Apparatus and Method for Electromagnetic Induction Heat Treatment-Assisted Bending Vibration Machining of Internal Threads

Abstract

This invention relates to a device and method for machining internal threads using electromagnetic induction heat treatment-assisted bending vibration, belonging to the field of precision special machining technology. The invention utilizes electromagnetic induction heating to pre-treat the surface of the workpiece's hole wall, controlling the surface strength and improving thread integrity and surface quality. It introduces ultrasonic vibration into internal thread turning, generating high-frequency bending vibration by setting the length and thickness of the tool holder. This vibration drives the internal thread turning tool, which, under the axial vibration of a piezoelectric transducer, performs high-frequency micro-displacement oscillation in the XY plane around the tool holder, simultaneously coupling the macroscopic machining trajectory of the X and Y axes. This avoids chip clogging and increased friction during dry internal thread machining, reduces chip damage and burr formation due to untimely chip removal, further improves the surface quality of the internal thread, and ensures machining accuracy. The auxiliary heating rod, in conjunction with the electromagnetic induction coil, allows for rapid heat accumulation on the hole wall surface, improving heating efficiency.

Description

Technical Field

[0001] This invention belongs to the field of precision special machining technology, and in particular relates to a device and method for electromagnetic induction heat treatment-assisted bending vibration machining of internal threads in difficult-to-machine materials such as metal-based and ceramic-based composite materials. Background Technology

[0002] Metal matrix and ceramic matrix composites possess excellent properties such as high strength, low density, and wear resistance, making fasteners (bolts, nuts, etc.) produced from them widely used in aerospace, defense, and other fields. However, in the production process of metal matrix and ceramic matrix composite bolts and nuts, especially in the machining of nuts, the commonly used machining methods are tapping, milling, and turning. Due to the high hardness, brittleness, uneven distribution, and numerous hard particles in metal matrix and ceramic matrix composites, precision machining using these three methods results in thread breakage, low thread profile dimensional accuracy, numerous thread surface defects and burrs, severe tool wear, and high processing costs, making it difficult to meet the high-efficiency and high-quality machining requirements of fasteners for high-end equipment. Currently, some researchers have proposed improved internal thread machining technologies, such as designing dedicated diamond flat-bottomed tools (CN107052476A), designing new thread structures (CN113000952A), and designing low-density thread machining technology (CN 112759404A). However, these technologies still suffer from problems such as excessive stress concentration during machining, microcracks leading to poor thread integrity, narrow material facets, uneven residual stress, low machining efficiency, and high costs. These issues make it difficult to meet the requirements for mass production and reliable application of such structural components.

[0003] Pre-treating the area to be processed by laser heating to control material hardness, followed by ultrasonic vibration technology, is an effective means to improve thread integrity, thread profile accuracy, and reduce tool wear, and is currently an effective way to improve processing efficiency. However, laser heating is not easy to control, the selected area is affected by factors such as the size of the laser spot, and there are problems such as temperature concentration and uneven distribution during the heating process, making it difficult to apply to the machining of internal threads in metal matrix and ceramic matrix composite materials.

[0004] Therefore, there is an urgent need for a high-efficiency precision cutting device and method with low-damage internal thread machining characteristics to improve the accuracy and efficiency of precision internal thread machining, reduce the cost of internal thread machining, and meet the high reliability and long service life requirements of fasteners. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an apparatus and method for machining internal threads by electromagnetic induction heat treatment-assisted bending vibration, in order to solve the current technical problem of needing a high-efficiency, low-damage precision cutting device and method for internal threads.

[0006] An electromagnetic induction heat treatment-assisted bending vibration machining device for internal threads includes a lathe body and a high-frequency vibration turning device. The lathe body includes a machine tool, a high-speed spindle, a CNC X-axis, a CNC Y-axis, and a tool turret. The CNC Y-axis is mounted on the CNC X-axis. The tool turret includes a tool head and a tool holder fixedly connected to the tool head, and is mounted on the CNC Y-axis. One end of the high-speed spindle is mounted on the machine tool via a spindle clamp, and the other end of the high-speed spindle has a workpiece fixed to it. The high-frequency vibration turning device includes an ultrasonic generator, a finishing turning tool, an internal threading tool, a piezoelectric transducer, and a tool holder. The ultrasonic generator is mounted on the machine tool. The internal threading tool is mounted on the piezoelectric transducer via a tool holder. The piezoelectric transducer and the finishing turning tool are mounted on the tool head via a clamp. The ultrasonic generator and the piezoelectric transducer are electrically connected.

[0007] The device for electromagnetic induction heat treatment-assisted bending vibration machining of internal threads also includes an electromagnetic induction heating device and a bus control system.

[0008] The electromagnetic induction heating device includes an electromagnetic induction main unit, a cylinder, a folding rod, an electromagnetic induction coil, and an auxiliary heating rod. The electromagnetic induction main unit is fixedly mounted on a machine tool; the cylinder is fixedly mounted on a spindle fixture; one part of the folding rod is a fixed part, and the other part is a folding part, which are rotatably connected. The fixed part is fixedly connected to the telescopic rod of the cylinder, and the electromagnetic induction coil is fixedly mounted on the folding part; the electromagnetic induction coil is sleeved around the workpiece, and the center of the electromagnetic induction coil coincides with the axis of the high-speed spindle, and the electromagnetic induction coil is connected to the electromagnetic induction main unit; the auxiliary heating rod is mounted on the tool head through a fixture, and is inserted into the inner hole of the workpiece during the preheating process before internal thread turning to heat the hole wall of the workpiece in contact.

[0009] The bus control system is equipped with a machining program and a control system program. The bus control system is connected to the electromagnetic induction host, ultrasonic generator, cylinder and lathe body respectively through signal lines. The machining program is determined by the optimal machining parameters for internal thread turning obtained by simulation of electromagnetic induction heat treatment assisted bending vibration.

[0010] The relationship between the length l and thickness h of the tool holder is as follows:

[0011]

[0012] In the formula, A1 is the first mode shape coefficient; c is the sound velocity of the material; f j The natural frequency is 20kHz.

[0013] The simulation includes:

[0014] 1) Based on the material properties and dimensions of the workpiece to be processed, an electromagnetic induction heating finite element model is established. By changing the output power, output frequency, output current, spindle speed, feed rate, and cross-sectional area of ​​the auxiliary heating rod, the heat-affected zone of the workpiece is simulated. The depth value corresponding to the temperature is extracted from the simulation results. This temperature is the effective softening temperature for reducing the material hardness of the workpiece. It is determined by consulting relevant literature or corresponding experiments, and the effective depth for reducing the material hardness of the workpiece, i.e., the depth of cut 'a', is established. p Regarding the output power P of the electromagnetic induction host i Electromagnetic induction host output frequency f i Electromagnetic induction host output current I i Spindle speed n, feed rate v r And the multiple regression equation for the cross-sectional area S of the auxiliary heating rod;

[0015]

[0016] In the formula, α is the regression coefficient; a1, a2, a3, a4, a5, and a6 are all parametric exponents.

[0017] 2) Based on the material properties and dimensions of the workpiece, finishing turning tool, and internal threading tool, establish a finite element model for electromagnetic induction heating-assisted cutting. This model is then modified by changing the amplitude A, spindle speed n, and feed rate v. r Back cut amount a p Simulations were performed on the cutting forces during machining, establishing the cutting forces with respect to amplitude A, spindle speed n, and feed rate v. r and back cut amount a p The multiple linear regression equation;

[0018]

[0019] In the formula, β, λ, ε, and τ are all regression coefficients;

[0020] The optimal machining parameters for internal thread turning assisted by electromagnetic induction heat treatment and bending vibration were obtained through simulation.

[0021] The processing parameters include electromagnetic induction output power, electromagnetic induction host output frequency, electromagnetic induction host output current, vibration frequency, amplitude, spindle speed, feed rate, depth of cut, and auxiliary heating rod model.

[0022] A method for machining internal threads using electromagnetic induction heat treatment-assisted bending vibration, comprising the aforementioned apparatus for machining internal threads using electromagnetic induction heat treatment-assisted bending vibration, includes the following steps, which are performed sequentially:

[0023] Step 1: Use ANSYS Workbench and Maxwell finite element simulation software to perform bidirectional coupling simulation of electromagnetic induction heating and cutting simulation respectively, and establish the effective depth of material hardness reduction of the workpiece, i.e., the depth of cut 'a'. p Regarding the output power P of the electromagnetic induction host i The output frequency f of the electromagnetic induction host i The output current I of the electromagnetic induction host i The high-speed spindle speed n and the high-speed spindle feed rate v r And the multiple regression equation for the cross-sectional area S of the auxiliary heating rod, and the cutting force with respect to the output vibration frequency f of the ultrasonic generator. j The output amplitude A of the ultrasonic generator, the rotational speed n of the high-speed spindle, and the feed rate v of the high-speed spindle. r and back cut amount a p The second multiple linear regression equation is used to obtain the optimal parameter values ​​of the electromagnetic induction host's output power, output frequency, output current, ultrasonic generator's output vibration frequency, ultrasonic generator's output amplitude, high-speed spindle speed, high-speed spindle feed rate, depth of cut, and auxiliary heating rod model. These parameters are then input into the bus control system to formulate the corresponding machining program.

[0024] The relationship between the length l and thickness h of the tool holder is set as follows:

[0025]

[0026] In the formula, A1 is the first mode shape coefficient; c is the sound velocity of the material; f j The natural frequency is 20kHz.

[0027] Step 2: Install and fix the workpiece to be processed onto the high-speed spindle. Fix the electromagnetic induction coil onto the workpiece by adjusting the telescopic rod and folding rod of the cylinder, and adjust the distance between the electromagnetic induction coil and the workpiece.

[0028] Step 3: Turn on the bus control system to control the CNC X-axis, CNC Y-axis, tool turret, and cylinder extension rod to return the machine tool to zero and set the tool; turn on the electromagnetic induction host, set the output power, output frequency, and output current, and make the fixed heating area of ​​the electromagnetic induction coil on the workpiece circular, with the center of the circle coinciding with the spindle.

[0029] Step 4: Start the machining program in the bus control system and perform electromagnetic induction heating-assisted precision turning of the inner hole using a precision turning tool;

[0030] Step 5: After the internal hole finish turning is completed, the CNC X-axis is zeroed through the bus control system, and the tool head is switched to the auxiliary heating rod to preheat the hole wall.

[0031] Step Six: After the hole wall heating pretreatment reaches the set time, the CNC X-axis is controlled to return to zero again through the bus control system, and the tool head is controlled to switch the auxiliary heating rod to the internal thread turning tool. At the same time, the ultrasonic generator is turned on and the output amplitude and frequency are set. Due to the setting of the tool holder length l and thickness h, high-frequency bending vibration can be generated, which drives the tool tip of the internal thread turning tool. Under the axial vibration of the piezoelectric transducer, it realizes high-frequency micro-displacement oscillation in the XY plane with the tool holder as the center, while coupling the macroscopic machining trajectory of the X-axis and Y-axis, and performs electromagnetic induction heat treatment assisted bending vibration internal thread turning on the workpiece.

[0032] Thus, a method for machining internal threads using electromagnetic induction heat treatment-assisted bending vibration is completed.

[0033] The bidirectional coupling simulation of electromagnetic induction heating is specifically as follows:

[0034] Based on the material properties and dimensions of the workpiece to be processed, an electromagnetic induction heating finite element model was established using ANSYS Workbench finite element simulation software. The model was then modified by changing the output power P of the electromagnetic induction host. i The output frequency f of the electromagnetic induction host i The output current I of the electromagnetic induction host i The high-speed spindle speed n and the high-speed spindle feed rate v r The cross-sectional area S of the auxiliary heating rod was used to simulate the heat-affected zone of the workpiece. The depth value of the corresponding temperature was extracted from the simulation results. This temperature is the effective softening temperature for reducing the material hardness of the workpiece. It was determined by consulting relevant literature or corresponding experiments. The established multiple regression equation is as follows:

[0035]

[0036] In the formula, α is the coefficient of the regression formula; a1, a2, a3, a4, a5, and a6 are all parametric exponents.

[0037] The output current and output frequency of the electromagnetic induction host in steps three, four, and six, as well as the setting of the hole wall heating pretreatment time in step five, are all obtained through the simulation of the heat-affected zone of the workpiece in step one.

[0038] The cutting simulation is specifically as follows:

[0039] The electromagnetic induction heating-assisted cutting finite element model is established based on the material properties and dimensions of the workpiece, the finishing turning tool, and the internal threading tool. This model is then modified by changing the output amplitude A of the ultrasonic generator, the rotational speed n of the high-speed spindle, and the feed rate v of the high-speed spindle. r Back cut amount a pThe second multiple linear regression equation was established by simulating the cutting force during machining:

[0040]

[0041] In the formula, β, λ, ε, and τ are all regression coefficients. This is the cutting force.

[0042] In step three, the electromagnetic induction host receives instructions from the bus control system and generates current to heat up the electromagnetic induction coil.

[0043] In step six, the ultrasonic generator receives instructions from the bus control system and generates an electrical signal to cause the piezoelectric transducer to drive the internal thread cutting tool to vibrate at high frequency.

[0044] Through the above design scheme, the present invention can bring the following beneficial effects:

[0045] 1. This invention utilizes electromagnetic induction heating to pretreat the surface of the hole wall of the workpiece, regulate the surface strength of the hole wall, and then apply high-frequency vibration to the internal thread cutting tool. This solves the problems of stress concentration, uneven residual stress, microcracks, and low processing efficiency in the internal thread cutting process of metal-based and ceramic-based composite materials, improves the integrity and surface quality of the thread teeth, and realizes efficient and low-damage preparation of internal threads of metal-based and ceramic-based composite materials.

[0046] 2. This invention utilizes metal-based and ceramic-based composite materials for internal thread turning. By setting the length l and thickness h of the tool holder, high-frequency bending vibration is generated, which drives the tip of the internal thread turning tool. Under the axial vibration of the piezoelectric transducer, the tool tip makes high-frequency micro-displacement oscillation in the XY plane with the tool holder as the center, while coupling the macroscopic machining trajectory of the X and Y axes. This can avoid the phenomenon of chip blockage and increased friction during dry internal thread machining, reduce the generation of burrs and scratches on the thread surface due to untimely chip removal, further improve the surface quality of the internal thread teeth, and ensure machining accuracy.

[0047] 3. This invention utilizes an auxiliary heating rod in conjunction with an electromagnetic induction coil, which allows heat to be rapidly superimposed on the surface of the hole wall, improving heating efficiency. Furthermore, the diameter of the auxiliary heating rod can be changed to accommodate various thread diameter series, making it suitable for high-volume, multi-variety processing needs.

[0048] 4. The CNC machine tool design used in this invention is simple in structure and easy to operate, and greatly reduces the processing cost of internal threads in metal-based and ceramic-based composite materials. Attached Figure Description

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0050] Figure 1This is a schematic diagram of the device in the electromagnetic induction heat treatment-assisted bending vibration machining of internal threads according to the present invention.

[0051] Figure 2 This is a schematic diagram of the high-frequency vibration turning device in the device and method for electromagnetic induction heat treatment-assisted bending vibration machining of internal threads of the present invention.

[0052] In the diagram, 1-high-speed spindle, 2-cylinder, 3-ultrasonic generator, 4-folding rod, 5-tool head, 6-tool post, 7-CNC Y-axis, 8-CNC X-axis, 9-electromagnetic induction host, 10-electromagnetic induction coil, 11-workpiece, 12-spindle fixture, 13-precision turning tool, 14-internal threading tool, 15-piezoelectric transducer, 16-tool holder, 17-auxiliary heating rod. Detailed Implementation

[0053] like Figure 1 and Figure 2 As shown, an electromagnetic induction pretreatment bending vibration assisted internal thread machining device includes a lathe body, an electromagnetic induction heating device, a high-frequency vibration turning device, and a bus control system.

[0054] The lathe body includes a machine tool, a high-speed spindle 1, a CNC X-axis 8, a CNC Y-axis 7, a tool turret, and a workpiece 11. The tool turret includes a tool head 5 and a tool holder 6. The tool head 5 is fixedly connected to the tool holder 6. The CNC Y-axis 7 is mounted on the CNC X-axis 8, and the tool holder 6 is mounted on the CNC Y-axis 7. The high-speed spindle 1 is mounted on the machine tool through a spindle clamp 12, and the workpiece 11 is mounted on the high-speed spindle 1.

[0055] The electromagnetic induction heating device includes an electromagnetic induction host 9, a cylinder 2, a folding rod 4, an electromagnetic induction coil 10, and an auxiliary heating rod 17. The electromagnetic induction host 9 is mounted on a machine tool. The electromagnetic induction coil 10 is fixed on the folding rod 4, which is mounted on the telescopic rod of the cylinder 2. To facilitate workpiece assembly and disassembly and workpiece heating, the electromagnetic induction coil 10 can be adjusted via the folding rod 4 connected to the telescopic rod of the cylinder 2. The cylinder 2 is mounted on a spindle clamp 12. The auxiliary heating rod 17 is mounted on a tool turret 5 via a clamp. The electromagnetic induction coil 10 is horizontally positioned around the workpiece 11, and the center of the electromagnetic induction coil 10 coincides with the axial direction of the high-speed spindle 1. The electromagnetic induction host 9 is connected to the electromagnetic induction coil 10.

[0056] The high-frequency vibration turning device includes an ultrasonic generator 3, a finishing turning tool 13, an internal threading turning tool 14, a piezoelectric transducer 15, and a tool holder 16. The ultrasonic generator 3 is mounted on the machine tool. The internal threading turning tool 14 is mounted on the piezoelectric transducer 15 via the tool holder 16. The piezoelectric transducer 15 and the finishing turning tool 13 are mounted on the tool disc 5 via a fixture. The ultrasonic generator 3 is connected to the piezoelectric transducer 15.

[0057] The bus control system is equipped with a machining program and a control system program, which are connected to the electromagnetic induction host 9, the ultrasonic generator 3, the cylinder 2 and the lathe body respectively via signal lines.

[0058] A method for machining internal threads using electromagnetic induction heat treatment-assisted bending vibration, comprising the aforementioned apparatus for machining internal threads using electromagnetic induction heat treatment-assisted bending vibration, includes the following steps, which are performed sequentially:

[0059] Step 1: Use ANSYS Workbench and Maxwell finite element simulation software to perform bidirectional coupling simulation of electromagnetic induction heating and cutting simulation. This provides guidance for setting parameters such as electromagnetic induction output power, electromagnetic induction host output frequency, electromagnetic induction host output current, vibration frequency, amplitude, spindle speed, feed rate, depth of cut, and selecting the auxiliary heating rod model in the bus control system program.

[0060] 1) Based on the material properties and dimensions of the workpiece 11 to be processed, an electromagnetic induction heating finite element model is established. By changing the output power, output frequency, output current, speed, feed rate of the high-speed spindle 1, and cross-sectional area of ​​the auxiliary heating rod 17 of the electromagnetic induction host 9, the heat-affected zone of the workpiece 11 is simulated. The depth value of the corresponding temperature is extracted from the simulation results. This temperature is the effective softening temperature for reducing material hardness, which can be determined by consulting relevant literature or corresponding experiments. The effective depth for reducing material hardness, i.e., the depth of cut a, is established. p Regarding the output power P of the electromagnetic induction host 9 i The output frequency f of the electromagnetic induction host 9 i The output current I of the electromagnetic induction host 9 i The rotational speed n of high-speed spindle 1 and the feed rate v of high-speed spindle 1. r And the multiple regression equation for the cross-sectional area S of the auxiliary heating rod 17;

[0061]

[0062] In the formula, α is the coefficient of the regression formula; a1, a2, a3, a4, a5, and a6 are all parametric exponents.

[0063] 2) Based on the material properties and dimensions of the workpiece 11 and the cutting tool, establish a finite element model for electromagnetic induction heating-assisted cutting. This model is then modified by changing the output amplitude A of the ultrasonic generator 3, the rotational speed n of the high-speed spindle 1, and the feed rate v of the high-speed spindle 1. r Back cut amount a p Simulations were performed on the cutting forces during machining, establishing the cutting forces with respect to amplitude A, spindle speed n, and feed rate v. r and back cut amount a p The second multiple linear regression equation:

[0064]

[0065] In the formula, β, λ, ε, and τ are all regression coefficients;

[0066] The relationship between the length l and thickness h of the tool holder is set as follows:

[0067]

[0068] In the formula, A1 is the first mode shape coefficient, c is the sound velocity of the material, and f j The natural frequency is 20kHz.

[0069] 3) Based on the multiple regression equations regarding the effective depth of material hardness reduction and cutting force, the optimal machining parameters for electromagnetic induction pretreatment bending vibration-assisted internal thread turning are formulated, and the corresponding machining program is developed.

[0070] Step 2: Install and fix the workpiece 11 to be processed onto the high-speed spindle 1. Fix the electromagnetic induction coil 10 onto the workpiece 11 by adjusting the telescopic rod and folding rod 4 of the cylinder 2, and adjust the distance between the electromagnetic induction coil 10 and the workpiece 11.

[0071] Step 3: Turn on the bus control system to control the CNC X-axis 8, CNC Y-axis 9, tool turret and cylinder 2 extension rod to return the machine tool to zero and set the tool; turn on the electromagnetic induction host 9, set the output current and the output frequency of the electromagnetic induction host 9, and set the fixed heating area of ​​the electromagnetic induction coil 10 on the workpiece to be circular, with the center of the circle coinciding with the high-speed spindle 1.

[0072] Step 4: Open the machining program in the bus control system and perform electromagnetic induction heating-assisted precision turning of the inner hole;

[0073] Step 5: After the inner hole finish turning is completed, the CNC X-axis 8 is controlled to return to zero through the bus control system, and the tool head is controlled to switch the finish turning tool 13 to the auxiliary heating rod 17 to perform preheating treatment on the hole wall.

[0074] Step Six: After the pretreatment of the hole wall heating is completed, the CNC X-axis 8 is controlled to return to zero again through the bus control system, and the tool head is controlled to switch the auxiliary heating rod 17 to the internal thread turning tool 14. At the same time, the ultrasonic generator 3 is turned on and the output amplitude and frequency are set. Due to the setting of the length l and thickness h of the tool holder 16, high-frequency bending vibration can be generated, which drives the tool tip of the internal thread turning tool 14. Under the axial vibration of the piezoelectric transducer 15, it realizes the high-frequency micro-displacement oscillation of the XY plane with the tool holder 16 as the center, while coupling the macroscopic machining trajectory of the X-axis and Y-axis, and performs electromagnetic induction heat treatment assisted bending vibration internal thread turning on the workpiece 11.

[0075] Thus, the method of machining internal threads by electromagnetic induction heat treatment assisted by bending vibration is completed.

[0076] In step three, the electromagnetic induction host 9 receives instructions from the bus control system and generates current to heat the induction coil.

[0077] The output current and output frequency of the electromagnetic induction host 9 in steps three, four, and six, as well as the setting of the hole wall heating pretreatment time in step five, are all obtained through temperature field simulation in step one.

[0078] In step six, the ultrasonic generator 3 receives instructions from the bus control system and generates an electrical signal to cause the piezoelectric transducer 15 to drive the internal thread cutting tool 14 to vibrate at high frequency.

Claims

1. An apparatus for electromagnetic induction heat treatment-assisted bending vibration machining of internal threads, comprising a lathe body and a high-frequency vibration turning device, wherein the lathe body comprises a machine tool, a high-speed spindle (1), a CNC X-axis (8), a CNC Y-axis (7), and a tool turret; the CNC Y-axis (7) is mounted on the CNC X-axis (8); the tool turret comprises a tool head (5) and a tool holder (6) fixedly connected to the tool head (5), and the tool turret is mounted on the CNC Y-axis (7); one end of the high-speed spindle (1) is mounted on the machine tool via a spindle clamp (12), and the high-speed spindle (1) The other end is fixed to the workpiece (11); the high-frequency vibration turning device includes an ultrasonic generator (3), a precision turning tool (13), an internal thread turning tool (14), a piezoelectric transducer (15), and a tool holder (16); the ultrasonic generator (3) is mounted on the machine tool; the internal thread turning tool (14) is mounted on the piezoelectric transducer (15) via the tool holder (16); the piezoelectric transducer (15) and the precision turning tool (13) are mounted on the tool disc (5) via a fixture; the ultrasonic generator (3) is electrically connected to the piezoelectric transducer (15); Its characteristics are: It also includes an electromagnetic induction heating device and a bus control system; The electromagnetic induction heating device includes an electromagnetic induction host (9), a cylinder (2), a folding rod (4), an electromagnetic induction coil (10), and an auxiliary heating rod (17). The electromagnetic induction host (9) is fixedly installed on the machine tool; the cylinder (2) is fixedly installed on the spindle fixture (12); one part of the folding rod (4) is a fixed part, and the other part is a folding part. The fixed part and the folding part are rotatably connected. The fixed part is fixedly connected to the telescopic rod of the cylinder (2). The electromagnetic induction coil (10) is fixedly installed on the folding part; the electromagnetic induction coil (10) is fitted around the workpiece (11), and the center of the electromagnetic induction coil (10) coincides with the axis of the high-speed spindle (1). The electromagnetic induction coil (10) is connected to the electromagnetic induction host (9); the auxiliary heating rod (17) is installed on the cutter head (5) through a fixture. The auxiliary heating rod (17) is inserted into the inner hole of the workpiece (11) in the preheating process before internal thread turning to heat the hole wall of the workpiece (11) in contact. The bus control system is equipped with a machining program and a control system program. The bus control system is connected to the electromagnetic induction host (9), ultrasonic generator (3), cylinder (2) and lathe body respectively through signal lines. The machining program is determined by the optimal machining parameters for internal thread turning obtained by simulation of electromagnetic induction heat treatment assisted bending vibration. The relationship between the length l and the thickness h of the tool holder (16) is as follows: In the formula, A1 is the first mode shape coefficient; c is the sound velocity of the material; f j The natural frequency is 20kHz.

2. The apparatus for electromagnetic induction heat treatment-assisted bending vibration machining of internal threads according to claim 1, characterized in that: The simulation includes: 1) Based on the material properties and dimensions of the workpiece (11) to be processed, an electromagnetic induction heating finite element model is established. By changing the output power of the electromagnetic induction host (9), the electromagnetic induction output frequency, the electromagnetic induction output current, the spindle speed, the feed rate, and the cross-sectional area of ​​the auxiliary heating rod (17), the heat-affected zone of the workpiece (11) is simulated. The depth value of the corresponding temperature is extracted from the simulation results. This temperature is the effective softening temperature of the material hardness reduction of the workpiece (11). It is determined by consulting relevant literature or corresponding experiments. The effective depth of the material hardness reduction of the workpiece (11), i.e., the depth of cut a, is established. p Regarding the output power P of the electromagnetic induction host (9) i Electromagnetic induction host output frequency f i Electromagnetic induction host output current I i Spindle speed n, feed rate v r And the multiple regression equation for the cross-sectional area S of the auxiliary heating rod (17); In the formula, α is the regression coefficient; a1, a2, a3, a4, a5, and a6 are all parametric exponents. 2) Based on the material properties and dimensions of the workpiece (11), the finishing turning tool (13), and the internal threading tool (14), an electromagnetic induction heating assisted cutting finite element model is established. By changing the amplitude A, the spindle speed n, and the feed rate v r Back cut amount a p Simulations were performed on the cutting forces during machining, establishing the cutting forces with respect to amplitude A, spindle speed n, and feed rate v. r and back cut amount a p The multiple linear regression equation; In the formula, β, λ, ε, and τ are all regression coefficients; The optimal machining parameters for internal thread turning assisted by electromagnetic induction heat treatment and bending vibration were obtained through simulation.

3. The apparatus for electromagnetic induction heat treatment-assisted bending vibration machining of internal threads according to claim 1 or 2, characterized in that: The processing parameters include electromagnetic induction output power, electromagnetic induction host output frequency, electromagnetic induction host output current, vibration frequency, amplitude, spindle speed, feed rate, depth of cut, and auxiliary heating rod (17) model.

4. A method for machining internal threads using electromagnetic induction heat treatment assisted by bending vibration, utilizing the apparatus for machining internal threads using electromagnetic induction heat treatment assisted by bending vibration as described in claim 1, characterized in that: The steps include the following steps, and the following steps are performed in sequence: Step 1: Use ANSYS Workbench and Maxwell finite element simulation software to perform bidirectional coupling simulation of electromagnetic induction heating and cutting simulation respectively, and establish the effective depth of material hardness reduction of workpiece (11), i.e., the depth of cut a. p Regarding the output power P of the electromagnetic induction host (9) i The output frequency f of the electromagnetic induction host (9) i The output current I of the electromagnetic induction host (9) i The rotational speed n of the high-speed spindle (1) and the feed rate v of the high-speed spindle (1) r And the multiple regression equation for the cross-sectional area S of the auxiliary heating rod (17), and the cutting force with respect to the output vibration frequency f of the ultrasonic generator (3). j The output amplitude A of the ultrasonic generator (3), the rotational speed n of the high-speed spindle (1), and the feed rate v of the high-speed spindle (1) r and back cut amount a p The second multiple linear regression equation is used to obtain the output power of the electromagnetic induction host (9), the output frequency of the electromagnetic induction host (9), the output current of the electromagnetic induction host (9), the output vibration frequency of the ultrasonic generator (3), the output amplitude of the ultrasonic generator (3), the rotation speed of the high-speed spindle (1), the feed amount of the high-speed spindle (1), the setting of the back depth of cut parameters, and the optimal parameter value of the auxiliary heating rod (17) model. These parameters are then input into the bus control system and the corresponding machining program is formulated. The relationship between the length l and thickness h of the tool holder (16) is set as follows: In the formula, A1 is the first mode shape coefficient; c is the sound velocity of the material; f j The natural frequency is 20kHz. Step 2: Install and fix the workpiece (11) to be processed onto the high-speed spindle (1). Fix the electromagnetic induction coil (10) onto the workpiece (11) by adjusting the telescopic rod and folding rod (4) of the cylinder (2). Adjust the distance between the electromagnetic induction coil (10) and the workpiece (11). Step 3: Open the bus control system to control the extension rods of the CNC X-axis (8), CNC Y-axis (7), tool turret and cylinder (2) to return the machine tool to zero and set the tool; turn on the electromagnetic induction host (9), set the output power, output frequency and output current, and the fixed heating area of ​​the electromagnetic induction coil (10) on the workpiece (11) is circular, with the center of the circle coinciding with the spindle; Step 4: Start the machining program in the bus control system and perform electromagnetic induction heating-assisted precision turning of the inner hole using a precision turning tool (13); Step 5: After the inner hole finish turning is completed, the CNC X-axis (8) is controlled to return to zero through the bus control system, and the tool head (5) is controlled to switch the finish turning tool (13) to the auxiliary heating rod (17) to perform preheating treatment on the hole wall; Step 6: After the hole wall heating pretreatment is completed to the set time, the CNC X-axis (8) is controlled to return to zero again through the bus control system, and the tool head (5) is controlled to switch the auxiliary heating rod (17) to the internal thread turning tool (14). At the same time, the ultrasonic generator (3) is turned on and the output amplitude and frequency are set. Due to the setting of the length l and thickness h of the tool holder (16), high-frequency bending vibration can be generated, and the tool tip of the internal thread turning tool (14) is driven to achieve high-frequency micro-displacement swing of the XY plane with the tool holder (16) as the center under the axial vibration of the piezoelectric transducer (15), while coupling the macroscopic machining trajectory of the X-axis and Y-axis, and performing electromagnetic induction heat treatment assisted bending vibration internal thread turning on the workpiece (11). Thus, a method for machining internal threads using electromagnetic induction heat treatment-assisted bending vibration is completed.

5. The method for machining internal threads using electromagnetic induction heat treatment assisted by bending vibration according to claim 4, characterized in that: The bidirectional coupling simulation of electromagnetic induction heating is specifically as follows: Based on the material properties and dimensions of the workpiece (11) to be processed, an electromagnetic induction heating finite element model was established using ANSYS Workbench finite element simulation software. The output power P of the electromagnetic induction host (9) was changed. i The output frequency f of the electromagnetic induction host (9) i The output current I of the electromagnetic induction host (9) i The rotational speed n of the high-speed spindle (1) and the feed rate v of the high-speed spindle (1) r The cross-sectional area S of the auxiliary heating rod (17) is used to simulate the heat-affected zone of the workpiece (11). The depth value of the corresponding temperature is extracted from the simulation results. This temperature is the effective softening temperature of the material hardness of the workpiece (11). It is determined by consulting relevant literature or corresponding experiments. The established multiple regression equation is: In the formula, α is the coefficient of the regression formula; a1, a2, a3, a4, a5, and a6 are all parametric exponents.

6. The method for machining internal threads using electromagnetic induction heat treatment assisted by bending vibration according to claim 5, characterized in that: The output current of the electromagnetic induction host (9), the output frequency of the electromagnetic induction host (9), and the setting of the hole wall heating pretreatment time in step five are all obtained by simulating the heat-affected zone of the workpiece (11) in step one.

7. The method for machining internal threads using electromagnetic induction heat treatment assisted by bending vibration according to claim 4, characterized in that: The cutting simulation is specifically as follows: The electromagnetic induction heating assisted cutting finite element model is established based on the material properties and dimensions of the workpiece (11), the finishing turning tool (13), and the internal threading tool (14). The output amplitude A of the ultrasonic generator (3), the rotational speed n of the high-speed spindle (1), and the feed rate v of the high-speed spindle (1) are changed. r Back cut amount a p The second multiple linear regression equation was established by simulating the cutting force during machining: In the formula, β, λ, ε, and τ are all regression coefficients. This is the cutting force.

8. The method for machining internal threads using electromagnetic induction heat treatment assisted by bending vibration according to claim 4, characterized in that: In step three, the electromagnetic induction host (9) receives instructions from the bus control system and generates current to heat up the electromagnetic induction coil (10).

9. The method for machining internal threads using electromagnetic induction heat treatment assisted by bending vibration according to claim 4, characterized in that: In step six, the ultrasonic generator (3) receives instructions from the bus control system and generates an electrical signal to cause the piezoelectric transducer (15) to drive the internal thread cutting tool (14) to vibrate at high frequency.

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