Method for manufacturing ball pin and ball pin

Abstract

The application discloses a preparation method of a ball pin and the ball pin and belongs to the technical field of vehicles. After a ball head to be processed is obtained, surface hardening treatment is performed on the ball head, so that a surface hardening layer is formed on the surface of the ball head. The hardness of the surface hardening layer is greater than the hardness of the inside of the ball head and greater than the hardness of a rod body. The surface hardening layer covers the ball head. After the ball head is installed in a ball seat, the surface hardening layer isolates the ball head from the ball seat, and the surface hardening layer is in contact with the inner wall of the ball seat. During rotation of the ball head in the ball seat relative to the ball seat, the surface hardening layer and the inner wall of the ball seat are in mutual friction. The hardness of the surface hardening layer is relatively large, so that the wear resistance of the surface hardening layer is relatively good, and the surface hardening layer is not easily damaged, so that rotation of the ball head in the ball seat relative to the ball seat is more smooth. The ball head and the rod body are separately manufactured, so that the surface hardening treatment process of the ball head does not affect the rod body, the strength of the rod body is not reduced, and the rod body is not easily broken.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, and in particular to a method for preparing a ball pin and the ball pin itself. Background Technology

[0002] In a vehicle, ball joints can be installed at the ends of control arms or thrust rods in the suspension system, connecting the control arms or thrust rods to the wheels. During vehicle movement, the steering force from the steering wheel is transmitted to the wheels via the ball joints on the control arms. The rotation and oscillation of these ball joints allow for the vertical movement and steering of the wheels.

[0003] The ball joint consists of a ball head and a rod body connected together. The ball head is rotatably connected to a ball seat fixed to the end of the control arm or thrust rod, and the rod body is connected to the wheel. As the ball head rotates within the ball seat, it can drive the rod body to rotate or swing, thereby realizing the up-and-down movement and steering motion of the wheel.

[0004] However, the low hardness of the ball head in the current ball pin results in low wear resistance on the surface of the ball head, which in turn makes the ball head more susceptible to damage during rotation relative to the ball seat. Summary of the Invention

[0005] This application provides a method for preparing a ball pin and a ball pin in general. This solves the problem that the ball head in existing ball pins is easily damaged. The technical solution is as follows: On the one hand, a method for preparing a ball pin is provided, the method comprising: Provide the ball head to be processed; The ball head is subjected to surface hardening treatment to form a surface hardening layer on the surface of the ball head; the surface hardening layer covers the ball head; Provide the rod to be processed; The ball head and the end of the rod body are connected after surface hardening treatment to obtain the ball pin; The surface hardening layer has a harder hardness than the interior hardness of the ball head and is also harder than the rod body.

[0006] In one implementation, surface hardening treatment of the ball head includes: The ball head is subjected to carburizing treatment; The carburized ball head is then quenched. The quenched ball head is then subjected to tempering treatment.

[0007] In one implementation, surface hardening treatment of the ball head further includes: After the ball head is quenched and before it is tempered, a first hardness test is performed on the ball head. After detecting that the hardness of the ball head is greater than or equal to the first hardness threshold, the ball head is subjected to tempering treatment.

[0008] In one implementation, surface hardening treatment of the ball head further includes: After the ball head is quenched and before it is tempered, the ball head is subjected to a first cleaning process.

[0009] In one implementation, carburizing the ball head further includes: Before carburizing the ball head, the ball head undergoes a homogenization treatment.

[0010] In one implementation, the method further includes: The ball head, after surface hardening treatment, is subjected to a second hardness test. After detecting that the surface hardness of the ball head is within a preset hardness range and the thickness of the surface hardened layer of the ball head is within a preset thickness range, the step of connecting the ends of the ball head and the shaft is performed.

[0011] In one implementation, the preset hardness range is 600HV to 780HV, and the preset thickness range is 0.3 mm to 0.6 mm.

[0012] In one implementation, the ends of the ball head and the rod body are connected after surface hardening treatment, including: The ends of the ball head and the rod body are welded after surface hardening treatment; After the welded area between the ball head and the end of the rod has cooled, the welded area is subjected to tempering treatment.

[0013] In one implementation, tempering is performed on the welded location, including: Electricity is applied to the welding position to heat it.

[0014] On the other hand, a ball pin is provided, which is prepared using the preparation method of this application.

[0015] In one implementation, the ball pin includes: a ball head and a shaft; the surface of the ball head has a surface-hardened layer covering the ball head; the end of the shaft is connected to the ball head having the surface-hardened layer. The surface hardening layer has a harder hardness than the interior hardness of the ball head and is also harder than the rod body.

[0016] In another aspect, a vehicle is provided, comprising: a suspension system and wheels, and the aforementioned ball joint, wherein the ball head of the ball joint is connected to the suspension system, and the rod of the ball joint is connected to the wheels.

[0017] The beneficial effects of the technical solutions provided in this application include at least the following: After obtaining the ball head to be processed, a surface hardening treatment can be performed on the ball head to form a surface hardened layer. The hardness of the surface hardened layer is greater than the hardness of the ball head's interior and greater than the hardness of the shaft. This surface hardened layer covers the ball head, and after the ball head is installed in the nut, it isolates the ball head from the nut, while the surface hardened layer contacts the inner wall of the nut. Therefore, during the ball head's rotation relative to the nut, the surface hardened layer rubs against the inner wall of the nut. The high hardness of the surface hardened layer results in good wear resistance and reduces the likelihood of damage, ensuring smoother rotation of the ball head relative to the nut. Furthermore, the ball head and shaft are manufactured separately, ensuring that the surface hardening process on the ball head does not affect the shaft, maintaining its strength and reducing the risk of breakage. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a ball pin provided in an embodiment of this application; Figure 2 This is a flowchart illustrating a method for preparing a ball pin according to an embodiment of this application; Figure 3 This is a flowchart of another method for preparing a ball pin provided in an embodiment of this application; Figure 4 This is a flowchart illustrating a method for manufacturing a ball head using a forging process, as provided in an embodiment of this application. Figure 5 This is a flowchart illustrating a method for surface hardening of a ball head according to an embodiment of this application; Figure 6 This is a flowchart of another method for surface hardening of a ball head provided in an embodiment of this application; Figure 7 This is a flowchart illustrating another method for surface hardening of a ball head provided in this application embodiment; Figure 8This is a flowchart illustrating another method for surface hardening of a ball head provided in this application embodiment; Figure 9 This is a flowchart illustrating a method for connecting the ball head and the end of the rod according to an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0021] like Figure 1 As shown, Figure 1 This is a schematic diagram of a ball joint provided in an embodiment of this application. The ball joint may include a ball head 100 and a rod body 200, which are fixedly connected. A ball seat may be fixedly connected to the end of a control arm or thrust rod in the vehicle, and the ball head 100 in the ball joint may be rotatably connected to the ball seat inside the ball seat. The rod body 200 in the ball joint may be fixedly connected to the wheel hub. Thus, during vehicle operation, as the ball head 100 in the ball joint rotates within the ball seat, it can drive the rod body 200 to rotate or swing, thereby achieving the up-and-down movement and steering motion of the wheel.

[0022] In existing technology, the ball head and shaft of a ball joint are generally manufactured as a single piece using a forging process. However, the surface hardness of a ball head manufactured by forging is relatively low, which makes the surface of the ball head more susceptible to damage during rotation within the ball seat, resulting in uneven rotation of the ball head within the ball seat.

[0023] Since the rod in the ball joint is used to connect to the wheel hub, the rod needs to have high strength to prevent breakage. In existing technology, the surface hardness of the ball head is generally increased by heat treating the entire ball joint. However, heat treatment reduces the overall strength of the ball joint, leading to a decrease in the strength of the rod itself and making it more prone to breakage.

[0024] This application provides a method for preparing a ball pin, which is used to prepare a ball pin. Please refer to... Figure 2 , Figure 2 This is a flowchart illustrating a method for preparing a ball pin according to an embodiment of this application. The method for preparing a ball pin may include: Step 101: Provide the ball head to be processed.

[0025] Here, the ball head can be manufactured using a forging process, and the ball head manufactured using a forging process is the ball head to be processed.

[0026] Step 102: Perform surface hardening treatment on the ball head to form a surface hardening layer on the surface of the ball head.

[0027] Here, the surface-hardened layer can cover the ball head. In this way, after the ball head is installed in the ball seat, as the ball head rotates relative to the ball seat, the surface-hardened layer covering the surface of the ball head can isolate the ball head from the ball seat, and the surface-hardened layer can contact the inner wall of the ball seat.

[0028] Step 103: Provide the rod to be processed.

[0029] Here, the shaft can be manufactured using a forging process, and the shaft manufactured using this process is the shaft to be processed. It should be noted that the ball head and shaft can be manufactured separately.

[0030] Step 104: Connect the surface-hardened ball head and the end of the shaft to obtain the ball pin.

[0031] Here, the ball head and shaft, which are manufactured separately, are fixed together to form the ball pin.

[0032] In this application, the hardness of the surface hardening layer can be greater than the hardness inside the ball head, and can also be greater than the hardness of the shaft.

[0033] In this way, the surface-hardened layer covers the ball head. After the ball head is installed in the ball seat, the surface-hardened layer can isolate the ball head from the ball seat, while the surface-hardened layer contacts the inner wall of the ball seat. Therefore, during the rotation of the ball head relative to the ball seat, the surface-hardened layer rubs against the inner wall of the ball seat. The high hardness of the surface-hardened layer makes it more wear-resistant and less prone to damage, ensuring smoother rotation of the ball head relative to the ball seat.

[0034] Furthermore, the ball head and shaft of the ball pin are manufactured separately, so the surface hardening process of the ball head will not affect the shaft, the strength of the shaft will not be reduced, and the shaft is not easy to break.

[0035] In summary, this application provides a method for manufacturing a ball joint, wherein the ball head and the shaft are manufactured separately. After obtaining the ball head to be processed, a surface hardening treatment can be performed on the ball head to form a surface hardening layer. The hardness of the surface hardening layer is greater than the hardness of the ball head's interior and greater than the hardness of the shaft. Thus, the surface hardening layer covers the ball head, and after the ball head is installed in the ball seat, the surface hardening layer can isolate the ball head from the ball seat, while the surface hardening layer contacts the inner wall of the ball seat. Therefore, during the rotation of the ball head relative to the ball seat within the ball seat, the surface hardening layer rubs against the inner wall of the ball seat. The high hardness of the surface hardening layer results in good wear resistance and makes it less prone to damage, ensuring smoother rotation of the ball head relative to the ball seat within the ball seat. Furthermore, the separate manufacturing of the ball head and the shaft ensures that the surface hardening process of the ball head does not affect the shaft, the strength of the shaft is not reduced, and the shaft is less prone to breakage.

[0036] Please refer to Figure 3 , Figure 3 This is a flowchart illustrating another method for preparing a ball pin according to an embodiment of this application. This method for preparing a ball pin may include: Step 201: Provide the ball head to be processed.

[0037] In this embodiment of the application, the ball head can be manufactured by forging, and the ball head manufactured by forging is the ball head to be processed.

[0038] In the embodiments of this application, please refer to Figure 4 , Figure 4 This is a flowchart illustrating a method for manufacturing a ball end using a forging process, as provided in an embodiment of this application. The manufacturing of a ball end using a forging process may include: Step 2011: Select round steel and inspect it.

[0039] In this application, the round steel bar is a solid steel material with a circular cross-section. It should be noted that the ball head in the ball pin has a spherical or hemispherical structure. Therefore, round steel bar is chosen to manufacture the ball head, which facilitates its forming.

[0040] The inspection of round steel bars can include: document verification, visual inspection, and dimensional deviation checking. Specifically, document verification can include: checking the product certificate, factory inspection report, and quality assurance certificate of the steel, and verifying the label. Visual inspection can include: inspecting the surface of the round steel bars to ensure that there are no cracks, scabs, or delamination. Dimensional deviation checking includes: after selecting round steel bars of suitable diameter, randomly selecting round steel bars and measuring their diameter to ensure that the diameter deviation of the round steel bars does not exceed the national standard allowable deviation.

[0041] Step 2012: Heating and cutting the qualified round steel bars.

[0042] In this application, the temperature of the round steel after heating and blanking needs to meet the forging temperature of subsequent steps. In one implementation, heating and blanking the round steel may include: first placing the round steel into a heating furnace to heat it until the round steel reaches the forging temperature, then removing the round steel from the heating furnace and placing it in the forging station of the forging equipment.

[0043] Step 2013: Forge the round steel to obtain a ball head.

[0044] In this application, round steel bars can be forged using forging equipment. In one implementation, after the heated and blanked round steel bars are placed in the forging station of the forging equipment, the forging equipment can continuously forge the round steel bars until a spherical or hemispherical ball head is obtained. For example, the forging equipment can be an air hammer device.

[0045] Step 2014: Inspect the forged ball head.

[0046] In this application, the forged ball head is inspected, including visual inspection and dimensional inspection. Specifically, visual inspection may include checking the surface of the forged ball head to ensure that the surface is free of cracks, scabs, and delamination. Dimensional inspection includes measuring the diameter and roundness of the forged ball head to ensure that dimensional deviations do not exceed the allowable deviations specified in national standards.

[0047] Step 2015: Clean the qualified ball heads.

[0048] In this application, cleaning the ball head can remove oxide scale, dust, oil and residual iron filings from the surface of the forged ball head, thereby improving surface cleanliness and meeting the requirements of subsequent processing steps.

[0049] Step 202: Perform surface hardening treatment on the ball head to form a surface hardening layer on the surface of the ball head.

[0050] In this embodiment, the surface-hardened layer can cover the ball head. The hardness of the surface-hardened layer can be greater than the hardness inside the ball head and greater than the hardness of the shaft. Thus, after the ball head is installed in the saddle, during its rotation relative to the saddle, the surface-hardened layer covering the ball head can isolate the ball head from the saddle, while the surface-hardened layer can contact the inner wall of the saddle. Therefore, during the ball head's rotation relative to the saddle, the surface-hardened layer rubs against the inner wall of the saddle. The high hardness of the surface-hardened layer makes it less susceptible to damage, ensuring smoother rotation of the ball head relative to the saddle.

[0051] In the embodiments of this application, please refer to Figure 5 , Figure 5 This is a flowchart illustrating a method for surface hardening a ball head according to an embodiment of this application. Here, surface hardening of the ball head to form a surface hardened layer on its surface may include: Step 2021: Carburize the ball head.

[0052] In this application, the carburizing treatment of the ball head can be carried out in a carburizing furnace. During the carburizing treatment of the ball head in the carburizing furnace, the carburizing furnace can be heated to change the temperature inside the furnace, and the atmosphere composition inside the carburizing furnace, such as the carbon content, can be changed to obtain the required heating carbon potential.

[0053] In one implementation, during the carburizing process of the ball head in the carburizing furnace, the heating temperature of the carburizing process can be between 910°C and 930°C, the heating carbon potential of the carburizing process can be between 1.13% and 1.17%, and the holding time of the carburizing process can be between 175 minutes and 185 minutes.

[0054] Step 2022: Quench the carburized ball head.

[0055] In this application, the quenching treatment of the ball head can be carried out in a quenching tank. Generally, a carburizing furnace has a quenching tank, which can be located below the carburizing furnace. In this way, after the ball head is carburized in the carburizing furnace, the carburized ball head can be directly transferred into the quenching tank located below the carburizing furnace for quenching treatment in the quenching tank.

[0056] Similarly, during the quenching process of the ball head in the quenching tank, the quenching tank can be heated to change the temperature inside the quenching tank, and the atmosphere ratio inside the quenching tank, such as the carbon content, can be changed to obtain the required heating carbon potential.

[0057] In one implementation, during the quenching process of the carburized ball head in the quenching tank, the heating temperature of the quenching process can be between 825°C and 845°C, the heating carbon potential of the quenching process can be between 0.84% ​​and 0.86%, the holding time of the quenching process can be between 55 minutes and 65 minutes, and the cooling temperature of the quenching process can be between 93°C and 97°C.

[0058] Step 2023: Temper the quenched ball head.

[0059] In this application, the tempering treatment of the ball head can be carried out in a tempering furnace. Here, the ball head that has been quenched in the quenching tank can be removed from the quenching tank and then placed into the tempering furnace.

[0060] Similarly, during the tempering process of the ball head in the tempering furnace, the tempering furnace can be heated to change the temperature inside the furnace.

[0061] In one implementation, during the tempering process of the ball head in the tempering furnace, the heating temperature of the tempering process can be between 170°C and 210°C, and the holding time of the tempering process can be greater than or equal to 120 minutes.

[0062] In this application, after sequentially performing carburizing, quenching, and tempering treatments on the ball head, a high-carbon hardened layer, i.e., a surface hardened layer, can be formed on the surface of the ball head. Compared to a ball head that has not undergone carburizing, quenching, and tempering treatments, the hardness and wear resistance of this high-carbon hardened layer are significantly improved, and the high-carbon hardened layer is less susceptible to damage. Furthermore, the internal structure of the ball head after carburizing, quenching, and tempering treatments retains its original toughness and strength, giving the ball head a comprehensive combination of wear resistance and impact resistance.

[0063] In the embodiments of this application, please refer to Figure 6 , Figure 6 This is a flowchart illustrating another method for surface hardening a ball head according to an embodiment of this application. Here, the surface hardening treatment of the ball head, forming a surface hardened layer on its surface, may further include: Step 2024: Perform the first hardness test on the ball head.

[0064] In this application, the step of performing a first hardness test on the ball head can be placed between the step of quenching the carburized ball head and the step of tempering the quenched ball head.

[0065] Thus, after quenching the ball head and before tempering it, a first hardness test is performed on the ball head. Once the hardness of the ball head is detected to be greater than or equal to the first hardness threshold, the tempering process is then performed.

[0066] Here, after the ball head is quenched, a first hardness test is performed. Only if the hardness of the ball head after the first hardness test is greater than or equal to the first hardness threshold is the ball head subjected to tempering. In this way, the first hardness test can screen out ball heads whose hardness after quenching is greater than or equal to the first hardness threshold. Only ball heads with a hardness greater than or equal to the first hardness threshold are subjected to tempering, while ball heads with a hardness less than the first hardness threshold are not subjected to tempering, thus reducing production costs.

[0067] In one implementation, the first hardness threshold can be 64.0 HRC. Furthermore, this application allows for the initial hardness test of the ball head using a hardness tester.

[0068] In the embodiments of this application, please refer to Figure 7 , Figure 7 This is a flowchart illustrating another method for surface hardening a ball head according to an embodiment of this application. Here, the surface hardening treatment of the ball head, forming a surface hardened layer on its surface, may further include: Step 2025: Perform the first cleaning treatment on the ball head.

[0069] In this application, the step of performing a first cleaning treatment on the ball head can be between the step of performing a carburizing treatment on the ball head and the step of performing a quenching treatment on the carburized ball head.

[0070] Thus, after quenching and before tempering, the ball head can undergo a first cleaning process. This first cleaning removes dust and debris from the ball head's surface, improving surface cleanliness and meeting the requirements of subsequent processing steps.

[0071] In this application, the initial cleaning process for the ball head may include adding a coolant. Adding a coolant during the initial cleaning process lowers the temperature of the quenched steel ball head, ensuring that its temperature meets the requirements for subsequent tempering.

[0072] It should be noted that after adding coolant during the first cleaning process of the ball head, the cleaning temperature for the first cleaning of the ball head can be between 60℃ and 80℃.

[0073] It should be noted that both the initial hardness test and the initial cleaning of the ball head can be performed after the quenching process and before the tempering process. Furthermore, the initial cleaning of the ball head can be performed after the initial hardness test.

[0074] In the embodiments of this application, please refer to Figure 8 , Figure 8 This is a flowchart illustrating another method for surface hardening a ball head according to an embodiment of this application. Here, the surface hardening treatment of the ball head, forming a surface hardened layer on its surface, may further include: Step 2026: Perform carbon homogenization treatment on the ball head.

[0075] In this application, the step of homogenizing the ball head can be performed before the step of carburizing the ball head. Thus, the ball head can be homogenized before being carburized.

[0076] Here, the carbonization of the ball head can also be carried out in a carburizing furnace.

[0077] In one implementation, during the homogenization treatment of the ball head in the carburizing furnace, the heating temperature of the homogenization treatment can be between 830°C and 870°C, the heating carbon potential of the carburizing treatment can be between 1.13% and 1.17%, and the holding time of the carburizing treatment can be between 9 minutes and 11 minutes.

[0078] In this way, after the ball head is homogenized in the carburizing furnace, there is no need to remove the ball head from the carburizing furnace. Then, the temperature in the carburizing furnace can be raised to between 910°C and 930°C, and then the ball head can be carburized.

[0079] Step 203: Perform a second hardness test on the ball head after surface hardening treatment.

[0080] In this embodiment of the application, after performing a second hardness test on the ball head after surface hardening treatment, if the detected surface hardness of the ball head is within a preset hardness range and the thickness of the surface hardening layer of the ball head is within a preset thickness range, the step of connecting the end of the ball head and the shaft can be performed.

[0081] Here, the preset hardness range of the ball head's surface hardness and the preset thickness range of the ball head's surface hardened layer can be considered as preset qualification conditions for the ball head after surface hardening treatment. After a second hardness test on the surface-hardened ball head, if the ball head's surface hardness and surface hardened layer thickness are within the preset range, the ball head meets the preset qualification conditions. A ball head that meets the preset qualification conditions can be connected to the end of the shaft.

[0082] In one implementation, the preset hardness range can be 600 HV to 780 HV, and the preset thickness range can be 0.3 mm to 0.6 mm.

[0083] It should be noted that the hardness of the ball head with a surface hardness within the preset hardness range can be greater than the hardness inside the ball head and can also be greater than the hardness of the shaft. Therefore, the ball head with a surface hardness within the preset hardness range can slide smoothly within the ball seat.

[0084] It should also be noted that this application can perform a second hardness test on the ball head using a hardness tester.

[0085] In this application, the ball head in the ball joint can be made of 20CrMnTi steel. 20CrMnTi is an alloy steel material conforming to GB / T3077-2015 standard. When the ball head is made of 20CrMnTi, after surface hardening treatment, the hardness of the surface hardened layer can be 698HV, 701HV, or 704HV, meeting the preset hardness range, and the thickness of the surface hardened layer can be 0.57 mm, meeting the preset thickness range.

[0086] It should be noted that when the ball head is made of 20CrMnTi, after surface hardening treatment, the surface microstructure of the ball head can contain martensite, retained austenite, and carbides. Furthermore, the martensite in the surface microstructure of the ball head is equivalent to level 4, the retained austenite to level 2, and the carbides to level 3, all satisfying the surface microstructure levels between 1 and 4.

[0087] Step 204: Provide the rod to be processed.

[0088] In this application, after the rod body is forged, it can be subjected to quenching and tempering treatment. The quenching and tempering treatment of the rod body can include: quenching treatment and high-temperature tempering treatment.

[0089] In one implementation, the quenching and tempering of the rod can be performed in a heating furnace. During the quenching and tempering process in the furnace, the furnace can be heated to change the temperature within the quenching tank. In another implementation, during the quenching process, the heating temperature can be between 830°C and 850°C, and the cooling temperature can be between 150°C and 180°C. During the high-temperature tempering process, the heating temperature can be between 500°C and 650°C.

[0090] In this way, after the forged rod is heat-treated, the internal structure of the rod is uniform, the residual stress can be eliminated, resulting in high overall strength of the rod. At the same time, the rod also has good plasticity and toughness, making it less prone to deformation and cracking.

[0091] In one implementation, after the shaft undergoes heat treatment, its stiffness can be tested. If the shaft's stiffness is detected to be between 32 HRC and 39 HRC, the shaft can be connected to the ball head. That is, if the shaft's stiffness is detected to be between 32 HRC and 39 HRC, the shaft meets the stiffness requirement and can be used to connect to the ball head.

[0092] In this application, the material of the shaft in the ball pin can be 40Cr steel. 40Cr is an alloy steel material conforming to the GB / T3077-2015 standard. When the shaft is made of 40Cr, after tempering, the hardness of the shaft can be between 35.5HRC, 36.6HRC, or 37.2HRC, meeting the hardness requirements.

[0093] It should be noted that when the rod body is made of 40Cr, after quenching and tempering, the surface microstructure of the rod body can have tempered sorbite + a small amount of ferrite. Furthermore, the tempered sorbite + small amount of ferrite in the surface microstructure of the rod body is equivalent to level 2, satisfying the surface microstructure levels between level 1 and 4.

[0094] It should also be noted that when the rod body is made of 40Cr, no decarburization occurs after the rod body undergoes quenching and tempering treatment, and the depth of complete decarburization of the rod body is less than or equal to 0.015 mm.

[0095] Step 205: Connect the surface-hardened ball head and the end of the shaft to obtain the ball pin.

[0096] Here, the ball head and shaft, which are manufactured separately, are fixed together to form the ball pin.

[0097] Please refer to the following in this application: Figure 9 , Figure 9 This is a flowchart illustrating a method for connecting the ball head and the end of the shaft according to an embodiment of this application. The connection process between the ball head and the end of the shaft may include: Step 2051: Weld the ends of the ball head and the shaft after surface hardening treatment.

[0098] In this application, the surface-hardened ball head and the end of the shaft are joined together by welding to achieve a fixed connection. Here, the end of the shaft is welded to the surface-hardened layer of the ball head. Furthermore, a butt welding process can be used to weld the end of the shaft to the surface-hardened layer of the ball head.

[0099] In one implementation, during the welding process of the surface-hardened ball head and rod ends, the welding current can be 105 amperes, the welding time can be 0.16 seconds, and the welding pressure can be 0.5 MPa. It should be noted that the welding current refers to the current flowing through the welding circuit, the welding time refers to the duration of a single pulse, and the welding pressure is the pressure applied by the electrode to the workpiece contact surface.

[0100] It should be noted that because the ball head undergoes carburizing after surface hardening, the carbon content of the surface hardened layer is relatively high. Therefore, during the welding process between the end of the club and the surface hardened layer of the ball head, martensite is more likely to form at the weld position. Martensite is brittle, which reduces the strength at the weld position between the end of the club and the ball head, making the club more prone to breakage from the ball head.

[0101] It should also be noted that before welding the ends of the ball head and shaft after surface hardening, the ball head and shaft can be transferred to the welding station and clamped within it. After being clamped in the welding station, the ends of the ball head and shaft can be aligned, and then welding can be performed on them.

[0102] Step 2052: After cooling at the welded position between the ball head and the end of the shaft, perform a tempering treatment on the welded position.

[0103] In this application, after the ends of the ball head and the shaft are welded together, the temperature at the weld position between the ends of the ball head and the shaft rises. Therefore, it is necessary to cool the weld position between the ends of the ball head and the shaft before performing a tempering treatment on the weld position.

[0104] Here, after cooling at the weld joint between the ball head and the end of the rod, and after tempering, the tempered martensite generated at the weld joint can transform into tempered troostite. Tempered troostite is less brittle than tempered martensite. Therefore, tempering the weld joint between the ball head and the end of the rod can reduce the brittleness at this weld joint and improve the connection strength between the ends of the ball head and the rod to meet strength requirements.

[0105] It should be noted that the strength requirement for the connection between the ball head and the end of the shaft is that the tensile force between the ball head and the shaft is greater than or equal to 50 kN.

[0106] Here, when the ball head is made of 20CrMnTi and the shaft is made of 40Cr, after welding the ends of the ball head and shaft that have undergone surface hardening treatment, and after tempering the welded area between the ends of the ball head and shaft, the tensile strength between the ball head and shaft can be 63KN, 67KN or 65KN, which meets the requirement that the tensile strength between the ball head and shaft is greater than or equal to 50KN.

[0107] In one implementation, tempering the welded area between the ends of the ball head and the shaft can include: applying electricity to the welded area between the ends of the ball head and the shaft to heat the welded area between the ends of the ball head and the shaft.

[0108] In one implementation, an electric current is applied to the welding position between the ends of the ball head and the shaft to heat the welding position. The welding current can be 94 amperes, the welding time can be 0.24 seconds, and the welding pressure can be 0.5 MPa.

[0109] In this application, after tempering the welded area between the ball head and the end of the shaft, the welded area can be cooled to return to room temperature. Furthermore, after cooling, the welded ball head and shaft can be subjected to flaw detection to ensure that the surface damage of the ball pins leaving the production line is within a predetermined range.

[0110] In summary, this application provides a method for manufacturing a ball joint, wherein the ball head and the shaft are manufactured separately. After obtaining the ball head to be processed, a surface hardening treatment can be performed on the ball head to form a surface hardening layer. The hardness of the surface hardening layer is greater than the hardness of the ball head's interior and greater than the hardness of the shaft. Thus, the surface hardening layer covers the ball head, and after the ball head is installed in the ball seat, the surface hardening layer can isolate the ball head from the ball seat, while the surface hardening layer contacts the inner wall of the ball seat. Therefore, during the rotation of the ball head relative to the ball seat within the ball seat, the surface hardening layer rubs against the inner wall of the ball seat. The high hardness of the surface hardening layer results in good wear resistance and makes it less prone to damage, ensuring smoother rotation of the ball head relative to the ball seat within the ball seat. Furthermore, the separate manufacturing of the ball head and the shaft ensures that the surface hardening process of the ball head does not affect the shaft, the strength of the shaft is not reduced, and the shaft is less prone to breakage.

[0111] This application also provides a ball pin, which is a ball pin prepared by the ball pin preparation method described in the above embodiments.

[0112] A ball pin may include a ball head and a shaft. The surface of the ball head in the ball pin has a surface-hardened layer that covers the ball head. The shaft in the ball pin can be connected to a ball having the surface-hardened layer.

[0113] In this application, the hardness of the surface-hardened layer is greater than the hardness of the ball's interior and greater than the hardness of the shaft. Thus, the surface-hardened layer covers the ball head, and after the ball head is installed in the saddle, the surface-hardened layer isolates the ball head from the saddle, while the surface-hardened layer contacts the inner wall of the saddle. Therefore, during the rotation of the ball head relative to the saddle, the surface-hardened layer rubs against the inner wall of the saddle. The higher hardness of the surface-hardened layer results in better wear resistance and reduces the likelihood of damage, ensuring smoother rotation of the ball head relative to the saddle. Furthermore, the ball head and shaft are manufactured separately, ensuring that the surface-hardening process on the ball head does not affect the shaft, maintaining its strength and reducing the likelihood of breakage.

[0114] This application also provides a vehicle, including: a suspension system and wheels, and a ball joint provided in any of the above embodiments, wherein the ball head of the ball joint is connected to the suspension system, and the rod of the ball joint is connected to the wheel.

[0115] Since the vehicle includes the ball pin provided in the above embodiments, it can also have similar effects, which will not be elaborated further here.

[0116] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0117] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0118] The above description is merely an embodiment of one implementation of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a ball pin, characterized in that, The method includes: Provide the ball head to be processed; The ball head is subjected to surface hardening treatment to form a surface hardening layer on the surface of the ball head; the surface hardening layer covers the ball head; Provide the rod to be processed; The ball head and the end of the rod body are connected after surface hardening treatment to obtain the ball pin; The surface hardening layer has a harder hardness than the interior hardness of the ball head and is also harder than the rod body.

2. The preparation method according to claim 1, characterized in that, The surface hardening treatment of the ball head includes: The ball head is subjected to carburizing treatment; The carburized ball head is then quenched. The quenched ball head is then subjected to tempering treatment.

3. The preparation method according to claim 2, characterized in that, The surface hardening treatment of the ball head further includes: After the ball head is quenched and before it is tempered, a first hardness test is performed on the ball head. After detecting that the hardness of the ball head is greater than or equal to the first hardness threshold, the ball head is subjected to tempering treatment.

4. The preparation method according to claim 2, characterized in that, The surface hardening treatment of the ball head further includes: After the ball head is quenched and before it is tempered, the ball head is subjected to a first cleaning process.

5. The preparation method according to claim 2, characterized in that, The carburizing treatment of the ball head also includes: Before carburizing the ball head, the ball head undergoes a homogenization treatment.

6. The preparation method according to any one of claims 1-5, characterized in that, The method further includes: The ball head, after surface hardening treatment, is subjected to a second hardness test. After detecting that the surface hardness of the ball head is within a preset hardness range and the thickness of the surface hardened layer of the ball head is within a preset thickness range, the step of connecting the ends of the ball head and the shaft is performed.

7. The preparation method according to claim 6, characterized in that, The preset hardness range is 600HV to 780HV, and the preset thickness range is 0.3 mm to 0.6 mm.

8. The preparation method according to any one of claims 1-5, characterized in that, The process of connecting the ends of the ball head and the rod body after surface hardening treatment includes: The ends of the ball head and the rod body are welded after surface hardening treatment; After the welded area between the ball head and the end of the rod has cooled, the welded area is subjected to tempering treatment.

9. The preparation method according to claim 8, characterized in that, Tempering the welded area includes: Electricity is applied to the welding position to heat it.

10. A ball pin, characterized in that, The ball pin is prepared using the preparation method described in any one of claims 1 to 9.

11. The ball pin according to claim 10, characterized in that, Includes: a ball head and a shaft; the surface of the ball head has a surface-hardened layer covering the ball head; the end of the shaft is connected to the ball head having the surface-hardened layer; The surface hardening layer has a harder hardness than the interior hardness of the ball head and is also harder than the rod body.

12. A vehicle, characterized in that, It includes: a suspension system and a wheel, and a ball joint as described in claim 10 or 11, wherein the ball head in the ball joint is connected to the suspension system, and the rod in the ball joint is connected to the wheel.

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