Process for manufacturing a high fatigue life vehicle hollow stabilizer bar

Abstract

The application discloses a preparation process of a high-fatigue-life vehicle hollow stabilizer bar, and relates to the technical field of vehicle parts.The specific steps of the preparation process are as follows: a blank preparation step, a cold bending forming step, a heat treatment step, an end treatment step and a final strengthening step.Through steel sand filling and end sealing treatment in the cold bending forming link, uniform radial support is provided for the inner wall of the pipe during pipe bending operation, the stability of the original cross-sectional shape of the pipe is maintained, local mechanical property fluctuation caused by cross-sectional deformation during pipe bending is avoided, and the consistency of the mechanical properties of the formed blank is ensured.Through the heat treatment process of step-by-step execution of quenching operation and tempering operation, the metallographic structure of the formed blank is controlled, the strength performance and the toughness performance of the material form a matched relationship, a stable metallographic structure basis is provided for the subsequent processing procedure and long-term service of the blank, and the uniformity and stability of the overall mechanical properties of the blank are ensured.

Description

Technical Field

[0001] This invention relates to the field of vehicle component technology, specifically to a manufacturing process for a high fatigue life hollow stabilizer bar for vehicles. Background Technology

[0002] With the rapid development of the automotive industry, the process of upgrading vehicle performance continues to accelerate. Vehicle handling stability, ride comfort, and driving safety have become core indicators of concern for OEMs and end markets. As a core component of the vehicle chassis, the automotive suspension system directly determines the vehicle's driving performance and ride experience. The stabilizer bar is a core safety component in the suspension system that suppresses body roll and balances the force on both wheels. Its service performance directly affects the vehicle's handling limits and driving safety. Under the industry trend of vehicle lightweighting, hollow stabilizer bars, with their lower weight and better material utilization, are gradually replacing traditional solid stabilizer bars and becoming the mainstream application solution for various passenger and commercial vehicles. 35CrMo alloy structural steel, with its excellent comprehensive mechanical properties, has become the core application material for high-load hollow stabilizer bars. There is a continuous and urgent market demand in the industry for high-durability and high-reliability manufacturing processes for hollow stabilizer bars made of this material.

[0003] However, the current industry-standard manufacturing process for hollow stabilizer bars made of 35CrMo material has several shortcomings. These shortcomings prevent it from meeting the high fatigue life requirements of high-performance vehicles. Existing cold bending processes cannot provide uniform internal support for the tubing, easily leading to changes in the cross-sectional shape of the bent area and causing deviations in the mechanical properties of the bent area compared to the straight section. General heat treatment processes lack sufficient precision in controlling the material's metallographic structure and hardness, easily causing an imbalance between the material's strength and toughness, failing to provide a stable microstructure for the long-term service of the stabilizer bar. Internal stress generated during end-processing cannot be effectively released, easily forming fatigue crack initiation points. Single surface strengthening processes cannot form a uniform and stable protective structure on the surface of the blank, making it difficult to suppress the propagation of surface micro-defects, ultimately resulting in the stabilizer bar's fatigue life failing to meet expectations. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a manufacturing process for a high-fatigue-life hollow stabilizer bar for vehicles. This invention utilizes steel grit filling and end sealing during the cold bending process to provide uniform radial support to the inner wall of the tube during bending, maintaining the stability of the original cross-sectional shape of the tube and avoiding localized mechanical property fluctuations caused by cross-sectional deformation during bending, thus ensuring the consistency of mechanical properties throughout the formed blank. Furthermore, through a heat treatment process involving quenching and tempering in separate steps, the metallographic structure of the formed blank is controlled, ensuring a suitable matching relationship between the material's strength and toughness properties. This provides a stable metallographic foundation for subsequent processing and long-term service, guaranteeing the uniformity and stability of the overall mechanical properties of the blank.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a manufacturing process for a high fatigue life hollow stabilizer bar for vehicles, the specific steps of which are as follows: Billet preparation steps: Select 35CrMo seamless steel pipe, cut it according to the product design dimensions, remove the burrs and flashes on the inside and outside of the seamless steel pipe opening to obtain the pipe billet; Cold bending forming steps: steel shot is filled into the tube blank and both ends of the tube blank are sealed. A CNC tube bending machine is used to complete the cold bending operation according to the bending angle and bending radius designed for the product, so as to obtain the stabilizer bar forming blank. Heat treatment steps: The stabilizer bar blank is sent into the quenching furnace, heated and held at the temperature, then immersed in the quenching liquid for quenching. After quenching, it is transferred to the tempering furnace for heating and holding at the temperature, then removed from the furnace and air-cooled to complete the tempering process, and the heat-treated blank is obtained. End treatment steps: Perform shot blasting on the heat-treated blank for the first time, and then flatten and drill the two ends of the heat-treated blank in sequence to remove burrs and flash from the hole openings and end faces. Then, send the heat-treated blank into the tempering furnace for low-temperature tempering to obtain the stress-relieved blank. Final shot blasting strengthening step: The stress-relieved blank is suspended in a walking beam shot blasting machine for a second shot blasting operation. After removal and cleaning, the finished stabilizer bar is obtained.

[0006] Furthermore, in the billet preparation step, the 35CrMo seamless steel pipe used has a specification of φ50×7. The cutting operation is completed by a CNC saw. The flatness deviation of both ends of the cut seamless steel pipe is <0.2mm. The burrs and flash on the inner and outer sides of the seamless steel pipe opening are removed by sanding.

[0007] Furthermore, in the cold bending forming step, during the steel sand filling and sealing process, steel sand is continuously filled into the inside of the pipe blank, the pipe wall of the pipe blank is simultaneously struck, and the two ends of the pipe blank are sealed with sealing heads and pipe clamps. Then, the sealed pipe blank is shaken for testing, thus completing the preparation work before the cold bending operation.

[0008] Furthermore, in the cold bending forming step, the steel grit is 40-70 mesh, the bending speed of the CNC pipe bending machine is 5-8° / s, and after the cold bending operation is completed, a stabilizer rod forming blank is obtained. The bending angle deviation is controlled within ±0.3° of the design angle, and the cross-sectional ellipticity of the bending area is controlled between 1.2-2.5%.

[0009] Furthermore, in the heat treatment step, during the quenching operation, the stabilizer bar blank is placed horizontally in a quenching furnace for heating and holding at a temperature of 850-870℃ for 35-45 minutes. Then, it is immersed in a quenching liquid, which is a PAG quenching liquid. During the quenching process, the temperature of the quenching liquid is 20-40℃. After quenching, the hardness of the stabilizer bar blank is controlled between HRC51 and 52.

[0010] Furthermore, in the heat treatment step, during the tempering process, the stabilizer bar forming blank that has completed the quenching process is transferred to the tempering furnace within 25-35 minutes, heated to 570-590℃ and held for 80-100 minutes, then taken out of the tempering furnace and placed in room temperature environment for natural air cooling. After tempering, the hardness of the stabilizer bar forming blank is controlled between HRC45-46.

[0011] Furthermore, in the end-processing step, the heat-treated blank is placed into a crawler-type shot blasting machine for the first shot blasting operation. The duration of the first shot blasting operation is 0.8-1.2 hours, and the shot blasting medium is 0.7-0.9 mm steel wire cut shot. After the first shot blasting operation is completed, a hydraulic head-pressing machine is used to flatten both ends of the heat-treated blank according to the design dimensions. Then, a vertical drilling machine is used to drill holes in the flattened areas at both ends of the heat-treated blank. The burrs and flashes at the hole openings and end faces are removed with sandpaper.

[0012] Furthermore, in the end-processing step, during the low-temperature tempering operation, the heat-treated blank after end processing is sent into a tempering furnace, heated to 320-340℃ and held for 4.5-5.5 hours. The heat-treated blank after heating and holding is then cooled to 80-120℃ in the tempering furnace and removed from the furnace. It is then placed in a room temperature environment for natural air cooling. The hardness of the heat-treated blank after tempering is controlled between HRC44-45.

[0013] Furthermore, in the final shot blasting strengthening step, the stress-relieved blank is suspended to the station of the walking shot blasting machine using a hanger. The suspension distance between adjacent stress-relieved blanks is adjusted to >200mm. During the secondary shot blasting operation, the stress-relieved blank rotates at a uniform speed with the station to complete the secondary shot blasting operation. The duration of the secondary shot blasting operation is 1.3-1.7h, and the shot blasting medium is 0.5-0.7mm steel wire cut shot. After the secondary shot blasting operation is completed, the stress-relieved blank is taken out and the surface is cleaned by compressed air to obtain the finished stabilizer bar.

[0014] Compared with existing technologies, the manufacturing process of this high fatigue life vehicle hollow stabilizer bar has the following advantages: I. This invention provides uniform radial support to the inner wall of the pipe during the bending process by filling it with steel grit and sealing the ends during the cold bending process. This maintains the stability of the original cross-sectional shape of the pipe and avoids local mechanical property fluctuations caused by cross-sectional deformation during bending, ensuring the consistency of mechanical properties throughout the formed blank. Through a heat treatment process that involves quenching and tempering in separate steps, the metallographic structure of the formed blank is controlled, so that the strength and toughness properties of the material are matched appropriately. This provides a stable metallographic basis for subsequent processing and long-term service, ensuring the uniformity and stability of the overall mechanical properties of the blank.

[0015] II. This invention arranges the initial shot blasting, end-finishing, and low-temperature tempering operations in sequence. Before end-finishing, the surface of the heat-treated blank is pretreated to eliminate micro-defects generated on the surface of the blank during heat treatment. Then, the low-temperature tempering operation after end-finishing fully releases the internal stress generated during end-finishing, avoiding the formation of fatigue crack sources due to residual stress. The secondary shot blasting operation further strengthens the surface of the low-temperature tempered blank, forming a uniform and stable stress structure on the surface of the blank, blocking the propagation path of micro-defects on the surface of the blank, and adapting to the long-term service requirements of the blank under alternating load conditions.

[0016] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0018] Figure 1 A flowchart illustrating the manufacturing process of a high-fatigue-life hollow stabilizer bar for vehicles; Figure 2 A framework diagram of the manufacturing process for a high fatigue life hollow stabilizer bar for vehicles; Figure 3 This is a framework diagram of the heat treatment steps in the manufacturing process of a hollow stabilizer bar for high fatigue life vehicles. Detailed Implementation

[0019] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below. Example

[0020] In the manufacturing of high fatigue life vehicle hollow stabilizer bars, the application is a φ50×7 specification 35CrMo vehicle hollow stabilizer bar, which is adapted to the high durability requirements of commercial vehicle suspension systems.

[0021] The billet preparation steps are as follows: The 35CrMo seamless steel pipe used is a high-alloy structural steel pipe with a specification of φ50×7. The chemical composition, mechanical properties, and dimensional tolerances of the seamless steel pipe all meet the industry-standard requirements for vehicle stabilizer bar manufacturing. The cutting operation is completed using a high-precision CNC metal band saw. During clamping, a V-shaped positioning fixture is used to correct the coaxiality of the seamless steel pipe, avoiding end-face tilting caused by clamping misalignment. The saw band speed is set to 80m / min and the feed speed to 15mm / min. Cutting to length according to the product design dimensions is then completed. After cutting, a digital height gauge and a flat crystal are used to check the flatness of both ends of the seamless steel pipe. The flatness deviation of both ends is measured to be 0.15mm. Subsequently, 100-grit metallographic sandpaper is used to grind the inner and outer sides of the pipe opening to completely remove burrs, flash, and sharp edges generated during cutting, resulting in the pipe billet. Figure 1 As shown.

[0022] Cold bending forming steps: Place the pipe blank on the operating frame. First, use a rubber sealing head and stainless steel pipe clamp to pre-seal one end of the pipe blank. Then, fill the inner cavity of the pipe blank with 60-mesh steel sand through a feeding funnel from the other end. During the filling process, continuously tap the pipe wall evenly along the pipe axis with a rubber hammer to eliminate internal gaps formed by steel sand bridging, ensuring that the steel sand is evenly and densely filled in the inner cavity of the pipe blank. After filling, seal the open end of the pipe with a rubber sealing head and pipe clamp of the same specification. After sealing, hold both ends of the pipe blank with both hands and shake it horizontally three times forcefully. No steel sand should be found moving out. The preparatory work for cold bending is completed after ensuring no noise is heard and no sand leakage is observed at the sealing point. The sealed pipe blank is then clamped into the special bending fixture of the CNC pipe bending machine. The bending positioning point is corrected, and the bending speed is set to 6° / s. The cold bending operation is completed according to the bending angle and radius designed for the product. After cold bending, a coordinate measuring machine is used to detect the bending angle. The deviation between the bending angle of the formed blank and the designed angle is measured to be 0.2°. Simultaneously, the major and minor axis dimensions of the cross-section in the bending area are measured, yielding an ellipticity of 1.8%. This results in the formation of the stabilizer bar blank. Figure 2 As shown.

[0023] The heat treatment process consists of two parts: quenching and tempering. The quenching furnace is a box-type resistance furnace with a PID temperature control system, achieving a temperature control accuracy of ±5℃. The tempering furnace is a pit-type tempering furnace of the same accuracy. The quenching fluid used is a 10% concentration PAG water-soluble quenching fluid, equipped with a circulating cooling system. During quenching, the stabilizer bar blanks are placed horizontally on a heat-resistant material rack, with a 10mm gap between the blanks to ensure uniform heating. After the quenching furnace reaches 860℃ and stabilizes at that temperature, the material rack is pushed into the furnace and held for 40 minutes. After holding, the stabilizer bar blanks are quickly removed and horizontally immersed in the PAG quenching fluid. The circulating cooling system maintains the quenching fluid temperature at 30℃. After quenching, the stabilizer bar blanks are removed. The blank was air-cooled to room temperature. Using a Rockwell hardness tester, three test points were evenly selected on the straight section of the stabilizer bar blank. The average hardness of the quenched blank was measured to be HRC 51.5. During tempering, the stabilizer bar blank, after quenching, was transferred to the tempering furnace within 30 minutes to avoid microstructural transformation caused by prolonged exposure to room temperature. After the tempering furnace reached 580℃ and stabilized, it was held for 90 minutes. After holding, the stabilizer bar blank was removed and allowed to air-cool naturally at room temperature. During air cooling, the stabilizer bar blank was prevented from contacting water or other cooling media. After cooling, the Rockwell hardness tester was used again, and the average hardness of the tempered blank was measured to be HRC 45.5. The heat-treated blank was then obtained. Figure 3 As shown.

[0024] End processing steps: First, perform the initial shot blasting operation. Place the heat-treated blank into a crawler-type shot blasting machine. The single loading amount should not exceed 60% of the machine's rated load capacity. Use 0.8mm steel wire cut shot as the blasting medium. Set the shot blasting machine's operating current to 20A and the shot blasting time to 1 hour. During the shot blasting process, the crawler alternates between forward and reverse rotation every 10 minutes to ensure that all outer surfaces of the heat-treated blank are evenly shot-treated without any dead corners. After shot blasting, remove the blank and use compressed air to blow away surface dust and residual shot. Then, perform end processing. Clamp the heat-treated blank after shot blasting into the positioning mold of the hydraulic end-pressing machine. Perform end-pressing and flattening operations according to the product design dimensions to ensure that both ends are flattened. The dimensions and coaxiality of the flattened area are consistent. The flattened heat-treated blank is then clamped into the drill jig of a vertical drilling machine, and drilling is performed according to the designed hole diameter. After drilling, burrs, flash, and sharp edges on the hole opening and end face are removed with 100-grit metallographic sandpaper. Finally, a low-temperature tempering operation is performed. The heat-treated blank with the completed end processing is neatly placed on the tempering furnace rack within 30 minutes. The heating temperature is set to 330℃ and held for 5 hours. After the holding time is completed, the blank is cooled to 100℃ in the furnace and then removed from the furnace and allowed to air cool naturally at room temperature. After cooling, the hardness of the heat-treated blank after tempering is tested with a Rockwell hardness tester. The average hardness of the heat-treated blank after tempering is measured to be HRC44.5, resulting in a stress-relieved blank.

[0025] Final polishing strengthening step: The stress-relieved blank is suspended to the feeding station of the walking beam shot blasting machine using a hanger. The preset spacing between adjacent hooks of the hanger is 220mm to ensure that the net spacing between adjacent stress-relieved blanks is 220mm. The shot blasting medium is 0.6mm steel wire cut shot. The shot blasting machine is set to a working current of 18A and a shot blasting time of 1.5h. During the shot blasting process, the hanger drives the stress-relieved blank to rotate at a constant speed of 5r / min to ensure that all outer surfaces of the stress-relieved blank are evenly shot-beared without any dead corners. After shot blasting, the blank is removed and the surface is thoroughly blown with 0.5MPa compressed air to remove residual shot and dust. After blowing, the final product stabilizer bar is obtained.

[0026] The finished stabilizer bar prepared in this embodiment was subjected to performance verification using a bench fatigue test method commonly used in the vehicle suspension stabilizer bar industry. The test parameters were: a loading force of 2.3 kN, a total displacement of 57 mm, an amplitude of 28.5 mm, a median of 8.5 mm, and a frequency of 1 Hz. The test results showed that the finished stabilizer bar had a failure cycle count of 146,000 cycles, and the performance dispersion coefficient of the 10 samples in the same batch was 3.2%, which can meet the high durability and high reliability requirements of high-performance vehicle suspensions for stabilizer bars. Example

[0027] In the context of manufacturing high fatigue life vehicle hollow stabilizer bars, the application is a φ50×7 specification 35CrMo vehicle hollow stabilizer bar, which is adapted to the durability requirements of mid-to-high-end commercial vehicle suspension systems; the materials and processing equipment used in this second embodiment are completely consistent with those in the first embodiment.

[0028] Billet preparation steps: The 35CrMo seamless steel pipe used is a common high-alloy structural steel pipe in the industry, with a specification of φ50×7. The cutting operation is completed using a high-precision CNC metal band saw. During clamping, a V-shaped positioning fixture is used to correct the coaxiality of the seamless steel pipe to avoid end face tilting caused by clamping misalignment. The saw band speed is set to 75m / min and the feed speed to 12mm / min. The cut to length is completed according to the product design dimensions. After cutting, a digital height gauge is used in conjunction with a flat crystal to check the flatness of both ends of the seamless steel pipe. The flatness deviation of the two ends is measured to be 0.18mm. Then, 80-grit metallographic sandpaper is used to grind the inner and outer sides of the pipe opening of the seamless steel pipe to completely remove the burrs, flash, and sharp edges generated during cutting, thus obtaining the pipe billet.

[0029] Cold bending forming steps: Place the prepared pipe blank on the operating frame. First, use a rubber sealing head and stainless steel pipe clamp to pre-seal one end of the pipe blank. Then, fill the inner cavity of the pipe blank with 50-mesh steel sand through a feeding funnel from the other end. During the filling process, continuously and evenly tap the pipe wall along the axial direction of the pipe blank with a rubber hammer to eliminate internal voids formed by steel sand bridging, ensuring that the steel sand is evenly and densely filled into the inner cavity of the pipe blank. After filling, seal the open end of the pipe blank with a rubber sealing head and pipe clamp of the same specification. After sealing, hold both ends of the pipe with both hands and shake it horizontally 4 times. With no steel sand movement noise and no sand leakage at the sealing point, preparations for the cold bending operation are complete. The sealed pipe blank is then clamped into the bending fixture of the CNC pipe bending machine, the bending positioning point is corrected, and the bending speed is set to 7° / s. The cold bending operation is completed according to the designed bending angle and radius. After cold bending, a coordinate measuring machine is used to detect the bending angle, and the deviation between the bending angle of the formed blank and the designed angle is measured to be 0.25°. Simultaneously, the major and minor axis dimensions of the cross-section in the bending area are detected, yielding an ellipticity of 2.1%, resulting in the stabilizer bar formed blank.

[0030] The heat treatment process consists of two parts: quenching and tempering. The quenching furnace is a box-type resistance furnace with a PID temperature control system, achieving a temperature control accuracy of ±5℃. The tempering furnace is a pit-type tempering furnace of the same accuracy. The quenching fluid used is a 12% PAG water-soluble quenching fluid, equipped with a circulating cooling system. During quenching, the stabilizer bar blanks are placed horizontally on a heat-resistant material rack, with a 10mm gap between the blanks to ensure uniform heating. After the quenching furnace reaches 855℃ and stabilizes at that temperature, the material rack is pushed into the furnace and held for 42 minutes. After holding, the stabilizer bar blanks are quickly removed and horizontally immersed in the PAG quenching fluid. The circulating cooling system maintains the quenching fluid temperature at 35℃. After quenching, the stabilizer bar blanks are removed. The stabilizer bar blank was air-cooled to room temperature. Four test points were evenly selected on the straight section of the stabilizer bar blank using a Rockwell hardness tester. The average hardness of the stabilizer bar blank after quenching was measured to be HRC51.2. During tempering, the stabilizer bar blank that had completed quenching was transferred to the tempering furnace within 32 minutes to avoid microstructural transformation caused by prolonged exposure to room temperature. After the tempering furnace was heated to 575℃ and held at that temperature for 95 minutes, it was removed and allowed to air-cool naturally at room temperature. During air cooling, the stabilizer bar blank was prevented from contacting water or other cooling media. After cooling, the Rockwell hardness tester was used again, and the average hardness of the tempered blank was measured to be HRC45.2, yielding the heat-treated blank.

[0031] End-end processing steps: First, perform an initial shot blasting operation. Place the heat-treated blank into a crawler-type shot blasting machine, with a single loading amount not exceeding 60% of the equipment's rated load capacity. Use 0.75mm steel wire cut shot as the blasting medium. Set the shot blasting machine's operating current to 19A and the shot blasting time to 1.1 hours. During the shot blasting process, the crawler alternates between forward and reverse rotation every 10 minutes to ensure that all outer surfaces of the heat-treated blank are evenly shot-treated without any dead corners. After shot blasting, remove the blank and use compressed air to blow away surface dust and residual shot. Then, perform end processing. Clamp the heat-treated blank after shot blasting into the positioning mold of the hydraulic end-forming machine and complete the end-flattening operation according to the product design dimensions. Ensure that the dimensions and coaxiality of the flattened areas at both ends are consistent; then, clamp the flattened heat-treated blank into the drill jig of the vertical drilling machine and complete the drilling operation according to the designed hole diameter. After drilling, use 80-grit metallographic sandpaper to remove burrs, flash, and sharp edges from the hole opening and end face. Finally, perform low-temperature tempering. Within 28 minutes, neatly place the heat-treated blank with the completed end processing on the tempering furnace rack, set the heating temperature to 325℃, and hold for 5.2 hours. After holding, cool with the furnace to 90℃, then remove from the furnace and allow to air cool naturally at room temperature. After cooling, use a Rockwell hardness tester to test the hardness. The average hardness of the tempered blank is measured to be HRC44.2, resulting in a stress-relieved blank.

[0032] Final polishing strengthening step: The stress-relieved blank is suspended by a hanger to the feeding station of the walking beam shot blasting machine. The preset spacing between adjacent hooks of the hanger is 210mm to ensure that the net spacing between adjacent blanks is 210mm. The shot blasting medium is 0.55mm steel wire cut shot. The shot blasting machine is set to a working current of 17A and a shot blasting time of 1.6h. During the shot blasting process, the hanger drives the stress-relieved blank to rotate at a constant speed of 5r / min to ensure that all outer surfaces of the stress-relieved blank are evenly shot-beared without any dead corners. After shot blasting, the blank is removed and the surface of the stress-relieved blank is thoroughly blown with 0.55MPa compressed air to remove residual shot and dust. After blowing, the finished stabilizer bar is obtained.

[0033] The finished stabilizer bar prepared in Example 2 was subjected to performance verification using the same bench fatigue test method as in Example 1. The test parameters were: loading force 2.3KN, total displacement 57mm, amplitude 28.5mm, median 8.5mm, and frequency 1Hz. The test results showed that the finished stabilizer bar had a failure cycle count of 139,000 cycles, and the performance dispersion coefficient of the 10 samples in the same batch was 4.1%. These performance indicators still far exceed the manufacturing level of conventional processes in the industry, and can meet the durability and reliability requirements of stabilizer bars for mid-to-high-end vehicle suspensions, and can still stably improve the fatigue life of stabilizer bars.

[0034] Comparative example: In the context of manufacturing high fatigue life vehicle hollow stabilizer bars, this comparative example demonstrates the conventional manufacturing process for vehicle hollow stabilizer bars. The application is completely consistent with Examples 1 and 2, specifically a φ50×7 specification 35CrMo vehicle hollow stabilizer bar. The materials and processing equipment used are also consistent with Examples 1 and 2.

[0035] Billet preparation steps: The 35CrMo seamless steel pipe used is a common high-alloy structural steel pipe in the industry, with a specification of φ50×7. The cutting operation is completed using the same high-precision CNC metal band saw as in Example 1. During clamping, a V-shaped positioning fixture is used to correct the coaxiality of the seamless steel pipe. The saw band speed is set to 80m / min and the feed speed is set to 15mm / min. The fixed-length cutting is completed according to the same product design dimensions as in Example 1. After cutting, a digital height gauge is used in conjunction with a flat crystal to check the flatness of both ends of the steel pipe. The flatness deviation of the two ends is measured to be 0.16mm. Then, 100-grit metallographic sandpaper is used to grind the inner and outer sides of the pipe opening of the seamless steel pipe to completely remove the burrs, flash, and sharp edges generated during cutting, thus obtaining the pipe billet.

[0036] Cold bending forming steps: The prepared pipe blank is directly clamped into the special bending fixture of the CNC pipe bending machine, which is the same as in Example 1. The bending positioning point is corrected, the bending speed is set to 6° / s, and the bending angle and bending radius are exactly the same as in Example 1. The cold bending operation is completed using the industry-standard air bending process. During the cold bending process, there is no filling support structure in the inner cavity of the pipe, nor is any internal auxiliary support treatment done. After the cold bending is completed, the bending angle is detected by a coordinate measuring machine. The deviation between the bending angle of the formed blank and the design angle is measured to be 0.35°. At the same time, the major axis and minor axis dimensions of the cross section of the bending area are detected, and the ellipticity of the cross section is found to be 10.8%, thus obtaining the stabilizer rod formed blank.

[0037] End processing steps: After the cold bending forming operation is completed, the end processing of the stabilizer bar forming blank is performed directly without a pre-heat treatment process. The stabilizer bar forming blank is clamped into the positioning mold of the hydraulic end-forming machine, which is the same as in Example 1. The end flattening operation is completed according to the same product design dimensions as in Example 1, ensuring that the dimensions and coaxiality of the flattened areas at both ends are consistent. Then, the flattened stabilizer bar forming blank is clamped into the drilling jig of the vertical drilling machine, which is the same as in Example 1. The drilling operation is completed according to the same design hole diameter as in Example 1. After drilling, burrs, flashes and sharp edges on the hole opening and end face are removed with 100-grit metallographic sandpaper to complete the end processing and obtain the end-processed blank.

[0038] Heat treatment steps: A one-step quenching and tempering overall heat treatment process was adopted. The quenching furnace, tempering furnace, and quenching liquid used were consistent with those in Example 1, without graded heat treatment or subsequent stress-relieving tempering process. The end-machined blanks were placed horizontally on a heat-resistant material rack. After the quenching furnace was heated to 860°C and held at a stable temperature, the material rack was pushed into the furnace and held for 40 minutes. After the holding time was completed, the blanks were quickly removed and immersed in PAG quenching liquid to complete the quenching operation. After quenching, the blanks were removed and air-cooled to room temperature. Then, the quenched blanks were transferred to a tempering furnace, heated to 620°C and held at a stable temperature for 90 minutes. After the holding time was completed, the blanks were removed and placed in a room temperature environment for natural air cooling. After cooling, the Rockwell hardness tester was used to test the hardness of the tempered blanks. The average hardness of the tempered blanks was measured to be HRC40, and the heat-treated blanks were obtained.

[0039] Surface shot blasting steps: Place the heat-treated blank into a tracked shot blasting machine identical to that in Example 1. The single loading amount shall not exceed 60% of the rated loading capacity of the equipment. The shot blasting medium is 0.8mm steel wire cut shot. Set the working current of the shot blasting machine to 20A. Use a single-pass whole shot blasting process without graded shot blasting or step shot blasting. The shot blasting time is 1.5 hours. During the shot blasting process, the track alternates between forward and reverse rotation every 10 minutes to ensure that the outer surface of the heat-treated blank is uniformly shot-blasted. After shot blasting is completed, remove the blank and blow off the surface dust and residual shot with compressed air to obtain the finished stabilizer bar.

[0040] The finished stabilizer bar prepared in this comparative example was subjected to performance verification using the same bench fatigue test method as in Examples 1 and 2. The test parameters were: loading force 2.3KN, total displacement 57mm, amplitude 28.5mm, median 8.5mm, and frequency 1Hz. The test results showed that the failure cycle of the finished stabilizer bar was 81,000 cycles, and the performance dispersion coefficient of the 10 samples in the same batch was 12.6%.

[0041] In summary, both Examples 1 and 2 utilize a comprehensive, coordinated process involving steel shot-assisted cold bending, precise graded heat treatment, low-temperature stress-relieving tempering after end machining, and secondary graded shot blasting. The resulting stabilizer bars exhibit higher fatigue life than the comparative example using conventional processes, with lower batch performance dispersion coefficients. This demonstrates significant advantages in product consistency and service reliability. Example 1 achieved superior fatigue life performance through precise matching of process parameters, while Example 2 achieved stable high fatigue life performance by adjusting process parameters, validating the parameter adaptability and process stability of the technology. This approach systematically addresses the core pain points of conventional industry processes, such as insufficient forming precision, imbalance between strength and toughness, inadequate residual stress release, and limited surface strengthening effects. It can stably produce high-fatigue-life hollow stabilizer bars that meet the requirements of high-performance vehicle suspensions.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A manufacturing process for a high fatigue life hollow stabilizer bar for vehicles, characterized in that, The specific steps of this preparation process are as follows: Billet preparation steps: Select 35CrMo seamless steel pipe, cut it according to the product design dimensions, remove the burrs and flashes on the inside and outside of the seamless steel pipe opening to obtain the pipe billet; Cold bending forming steps: steel shot is filled into the tube blank and both ends of the tube blank are sealed. A CNC tube bending machine is used to complete the cold bending operation according to the bending angle and bending radius designed for the product, so as to obtain the stabilizer bar forming blank. Heat treatment steps: The stabilizer bar blank is sent into the quenching furnace, heated and held at the temperature, then immersed in the quenching liquid for quenching. After quenching, it is transferred to the tempering furnace for heating and holding at the temperature, then removed from the furnace and air-cooled to complete the tempering process, and the heat-treated blank is obtained. End treatment steps: Perform shot blasting on the heat-treated blank for the first time, and then flatten and drill the two ends of the heat-treated blank in sequence to remove burrs and flash from the hole openings and end faces. Then, send the heat-treated blank into the tempering furnace for low-temperature tempering to obtain the stress-relieved blank. Final shot blasting strengthening step: The stress-relieved blank is suspended in a walking beam shot blasting machine for a second shot blasting operation. After removal and cleaning, the finished stabilizer bar is obtained.

2. The manufacturing process of a high fatigue life hollow stabilizer bar for vehicles according to claim 1, characterized in that, In the billet preparation step, the 35CrMo seamless steel pipe used has a specification of φ50×7. The cutting operation is completed by a CNC saw. The burrs and flash on the inside and outside of the seamless steel pipe opening are removed by sanding.

3. The manufacturing process of a high fatigue life vehicle hollow stabilizer bar according to claim 1, characterized in that, In the cold bending forming step, during the steel sand filling and sealing process, steel sand is continuously filled into the inside of the pipe blank, the pipe wall of the pipe blank is simultaneously struck, and the two ends of the pipe blank are sealed with sealing heads and pipe clamps. Then, the sealed pipe blank is shaken to test, thus completing the preparation work before the cold bending operation.

4. The manufacturing process of a high fatigue life hollow stabilizer bar for vehicles according to claim 1, characterized in that, In the cold bending forming step, the steel grit has a mesh size of 40-70, the bending speed of the CNC pipe bending machine is 5-8° / s, and the stabilizer bar blank is obtained after the cold bending operation is completed.

5. The manufacturing process of a high fatigue life hollow stabilizer bar for vehicles according to claim 1, characterized in that, In the heat treatment step, during the quenching operation, the stabilizer rod blank is placed horizontally in the quenching furnace for heating and heat preservation. The heating temperature is 850-870℃, and the heat preservation time is 35-45 minutes. Then, it is immersed in the quenching liquid for quenching. The quenching liquid is PAG quenching liquid, and the temperature of the quenching liquid during the quenching process is 20-40℃.

6. The manufacturing process of a high fatigue life hollow stabilizer bar for vehicles according to claim 1, characterized in that, In the heat treatment step, during the tempering process, the stabilizer bar blank that has completed the quenching process is transferred to the tempering furnace within 25-35 minutes, heated to 570-590℃ and held for 80-100 minutes, then taken out of the tempering furnace and placed in a room temperature environment for natural air cooling.

7. The manufacturing process of a high fatigue life vehicle hollow stabilizer bar according to claim 1, characterized in that, In the end-processing step, the heat-treated blank is placed into a crawler shot blasting machine for the first shot blasting operation. The duration of the first shot blasting operation is 0.8-1.2 hours, and the shot blasting medium is 0.7-0.9 mm steel wire cut shot. After the first shot blasting operation is completed, a hydraulic head-pressing machine is used to flatten both ends of the heat-treated blank according to the design dimensions. Then, a vertical drilling machine is used to drill holes in the flattened areas at both ends of the heat-treated blank. The burrs and flashes at the hole openings and end faces are removed with sandpaper.

8. The manufacturing process of a high fatigue life vehicle hollow stabilizer bar according to claim 1, characterized in that, In the end-processing step, during the low-temperature tempering operation, the heat-treated blank after the end processing is sent into the tempering furnace, heated to 320-340℃ and held for 4.5-5.5 hours. After the heat-treated blank is cooled to 80-120℃ in the tempering furnace, it is taken out of the furnace and placed in a room temperature environment for natural air cooling.

9. The manufacturing process of a high fatigue life vehicle hollow stabilizer bar according to claim 1, characterized in that, In the final shot blasting strengthening step, the stress-relieved blank is suspended to the station of the walking beam shot blasting machine using a hanger. The suspension distance between adjacent stress-relieved blanks is adjusted to >200mm. During the secondary shot blasting operation, the stress-relieved blank rotates at a uniform speed with the station to complete the secondary shot blasting operation. The duration of the secondary shot blasting operation is 1.3-1.7h, and the shot blasting medium is 0.5-0.7mm steel wire cut shot. After the secondary shot blasting operation is completed, the stress-relieved blank is taken out and the surface is cleaned by compressed air to obtain the finished stabilizer bar.

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