Lightweight shock absorber piston rod and manufacturing method thereof

Abstract

The invention discloses a piston rod technology, and aims to provide a lightweight shock absorber piston rod and a manufacturing method thereof, and the technical scheme is that the lightweight shock absorber piston rod comprises a piston rod body, the piston rod body comprises a loading end made of a cold heading material 10B21 and used for being connected with a shock absorber mounting structure and providing initial assembly strength; the piston end is made of a cold heading material 10B21 and used for being matched with a piston assembly in the shock absorber and transmitting loads; the working area is made of a precise seamless steel pipe 35 #, is connected between the loading end and the piston end and is used for bearing a reciprocating load when the shock absorber works; the loading end, the working area and the piston end are integrally welded and formed through a friction welding process; the outer surface of the working area is subjected to chromium plating treatment and is subjected to dehydrogenation treatment within 24 hours after chromium plating; the invention is applicable to the technical field of piston rods.

Description

Technical Field

[0001] This invention relates to piston rod technology, and more specifically, to a lightweight vibration damper piston rod and a method for manufacturing the same. Background Technology

[0002] As the automotive industry moves towards lightweighting and high performance, large SUVs such as the new generation Acura MDX, while pursuing greater interior space and comfort, place higher technical demands on the piston rod, a key component of the chassis suspension system's shock absorbers. Traditional shock absorber piston rods often use a single material, which, while meeting basic mechanical performance requirements, results in issues such as high weight and energy consumption under the trend of vehicle lightweighting. In addition, their structural design often fails to optimize for the differentiated load requirements of the mounting end, working area, and piston end, easily leading to localized stress concentration or material redundancy, affecting the lifespan of the shock absorber and ride comfort.

[0003] In existing technical solutions, piston rods are usually made by integral forging or machining of a single material, which makes it difficult to balance the contradiction between "lightweight" and "high load-bearing capacity". For example, although all-steel materials have high strength, they are heavy, which is not conducive to optimizing the fuel consumption of the whole vehicle; while some aluminum piston rods cannot meet the impact load requirements under complex road conditions due to insufficient material strength. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a lightweight shock absorber piston rod and its manufacturing method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a lightweight shock absorber piston rod, comprising a piston rod body, wherein the piston rod body includes:

[0006] The loading end is made of cold-forged material 10B21 and is used to connect with the shock absorber mounting structure and provide initial assembly strength;

[0007] The piston end, made of cold-forged material 10B21, is used to cooperate with the internal piston assembly of the shock absorber and transmit load;

[0008] The working area, made of precision seamless steel pipe #35, is connected between the loading end and the piston end and is used to bear the reciprocating load when the shock absorber is working.

[0009] The loading end, working area, and piston end are integrally welded together using a friction welding process; the outer surface of the working area is chrome-plated and then dehydrogenated within 24 hours after chrome plating.

[0010] The present invention is further configured such that: the overall dimensional accuracy of the piston rod body meets the following requirements: surface straightness ≤ 0.01 / 100, roundness ≤ 0.01; surface roughness meets the following requirement: Ra < 0.063.

[0011] A method for manufacturing a lightweight vibration damper piston rod, characterized by comprising the following steps:

[0012] S1. Raw material pretreatment: Pre-process the loading end, piston end and working area respectively to ensure that the initial dimensions of each component meet the design requirements;

[0013] S2. Heat treatment at both ends: Before subsequent machining of the loading end and piston end, heat treatment is performed to improve material strength and subsequent welding adaptability.

[0014] S3. Friction welding: The pre-treated loading end and piston end are continuously welded to the working area using a single-pass friction welding process to form an integrated structure. Friction parameters are controlled during the welding process to avoid multiple layers and multiple weld marks.

[0015] S4. Initial inspection of weld strength: After the weld is welded, a preliminary visual inspection is carried out. After confirming that there are no defects visible to the naked eye, the weld will proceed to chrome plating.

[0016] S5. Chrome plating: Chrome plating is applied to the surface of the working area to improve corrosion resistance;

[0017] S6. Dehydrogenation treatment: Dehydrogenation treatment is carried out within 24 hours after chrome plating, and the treated piston rod is kept at 260℃ for 1 hour to eliminate the risk of hydrogen embrittlement.

[0018] S7. Dimensional and performance fine inspection: The surface roughness, straightness, roundness, chrome plating thickness and weld appearance of the piston rod are inspected in sequence to ensure that they meet the design requirements;

[0019] S8. Comprehensive performance test: The finished piston rod is subjected to fatigue strength test, static strength test, impact resistance test and salt spray test in sequence. The product is judged to be qualified after all tests are passed.

[0020] The present invention is further configured such that, in step S3, during the friction welding process, the temperature change curve and pressure feedback value of the welding area are monitored in real time, specifically including:

[0021] When the friction temperature T1 in the initial stage of welding exceeds the first preset threshold Ta, welding should be stopped immediately and the wear condition of the friction pair should be checked.

[0022] When T1 ≤ Ta but T1 > Tb, where Ta > Tb, record the current temperature and continuously monitor the rate of temperature change ΔT / Δt over the next 30 seconds:

[0023] If ΔT / Δt ≤ preset stability threshold K1 and pressure P ∈ [P1, P2], then maintain the current welding parameters and continue welding;

[0024] If ΔT / Δt>K1 or Then adjust the friction speed and axial pressure, and re-monitor the temperature and pressure stability within 30 seconds. If the conditions are still not met after adjustment, stop welding and replace the friction welding head.

[0025] After welding is completed, ultrasonic testing is used to check for pores or cracks inside the weld. If the test is qualified, proceed to step S4; if the test is unqualified, mark the weld position and proceed to step S3 to re-perform friction welding until the test results meet the requirements.

[0026] The present invention is further configured such that: in S4, the initial inspection of weld strength also includes a petal test: the welded joint is placed in a special bending fixture, and the weld is bent at 60° with the fixed fulcrum as the center. During the bending process, the load displacement curve is monitored by a force sensor. When the ratio of the maximum bending load Fmax to the theoretically calculated value F0, Fmax / F0, is ≥0.9 and there are no visible cracks at the weld after bending, the weld strength is deemed to be qualified; if Fmax / F0 <0.9 or cracks appear, the welding strength is deemed insufficient, and the friction welding parameters need to be readjusted and S3 is repeated.

[0027] The present invention is further configured such that, in step S7, the straightness and roundness detection includes:

[0028] S71. Check the surface straightness L1 and roundness C1. If L1≤0.01 / 100 and C1≤0.01, it is considered qualified.

[0029] S72. If L1 > 0.01 / 100 or C1 > 0.01, then obtain the three-dimensional morphology curve of the entire piston rod length using a laser scanner, and analyze the distribution pattern of local out-of-tolerance areas:

[0030] S73. When the length of the out-of-tolerance area is less than 10% of the total length, it should be re-inspected after local grinding correction.

[0031] S74. When the length of the out-of-tolerance area is greater than or equal to 10% of the total length, or when the morphology curve shows continuous fluctuations exceeding the preset threshold R, it is determined that the overall processing deviation is too large. Then, proceed to S3 to re-weld or adjust the pre-processing dimensions.

[0032] The present invention is further configured such that, in step S8, the comprehensive performance test includes: a fatigue strength test employing 2.5 million cycles of loading, with strain gauges used to monitor the stress change curve of the piston rod in real time.

[0033] If the deviation Δσ from the peak stress σ1 and the initial stress σ0 is ≤5% when the number of cycles reaches 1 million, the test shall continue.

[0034] If Δσ > 5%, the test should be suspended and the piston rod should be checked for microcracks or stress concentration points. After repair, the test should be restarted from 0.

[0035] After completing 2.5 million cycles, if no cracks are confirmed by magnetic particle testing or penetrant testing, and the deformation is ≤60% or no fracture occurs after applying the ultimate load in the static strength test, and there is no fracture in the impact resistance test (i.e., a 100kg iron hammer impacts the loading end from a height of 0.8m without fracture) and no corrosion in the 72h salt spray test, then it is judged as a final qualified product.

[0036] If any item fails to meet the requirements, the product is deemed non-conforming.

[0037] The present invention is further configured such that the comprehensive control of straightness and roundness includes: during inspection, if straightness L1 and roundness C1 simultaneously satisfy L1≤0.01 / 100 and C1≤0.01, the geometric accuracy is directly determined to be qualified; if only L1 or C1 is out of tolerance, the out-of-tolerance item is corrected through compensation processing and then re-inspected; if both L1 and C1 are out of tolerance and the out-of-tolerance amount exceeds the cumulative threshold, it is determined to be an overall forming defect, and it is necessary to return to S1 to reselect raw materials or adjust the pre-processing process until the piston rod manufactured subsequently meets the coordinated accuracy requirements of straightness and roundness.

[0038] The beneficial effects of this invention are:

[0039] 1. Compared to existing technologies, the lightweight shock absorber piston rod of this invention achieves an optimized balance between performance and cost by selecting appropriate materials for each segment. The mounting end and piston end use cold-forged material 10B21, whose excellent cold-forging formability and initial strength ensure a reliable connection with the shock absorber mounting structure and stable load transmission to the piston assembly, preventing assembly loosening or load transmission failure. The working area uses precision seamless steel pipe 35#, which combines good mechanical properties with lightweight characteristics, effectively bearing the reciprocating load during shock absorber operation, reducing overall weight and lowering energy consumption. Friction welding process achieves three-section integrated molding, resulting in higher weld strength and better consistency compared to traditional welding methods, avoiding weak links caused by multi-segment connections. Chrome plating of the working area improves corrosion resistance and extends service life, and hydrogen removal treatment within 24 hours effectively eliminates the risk of hydrogen embrittlement, preventing fracture accidents caused by hydrogen embrittlement during operation, significantly improving the safety and durability of the piston rod.

[0040] 2. In the lightweight vibration damper piston rod of this invention, the overall dimensional accuracy and surface roughness requirements of the piston rod body are clearly defined, providing a key guarantee for the stable operation of the vibration damper. The high-precision standards of surface straightness ≤0.01 / 100 and roundness ≤0.01 ensure the coaxiality of the piston rod's reciprocating motion during vibration damper operation, avoiding motion jamming or increased local wear caused by geometric deviations, reducing abnormal wear of internal components of the vibration damper, and extending the overall service life of the vibration damper. At the same time, the high-precision geometric dimensions ensure uniform clearance between the piston assembly and the inner wall of the cylinder, avoiding hydraulic shock caused by uneven clearance, improving the vibration damping effect and operational stability of the vibration damper. The surface roughness Ra<0.063 reduces the friction coefficient between the piston rod and the seal during piston rod movement, reduces friction loss, improves sealing performance, prevents hydraulic oil leakage, ensures the efficiency of the vibration damper's hydraulic system, and reduces heat generated by friction, avoiding the impact of local overheating on material properties, further improving the reliability of the piston rod and the working stability of the vibration damper.

[0041] 3. In this invention, through a step-by-step, refined process design, the quality and performance of the lightweight shock absorber piston rod are comprehensively guaranteed; S1 raw material pretreatment ensures that the initial dimensions of each component meet the design requirements, laying a good foundation for subsequent welding and processing, and avoiding final product defects due to initial dimensional deviations; S2 heat treatment at both ends improves the material strength and welding adaptability of the loading end and piston end in advance, reduces the risk of cracking during welding, and enhances the weld bonding strength; S3 friction welding single-pass continuous welding forms an integrated structure, avoiding performance hazards caused by multi-layer and multi-pass weld marks, and improving the overall structural stability; S4 initial inspection of weld strength and S7 precise inspection of dimensional performance form a dual quality control, timely screening out products that do not meet appearance and dimensional standards, and avoiding waste in subsequent processes; S5 chrome plating treatment and S6 hydrogen removal treatment respectively improve corrosion resistance and eliminate the risk of hydrogen embrittlement; S8 comprehensive performance testing fully verifies the fatigue strength, static strength, impact resistance, and corrosion resistance of the piston rod, ensuring that the finished product can cope with complex working conditions, significantly reducing the probability of shock absorber failure during use, and improving the product qualification rate.

[0042] 4. The present invention has a simple and reasonable structure, is easy to manufacture and operate, avoids the defects of the prior art, and is suitable for promotion and application. Attached Figure Description

[0043] Figure 1 This is a structural diagram of the piston rod of the lightweight vibration damper of the present invention.

[0044] Figure 2 This is a flowchart illustrating the manufacturing method of the lightweight vibration damper piston rod of the present invention.

[0045] Figure 1-2 Reference numerals: 1. Loading end; 2. Piston end; 3. Working area. Detailed Implementation

[0046] Reference Figure 1-2 The embodiments of the lightweight vibration damper piston rod and its manufacturing method of the present invention are further described below.

[0047] For ease of explanation, spatial relative terms such as “up,” “down,” “left,” and “right” are used in the embodiments to describe the relationship of one element or feature shown in the figures relative to another element or feature. It should be understood that, in addition to the orientations shown in the figures, spatial terms are intended to include different orientations of the device in use or operation. For example, if the device in the figures is inverted, an element described as being “down” of other elements or features would be positioned “up” of those other elements or features. Therefore, the exemplary term “down” can encompass both up and down orientations. The device may be positioned in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0048] Moreover, relational terms such as “first” and “second” are used merely to distinguish one component from another that has the same name, without necessarily requiring or implying any such actual relationship or order between the components.

[0049] Figures 1 to 2 The illustrated lightweight shock absorber piston rod includes a piston rod body, the piston rod body comprising:

[0050] The loading end 1, made of cold-forged material 10B21, is used to connect with the shock absorber mounting structure and provide initial assembly strength;

[0051] Piston end 2, made of cold-forged material 10B21, is used to cooperate with the internal piston assembly of the shock absorber and transmit load;

[0052] Working area 3, made of precision seamless steel pipe 35#, is connected between loading end 1 and piston end 2 to bear the reciprocating load when the shock absorber is working; the hollow structure design not only reduces the weight of the piston rod, but also improves its rigidity and torsional performance, further enhancing the overall performance of the shock absorber.

[0053] The loading end 1, working area 3, and piston end 2 are integrally welded together by friction welding process; the outer surface of the working area 3 is chrome-plated and undergoes dehydrogenation treatment within 24 hours after chrome plating.

[0054] By selecting appropriate materials for each section, an optimal balance between performance and cost is achieved. The mounting end 1 and piston end 2 use cold-forged material 10B21, whose excellent cold-forging formability and initial strength ensure a reliable connection with the shock absorber mounting structure and stable load transmission to the piston assembly, preventing assembly loosening or load transmission failure. The working area 3 uses precision seamless steel pipe 35#, which combines good mechanical properties with lightweight characteristics, effectively bearing the reciprocating load during shock absorber operation, reducing overall weight and lowering energy consumption. Friction welding process achieves three-section integrated molding, resulting in higher weld strength and better consistency compared to traditional welding methods, avoiding weak links caused by multi-section connections. Chrome plating of the working area 3 improves corrosion resistance and extends service life, and hydrogen removal treatment within 24 hours effectively eliminates the risk of hydrogen embrittlement, preventing fracture accidents caused by hydrogen embrittlement during operation, and significantly improving the safety and durability of the piston rod.

[0055] The overall dimensional accuracy of the piston rod body meets the following requirements: surface straightness ≤ 0.01 / 100, roundness ≤ 0.01; surface roughness meets the following requirement: Ra < 0.063;

[0056] Clearly defining the overall dimensional accuracy and surface roughness requirements of the piston rod body provides crucial assurance for the stable operation of the vibration damper. High-precision standards, such as surface straightness ≤0.01 / 100 and roundness ≤0.01, ensure the coaxiality of the piston rod's reciprocating motion during vibration damper operation, preventing motion jamming or accelerated localized wear due to geometric deviations, reducing abnormal wear on internal components, and extending the overall service life of the vibration damper. Simultaneously, high-precision geometric dimensions ensure uniform clearance between the piston assembly and the cylinder inner wall, preventing hydraulic shocks caused by uneven clearances, and improving the vibration damping effect and operational stability of the vibration damper. A surface roughness Ra <0.063 reduces the friction coefficient between the piston rod and the seals during piston rod movement, reducing frictional loss, improving sealing performance, preventing hydraulic oil leakage, ensuring the efficiency of the vibration damper's hydraulic system, and reducing heat generated by friction, avoiding the impact of localized overheating on material properties, further enhancing the reliability of the piston rod and the operational stability of the vibration damper.

[0057] A method for manufacturing a lightweight vibration damper piston rod, characterized by comprising the following steps:

[0058] S1. Raw material pretreatment: Pre-process the loading end 1, piston end 2 and working area 3 respectively to ensure that the initial dimensions of each component meet the design requirements;

[0059] S2. Heat treatment at both ends: Before subsequent machining of the loading end 1 and piston end 2, heat treatment is performed on them to improve the material strength and subsequent welding adaptability.

[0060] S3. Friction welding: The pre-treated loading end 1 and piston end 2 are continuously welded to the working area 3 through friction welding to form an integrated structure. Friction parameters are controlled during the welding process to avoid multiple layers and multiple weld marks.

[0061] S4. Initial inspection of weld strength: After the weld is welded, a preliminary visual inspection is carried out. After confirming that there are no defects visible to the naked eye, the weld will proceed to chrome plating.

[0062] S5. Chrome plating: Chrome plating is applied to the surface of working area 3 to improve corrosion resistance;

[0063] S6. Dehydrogenation treatment: Dehydrogenation treatment is carried out within 24 hours after chrome plating, and the treated piston rod is kept at 260℃ for 1 hour to eliminate the risk of hydrogen embrittlement.

[0064] S7. Dimensional and performance fine inspection: The surface roughness, straightness, roundness, chrome plating thickness and weld appearance of the piston rod are inspected in sequence to ensure that they meet the design requirements;

[0065] S8. Comprehensive performance test: The finished piston rod is subjected to fatigue strength test, static strength test, impact resistance test and salt spray test in sequence. The final qualified product is determined after all tests are passed.

[0066] Through a step-by-step, meticulous process design, the quality and performance of the lightweight shock absorber piston rod are fully guaranteed. S1 raw material pretreatment ensures that the initial dimensions of each component meet design requirements, laying a solid foundation for subsequent welding and processing, and preventing final product defects due to initial dimensional deviations. S2 end heat treatment enhances the material strength and weldability of the loading end 1 and piston end 2, reducing the risk of cracking during welding and strengthening the weld joint strength. S3 friction welding, a single-pass continuous welding process, forms an integrated structure, avoiding performance risks caused by multiple layers and weld marks, and improving overall structural stability. S4 initial weld strength inspection and S7 dimensional performance inspection form a dual quality control system, promptly screening out products that fail to meet appearance and dimensional standards, avoiding waste in subsequent processes. S5 chrome plating and S6 hydrogen removal treatment respectively improve corrosion resistance and eliminate hydrogen embrittlement risk. S8 comprehensive performance testing fully verifies the piston rod's fatigue strength, static strength, impact resistance, and corrosion resistance, ensuring the finished product can cope with complex working conditions, significantly reducing the probability of shock absorber failure during use, and improving product qualification rate.

[0067] In step S3, during the friction welding process, the temperature change curve and pressure feedback value of the welding area are monitored in real time, specifically including:

[0068] When the friction temperature T1 in the initial stage of welding exceeds the first preset threshold Ta, welding should be stopped immediately and the wear condition of the friction pair should be checked.

[0069] When T1 ≤ Ta but T1 > Tb, where Ta > Tb, record the current temperature and continuously monitor the rate of temperature change ΔT / Δt over the next 30 seconds:

[0070] If ΔT / Δt ≤ preset stability threshold K1 and pressure P ∈ [P1, P2], then maintain the current welding parameters and continue welding;

[0071] If ΔT / Δt>K1 or Then adjust the friction speed and axial pressure, and re-monitor the temperature and pressure stability within 30 seconds. If the conditions are still not met after adjustment, stop welding and replace the friction welding head.

[0072] After welding is completed, ultrasonic testing is used to check whether there are pores or cracks inside the weld. If the test is qualified, it proceeds to step S4; if the test is unqualified, the weld position is marked and the process is repeated in step S3 until the test results meet the requirements.

[0073] Introducing a real-time temperature and pressure monitoring mechanism during friction welding significantly improves the stability and reliability of welding quality. By setting temperature thresholds Ta and Tb, abnormally high temperatures in the initial stage of welding can be identified in a timely manner, avoiding a decline in welding quality due to friction pair wear and preventing material performance degradation caused by overheating. Monitoring and adjusting the temperature change rate ΔT / Δt and pressure P ensures that the welding process remains stable, avoiding insufficient weld strength or internal defects caused by parameter fluctuations. Ultrasonic flaw detection after welding can accurately identify hidden defects such as porosity and cracks inside the weld. Compared with visual inspection alone, it can better guarantee the internal quality of the weld and reduce the risk of later fracture due to internal defects. For products that fail flaw detection, they can be re-welded until they pass, preventing defective products from flowing into subsequent processes. This further improves the structural safety of the finished piston rod, ensuring that the weld area can work stably under reciprocating loads and extending its service life.

[0074] In step S4, the initial inspection of weld strength also includes a petal test: the welded joint is placed in a special bending fixture, and the weld is bent at 60° with the fixed fulcrum as the center. During the bending process, the load-displacement curve is monitored by a force sensor. When the ratio of the maximum bending load Fmax to the theoretically calculated value F0, Fmax / F0, is ≥0.9 and there are no visible cracks at the weld after bending, the weld strength is deemed to be qualified. If Fmax / F0 <0.9 or cracks appear, the weld strength is deemed insufficient, and the friction welding parameters need to be readjusted and step S3 is repeated.

[0075] By placing the welded joint in a specialized bending fixture and bending it 60°, combined with load-displacement curve monitoring using a force sensor, the bending load that the piston rod may bear in actual use can be realistically simulated. Compared with simple visual inspection, this method better reflects the actual load-bearing capacity of the weld. By using the criterion of Fmax / F0≥0.9, the weld strength requirements are quantified, avoiding subjective judgment errors and ensuring that the weld strength meets design requirements, preventing the piston rod from breaking under stress due to insufficient weld strength. If Fmax / F0<0.9 or cracks are found, the friction welding parameters can be adjusted in time and the welding can be re-welded. This can effectively correct welding process deviations, reduce product scrap due to weld problems, improve the pass rate of the welding process, ensure the load-bearing reliability of the overall piston rod structure, and ensure the safe operation of the vibration damper under complex working conditions.

[0076] In step S7, the straightness and roundness detection includes:

[0077] S71. Check the surface straightness L1 and roundness C1. If L1≤0.01 / 100 and C1≤0.01, it is considered qualified.

[0078] S72. If L1 > 0.01 / 100 or C1 > 0.01, then obtain the three-dimensional morphology curve of the entire piston rod length using a laser scanner, and analyze the distribution pattern of local out-of-tolerance areas:

[0079] S73. When the length of the out-of-tolerance area is less than 10% of the total length, it should be re-inspected after local grinding correction.

[0080] S74. When the length of the out-of-tolerance area is greater than or equal to 10% of the total length, or when the morphology curve shows continuous fluctuations exceeding the preset threshold R, it is determined that the overall processing deviation is too large. Then, proceed to S3 to re-weld or adjust the pre-processing dimensions.

[0081] S71 directly determines qualified products, improving inspection efficiency and avoiding unnecessary subsequent processing; S72 acquires three-dimensional morphology curves through a laser scanner, enabling precise analysis of the distribution patterns of local out-of-tolerance areas, providing a more comprehensive understanding of the piston rod's geometric deviation compared to traditional inspection methods; S73 performs localized grinding correction on products with out-of-tolerance areas less than 10% of the total length, maximizing raw material utilization, reducing waste, and lowering production costs; S74 determines severely out-of-tolerance products as having excessive overall processing deviations and returns them to S3 or adjusts pre-processing dimensions, enabling timely detection and resolution of systemic problems in the manufacturing process, preventing the recurrence of similar deviations, ensuring that the geometric accuracy of piston rods in subsequent production meets requirements, guaranteeing their compatibility with other components of the shock absorber, and improving the overall performance of the shock absorber.

[0082] In S8, the comprehensive performance test includes: a fatigue strength test using 2.5 million cycles of loading, with strain gauges used to monitor the stress change curve of the piston rod in real time.

[0083] When the number of cycles reaches 1 million times, if the deviation Δσ between the stress peak σ1 and the initial stress σ0 is ≤ 5%, the test continues;

[0084] If Δσ > 5%, the test is paused and the piston rod is checked for microcracks or stress concentration points. After repair, the counting starts from 0 again for the test;

[0085] When 2.5 million cycles are completed, if there are no cracks confirmed by magnetic particle inspection or penetrant testing, and the deformation amount ≤ 60% or there is no fracture after applying the ultimate load in the static strength test, and at the same time in the impact resistance test, that is, there is no fracture when a 100 kg hammer impacts the loading end 1 at a height of 0.8 m and there is no corrosion in the 72 - hour salt spray test, it is judged as a final qualified product;

[0086] If any one item does not meet the requirements, it is judged as an unqualified product;

[0087] The fatigue strength test uses 2.5 million cycles of loading and real - time monitors the stress changes, which can simulate the fatigue working conditions of the piston rod during long - term operation, and pre - detect the failure risks caused by fatigue in advance. The stress deviation inspection at 1 million cycles can timely detect early problems and repair them, avoiding waste of test resources; the non - destructive testing and static strength test after 2.5 million cycles further verify the structural strength of the piston rod, ensuring that it does not fracture or undergo excessive deformation under the ultimate load; the impact resistance test simulates accidental impact scenarios, and the salt spray test verifies the corrosion resistance. The two tests respectively ensure the reliability of the piston rod under special working conditions and harsh environments; only when all tests are qualified is it judged as a qualified product, which can effectively eliminate products with insufficient performance and improve the quality of finished products.

[0088] The comprehensive control of the straightness and roundness includes: in the inspection, if the straightness L1 and the roundness C1 simultaneously satisfy L1 ≤ 0.01 / 100 and C1 ≤ 0.01, the geometric accuracy is directly judged as qualified; if only L1 or C1 is singly out - of - tolerance, the out - of - tolerance item is corrected by compensation machining and then re - inspected; if both L1 and C1 are out - of - tolerance and the out - of - tolerance amount exceeds the cumulative threshold, it is judged as an overall forming defect, and it is necessary to return to S1 to re - select raw materials or adjust the pre - processing process until the piston rod manufactured subsequently meets the collaborative accuracy requirements of straightness and roundness;

[0089] The comprehensive control strategy for straightness and roundness realizes the precise control of geometric accuracy by differentiating and processing different out-of-tolerance situations. At the same time, it optimizes the production process and reduces costs. Products that meet both indicators are directly judged as qualified, improving the detection efficiency. For single out-of-tolerance products, compensation machining and correction are carried out, which can make full use of existing products, reduce scrap, and save raw material and manufacturing costs. For products with both out-of-tolerance and excessive out-of-tolerance, they are returned to S1 for processing, which can identify problems from the source, possibly involving raw material quality or pre-processing technology defects. Timely adjustment can avoid continuous occurrence of similar problems in subsequent production, improving the overall production stability and product qualification rate. This collaborative precision control method ensures that the geometric accuracy of the piston rod not only meets the requirements of single indicators, but more importantly, achieves overall adaptability, guarantees smooth movement in the shock absorber, reduces failures caused by geometric deviations, and improves the operating stability and service life of the shock absorber.

[0090] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A lightweight shock absorber piston rod and a manufacturing method thereof, characterized by: The piston rod body comprises: The loading end (1) is made of cold heading material 10B21, used for connecting with the shock absorber mounting structure and providing initial assembly strength; The piston end (2) is made of cold heading material 10B21, used for cooperating with the internal piston assembly of the shock absorber and transmitting load; The working area (3) is made of precision seamless steel pipe 35#, connected between the loading end (1) and the piston end (2), used for bearing the reciprocating load during the working of the shock absorber; The loading end (1), the working area (3) and the piston end (2) are integrally welded by friction welding process; the outer surface of the working area (3) is treated by chromium plating, and the dehydrogenation treatment is carried out within 24 hours after chromium plating.

2. A lightweight shock absorber piston rod according to claim 1, characterized in that The overall dimensional accuracy of the piston rod body satisfies: surface straightness ≤0.01 / 100, roundness ≤0.01; the surface roughness satisfies: Ra<0.

063.

3. A manufacturing method for the lightweight damper piston rod according to any one of claims 1 to 2, characterized in that The method comprises the following steps: S1, raw material pretreatment: the loading end (1), the piston end (2) and the working area (3) are pretreated respectively to ensure that the initial dimensions of each part meet the design requirements; S2, two-end heat treatment: before subsequent machining of the loading end (1) and the piston end (2), heat treatment is carried out to improve the material strength and subsequent welding adaptability; S3, friction welding: the pretreated loading end (1), the piston end (2) and the working area (3) are continuously welded by single pass by friction welding process to form an integrated structure, and the friction parameters are controlled during welding to avoid multi-layer and multi-pass welding marks; S4, initial inspection of weld strength: after welding, the weld is preliminarily inspected for appearance to confirm that there is no visible defect, and then chromium plating is carried out; S5, chromium plating treatment: the surface of the working area (3) is plated with chromium to improve corrosion resistance; S6, dehydrogenation treatment: dehydrogenation treatment is carried out within 24 hours after chromium plating, and the treated piston rod is placed in a 260℃ environment for 1 hour to eliminate the risk of hydrogen embrittlement; S7, size and performance precision inspection: the surface roughness, straightness, roundness, chromium plating layer thickness and weld appearance of the piston rod are detected in sequence to ensure that the design requirements are met; S8, comprehensive performance test: the finished piston rod is subjected to fatigue strength test, static strength test, impact resistance test and salt spray test in sequence, and is determined as a final qualified product after all tests are qualified.

4. The manufacturing method of a lightweight shock absorber piston rod according to claim 3, characterized by In S3, during the friction welding process, the temperature change curve and pressure feedback value of the welding area are monitored in real time, specifically including: When the friction temperature T1 at the initial stage of welding is greater than the first preset threshold value Ta, stop welding immediately and check the wear state of the friction pair; When T1≤Ta but T1>Tb, where Ta>Tb, record the current temperature and continuously monitor the temperature change rate ΔT / Δt in the next 30 seconds: If ΔT / Δt≤preset stable threshold value K1 and pressure P∈[P1,P2], then maintain the current welding parameters to continue welding; If ΔT / Δt > K1 or then adjust the friction rotation speed and axial pressure, re-monitor the temperature and pressure stability within 30s, if still not meet the conditions after adjustment, then suspend the welding and replace the friction welding head; After welding is completed, whether there are pores or cracks in the weld is detected by ultrasonic flaw detection, if the detection is qualified, it enters S4; if the detection is unqualified, the weld position is marked and friction welding is re-performed in S3 until the flaw detection result meets the requirements.

5. The manufacturing method of a lightweight shock absorber piston rod according to claim 3, characterized by In the S4, the initial inspection of the weld strength further comprises determining by the petal test: placing the welded joint in a special bending clamp, bending the weld position 60° around the fixed fulcrum, monitoring the load displacement curve through the force sensor during the bending process, when the ratio of the maximum bending load Fmax to the theoretical calculation value F0 Fmax / F0≥0.9 and no visible cracks at the weld after bending, the weld strength is determined to be qualified; if Fmax / F0<0.9 or cracks appear, the weld strength is determined to be insufficient, and the friction welding parameters need to be adjusted and S3 is repeated.

6. The manufacturing method of a lightweight shock absorber piston rod according to claim 3, characterized by In the S7, the straightness and roundness detection comprises: S71, detecting the surface straightness L1 and the roundness C1, if L1≤0.01 / 100 and C1≤0.01, then it is determined to be qualified; S72, if L1>0.01 / 100 or C1>0.01, then the three-dimensional topography curve of the full length of the piston rod is obtained by a laser scanner, and the distribution rule of the local out-of-tolerance area is analyzed: S73, when the length ratio of the out-of-tolerance area is less than 10% of the total length, the local polishing correction is performed and then re-detection is performed; S74, when the length ratio of the out-of-tolerance area is greater than or equal to 10% of the total length or the topography curve shows that the continuous fluctuation exceeds the preset threshold R, it is determined that the overall machining deviation is too large, and then S3 is returned to re-welding or adjusting the pre-machining size.

7. The manufacturing method of a lightweight shock absorber piston rod according to claim 3, characterized by In the S8, the comprehensive performance test comprises: the fatigue strength test adopts 2.5 million cycle loading, and the stress change curve of the piston rod is monitored in real time by a strain gauge: When the cycle number reaches 1 million times, if the deviation Δσ of the stress peak σ1 and the initial stress σ0 is less than or equal to 5%, the test continues; If Δσ>5%, the test is paused and the piston rod is checked for micro-cracks or stress concentration points, and then the test is restarted from 0 after repair; After completing 2.5 million cycles, no cracks are found by magnetic particle inspection or penetration detection, and the deformation amount is less than or equal to 60% or no fracture occurs after applying the limit load in the static strength test, and the impact resistance test, i.e. 100 kg iron hammer 0.8 m high impact on the loading end (1) without fracture and 72 h salt spray test without corrosion, is determined to be a final qualified product; If any one of the requirements is not met, it is determined to be an unqualified product.

8. The manufacturing method of a lightweight shock absorber piston rod according to claim 3, characterized by The comprehensive control of straightness and roundness comprises: in the detection, if the straightness L1 and the roundness C1 meet L1≤0.01 / 100 and C1≤0.01 at the same time, the geometric precision is directly determined to be qualified; if only L1 or C1 is out of tolerance, the out-of-tolerance item is corrected by compensation machining and then re-detection is performed; if both L1 and C1 are out of tolerance and the out-of-tolerance amount exceeds the cumulative threshold, it is determined that the overall forming defect exists, and the raw material needs to be selected again or the pre-machining process needs to be adjusted in S1 until the piston rod manufactured subsequently meets the coordinated accuracy requirements of straightness and roundness.

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