Heavy-duty axle rolling method based on rolling difference

Abstract

The invention discloses a heavy axle rolling method based on rolling differentiation, which comprises the following steps: S1, axle pretreatment: adopting a two-stage cleaning process, firstly performing high-pressure flushing through kerosene at 60-80 DEG C, then performing double-frequency alternate ultrasonic cleaning, and drying with hot air at 70 DEG C after cleaning, so that the surface roughness Ra of the pretreated axle is less than or equal to 1.6 mu m, and the oil stain residual quantity is less than or equal to 5mg / m < 2 >; s2, three-dimensional modeling and stress partitioning are carried out, an axle digital model is established, and stress simulation is carried out. According to the method, a plastic deformation layer of 0.2 mm-0. 3mm and a residual compressive stress field of which the depth is greater than or equal to 0.5 mm are formed on the surface layer aiming at reinforced rolling of a high-stress area, and the range value is-200MPa to-300MPa, so that the tensile stress in the working process is effectively counteracted, the fatigue life of the axle is prolonged, and the service life of the axle is prolonged. According to the stepped rolling technology, surface defects are eliminated through pre-rolling, a uniform strengthened layer is formed through main rolling, the surface quality is optimized through fine rolling, the overall impact resistance of the axle is improved, and the axle can adapt to the severe working condition of long-term heavy-load running of heavy vehicles.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of axle roll forming, and particularly relates to a heavy axle roll forming method based on roll forming differentiation. BACKGROUND

[0002] As a core component for transmitting torque and bearing load of heavy vehicles (such as railway freight cars, engineering machinery, heavy trucks, etc.), the working environment of the heavy axle has the significant characteristics of high load, variable stress and strong impact, and the axle is long-term under complex mechanical action, which is prone to stress concentration at the structural transition parts (such as unloading grooves and shaft shoulder fillets), and thus fatigue cracks are easily caused, which seriously threatens the safety of vehicle operation.

[0003] As a key means for improving the surface quality and fatigue strength of the axle, the roll forming technology can effectively improve the surface roughness and form a residual compressive stress layer by applying a certain pressure to the surface of the axle, so as to improve the mechanical properties of the axle. However, due to the geometric structure mutation, the stress concentration coefficient of the unloading grooves and shaft shoulder fillets of the axle can reach 2.5-3.0, which is a high-risk area of fatigue failure. The existing process adopts a vertical roll forming mode, which cannot form a uniform residual compressive stress field at these transition parts, but may aggravate stress concentration due to uneven stress, resulting in limited improvement of the fatigue life of the axle after roll forming. SUMMARY

[0004] In view of the problems in the prior art, the application provides the following technical scheme:

[0005] The heavy axle roll forming method based on roll forming differentiation comprises the following steps:

[0006] S1, axle pretreatment, adopting a two-stage cleaning process, first high-pressure washing with 60-80 DEG C kerosene, then double-frequency alternating ultrasonic cleaning, and drying with 70 DEG C hot air after cleaning, so that the surface roughness Ra of the pretreated axle is less than or equal to 1.6 microns, and the oil stain residual amount is less than or equal to 5 mg / m 2 ;

[0007] S2, three-dimensional modeling and stress partitioning, establishing a digital model of the axle and performing stress simulation, and dividing high stress area, medium stress area and low stress area according to the simulation results;

[0008] S3, roll forming system configuration, adopting a multi-axis linkage system transformed from a numerical control lathe, equipped with an automatic tool changing mechanism, a WC-Co hard alloy material roll forming head and an auxiliary strengthening device containing two independent hydraulic circuits;

[0009] S4, differential parameter matrix construction, based on material properties and stress partitioning, establishing a dynamic parameter matrix containing roll forming pressure, feed amount, speed, roll forming times and angle parameters;

[0010] S5, the stepped rolling process, pre-rolling, main rolling, and fine rolling are sequentially carried out, the pre-rolling is fast rolled once at 50% set pressure, the main rolling is rolled multiple times according to the parameter matrix and stops for 2 seconds after each rolling, and the fine rolling reduces the feeding amount to 0.05-0.1 mm / r and is rolled once at 80% set pressure;

[0011] S6, special part strengthening, a customized arc-shaped roller is used for the unloading groove to apply 11±1 tons of symmetrical pressure through a double-channel hydraulic system and keep pressure for 6 seconds, and a rotatable arc-shaped rolling head is used for the shaft shoulder fillet for 3 times of reciprocating rolling;

[0012] S7, intelligent monitoring and feedback, integrating infrared temperature measuring instrument, force sensor, and laser displacement sensor for real-time monitoring, and automatically adjusting when exceeding the set value.

[0013] As a preferred embodiment of the above technical solution, in S1, the pressure of high-pressure washing is 0.3-0.5 MPa, 0.5-1% surfactant is added to the aqueous solution for ultrasonic cleaning, the frequency of double-frequency alternating cleaning is 28 kHz and 40 kHz, the cleaning time is 15 minutes, and the air speed of hot air drying is 15 m / s.

[0014] As a preferred embodiment of the above technical solution, in S2, a three-dimensional scanning is used to establish a digital model of the axle, the model is imported into ANSYS Workbench to apply a rated load for stress simulation, the high-stress area is the unloading groove and the shaft shoulder fillet, the medium-stress area is the bearing fitting section, and the low-stress area is the free section.

[0015] As a preferred embodiment of the above technical solution, in S3, the positioning accuracy of the X / Z axis of the multi-axis linkage system is ±0.005 mm, the tool changing time of the automatic tool changing mechanism is less than 3 seconds, the working surface of the rolling head is mirror ground with Ra≤0.02 μm, and the proportional valve control pressure output response time of the auxiliary strengthening device is less than 50 ms.

[0016] As a preferred embodiment of the above technical solution, in S4, for the EA4T material, the rolling pressure of the high-stress area is 300±20 bar, the feeding amount is 0.1±0.02 mm / r, the rotating speed is 320±20 r / min, and the rolling times are 3-4 times, the rolling pressure of the low-stress area is 220±20 bar, the feeding amount is 0.18±0.02 mm / r, the rotating speed is 275±20 r / min, and the rolling times are 2 times.

[0017] For the LZ50 material, the high stress area has a rolling pressure of 250±10 bar, a feed amount of 0.1±0.01 mm / r, a rotating speed of 260±10 r / min, and 4-5 rolling times; the low stress area has a rolling pressure of 200±20 bar, a feed amount of 0.17±0.02 mm / r, a rotating speed of 225±15 r / min, and 2-3 rolling times; and in terms of the angle parameter, the high stress transition section adopts a 60° angle, and the low stress flat section adopts a 90° vertical rolling.

[0018] As a preferred embodiment of the above technical solution, in S5, the surface roughness of the axle can be reduced to Ra≤0.8 μm.

[0019] As a preferred embodiment of the above technical solution, in S6, the customized arc-shaped roller used for the unloading groove strengthening has a fitting degree with the groove of ≥98%, a plastic deformation layer of 0.2 mm-0.3 mm is generated on the surface layer after strengthening, a residual compressive stress field with a depth of ≥0.5 mm is formed, and the residual compressive stress is in the range of -200 MPa to -300 MPa.

[0020] The curvature radius of the rotatable arc-shaped rolling head used for the shoulder fillet strengthening is R3 mm-R5 mm, and the feeding direction of each of the three reciprocating rollings is opposite.

[0021] As a preferred embodiment of the above technical solution, in S7, the sampling frequency of the infrared temperature measuring instrument is 10 Hz, and when the temperature exceeds 80℃, the 5% emulsion spray cooling is automatically started;

[0022] The accuracy of the force sensor is ±1% FS, and when the rolling force fluctuation exceeds the set value ±5%, the output of the servo motor is automatically adjusted;

[0023] The resolution of the laser displacement sensor is 0.5 μm, which is used for detecting the diameter change to ensure that the design requirement of 0.3 mm-0.7 mm is met.

[0024] The present application has the following beneficial effects:

[0025] 1. The present application strengthens the high stress area through rolling, so that a plastic deformation layer of 0.2 mm-0.3 mm and a residual compressive stress field with a depth of ≥0.5 mm are formed on the surface layer, the residual compressive stress is in the range of -200 MPa to -300 MPa, the tensile stress in the working process is effectively offset, the fatigue life of the axle is improved, the step rolling process eliminates surface defects through pre-rolling, forms a uniform strengthening layer through main rolling, optimizes the surface quality through fine rolling, improves the overall impact resistance of the axle, and can adapt to the harsh working conditions of long-term heavy load operation of heavy vehicles.

[0026] 2. The two-stage cleaning process of the present application combines double-frequency ultrasonic cleaning, so that the surface roughness of the axle is controlled to be Ra≤1.6 μm, and the oil stain residual amount is ≤5 mg / m 2This provides a clean and uniform reference surface for subsequent rolling, reducing rolling defects caused by surface impurities. The combination of multi-axis linkage system and intelligent monitoring feedback enables real-time control of rolling parameters, allowing the axle size tolerance of mass production to be controlled within ±0.02mm, improving the surface roughness pass rate, and solving the problem of large quality fluctuations in traditional processes.

[0027] 3. The differentiated parameter matrix of this invention is compatible with a variety of commonly used axle materials such as EA4T and LZ50. By accurately matching the material properties and stress zones, it avoids the problem of over-rolling or under-rolling caused by "one-size-fits-all" parameters, thereby reducing material waste and rework rate.

[0028] 4. The high-stress transition section of this invention uses a 60° included angle rolling head, which makes the rolling pressure evenly distributed along the axial and radial directions, reducing the stress concentration factor by 25%-40%; the reciprocating rolling of the shoulder fillet eliminates unidirectional stress segregation, significantly reduces the risk of fatigue crack initiation, and improves the safety of heavy vehicle operation. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0030] Example

[0031] The heavy-duty axle rolling method based on rolling differentiation includes the following steps:

[0032] Axle pretreatment: A two-stage cleaning process is adopted. First, the axle is high-pressure rinsed with kerosene at 60℃-80℃. Setting the temperature within this range enhances the dissolving power of the kerosene, better removing surface oxide scale and cutting residue. The high-pressure rinsing pressure is 0.3MPa-0.5MPa, which effectively cleans without damaging the axle surface. Next, dual-frequency alternating ultrasonic cleaning is performed. 0.5%-1% surfactant is added to the aqueous solution to improve the cleaning effect. The 28kHz frequency targets large particles of dirt, while the 40kHz frequency targets small impurities. The alternating frequency ensures thorough cleaning. The cleaning time of 15 minutes ensures complete cleaning. After cleaning, the axle is dried with 70℃ hot air at a wind speed of 15m / s, resulting in a surface roughness Ra ≤ 1.6μm and oil residue ≤ 5mg / m² after pretreatment. 2 This meets the surface quality requirements of subsequent processing.

[0033] 3D Modeling and Stress Zoning: A digital model of the axle is established and stress simulation is performed to accurately reproduce the structural characteristics of the axle. The model is imported into ANSYS Workbench, and a rated load is applied for stress simulation, simulating the stress state of the axle in actual operation. Based on the simulation results, the axle is divided into high-stress zones (unloading grooves, axle shoulder fillets), medium-stress zones (bearing mating sections), and low-stress zones (free sections). Different stress zones bear different loads and stresses during use, requiring different rolling parameters.

[0034] Roller burnishing system configuration: Utilizing a multi-axis linkage system modified from a CNC lathe, the X / Z axis positioning accuracy reaches ±0.005mm, ensuring the roller burnishing head can precisely act on the corresponding parts of the axle. It is equipped with an automatic tool changer, a WC-Co carbide roller burnishing head, and an auxiliary strengthening device with two independent hydraulic circuits. The tool change time is <3 seconds, improving processing efficiency and adapting to the tool requirements of different parts of the roller burnishing process. The WC-Co carbide roller burnishing head has high hardness and good wear resistance, and its working surface is mirror-polished (Ra≤0.02μm), ensuring the quality of the axle surface after roller burnishing. The auxiliary strengthening device with two independent hydraulic circuits has a proportional valve control pressure output response time of <50ms, enabling rapid and precise control of the roller burnishing pressure to meet the requirements of strengthening roller burnishing in special parts.

[0035] Construction of differentiated parameter matrix: Based on material properties and stress zoning, a dynamic parameter matrix is ​​established that includes rolling pressure, feed rate, rotation speed, number of rolling passes and angle parameters.

[0036] It should be noted that for EA4T material, the high-stress area bears greater stress and requires higher rolling pressure (300±20 bar), lower feed rate (0.1±0.02 mm / r), higher rotation speed (320±20 r / min), and more rolling cycles (3-4 times) to form a sufficient reinforcement layer; while the low-stress area uses relatively lower rolling parameters.

[0037] For LZ50 material, its properties are different from EA4T, so the rolling parameters are also different. The rolling pressure (250±10 bar) and rotation speed (260±10 r / min) in the high stress area are different from those of EA4T. The number of rolling cycles (4-5 times) is also more to adapt to its material characteristics.

[0038] In terms of angular parameters, the high-stress transition section adopts a 60° included angle to ensure that the rolling pressure is evenly distributed along the axial and radial directions, reducing stress concentration; the low-stress straight section adopts a 90° vertical rolling to ensure surface flatness.

[0039] Stepped rolling process: The process is carried out in three stages: pre-rolling, main rolling and fine rolling. The pre-rolling is performed once with a 50% set pressure. The main rolling is performed multiple times according to the parameter matrix, with a 2-second pause after each rolling. The fine rolling is performed once with a reduced feed rate of 0.05-0.1 mm / r and a 80% set pressure.

[0040] Specifically, the purpose of pre-rolling is to eliminate surface micro-irregularities and provide a uniform reference for subsequent processing. The main rolling allows the material to undergo sufficient plastic deformation to form a certain reinforcing layer. The fine rolling further reduces the surface roughness, reducing the surface roughness of the axle to Ra≤0.8μm and improving the surface quality.

[0041] Special parts reinforcement: The unloading groove is reinforced with a custom arc-shaped roller through a dual-channel hydraulic system to apply symmetrical pressure of 11±1 tons and hold the pressure for 6 seconds. The shoulder fillet is rolled three times with a rotatable arc-shaped rolling head.

[0042] Specifically, a custom-designed arc-shaped roller with a conformity ≥98% to the groove shape is used for the unloading groove. A symmetrical pressure of 11±1 tons is applied through a dual-channel hydraulic system and held for 6 seconds, creating a 0.2mm-0.3mm plastic deformation layer on the surface and forming a residual compressive stress field (-200MPa to -300MPa) with a depth ≥0.5mm, enhancing the strength and fatigue resistance of the unloading groove. For the shoulder fillet, a rotatable arc-shaped rolling head (radius of curvature R3mm-R5mm) is used for three reciprocating rolling passes, with each pass in the opposite direction of feed. This eliminates stress segregation caused by unidirectional rolling, resulting in a more uniform stress distribution and improved performance of the shoulder fillet.

[0043] Intelligent monitoring and feedback: It integrates an infrared thermometer, force sensor, and laser displacement sensor for real-time monitoring and automatically adjusts when the set value is exceeded.

[0044] It should be noted that the infrared thermometer used is the PT300A model manufactured by Dikai, with a sampling frequency of 10Hz. It monitors the surface temperature in real time and automatically starts 5% emulsion spray cooling when the temperature exceeds 80℃ to avoid the temperature from affecting the performance of the axle material.

[0045] The force sensor uses a C6B force sensor manufactured by HBM in Germany, with an accuracy of ±1%FS. When the rolling pressure fluctuation exceeds the set value of ±5%, the servo motor output is automatically adjusted to ensure that the rolling pressure is stable within the set range and to guarantee the rolling effect.

[0046] The laser displacement sensor selected is the optoNCDT1420 series from the German company Miiyi, with a resolution of 0.5μm, used to detect diameter changes, ensuring compliance with the design requirements of 0.3mm-0.7mm and guaranteeing the dimensional accuracy of the axle.

[0047] A multi-parameter monitoring system consisting of an infrared thermometer, force sensor, and laser displacement sensor can record processing data in real time. Combined with the CNC system, it enables quality traceability and provides data support for subsequent process optimization, which is in line with the development trend of modern intelligent manufacturing.

[0048] Comparative Example 1

[0049] Using the same EA4T axle material and specifications as in the example, and processed according to traditional methods:

[0050] Pretreatment: Rinsedating with room temperature kerosene only, without ultrasonic cleaning; surface roughness Ra = 3.5 μm; oil residue 12.8 mg / m². 2 .

[0051] Rolling parameters: The entire shaft adopts uniform parameters (pressure 250 bar, feed rate 0.15 mm / r, speed 280 r / min, rolling times 2 times, 90° vertical rolling).

[0052] Special treatment for special parts: The unloading groove is not reinforced separately, but is only processed during the main rolling process.

[0053] Monitoring method: No real-time monitoring, only random sampling after processing.

[0054] Performance comparison results

[0055]

[0056] Comparative Example 2

[0057] Using LZ50 axles of the same material and specifications as in the example, and employing a simplified processing method:

[0058] Pretreatment: Same as in the example (two-stage cleaning process), surface roughness Ra = 1.4 μm, oil residue 3.0 mg / m³. 2 .

[0059] Rolling parameters: Although different pressures are set for high and low stress zones (250 bar for high stress zone and 200 bar for low stress zone), the feed rate, rotation speed and number of rolling cycles are not distinguished, and stepped rolling is not used; only a single main rolling cycle is performed.

[0060] Special treatment for special parts: The unloading groove is processed using only a conventional rolling head, without the use of customized arc rollers and pressure holding process.

[0061] Monitoring method: Only temperature monitoring is provided; there is no real-time feedback on pressure and size.

[0062] Performance comparison results

[0063]

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. A heavy-duty vehicle axle rolling method based on rolling differentiation, characterized in that, Includes the following steps: S1. Axle pretreatment employs a two-stage cleaning process: first, high-pressure rinsing with kerosene at 60℃-80℃, followed by alternating dual-frequency ultrasonic cleaning. After cleaning, the axle is dried with 70℃ hot air, ensuring a surface roughness Ra ≤ 1.6μm and oil residue ≤ 5mg / m² after pretreatment. 2 ; S2. Three-dimensional modeling and stress zoning: Establish a digital model of the axle and perform stress simulation. Divide the high-stress zone, medium-stress zone and low-stress zone according to the simulation results. S3, Roller system configuration, adopts a multi-axis linkage system modified from CNC lathe, equipped with an automatic tool changer, WC-Co carbide roller head and auxiliary strengthening device with two independent hydraulic circuits; S4. Construction of differentiated parameter matrix: Based on material properties and stress zoning, a dynamic parameter matrix is ​​established that includes rolling pressure, feed rate, rotation speed, number of rolling cycles and angle parameters. S5, stepped rolling process, which involves three stages of processing: pre-rolling, main rolling and fine rolling. Pre-rolling is performed once with 50% set pressure. Main rolling is performed multiple times according to the parameter matrix, with a 2-second pause after each rolling. Fine rolling is performed once with the feed rate reduced to 0.05-0.1 mm / r and 80% set pressure. S6. Special parts are reinforced. Custom arc-shaped rollers are used to apply symmetrical pressure of 11±1 tons through a dual-channel hydraulic system to the unloading groove and hold the pressure for 6 seconds. Rotatable arc-shaped rolling head is used to perform 3 reciprocating rolling on the shoulder fillet. S7 features intelligent monitoring and feedback, integrating an infrared thermometer, force sensor, and laser displacement sensor for real-time monitoring, and automatically adjusting when the set value is exceeded.

2. The heavy-duty axle rolling method based on rolling differentiation according to claim 1, characterized in that, In S1, the pressure of high-pressure rinsing is 0.3MPa-0.5MPa, 0.5%-1% surfactant is added to the aqueous solution for ultrasonic cleaning, the frequency of dual-frequency alternating cleaning is 28kHz and 40kHz, the cleaning time is 15 minutes, and the wind speed for hot air drying is 15m / s.

3. The heavy-duty axle rolling method based on rolling differentiation according to claim 1, characterized in that, In S2, a digital model of the axle is established by 3D scanning, imported into ANSYS Workbench, and subjected to rated load for stress simulation. The high stress area is the unloading groove and axle shoulder fillet, the medium stress area is the bearing mating section, and the low stress area is the free section.

4. The heavy-duty axle rolling method based on rolling differentiation according to claim 1, characterized in that, In S3, the X / Z axis positioning accuracy of the multi-axis linkage system reaches ±0.005mm, the tool changing time of the automatic tool changer is <3 seconds, the working surface of the roller burnishing head is mirror-polished with Ra≤0.02μm, and the proportional valve control pressure output response time of the auxiliary strengthening device is <50ms.

5. The heavy-duty axle rolling method based on rolling differentiation according to claim 1, characterized in that, In S4, for EA4T material, the rolling pressure in the high-stress zone is 300±20 bar, the feed rate is 0.1±0.02 mm / r, the rotation speed is 320±20 r / min, and the number of rolling cycles is 3-4. The rolling pressure in the low-stress zone is 220±20 bar, the feed rate is 0.18±0.02 mm / r, the rotation speed is 275±20 r / min, and the number of rolling cycles is 2. For LZ50 material, the rolling pressure in the high-stress zone is 250±10 bar, the feed rate is 0.1±0.01 mm / r, the rotation speed is 260±10 r / min, and the number of rolling cycles is 4-5. The rolling pressure in the low-stress zone is 200±20 bar, the feed rate is 0.17±0.02 mm / r, the rotation speed is 225±15 r / min, and the number of rolling cycles is 2-3. In terms of angle parameters, a 60° included angle is used in the high-stress transition section, and a 90° vertical rolling angle is used in the low-stress straight section.

6. The heavy-duty axle rolling method based on rolling differentiation according to claim 1, characterized in that, In S5, the surface roughness of the axle can be reduced to Ra≤0.8μm.

7. The heavy-duty axle rolling method based on rolling differentiation according to claim 1, characterized in that, In S6, the custom arc-shaped rollers used for unloading groove reinforcement have a matching degree of ≥98% with the groove shape. After reinforcement, a plastic deformation layer of 0.2mm-0.3mm is generated on the surface, forming a residual compressive stress field with a depth of ≥0.5mm, ranging from -200MPa to -300MPa. The radius of curvature of the rotatable arc-shaped rolling head used for shoulder fillet reinforcement is R3mm-R5mm, and the feed direction is opposite for each of the three reciprocating rolling cycles.

8. The heavy-duty axle rolling method based on rolling differentiation according to claim 1, characterized in that, In the S7, the infrared thermometer has a sampling frequency of 10Hz and automatically starts 5% emulsion spray cooling when the temperature exceeds 80℃. The force sensor has an accuracy of ±1%FS, and automatically adjusts the servo motor output when the rolling force fluctuation exceeds the set value of ±5%. The laser displacement sensor has a resolution of 0.5 μm and is used to detect diameter changes to ensure compliance with the design requirements of 0.3 mm to 0.7 mm.

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