Axle box built-in type axle lightweight manufacturing method

Abstract

This invention discloses a lightweight manufacturing method for axles with built-in axle boxes, belonging to the field of rail transit axle technology. Based on the existing axle box-integrated alloy steel quenched and tempered axle design, this invention enlarges the central through-hole of the axle; then, the axle surface undergoes induction hardening treatment; followed by tempering treatment and grinding of the axle end faces and outer surfaces. This invention enables lightweight axle design and manufacturing, reducing the overall axle weight by 96.2 kg. The induction hardening treatment of the axle surface in this invention improves surface hardness and strength, enhancing resistance to external impacts and wear; the introduction of residual compressive stress on the axle surface can prevent or inhibit crack propagation; therefore, the method of this invention can achieve lightweighting while improving the axle's overall service life safety.

Description

Technical Field

[0001] This invention relates to the field of rail transit axle technology, specifically to a lightweight manufacturing method for axles with built-in axle boxes, which enables lightweight manufacturing of axles and improves axle safety. Background Technology

[0002] The axle is one of the most critical core components of railway vehicles, and its safety and reliability directly affect railway operational safety. To improve axle safety and reliability, the axle size can be increased to reduce nominal stress; however, this increases the axle weight, i.e., the unsprung mass of the train. Increased unsprung mass leads to more severe wheel-rail impacts, accelerates wheel-rail wear, and worsens operating conditions. Therefore, lightweight design and manufacturing of axles is a crucial research area in the field of rail transit component safety.

[0003] Researchers both domestically and internationally have invented numerous methods for lightweighting wheel axles, with hollow axles being the most commonly used. The diameter of the central through-hole in a hollow axle is typically 30 mm. However, for the sake of axle safety during service, traditional design and manufacturing methods have limited the potential to further improve axle lightweighting.

[0004] In the design of bogies with built-in axle boxes, the axle box is moved from the outside of the wheel seat to the inside, eliminating the axle journal portion and further reducing the axle's weight. With the axle box built in, the protruding axle section on the outside of the wheelset can be removed, and the axle end is directly aligned with the wheel, resulting in a more uniform overall axle size. The force distribution on axles with external and internal axle boxes is also significantly different: axles with external axle boxes experience bending moments from both vertical and lateral forces in the same direction, resulting in superimposed and larger bending moments; while axles with internal axle boxes experience bending moments from both vertical and lateral forces in opposite directions, resulting in canceling bending moments and reducing the overall bending moment on the axle. The built-in axle box design also facilitates a further increase in the diameter of the axle's central bore, enabling lightweight manufacturing in terms of both geometric design and service conditions.

[0005] Of course, built-in axle boxes also have certain limitations. First, the lateral span of the vehicle's anti-hunting shock absorbers is reduced, decreasing the vehicle's stability in lateral and hunting motions. Furthermore, due to the built-in axle boxes, the lateral spans of the air springs and primary suspension are also reduced, leading to a decrease in the torque supporting the vehicle's roll, thus reducing the vehicle's anti-roll capability. It is worth noting that if bearings need to be inspected, the wheelset must be removed, inspected, and then reinstalled, which exacerbates wear on the axle assembly surfaces and increases the risk of axle failure. To ensure the safe service of axles with built-in axle boxes and to achieve axle lightweighting, it is necessary to develop lightweight manufacturing methods for such axles. However, simply increasing the diameter of the central through-hole will reduce the axle's load-bearing capacity and increase the risk of axle fatigue failure.

[0006] Induction hardening can increase the surface hardness of axles, significantly improving their wear resistance. Furthermore, induction hardening can introduce residual compressive stress on the axle surface, inhibiting crack propagation. By designing an induction hardening process, the axle becomes hard on the outside and tough on the inside, significantly improving its strength. Therefore, induction hardening plays a crucial role in inhibiting wear, suppressing crack propagation, and increasing axle strength.

[0007] However, the design and manufacturing methods of induction hardening processes need to consider the axle geometry, service conditions, and damage modes of various parts to achieve a balance between hardness, strength, and toughness. If the surface hardness is very high, although the introduced residual compressive stress is large, the subsurface residual tensile stress is also very large, which is detrimental to suppressing crack propagation. Hardening increases the material's hardness but also makes it more brittle. If the hardening depth is too deep, the overall brittleness of the axle increases, and its resistance to crack propagation decreases. Therefore, the lightweight geometry and manufacturing methods of axles with integrated axle boxes require meticulous design and development.

[0008] Existing literature (Research on Induction Hardening Technology of Axles, Wang Shuqing et al.) studied the surface induction hardening of 40 steel axles, but the hardened layer depth obtained from their experiments was less than 10 mm. The rotational bending fatigue limit of a 7.5 mm diameter specimen treated with high-frequency induction hardening was 590 MPa, which is more than twice that of the base material (240 MPa), but it did not cover the lightweight design and manufacturing of full-size axles.

[0009] Chinese patent application (CN 112080625 A) uses a heat-treated DZ2 axle as a workpiece for induction hardening, resulting in a hardened layer depth of 4-10 mm, which is relatively shallow. The hardening machine rotates the axle at 0-60 r / min, which is slow and not conducive to the uniformity of the hardened layer distribution in the circumference. The tempering temperature of 150-250℃ is unreasonable. Too low a temperature makes it difficult to balance the internal stress of such a large component as the axle, while too high a temperature weakens the residual compressive stress introduced by induction hardening, which is not conducive to the overall fatigue strength of the axle. The service load of the axle depends on the axle weight, running speed and track conditions. The service load of railway axles on low-speed tracks with poor conditions is more severe than that of standard EMU axles. Simply determining the service conditions based on the train running speed is unscientific, and the conclusion that axles used in trains running at 200-350 km / h cannot meet the requirements of trains running at 350 km / h or higher lacks scientific basis. The material used in this invention is low-carbon alloy steel, and the surface hardness after induction hardening is no greater than 600 HV, while the claim of greater than 650 HV disclosed in the application lacks scientific basis. The fatigue strength of the induction-hardened axle exceeds 860 MPa, while the yield strength of the base material is 600 MPa and the fatigue strength is 428 MPa. Surface induction hardening only treats the surface portion of the material; if the overall load exceeds 600 MPa, the axle will have already yielded, making the results obtained from the invention completely unscientific. In this invention, the entire axle is surface induction hardened, with a diameter difference of approximately 60 mm between the axle journal and the wheel seat. However, the axle is located in the center of the coil, with a distance greater than 30 mm between the coil and the axle. This is completely inconsistent with the distance between the coil and the workpiece in induction hardening of large components, making heating impossible. The fatigue cycle number after induction hardening of the axle is 1×10⁻¹⁰. 8 The fatigue test standard for axles in Europe, Japan, and China is 1×10⁻⁶. 7 This test does not conform to the standard; furthermore, the standard fatigue test frequency for full-size axles is relatively low, with a test cycle of approximately two months for a single axle. If a single axle is tested 1×10 times... 8 The total testing time for a single axle is one and a half to two years, and testing multiple axles can take decades to complete, which is inconsistent with the development history of axles both domestically and internationally. In summary, many aspects of this patent lack scientific basis.

[0010] Chinese patent application (CN 112126750 A) uses a heat-treated DZ1 axle as a workpiece for induction hardening, resulting in a hardened layer depth of 4-10 mm, which is relatively shallow. The hardening machine tool drives the axle to rotate at 0-60 r / min, which is slow and not conducive to the circumferential uniformity of the axle. The tempering temperature of 150-250℃ is unreasonable. Too low a temperature makes it difficult to balance the internal stress of such a large component as the axle, while too high a temperature weakens the residual compressive stress introduced by induction hardening, which is not conducive to the overall fatigue strength of the axle. The service load of the axle depends on the axle weight, running speed and track conditions. The service load of railway axles on low-speed tracks with poor conditions is more severe than that of standard EMUs. Simply determining the service conditions based on the train's running speed is unscientific. It is too unscientific to conclude that axles used in trains with a service speed of 200-350 km / h cannot meet the requirements of trains with a service speed of 350 km / h or higher. The material used in this invention is low-carbon alloy steel, and the surface hardness after induction hardening is no greater than 550 HV. However, the data published in the application lacks scientific basis. The fatigue strength of the induction-hardened axle exceeds 707 MPa, while the yield strength of the base material is 580 MPa and the fatigue strength is 362 MPa. Surface induction hardening only treats the surface portion of the material; if the overall load exceeds 580 MPa, the axle will have already yielded. The results obtained from the invention are completely unscientific. In this invention, the entire axle is surface induction hardened, and the diameter difference between the axle journal and the wheel seat is approximately 60 mm. However, the axle is located in the center of the coil, and the distance between the coil and the axle is greater than 30 mm. This is completely inconsistent with the distance between the coil and the workpiece in induction hardening of large components, making heating impossible. The fatigue cycle number of the 0070 axle after induction hardening is 1×10⁻⁶. 8 The fatigue test standard for axles in Europe, Japan, and China is 1×10⁻⁶. 7 This test does not conform to the standard; furthermore, the standard fatigue test frequency for full-size axles is relatively low, with a test cycle of approximately two months for a single axle. If a single axle is tested 1×10 times... 8 The total testing time for a single axle is one and a half to two years, and testing multiple axles can take decades to complete, which is inconsistent with the development history of axles both domestically and internationally. In summary, many aspects of this patent lack scientific basis.

[0011] In summary, research on lightweight axle design and manufacturing is scarce, and existing publicly available information does not cover axle box-integrated axles and is therefore not of significant reference value. Thus, providing a method for the lightweight design and manufacturing of axle box-integrated axles is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0012] In view of this, the present invention provides a lightweight manufacturing method for an axle with an integrated axle box. This method uses a tempered EA4T axle as raw material, enlarging the diameter of the axle's central through-hole to reduce axle weight. To compensate for the risk of reduced load-bearing capacity due to increased central through-hole diameter, the present invention utilizes induction hardening to prepare a modified layer on the axle surface, improving the axle's load-bearing capacity. The modified layer depth can reach 20 mm, balancing wear resistance, impact resistance, and fatigue resistance. Using this method, the axle's central through-hole diameter is increased from the current 30 mm to 100 mm, and the axle weight is reduced by 96.2 kg, achieving a lightweight axle design, while simultaneously increasing the axle's fatigue strength by more than 18.3%.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A method for manufacturing lightweight axles with built-in axle boxes includes the following steps: The axle has a central through hole, the diameter of which is... ,in, The axle includes a bearing housing and a wheel seat, wherein the outer diameter of the bearing housing is larger than the outer diameter of the wheel seat; the process includes the following steps: (1) Enlarge the central through hole of the axle, the diameter of the central through hole of the axle is... So that its diameter is ,in, ; wherein, the ;and , ; (2) The axle surface is subjected to induction hardening treatment; (3) The axle is tempered; (4) Grinding the axle end face and outer surface.

[0015] In step (1), a certain amount of allowance is reserved at each shaft end.

[0016] Furthermore, the induction hardening machine tool mentioned in step (2) is a vertical induction hardening machine tool or a horizontal induction hardening machine tool.

[0017] Furthermore, the sensor is a scanning multi-segment arc sensor, which uses three arc segments to wrap around the axle, and uses a three-axis servo to wrap the axle for induction hardening; the distance between the arc of the scanning multi-segment arc sensor and the processing area is 4-6 mm.

[0018] In this invention, the scanning sensor is positioned according to a set trajectory via a three-axis servo system, ensuring that the arc on the scanning sensor matches the surface dimensions of the axle. The distance between the sensor arc and the axle is always maintained at 4-6 mm, ensuring sufficient heating energy and continuity of quenching depth in the axle transition area. When the center of the sensor reaches the other end face of the axle, the sensor pauses for 5-8 seconds, then the power is cut off and it continues to move at the set speed until the subsequent quenching ring or quenching plate completes the quenching of the entire axle, thus completing the induction quenching of the axle. The sensor starts before reaching the starting end face of the workpiece and pauses briefly upon reaching the other end face of the axle, making the hardened layer depth more uniform at both ends of the axle. This ensures the hardness and strength of the area prone to fretting fatigue on the outer edge of the axle wheel seat, improving the axle's resistance to fretting fatigue.

[0019] Furthermore, during the quenching process, the axle rotates at a speed of 60-90 r / min under the action of the ejector pin friction; the sensor input frequency is 1600-2400 Hz, and the input power is 240-360 kW.

[0020] Furthermore, quenching is performed by a water spray ring or water spray plate, with a pressure of not less than 0.3 MPa, a quenching medium concentration of 10%-15%, an axial width of not less than 100 mm for the water spray ring or water spray plate, and a quenched axle temperature of not more than 60℃.

[0021] In the present invention, the quenching medium is a water-based quenching fluid.

[0022] In the present invention, the depth of the induction hardening and tempering hardened layer of the axle is 12-20 mm; the hardened layer on the axle surface is continuous in the axial and circumferential directions, and the circumferential deviation of the hardened layer at any cross section does not exceed 1 mm.

[0023] Furthermore, the tempering temperature in step (3) is 180-220 ℃, and the tempering time is not less than 2 hours; Furthermore, after tempering, the axle is first allowed to cool naturally to below 100°C before being removed from the furnace, and then placed on a material platform to cool naturally to room temperature.

[0024] The axle grinding process employs multiple feeds with controlled feed rate, ensuring the total grinding depth does not exceed 0.3 mm. Grinding fluid is used for cooling during the grinding process to prevent the axle surface temperature from becoming too high or even overheating, thus reducing residual stress on the axle surface.

[0025] The solution of this invention is not only applicable to axle box-integrated axles made of EA4T material, but can also be used as a solution for lightweight manufacturing of axle box-integrated axles made of alloy steel materials such as DZ1, DZ2, 30NiCrMoV12, 34NiCrMoV6, and 35CrMo.

[0026] The beneficial effects of this invention are as follows: 1. Achieving lightweight design and manufacturing of axles: In this invention, the diameter of the central through hole of the axle is increased from 30 mm to 100 mm, and the overall weight of the axle is reduced by 96.2 kg.

[0027] 2. Improve the service safety of axles: The induction hardening treatment of the axle surface in this invention improves the surface hardness and strength, and enhances the resistance to impact and wear. The introduction of residual compressive stress on the axle surface can prevent or inhibit the propagation of cracks. Therefore, this manufacturing method can improve the service safety of axles throughout their entire life cycle.

[0028] This invention enables lightweight manufacturing of axles while improving the safety of axles throughout their entire life cycle, and can provide a method and process reference for other types of axles. Attached Figure Description

[0029] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 This is a flowchart illustrating the axle manufacturing process according to an embodiment of the present invention. Figure 2 This is a schematic diagram showing the final dimensions of the axle in an embodiment of the present invention; Figure 3 The metallographic distribution diagram of the shaft body in Embodiment 1 of the present invention is shown, where (a) is the microstructure gradient in the depth direction, (b) is the surface tempered martensite, and (c) is the core tempered sorbite. Figure 4 The metallographic distribution diagram of the shaft body in Embodiment 2 of the present invention is shown, where (a) is the microstructure gradient in the depth direction, (b) is the surface tempered martensite, and (c) is the core tempered sorbite. Figure 5 This is a diagram showing the surface hardness and residual stress distribution of the shaft in Embodiment 1 of the present invention. Figure 6 This is a diagram showing the surface hardness and residual stress distribution of the shaft in Embodiment 2 of the present invention. Figure 7 These are the local fatigue limit diagrams of the shaft body in Embodiments 1 and 2 of the present invention. Detailed Implementation

[0031] 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 only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1 (Case 1) Based on existing 25CrMo4 (EA4T) alloy steel quenched and tempered axles, the specific composition by weight percentage is shown in Table 1. The axles are produced through the following process: (1) When rough machining the axle, leave an extra 9 mm allowance at each end of the blank. Then, perform tempering, rough machining, drilling of the center through hole (100 mm), and semi-finish machining on the axle in sequence. After semi-finish machining, leave an allowance of 0.25 mm on one side of the axle surface in the radial direction. (2) After the axle is semi-finished, the axle surface is induction hardened using a vertical or horizontal induction hardening machine. The starting point of the inductor is 4 mm away from one end of the axle. When the center of the inductor reaches the end face of the axle, the inductor stays for 6 seconds and then scans the axle surface along the set trajectory for quenching. The inductor scanning speed is 110 mm / min. The inductor is a scanning multi-segment circular arc inductor, which uses three circular arcs to wrap around the axle and uses a three-axis servo to achieve induction hardening of the axle. The distance between the arc of the scanning multi-segment circular arc inductor and the processing area is maintained at 5 mm. During the quenching process, the axle rotates at a speed of 75 r / min under the action of the ejector pin friction. The inductor input frequency is 1600 Hz and the input power is 320 kW. The quenching is completed by a water spray ring or water spray plate with a pressure of not less than 0.3 MPa, a quenching medium concentration of 12%, an axial width of 100 mm for the water spray ring, and a temperature of not more than 60℃ after quenching.

[0033] (3) Place the quenched axle into a tempering furnace and temper it at 210°C for 2 hours. After tempering, let the axle cool naturally to below 100°C before taking it out of the furnace. Then place the axle on the material platform and let it cool naturally to room temperature. (4) After cooling, wire cutting is used to remove the excess material on the end face of the axle, leaving only 0.2 mm for subsequent fine grinding. Then, the end face of the axle is ground and the thread on the axle end is machined. Then, the outer surface of the axle is ground using a cylindrical grinder. The total grinding depth of the axle does not exceed 0.25 mm. Grinding fluid is used to cool the axle during the grinding process. After grinding, the axle is subjected to ultrasonic and magnetic particle testing. After passing the inspection, the axle is packaged and put into storage.

[0034] Table 1 Chemical composition of EA4T steel

[0035] Example 2 (Case 2) Produced through the following process: (1) When rough machining the axle, leave an extra 9 mm allowance at each end of the blank. Then, perform tempering, rough machining, drilling of the center through hole (100 mm), and semi-finish machining on the axle in sequence. After semi-finish machining, leave an allowance of 0.25 mm on one side of the axle surface in the radial direction. (2) After the axle is semi-finished, the axle surface is induction hardened using a vertical or horizontal induction hardening machine. The starting point of the inductor is 4 mm away from one end of the axle. When the center of the inductor reaches the end face of the axle, the inductor stays for 6 seconds and then scans the axle surface along the set trajectory for induction hardening. The inductor scanning speed is 130 mm / min. The inductor is a scanning multi-segment arc inductor, which uses three arc segments to wrap around the axle and uses a three-axis servo to achieve induction hardening of the axle. The distance between the arc of the scanning multi-segment arc inductor and the processing area is 5 mm. During the hardening process, the axle rotates at a speed of 75 r / min under the action of the ejector pin friction. The inductor input frequency is 1800 Hz and the input power is 280 kW. Quenching is performed by a water spray ring or water spray plate at a pressure of not less than 0.3 MPa, with a quenching medium concentration of 12%. The axial width of the water spray ring or water spray plate is not less than 100 mm, and the temperature of the axle after quenching is not greater than 60℃.

[0036] (3) Place the quenched axle into a tempering furnace and temper it at 210 ℃ for 2 h. After tempering, the axle should be naturally cooled to below 100 ℃ before being taken out of the furnace. Then place the axle on the material platform and let it cool naturally to room temperature. (4) After cooling, wire cutting is used to remove the excess material on the end face of the axle, leaving only 0.3 mm for subsequent fine grinding. Then, the end face of the axle is ground and the thread on the axle end is machined. Then, the outer surface of the axle is ground using a cylindrical grinder. The total grinding depth of the axle does not exceed 0.25 mm. Grinding fluid is used to cool the axle during the grinding process. After grinding, the axle is subjected to ultrasonic and magnetic particle testing. After passing the inspection, the axle is packaged and put into storage.

[0037] Comparative Examples 1-2: The same axle was quenched according to existing literature (Research on Induction Hardening Technology of Axle, Wang Shuqing et al.); Comparative Example 3: The same axle was subjected to quenching treatment according to Chinese patent application (CN 112080625 A); Comparative Example 4: The same axle was quenched according to Chinese patent application (CN 112126750 A).

[0038] Samples were taken from the axles of Examples 1 and 2, and after etching with a nitric acid-alcohol solution, the cross-sections of the modified layers of Examples 1 and 2 were obtained as shown below. Figure 3 and Figure 4 Hardness and residual stress tests can reveal the specific distribution of residual stress and Vickers hardness on the axle surface, as follows: Figure 5 and Figure 6 The hardening effects of this embodiment compared with those disclosed are summarized in Table 2.

[0039] Table 2 Comparison of quenching effects between the method of this invention and previously disclosed methods

[0040] This invention increases the diameter of the central through-hole in the axle, achieving a lightweight design. The increased diameter of the central through-hole leads to a smaller bearing cross-sectional area, particularly in the axle body, where the overall dimensions are smallest, resulting in the most significant reduction in load-bearing capacity and making it the weakest point of the axle with a higher risk of failure than other parts. Therefore, the following section will focus on analyzing the changes in the load-bearing capacity of the axle body due to lightweight design and manufacturing.

[0041] To reduce the risk of failure in lightweight axles, this invention analyzes the load-bearing capacity of Example 1 (hardened layer depth 19 mm) and Example 2 (hardened layer depth 16 mm) and compares it with existing inventions. Based on the local fatigue strength method, the local load stress curve and the local fatigue strength curve are interferometrically analyzed, such as... Figure 7 The fatigue limit of the embodiments of the present invention can be obtained. Since the disclosed comparative examples do not provide the radial distribution of residual stress, but the depth of their hardened layers does not exceed 10 mm, the secondary surface weak points caused by tensile stress balance are approximately 10 mm deep. To compare the beneficial effects of the present invention with existing methods, the existing comparative examples are optimally considered, i.e., their weak point depth is considered to be 2-3 times the depth of the hardened layer, and the fatigue limit is estimated using the local fatigue strength method. The fatigue limit results of each embodiment and comparative example are summarized in Table 3.

[0042] Table 3. Axle fatigue strength evaluation results obtained by the present invention and disclosed methods

[0043] As can be seen, the fatigue limit of the lightweight axle of the present invention is 441 MPa in Example 1, an improvement of 24.4%, and the fatigue limit of Example 2 is 427 MPa, an improvement of 18.3%. In comparison, the best fatigue limit result of the disclosed method in Comparative Example 1 is 273 MPa, an improvement of 13.8%, and the best fatigue limit result of the axle body section is 399 MPa, an improvement of 10.2%. Comprehensive analysis shows that the manufacturing method of the present invention can improve the fatigue limit of the lightweight axle by about 20%, which is superior to the currently disclosed methods, and the lightweighting does not affect the axle safety.

[0044] The change in the moment of inertia of the cross section caused by the change in the diameter of the central through hole will change the bending moment bearing capacity. In the case of lightweighting, the load-bearing capacity of the axle is further evaluated based on the improvement of fatigue strength. The load-bearing capacity of conventional axles and axles of the present invention under different diameter central through holes is calculated and summarized as shown in Table 4.

[0045] Table 4 Load Capacity of Hollow Car Bearings with Different Center Hole Diameters

[0046] It is evident that increasing the diameter of the axle's center through-hole reduces the axle's load-bearing capacity. However, this invention, through induction hardening to improve the axle's fatigue limit, effectively mitigates this effect and enhances the axle's load-bearing capacity. Verification by the aforementioned embodiments shows that, compared to the standard axle with an untreated 30 mm center through-hole diameter, Embodiment 1 can increase the center through-hole diameter to 80 mm, increasing the load-bearing capacity from 274.2 kN. m increased to 332.2 kN m, the load-bearing capacity of Example 2 can be 182.8 kN m increased to 206.6 kN Overall, the full-size axle can increase load-bearing capacity by 13.29% while reducing weight by 67.9 kg. If the center bore diameter is further increased to 100 mm, the axle weight will be reduced by 96.2 kg, and the axle body load-bearing capacity will decrease to 192.4 kN. m, while still ensuring a 5.25% increase in the overall load-bearing capacity of the full-size axle.

[0047] In summary, the embodiments of the present invention can increase the diameter of the central through hole of the full-size axle from 30 mm to 100 mm, reduce the weight by 96.2 kg, and ensure a 5.25% increase in load-bearing capacity. The surface hardness is increased from 230 HV in traditional manufacturing to over 400 HV, improving the wear resistance and fretting fatigue resistance of the axle; the fatigue strength of the axle is increased by about 20%.

[0048] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for manufacturing a lightweight axle with an integrated axle box, wherein the axle has a central through hole, the diameter of which is [missing information]. ,in, The axle includes a bearing housing and a wheel seat, wherein the outer diameter of the bearing housing is larger than the outer diameter of the wheel seat; characterized by comprising the following steps: (1) Enlarge the central through hole of the axle, the diameter of the central through hole of the axle is... This makes the diameter of its central through hole be ,in, ; wherein, the ; (2) The surface of the axle is subjected to induction hardening treatment; (3) The axle is tempered; (4) Grinding the axle end face and outer surface.

2. The lightweight manufacturing method of an axle box-integrated axle according to claim 1, characterized in that, In step (1), a certain allowance is reserved at each end of the axle during machining.

3. The lightweight manufacturing method of an axle box-integrated axle according to claim 1, characterized in that, In step (2), the induction hardening process uses an inductor starting point 3-5 mm away from one end of the axle. When the center of the inductor reaches or is about to reach the end face of the axle, the inductor stays for 5-8 seconds and then scans the axle surface trajectory for hardening. The inductor scanning speed is 100-150 mm / min.

4. The lightweight manufacturing method of an axle box-integrated axle according to claim 3, characterized in that, The sensor is a scanning multi-segment arc sensor, which uses three arc segments to wrap around the axle and uses a three-axis servo to achieve induction hardening of the axle; the distance between the arc of the scanning multi-segment arc sensor and the processing part is maintained at 4-6 mm.

5. The lightweight manufacturing method of an axle box-integrated axle according to claim 4, characterized in that, During the quenching process, the axle rotates at a speed of 60-90 r / min; the sensor input frequency is 1600-2400 Hz, and the input power is 240-360 kW.

6. The lightweight manufacturing method of an axle box-integrated axle according to claim 5, characterized in that, Quenching is performed by a water spray ring or water spray plate at a pressure of not less than 0.3 MPa. The quenching medium concentration is 10%-15%, the axial width of the water spray ring or water spray plate is not less than 100 mm, and the temperature of the axle after quenching is not greater than 60℃.

7. The lightweight manufacturing method of an axle box-integrated axle according to claim 1, characterized in that, The tempering temperature in step (3) is 180-220℃, and the tempering time is not less than 2 hours.

8. The lightweight manufacturing method of an axle box-integrated axle according to claim 7, characterized in that, After tempering, the axle is allowed to cool naturally to below 100°C before being removed from the furnace. Then, the axle is placed on the material platform and allowed to cool naturally to room temperature.

9. The lightweight manufacturing method of an axle box-integrated axle according to claim 1, characterized in that, In step (4), after grinding, a fine grinding allowance is retained and subsequent fine grinding is performed. The fine grinding allowance is 0.2-0.3 mm.

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