Composite strengthening method and device for high-precision hole component

Abstract

The invention belongs to the technical field of precision machining, and particularly relates to a composite strengthening method and device for a high-precision hole component. The method comprises the steps that firstly, clamping and pretreatment are conducted; step 2, coating an absorption layer: coating the absorption layer by adopting a spraying process; thirdly, variable-frequency induction preheating is conducted, wherein the temperature of the whole workpiece to be machined is increased to the preheating temperature range; the current frequency is adjusted to a high frequency through a frequency conversion assembly, vortex is induced to be generated on the inner wall of the hole, and local deep heating is conducted on the inner wall of the hole; 5, plasma beam cladding strengthening is conducted, specifically, a plasma beam generation system is started, plasma beams are generated and used for conducting pretreatment on an area to be strengthened, and then the plasma beams are combined with variable-frequency induction heating to achieve strengthening of the inner wall of the hole; and step 6, processing post-treatment: after plasma beam cladding reinforcement is completed, rapid cooling and detection are carried out, and a processing site is cleaned to prepare for next processing. The energy utilization rate is high, and the strengthening effect is uniform.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision machining, and particularly relates to a method and device for composite strengthening of high-precision hole components. Background Art

[0002] In the fields of aerospace, high-end equipment manufacturing, etc., hole workpieces with hole diameters in the range of 3 - 50 mm have key application values. Typical representatives include fuel injection holes of aero-engines. As the core component of the engine fuel injection system, their surface properties directly affect the fuel atomization effect and combustion efficiency; there are also precision holes of hydraulic valve bodies, which are related to the pressure control accuracy and working stability of the hydraulic system. For these hole workpieces, this technology can achieve high-precision surface cladding. By cladding a specific alloy coating on the workpiece surface, its wear resistance and corrosion resistance are enhanced; an accurate quenching process is implemented to optimize the surface hardness and microstructure of the workpiece; at the same time, the internal structure is effectively regulated, the crystal structure is improved, and the comprehensive mechanical properties of the material are enhanced.

[0003] Existing hole workpiece strengthening technologies mostly adopt laser shock or single-frequency variable induction heating. These existing technologies have the following defects:

[0004] 1. Laser shock technology: The energy is significantly attenuated due to multiple reflections on the inner wall of the hole, resulting in insufficient depth of the strengthening layer and uneven residual stress distribution; affected by multiple reflections on the inner wall of the hole and the Fresnel absorption effect, the energy attenuation of laser shock technology is significant (about 50 - 70%), resulting in insufficient depth of the strengthening layer (usually <200 μm), and the distribution gradient of residual compressive stress is steep (±200 MPa / mm), which is prone to stress concentration.

[0005] 2. Variable frequency induction heating: The heating efficiency of the inner wall of the hole is low, and it is difficult to achieve local depth modification; the skin effect of single-frequency variable induction heating limits the heating depth (δ≈√(ρ / πμf), typical value 0.1 - 1 mm). Due to uneven magnetic field distribution on the inner wall of the hole, a cold and hot junction area is easily generated, and the grain refinement effect is poor (average grain size >5 μm).

[0006] 3. Traditional eddy current heating: Lack of coordination with external heating technologies, unable to optimize surface and internal properties simultaneously. Traditional eddy current heating lacks coordinated control with external heat sources, making it difficult to synchronously optimize surface cladding and internal recrystallization, and the energy utilization rate is low (<35%). Summary of the Invention

[0007] The purpose of the present invention is to provide a method for composite strengthening of high-precision hole components, which is used to solve the technical problems in the prior art that the energy attenuation is serious during the transmission of the plasma beam in the hole, it is impossible to achieve effective processing in the deep part of the hole, and it is extremely easy to cause uneven heating, affecting the consistency of processing quality.

[0008] The described high-precision hole component composite strengthening method includes the following steps:

[0009] Step 1, clamping and pre-treatment: Clamp and fix the workpiece to be machined, and perform equipment preparation and pre-treatment of the workpiece.

[0010] Step 2, absorption layer coating: On the surface area to be strengthened of the workpiece to be machined, coat the absorption layer by spraying process.

[0011] Step 3, variable-frequency induction preheating: Start the eddy current induction heating component and the variable-frequency component to raise the overall temperature of the workpiece to be machined to the preheating temperature range.

[0012] Step 4, eddy current deep heating: Adjust the current frequency to a higher frequency through the variable-frequency component, induce eddy currents on the inner wall of the hole, and perform local deep heating on the inner wall of the hole.

[0013] Step 5, plasma beam cladding strengthening: Start the plasma beam generating system to generate a plasma beam current, and use it to perform pre-treatment on the area to be strengthened, and then combine it with variable-frequency induction heating to achieve strengthening of the inner wall of the hole.

[0014] Step 6, post-processing after machining: After completing the plasma beam cladding strengthening, perform rapid cooling and detection, and clean the machining site to prepare for the next machining.

[0015] Preferably, Step 1 includes system control initialization, pre-treatment of the workpiece to be machined, and clamping of the workpiece to be machined; Step 5 includes starting and regulating the plasma beam generating system, plasma pre-treatment, and composite strengthening of the inner wall of the hole; Step 6 includes turning off the heating-related devices, rapid cooling and detection, and the post-processing process.

[0016] Preferably, in Step 2, the carbon black suspension after dispersion treatment is sprayed on the hole mouth and the inner wall of the hole to be strengthened. When spraying, control the spraying distance to be 10 - 15 cm, the spraying pressure to be 0.3 - 0.4 MPa. After spraying, make the thickness of the absorption layer evenly distributed on the surface area to be strengthened, and the thickness range is 50 - 100 μm.

[0017] Preferably, in Step 3, after starting the variable-frequency component, use the frequency synthesis technology to accurately set the frequency to 100 kHz, use the power adjustment module to stably output the power as 15 kW, and set the duty cycle to 50%; use an infrared thermal imager to monitor the workpiece temperature in real time, and through the closed-loop control system, accurately control the workpiece temperature within 300 - 600 °C, and control the temperature fluctuation within the range of ±10 °C.

[0018] Preferably, in step four, during the plasma pretreatment, the current frequency of the eddy current induction heating coil is adjusted to 300 kHz to induce a strong eddy current on the inner wall of the hole. The eddy current generates Joule heat on the inner wall of the hole to achieve local deep heating. According to the preset temperature value, the PID control algorithm is used to dynamically adjust the heating power to ensure that the temperature on the inner wall of the hole rapidly and stably rises to 800 - 1200 °C, and the temperature fluctuation is controlled within the range of ±10 °C.

[0019] Preferably, in step five, after the plasma generator operates, a voltage of 80 - 150 V is applied between the tungsten electrode and the fixed electrode and excited by a variable frequency oscillator, so that the passing inert gas is ionized to form a plasma beam current. At the same time, the cooling system in the plasma beam generating system is turned on, and the generator coolant is circulated through the shell, and the corresponding flow rate of the coolant is controlled at 5 - 10 L / min.

[0020] Preferably, in step five, after the plasma generator is started, by adjusting the direction of the nozzle, on the one hand, an inert gas is sprayed onto the inner wall of the hole to be strengthened for protection to form a stable flowing gas curtain protection layer on the inner wall of the hole; on the other hand, an arc voltage of 80 - 120 V is applied between the tungsten electrode and the fixed electrode to ionize the inert gas to generate a directional plasma beam current with a power density of 3 - 10 kW / cm 2 . During the pretreatment process, the plasma beam current is used to clean the surface of the inner wall of the hole at a scanning speed of 0.5 - 1.5 mm / s. After the pretreatment, the surface roughness Ra ≤ 0.4 μm.

[0021] Preferably, in step five, when performing composite strengthening on the inner wall of the hole, the arc voltage is set to 120 V, the flow rate of the inert gas is precisely adjusted to 15 L / min, the cross-sectional area of the arc is reduced through the nozzle and the energy is concentrated to form a high-energy jet; the nozzle is adjusted to the optimal spraying angle through the angle adjustment mechanism driven by the motor; the inner wall of the hole is subjected to cladding treatment at a scanning speed of 0.5 - 2 mm / s, and at the same time, the overlapping rate of the plasma beam current is controlled at 40%; during the cladding process, the energy distribution and composition changes of the plasma beam are monitored in real time by a spectral analyzer, and the parameters of the plasma generator are dynamically adjusted through the feedback control system.

[0022] The present invention also provides a composite strengthening device for high-precision hole components, which is applied to a composite strengthening method for high-precision hole components as described above. The composite strengthening device for high-precision hole components includes a plasma beam generation system, an eddy current induction heating component, a control module, a frequency conversion component, and a workbench. The workbench is provided with a fixed workpiece fixture for fixing the workpiece to be processed and a temperature detection device for detecting the temperature of the workpiece. The plasma generation system includes a gas supply device, a plasma generator, and a cooling system. The nozzle direction of the plasma generator can be adjusted so as to cover the inner wall of the hole at the optimal incident angle. The eddy current induction heating component includes an eddy current induction heating coil arranged around the inner wall of the hole and a coil mounting structure. The power supply is electrically connected to the eddy current induction heating coil through the frequency conversion component. The control module is used to control the frequency conversion current, the eddy current heating intensity, and the working parameters of the plasma beam generation system.

[0023] Preferably, a tungsten electrode, a nozzle, and a part of the cooling system are arranged in the housing of the plasma generator. The workbench is provided with a fixed electrode located below the fixed workpiece fixture. The gas supply device is communicated with the inner cavity of the housing through a gas flow controller. By adjusting the arc voltage between the tungsten electrode and the fixed electrode and the supplied gas flow rate, a directional plasma beam flow is formed on the inner wall of the hole to be strengthened.

[0024] The present invention has the following advantages:

[0025] High energy utilization rate: During the processing, the plasma beam directional heating technology plays a key role. The plasma gas is ionized by frequency conversion to form a transferred arc and a non-transferred arc. After being compressed by a carefully designed nozzle, a highly concentrated high-energy jet is formed. This directional plasma beam can accurately act on the area to be processed on the inner wall of the hole, greatly reducing the diffuse reflection and scattering losses of energy in the hole. Compared with the traditional laser processing where the energy in the hole is greatly attenuated (about 50 - 70%) due to multiple reflections, the plasma beam can achieve more efficient energy transfer. At the same time, the eddy current heating component is optimized for the deep modification of the inner wall of the hole. The eddy current induction heating coil wound with Litz wire effectively reduces the energy loss caused by the skin effect. According to the skin effect principle, when the frequency conversion current flows in a conductor, the current density will be concentrated on the surface of the conductor. The multi-strand fine wire structure of the Litz wire can reduce this effect, making the current more evenly distributed and improving the heating efficiency. By precisely adjusting the current frequency (adjustable from 100 - 500 kHz), the penetration depth and heating intensity of the eddy current on the inner wall of the hole can be accurately controlled, realizing efficient heating of a specific depth area on the inner wall of the hole and completing the deep modification. With the synergistic effect of the plasma beam directional heating and the eddy current heating, the comprehensive energy efficiency of this technology is increased by more than 40% compared with the traditional processing method.

[0026] Uniform strengthening effect: This technology adopts a unique dual-path heating method, namely external→internal frequency conversion induction and internal→external eddy current collaborative heating. The frequency conversion induction heating component generates an alternating magnetic field through an induction coil surrounding the workpiece. Utilizing the electromagnetic field-thermal field coupling effect, during this process, the entire workpiece is uniformly heated, and heat is transferred from the outside to the inside, establishing a relatively uniform initial temperature field inside the workpiece, effectively reducing the residual stress in subsequent processing. The eddy current induction heating coil is nested on the inner wall of the hole, and eddy currents are induced in the hole using a variable frequency magnetic field. Based on the skin effect and proximity effect, the inner wall of the hole instantaneously heats up to 800-1200°C. This heating method from the inside to the outside complements the frequency conversion induction heating. The dual-path heating enables the temperature field gradient of the hole wall to be ≤50°C / mm, a 70% reduction compared to the single heating method. The uniform temperature field distribution makes the tissue transformation and stress state of each part of the workpiece more consistent during processing. It can be determined by X-ray diffraction that the standard deviation of the residual stress distribution is <50 MPa, thus ensuring a high degree of consistency in the stress distribution inside and outside the hole and significantly improving the uniformity of the strengthening effect. Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of a composite strengthening device for a high-precision hole component in the present invention.

[0028] The reference numerals therein include: 1 industrial control computer, 2 control module, 3 rapid charge and discharge module, 4 workpiece to be processed with holes, 5 absorption layer, 6 fixture for fixing the workpiece, 7 frequency conversion component, 8 nozzle, 9 inert gas, 10 tungsten electrode, 11 fixed electrode, 12 coolant for the generator, 13 gas supply device, 14 transferred arc, 15 non-transferred arc, 16 gas flow controller, 17 eddy current induction heating coil. Detailed Embodiment

[0029] The following is a more detailed description of the specific embodiments of the present invention by referring to the drawings and describing the embodiments, so as to help those skilled in the art have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0030] As Figure 1As shown in the figure, the present invention provides a high-precision hole component composite strengthening device, including a plasma beam generating system, an eddy current induction heating component, a control module 2, a frequency conversion component 7, and a workbench. The workbench is provided with a fixed workpiece fixture 6 for fixing the workpiece to be processed and a temperature detection device for detecting the workpiece temperature. The plasma generating system includes a gas supply device 13, a plasma generator, and a cooling system. The nozzle 8 direction of the plasma generator can be adjusted to cover the inner wall of the hole at the best incident angle. The eddy current induction heating component includes an eddy current induction heating coil 17 arranged around the inner wall of the hole and a coil installation structure. The power supply is electrically connected to the eddy current induction heating coil 17 through the frequency conversion component 7. The control module 2 is used to control the frequency conversion current, the eddy current heating intensity, and the working parameters of the plasma beam generating system.

[0031] The frequency conversion component 7 is electrically connected to the fast charge and discharge module 3. Both the frequency conversion component 7 and the fast charge and discharge module 3 are connected to the control module 2. The frequency range controlled by the frequency conversion component 7 is 50Hz - 300kHz. The eddy current induction heating coil 17 adopts an annular structure nested on the inner wall of the hole, and the coil spacing can be adjusted. By controlling the current frequency conversion range of the eddy current induction heating coil 17, the frequency conversion component 7 can heat the workpiece to be processed through frequency conversion induction heating. During this process, the high-frequency surface layer of the workpiece matrix of the workpiece to be processed is rapidly preheated with a gradient through the electromagnetic field-thermal field coupling effect, with a heating rate ≥150°C / s, and a low-frequency internal steady-state heating, with good temperature gradient uniformity, effectively reducing the residual stress.

[0032] The eddy current induction heating coil 17 adopts a Litz wire winding method, which not only improves the heating efficiency but also reduces the coil heating and loss caused by the skin effect, reducing the probability of coil damage. The temperature detection device includes an infrared temperature measurement module, and the infrared temperature measurement module is embedded in the inner wall of the eddy current induction heating coil 17 to monitor the coil temperature and avoid failures caused by overheating.

[0033] The shell of the plasma generator is provided with a tungsten electrode 10, a nozzle 8, and a part of the cooling system. The workbench is provided with a fixed electrode 11 located below the fixed workpiece fixture 6. The gas supply device 13 is communicated with the inner cavity of the shell through a gas flow controller 16. By adjusting the arc voltage between the tungsten electrode 10 and the fixed electrode 11 and the supplied gas flow rate, a directional plasma beam flow is formed on the inner wall of the hole to be strengthened, removing the oxide layer on the inner wall surface of the hole and improving the adhesion of the absorption layer 5. The gas flow controller 16 adopts a mass flow controller (MFC) with an accuracy of ±0.1sccm, which can accurately control the gas flow rate, ensure the stable generation of plasma, and reduce the damage to the equipment caused by unstable gas flow rate.

[0034] An internal water-cooling channel integrated with the fixed workpiece fixture 6 is provided inside the hole of the workpiece to be machined, and circulating coolant flowing in a cycle is injected into the internal water-cooling channel through a cooling system. Thereby, the temperature rise of the machining area of the workpiece to be machined is controlled to prevent thermal damage.

[0035] The present invention also provides a method for composite strengthening of high-precision hole components, using the above-mentioned high-precision hole component composite strengthening device. This method includes the following steps.

[0036] Step 1: Clamping and pretreatment: Clamp and fix the hole workpiece 4 to be machined, and perform equipment preparation and workpiece pretreatment.

[0037] System control initialization: Start the control module 2 and the industrial control computer 1, run the corresponding control software, establish a connection between the industrial control computer 1 and the control module 2, set the initial control parameters on the control software interface, and perform equipment debugging. The control parameters include but are not limited to the working modes of each device, signal transmission frequencies, etc., to ensure that the entire machining system is in a standby state.

[0038] Pretreatment of the workpiece to be machined: It includes cleaning assistance for the surface of the workpiece to be machined (including the inner wall surface of the hole to be strengthened), for example, using organic solvents such as acetone or alcohol to remove impurities such as oil stains and dust on the surface. This can ensure good adhesion between the absorption layer 5 and the workpiece surface. Other pretreatment methods also include degreasing, pickling, and ultrasonic cleaning of the workpiece surface to remove oil stains, oxide layers, and impurities and enhance surface activity.

[0039] Clamping of the workpiece to be machined: Select a fixed workpiece fixture 6 suitable for the size and shape of the workpiece to be machined. The fixed workpiece fixture 6 needs to use high-precision positioning tools to ensure that the position accuracy of the hole workpiece 4 to be machined in the workpiece clamp reaches ±0.01 mm, avoiding the influence of clamping deviation on the subsequent machining accuracy. Turn on the internal water-cooling channel to achieve the circulating flow of the circulating coolant at a constant flow rate of 10 L / min. The circulating coolant is a mixture of deionized water and rust inhibitor additive. During the preparation stage, the temperature at the internal water-cooling channel is stabilized at 20 ± 2 °C through circulation to prepare for heat management during the machining process.

[0040] Step 2: Coating of the absorption layer 5: Coat the absorption layer 5 on the area to be strengthened on the surface of the workpiece to be machined by using a spraying process.

[0041] This step can adopt the high-voltage electrostatic spraying technology, and carbon black is selected as the absorption layer 5. The specific operation method is to spray the dispersed carbon black suspension on the orifice and inner wall of the hole to be strengthened. When spraying, control the spraying distance to be 10 - 15 cm, the spraying pressure to be 0.3 - 0.4 MPa. After spraying, make the thickness of the absorption layer 5 evenly distributed in the surface area to be strengthened, and the thickness range is 50 - 100 μm. After spraying, it can be detected by an optical interference thickness gauge to ensure that the thickness deviation is controlled within the range of ±10 μm, so that the plasma beam energy absorption rate can be increased to more than 90%.

[0042] Step Three: Variable-frequency induction preheating: Start the eddy current induction heating component and the variable-frequency component 7 to raise the overall temperature of the workpiece to be processed to the preheating temperature range.

[0043] After starting the variable-frequency component 7 in this step, use the frequency synthesis technology to accurately set the frequency to 100 kHz, and use the power adjustment module to stably output the power as 15 kW, and set the duty cycle to 50%. The variable-frequency current generated by the variable-frequency component 7 passes through the eddy current induction heating coil 17, and the latter heats the workpiece to be processed as a whole through the Joule heat effect. During this process, an alternating magnetic field is formed in space by the coil, and the alternating magnetic field penetrates the hole workpiece 4 to be processed, generating an induced electromotive force inside the workpiece, and then forming an induced current. The induced current generates Joule heat inside the workpiece, causing the overall temperature of the workpiece to rise evenly.

[0044] During this process, this step also uses an infrared thermal imager to monitor the temperature of the workpiece in real time. Through a closed-loop control system, the temperature of the workpiece is accurately controlled within the range of 300 - 600 °C, and the temperature fluctuation is controlled within the range of ±10 °C. This temperature is determined according to the workpiece material and experiments. In this embodiment, the temperature of the workpiece is accurately controlled at 450 ± 10 °C. At this preheating temperature, according to the thermo-mechanical property theory of metal materials, the yield strength of the workpiece matrix is reduced by 30%, creating conditions for reducing the accumulation of residual stress in subsequent processing.

[0045] Step Four: Eddy current deep heating: Adjust the current frequency to a higher frequency through the variable-frequency component 7 to induce eddy currents on the inner wall of the hole and perform local deep heating on the inner wall of the hole.

[0046] In the embodiment, the variable-frequency component 7 adjusts the current frequency of the eddy current induction heating coil 17 to 300 kHz. Based on the skin effect and proximity effect of electromagnetic induction, a powerful eddy current is induced on the inner wall of the hole by the formed variable-frequency alternating magnetic field. The eddy current generates Joule heat on the inner wall of the hole to achieve local deep heating. The variable-frequency component 7 maintains the heating power density stably at 8 kW / cm 2 . This step also uses a real-time infrared temperature measurement module embedded in the inner wall of the coil to collect the temperature data of the inner wall of the hole at a frequency of 10 times per second and feedback the data to the control module 2.

[0047] The control module 2 dynamically adjusts the heating power according to the preset temperature value by using the PID control algorithm to ensure that the temperature of the inner wall of the hole rapidly and stably rises to 800 - 1200 °C. This temperature is determined according to the workpiece material and experiments. In this embodiment, the temperature of the inner wall of the hole is accurately controlled at about 1000 °C, and the temperature fluctuation is controlled within the range of ±10 °C, which promotes the grain refinement and microstructure optimization in the area of the inner wall of the hole.

[0048] Step Five: Plasma beam cladding strengthening: Start the plasma beam generating system to generate a plasma beam, which is used for preprocessing the area to be strengthened, and then combined with variable-frequency induction heating to achieve the strengthening of the inner wall of the hole.

[0049] Start and regulate the plasma beam generating system: Under the control of the industrial control computer 1, the control module 2 and the fast charge and discharge module 3 work together to accurately regulate the magnitude of the current and the amplitude of the voltage applied to the plasma generator. After the plasma generator operates, a voltage of 80 - 150 V is applied between the tungsten electrode 10 and the fixed electrode 11, and it is excited by a variable-frequency oscillator, so that the inert gas 9 (such as an Ar-N2 mixture) passing through is ionized to form a plasma beam. The plasma beam is an arc, including a transferred arc 14 and a non-transferred arc 15. At the same time, turn on the cooling system in the plasma beam generating system, and circulate the generator coolant 12 in the shell. The generator coolant 12 uses deionized water or a special cooling medium, and the corresponding flow rate is controlled at 5 - 10 L / min. Start the cooling system to reduce the temperature of the tungsten electrode 10 in the shell and prevent it from being ablated at high temperatures, optimizing the stability and energy distribution characteristics of the plasma beam.

[0050] Plasma pretreatment: After turning on the plasma generator, by regulating the direction of the nozzle 8, on the one hand, inert gas 9 (such as an Ar-N2 mixture) is sprayed onto the inner wall of the hole to be strengthened for protection, that is, a convective gas curtain for protecting the surface of the workpiece is realized, and a stable flowing gas curtain protection layer is formed on the inner wall of the hole; on the other hand, by applying an arc voltage of 80 - 120 V between the tungsten electrode 10 and the fixed electrode 11, the inert gas 9 is ionized to generate a directional plasma beam with a power density of 3 - 10 kW / cm 2 ². During the pretreatment process, let the plasma beam clean the surface of the inner wall of the hole at a scanning speed of 0.5 - 1.5 mm / s. The plasma beam removes the oxide layer and impurities on the inner wall of the hole through thermal etching and ion bombardment, and at the same time makes the surface micro-region molten and activated, enhancing the adhesion of the absorption layer 5. After pretreatment, the surface roughness Ra ≤ 0.4 μm.

[0051] Composite strengthening of the inner wall of the hole: Set the arc voltage to 120V, use a mass flow controller (MFC) to precisely adjust the gas flow rate to 15L / min, and adjust the nozzle 8 to the optimal spraying angle through an angle adjustment mechanism driven by a motor. The generated arc passes through the carefully designed nozzle 8. Under the combined action of three effects: mechanical compression, thermal contraction, and magnetic contraction, the cross-sectional area of the arc is significantly reduced, and the energy is highly concentrated, thus forming a high-energy jet (i.e., a plasma beam). After the plasma beam is compressed by the nozzle 8 to form a high-energy jet, the inner wall of the hole is subjected to cladding treatment at a scanning speed of 0.5 - 2mm / s, and at the same time, the overlapping rate of the plasma beam is controlled to be 40%. In the strengthened area, the microstructure of the inner wall surface of the hole changes significantly, the grains are refined, and the dislocation density increases, forming a strengthened layer with good comprehensive properties. During the cladding process, use a spectral analyzer to monitor the energy distribution and composition changes of the plasma beam in real time, and dynamically adjust the parameters of the plasma generator through a feedback control system to ensure the formation of a uniform, dense, and well-bonded strengthened layer on the inner wall of the hole.

[0052] Step Six, Post-processing after Machining: After completing the plasma beam cladding strengthening, perform rapid cooling and detection, and clean the processing site to prepare for the next processing.

[0053] Turn off the heating-related devices: After completing the plasma beam cladding strengthening, immediately turn off the frequency conversion component 7 and the plasma beam generation system, and stop the heating actions of the eddy current induction heating coil 17 and the plasma generator. Note that the power of the frequency conversion component 7 should be gradually reduced until it is completely turned off to avoid adverse effects on the equipment and workpieces caused by electromagnetic interference generated by sudden power failure.

[0054] Rapid Cooling and Detection: Maintain the operation of each cooling system, and increase the flow rate of the circulating coolant to 20 - 30L / min, so that the workpiece is rapidly cooled to room temperature through the forced convection heat transfer of the cooling system. During the cooling process, use a thermal stress monitor to monitor the thermal stress changes inside the workpiece in real time to avoid workpiece deformation or cracking caused by excessive thermal stress due to too fast cooling. After cooling is completed, use a microhardness tester to perform multi-point hardness tests at different positions of the strengthened layer according to the Vickers hardness test standard (such as a load of 500gf), and take the average value of 3 tests at each position to comprehensively evaluate the hardness distribution of the strengthened layer. Use an X-ray diffractometer

[0055] Post-processing Process: After the temperature of the workpiece drops to room temperature, clean the processing site, remove the workpiece to be processed, clean the impurities and residues on the surface of the fixing clamp, and perform maintenance on the equipment to prepare for the next processing and end the entire strengthening operation process.

[0056] The above method has the advantages of high energy utilization rate and uniform strengthening effect. In addition, it also has the advantages of wide adaptability, strong material compatibility, environmental protection and high efficiency, high processing precision, good process expandability, etc. Details are as follows.

[0057] Wide adaptability: In terms of hardware design, the processing and strengthening device has a high degree of flexibility. The nozzle 8 of the multi-angle adjustable plasma beam processing component is designed to be multi-angle adjustable, and the deflection angle can be adjusted by ±45°. Through the motor drive and precise angle control mechanism, the angle of the nozzle 8 can be accurately adjusted according to the inner wall shape and processing requirements of workpieces with different hole diameters, ensuring that the plasma beam covers the inner wall of the hole at the best incident angle, and realizing uniform cladding and quenching treatment. At the same time, the eddy current induction heating coil 17 adopts an annular structure nested on the inner wall of the hole, and the coil spacing is adjustable. Through the mechanical adjustment device, the coil spacing can be quickly and accurately changed to adapt to the processing requirements of workpieces with different hole diameters (3 - 50 mm). Whether it is a precision hole workpiece with a small hole diameter or a general hole workpiece with a large hole diameter, by adjusting the angle of the nozzle 8 and the coil spacing, the consistency and stability of the heating and strengthening effects can be ensured, demonstrating a strong processing adaptability.

[0058] Environmental protection and high efficiency: In terms of environmental protection, the plasma gas (such as argon-nitrogen mixture) used in this technology has no pollution emissions during the processing. Argon has a stable chemical property and does not react with other substances in the processing environment, and no harmful by-products will be generated; nitrogen, after participating in the plasma formation process, finally escapes in a harmless form or combines with other substances, without causing pollution to the environment, meeting the requirements of modern manufacturing for green environmental protection. In terms of efficiency, compared with the traditional laser processing technology, the processing cycle of this technology is significantly shortened by 30%. There are serious problems such as severe energy attenuation and uneven heating in the hole during traditional laser processing, resulting in the need for multiple repeated operations during the processing to achieve the expected effect, consuming a lot of time. However, this technology can achieve the effect of one-time processing reaching or even exceeding multiple operations of traditional laser processing through plasma beam directional heating, dual-path collaborative heating, and the efficient control module 2 for real-time adjustment of processing parameters, effectively reducing the processing procedures and time, improving the production efficiency, and reducing the production cost.

[0059] High processing accuracy: The collaborative control module 2 integrates an industrial control computer 1, a rapid charge and discharge module 3, and a digital twin model, playing a key role. The digital twin model, based on physical principles such as Maxwell's equations and heat conduction equations, real-time simulates the electromagnetic-thermal-stress multi-physical field coupling situation during the processing. By comparing the simulated data with the actual monitored data, such as using a multi-channel data acquisition system to synchronously monitor the temperature inside the hole, the plasma beam power, and the eddy current density (response time < 1ms), when a deviation occurs, the control module 2 can quickly adjust the frequency conversion current, the eddy current heating intensity, and the plasma beam parameters. During plasma beam processing, the arc voltage and gas flow can be precisely controlled, so that the energy density of the plasma beam is stabilized at 3×10 4 -5×10 4 W / cm 2 , combined with the multi-angle adjustable nozzle 8 (deflection angle adjustable within ±45°), ensuring that the thickness uniformity error of the cladding layer is within ±10μm. During the frequency conversion induction and eddy current heating processes, the temperature control accuracy can reach ±10°C, effectively guaranteeing the processing accuracy and meeting the requirements of high-precision surface modification of hole-like components.

[0060] Strong material compatibility: The synergistic effect of frequency conversion induction heating, eddy current heating, and plasma beam processing enables this technology to have good compatibility with a variety of materials. For difficult-to-machine materials such as Inconel718 and Ti6Al4V, frequency conversion induction preheating can reduce the yield strength of the materials, creating favorable conditions for subsequent processing; eddy current deep heating can make the austenitization degree of the materials > 95%, refining the grains; plasma beam cladding can generate a nano-crystalline / amorphous composite strengthening layer on the surface, significantly improving the material properties. At the same time, this technology is also applicable to other metal materials, such as aluminum alloys and copper alloys. For different materials, personalized processing strengthening can be achieved by adjusting the heating parameters (such as frequency, power, heating time) and plasma beam parameters (such as power density, gas flow, arc voltage), expanding the application scope of the technology.

[0061] Low equipment maintenance cost: In terms of the equipment composition, the structural design of the frequency conversion induction heating component, the eddy current induction heating component, and the plasma beam processing component is reasonable and convenient for maintenance. For example, the eddy current induction heating coil 17 is wound with Litz wire, which not only improves the heating efficiency but also reduces the coil heating and loss caused by the skin effect, reducing the probability of coil damage. At the same time, the real-time infrared temperature measurement module is embedded in the inner wall of the coil, which can timely monitor the coil temperature and avoid faults caused by overheating. The plasma gas generator is equipped with a mass flow controller (MFC) with an accuracy of ±0.1sccm, which can precisely control the gas flow, ensure the stable generation of plasma, and reduce the damage to the equipment caused by unstable gas flow. In addition, a modular design is adopted between the components. When a certain component fails, it can be quickly disassembled and replaced, shortening the equipment downtime and reducing the maintenance cost.

[0062] Good process expandability: The process expandability of this processing and strengthening technology is good. Based on the existing process, more functions can be achieved by adjusting the processing parameters and adding auxiliary processes. The cladding-quenching composite process can be further optimized by adjusting the plasma beam scanning speed, overlapping rate, and cooling rate to prepare a strengthening layer with special microstructure and properties, such as a functionally gradient material strengthening layer, to meet the special requirements for the surface properties of hole workpieces under different working conditions. It can also be combined with other surface treatment technologies, such as electroless plating and electroplating, to further process the surface of the strengthening layer to improve the comprehensive properties of the hole workpiece, such as corrosion resistance and wear resistance. By changing the frequency and power distribution of variable-frequency induction and eddy current heating, selective strengthening of different depths and regions of the hole workpiece can be achieved, expanding the application scenarios of the process.

[0063] The present invention has been described by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made using the inventive concept and technical solution of the present invention, or the inventive concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A composite strengthening method for high-precision hole components, characterized in that: It includes the following steps: Step 1, clamping and pretreatment: Clamp and fix the workpiece with holes to be machined, and perform equipment preparation and workpiece pretreatment; Step 2, absorption layer coating: On the surface area to be strengthened of the workpiece to be machined, coat the absorption layer by spraying process; Step 3, variable-frequency induction preheating: Start the eddy current induction heating component and the variable-frequency component to raise the overall temperature of the workpiece to be machined to the preheating temperature range; Step 4, eddy current deep heating: Adjust the current frequency to a higher frequency through the variable-frequency component to induce eddy currents on the inner wall of the hole and perform local deep heating on the inner wall of the hole; Step 5, plasma beam cladding strengthening: Start the plasma beam generating system to generate a plasma beam current, and use it to perform pretreatment on the area to be strengthened, and then combine it with variable-frequency induction heating to achieve strengthening of the inner wall of the hole; Step 6, post-processing after machining: After completing the plasma beam cladding strengthening, perform rapid cooling and detection, and clean the machining site to prepare for the next machining.

2. The composite strengthening method for a high-precision hole component according to claim 1, wherein: Step 1 includes system control initialization, pretreatment of the workpiece to be machined, and clamping of the workpiece to be machined; Step 5 includes starting and regulating the plasma beam generating system, plasma pretreatment, and composite strengthening of the inner wall of the hole; Step 6 includes shutting down the heating-related devices, rapid cooling and detection, and the post-processing flow.

3. A composite strengthening method for a high-precision hole component according to claim 1, characterized in that: In Step 2, spray the carbon black suspension after dispersion treatment on the orifice and inner wall of the hole to be strengthened. When spraying, control the spraying distance to be 10 - 15 cm, the spraying pressure to be 0.3 - 0.4 MPa. After spraying, make the thickness of the absorption layer evenly distributed on the surface area to be strengthened, and the thickness range is 50 - 100 μm.

4. A composite strengthening method for a high-precision hole component according to claim 1, characterized in that: In Step 3, after starting the variable-frequency component, use the frequency synthesis technology to accurately set the frequency to 100 kHz, use the power adjustment module to stably output the power as 15 kW, and set the duty cycle to 50%; Use an infrared thermal imager to monitor the workpiece temperature in real time. Through the closed-loop control system, accurately control the workpiece temperature within 300 - 600 °C, and control the temperature fluctuation within the range of ±10 °C.

5. A composite strengthening method for a high-precision hole component according to claim 1, characterized in that: In Step 4, when performing plasma pretreatment, adjust the current frequency of the eddy current induction heating coil to 300 kHz to induce a strong eddy current on the inner wall of the hole. The eddy current generates Joule heat on the inner wall of the hole to achieve local deep heating; According to the preset temperature value, use the PID control algorithm to dynamically adjust the heating power to ensure that the temperature of the inner wall of the hole quickly and stably rises to 800 - 1200 °C, and control the temperature fluctuation within the range of ±10 °C.

6. A composite strengthening method for a high-precision hole component according to claim 2, characterized in that: In Step 5, after the plasma generator operates, apply a voltage of 80 - 150 V between the tungsten electrode and the fixed electrode, and excite it through a variable-frequency oscillator to ionize the passing inert gas to form a plasma beam current; At the same time, turn on the cooling system in the plasma beam generating system, circulate the generator coolant in the shell, and control the corresponding flow rate of the generator coolant to be 5 - 10 L / min.

7. A composite strengthening method for a high-precision hole component according to claim 2, characterized in that: In Step 5, after starting the plasma generator, by adjusting the direction of the nozzle, on the one hand, an inert gas is sprayed onto the inner wall of the hole to be strengthened for protection, forming a stable flowing gas curtain protection layer on the inner wall of the hole; on the other hand, by applying an arc voltage of 80 - 120 V between the tungsten electrode and the fixed electrode, the inert gas is ionized to generate a directional plasma beam with a power density of 3 - 10 kW / cm 2 . During the pretreatment process, the plasma beam is used to clean the surface of the inner wall of the hole at a scanning speed of 0.5 - 1.5 mm / s. After pretreatment, the surface roughness Ra ≤ 0.4 μm.

8. A composite strengthening method for a high-precision hole component according to claim 2, characterized in that: In Step 5, when performing composite strengthening on the inner wall of the hole, set the arc voltage to 120 V, precisely adjust the flow rate of the inert gas to 15 L / min, reduce the cross-sectional area of the arc and concentrate the energy through the nozzle to form a high-energy jet; adjust the nozzle to the optimal spraying angle through the angle adjustment mechanism driven by the motor; perform cladding treatment on the inner wall of the hole at a scanning speed of 0.5 - 2 mm / s, and at the same time control the overlapping rate of the plasma beam current to be 40%; during the cladding process, use a spectral analyzer to monitor the energy distribution and composition changes of the plasma beam in real time, and dynamically adjust the parameters of the plasma generator through the feedback control system.

9. A composite strengthening device for high-precision hole components, characterized in that: Applied to a composite strengthening method for a high-precision hole component according to any one of claims 1 - 8, and including a plasma beam generation system, an eddy current induction heating component, a control module, a frequency conversion component, and a workbench. The workbench is provided with a fixed workpiece fixture for fixing the workpiece to be processed and a temperature detection device for detecting the workpiece temperature. The plasma generation system includes a gas supply device, a plasma generator, and a cooling system. The nozzle direction of the plasma generator can be adjusted so as to cover the inner wall of the hole at the optimal incident angle. The eddy current induction heating component includes an eddy current induction heating coil arranged around the inner wall of the hole and a coil mounting structure. The power supply is electrically connected to the eddy current induction heating coil through the frequency conversion component. The control module is used to control the frequency conversion current, the eddy current heating intensity, and the working parameters of the plasma beam generation system.

10. A high-precision hole component composite strengthening device according to claim 9, characterized in that: A tungsten electrode, a nozzle, and a part of the cooling system are arranged in the housing of the plasma generator. The workbench is provided with a fixed electrode located under the fixed workpiece fixture. The gas supply device is communicated with the inner cavity of the housing through a gas flow controller; by adjusting the arc voltage between the tungsten electrode and the fixed electrode and the supplied gas flow rate, a directional plasma beam current is formed on the inner wall of the hole to be strengthened.

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