Precision machining method for thin-wall long bolt

Abstract

The invention discloses a precision machining method for a thin-wall long bolt. The precision machining method comprises the following steps that S1, the outer surface and the end face of a part are roughly machined; s2, deep hole drilling is conducted on the part subjected to rough machining in the step S1 through three tools; s3, residual stress of the part is eliminated through a stabilizing treatment process; s4, turning and deviation correction are conducted on the part with the runout exceeding 0.05 mm in the step S2; s5, the outer circle of the part is subjected to finish turning; s6, the outer circle rod part of the part is subjected to grinding treatment; s7, shot blasting is conducted on the part through a sectional type shot blasting method; s8, performing inspection; according to the machining method provided by the invention, a rod part turning and grinding scheme is optimized, and the size qualification rate of 0.015 mm jumping of a precise shot blasting surface with a blind hole bottom (stress concentration point) structure reaches 100% through a sectional type shot blasting method.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical processing, and in particular to a precision processing method for thin-walled long bolts. Background Art

[0002] At present, in aero-engines, the materials of thin-walled long bolts are mostly nickel-based high-temperature alloys. The inner holes of such parts often have spherical deep blind holes with large aspect ratio and small diameter. The aspect ratio of the blind hole is as high as 27:1, and the runout requirement of the deep blind hole based on the outer cylindrical reference surface is no more than 0.12mm. The precision requirement of the diameter size of the outer surface of the part is only 0.01mm, and shot peening is required to ensure the stability and reliability of the connection. After shot peening, the precision outer cylindrical surface has high requirements for diameter and runout value, especially the runout of the precision outer cylindrical surface based on the reference surface is mostly required to be no more than 0.015mm. After shot peening, in order to ensure the performance of the part, the part must not be corrected. This is extremely difficult to control the deformation of the hollow thin-walled long bolts. Therefore, a mature and stable thin-walled long bolt processing method is urgently needed to meet the requirements of mass production of thin-walled long bolts with high quality.

[0003] The patent with the prior art application number CN201910534796.1 discloses a deep hole drilling method for tiny thin-walled parts, including the following steps: Step SS1: Use a centering drill to center the product, set the drilling depth and reserve a processing allowance for the next drill bit; Step SS2: Use a medium drill bit to drill the product, control the drilling depth and reserve a processing allowance for the next drill bit; Step SS3: Use a long drill bit to drill the product, control the drilling depth and reserve a single-side allowance. The present invention aims at the technical problems that the existing centering drill processing has a drill line diameter ratio that is too long, and the hole is very easy to be drilled eccentrically, broken and fractured after the drill bit vibrates. The present invention proposes a drill processing process for thin-walled parts with a tiny length-to-line diameter ratio; the process of the invention optimizes the process from aspects such as tool selection, rotation speed, feed, control of cutting amount and cutting reserve, and method of feeding drill chips. The disadvantage of the patent is that it is difficult to control the outer circle of the part to reach the processing standard based on the reference surface after the drilling is completed. Summary of the invention

[0004] The present invention mainly aims at the problem that the runout qualified rate of the precision shot peening surface of thin-walled blind hole structure or thin-walled long bolt in the prior art is difficult to control, and proposes a precision machining method for thin-walled long bolts, so that the parts are stabilized after deep hole drilling to eliminate residual stress, and no correction process is used throughout the whole process, and the rod turning and grinding schemes are optimized. Finally, by adopting a segmented shot peening method, the precision shot peening surface with a runout of 0.015mm in the structure with a blind hole bottom (stress concentration point) is achieved. The size pass rate reaches 100%.

[0005] In view of the above technical problems, the technical solutions of the present invention are as follows:

[0006] A precision machining method for thin-walled long bolts, comprising the following steps:

[0007] S1. Process the blank and rough-process the outer surface and end face of the part;

[0008] S2, deep hole drilling: on a horizontal machining center, deep hole drilling is performed on the parts that have been rough-machined in step S1, the rod of the parts is clamped with soft claws, a guide drill is first used to machine a guide hole, a long drill is then used to machine a bottom hole, and finally a formed ball-end milling cutter is used to complete the leveling of the bottom of the deep hole;

[0009] S3, stabilization treatment: after the blind hole processing of the parts is completed, the parts are subjected to stabilization treatment process to eliminate residual stress, and the parts are vertically hung in a vacuum tempering aging furnace;

[0010] S4, lathe deflection repair: deflection repair is performed on the parts whose runout exceeds 0.05 mm in step S2;

[0011] S5, finishing the outer circle: finishing the outer circle of the parts;

[0012] S6, outer cylindrical part grinding: grinding the outer cylindrical part of the part;

[0013] S7, shot peening: according to the outer circle of the root of the blind hole deformed by shot peening, the conventional shot peening path is divided, and the suspended part of the part is shot peened first by the segmented shot peening method, and the starting point of the segmented shot peening is the outer circle of the root of the blind hole, and then quickly moves from the middle weak point to the large end of the part;

[0014] S8. Inspect the parts after shot peening.

[0015] Furthermore, in step S2, under the condition of high-pressure internal cooling, the rotation speed of the guide drill bit is set to 2500r / min, and a certain feed rate is used to drill an initial hole of about 3-7mm deep and stop, and the feed rate is increased to drill a guide hole of about 10-13mm with a depth of at least 3 times the diameter, and the tool is quickly retracted; the guide drill bit, long drill bit and forming ball head milling cutter are all provided with an internal cooling zone coating.

[0016] Furthermore, in step S2, under the condition of high-pressure internal cooling, the rotation speed of the long drill bit is consistent with the rotation speed of the guide drill bit, and the guide hole is first drilled counterclockwise at a certain feed rate. After the long drill bit enters the part about 10-13mm, the feed rate is increased to process the blind hole of the remaining depth, and the tool is quickly retracted after the blind hole processing is completed.

[0017] Furthermore, in step S2, the overhang depth of the forming ball head milling cutter exceeds 100 mm. During the leveling process of the forming ball head milling cutter, the rotation speed of the forming ball head milling cutter is set to 700 r / min, and a low feed rate is used to process the spherical bottom of the inner hole by pecking drilling, and the processing allowance is not more than 1.5 mm.

[0018] Furthermore, the vacuum tempering aging furnace is heated to (540°C-560°C)±5°C at a certain rate, kept warm for a period of time, a certain amount of argon is introduced and a fan is turned on for cooling, and when the temperature drops below 100°C, it is taken out of the furnace and air-cooled.

[0019] Furthermore, in step S4, a hole runout measuring tool is used to measure the actual runout value L of the outer cylindrical rod portion of the part relative to the inner hole reference of the part and mark the runout high point position (angle α), the uppermost jaw of the four-jaw chuck is aligned with the runout high point position marked on the part, the small end of the part is clamped, and the top point is supported against the hole mouth position of the part, and the actual runout value L and runout position of the part are matched with the value and position (angle α) measured by the hole runout measuring tool, and the runout between the outer cylindrical turning rod portion and the inner hole of the part is controlled within 0.05 mm.

[0020] Furthermore, after the turning of the rod is completed, a three-jaw chuck is used to clamp the rod, and the runout at the clamping point is not greater than 0.01 mm.

[0021] Furthermore, in the step S5, the outer circle of the large end of the part is rough-turned and fine-turned respectively, and the runout of the outer circle rod portion relative to the center holes at both ends of the part is controlled by turning to be no more than 0.03 mm.

[0022] Furthermore, in step S6, the part is ground with a grinding wheel, and the grinding is performed in three steps. First, the middle rod of the part is processed, and then the grinding wheel R is repaired; during rough processing, the single-side grinding amount is about 0.015-0.02mm, and a single-side margin of 0.01-0.02mm is left for fine processing; during fine processing, the single-side grinding amount is about 0.003-0.007mm, and before each step of fine grinding of the part, a grinding wheel dressing work is added, and the integrity of the diamond pen is checked before dressing.

[0023] Furthermore, in the step S7, during the segmented shot peening process, clamps are provided at both ends of the part.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention is aimed at thin-walled long bolts with a spherical deep blind hole structure with a large aspect ratio and a small diameter. By designing three coated and internally cooled tools with a diameter size of Ф3.65, namely a guide drill, a long drill and a formed ball-end milling cutter, the guide hole drilled by the guide drill, the bottom hole processed by the long drill, and the leveling work of the bottom R of the deep hole completed by the formed ball-end milling cutter; it can avoid using a dedicated CNC gun drilling machine and expensive forming gun drilling tools to process parts, and the present invention is more economical; the original CNC gun drilling tool needs to be sharpened every time 2-3 parts are processed, while each tool can stably process at least 20 parts with the existing tool, and the processing efficiency is improved by more than 60%.

[0026] 2. After the deep hole drilling is completed, the present invention performs a stabilization treatment to eliminate residual stress on the parts. The correction process is not used throughout the process, the rod turning scheme and the grinding scheme are optimized, and finally, by adopting a segmented shot peening method, a precision shot peening surface with a blind hole bottom (stress concentration point) structure with a dimensional pass rate of 0.015mm is achieved, reaching 100%; after the thin-walled long bolt completes the processing of a large aspect ratio and small diameter spherical deep blind hole, the residual stress of the part is large. The residual stress of the part is eliminated by adopting a stabilization treatment process. In the segmented shot peening process, the deformation of the part before and after shot peening is strictly controlled to ensure that the final precision shot peening surface runout size reaches 0.015mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the structure of a thin-walled long bolt of the present invention;

[0028] Figure 2 This is a schematic diagram of the processing of a thin-walled long bolt guide drill bit according to the present invention;

[0029] Figure 3 It is a schematic diagram of the deep hole drilling process of a thin-walled long bolt according to the present invention;

[0030] Figure 4 It is a schematic diagram of the turning and trimming of a thin-walled long bolt according to the present invention;

[0031] Figure 5 This is a schematic diagram of the thin-walled long bolt connection bottom R of the present invention;

[0032] Figure 6 It is a schematic diagram of the segmented shot peening method of the thin-walled long bolt of the present invention;

[0033] Figure 7 Schematic diagram of conventional shot peening for thin-walled long bolts.

[0034] In the schematic diagram, 1. rod; 2. large end; 3. small end; 4. top hole; 5. fixture; 6. shot peening area; SR. bottom hole; ①, ②, ③, ④, ⑤ represent the shot peening process respectively. DETAILED DESCRIPTION

[0035] In order to clearly illustrate the technical features of the application scheme of the present invention, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited to the specific embodiments disclosed below.

[0037] Example 1

[0038] like Figure 1 As shown, a precision machining method for thin-walled long bolts comprises the following steps:

[0039] S1. Process the blank and rough-process the outer surface and end face of the part;

[0040] S2, deep hole drilling: On a horizontal machining center, deep hole drilling is performed on the part that has been rough-machined in step S1, the rod 1 of the part is clamped with soft claws, a guide hole is first machined with a guide drill, a bottom hole is then machined with a long drill, and finally a forming ball-end milling cutter is used to complete the leveling of the bottom of the deep hole;

[0041] S3, stabilization treatment: after the blind hole processing of the parts is completed, the parts are subjected to stabilization treatment process to eliminate residual stress, and the parts are vertically hung in a vacuum tempering aging furnace;

[0042] S4, lathe deflection repair: deflection repair is performed on the parts whose runout exceeds 0.05 mm in step S2;

[0043] S5, finishing the outer circle: finishing the outer circle of the parts;

[0044] S6, grinding of outer cylindrical portion: grinding the outer cylindrical portion 1 of the part;

[0045] S7, shot peening: according to the outer circle of the root of the blind hole deformed by shot peening, the conventional shot peening path is divided, and the suspended part of the part is shot peened by the segmented shot peening method, and the starting point of the segmented shot peening is the outer circle of the root of the blind hole, and then quickly moves from the middle weak point to the large end of the part 2; Figure 1 As shown, the large end 2 in this embodiment refers to the end with a larger outer diameter of the part, and the small end 3 refers to the end with a smaller outer diameter;

[0046] S8. Inspect the parts after shot peening.

[0047] like Figure 1 As shown, the runout of a deep blind hole based on an outer cylindrical reference surface is required to be no greater than 0.12 mm, and the runout of a precision outer cylindrical surface based on a reference surface is mostly required to be no greater than 0.015 mm. The method of the present application can meet these requirements.

[0048] In this embodiment, in step S2, the diameters of the three cutting tools are all Φ3.65. Figure 2 As shown, soft jaws are used to clamp the rod 1 of the part, the clamping width of the soft jaws is 30mm, and a coated and internally cooled alloy guide drill is used to process a 13mm long guide hole. The total length of the tool is about 50mm, and the blade length is 15mm. The guide drill processing is specifically that the guide drill with a rotation speed of 2500r / min drills a 5mm deep initial hole at a feed rate of F0.05mm / r and stays for 1 circle under the premise of high pressure inner hole, and then drills a guide hole of about 13mm with a depth of at least 3 times the diameter at a feed rate of F0.08mm / r, and then quickly withdraws the tool from the workpiece.

[0049] like Figure 3 As shown, in this embodiment, a long drill is used to process a deep hole, and a soft claw is used to clamp the rod 1 of the part. The clamping width of the soft claw is 30mm. A coated alloy deep hole drill with internal cooling is used to process a 90.6mm long bottom hole. The total length of the tool is about 140mm, and the blade length is 100mm. The long drill with a rotation speed of 2500r / min is used to drill a 11mm deep guide hole counterclockwise at a feed rate of F0.5mm / r under the premise of a high-pressure inner hole. Since the tool sizes of the long drill and the guide drill are both Ф3.65 and the depth is less than 13mm, the long drill When entering the unprocessed part counterclockwise, the guide hole of the part will not be scratched. After the long drill enters the part 11mm, it will be processed clockwise at a speed of 2500r / min and a feed rate of F0.08mm / r to machine the remaining 80.1mm deep blind hole, and then quickly withdraw the tool from the workpiece. Considering that the inner hole is a deep blind hole, in order to ensure the chip removal effect of the part, the guide drill, long drill and forming ball head milling cutter are all equipped with internal cooling belt coating. This processing technology can replace the traditional forming gun drill tool on a dedicated deep hole gun drilling machine, and the tool price and processing efficiency are significantly improved.

[0050] like Figure 5 As shown, soft jaws are used to clamp the part rod 1, the soft jaw clamping width is 30mm, and a coated alloy ball head milling cutter with internal cooling is used to connect the bottom R of the blind hole. The total length of the tool is about 140mm and the blade length is 16mm. Considering that the milling force of the ball head milling cutter with a large aspect ratio is small and the rigidity is poor, only a margin of no more than 1.5mm is left for the spherical milling cutter to level it. A forming ball head milling cutter with a cantilever depth of more than 100mm is used. The tool speed is set to 700r / min, and a low feed rate of 5mm / min is used to complete the leveling of the spherical bottom of the inner hole by pecking drilling.

[0051] After the thin-walled long bolts have completed the processing of the spherical deep blind hole with a large aspect ratio and small diameter, the residual stress of the parts is relatively large. A stable treatment process is required to eliminate the residual stress of the parts, because the shot peening process will release a certain amount of residual stress. This is one of the keys to ensure that the final precision shot peening surface runout size reaches 0.015mm. The parts are vertically suspended into the vacuum tempering aging furnace to avoid bending and deformation of the parts. The vacuum working pressure in the furnace is about 133.3×10-1Pa~133.3×10-5Pa.

[0052] Example 2

[0053] like Figure 4 As shown, in this embodiment, in order to ensure that the runout of the final inner hole based on the outer circle reference surface is not greater than 0.12mm, for the parts with runout exceeding 0.05mm in step S2, a hole runout measuring tool or a measuring device is used to measure the actual runout value L of the outer cylindrical rod portion 1 of the part relative to the inner hole reference of the part, and the runout high point position (angle α) is marked, and then a four-jaw chuck is used on an ordinary lathe to align the top jaw of the four-jaw chuck with the runout high point position marked on the part, clamp the small end 3 of the part, and the top point is against the hole mouth position processed in step S2, and the part runout measured value L, runout position and the value and position (angle α) measured by the hole runout measuring tool or the measuring device are matched, and then turning is performed, so that the runout of the outer cylindrical turning rod portion 1 and the inner hole of the part can be controlled within 0.05mm. This is because when deep hole drilling, the runout at the inlet position is generally better, and the runout at the outlet position is worse, which can be controlled according to the eccentricity of the bottom position of the hole.

[0054] After completing the turning of the above-mentioned rod 1, it is only necessary to clamp the rod 1 normally with a three-jaw chuck, align the clamping position so that the runout is no more than 0.01mm, level the outer circle of the clamping position in the above figure, and complete the processing of the center hole 4 at the small end 3 of the part for subsequent precision turning of the rod 1.

[0055] like Figure 4 As shown, the rod 1 of the part is clamped, and two 35°R0.4 tools are used to rough and fine turn the outer circle of the part 2 ( Figure 4The right end has not been processed outer circle), and then turn around to clamp the part and turn the outer circle of the large end 2 that has been turned to hold the top hole 4 of the part. When turning the remaining most of the outer circle rod 1 of the part, it is necessary to ensure that the outer circle of the turned rod 1 does not exceed 0.03mm from the top holes 4 at both ends of the part. The runout must be directly guaranteed by turning, and the correction process cannot be used to avoid causing large residual stress in the part. Based on this, considering the part size requirements, a 35°R0.4 external cylindrical cutter is used for rough machining to avoid part interference, the cutting depth is 0.3mm, the rotation speed is 400r / min, and the feed is 0.06mm / r; a 35°R0.2 external cylindrical cutter is used for fine machining, the cutting depth is 0.2mm, the rotation speed is 500r / min, and the feed is 0.06mm / r. The tool cutting force was reduced by changing the original finishing 35°R0.4 tool to a 35°R0.2 blade. In addition, the cutting speed of the process was reduced from 600r / min to 500r / min, and the feed was reduced from 0.08mm / r to 0.06mm / r.

[0056] like Figure 5 As shown, in this embodiment, the outer cylindrical rod portion 1 of the part is ground, and the specific process is: the part is ground using a conventional single crystal corundum grinding wheel P500×50×203SA60KV, considering that the part material has a high hardness and the dimensional tolerance is only 0.01mm, and the runout of the center holes 4 at both ends is required to be no more than 0.005mm. Therefore, the long bolts are ground in three steps. First, the middle rod 1 of the part is processed, then the grinding wheel R is repaired, the large end 2 rod and R of the part are processed, and finally the small end 3 rod of the part is processed. When grinding, considering the high hardness of the part, the single-side grinding amount of the rough machining of the part is 0.015-0.02mm, and a single-side margin of 0.01-0.02mm is left for fine machining; the single-side grinding amount during fine machining is 0.005mm. Before each step of fine grinding of the part, the grinding wheel dressing work needs to be added, and the integrity of the diamond pen is checked before dressing to ensure the sharpness of the grinding wheel during fine grinding. Finally, the grinding wheel linear speed is maintained at 30-35m / s, the workpiece rotation speed is 60-70r / min, and the grinding process requires that the qualification rate of all dimensions can reach 100%.

[0057] Example 3

[0058] like Figure 1As shown, a precision machining method for thin-walled long bolts includes the following steps: wherein, S7, in order to ensure that the outer circles at both ends of the rod portion 1 of the part do not run out more than 0.015mm based on the middle outer circle reference surface after shot peening, the conventional shot peening path is divided according to the outer circle of the root of the blind hole deformed by shot peening, and the suspended part of the part is shot peened first by segmented shot peening, so that the rigidity of the outer circle of the root of the blind hole and the entire suspended part of the part is increased, and the starting point of shot peening is the outer circle of the root of the blind hole, and then it moves quickly from the middle weak point to the large end 2 of the part.

[0059] like Figure 7 As shown, to ensure Figure 1 After shot peening, the outer circles at both ends of the middle part rod 1 are strictly controlled based on the requirement that the runout of the middle outer circle reference surface is no more than 0.015mm. The conventional shot peening method is to fix the large end of the part on the shot peening equipment through a clamp. The shot peening process parameters are shot peening intensity: F10-12A, shot specification: ZG30, coverage: greater than or equal to 100%, air source pressure: 1×105Pa, shot flow: 8Kg / min, spray distance: 120mm, turntable speed: 10r / min, nozzle diameter: Ф10mm, number of nozzles: 1, nozzle angle: 30°, nozzle moving speed: 150mm / min. See the detailed shot peening path for details. Figure 7 As shown in the figure, the nozzle moves from the large end of the part to the small end 3 of the part, and then moves from the small end 3 to the large end, and the shot peening of the part is completed. This shot peening route is suitable for parts with uniform wall thickness of the rod 1 or all solid structural parts. It is not suitable for parts whose shot peening area includes both solid structures and thin-walled structures and whose shot peening outer circle runout requirement is not greater than 0.015mm, because there is stress concentration at the bottom of the blind hole of the part, and the outer circle surface here is easy to exceed the tolerance during shot peening, and the qualified rate is difficult to reach 100%.

[0060] like Figure 6 As shown in the figure, a segmented shot peening method is used. The core of this shot peening method is to use the key part of shot peening deformation (the outer circle of the blind hole root) to divide the conventional shot peening path, and first peen the suspended part of the part, and the starting point is from the root of the blind hole to increase the rigidity of the outer circle of the blind hole root and the entire suspended part of the part. Figure 6 As shown in the figure, the shot peening route is to first process from point B to point C, then from point C to point B; then G00 quickly moves from point B to point A, from point A to point B, and finally from point B to point A. In this process, the parts are all hollow thin-walled outer surfaces, and the entire shot peening process is stable and controllable.

[0061] Obviously, the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A precision machining method for thin-walled long bolts, characterized in that: The following steps are involved: S1. Process the blank and rough-process the outer surface and end face of the part; S2, deep hole drilling: on a horizontal machining center, deep hole drilling is performed on the parts that have been rough-machined in step S1, the rod of the parts is clamped with soft claws, a guide drill is first used to machine a guide hole, a long drill is then used to machine a bottom hole, and finally a formed ball-end milling cutter is used to complete the leveling of the bottom of the deep hole; S3, stabilization treatment: after the blind hole processing of the parts is completed, the parts are subjected to stabilization treatment process to eliminate residual stress, and the parts are vertically hung in a vacuum tempering aging furnace; S4, lathe deflection repair: deflection repair is performed on the parts whose runout exceeds 0.05 mm in step S2; S5, finishing the outer circle: finishing the outer circle of the parts; S6, outer cylindrical part grinding: grinding the outer cylindrical part of the part; S7, shot peening: according to the outer circle of the root of the blind hole deformed by shot peening, the conventional shot peening path is divided, and the suspended part of the part is shot peened first by the segmented shot peening method, and the starting point of the segmented shot peening is the outer circle of the root of the blind hole, and then quickly moves from the middle weak point to the large end of the part; S8. Inspect the parts after shot peening.

2. A precision machining method for thin-walled long bolts according to claim 1, characterized in that: In step S2, under the condition of high-pressure internal cooling, the rotation speed of the guide drill is set to 2500r / min, and a certain feed rate is used to drill an initial hole about 3-7mm deep and stop, and the feed rate is increased to drill a guide hole of about 10-13mm with a depth of at least 3 times the diameter, and the tool is quickly retracted; the guide drill, long drill and forming ball head milling cutter are all provided with an internal cooling zone coating.

3. A precision machining method for thin-walled long bolts according to claim 1, characterized in that: In step S2, under the condition of high-pressure internal cooling, the rotation speed of the long drill bit is consistent with the rotation speed of the guide drill bit, and the guide hole is first drilled counterclockwise at a certain feed rate. After the long drill bit enters the part about 10-13mm, the feed rate is increased to process the blind hole of the remaining depth, and the tool is quickly retracted after the blind hole processing is completed.

4. A precision machining method for thin-walled long bolts according to claim 1, characterized in that: In step S2, the overhang depth of the forming ball head milling cutter exceeds 100 mm. During the leveling process of the forming ball head milling cutter, the rotation speed of the forming ball head milling cutter is set to 700 r / min, and a low feed rate is used to process the spherical bottom of the inner hole by pecking drilling, and the processing allowance is not more than 1.5 mm.

5. The precision machining method for thin-walled long bolts according to claim 1, characterized in that: In step S3, the vacuum tempering aging furnace is heated to (540°C-560°C)±5°C at a certain rate, kept warm for a period of time, a certain amount of argon is introduced and a fan is turned on for cooling, and when the temperature drops below 100°C, the furnace is taken out of the furnace for air cooling.

6. A precision machining method for thin-walled long bolts according to claim 1, characterized in that: In step S4, a hole runout measuring tool is used to measure the actual runout value L of the outer cylindrical rod portion of the part relative to the inner hole reference of the part and mark the runout high point position (angle α), the uppermost jaw of the four-jaw chuck is aligned with the runout high point position marked on the part, the small end of the part is clamped, and the top point is supported against the hole mouth position of the part, and the actual runout value L and the runout position of the part are matched with the values ​​and positions (angle α) measured by the hole runout measuring tool, and the runout of the outer cylindrical turning rod portion and the inner hole of the part is controlled within 0.05mm.

7. A precision machining method for thin-walled long bolts according to claim 6, characterized in that: After the turning of the rod is completed, the rod is clamped with a three-jaw chuck, and the runout at the clamping point is not greater than 0.01mm.

8. The precision machining method for thin-walled long bolts according to claim 1, characterized in that: In step S5, the outer circle of the large end of the part is rough-turned and fine-turned respectively, and the runout of the outer circle rod portion relative to the center holes at both ends of the part is controlled by turning to be no more than 0.03 mm.

9. A precision machining method for thin-walled long bolts according to claim 1, characterized in that: In step S6, the part is ground with a grinding wheel, and the grinding is performed in three steps. First, the middle rod of the part is processed, and then the grinding wheel R is repaired; the single-side grinding amount during rough processing is about 0.015-0.02mm, and a single-side margin of 0.01-0.02mm is left for fine processing; the single-side grinding amount during fine processing is about 0.003-0.007mm, and before each step of fine grinding of the part, a grinding wheel dressing work is added, and the integrity of the diamond pen is checked before dressing.

10. A precision machining method for thin-walled long bolts according to claim 1, characterized in that: In the step S7, during the segmented shot peening process, clamps are provided at both ends of the part.

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