A method of machining a steering inner tube

Abstract

The present application relates to a kind of processing methods of steering inner tube.It includes the following processes:(1) selecting raw material, (2) raw material surface treatment, (3) rotary swaging processing, (4) extruding outer spline, (5) turning cutting and chamfering, (6) extruding internal thread, (7) cleaning, rust prevention, boxing.The rotary swaging process two in the present application reserves material in front end, ensures that the material after thread bottom in rotary swaging process three is enough, and under the support of light plug rod, it is ensured that A-B runout value is low.In rotary swaging process three, light plug rod is used as support, prevent the collapse of conical surface material, keep conical surface forming better.Moreover, the bearing and the junction of installation switch area, can prevent the material in bearing area from not being deformed, meet the requirement of bearing area outer diameter size.

Description

Technical Field

[0001] This invention relates to the field of automotive steering column technology, specifically a method for processing steering inner tubes. Background Technology

[0002] The steering column and intermediate shaft assembly is the connecting component installed between the steering wheel and the steering gear. Its main functions are to control the vehicle's direction of travel, transmit torque, and absorb energy during a collision. Based on their working principles, steering columns can be divided into mechanical columns and electronically adjustable columns. Functionally, they allow for vertical and horizontal adjustment, collectively known as four-way adjustment, to meet the driver's comfort requirements.

[0003] The structure of the steering inner tube generally consists of several parts from front to back: external spline area 1, internal thread area 2, conical surface 3, combination switch mounting area 4, bearing area 5, and internal spline area 6. Figure 1 As shown. In the existing technology, the specific processing method of the inner tube is as follows: Step 1, rotary forging the inner spline 6 area; Step 2, reducing the diameter of the remaining raw material at the other end so that the outer diameter of the inner tube is the same as the outer diameter of the inner spline area; Step 3, rotary forging the bottom diameter of the outer spline and the conical surface 3 in one step; Step 4, rotary forging the combination switch mounting area 4; Step 5, cold extruding the outer spline 1; Step 6, extruding the internal thread 2 with a tap.

[0004] The above processing method has the following defects: 1. Insufficient material for the inner thread bottom diameter: In actual process development, it was found that after the inner spline is formed, the bearing area and the outer spline area are reduced in diameter to make the outer diameters of the inner spline area, bearing area and outer spline area the same. This results in insufficient wall thickness in the bottom diameter part of the rotary forged outer spline. When rotary forging the bottom diameter of the outer spline, even if the size requirement of the outer spline bottom diameter is met, the inner thread bottom diameter is larger than the required size, and there is insufficient material for the thread bottom diameter. Normally, this problem is solved by increasing the wall thickness of the pipe. However, if the wall thickness is increased too much, it will lead to large material deformation during the inner spline forming, causing certain difficulties, such as large equipment vibration, increased tooling wear, which is not conducive to mass production and goes against the development of lightweight automotive parts in modern times. 2. Large runout at the bottom diameter of the outer spline: Because there is no smooth stopper rod inside the pipe as support when rotary forging the bottom diameter of the outer spline, the runout of the bottom diameter of the outer spline is large. 3. Poor cone surface forming: In the existing processing method, the bottom diameter of the external spline and the cone surface 3 are formed by rotary forging in one step, and then the installation area 4 of the combination switch is formed by rotary forging. Since there is no light plug rod to support it inside the tube, the cone surface material is prone to collapse, resulting in poor cone surface forming. Summary of the Invention

[0005] The purpose of this invention is to provide a machining method for a steering inner tube, which has high machining accuracy, good tapered surface forming, and can meet the material requirements for the thread root diameter.

[0006] The technical solution of the present invention:

[0007] A method for processing a steering inner tube includes the following steps:

[0008] (1) Select raw materials, (2) Surface treatment of raw materials, (3) Rotary forging, (4) Extrusion of external splines, (5) Turning, cutting and chamfering, (6) Extrusion of internal threads, (7) Cleaning, rust prevention and packing.

[0009] Specific processing methods:

[0010] (1) Select raw materials; select precision seamless cold-drawn steel pipes with appropriate outer diameter, wall thickness and length, and the steel pipes have a certain degree of ductility;

[0011] (2) Material surface treatment: Phosphating treatment of seamless steel pipe surface can effectively reduce the extrusion pressure on the working surface of mold and improve the service life of clamping fixture;

[0012] (3) Rotary forging:

[0013] a. Rotary forging and cold extrusion of internal splines: Internal splines are forged on one side of a steel pipe using a rotary forging machine. A suitable rotary forging outer diameter die and mandrel are selected. During the processing, the die extrudes the outer surface of the pipe, and the mandrel supports the pipe material inside. During the processing, the material flows radially and axially, and the internal spline is formed after rotary forging.

[0014] b: Lathe length preservation process: Using a CNC lathe, retain the internal spline section and the total length of the inner tube as required;

[0015] c: Rotary forging diameter reduction: The steel pipe is rotary forged to reduce the diameter of the side without extruded internal splines using a rotary forging machine. The outer diameter die and smooth stopper rod used in the rotary forging cold extrusion internal spline process are used for the diameter reduction rotary forging. The rotary forging is carried out in two stages. The first stage reduces the diameter of the end of the steel pipe without extruded internal splines. After forming, the outer diameter is larger than the outer diameter of the internal spline. The second stage reduces the diameter of the remaining part of the steel pipe after the first stage. After forming, the outer diameter is the same as the outer diameter of the internal spline. The length of the end of the steel pipe after the first rotary forging is 6% of the length of the internal spline part.

[0016] d: Rotary forging of the outer spline bottom diameter and conical surface. The outer spline bottom diameter and conical surface are rotary forged using a rotary forging machine. The rotary forging process is carried out using a rotary forging die for the outer spline bottom diameter and a smooth plug bar from the rotary forging diameter reduction step. The rotary forging is performed in three stages. In the first stage of rotary forging, the outer spline bottom diameter and conical surface are rotary forged. The end of the smooth plug bar is positioned at the rear end of the conical surface after forming to prevent material collapse during rotary forging. In the second stage of rotary forging, the smooth plug bar remains in place to prevent deformation of the conical surface. The first third of the combined switch installation area is rotary forged. In the third stage of rotary forging, the smooth plug bar moves backward to the junction of the bearing area and the combined switch installation area to rotary forge the last two-thirds of the combined switch installation area.

[0017] (4) Extruding external splines: Using support rods and mold frames, install them on the worktable of a four-column hydraulic press to perform cold extrusion of external splines. The extruded splines have no missing teeth or material accumulation.

[0018] (5) Turning, cutting and chamfering; holding the middle area of ​​the inner tube, cutting, chamfering and cutting to retain the total length of the finished product;

[0019] (6) Extruding internal threads; the middle area of ​​the inner tube is clamped by a pneumatic chuck, and the threads are cold-extruded by an extrusion tap, without thread damage or breakage.

[0020] (7) Cleaning, rust prevention, and packing; inspect before packing to prevent defective products from being released.

[0021] The beneficial effects of this invention are:

[0022] 1. The forging die for the spline forming process in this application is shared with the diameter reduction die for the second forging process; the smooth plug rod is shared between the second and third forging processes. In the development of the forging process, this indirectly reduces the fabrication of tooling fixtures for the inner tube and lowers processing costs. The area for installing the combination switch is processed in the third forging process, reducing one manual loading process.

[0023] 2. In the second rotary forging process of this application, the outer diameter of the reduced-diameter section of the inner tube front end (the end without the internal spline) is larger than the outer diameter of the internal spline area, and the tube wall is thicker. This ensures that the size of the internal thread hole meets the requirements during the rotary forging of the outer spline bottom diameter, and that there is sufficient material for the internal thread bottom diameter. Furthermore, the reduced-diameter step in the second rotary forging process, supported by a smooth stopper rod, uses a concave rotary forging method to ensure a low AB runout value. In the third rotary forging process, a smooth stopper rod is used as a support to prevent the conical material from collapsing, maintaining a good conical surface shape. Moreover, during the rotary forging of the combined switch installation area, the process involves two rotary forging operations, with the smooth stopper rod position adjusted simultaneously. After the adjustment, the front end of the smooth stopper rod is positioned at the junction of the bearing area and the combined switch installation area, preventing material deformation in the bearing area and meeting the outer diameter requirements of the bearing area. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is a cross-sectional view of the inner tube of this application.

[0026] Figure 2 This is a schematic diagram of the overall structure of the inner tube of the steering system in this application.

[0027] Figure 3A schematic diagram of the steel pipe structure for machining the inner steering tube.

[0028] Figure 4 This is a schematic diagram of the workpiece structure after the first rotary forging process.

[0029] Figure 5 This is a schematic diagram of the workpiece structure after the long process.

[0030] Figure 6 This is a schematic diagram of the workpiece structure after the second rotary forging process.

[0031] Figure 7 This is a schematic diagram of the workpiece structure after the third step of the rotary forging process.

[0032] Figure label:

[0033] 1. External spline; 2. Internal thread; 3. Tapered surface; 4. Combination switch mounting area; 5. Bearing; 6. Internal spline; 7. Steel pipe; 8. External spline base diameter. Detailed Implementation

[0034] To address the problems existing in the background technology, the processing method for the inner tube of the steering mechanism of this application has been invented. This method has high processing accuracy, good tapered surface forming, and can simultaneously meet the dimensional requirements of both the thread root diameter and the external spline root diameter, with sufficient material for the thread root diameter. Moreover, while meeting the requirements of internal spline forming and lightweighting, thin-walled raw material tubes are selected as much as possible.

[0035] The present application will now be described in detail with reference to the accompanying drawings:

[0036] A method for processing a steering inner tube includes the following steps:

[0037] (1) Select raw materials, (2) Surface treatment of raw materials, (3) Rotary forging, (4) Extrusion of external splines, (5) Turning, cutting and chamfering, (6) Extrusion of internal threads, (7) Cleaning, rust prevention and packing.

[0038] Specific processing methods:

[0039] (1) As Figure 3 As shown, select raw materials; choose precision seamless cold-drawn steel pipes with suitable outer diameter, wall thickness and length, and with a certain degree of ductility.

[0040] (2) Surface treatment of raw materials: Phosphating treatment of seamless steel pipe surface can effectively reduce the extrusion pressure on the working surface of mold and improve the service life of clamping fixture.

[0041] (3) Rotary forging:

[0042] a. such as Figure 4As shown, rotary forging cold extrusion of internal splines (rotary forging process one): using a rotary forging machine to rotary forge internal splines on one side of a steel pipe, selecting a suitable rotary forging outer diameter die and mandrel, during the processing, the die extrudes the outer surface of the pipe, and the mandrel supports the pipe material inside. During the processing, the material undergoes radial and axial flow, and the internal spline is formed after rotary forging.

[0043] b: such as Figure 5 As shown, the lathe length preservation process involves using a CNC lathe to preserve the length of the internal spline section and the total inner tube as required.

[0044] c: such as Figure 6 As shown, rotary forging diameter reduction (rotary forging process two): The portion of the steel pipe without extruded internal splines is rotary forged and reduced in diameter using a rotary forging machine. The outer diameter die and smooth plug rod used in the rotary forging cold extrusion internal spline process are used for diameter reduction rotary forging. The rotary forging is performed in two stages. The first stage is to reduce the diameter of the end of the steel pipe without extruded internal splines (i.e., the corresponding external spline area). After forming, the outer diameter is larger than the outer diameter of the internal spline. The second stage is to reduce the diameter of the remaining portion of the steel pipe after the first stage (corresponding to the bearing area and the combined switch installation area). After forming, the outer diameter is the same as the outer diameter of the internal spline. The length of the end of the steel pipe after the first rotary forging is 6% of the length of the internal spline portion.

[0045] d: such as Figure 7 As shown, the bottom diameter and conical surface of the external spline are forged using a rotary forging machine. The external spline bottom diameter and conical surface are forged using a rotary forging die and a smooth plug bar from the rotary forging diameter reduction step. The rotary forging is performed in three stages. In the first stage, the external spline bottom diameter and conical surface are forged using a rotary forging machine. The end of the smooth plug bar is positioned at the rear end of the conical surface after forming to prevent material collapse during rotary forging. In the second stage, the smooth plug bar remains in place to prevent deformation of the conical surface. The first third of the combined switch installation area is forged using a rotary forging die. In the third stage, the smooth plug bar moves backward to the junction of the bearing area and the combined switch installation area to prevent material deformation in the bearing area. The last two-thirds of the combined switch installation area is forged using a rotary forging die. The third stage is the final rotary forging step.

[0046] (4) Extruding external splines: Using support rods and mold frames, install them on the worktable of a four-column hydraulic press to perform cold extrusion of external splines. The extruded splines have no missing teeth or material accumulation.

[0047] (5) Turning, cutting and chamfering; holding the middle area of ​​the inner tube, cutting, chamfering and cutting to retain the total length of the finished product.

[0048] (6) Extruding internal threads: The inner tube is clamped in the middle area by a pneumatic chuck, and the threads are formed by cold extrusion by an extrusion tap, without any thread damage or breakage.

[0049] (7) Cleaning, rust prevention, and packing; inspect before packing to prevent defective products from being released. Specific implementation examples:

[0051] This embodiment, to better fit existing steering wheels, ensures that the M18 thread interface, external spline parameters, and bearing area diameter remain unchanged. Steering inner tube design requirements: 18-tooth internal spline parameters, M18 internal thread, bearing area diameter. This structure offers superior stiffness compared to other structural parameters of the inner tube, thereby improving product performance and enhancing vehicle driving safety. The internal spline 6 has 18 teeth and a minor diameter... Da Jia Pitch circle diameter Thread 2 is M18X1.5; external spline 1 has 86 teeth, a tooth cogging angle of 30°, and a pitch circle... Tooth tip circle Tooth root round

[0052] The inner and outer surfaces of the steering inner tube cannot be machined during the forming process, otherwise the metallographic structure of the material will be damaged. Except for cutting length and chamfering, the entire tube is cold extruded. During the processing, the tube material will undergo plastic deformation and harden during the extrusion process, exhibiting a certain degree of fibrous flow, which will increase the hardness and strength of the product, thereby obtaining greater rigidity to achieve the transmission of greater torque.

[0053] If existing technical methods are used, the following problems exist:

[0054] 1. It cannot simultaneously meet the requirements for the external spline root diameter and the internal thread root diameter, and does not meet the conditions for thread extrusion forming.

[0055] 2. Based on A and B, the runout of the bottom diameter of the external spline is >0.2mm; after the inner tube is forged, the runout of the bottom diameter of the external spline is measured with a dial indicator and is between 0.4 and 1.2mm, which does not meet the requirement of ≤0.2mm in the drawing.

[0056] 3. After the bottom diameter of the external spline is forged, the cone surface is poorly formed.

[0057] Specific processing methods:

[0058] (1) Selection of raw materials: Select precision seamless cold-drawn steel pipes with an outer diameter of 34.6, an inner diameter of 27.8, a wall thickness of 3.4, and a length of ≥240, and with a certain degree of ductility.

[0059] (1) Surface treatment of raw materials: Before rotary forging and cold extrusion, the raw materials are prepared by phosphate treatment of the seamless steel pipe surface, which can effectively reduce the extrusion pressure on the working surface of the die and improve the service life of the clamping fixture.

[0060] (2) Rotary forging:

[0061] a. Rotary Forging and Cold Extrusion of Internal Splines (Rotary Forging Process 1): Using an HA-40 rotary forging machine, internal splines are forged on one side of the steel pipe. A rotary forging die and an 18-tooth mandrel are selected. During processing, the die extrudes the outer surface of the pipe, while the 18-tooth mandrel provides internal support. The material undergoes radial and axial flow during processing. After rotary forging, an 18-tooth internal spline is formed, with a length ≥240 mm and an outer diameter...

[0062] b: Lathe length maintenance process: Using a CNC lathe, the internal spline section is maintained at 238mm in length, and the total length is 320±0.5mm.

[0063] c: Rotary forging diameter reduction (rotary forging process two): Utilizing an HA-40 rotary forging machine for rotary forging diameter reduction, borrowing the outer diameter die from the cold extrusion of the internal spline in the rotary forging process. The light stopper rod undergoes a diameter-reduction rotary forging process. After adjusting the program parameters, the forging is performed in two stages with mold closing. The first stage reduces the diameter of the end of the steel pipe that is not extruded from the internal spline. After forming, the outer diameter is larger than the outer diameter of the internal spline. The second reduction is performed on the remaining portion of the steel pipe after the first reduction. The outer diameter of the formed pipe is the same as the outer diameter of the internal spline. The length of the end of the steel pipe in the first rotary forging is 14-16 cm;

[0064] d: Rotary forging of external spline bottom diameter and tapered surface (rotary forging process three): Using an HA-40 rotary forging machine, the external spline bottom diameter and tapered surface are rotary forged, using the rotary forging external spline bottom diameter die and the rotary forging diameter reduction step. The light stopper rod undergoes rotary forging, which is performed in three stages of die-fitting rotary forging. The first stage involves rotary forging the outer spline bottom diameter. The light plug rod's head is positioned at the rear end of the cone surface after forming to prevent material collapse during rotary forging. During the second die-closing rotary forging, the light plug rod remains stationary to prevent cone surface deformation. The dimensions of the rotary forging combination switch mounting area are also specified. The front length is 10 mm. During the third die-forging process, the smooth stopper bar is moved backward 30 mm to the junction of the bearing area and the combined switch mounting area to prevent material deformation in the bearing area. The dimensions of the combined switch mounting area are as follows: [Dimensions of the combined switch mounting area are missing from the original text]. 20 mm long, formed by third-order rotary forging.

[0065] (4) External spline forming: Using support rods and mold frame, install on the worktable of four-column hydraulic press to perform cold extrusion of external splines. The extruded splines have no missing teeth or material accumulation, which meets the requirements.

[0066] (5) Turning, cutting and chamfering; holding the middle area of ​​the inner tube, cutting, chamfering and cutting to retain the total length of the finished product.

[0067] (6) Thread forming: The inner tube is clamped in the middle area by a pneumatic chuck, and the thread is formed by cold extrusion by a tap.

[0068] (7) Cleaning, rust prevention, and packing. Inspection should be carried out before packing to prevent defective products from being shipped out.

[0069] The rotary forging die for the 18-tooth internal spline forming process is shared with the diameter reduction die for the second rotary forging process; the smooth plug rod is shared between the second and third rotary forging processes. This indirectly reduces the fabrication of rotary forging inner tube tooling fixtures and lowers processing costs during the rotary forging development process. (Installation area for combination switches) The dimensions are processed in the third stage, reducing one manual material loading process.

[0070] Front end of rotary forging process 2 Material reserves are made to ensure sufficient material for the thread bottom diameter after the third rotary forging process. Furthermore, with the support of the smooth stopper rod, the concave rotary forging diameter reduction ensures an AB runout value ≤ 0.2. In the third rotary forging process, the smooth stopper rod is used as a support to prevent the conical surface material from collapsing, maintaining good conical surface forming; and... Size and At the dimensional joints, it is possible to prevent deformation of the material in the bearing area, thus satisfying the bearing area requirements. Require.

[0071] Note: All length units in this application are millimeters.

[0072] In this application, the inner spline portion of the steering inner tube is the rear end, and the outer spline portion is the front end.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention, and are not intended to limit them. Although the embodiments of the present invention have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the embodiments of the present invention.

Claims

1. A method for processing a steering inner tube, characterized in that: The following processes are included: (1) Select raw materials, (2) Surface treatment of raw materials, (3) Rotary forging, (4) Extrusion of external splines, (5) Turning, cutting and chamfering, (6) Extrusion of internal threads, (7) Cleaning, rust prevention and packing. Specific processing methods: (1) Select raw materials; select precision seamless cold-drawn steel pipes with appropriate outer diameter, wall thickness and length, and the steel pipes have a certain degree of ductility; (2) Material surface treatment: Phosphating treatment of seamless steel pipe surface can effectively reduce the extrusion pressure on the working surface of mold and improve the service life of clamping fixture; (3) Rotary forging: a. Rotary forging and cold extrusion of internal splines: Internal splines are forged on one side of a steel pipe using a rotary forging machine. A suitable rotary forging outer diameter die and mandrel are selected. During the processing, the die extrudes the outer surface of the pipe, and the mandrel supports the pipe material inside. During the processing, the material flows radially and axially, and the internal spline is formed after rotary forging. b: Lathe length preservation process: Using a CNC lathe, retain the internal spline section and the total length of the inner tube as required; c: Rotary forging diameter reduction: The diameter reduction of the steel pipe is carried out on the side of the steel pipe that is not extruded with internal splines using a rotary forging machine. The outer diameter die and smooth stopper rod of the rotary forging cold extrusion internal spline process are used for the diameter reduction rotary forging. The rotary forging is carried out in two stages. The first stage is to reduce the diameter of the end of the steel pipe that is not extruded with internal splines. After forming, the outer diameter is larger than the outer diameter of the internal spline. The second stage is to reduce the diameter of the remaining part of the steel pipe after the first stage. After forming, the outer diameter is the same as the outer diameter of the internal spline. The length of the end of the steel pipe after the first rotary forging is 6% of the length of the internal spline part. d: Rotary forging of the outer spline bottom diameter and conical surface. The outer spline bottom diameter and conical surface are rotary forged using a rotary forging machine. The rotary forging process is carried out using a rotary forging die for the outer spline bottom diameter and a smooth plug bar from the rotary forging diameter reduction step. The rotary forging is performed in three stages. In the first stage of rotary forging, the outer spline bottom diameter and conical surface are rotary forged. The end of the smooth plug bar is positioned at the rear end of the conical surface after forming to prevent material collapse during rotary forging. In the second stage of rotary forging, the smooth plug bar remains in place to prevent deformation of the conical surface. The first third of the combined switch installation area is rotary forged. In the third stage of rotary forging, the smooth plug bar moves backward to the junction of the bearing area and the combined switch installation area to rotary forge the last two-thirds of the combined switch installation area. (4) Extruding external splines: Using support rods and mold frames, install them on the worktable of a four-column hydraulic press to perform cold extrusion of external splines. The extruded splines have no missing teeth or material accumulation. (5) Turning, cutting and chamfering; holding the middle area of ​​the inner tube, cutting, chamfering and cutting to retain the total length of the finished product; (6) Extruding internal threads; the middle area of ​​the inner tube is clamped by a pneumatic chuck, and the threads are cold-extruded by an extrusion tap, without thread damage or breakage. (7) Cleaning, rust prevention, and packing; inspect before packing to prevent defective products from being released.

2. The processing method of a steering inner tube according to claim 1, characterized in that: Specific processing methods: The steering inner tube has an 18-tooth internal spline, an M18 internal thread, and a bearing area diameter. The number of external spline teeth is 86. (1) Selection of raw materials: Select precision seamless cold-drawn steel pipes with an outer diameter of 34.6, an inner diameter of 27.8, a wall thickness of 3.4, and a length of ≥240, and the steel pipes have a certain degree of ductility; (2) Surface treatment of raw materials: Before rotary forging and cold extrusion, the raw materials are prepared by phosphate treatment of the seamless steel pipe surface, which can effectively reduce the extrusion pressure on the working surface of the die and improve the service life of the clamping fixture. (3) Rotary forging: a. Rotary forging and cold extrusion of internal splines: Using an HA-40 rotary forging machine, internal splines are forged on one side of the steel pipe. A rotary forging die and an 18-tooth mandrel are selected. During processing, the die extrudes the outer surface of the pipe, while the 18-tooth mandrel provides support inside the pipe. During processing, the material undergoes radial and axial flow. After rotary forging, an 18-tooth internal spline is formed, with a length ≥240 mm and an outer diameter... b: Lathe length maintenance process: Using a CNC lathe, the internal spline section is maintained at 238mm in length, and the total length is 320±0.5mm. c: Rotary forging diameter reduction: Utilizing an HA-40 rotary forging machine for rotary forging diameter reduction, and taking advantage of the outer diameter die used in the cold extrusion of the internal spline during rotary forging. The light stopper rod undergoes a diameter-reduction rotary forging process. After adjusting the program parameters, the forging is performed in two stages with mold closing. The first stage reduces the diameter of the end of the steel pipe that is not extruded from the internal spline. After forming, the outer diameter is larger than the outer diameter of the internal spline. The second reduction is performed on the remaining portion of the steel pipe after the first reduction. The outer diameter of the formed pipe is the same as the outer diameter of the internal spline. The length of the end of the steel pipe in the first rotary forging is 14-16 cm; d: Rotary forging of external spline bottom diameter and tapered surface: The external spline bottom diameter and tapered surface are forged using an HA-40 rotary forging machine, employing a rotary forging external spline bottom diameter die and the rotary forging diameter reduction step. The light stopper rod undergoes rotary forging, which is performed in three stages of die-fitting rotary forging. The first stage involves rotary forging the outer spline bottom diameter. The light plug rod's head is positioned at the rear end of the cone surface after forming to prevent material collapse during rotary forging. During the second die-closing rotary forging, the light plug rod remains stationary to prevent cone surface deformation. The dimensions of the rotary forging combination switch mounting area are also specified. The front length is 10mm. During the third die-forging process, the smooth plug is moved backward to the junction of the bearing area and the combined switch mounting area to prevent material deformation in the bearing area. The dimensions of the combined switch mounting area are as follows: [Dimensions of the combined switch mounting area are missing]. 20 (units unspecified) (4) External spline forming: Using support rods and mold frame, the external spline is cold extruded on the worktable of a four-column hydraulic press. The extruded spline has no missing teeth or material accumulation, which meets the requirements. (5) Turning, cutting and chamfering; holding the middle area of ​​the inner tube, cutting, chamfering and cutting to retain the total length of the finished product; (6) Thread forming; The inner tube is clamped in the middle area by a pneumatic chuck, and the thread is formed by cold extrusion by a tap. (7) Cleaning, rust prevention and packing: Inspection is carried out before packing to prevent unqualified products from flowing out.

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