Manufacturing method of stress lasting type Inconel 718 high-temperature alloy precision rod bolt

Abstract

The invention belongs to the technical field of bolt fastener machining, and particularly relates to a manufacturing method of a stress lasting type Inconel 718 high-temperature alloy precision rod bolt. The manufacturing method comprises the following steps that the head of a part is subjected to hot upsetting forming; carrying out solution treatment on the part; performing numerical control lathe rough machining on the part, reserving the diameter size of the polished rod, and reserving a center hole step at the tail part without turning; cold rolling machining is conducted on the lower R angle of the head of the part; the part is subjected to thread rolling machining; aging treatment is conducted on the part; and carrying out numerical control lathe finish machining forming on the part. According to the manufacturing method, the problem that the size of the stress persistent Inconel 718 high-temperature alloy precision rod bolt is out of tolerance after the precision rod is subjected to aging treatment is effectively avoided, the precision of the precision rod is smaller than or equal to 0.009 mm, the precision requirement of the precision rod is met, and meanwhile the product performance is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of machining of bolt fasteners, and particularly relates to a manufacturing method for a stress endurance type Inconel 718 superalloy precision rod bolt. Background Art

[0002] The stress endurance type Inconel 718 superalloy D-head precision rod bolt has excellent connection performances such as high temperature resistance, corrosion resistance, vibration resistance, and saving installation space, and is widely used in the field of aircraft engines.

[0003] See Figure 1 , since relevant standards stipulate that the accuracy of the shank size (the precision rod part 1 in Figure 1 ) is ≤ 0.009 mm, and since this bolt is of the stress endurance type, its solution treatment needs to be carried out before finish machining, and the aging treatment needs to be carried out after the R-rolling machining (the R-rolling machining part 2 in Figure 1 ) and the thread rolling machining (the thread rolling machining part 3 in Figure 1 ). Its main processing technological process is: "hot heading the head → solution treatment → finish turning → R-rolling → thread rolling → aging treatment → surface treatment → finished product inspection".

[0004] The problems existing in the above processing method are: after the Inconel 718 material undergoes aging treatment, solid state phase transformation will occur, and the diameter size of the aged shank (the precision rod part 1 in Figure 1 ) is 0.009 mm - 0.010 mm smaller than that before aging, and its reduction amplitude has exceeded its tolerance range, not meeting the precision requirements of the precision rod, and it is impossible to effectively guarantee this size. How to guarantee the precision rod size while not damaging the R-rolling and thread rolling strengths of the bolt and ensuring the product performance is an urgent problem to be solved.

[0005] Chinese invention patent with the publication number CN102941447B discloses a manufacturing and processing technology for a bolt. The bolt is processed through a set of technological processes including hot heading - solution treatment - rough machining - vacuum aging treatment - finish machining and rolling the external thread - surface treatment - detection. Among them, the vacuum aging treatment is advanced between the rough machining and the finish machining, and a solution treatment is added between the hot heading and the rough machining, so as to ensure that between the finish machining of the semi-finished bolt workpiece and the rolling of the external thread, the internal metal streamline distribution of the semi-finished bolt workpiece is uniform, avoiding the problem that the internal metal streamline of the finished bolt workpiece is broken after the finish machining and the rolling of the external thread of the semi-finished bolt workpiece, ensuring the hardness and strength of the finished bolt workpiece, and further solving the problem that the internal metal streamline of the existing technology for machining a twelve-angle head flange face bolt is cut off. However, the bolt in this patent belongs to the anti-fatigue type, that is, the finish machining, thread rolling, and R-rolling processes are carried out after the final heat treatment, and there is no problem of size reduction after aging treatment, and there is no comparability with the processing of the stress endurance type bolt. Summary of the Invention

[0006] In view of the deficiencies of the existing technical methods, the present invention provides a manufacturing method for stress-rupture Inconel 718 superalloy precision rod bolts, effectively avoiding the problem of out-of-tolerance dimensions of stress-rupture Inconel 718 superalloy precision rod bolts after the precision rods are solution-treated. The precision of the precision rods is ≤0.009 mm, meeting the precision requirements of the precision rods, and at the same time ensuring the product performance.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A manufacturing method for stress-rupture Inconel 718 superalloy precision rod bolts, comprising the following steps: S1. Hot upset forming the head of the part; S2. Solution-treating the part; S3. Rough machining the part by numerical control turning, leaving a stock for the diameter of the smooth rod, and at the same time retaining the tip hole step at the tail without turning it off; S4. Cold rolling the R corner under the head of the part; S5. Thread rolling the part; S6. Aging-treating the part; S7. Finishing machining the part by numerical control turning to form.

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

[0009] Preferably, a 20 - 40 kW high-frequency heater is used for the hot upset forming, the inner diameter of the heating coil is φ15 - 16 mm, and the number of turns of the heating coil is 4 - 6 turns.

[0010] Preferably, in step S2, the solution-treatment of the part includes: The heat treatment temperature is 785 - 815 °C, holding for 60 - 65 min, heating up to 940 - 970 °C, holding for 90 - 99 min, and cooling with argon.

[0011] Preferably, in step S3, the stock for the diameter of the smooth rod is 0.16 - 0.24 mm.

[0012] Preferably, in step S4, the cold rolling of the R corner under the head of the part includes: Cold roll the arc within the range of 90° starting from the tangent point between the lower head fillet and the head support surface, use a roller with R0.28 - R0.32, 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.

[0013] Preferably, the deformation amount A value of the transition part between the adjacent areas on both sides of the R - angle rod part or the head is 0.06 - 0.10mm; the pressing depth B value applied by the roller 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°C, keep warm for 480 - 510min, cool in the furnace at a cooling rate of 48 - 64°C / h to 613 - 629°C, keep warm for 480 - 510min, and cool with argon.

[0015] Preferably, the CNC turning finish machining of the parts in step S7 includes: Use a collet and the tail center hole to turn the parts, machine the precision rod, and at the same time turn off the tail center hole. The R - angle under the head is avoided from machining according to R0.6 - R0.8, and the precision of the precision rod is ≤0.009mm.

[0016] The positive and beneficial effects of the present invention: 1. The anti - fatigue type bolt is characterized by being able 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 is usually to perform finish machining, thread rolling, and R - rolling on the product after the final heat treatment (aging treatment) to enhance the strength at the thread root and the R - angle under the head and improve the fatigue life. Since the finish machining, thread rolling, and R - rolling processes of the anti - fatigue type bolt are carried out after the final heat treatment (aging treatment), there is no problem of size reduction after aging treatment. And the present invention belongs to the stress - persistent type bolt, which is characterized by high creep resistance and relaxation resistance, and pays more attention to uniform stress, that is, to avoid creep fracture caused by local stress concentration. The processing technology is usually "hot - heading the head → solution treatment → finish turning → R - rolling → thread rolling → aging treatment → surface treatment → finished product inspection". First, R - rolling and thread rolling are carried out, and then aging heat treatment is carried out to reduce the surface stress concentration. The problem with the above - mentioned processing method is that: since the Inconel 718 material undergoes solid - state phase transformation after aging treatment, the diameter of the aged smooth rod is reduced by 0.009mm - 0.010mm compared with that before aging, and the reduction amplitude has exceeded its tolerance range, not meeting the precision requirements of the precision rod, and it is impossible to effectively guarantee this size.

[0017] When processing stress - persistent Inconel 718 superalloy precision rod bolts, the present invention first performs hot upset forming on the part head to ensure that the metallography of the product head will not overheat or burn, and the grain flow line is normal; performs solution treatment on the part to improve the plasticity and toughness of the material and prepare for subsequent CNC turning rough machining; uses CNC turning to rough - machine the smooth rod, and the size of the smooth rod does not need to be machined in place, leaving a margin for subsequent machining after aging treatment; performs cold rolling on the R - angle under the head. During rolling, the deformation amount is large, leaving a margin for subsequent machining after aging treatment; performs thread rolling on the part, and after thread rolling, performs aging treatment on the part to eliminate the internal residual stress of the product and stabilize the material structure and size; performs CNC turning finish - machining to form the part, ensuring the precision requirements of the precision rod and at the same time ensuring that the grain flow line at the cold - rolled R - angle is not damaged by CNC turning. The present invention divides the existing precision turning process into two steps: CNC turning rough machining and CNC turning finish - machining. The solution treatment is placed before rough machining, and the finish - machining is placed after aging treatment. First, rough - machine the smooth rod with a margin to prevent dimensional deviation after aging. The margin for the diameter of the smooth rod is 0.16 - 0.24 mm. At the same time, the deformation amount A value at the transition part between the R - angle rod part or both sides adjacent to the head is 0.06 - 0.10 mm, and the depth - of - cut B value applied by the roller in the direction perpendicular to the R - angle surface is 0.06 - 0.10 mm. Compared with the maximum standard value of 0.05 mm, the rolling deformation amount is increased during R - rolling to ensure that the grain flow line at the R - angle will not be damaged by subsequent machining after aging. After rough machining, R - rolling, and thread rolling, aging treatment is performed, and then the precision rod is finish - machined after aging treatment, effectively avoiding the dimensional deviation problem of stress - persistent Inconel 718 superalloy precision rod bolts after aging treatment of the precision rod. The precision of the precision rod is ≤0.009 mm, meeting the precision requirements of the precision rod and ensuring the product performance at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a D - type head precision rod bolt; Figure 2 It is a structural schematic diagram of the smooth rod rough - machined by CNC turning according to the present invention; Figure 3 It is a structural schematic diagram of a bolt with cold rolling on the R - angle under the head according to the present invention; Figure 4 It is a structural schematic diagram of a bolt finish - machined by CNC turning according to the present invention; Figure 5 It is a partial structural schematic diagram of a bolt finish - machined by CNC turning according to the present invention; In the figure: 1 is the precision rod part, 2 is the R - rolling processing part, 3 is the thread - rolling processing part, 4 is the rough - machined smooth rod part, 5 is the rough - machined tip hole step, 6 is the precision - turned precision rod part, 7 is the precision - turned R - angle under the head part. DETAILED DESCRIPTION OF THE INVENTION

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

[0020] Embodiment 1 A manufacturing method for a stress-resistant Inconel 718 superalloy D-head precision rod bolt includes the following steps: S1. Hot upset forming is performed on the part head. A 30kW high-frequency heater is used, the inner diameter of the heating coil is φ15mm, and the number of turns of the heating coil is 4; the heating current is 920A, the heating time is 3s, the holding current is 920A, and the holding time is 3s to ensure that the metallography of the product head will not overheat or burn, and the grain flow line is normal. S2. Solution treatment is performed on the part. The heat treatment temperature is 800°C, held for 65 minutes, heated to 954°C, held for 90 minutes, and cooled with argon to improve the plasticity and toughness of the material and prepare for subsequent rough CNC turning. S3. Rough CNC turning is performed on the part. See Figure 2 , for the bare rod ( Figure 2 The machining allowance for the rough machining of the bare rod part 4) is 0.20mm, which is reserved for the machining after the subsequent aging treatment. At the same time, the tip hole step ( Figure 2 The rough machining tip hole step 5) is not removed to facilitate the facing turning of the part after the aging treatment. S4. Cold rolling is performed on the R angle under the part head. Cold rolling is performed on the arc within 90° starting from the tangent point of the fillet under the head and the head support surface. An R0.3 roller is used, the rolling pressure is 1200N, the rolling time is 1000ms, the spindle speed is 500r / min, and the feed speed is 70r / min. See Figure 3 , the deformation amount A value of the transition part between the R angle rod part or the two adjacent regions on both sides of the head is 0.08mm; the pressing depth B value applied by the roller in the direction perpendicular to the R angle surface is 0.08mm. The deformation amount is large during rolling to strengthen the R angle under the head and reserve the allowance for the machining after the subsequent aging treatment. S5. Thread rolling is performed on the part. The tool carrier is installed on the machine tool base, the position and support height of the tool carrier are adjusted to ensure that the workpiece and the center of the thread rolling wheel are in the correct relative position, the thread floss is aligned, and the feed amount of the thread rolling wheel is adjusted to extrude the thread. S6. Vacuum aging treatment is performed on the part. The vacuum degree ≤ 1.33×10 -2Pa, the vacuum heat treatment temperature is 718 °C, hold for 500 min, furnace cool to 621 °C at a cooling rate of 56 °C / h, hold for 500 min, and cool with argon. The purpose is to eliminate the internal residual stress of the product, stabilize the material structure and dimensions, and at the same time meet the performance requirements of the standard; S7. Finish machining the parts by CNC turning; See Figure 4 and Figure 5 , connect the D-type jacket to the left three-jaw chuck of the CNC lathe, and the D-type jacket is matched with the head of the precision rod bolt of the D-type head. The center drill is tightened with the center hole at the tail of the precision rod of the D-type head. Machine the precision rod, and at the same time turn off the center hole at the tail to ensure the size of the precision rod ( Figure 4 finish machining the precision rod part 6 in the middle), and the R angle under the head ( Figure 4 finish machining the R angle part 7 under the head in the middle) is not machined according to R0.6 avoidance. The precision of the precision rod ( Figure 4 finish machining the precision rod part 6 in the middle) is ≤0.009 mm, and at the same time, it is ensured that the grain flow line at the cold rolling of the R angle is not damaged by the CNC lathe.

[0021] Example 2 A manufacturing method of a stress-resistant Inconel 718 superalloy D-type head precision rod bolt, comprising the following steps: S1. Hot upset the head of the part; Use a 30 kW high-frequency heater, the inner diameter of the heating coil is φ15 mm, and the number of turns of the heating coil is 4; the heating current is 920 A, the heating time is 3 s, the holding current is 920 A, and the holding time is 3 s to ensure that the metallography of the product head will not overheat or burn, and the grain flow line is normal; S2. Solution treatment of the part; The heat treatment temperature is 810 °C, hold for 60 min, heat up to 945 °C, hold for 90 min, and cool with argon to improve the plasticity and toughness of the material and prepare for the subsequent rough machining by CNC lathe; S3. Rough machining the part by CNC lathe; See Figure 2 , the size allowance of the optical rod ( Figure 2 rough machining the optical rod part 4) is 0.20 mm, which is reserved for machining after subsequent aging treatment, and at the same time, the center hole step ( Figure 2 rough machining the center hole step 5) at the tail is not machined off, which is convenient for turning the part after aging treatment; S4. Cold rolling the R angle under the head of the part; Cold roll the arc within 90° starting from the tangent point of the fillet under the head and the head support surface, use an R0.3 roller, the rolling pressure is 1200 N, the rolling time is 1000 ms, the spindle speed is 500 r / min, and the feed speed is 70 r / min; Participate in Figure 3 , the deformation amount A value of the transition part on both sides of the R-angle rod part or the head is 0.1 mm; the pressing depth B value applied by the roller in the direction perpendicular to the R-angle surface is 0.1 mm. The deformation amount is large during rolling, so as to strengthen the R-angle under the head and leave a margin for subsequent machining after aging treatment; S5. Perform thread rolling on the parts; Install the tool rest on the machine tool base, adjust the position and support height of the tool rest to ensure that the workpiece and the center of the thread rolling wheel are in the correct relative position, align the thread floss, and adjust the feed of the thread rolling wheel to extrude the thread; S6. Perform vacuum aging treatment on the parts; The vacuum degree ≤ 1.33×10 -2 Pa, the vacuum heat treatment temperature is 720 °C, keep warm for 510 min, cool in the furnace at a cooling rate of 60 °C / h to 624 °C, keep warm for 490 min, and cool with argon. The purpose is to eliminate the internal residual stress of the product, stabilize the material structure and dimensions, and at the same time meet the standard requirements for performance; S7. Perform CNC turning finish machining on the parts to form; See Figure 4 and Figure 5 , use a D-type bushing to connect with the left three-jaw chuck of the CNC lathe, and the D-type bushing is matched with the head of the D-type head precision rod bolt. The center pin is tightened with the tail center hole of the D-type head precision rod to machine the precision rod. At the same time, the tail center hole is removed by turning to ensure the size of the precision rod ( Figure 4 the precision turning precision rod part 6 in Figure 4 ), the R-angle under the head ( Figure 4 the precision turning R-angle under the head part 7 in

[0022] Example 3 A manufacturing method of a stress-resistant Inconel 718 superalloy D-type head precision rod bolt includes the following steps: S1. Perform hot upset forming on the head of the parts; Use a 30 kW high-frequency heater, the inner diameter of the heating coil is φ15 mm, and the number of turns of the heating coil is 4; the heating current is 920 A, the heating time is 4 s, the holding current is 920 A, and the holding time is 4 s to ensure that the metallography of the product head will not overheat or overburn and the grain flow line is normal; S2. Perform solution treatment on the parts; The heat treatment temperature is 790 °C, keep warm for 65 min, heat up to 960 °C, keep warm for 99 min, and cool with argon to improve the plasticity and toughness of the material and prepare for subsequent rough machining on the CNC lathe; S3. Perform rough machining on the parts by CNC turning; See Figure 2 , for the rough and semi-finish turning of the polished rod part ( Figure 2 No. 4), leave a machining allowance of 0.16 mm for subsequent machining after aging treatment. At the same time, retain the center hole step at the tail ( Figure 2 No. 5 of the rough and semi-finish turning of the center hole step) without turning it off, which is convenient for facing turning of the part after aging treatment; S4. Carry out cold rolling on the R corner under the head of the part; Carry out cold rolling on the arc within 90° starting from the tangent point of the fillet under the head and the head support surface. Use an R0.3 roller, rolling pressure of 1200 N, rolling time of 1000 ms, spindle speed of 500 r / min, and feed speed of 70 r / min; Refer to Figure 3 , the deformation amount A value of the transition part between the R corner rod part or both sides of the head is 0.07 mm; the depth of cut B value applied by the roller in the direction perpendicular to the R corner surface is 0.07 mm. The deformation is large during rolling. To strengthen the R corner under the head and leave an allowance for subsequent machining after aging treatment; S5. Carry out thread rolling on the part; Install the tool rest on the machine tool base, adjust the position and support height of the tool rest to ensure that the workpiece and the center of the thread rolling wheel are in the correct relative position. Align the thread tooth line and adjust the feed of the thread rolling wheel to extrude the thread; S6. Carry out vacuum aging treatment on the part; Vacuum degree ≤ 1.33×10 -2 Pa, the vacuum heat treatment temperature is 726 °C, hold for 500 min, cool in the furnace at a cooling rate of 60 °C / h to 615 °C, hold for 510 min, and cool with argon. The purpose is to eliminate the internal residual stress of the product, stabilize the material structure and dimensions, and at the same time meet the standard requirements for performance; S7. Carry out CNC turning for finish machining and forming on the part; See Figure 4 and Figure 5 , connect the D-type collet with the left three-jaw chuck of the CNC lathe, and the D-type collet is matched with the head of the precision rod bolt of the D-type head. The center drill is tightened with the center hole at the tail of the precision rod of the D-type head to machine the precision rod. At the same time, turn off the center hole at the tail to ensure the dimensions of the precision rod part ( Figure 4 No. 6 of the finish turning of the precision rod), the R corner under the head ( Figure 4 No. 7 of the finish turning of the R corner under the head) is not turned according to R0.8 for avoidance. The accuracy of the precision rod part ( Figure 4 No. 6 of the finish turning of the precision rod) is ≤ 0.009 mm, and at the same time, ensure that the grain flow line at the cold-rolled R corner is not damaged by CNC turning.

[0023] Example 4 A manufacturing method for a stress - durable Inconel 718 superalloy D - type head precision rod bolt, comprising the following steps: S1. Hot - upset the head of the part; Use a 30kW high - frequency heater with an inner diameter of the heating coil of φ15mm and 4 turns of the heating coil; the heating current is 920A, the heating time is 3s, the holding current is 920A, and the holding time is 3s to ensure that the metallography of the product head will not be over - heated or over - burned and the grain flow line is normal; S2. Solution - treat the part; The heat - treatment temperature is 786°C, hold for 60min, heat up to 940°C, hold for 90min, and cool with argon to improve the plasticity and toughness of the material and prepare for subsequent rough numerical - control turning; S3. Rough - machine the part by numerical - control turning; See Figure 2 , for the optical rod ( Figure 2 the rough - machining allowance for the optical rod part 4) is 0.18mm, which is the allowance for machining after subsequent aging treatment. At the same time, the tip hole step ( Figure 2 the rough - machining tip hole step 5) is not machined away to facilitate facing - turning machining of the part after aging treatment; S4. Cold - roll the R - corner under the head of the part; Cold - roll the arc within 90° starting from the tangent point of the fillet under the head and the head support surface. Use an R0.3 roller, the rolling pressure is 1150N, the rolling time is 2000ms, the spindle speed is 500r / min, and the feed speed is 70r / min; See Figure 3 , the deformation amount A value of the transition part between the R - corner rod part or both sides of the head is 0.08mm; the pressing - down depth B value applied by the roller in the direction perpendicular to the R - corner surface is 0.08mm. The deformation amount is large during rolling to strengthen the R - corner under the head and provide an allowance for machining after subsequent aging treatment; S5. Thread - roll the part; Install the tool - supporting device on the machine tool base, adjust the position and support height of the tool - supporting device to ensure that the workpiece and the center of the thread - rolling wheel are in the correct relative position, align the thread tooth line, and adjust the feed of the thread - rolling wheel to extrude the thread; S6. Vacuum aging - treat the part; The vacuum degree ≤ 1.33×10 -2 Pa, the vacuum heat - treatment temperature is 719°C, hold for 480min, cool in the furnace at a cooling rate of 50°C / h to 620°C, hold for 480min, and cool with argon. Its purpose is to eliminate the internal residual stress of the product, stabilize the material structure and dimensions, and simultaneously meet the standard - required performance; S7. Finish - machine the part by numerical - control turning to form; See Figure 4 and Figure 5 , connect the D-type jacket with the left three-jaw chuck of the CNC lathe, and the D-type jacket is fitted with the head of the D-type head precision rod bolt. The center drill is tightened with the center hole at the tail of the D-type head precision rod, and the precision rod is machined. At the same time, the center hole at the tail is turned off to ensure the precision rod ( Figure 4 precision turning of the precision rod part 6 in Figure 4 precision turning of the R corner under the head part 7 in Figure 4 precision turning of the precision rod part 6 in

[0024] Example 5 A manufacturing method for a stress-enduring Inconel 718 superalloy D-type head precision rod bolt includes the following steps: S1. Hot upset the head of the part; Use a 30kW high-frequency heater with an inner diameter of the heating coil of φ15mm and 4 turns of the heating coil; the heating current is 930A, the heating time is 3s, the holding current is 930A, and the holding time is 3s to ensure that the metallography of the product head will not overheat or burn and the grain flow line is normal; S2. Solution treat the part; The heat treatment temperature is 815°C, hold for 65 minutes, heat up to 965°C, hold for 99 minutes, and cool with argon to improve the plasticity and toughness of the material and prepare for subsequent rough machining on the CNC lathe; S3. Rough machine the part on the CNC lathe; See Figure 2 , leave a machining allowance of 0.24mm for the size of the optical rod ( Figure 2 rough machining of the optical rod part 4 in Figure 2 for subsequent machining after aging treatment, and at the same time, retain the center hole step at the tail ( rough machining of the center hole step 5 in Do not turn off the center hole step 5 for subsequent facing machining of the part after aging treatment; Participate in Figure 3 , the deformation amount A value of the transition part between the R corner rod part and the adjacent area on both sides of the head is 0.06mm; the pressing depth B value applied by the roller in the direction perpendicular to the R corner surface is 0.06mm, and the deformation amount is large during rolling. To strengthen the R corner under the head and leave an allowance for subsequent machining after aging treatment; S5. Thread rolling process the parts; Install the supporting tool on the machine tool base, adjust the position and supporting height of the supporting tool to ensure that the workpiece and the center of the thread rolling wheel are in the correct relative position, align the thread floss, and adjust the feed of the thread rolling wheel to extrude the thread; S6. Vacuum aging treatment for the parts; The vacuum degree ≤ 1.33×10 -2 Pa, the vacuum heat treatment temperature is 722 °C, keep warm for 510 min, cool in the furnace at a cooling rate of 56 °C / h to 627 °C, keep warm for 500 min, and cool with argon. The purpose is to eliminate the internal residual stress of the product, stabilize the material structure and dimensions, and at the same time meet the performance requirements of the standard; S7. Numerically controlled lathe finish machining to form the parts; Refer to Figure 4 and Figure 5 , connect the D-type bushing with the left three-jaw chuck of the numerically controlled lathe, and the D-type bushing is matched with the head of the precision rod bolt of the D-type head. The center drill is tightened with the tail center hole of the precision rod of the D-type head. Machine the precision rod, and at the same time turn off the tail center hole to ensure the size of the precision rod ( Figure 4 finish machining the precision rod part 6 in Figure 4 , the R angle under the head ( Figure 4 finish machining the R angle part 7 under the head in

[0025] is not machined according to R0.6 for avoidance. The precision of the precision rod (

[0026] finish machining the precision rod part 6 in Example Measured value Qualified judgment 1 Maximum axial load of 52.019 kN, failure location is the thread Qualified 2 Maximum axial load of 51.950 kN, failure location is the thread Qualified 3 Maximum axial load of 51.916 kN, failure location is the thread Qualified 4 Maximum axial load of 51.872 kN, failure location is the thread Qualified 5 Maximum axial load of 51.796 kN, failure location is the thread Qualified ≤ 0.009 mm, and at the same time ensure that the grain flow line at the cold rolling of the R angle is not damaged by the numerically controlled lathe.

[0025] Conduct tensile property tests on the stress endurance type Inconel 718 superalloy D-type head precision rod bolts processed and formed by the manufacturing methods of the above Examples 1-5. Normal temperature tensile property test: At room temperature, it should withstand a tensile load of ≥ 47.793 kN, and the test should be carried out until fracture and record the fracture; High temperature tensile property test: At 650 °C, it should withstand a tensile load of ≥ 37.469 kN, and the test should be carried out until fracture and record the fracture; Randomly select 10 pieces for each example, among which 5 pieces are subjected to normal temperature tensile property, and the other 5 pieces are subjected to high temperature tensile property test, and calculate the average value. The results are shown in Table 1 and Table 2 below.

[0026] Table 1 Normal temperature tensile properties of stress endurance type Inconel 718 superalloy D-type head precision rod bolts Example Measured value Qualified judgment 1 Maximum axial load of 52.019 kN, failure location is the thread Qualified 2 Maximum axial load of 51.950 kN, failure location is the thread Qualified 3 Maximum axial load of 51.916 kN, failure location is the thread Qualified 4 Maximum axial load of 51.872 kN, failure location is the thread Qualified 5 Maximum axial load of 51.796 kN, failure location is the thread Qualified Table 2 High temperature tensile properties of stress endurance type Inconel 718 superalloy D-type head precision rod bolts Example Measured value Qualified judgment 1 Maximum axial load of 45.796 kN, failure location is the thread Qualified 2 Maximum axial load of 45.503 kN, failure location is the thread Qualified 3 Maximum axial load of 46.145 kN, failure location is the thread Qualified 4 Maximum axial load of 45.997 kN, failure location is the thread Qualified 5 Maximum axial load of 45.369 kN, failure location is the thread Qualified According to the above test results, it can be seen that the measured room-temperature tensile properties of the stress-enduring Inconel 718 superalloy D-head precision rod bolts exceed the standard requirements by more than 8%, and the measured high-temperature tensile properties exceed the standard requirements by more than 21%. There is a certain margin in the values, and the failure parts of the products are all at the threads, and no fracture occurs at the fillet under the head, indicating that the strength of the head-rod joint of the precision rod bolts obtained by the manufacturing method of the present 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 not to limit them. Other modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A manufacturing method of a stress durable Inconel 718 superalloy precision rod bolt, characterized in that, It includes the following steps: S1. Hot upset forming the head of the part; S2. Solution treating the part; S3. Rough machining the part by CNC turning, leaving a stock for the smooth rod dimension, and at the same time retaining the center hole step at the tail without machining it off; S4. Cold rolling the R corner under the head of the part; S5. Thread rolling the part; S6. Aging treating the part; S7. Finish machining the part by CNC turning to form it.

2. The manufacturing method of the stress-enduring Inconel 718 superalloy precision rod bolt according to claim 1, characterized in that, For the hot upset forming of the head of the part in step S1, the heating current is 910 - 930 A, the heating time is 2 - 4 s, the holding current is 910 - 930 A, and the holding time is 2 - 4 s.

3. The manufacturing method of the stress-enduring Inconel 718 superalloy precision rod bolt according to claim 2, characterized in that, The hot upset forming uses a 20 - 40 kW high - frequency heater, the inner diameter of the heating coil is φ15 - 16 mm, and the number of turns of the heating coil is 4 - 6 turns.

4. The manufacturing method of the stress endurance type Inconel 718 superalloy precision rod bolt according to claim 1, characterized in that, For the solution treatment of the part in step S2, it includes: The heat treatment temperature is 785 - 815 °C, holding for 60 - 65 min, heating up to 940 - 970 °C, holding for 90 - 99 min, and cooling with argon.

5. The manufacturing method of the stress-enduring Inconel 718 superalloy precision rod bolt according to claim 1, characterized in that, For step S3, the stock for the smooth rod diameter dimension is 0.16 - 0.24 mm.

6. The manufacturing method of the stress endurance type Inconel 718 superalloy precision rod bolt according to claim 1, characterized in that, For the cold rolling of the R corner under the head of the part in step S4, it includes: Cold rolling the arc within a 90° range starting from the tangent point of the fillet under the head and the head support surface, using a roller with R0.28 - R0.32, the rolling pressure is 1150 - 1250 N, the rolling time is 1000 - 2000 ms, the spindle speed is 400 - 500 r / min, and the feed speed is 60 - 80 r / min.

7. The manufacturing method of the stress endurance type Inconel 718 superalloy precision rod bolt according to claim 6, characterized in that, The deformation amount A value of the transition part between the R - corner rod part or the two adjacent regions on both sides of the head is 0.06 - 0.10 mm; the depth of cut B value applied by the roller in the direction perpendicular to the R - corner surface is 0.06 - 0.10 mm.

8. The manufacturing method of the stress-enduring Inconel 718 superalloy precision rod bolt according to claim 1, characterized in that, For the aging treatment of the part in step S6, it includes: The heat treatment temperature is 710 - 726 °C, holding for 480 - 510 min, cooling in the furnace at a cooling rate of 48 - 64 °C / h to 613 - 629 °C, holding for 480 - 510 min, and cooling with argon.

9. The manufacturing method of the stress endurance type Inconel 718 superalloy precision rod bolt according to claim 1, characterized in that, For the finish machining of the part by CNC turning in step S7, it includes: Using a collet and the center hole at the tail to turn the part from the top, machining the precision rod, and at the same time machining off the center hole at the tail, avoiding machining the R corner under the head with R0.6 - R0.8, and the precision of the precision rod is ≤0.009 mm.

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