Device and machining method for ultrasonic vibration reinforced electric spark electrolytic machining of composite material

Abstract

The device comprises a pulse power supply, the negative electrode and the positive electrode of the pulse power supply are connected with a metal-based diamond composite material and a tool electrode respectively, the tool electrode or the metal-based diamond composite material is provided with an ultrasonic vibrator, and the ultrasonic vibrator is connected with the pulse power supply. And the ultrasonic vibrator is provided with an ultrasonic generator. According to the method, the distribution density of bubbles on the surface of the diamond is improved through the cathode surface hydrogen evolution process in the electrolysis process, controllable conditions are created for the ultrasonic cavitation effect, a tool electrode material is sputtered to the surface layer of the diamond due to electric spark discharge, a catalyst is provided, and the conversion efficiency of diamond graphitization is improved by integrating the two conditions. The surface layer of the diamond has electrical conductivity after being graphitized, so that the diamond has discharge machinability without the operation of plating metal and the like, and the implementation mode is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of material processing, and in particular to an apparatus and a processing method for ultrasonic vibration enhanced electro-discharge electrochemical machining of composites. Background Art

[0002] Particle reinforced metal matrix composites are a new type of composite material prepared by a certain process with metal as the matrix and ceramic particles as the reinforcing phase, such as diamond particles. However, since the metal matrix diamond composites are a kind of heterogeneous composite materials and the particle reinforcing phase has a high hardness, traditional machining methods, such as cutting and grinding, have serious tool wear problems and it is difficult to ensure the dimensional accuracy of parts.

[0003] Electro-discharge machining technology uses electro-thermal energy to erode materials. When voltages are applied to both ends of the workpiece and the tool electrode and the working medium is broken down, the energy density of the plasma in the formed discharge channel is extremely high, and the temperature in the central region can reach 10,000 K. In theory, any conductive material can be eroded.

[0004] However, the diamond particle reinforcing phase is not conductive. After the metal matrix is eroded by discharge, the exposed diamond particles hinder the feeding of the tool electrode for electro-discharge machining, and the machining stability is poor. When the tool electrode is a wire electrode, there is a serious wire bending phenomenon during the machining process. Not only is continuous machining difficult to sustain, but there is also a serious risk of wire breakage.

[0005] As the volume fraction of the diamond reinforcing phase increases, the machinability of the metal matrix diamond composites becomes worse. Only relying on the removal form of particle reinforcing phase peeling, the surface quality of the side wall surface or the cut surface after discharge machining is poor, and it is difficult to control the dimensional accuracy.

[0006] Electrochemical machining is based on an electrochemical reaction. The anode material will be removed in the form of ions. After the material around the particle reinforcing phase is eroded by discharge, the particle reinforcing phase is removed in the form of peeling. There are pits on the machined surface, and the distribution of the pits is affected by the volume fraction of the particle reinforcing phase. The larger the volume fraction, the denser the pits, and the quality of the machined surface is poor.

[0007] The cavitation effect of traditional ultrasonic vibration has poor randomness and it is difficult to efficiently promote the carbonization process of diamond. Ultrasonic vibration assisted electro-discharge machining mainly uses ultrasonic vibration to promote chip removal in the machining area.

[0008] Existing machining technologies are difficult to ensure machining efficiency, surface quality and machining accuracy, which hinders the engineering application of such materials. Based on the above analysis, an apparatus and a processing method for ultrasonic vibration enhanced electro-discharge electrochemical machining of composites are proposed. Summary of the Invention

[0009] The purpose of the present invention is to provide a device and a processing method for ultrasonic vibration enhanced electro-discharge electrochemical machining of composites, so as to solve the problems raised in the above-mentioned background technology.

[0010] To achieve the above purpose, the present invention provides the following technical solution: A device for ultrasonic vibration enhanced electro-discharge electrochemical machining of composites, including a pulse power supply, the negative electrode and the positive electrode of the pulse power supply are respectively connected to a metal matrix diamond composite and a tool electrode, and an ultrasonic vibrator is provided on the tool electrode or the metal matrix diamond composite, and the ultrasonic vibrator is equipped with an ultrasonic generator.

[0011] Preferably: When the tool electrode is a block electrode or a cylindrical electrode, the ultrasonic vibrator is connected to the tool electrode.

[0012] Preferably: When the tool electrode is an electrode wire, a wire guide for guiding is provided on the electrode wire, and the ultrasonic vibrator is connected to the wire guide.

[0013] Preferably: The material of the tool electrode is iron or an iron-containing alloy.

[0014] Preferably: The output frequency of the ultrasonic generator is 20 - 40 KHz, the power is 10 - 100 W, and the number of ultrasonic vibrators is 1 - 5.

[0015] The processing method using the device for ultrasonic vibration enhanced electro-discharge electrochemical machining of composites according to any one of the above 1 - 5 includes the following steps:

[0016] S1, Spray the working fluid into the processing area, or immerse the metal matrix diamond composite and the tool electrode in the working fluid;

[0017] S2, Turn on the pulse power supply, adjust the distance between the metal matrix diamond composite and the tool electrode until electric spark discharge occurs, turn on the ultrasonic generator, and start automatic processing;

[0018] S3, The metal matrix of the metal matrix diamond composite is eroded by electric spark discharge, the diamond particles are exposed on the diamond surface layer, hydrogen bubbles are precipitated on the surface of the metal matrix diamond composite, and adhere to the surface of the diamond surface layer;

[0019] S4, The ultrasonic generator makes the tool electrode vibrate at a set frequency, move away from or close to the metal matrix diamond composite from the equilibrium position, alternating negative pressure and high pressure appear in the processing area, the hydrogen bubbles expand under negative pressure, and the hydrogen bubbles are compressed or even collapsed under high pressure. This process generates ultrasonic cavitation effect, accompanied by high temperature and water hammer effect, continuously acting on the diamond surface layer, turning the diamond surface layer into a conductive carbonized layer, and the material of the tool electrode splashed onto the diamond surface layer acts as a catalyst, which can catalyze the formation of the carbonized layer;

[0020] S5. A conductive layer is formed by the carbonized layer and the metal matrix. The carbonized layer is bombarded by electric spark discharge, causing the diamond particles to be micro-crushed and removed.

[0021] S6. Steps S3 to S5 are cycled, and the metal matrix diamond composite is continuously removed to complete the processing of the metal matrix diamond composite.

[0022] Preferably, in step S2, electric spark discharge occurs during the pulse width of the pulse power supply, and hydrogen bubbles are precipitated due to electrolysis during the pulse interval.

[0023] Preferably, the pulse width voltage amplitude is 100 - 200V, the pulse width duration is 0.5 - 200 μs, the pulse interval voltage does not exceed 30V, and the pulse interval duration is 0.1 - 10 times that of the pulse width duration.

[0024] Preferably, in step S1, the conductivity of the working fluid is 1 - 15 mS / cm, and the injection pressure of the working fluid is 0.1 - 1 MPa.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: In the present invention, the distribution density of bubbles on the diamond surface is increased by the hydrogen evolution process on the cathode surface during electrolysis, creating controllable conditions for the ultrasonic cavitation effect. The tool electrode material is sputtered onto the diamond surface layer due to electric spark discharge, providing a catalyst. Combining the above two conditions, the conversion efficiency of diamond graphitization is improved. After the diamond surface layer is graphitized, it has conductivity, and there is no need to make it dischargeable through operations such as metal plating, and the implementation method is simple. The diamond particles are micro-crushed by electric spark discharge, the gap consistency in the processing area is good, the discharge stability is high, and high-efficiency, high-surface-quality, and high-processing-precision processing can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a structural schematic diagram of the present invention;

[0027] Figure 2 is a voltage and current waveform diagram output by the pulse power supply of the present invention;

[0028] Figure 3 is a structural schematic diagram of the electric spark forming machining of the present invention;

[0029] Figure 4 is a structural schematic diagram of the electric spark wire cutting machining of the present invention.

[0030] In the figure: 1. Metal matrix diamond composite; 2. Tool electrode; 3. Diamond particles; 4. Carbonized layer; 5. Hydrogen bubbles; 6. Electric spark discharge; 7. Working fluid; 8. Ultrasonic oscillator; 9. Ultrasonic generator; 10. Ultrasonic cavitation effect; 11. Diamond surface layer; 12. Pulse power supply; 13. Catalyst; 14. Wire storage barrel; 15. Wire guide; 16. Spindle chuck; 17. Workbench. Detailed implementation mode

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0032] Please refer to Figures 1-4 , the present invention provides a technical solution: a device for ultrasonic vibration enhanced electro-discharge electrolytic machining of composite materials, as Figure 1 shown: It includes a pulse power supply 12, the negative and positive electrodes of the pulse power supply 12 are respectively connected to a metal matrix diamond composite material 1 and a tool electrode 2, and the material of the tool electrode 2 is iron or an iron-containing alloy. An ultrasonic vibrator 8 is provided on the tool electrode 2 or the metal matrix diamond composite material 1, the ultrasonic vibrator 8 is equipped with an ultrasonic generator 9, the output frequency of the ultrasonic generator 9 is 20 - 40 KHz, the power is 10 - 100 W, and the number of ultrasonic vibrators 8 is 1 - 5.

[0033] As Figure 3 shown: When the tool electrode 2 is a block electrode or a cylindrical electrode, the metal matrix diamond composite material 1 is fixed on the workbench 17 of the electro-discharge forming machine tool. When the tool electrode 2 is a block, it is used for cavity machining, and when the tool electrode 2 is a cylinder, it is used for hole machining. The tool electrode 2 is clamped on the spindle chuck 16. Connect the ultrasonic vibrator 8 with the ultrasonic generator 9 and cement it on the side of the tool electrode 2.

[0034] The waveform of the pulse power supply 12 is as Figure 2 shown, the pulse width can perform electro-discharge 6, and the pulse interval can perform electrolysis. The positive and negative electrodes of the pulse power supply 12 are respectively connected to the tool electrode 2 and the metal matrix diamond composite material 1. Turn on the water pump to spray the working fluid 7 into the machining area between the electrodes, and turn on the ultrasonic generator 9.

[0035] When everything is ready, turn on the pulse power supply 12, slowly adjust the distance between the tool electrode 2 and the metal matrix diamond composite material 1 until electro-discharge 6 appears, and then turn on the automatic feed switch of the machine tool workbench 17. When performing cavity machining, the workbench 17 feeds tangentially along the metal matrix diamond composite material, and the tangential feed speed V1 is 2 - 200 μm / s, and the single-layer material removal thickness is 5 - 50 μm.

[0036] When performing hole machining, the tool electrode 2 feeds along the normal direction of the metal matrix diamond composite material 1, and the feed speed V2 is 2 - 200 μm / s.

[0037] As Figure 4As shown: When the tool electrode 2 is an electrode wire, the metal-based diamond composite 1 is fixed on the workbench 17 of the wire electrical discharge machining machine tool. The electrode wire is wound around the wire storage barrel 14, and the effective winding length is not less than 1 / 2 of the length of the wire storage barrel 14. The wire guide 15 guides the position of the electrode wire. The ultrasonic oscillator 8 is connected to the ultrasonic generator 9 and cemented to the side of the wire guide 15.

[0038] The waveform of the pulse power supply 12 is as Figure 2 shown. The pulse width can be used for electrical discharge machining 6, and the pulse interval can be used for electrolysis. The positive and negative electrodes of the pulse power supply 12 are respectively connected to the electrode wire and the metal-based diamond composite 1. Turn on the water pump to spray the working fluid 7 into the machining area between the electrodes. Turn on the ultrasonic generator 9 and the wire movement switch of the wire storage barrel 14 to make the electrode wire reciprocate along the tangential direction of the metal-based composite at a speed of V1, where V1 is 0.1 - 12 m / s.

[0039] When everything is ready, turn on the pulse power supply 12, slowly adjust the distance between the electrode wire and the metal-based diamond composite 1 until electrical discharge machining 6 occurs, and then turn on the automatic feed switch of the machine tool workbench 17 to make the workbench 17 feed along the normal direction of the metal-based diamond composite at a speed of V2, where V2 is 2 - 200 μm / s.

[0040] A processing method for an ultrasonic vibration enhanced electrical discharge electrolysis machining composite device includes the following steps: First, connect the positive electrode of the pulse power supply 12 to the tool electrode 2 and the negative electrode to the metal-based diamond composite 1. When the tool electrode 2 is a block electrode or a cylindrical electrode for electrical discharge forming machining, the ultrasonic oscillator 8 is cemented to the tool electrode 2. When the tool electrode 2 is an electrode wire for wire electrical discharge machining, the ultrasonic oscillator 8 is cemented to the wire guide 15, and the ultrasonic oscillator 8 is equipped with an ultrasonic generator 9.

[0041] Then spray the working fluid 7 into the machining area, or immerse the metal-based diamond composite 1 and the tool electrode 2 in the working fluid 7. The conductivity of the working fluid 7 is 1 - 15 mS / cm, and the spraying pressure of the working fluid 7 is 0.1 - 1 MPa.

[0042] After that, turn on the pulse power supply 12. The pulse power supply 12 performs electrical discharge machining 6 during the pulse width period. The pulse width voltage amplitude is 100 - 200 V, and the pulse width duration is 0.5 - 200 μs. Electrolysis reaction occurs during the pulse interval, so hydrogen bubbles 5 are precipitated due to the electrolysis effect. The pulse interval voltage does not exceed 30 V, and the pulse interval duration is 0.1 - 10 times the pulse width duration.

[0043] Then, adjust the distance between the metal matrix diamond composite 1 and the tool electrode 2 until the electric spark discharge 6 appears. Turn on the ultrasonic generator 9 and start the automatic machining. The metal matrix of the metal matrix diamond composite 1 is eroded by the electric spark discharge 6, and the diamond particles 3 are exposed on the diamond surface layer 11. Hydrogen bubbles 5 are precipitated on the surface of the metal matrix diamond composite 1 due to the electrolysis effect and adhere to the surface of the diamond surface layer 11.

[0044] Subsequently, the ultrasonic generator 9 vibrates the tool electrode 2 at a set frequency, moving away from or approaching the metal matrix diamond composite 1 from the equilibrium position. Alternating negative and positive pressures appear in the machining area. The hydrogen bubbles 5 expand under negative pressure and are compressed or even collapsed under positive pressure. During this process, the ultrasonic cavitation effect 10 is generated, accompanied by high temperature and water hammer effect, continuously acting on the diamond surface layer 11, converting the diamond surface layer 11 into a conductive carbide layer 4. The material of the tool electrode 2 splashed onto the diamond surface layer 11 acts as a catalyst 13, which can catalyze the formation of the carbide layer 4.

[0045] The carbide layer 4 and the metal matrix form a conductive layer. The electric spark discharge 6 bombards the carbide layer 4, causing the diamond particles 3 to be slightly broken and removed. Repeat the above steps, and the metal matrix diamond composite 1 is continuously removed to complete the machining of the metal matrix diamond composite 1.

[0046] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An apparatus for ultrasonic vibration enhanced electro-discharge electrolytic machining of composites, comprising a pulse power supply (12), characterized in that: The negative electrode and the positive electrode of the pulse power supply (12) are respectively connected to a metal-based diamond composite material (1) and a tool electrode (2). An ultrasonic oscillator (8) is provided on the tool electrode (2) or the metal-based diamond composite material (1), and the ultrasonic oscillator (8) is equipped with an ultrasonic generator (9).

2. The device for ultrasonic vibration enhanced electro-discharge electrolytic machining of composite materials according to claim 1, characterized in that: When the tool electrode (2) is a block-shaped electrode or a cylindrical electrode, the ultrasonic oscillator (8) is connected to the tool electrode (2).

3. The device for ultrasonic vibration enhanced electro-discharge electrolytic machining of composite materials according to claim 1, wherein: When the tool electrode (2) is an electrode wire, a wire guide (15) for guiding is provided on the electrode wire, and the ultrasonic oscillator (8) is connected to the wire guide (15).

4. An apparatus for ultrasonic vibration enhanced electro-discharge electrochemical machining of composite materials according to claim 1, characterized in that: The material of the tool electrode (2) is iron or an iron-containing alloy.

5. The device for ultrasonic vibration enhanced electro-discharge electrochemical machining of composites according to claim 1, characterized in that: The output frequency of the ultrasonic generator (9) is 20 - 40 KHz, the power is 10 - 100 W, and the number of the ultrasonic oscillators (8) is 1 - 5.

6. The machining method of a composite material machining device for ultrasonic vibration enhanced electro-discharge electrolytic machining according to any one of claims 1-5, characterized in that, It includes the following steps: S1. Spray the working fluid (7) into the machining area, or immerse the metal-based diamond composite material (1) and the tool electrode (2) in the working fluid (7). S2. Turn on the pulse power supply (12), adjust the distance between the metal-based diamond composite material (1) and the tool electrode (2) until electric spark discharge (6) occurs, turn on the ultrasonic generator (9), and start automatic machining. S3. The metal matrix of the metal-based diamond composite material (1) is eroded by the electric spark discharge (6), the diamond particles (3) expose the diamond surface layer (11), hydrogen bubbles (5) precipitate on the surface of the metal-based diamond composite material (1) and adhere to the surface of the diamond surface layer (11). S4. The ultrasonic generator (9) vibrates the tool electrode (2) at a set frequency, moving away from or approaching the metal-based diamond composite material (1) from the equilibrium position. Alternating negative pressure and high pressure appear in the machining area. The hydrogen bubbles (5) expand under negative pressure and are compressed or even collapsed under high pressure. This process generates an ultrasonic cavitation effect (10), accompanied by high temperature and a water hammer effect, continuously acting on the diamond surface layer (11), turning the diamond surface layer (11) into a conductive carbonized layer (4). The material of the tool electrode (2) splashed onto the diamond surface layer (11) acts as a catalyst (13), which can catalyze the formation of the carbonized layer (4). S5. The carbonized layer (4) and the metal matrix form a conductive layer, and the electric spark discharge (6) bombards the carbonized layer (4), causing the diamond particles (3) to be micro-crushed and removed. S6. Repeat steps S3 to S5, and the metal-based diamond composite material (1) is continuously removed to achieve the machining of the metal-based diamond composite material (1).

7. The processing method of a composite material device for ultrasonic vibration enhanced electro-discharge electrolytic machining according to claim 6, characterized in that: In step S2, electric spark discharge (6) occurs during the pulse width of the pulse power supply (12), and an electrolysis reaction occurs during the pulse interval, and hydrogen bubbles (5) precipitate due to the electrolysis effect at the same time.

8. The processing method of a composite material processing device for ultrasonic vibration enhanced electro-discharge electrochemical machining according to claim 7, characterized in that: The pulse width voltage amplitude is 100 - 200 V, the pulse width duration is 0.5 - 200 μs, the pulse interval voltage does not exceed 30 V, and the pulse interval duration is 0.1 - 10 times the pulse width duration.

9. The machining method of a composite material device for ultrasonic vibration enhanced electro-discharge electrochemical machining according to claim 6, characterized in that: In step S1, the conductivity of the working fluid (7) is 1 - 15 mS / cm, and the spraying pressure of the working fluid (7) is 0.1 - 1 MPa.

Images