A method for manufacturing a stress-durable Inconel 718 high-temperature alloy precision rod bolt

Abstract

The present application belongs to the technical field of bolt fastener machining, and particularly relates to a manufacturing method of stress-durability Inconel 718 high-temperature alloy precision rod bolt. The manufacturing method comprises the following steps: heat upsetting forming on the head of the part; solid solution treatment on the part; numerical control rough machining on the part, with the diameter size allowance of the light rod, and the top hole step of the tail part not being removed; cold roll forming on the R angle under the head of the part; thread rolling on the part; aging treatment on the part; and numerical control finishing forming on the part. The manufacturing method effectively avoids the size out-of-tolerance problem of the stress-durability Inconel 718 high-temperature alloy precision rod bolt after the aging treatment of the precision rod, with the precision of the precision rod being less than or equal to 0.009 mm, meeting the precision requirement of the precision rod, and ensuring the performance of the product.

Description

Technical Field

[0001] This invention belongs to the field of bolt fastener machining technology, and specifically relates to a method for manufacturing a stress-delay type Inconel 718 high-temperature alloy precision rod bolt. Background Technology

[0002] Stress-resistant Inconel 718 high-temperature alloy D-head precision rod bolts offer excellent connection performance, including high temperature resistance, corrosion resistance, vibration resistance, and space-saving installation, and are widely used in the field of aircraft engines.

[0003] See Figure 1 Because relevant standards specify the dimensions of its smooth rod ( Figure 1 For the medium-precision rod section 1), the precision is ≤0.009mm, and since this bolt is a stress-delay type, its solution treatment needs to be performed before finishing, and the aging treatment needs to be performed after rolling (R). Figure 1 2) Medium rolling R machining part and thread rolling ( Figure 1 After the thread rolling part 3), the main processing flow is: "Hot upsetting head → solution treatment → precision turning → R rolling → thread rolling → aging treatment → surface treatment → finished product inspection".

[0004] The problem with the above processing method is that Inconel 718 material undergoes a solid-state phase transition after aging treatment, which affects the diameter of the aging rod. Figure 1 The precision rod portion 1) is 0.009mm~0.010mm smaller than before aging. This reduction exceeds its tolerance range and does not meet the precision requirements of the rod, making it impossible to effectively guarantee this dimension. How to ensure the precision rod dimension without compromising the bolt rolling radius and thread strength, and thus guaranteeing product performance, is an urgent problem to be solved.

[0005] Chinese invention patent CN102941447B discloses a bolt manufacturing process. The process involves hot upsetting, solution treatment, rough machining, vacuum aging, finish machining and thread rolling, surface treatment, and inspection. The vacuum failure treatment is moved to between rough and finish machining, and a solution treatment is added between hot upsetting and rough machining. This ensures a uniform distribution of internal metal flow lines in the semi-finished bolt workpiece between finish machining and thread rolling, preventing the breakage of internal metal flow lines in the finished bolt workpiece after finish machining and thread rolling. This guarantees the hardness and strength of the finished bolt workpiece and solves the problem of internal metal flow line interruption in the processing of twelve-corner flange bolts in existing technologies. However, this patented bolt is a fatigue-resistant type, meaning that the finish machining, thread rolling, and radius rolling processes are performed after the final heat treatment, and there is no issue of dimensional reduction after aging treatment. Therefore, it is incomparable to the processing of stress-endurance bolts. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for manufacturing stress-delay Inconel 718 high-temperature alloy precision rod bolts. This method effectively avoids the dimensional deviation problem that occurs after the precision rod undergoes aging treatment, ensuring a precision rod accuracy of ≤0.009mm, meeting the precision rod accuracy requirements, and guaranteeing product performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for manufacturing a stress-endurance type Inconel 718 high-temperature alloy precision rod bolt includes the following steps: S1. Hot forging is performed on the head of the part; S2. Perform solution treatment on the parts; S3. Perform CNC machining on the part, leaving allowance for the dimensions of the smooth rod, while retaining the step of the center hole at the tail without removing it; S4. Perform cold rolling on the lower radius of the part head; S5. Perform thread rolling on the parts; S6. Perform aging treatment on the parts; S7. Perform CNC machining on the parts to achieve precision forming.

[0008] Preferably, the heating current for hot upsetting the head of the part in step S1 is 910~930A, the heating time is 2~4s, the holding current is 910~930A, and the holding time is 2~4s.

[0009] Preferably, the hot upsetting process uses a 20~40kW high-frequency heater, with an inner diameter of φ15~16mm for the heating coil and 4~6 turns of the heating coil.

[0010] Preferably, the solution treatment of the part in step S2 includes: The heat treatment temperature is 785~815℃, held for 60~65min, then heated to 940~970℃, held for 90-99min, and cooled with argon gas.

[0011] Preferably, the allowance for the diameter of the optical rod in step S3 is 0.16~0.24mm.

[0012] Preferably, step S4, which involves cold rolling the lower radius of the part head, includes: Cold rolling is performed on an arc within a 90° range calculated from the point of tangency between the lower fillet and the head support surface. Use rollers with R0.28~R0.32, rolling pressure of 1150~1250N, rolling time of 1000~2000ms, spindle speed of 400~500r / min, and feed speed of 60~80r / min.

[0013] Preferably, the deformation A value of the transition area between adjacent regions on both sides of the R-angle rod or head is 0.06~0.10mm; the pressing depth B value of the roller applied in the direction perpendicular to the R-angle surface is 0.06~0.10mm.

[0014] Preferably, the aging treatment of the parts in step S6 includes: The heat treatment temperature is 710~726℃, held for 480~510min, then furnace cooled to 613~629℃ at a cooling rate of 48~64℃ / h, held for 480~510min, and then cooled with argon gas.

[0015] Preferably, step S7, which involves CNC turning to finish the part, includes: The part is machined using a collet and a tail center hole to machine a precision rod. At the same time, the tail center hole is removed. The bottom radius of the head is not machined with a radius of R0.6~R0.8. The precision rod accuracy is ≤0.009mm.

[0016] The positive and beneficial effects of this invention are as follows: 1. Fatigue-resistant bolts are characterized by their ability to resist fatigue fracture caused by alternating stress. Therefore, it is necessary to ensure the high strength and high toughness of the product. The processing technology usually involves finishing, thread rolling, and radius rolling after the final heat treatment (aging treatment) to enhance the strength of the thread root and the radius corner under the head, thereby improving fatigue life. Since the finishing, thread rolling, and radius rolling processes of fatigue-resistant bolts are carried out after the final heat treatment (aging treatment), there is no problem of dimensional reduction after aging treatment. This invention pertains to stress-endurance bolts, characterized by high creep resistance and relaxation resistance. It emphasizes uniform stress distribution to avoid localized stress concentration that could lead to creep fracture. The typical manufacturing process is "hot upsetting the head → solution treatment → precision turning → radius rolling → thread rolling → aging treatment → surface treatment → finished product inspection." Radius rolling and thread rolling are performed first, followed by aging heat treatment to reduce surface stress concentration. However, this method has a problem: because Inconel 718 material undergoes a solid-state phase transformation after aging, the diameter of the aged bolt decreases by 0.009mm to 0.010mm compared to before aging. This reduction exceeds the tolerance range and does not meet the precision requirements of the bolt, making it impossible to effectively guarantee the dimensional accuracy.

[0017] This invention, when processing stress-endurance Inconel 718 high-temperature alloy precision rod bolts, firstly involves hot upsetting the head of the part to ensure that the metallographic structure of the head does not overheat or burn, and that the grain flow lines remain normal. Next, the part undergoes solution treatment to improve the material's plasticity and toughness, preparing it for subsequent CNC lathe roughing. The smooth rod is then rough-machined using a CNC lathe; the dimensions of the smooth rod do not need to be precisely machined, leaving allowance for machining after aging treatment. The lower radius (R-angle) of the head is then cold-rolled; the large deformation during rolling provides allowance for machining after aging treatment. Finally, the part undergoes thread rolling, followed by aging treatment to eliminate residual stress and stabilize the material's microstructure and dimensions. The part is then precision-machined using a CNC lathe to ensure the precision requirements of the rod while preventing damage to the grain flow lines at the cold-rolled R-angle by the CNC lathe. This invention divides the precision turning process of existing technologies into two steps: CNC roughing and CNC finishing. Solution treatment is performed before roughing, and finishing is performed after aging. A allowance is left during the roughing of the polished rod to prevent dimensional deviations after aging. The allowance for the polished rod diameter is 0.16~0.24mm. Simultaneously, the deformation A value at the transition area between adjacent regions on both sides of the R-angle rod or head is 0.06~0.10mm, and the indentation depth B applied by the roller in the direction perpendicular to the R-angle surface is 0.06~0.10mm. mm, compared to the maximum standard requirement of 0.05mm, the rolling deformation is increased during the R-rolling process to ensure that the grain flow lines at the R-corner will not be damaged during machining after aging. After rough machining, R-rolling, and thread rolling, aging treatment is performed. After aging treatment, the precision rod is then precision machined. This effectively avoids the dimensional deviation problem that occurs in stress-endurance type Inconel 718 high-temperature alloy precision rod bolts after the precision rod has undergone aging treatment. The precision rod accuracy is ≤0.009mm, which meets the precision rod accuracy requirements and ensures product performance. Attached Figure Description

[0018] Figure 1 This is a structural schematic diagram of a D-type head precision rod bolt; Figure 2 This is a schematic diagram of the CNC lathe roughing of the guide rod according to the present invention; Figure 3 This is a schematic diagram of the bolt structure for cold rolling of the lower R-angle of the head according to the present invention; Figure 4 This is a schematic diagram of the bolt precision-machined by a CNC lathe according to the present invention; Figure 5 This is a partial structural schematic diagram of the bolt precision-machined by a CNC lathe according to the present invention; In the diagram: 1 is the precision rod section, 2 is the R-rolling section, 3 is the thread rolling section, 4 is the rough-machined smooth rod section, 5 is the rough-machined center hole step, 6 is the precision rod section, and 7 is the R-angle section under the head. Detailed Implementation

[0019] The present invention will be further described below with reference to some specific embodiments.

[0020] Example 1 A method for manufacturing a stress-delay type Inconel 718 high-temperature alloy D-head precision shank bolt includes the following steps: S1. Hot forging is performed on the head of the part; A 30kW high-frequency heater is used, with a heating coil inner diameter of φ15mm and 4 turns of the heating coil; the heating current is 920A, the heating time is 3s, the heat preservation current is 920A, and the heat preservation time is 3s, to ensure that the metallographic structure of the product head will not overheat or burn, and that the grain flow lines are normal. S2. Perform solution treatment on the parts; The heat treatment temperature is 800℃, held for 65 minutes, then heated to 954℃, held for 90 minutes, and cooled with argon gas to improve the plasticity and toughness of the material and prepare it for subsequent CNC lathe rough machining. S3. Perform CNC machining on the parts; See Figure 2 bare rod ( Figure 2 For the rough-machined section 4), a dimensional allowance of 0.20mm is provided for subsequent machining after aging treatment. A step for the center hole is also retained at the tail end. Figure 2 5) The step of the center hole in the medium-rough machining is not removed by turning, so that the part can be machined by turning after aging treatment; S4. Perform cold rolling on the lower radius of the part head; Cold rolling is performed on an arc within a 90° range calculated from the point of tangency between the lower fillet and the head support surface. Use an R0.3 roller, a rolling force of 1200N, a rolling time of 1000ms, a spindle speed of 500r / min, and a feed speed of 70r / min. join Figure 3 The deformation A value of the transition area between adjacent areas on both sides of the R-angle rod or head is 0.08mm; the pressing depth B value of the roller applied in the direction perpendicular to the R-angle surface is 0.08mm. The large deformation during rolling is to strengthen the R-angle under the head and to allow for machining after subsequent aging treatment. S5. Perform thread rolling on the parts; Install the support tool on the machine tool base, adjust the position and support height of the support tool to ensure that the workpiece and the center of the thread rolling wheel are in the correct relative position, align the thread line, and adjust the feed of the thread rolling wheel to extrude the thread. S6. Perform vacuum aging treatment on the parts; Vacuum degree ≤1.33×10 -2Pa, vacuum heat treatment temperature is 718℃, hold for 500min, furnace cool to 621℃ at a cooling rate of 56℃ / h, hold for 500min, argon cooling, the purpose of which is to eliminate residual stress inside the product, stabilize the material structure and size, and at the same time achieve the standard performance requirements. S7. The parts are precision machined and shaped using CNC turning; See Figure 4 and Figure 5 A D-type collet is used to connect with the three-jaw chuck on the left side of the CNC lathe. The D-type collet mates with the head of the D-type head precision rod bolt. The center pin is tightened with the center hole at the tail of the D-type head precision rod to machine the precision rod. At the same time, the center hole at the tail is removed to ensure the precision rod ( Figure 4 The dimensions of the precision rod section 6 (machined by a precision machine), and the lower radius (R angle) of the head. Figure 4 The lower R-angle section 7 of the precision machining head should be avoided by R0.6, and the precision rod ( Figure 4 The precision of the precision rod part 6) is ≤0.009mm, while ensuring that the grain flow lines at the R-angle cold rolling are not damaged by the CNC lathe.

[0021] Example 2 A method for manufacturing a stress-delay type Inconel 718 high-temperature alloy D-head precision shank bolt includes the following steps: S1. Hot forging is performed on the head of the part; A 30kW high-frequency heater is used, with a heating coil inner diameter of φ15mm and 4 turns of the heating coil; the heating current is 920A, the heating time is 3s, the heat preservation current is 920A, and the heat preservation time is 3s, to ensure that the metallographic structure of the product head will not overheat or burn, and that the grain flow lines are normal. S2. Perform solution treatment on the parts; The heat treatment temperature is 810℃, held for 60 minutes, then heated to 945℃, held for 90 minutes, and cooled with argon gas to improve the plasticity and toughness of the material and prepare it for subsequent CNC lathe roughing. S3. Perform CNC machining on the parts; See Figure 2 bare rod ( Figure 2 For the rough-machined section 4), a dimensional allowance of 0.20mm is provided for subsequent machining after aging treatment. A step for the center hole is also retained at the tail end. Figure 2 5) The step of the center hole in the medium-rough machining is not removed by turning, so that the part can be machined by turning after aging treatment; S4. Perform cold rolling on the lower radius of the part head; Cold rolling is performed on an arc within a 90° range calculated from the point of tangency between the lower fillet and the head support surface. Use an R0.3 roller, a rolling force of 1200N, a rolling time of 1000ms, a spindle speed of 500r / min, and a feed speed of 70r / min. join Figure 3 The deformation A value of the transition area between adjacent areas on both sides of the R-angle rod or head is 0.1mm; the pressing depth B value of the roller applied in the direction perpendicular to the R-angle surface is 0.1mm. The large deformation during rolling is to strengthen the R-angle under the head and to allow for machining after subsequent aging treatment. S5. Perform thread rolling on the parts; Install the support tool on the machine tool base, adjust the position and support height of the support tool to ensure that the workpiece and the center of the thread rolling wheel are in the correct relative position, align the thread line, and adjust the feed of the thread rolling wheel to extrude the thread. S6. Perform vacuum aging treatment on the parts; Vacuum degree ≤1.33×10 -2 Pa, vacuum heat treatment temperature is 720℃, hold for 510 min, furnace cool to 624℃ at a cooling rate of 60℃ / h, hold for 490 min, argon cooling, the purpose of which is to eliminate residual stress inside the product, stabilize the material structure and size, and at the same time meet the standard performance requirements. S7. The parts are precision machined and shaped using CNC turning; See Figure 4 and Figure 5 A D-type collet is used to connect with the three-jaw chuck on the left side of the CNC lathe. The D-type collet mates with the head of the D-type head precision rod bolt. The center pin is tightened with the center hole at the tail of the D-type head precision rod to machine the precision rod. At the same time, the center hole at the tail is removed to ensure the precision rod ( Figure 4 The dimensions of the precision rod section 6 (machined by a precision machine), and the lower radius (R angle) of the head. Figure 4 The lower R-angle section 7 of the precision machining head should be avoided by R0.6, and the precision rod ( Figure 4 The precision of the precision rod part 6) is ≤0.009mm, while ensuring that the grain flow lines at the R-angle cold rolling are not damaged by the CNC lathe.

[0022] Example 3 A method for manufacturing a stress-delay type Inconel 718 high-temperature alloy D-head precision shank bolt includes the following steps: S1. Hot forging is performed on the head of the part; A 30kW high-frequency heater is used, with a heating coil inner diameter of φ15mm and 4 turns of the heating coil; the heating current is 920A, the heating time is 4s, the heat preservation current is 920A, and the heat preservation time is 4s, to ensure that the metallographic structure of the product head will not overheat or burn, and that the grain flow lines are normal. S2. Perform solution treatment on the parts; The heat treatment temperature is 790℃, held for 65 minutes, then heated to 960℃, held for 99 minutes, and cooled with argon gas to improve the plasticity and toughness of the material and prepare it for subsequent CNC lathe rough machining. S3. Perform CNC machining on the parts; See Figure 2 bare rod ( Figure 2 For the rough-machined section 4), a dimensional allowance of 0.16mm is provided for subsequent machining after aging treatment. A step for the center hole is also retained at the tail end. Figure 2 5) The step of the center hole in the medium-rough machining is not removed by turning, so that the part can be machined by turning after aging treatment; S4. Perform cold rolling on the lower radius of the part head; Cold rolling is performed on an arc within a 90° range calculated from the point of tangency between the lower fillet and the head support surface. Use an R0.3 roller, a rolling force of 1200N, a rolling time of 1000ms, a spindle speed of 500r / min, and a feed speed of 70r / min. join Figure 3 The deformation A value of the transition area between adjacent areas on both sides of the R-angle rod or head is 0.07mm; the pressing depth B value of the roller applied in the direction perpendicular to the R-angle surface is 0.07mm. The large deformation during rolling is to strengthen the R-angle under the head and to allow for machining after subsequent aging treatment. S5. Perform thread rolling on the parts; Install the support tool on the machine tool base, adjust the position and support height of the support tool to ensure that the workpiece and the center of the thread rolling wheel are in the correct relative position, align the thread line, and adjust the feed of the thread rolling wheel to extrude the thread. S6. Perform vacuum aging treatment on the parts; Vacuum degree ≤1.33×10 -2 Pa, vacuum heat treatment temperature is 726℃, hold for 500min, furnace cool to 615℃ at a cooling rate of 60℃ / h, hold for 510min, argon cooling, the purpose of which is to eliminate residual stress inside the product, stabilize the material structure and size, and at the same time achieve the standard performance requirements. S7. The parts are precision machined and shaped using CNC turning; See Figure 4 and Figure 5 A D-type collet is used to connect with the three-jaw chuck on the left side of the CNC lathe. The D-type collet mates with the head of the D-type head precision rod bolt. The center pin is tightened with the center hole at the tail of the D-type head precision rod to machine the precision rod. At the same time, the center hole at the tail is removed to ensure the precision rod ( Figure 4 The dimensions of the precision rod section 6 (machined by a precision machine), and the lower radius (R angle) of the head. Figure 4 The lower R-angle section 7 of the precision machining head should be avoided by R0.8, and the precision rod ( Figure 4 The precision of the precision rod part 6) is ≤0.009mm, while ensuring that the grain flow lines at the R-angle cold rolling are not damaged by the CNC lathe.

[0023] Example 4 A method for manufacturing a stress-delay type Inconel 718 high-temperature alloy D-head precision shank bolt includes the following steps: S1. Hot forging is performed on the head of the part; A 30kW high-frequency heater is used, with a heating coil inner diameter of φ15mm and 4 turns of the heating coil; the heating current is 920A, the heating time is 3s, the heat preservation current is 920A, and the heat preservation time is 3s, to ensure that the metallographic structure of the product head will not overheat or burn, and that the grain flow lines are normal. S2. Perform solution treatment on the parts; The heat treatment temperature is 786℃, held for 60 minutes, then heated to 940℃, held for 90 minutes, and cooled with argon gas to improve the plasticity and toughness of the material and prepare it for subsequent CNC lathe rough machining. S3. Perform CNC machining on the parts; See Figure 2 bare rod ( Figure 2 For the rough-machined section 4), a dimensional allowance of 0.18mm is provided for subsequent machining after aging treatment. A step for the center hole is also retained at the tail end. Figure 2 5) The step of the center hole in the medium-rough machining is not removed by turning, so that the part can be machined by turning after aging treatment; S4. Perform cold rolling on the lower radius of the part head; Cold rolling is performed on an arc within a 90° range calculated from the point of tangency between the lower fillet and the head support surface. Use an R0.3 roller, rolling force 1150N, rolling time 2000ms, spindle speed 500r / min, and feed speed 70r / min. join Figure 3 The deformation A value of the transition area between adjacent areas on both sides of the R-angle rod or head is 0.08mm; the pressing depth B value of the roller applied in the direction perpendicular to the R-angle surface is 0.08mm. The large deformation during rolling is to strengthen the R-angle under the head and to allow for machining after subsequent aging treatment. S5. Perform thread rolling on the parts; Install the support tool on the machine tool base, adjust the position and support height of the support tool to ensure that the workpiece and the center of the thread rolling wheel are in the correct relative position, align the thread line, and adjust the feed of the thread rolling wheel to extrude the thread. S6. Perform vacuum aging treatment on the parts; Vacuum degree ≤1.33×10 -2 Pa, vacuum heat treatment temperature is 719℃, hold for 480min, furnace cool to 620℃ at a cooling rate of 50℃ / h, hold for 480min, argon cooling, the purpose of which is to eliminate residual stress inside the product, stabilize the material structure and size, and at the same time meet the standard performance requirements. S7. The parts are precision machined and shaped using CNC turning; See Figure 4 and Figure 5 A D-type collet is used to connect with the three-jaw chuck on the left side of the CNC lathe. The D-type collet mates with the head of the D-type head precision rod bolt. The center pin is tightened with the center hole at the tail of the D-type head precision rod to machine the precision rod. At the same time, the center hole at the tail is removed to ensure the precision rod ( Figure 4 The dimensions of the precision rod section 6 (machined by a precision machine), and the lower radius (R angle) of the head. Figure 4 At the lower R-angle of the precision machining head (7), avoid turning the machine with a radius of R0.7. Precision rod ( Figure 4 The precision of the precision rod part 6) is ≤0.009mm, while ensuring that the grain flow lines at the R-angle cold rolling are not damaged by the CNC lathe.

[0024] Example 5 A method for manufacturing a stress-delay type Inconel 718 high-temperature alloy D-head precision shank bolt includes the following steps: S1. Hot forging is performed on the head of the part; A 30kW high-frequency heater is used, with a heating coil inner diameter of φ15mm and 4 turns. The heating current is 930A, the heating time is 3s, the holding current is 930A, and the holding time is 3s, ensuring that the metallographic structure of the product head will not overheat or burn, and that the grain flow lines are normal. S2. Perform solution treatment on the parts; The heat treatment temperature is 815℃, held for 65 minutes, then heated to 965℃, held for 99 minutes, and cooled with argon gas to improve the plasticity and toughness of the material and prepare it for subsequent CNC lathe rough machining. S3. Perform CNC machining on the parts; See Figure 2 bare rod ( Figure 2 For the rough-machined section 4), a dimensional allowance of 0.24mm is provided for subsequent machining after aging treatment. A step for the center hole is also retained at the tail end. Figure 2 5) The step of the center hole in the medium-rough machining is not removed by turning, so that the part can be machined by turning after aging treatment; S4. Perform cold rolling on the lower radius of the part head; Cold rolling is performed on an arc within a 90° range calculated from the point of tangency between the lower fillet and the head support surface. An R0.3 roller is used, with a rolling force of 1200N, a rolling time of 1500ms, a spindle speed of 500r / min, and a feed speed of 70r / min. join Figure 3 The deformation A value of the transition area between adjacent areas on both sides of the R-angle rod or head is 0.06mm; the pressing depth B value of the roller applied in the direction perpendicular to the R-angle surface is 0.06mm. The large deformation during rolling is to strengthen the R-angle under the head and to allow for machining after subsequent aging treatment. S5. Perform thread rolling on the parts; Install the support tool on the machine tool base, adjust the position and support height of the support tool to ensure that the workpiece and the center of the thread rolling wheel are in the correct relative position, align the thread line, and adjust the feed of the thread rolling wheel to extrude the thread. S6. Perform vacuum aging treatment on the parts; Vacuum degree ≤1.33×10 -2 Pa, vacuum heat treatment temperature is 722℃, hold for 510 min, furnace cool to 627℃ at a cooling rate of 56℃ / h, hold for 500 min, argon cooling, the purpose of which is to eliminate residual stress inside the product, stabilize the material structure and size, and at the same time achieve the standard performance requirements. S7. The parts are precision machined and shaped using CNC turning; See Figure 4 and Figure 5 A D-type collet is used to connect with the three-jaw chuck on the left side of the CNC lathe. The D-type collet mates with the head of the D-type head precision rod bolt. The center pin is tightened with the center hole at the tail of the D-type head precision rod to machine the precision rod. At the same time, the center hole at the tail is removed to ensure the precision rod ( Figure 4 The dimensions of the precision rod section 6 (machined by a precision machine), and the lower radius (R angle) of the head. Figure 4 The lower R-angle section 7 of the precision machining head should be avoided by R0.6, and the precision rod ( Figure 4 The precision of the precision rod part 6) is ≤0.009mm, while ensuring that the grain flow lines at the R-angle cold rolling are not damaged by the CNC lathe.

[0025] Tensile properties were tested on the stress-endurance type Inconel 718 high-temperature alloy D-head precision rod bolts manufactured by the methods described in Examples 1-5 above. For the room temperature tensile property test: at room temperature, it should withstand a tensile load of ≥47.793 kN and be tested until fracture was recorded. For the high-temperature tensile property test: at 650℃, it should withstand a tensile load of ≥37.469 kN and be tested until fracture was recorded. Ten pieces were randomly selected from each example, with five pieces undergoing room temperature tensile property testing and the other five undergoing high-temperature tensile property testing. The average value was calculated, and the results are shown in Tables 1 and 2 below.

[0026] Table 1. Room temperature tensile properties of stress-inducing Inconel 718 high-temperature alloy D-head precision shank bolts. Example Measured value Qualification 1 Maximum axial load of 52.019 kN, failure site is thread. qualified 2 Maximum axial load of 51.950 kN, failure site is thread. qualified 3 Maximum axial load of 51.916 kN, failure site is thread. qualified 4 Maximum axial load of 51.872 kN, failure site is thread. qualified 5 Maximum axial load of 51.796 kN, failure site is thread. qualified Table 2. High-Temperature Tensile Properties of Stress-Insulated Inconel 718 High-Temperature Alloy D-Head Precision Rod Bolts Example Measured value Qualification 1 Maximum axial load of 45.796 kN, failure site is thread. qualified 2 Maximum axial load of 45.503 kN, failure site is thread. qualified 3 Maximum axial load of 46.145 kN, failure site is threaded section. qualified 4 Maximum axial load of 45.997 kN, failure site is threaded section. qualified 5 Maximum axial load of 45.369 kN, failure site is threaded section. qualified Based on the above test results, it can be seen that the measured values ​​of the room temperature tensile strength of the stress-delay type Inconel 718 high-temperature alloy D-type head precision rod bolt exceed the standard value requirement by more than 8%, and the measured values ​​of the high-temperature tensile strength exceed the standard value requirement by more than 21%. The values ​​have a certain margin, and the failure points of the products are all at the threaded parts, and no fracture occurs at the lower fillet of the head. This indicates that the head-rod joint strength of the precision rod bolt obtained by the manufacturing method of this invention meets the standard requirements.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for manufacturing a stress-delay type Inconel 718 high-temperature alloy precision rod bolt, characterized in that, Includes the following steps: S1. Hot forging is performed on the head of the part; S2. Perform solution treatment on the parts; S3. Perform CNC machining on the part, leaving allowance for the dimensions of the smooth rod, while retaining the step of the center hole at the tail without removing it; S4. Perform cold rolling on the lower radius of the part head, including: Cold rolling is performed using R0.28~R0.32 rollers, and the deformation A value of the transition area between adjacent regions on both sides of the R-angle rod or head is 0.06~0.10mm; the pressing depth B value of the rollers applied in the direction perpendicular to the R-angle surface is 0.06~0.10mm. S5. Perform thread rolling on the parts; S6. Perform aging treatment on the parts; S7. Perform CNC turning precision machining on the parts, including: The part is machined using a collet and a tail center hole to machine a precision rod. At the same time, the tail center hole is removed. The bottom radius of the head is not machined with a radius of R0.6~R0.

8. The precision rod accuracy is ≤0.009mm.

2. The method for manufacturing stress-delay type Inconel 718 high-temperature alloy precision rod bolts according to claim 1, characterized in that, The heating current for hot forging the head of the part in step S1 is 910~930A, the heating time is 2~4s, the holding current is 910~930A, and the holding time is 2~4s.

3. The method for manufacturing stress-delay type Inconel 718 high-temperature alloy precision rod bolts according to claim 2, characterized in that, The hot upsetting process uses a 20~40kW high-frequency heater with a heating coil inner diameter of φ15~16mm and 4~6 turns.

4. The method for manufacturing stress-delay type Inconel 718 high-temperature alloy precision rod bolts according to claim 1, characterized in that, Step S2, which involves solution treatment of the part, includes: The heat treatment temperature is 785~815℃, held for 60~65min, then heated to 940~970℃, held for 90-99min, and cooled with argon gas.

5. The method for manufacturing stress-delay type Inconel 718 high-temperature alloy precision rod bolts according to claim 1, characterized in that, The allowance for the diameter of the optical rod in step S3 is 0.16~0.24mm.

6. The method for manufacturing stress-delay type Inconel 718 high-temperature alloy precision rod bolts according to claim 1, characterized in that, Step S4, which involves cold rolling the lower radius of the part head, further includes: Cold rolling is performed on an arc within a 90° range calculated from the point of tangency between the lower fillet and the head support surface. The rolling pressure is 1150~1250N, the rolling time is 1000~2000ms, the spindle speed is 400~500r / min, and the feed speed is 60~80r / min.

7. The method for manufacturing stress-delay type Inconel 718 high-temperature alloy precision rod bolts according to claim 1, characterized in that, Step S6, which involves aging the parts, includes: The heat treatment temperature is 710~726℃, held for 480~510min, then furnace cooled to 613~629℃ at a cooling rate of 48~64℃ / h, held for 480~510min, and then cooled with argon gas.

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