine grinding requirements are as follows: Before grinding, the temperature of the welded joint and the area within 1m at both ends should be below 50℃. Use a profile grinding machine to perform profile fine finishing on the rail top surface and the working edge of the rail head within a 400mm range on both sides of the weld to maintain the rail outline shape. The flatness inspection standard in step S9 is as follows: within 1m of the weld seam, the flatness of the rail top surface is 0~+0.2mm, the flatness of the inner working surface of the rail head is 0~+0.3mm, and the grinding depth of the base material is less than 0.5mm. In step S10, the track locking requirements are as follows: After the turnout joint welding is completed, the track temperature can only be locked when it is within the designed locking temperature range. First, install the fasteners in a two-on-one manner, and then tighten them fully after the remaining fasteners are completed. The torque of the fastener bolts should reach 120~150 N·m.

[0018] The present invention provides a flash welding construction method for turnout rails, which can effectively improve the consistency of welding quality, enhance the ability to prevent defects, optimize the efficiency of construction organization, reduce the operation threshold, and achieve traceability of the welding process. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is the overall flowchart of the flash welding construction method for turnout rails proposed in this invention; Figure 2 This is a block diagram of the flash welding control principle based on dynamic compensation in this invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0022] Please see Figure 1 This invention discloses a flash welding construction method for turnout rails, comprising the following steps: S1. Construction preparation and turnout investigation; S2. Rail condition inspection and pretreatment; S3. Welding machine alignment and clamping; S4. Flash welding based on dynamic compensation; S5. Post-weld normalizing treatment; S6, coarse sanding; S7. Weld head flaw detection; S8, fine polishing and contour finishing; S9. Straightness and appearance inspection; S10, Line Lockout; Step S4 includes the following sub-steps: S4.1 Establishment of Welding Parameter Database: Conduct process tests on turnout rail joints with different combinations and establish a database containing standard welding process parameters; S4.2 Automatic identification of welding type and parameter preset: Identify the type of rails on both sides of the current welding head and retrieve the corresponding initial process parameters from the database; S4.3 Real-time monitoring of the welding process: During the welding process, key parameters including dynamic resistance, welding current, and upsetting displacement are collected in real time. S4.4 Dynamic Compensation Calculation and Control: The real-time acquired dynamic resistance curve is compared with the corresponding standard dynamic resistance-time characteristic curve in S4.1, and the burning rate and / or welding current are adjusted in real time according to the comparison results; and the upsetting amount is corrected in real time according to the final burning amount before the upsetting stage. S4.5 Real-time Welding Quality Assessment: After welding is completed, the system automatically compares the collected data with the standard process package and generates a quality assessment report.

[0023] Furthermore, step S1, construction preparation and turnout investigation, specifically includes the following sub-steps: S1.1 The ballast leveling and rough adjustment of the turnout are completed. The geometric dimensions of the turnout meet the design and acceptance standards. The gauge, level, height, direction and other indicators of each part of the turnout have been tested and qualified.

[0024] S1.2 Investigate the type of turnout to be welded, the combination of rail types, the laying location, the on-site traffic conditions, and the surrounding environment. Turnout types should include at least common single turnouts such as No. 9, No. 12, No. 18, No. 30, and No. 42, as well as symmetrical turnouts and crossovers. Rail type combinations should include ordinary rail-ordinary rail, ordinary rail-AT rail, AT rail-AT rail, and ordinary rail-high manganese steel frogs.

[0025] S1.3. Based on the turnout installation situation at each station, conduct a construction survey in advance, plan the path for the rail welding machine for both road and rail turnouts, and prepare a flowchart of the rail welding machine's entry and exit from the turnouts on the station layout plan. The path planning needs to comprehensively consider: the specific location of the turnout in the station yard and the surrounding track conditions; the geometric conditions such as the width, slope, and curve radius of the rail welding machine's entry and exit passage; the existing line's train operation schedule and track maintenance window; and the layout of auxiliary facilities such as power supply and water supply.

[0026] S1.4. Determine the process parameters for mobile flash welding, complete the type test, and obtain the test report. The type test shall include at least the following items: tensile test, fatigue test, hardness test, metallographic structure inspection, fracture surface inspection, etc., and the test results shall meet the requirements of TB / T 1632 standard.

[0027] S1.5. Loading, unloading, and transporting the extended rail components of the turnout to the location of the rail components to be replaced. The extended rail components include guide rails A, B, C, D, E, and F, etc., and the specific specifications and quantities are determined according to the turnout model and welding sequence.

[0028] S1.6 Establishment of Welding Parameter Database: During the construction preparation phase, process tests are conducted on turnout rail joints with different combinations. These different combinations include at least three types: ordinary rail-ordinary rail, ordinary rail-AT rail, and AT rail-AT rail. The optimal welding parameters for each type of joint are obtained through process tests, and a database containing standard welding process parameters and standard dynamic resistance-time characteristic curves is established. The specific methods for process tests are as follows: Rails of the same material and specifications as those used on-site are selected for trial welding; orthogonal experimental design is used to optimize welding parameters, determining the optimal combination of parameters such as preheating current, preheating time, burning rate, burning amount, upsetting force, upsetting amount, and electric upsetting time; the dynamic resistance curve during the welding process is recorded, and characteristic values ​​(such as peak resistance, steady-state resistance, and resistance before upsetting) are extracted; mechanical property tests and microstructure analysis are conducted on the trial welded joints to verify the rationality of the parameters.

[0029] Furthermore, step S2, rail condition inspection and pretreatment, specifically includes the following sub-steps: S2.1 Remove rust and grind the end face of the rail to be welded and the contact area of ​​the electrode jaw and rail web to expose the metal luster. The grinding width shall not be less than the width of the electrode contact surface (usually 60~80mm), and the grinding depth shall not exceed 0.2mm. The base material of the rail shall not be damaged.

[0030] S2.2 Inspect and adjust the perpendicularity and torsion of the rail end face. The perpendicularity of the rail end face should be ≤0.5mm, and the rail end face should be free of cracks, oil stains, rust, and other impurities. The rail end face should be finished with a special end face grinder to ensure that the end face is flat and smooth.

[0031] S2.3 Place rollers under the rails to be welded, with a roller spacing of 3-5m to ensure that the moving end rail can freely expand and contract during welding, avoiding stress concentration. For critical parts such as the heel of the switch rail, the roller arrangement needs to be more dense.

[0032] S2.4. For the variable cross-section end of the AT rail, a special inspection is required to ensure that the variable cross-section area is free from damage, deformation, and cracks. The dimensional accuracy and surface quality of the variable cross-section area of ​​the AT rail directly affect the welding quality and require special attention.

[0033] S2.5 Rust removal quality inspection of rail end faces and conductive surfaces on the rail web: Visual inspection is required, ensuring uniform metallic luster and absence of residual rust and oil stains. If necessary, a surface roughness tester can be used for testing; the roughness Ra ≤ 12.5 μm.

[0034] Furthermore, step S3, welding machine alignment and clamping, specifically includes the following sub-steps: S3.1 The rail welding machine moves to the designated alignment point, aligning the center of the welding machine with the weld seam, with an allowable deviation of ≤20mm. The welding machine must move smoothly at a speed ≤5km / h.

[0035] S3.2 Raise the hydraulic outriggers to stabilize the welding machine and ensure it is level. The hydraulic outrigger system has an automatic leveling function, and pads should be placed under the outriggers to prevent settlement.

[0036] S3.3. Operate the clamps, using the rail head working surface as a reference, to precisely clamp the rail. The misalignment of the rail head working surface should be ≤0.2mm, and the misalignment of the rail bottom edge should be ≤1mm. The clamping force is determined according to the rail type and cross-sectional dimensions, and is generally controlled between 500 and 800kN.

[0037] S3.4 When welding critical parts such as the switch rail heel, secondary positioning is required to check the relative position of the switch rail and the stock rail, the squareness of the switch rail tip, and the position of the limit switch block. The specific inspection standards are: the deviation of the distance between the switch rail tip and the front of the turnout ≤ 5mm; the squareness of the switch rail tip ≤ 5mm; the gap difference between the two sides of the limit switch block ≤ 0.5mm.

[0038] S3.5 For the variable cross-section end of the AT rail, a special clamping pad must be used to ensure that the clamping force is evenly distributed and to avoid local stress concentration.

[0039] Further, step S4 includes the following sub-steps: S4.1 Establishment of Welding Parameter Database (details already described in S1, supplemented here): The database is organized in a hierarchical structure. The first layer is the turnout type (e.g., No. 9, No. 12, No. 18, etc.), the second layer is the rail combination type (ordinary rail-ordinary rail, ordinary rail-AT rail, AT rail-AT rail), and the third layer is the welding parameter group. Each record contains: Rail type identifier; Preheating current (A): range 800~1800A; Preheating time (s): range 20~60s; Burning rate (mm / s): range 0.8~2.0 mm / s; Burning depth (mm): Range 10~20mm; Upsetting force (kN): range 400~800kN; Upsetting amount (mm): range 8~15mm; Electric upsetting time (s): range 0.5~2.0s; Array of characteristic points for standard dynamic resistance-time curve.

[0040] S4.2 Automatic Welding Type Recognition and Parameter Preset: After the rail welding machine is aligned, the rail type can be identified using one of the following methods: Method 1: Manually input the rail type and joint combination using the operating terminal; Method 2: The laser scanner automatically identifies the profile of the rail section and matches it with the rail section template in the database; Method 3: RFID radio frequency identification, reading information from electronic tags embedded in the rails.

[0041] After identification is completed, the system automatically retrieves the corresponding initial process parameters from the database for preset.

[0042] S4.3 Real-time monitoring of the welding process: During the welding process, key parameters are collected and recorded in real time using a sensor system built into the rail welding machine at a sampling frequency of no less than 1000Hz. The sensor system includes: Dynamic resistance monitoring module: Calculates the dynamic resistance between rails in real time by measuring welding voltage and current, with a sampling frequency of 2000Hz; Hall effect current sensor: monitors welding current, range 0~2000A, accuracy ±1%; Voltage transformer: Monitors welding voltage, range 0~15V, accuracy ±0.5%; Displacement sensor: monitors the displacement of the top forging cylinder, with a range of 0~50mm and an accuracy of ±0.01mm, and is also used to calculate the burning amount; Pressure sensor: monitors upsetting force, range 0~1000kN, accuracy ±1%; Temperature sensor: Monitors rail temperature and is used for rail temperature compensation.

[0043] S4.4 Dynamic Compensation Calculation and Control: The dynamic compensation control adopts a dual closed-loop control strategy, with the outer loop being a dynamic resistance control loop and the inner loop being a current / speed control loop.

[0044] (1) Comparison of dynamic resistance curves: The welding controller compares the real-time acquired dynamic resistance curve with the corresponding standard dynamic resistance-time characteristic curve in S4.1. The dynamic resistance curve is typically divided into four stages: Stage I (Preheating Stage): Resistance gradually decreases; Phase II (initial flash): Resistance decreases slowly; Phase III (Flash Stabilization Period): The resistance tends to stabilize and fluctuates horizontally; Stage IV (before upsetting): Resistance drops rapidly.

[0045] Feature points (such as start point, inflection point, and end point) are extracted at each stage for deviation calculation.

[0046] (2) Deviation determination: If the real-time dynamic resistance value deviates from the standard curve threshold by ±5%, the system determines that the welding process is abnormal. The deviation calculation formula is as follows:

[0047] Where e(t) is the deviation, R real (t) is the real-time resistance, R std (t) represents the standard resistance.

[0048] (3) PID control algorithm: The controller uses a PID control algorithm to adjust the burning rate and / or welding current in real time for subsequent stages based on the direction and magnitude of the deviation. The formula for calculating the control quantity is as follows:

[0049] in, t represents the current welding time (in seconds). Δu(t) is the control quantity correction value at time t; : Proportional coefficient, ranging from 0.5 to 2.0, calibrated through process testing; Integral coefficient, ranging from 0.1 to 0.5; Differential coefficient, ranging from 0.05 to 0.2. τ is the integration variable, representing the continuous time points from 0 to the current time t; This is the integral term of the deviation, used to eliminate steady-state error; The differential term of the deviation reflects the trend of deviation change and is used for predictive control.

[0050] The control quantity correction value Δu(t) is used to correct the burning rate or welding current, and the correction relationship is as follows: Burning rate correction: V(t) = V0 + k v ×Δu(t), where V0 is the standard burn rate, k v k is the speed adjustment coefficient. v Take a value of 0.05 to 0.2 depending on the situation; Welding current correction: I(t) = I0 + k I ×Δu(t), where I0 is the standard welding current, k I k is the current adjustment coefficient. I Take 0.1 to 0.3 depending on the situation.

[0051] The PID control algorithm described above makes the dynamic resistance curve of the actual welding process approach the standard process curve, ensuring the consistency of welding quality.

[0052] (4) Correction before upsetting stage: Before entering the upsetting stage (usually at the end of the flashing stage, when the burn-off amount reaches 95% of the set value), the controller dynamically calculates and corrects the final upsetting amount and the energized upsetting time based on the final burn-off amount and the real-time monitored changes in the secondary circuit impedance.

[0053] ① Compensation for burn-off amount:

[0054] The corrected upsetting amount is:

[0055] Among them, L actual The actual amount of burning (unit: mm) is monitored in real time by a displacement sensor; L std The standard burn-off amount (unit: mm) is retrieved from the process parameter database, ranging from 10 to 20 mm. α is the burn-off compensation coefficient (dimensionless), ranging from 0.3 to 0.8, calibrated through process experiments; ΔL forge Upsetting compensation value (unit: mm); L forge The adjusted upsetting amount (unit: mm).

[0056] ② Secondary circuit impedance compensation:

[0057] The corrected electric upsetting time is:

[0058] in: Z actual The actual secondary circuit impedance (unit: mΩ) is calculated using the welding voltage to current ratio monitored in real time. Z std The standard secondary circuit impedance (unit: mΩ) is measured during type testing and stored in the database; t std The standard electric upsetting time (unit: s) ranges from 0.5 to 2.0 s; β is the impedance compensation coefficient (dimensionless), ranging from 0.2 to 0.6, calibrated through process testing; Δt forge The time compensation value for electric upsetting (unit: s); t forge The corrected electric upsetting time (unit: s).

[0059] (5) Rail temperature compensation: When the ambient temperature differs significantly from the standard process test temperature (20℃) (temperature difference ≥10℃), the system will automatically perform track temperature compensation.

[0060] Rail temperature compensation formula:

[0061] The revised preheating energy is:

[0062] in: E0 is the standard preheating energy (unit: J or A·s), determined by the product of the standard preheating current and the standard preheating time: E0 = I preheat0 ×t preheat0 ;I preheat.0 The standard preheating current (unit: A) is in the range of 800~1800A; t preheat0 The standard preheating time (unit: s) is within the range of 20~60s; T std The standard test temperature (unit: °C) is 20 °C. T amb The actual ambient temperature (unit: °C) is obtained by a temperature sensor. γ is the temperature compensation coefficient (unit: °C) -1 The value ranges from 0.01 to 0.03, and is calibrated through process testing. ΔE is the preheating energy compensation value (unit: J or A·s); E preheat The corrected preheating energy (unit: J or A·s).

[0063] The corrected preheating energy is achieved by adjusting the preheating current or preheating time: When prioritizing the adjustment of preheating current: I preheat =I preheat0 +ΔE / t preheat0 ; When prioritizing the adjustment of preheating time: t preheat =t preheat0 +ΔE / I preheat0 ; Among them, I preheat For the corrected preheating current, t preheat This is the corrected preheating time; after adjustment, the preheating current must be within the range of 800~1800A, and the preheating time must be within the range of 20~60s.

[0064] Furthermore, step S5, post-weld normalizing treatment, specifically includes the following sub-steps: S5.1 After the welding head cools to below 500℃, use a medium-frequency normalizing device to heat the weld and heat-affected zone. The medium-frequency normalizing device has a frequency of 800~2000Hz and a power of 100~200kW.

[0065] S5.2 Normalizing Temperature Control: The surface temperature of the rail head is controlled at 900±20℃, and the surface temperature of the rail foot is controlled at 800~850℃, monitored in real time using an infrared thermometer. Temperature measuring points are arranged at the center of the weld, 10mm away from the center of the weld, and 20mm away from the center of the weld.

[0066] S5.3 The heating time is determined according to the type of rail and the size of the joint, and is generally 120~180s.

[0067] S5.4 The rail head should be cooled naturally. Rapid cooling with water is strictly prohibited to prevent the formation of hardened structures such as martensite.

[0068] S5.5 Pre-normalizing inspection: Inspect the condition of the medium-frequency normalizing equipment, check for damage or leaks in the connecting wires and cooling water pipes, and check for foreign objects inside the induction coil. The cooling water temperature should be below 25℃, and the water pressure should be ≥0.2MPa.

[0069] S5.6 Cleaning before normalizing: Clean the normalizing joint before installation, remove conductive materials such as iron slag, and remove flammable materials near the joint.

[0070] S5.7 Normalizing Coil Installation: The normalizing coil must not come into contact with the rails to prevent arcing, which could damage the coil and the normalizing transformer. The induction coil must be installed vertically, and both coil fixing bolts must be tightened securely without any looseness. The transformer must be held steady during loading and unloading to prevent it from tipping over and damaging the equipment.

[0071] S5.8 Safe Operation: Installation and disassembly must be carried out under power failure. First, place the normalizing equipment at least 600mm away from the weld seam to prevent burns caused by excessive welding head temperature.

[0072] Furthermore, step S6, rough polishing, specifically includes the following sub-steps: S6.1 Measure the sprue allowance before rough grinding. The sprue allowance refers to the amount of metal remaining after the weld seam is pushed up, which is generally 0~3mm. Determine the grinding range and grinding amount based on the sprue allowance.

[0073] S6.2 Grinding range: Non-working surface of the rail, rail jaw, and upper surface of the rail bottom corner in the joint area. The grinding width is 150~200mm on both sides of the weld.

[0074] S6.3 Grinding Standards: The grinding allowance for the rail bottom surface and non-working surface shall be controlled within 0~+0.5mm; the grinding width of the upper surface of the rail bottom corner inward shall be ≥45mm, and the longitudinal weld seam shall be centered and the grinding width towards both sides shall be ≥85mm.

[0075] S6.4 Grinding Requirements: Apply an appropriate amount of material during grinding, ensuring the surface is not damaged and that blackening or bluing does not occur. Blackening or bluing is caused by overheating during grinding, leading to surface oxidation or phase transformation, which will reduce the surface performance of the rail.

[0076] S6.5 After rough grinding, the ground surface must be smooth and even to meet the requirements for flaw detection. Surface roughness Ra≤25μm.

[0077] Furthermore, step S7, weld head flaw inspection, specifically includes the following sub-steps: S7.1 Timing of Flaw Detection: The weld temperature should be cooled to below 40℃ or to the natural rail temperature. If the cooling time is insufficient, the propagation speed of ultrasonic waves in the high-temperature rail will change, affecting the accuracy of flaw detection.

[0078] S7.2 Flaw Detection Equipment: Use a digital ultrasonic flaw detector with a probe frequency of 2.5~5MHz and a crystal size of 8×12mm or 10×16mm.

[0079] S7.3. Scanning range: Within 200mm on both sides of the weld, a comprehensive scan is conducted using a combination of direct and oblique scanning methods.

[0080] S7.4, Flaw Detection Standard: The flaw detection results shall meet the requirements of TB / T 1632.1 "Rail Welding Part 1: General Technical Conditions". The acceptance standard is: No defects larger than φ2mm equivalent; No linear defects such as cracks or incomplete penetration; Single defect area ≤10mm 2 .

[0081] S7.5, Flaw Detection Record: After flaw detection is completed, fill in the "Ultrasonic Flaw Detection Record of Welded Joints of Steel Rails on Construction Site" in a timely manner. The record includes: joint number, flaw detection date, flaw detection personnel, instrument model, probe specifications, scanning method, defect location and equivalent, evaluation conclusion, etc.

[0082] Furthermore, step S8, fine polishing and contouring, specifically includes the following sub-steps: S8.1 Preparation before grinding: The temperature of the weld joint and within 1m of both ends should be below 50℃. Measure the straightness of the weld in the horizontal and vertical directions within 500mm on both sides to determine the appropriate grinding feed rate.

[0083] S8.2, Contour Grinding Range: Contour grinding is performed on the working edges of the rail top surface and rail head side within a 400mm range on both sides of the weld to maintain the rail outline shape.

[0084] S8.3 Grinding equipment: Use a profile grinding machine with automatic feeding and contour tracking functions, and a grinding accuracy of ≤0.1mm.

[0085] S8.4, Polishing requirements: The fillets on the rail head and rail bottom should be smooth within a 1m range, without any obvious protrusions or depressions; The rail weld head should be ground smooth within 150mm on both sides of the weld seam on the upper surface of the rail base and within 35mm from the edge of the rail base corner on both sides. There must be no obvious indentations, dents, or scratches within 100mm on both sides of the weld. To prevent the rail surface from overheating and turning black or blue during grinding, the feed rate and coolant supply should be controlled.

[0086] S8.5 Inspection after grinding: Use a profile measuring instrument to check the rail head profile and compare it with the standard rail profile. The deviation should be ≤0.3mm.

[0087] Further, step S9, flatness and appearance inspection, specifically includes the following sub-steps: S9.1 Straightness Inspection: Within a 1m radius centered on the weld, measure using a 1m straightedge and feeler gauge. Measurement locations include: Longitudinal measurement of the top surface of the rail: 3 locations (center, 300mm from the center, and 500mm from the center); Longitudinal measurement of the inner working edge of the rail head: 3 positions; Lateral view of the top surface of the rail: Measure the cross-section at the weld.

[0088] S9.2, Straightness Standard: Rail top surface flatness: 0~+0.2mm; Straightness of the inner working surface of the rail head: 0~+0.3mm; Rail bottom straightness: 0~+0.5mm.

[0089] S9.3 Visual Inspection: The welded joint and the surface of the rail in its vicinity shall be free from cracks, obvious indentations, scratches, dents, electrode burns, and grinding burns. The inspection method is visual inspection and inspection with a magnifying glass (5-10x magnifying glass).

[0090] S9.4 Grinding Depth Inspection: The grinding depth of the base material should be less than 0.5mm, and a depth gauge should be used for measurement.

[0091] Furthermore, step S10, line locking, specifically includes the following sub-steps: S10.1 Locking Timing: Track locking can only be carried out after the turnout joint welding is completed and the rail temperature is within the designed locking rail temperature range. The designed locking rail temperature is generally ±5℃ of the local annual average temperature.

[0092] S10.2 Initial Locking: Install fasteners on the track in a two-on-one pattern (i.e., install one fastener every two sleepers) to lock the track and ensure the safe movement of the rail welding machine. After initial locking, a preliminary constraint is created between the sleepers and the rails.

[0093] S10.3, Full Locking: Replace any remaining fasteners, fully tighten all fastener bolts, and ensure the lower jaw of the spring clip is against the gauge plate. Fastener bolt torque should reach 120~150 N·m, and should be checked using a torque wrench at a frequency of no less than 20%.

[0094] S10.4 Post-locking inspection: After locking, check the geometric dimensions such as track gauge, level, and direction to ensure they meet the design and acceptance standards.

[0095] Furthermore, the present invention also proposes a welding system for implementing the welding construction method of the present invention, comprising a rail welding machine main unit, a sensor system, a controller, and a human-machine interface: (1) Rail welding machine main unit: The dual-purpose road and rail chassis has both road and rail travel modes; The 180° rotating head allows for quick switching of welding directions; The hydraulic outrigger support system has an automatic leveling function and an outrigger stroke of ≥500mm; Welding transformer, rated capacity ≥250kVA; The clamping system is hydraulically driven, and the clamping force is adjustable from 500 to 800 kN.

[0096] (2) Sensor system: Dynamic resistance monitoring module: consists of a Hall current sensor and a voltage transformer, with a sampling frequency of 2000Hz; Displacement sensor: installed inside the top forging cylinder, measuring range 0~50mm, accuracy ±0.01mm; Pressure sensor: installed in the hydraulic circuit of the top forging cylinder, measuring range 0~1000kN, accuracy ±1%; Temperature sensor: Infrared thermometer, temperature range 0~1500℃, accuracy ±1%; Laser scanner: used for rail contour recognition, scanning speed ≥1000 points / second.

[0097] (3) Controller: Industrial-grade embedded controller, main frequency ≥1GHz; Built-in PID control algorithm and database management system; It has multiple communication interfaces such as Ethernet, CAN bus, and RS485; With an IP65 protection rating, it is suitable for outdoor construction environments.

[0098] (4) Human-computer interaction interface: Industrial touchscreens of 10 inches and above; The graphical user interface displays welding parameters, dynamic resistance curves, and evaluation results in real time. Supports data export and printing functions.

[0099] Compared with the prior art, the present invention has the following technical effects: 1. Improve the consistency of welding quality This invention establishes a standard process database for different types of joints and introduces an intelligent control method based on comparing real-time parameters such as dynamic resistance with standard characteristic curves during the welding process, thereby dynamically compensating welding parameters. This effectively overcomes the instability of welding quality caused by factors such as differences in rail type, power grid fluctuations, and changes in equipment status, making the quality of each weld joint approach the optimal process level.

[0100] Through experimental comparison, the performance indicators of the welded joints using the method of this invention are as follows: Tensile strength: ≥980MPa (base material standard ≥900MPa), 100% pass rate; Fatigue strength: 2×10 6 No breakage in subsequent cycles, with a pass rate of ≥99.5%; Hardness distribution: Hardness deviation in weld zone ≤10HB, softening width in heat-affected zone ≤15mm; Dynamic resistance curve similarity: ≥0.95, connector quality dispersion is reduced by about 60%.

[0101] 2. Enhance defect prevention capabilities By real-time monitoring and dynamic adjustment, quality control is shifted from post-production inspection to process control, significantly reducing the probability of internal defects such as incomplete penetration, overheating, and inclusions. Practical applications show that: The incidence of incomplete penetration defects was reduced from 2.5% in the traditional process to 0.3%; The incidence of overheating defects decreased from 1.8% to 0.2%; The first-pass yield rate of post-weld flaw detection increased from 92% to 98.5%.

[0102] 3. Optimize construction organization efficiency By combining forward / reverse entry path planning for the turnout with the 180° rotation function of the rail welding machine head, the optimal welding sequence can be flexibly selected according to site conditions. Taking a No. 12 single turnout as an example: Traditional process: requires 6 shifts and auxiliary work time of about 4 hours; This invention allows for reverse entry: requiring only two positioning attempts, with auxiliary operation time of approximately 1.5 hours; Construction efficiency is improved by about 40%, and skylight time is saved by about 2.5 hours.

[0103] 4. Lower the operational threshold By automatically identifying rail types, retrieving parameters, performing dynamic compensation, and assessing quality, the system significantly reduces reliance on manual experience in the welding process. The training cycle for construction personnel has been shortened from three months to two weeks, and the difference in welding quality between different operators has decreased from 30% to less than 5%.

[0104] 5. Achieve traceability of the welding process Each welding process involves recording key parameters, dynamic resistance curves, and evaluation conclusions to create a complete quality archive. When joint damage occurs during line operation, welding process parameters can be traced, causes analyzed, and a basis for process improvement provided.

[0105] The technical principles of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that these descriptions are merely for explaining the principles of the present invention and should not be construed as limiting the scope of protection of the present invention in any way. Based on this explanation, those skilled in the art can conceive of other specific embodiments or equivalent substitutions of the present invention without creative effort, and all such embodiments will fall within the scope of protection of the present invention.

Claims

1. A method for flash welding of turnout rails, characterized in that, The following steps are included: S1. Construction preparation and turnout investigation; S2. Rail condition inspection and pretreatment; S3. Welding machine alignment and clamping; S4. Flash welding based on dynamic compensation; S5. Post-weld normalizing treatment; S6, coarse sanding; S7. Weld head flaw detection; S8, fine polishing and contour finishing; S9. Straightness and appearance inspection; S10, Line Lockout; Step S4 includes the following sub-steps: S4.1 Establishment of Welding Parameter Database: Conduct process tests on turnout rail joints with different combinations and establish a database containing standard welding process parameters; S4.2 Automatic identification of welding type and parameter preset: Identify the type of rails on both sides of the current welding head and retrieve the corresponding initial process parameters from the database; S4.3 Real-time monitoring of the welding process: During the welding process, key parameters including dynamic resistance, welding current, and upsetting displacement are collected in real time. S4.4 Dynamic Compensation Calculation and Control: The real-time acquired dynamic resistance curve is compared with the corresponding standard dynamic resistance-time characteristic curve in S4.1, and the burning rate and / or welding current are adjusted in real time according to the comparison results; and the upsetting amount is corrected in real time according to the final burning amount before the upsetting stage. S4.5 Real-time Welding Quality Assessment: After welding is completed, the system automatically compares the collected data with the standard process package and generates a quality assessment report.

2. The method for flash welding of turnout rails according to claim 1, characterized in that, The standard welding process parameters in step S4.1 include preheating current, preheating time, burning rate, burning amount, upsetting force, and upsetting amount.

3. The method for flash welding of turnout rails according to claim 1, characterized in that, The different combinations of turnout rail joints in step S4.1 include three types: ordinary rail-ordinary rail, ordinary rail-AT rail, and AT rail-AT rail.

4. The flash welding construction method for turnout rails according to claim 1, characterized in that, The real-time monitoring sampling frequency in step S4.3 is no less than 1000Hz, and the key parameters collected include welding voltage, secondary circuit impedance, and upsetting force.

5. The method for flash welding of turnout rails according to claim 1, characterized in that, The dynamic compensation calculation and control in step S4.4 specifically involves: if the real-time dynamic resistance value deviates from the standard curve threshold by ±5%, the system determines that the welding process is abnormal, and adjusts the burning speed or welding current of the subsequent stages in real time according to the direction and magnitude of the deviation, so that the actual welding process approaches the standard process curve.

6. The method for flash welding of turnout rails according to claim 1, characterized in that, The dynamic compensation calculation and control in step S4.4 also includes: before entering the upsetting stage, the controller dynamically calculates and corrects the final upsetting amount and the energized upsetting time based on the final burning amount and the real-time monitored changes in the secondary circuit impedance.

7. The method for flash welding of turnout rails according to claim 1, characterized in that, The dynamic compensation calculation and control in step S4.4 also includes: when the real-time monitored rate of change of secondary circuit impedance exceeds the set threshold, the system automatically adjusts the upsetting force to compensate for the energy loss caused by the change in the state of the conductive circuit.

8. The method for flash welding of turnout rails according to claim 1, characterized in that, Step S1 includes planning the path for the rail welding machine to enter the turnout in the forward or reverse direction based on the turnout laying conditions of each station, and compiling a flow chart of the rail welding machine entering and exiting the turnout on the station plan.

9. The method for flash welding of turnout rails according to claim 1, characterized in that, Step S2 includes rust removal and grinding of the end face of the rail to be welded and the contact area of ​​the electrode jaws, and checking that the verticality of the rail end face is ≤0.5mm.

10. A method for flash welding of turnout rails according to any one of claims 1 to 9, characterized in that, In step S5, the normalizing temperature is controlled as follows: 900±20℃ for the rail head and 800~850℃ for the rail base. The temperature is monitored in real time using an infrared thermometer, and the rail head is cooled naturally. The rough grinding requirements in step S6 are as follows: the grinding allowance of the rail bottom surface and non-working surface is controlled at 0~+0.5mm, the grinding width of the upper surface of the rail bottom corner is ≥45mm, the longitudinal weld is centered and the grinding width on both sides is ≥85mm, and the grinding surface shall not show blackening or bluening. The weld head inspection requirements in step S7 are as follows: After the weld has cooled to below 40°C or to the natural rail temperature, use an ultrasonic flaw detector to perform a full-length scan. The fine grinding requirements in step S8 are as follows: the temperature of the welded joint and within 1m of both ends should be below 50℃ before grinding. Use a profile grinding machine to perform profile fine finishing on the rail top surface and the working edge of the rail head side within a 400mm range on both sides of the weld to maintain the rail outline shape. The flatness inspection standard in step S9 is as follows: within a 1m range centered on the weld, the flatness of the rail top surface is 0~+0.2mm, the flatness of the inner working surface of the rail head is 0~+0.3mm, and the grinding depth of the base material is less than 0.5mm. The track locking requirements in step S10 are as follows: after the turnout joint welding is completed, the track temperature can be locked only when it is within the designed locking temperature range. First, install the fasteners in a two-on-one manner, and after completing the remaining fasteners, tighten them all. The torque of the fastener bolts should reach 120~150 N·m.

Images