Porous electrode forming method for electric spark machining of deep micro holes

Abstract

The invention provides a porous electrode forming method for electric spark machining of deep micro holes, and belongs to the technical field of non-traditional machining, the diameter of the prepared porous electrode can reach 100 microns or below through the technology of suspension preparation, low-temperature freezing, freeze drying, impurity removal, high-temperature sintering and electric spark grinding, and the diameter of the prepared porous electrode can reach 100 microns or below. The porous electrode is of a micro porous structure constructed by nano-particles, circulation of working fluid in the electrode can be achieved, the working fluid with a certain speed and pressure is conveyed to the depth of the small holes, accumulation of electric corrosion products is slowed down, the machining precision and machining efficiency of the small holes are improved, and the service life of the electrode is prolonged. And different degrees of electric spark grinding treatment can be carried out according to machining requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of special processing, and in particular relates to a porous electrode forming method for electric spark processing of deep micro holes. Background Art

[0002] With the continuous improvement of mechanical production technology requirements, mechanical products also tend to be miniaturized and precise. In the face of the problem of processing tiny holes (holes with a diameter of less than 0.3mm are usually called microholes, and holes with a diameter of 0.3mm to 1mm are called small holes) of precision parts, EDM micro-hole processing technology has gradually become the preferred method. Compared with mechanical drilling, EDM micro-hole processing does not have problems such as stress and material deformation. It has high processing accuracy and is not limited by cutting conditions such as the hardness and strength of the workpiece material. The hole depth can be controlled by adjusting electrical parameters. It is especially suitable for micro-hole processing of parts with thin-wall features and difficult-to-process materials.

[0003] At present, in the application of EDM micro-hole processing technology for high-precision deep and micro-hole processing, there are many problems such as the difficulty in effectively discharging the electro-etched particles generated by the discharge and low processing efficiency. Failure to discharge the electro-etched particles in time will also lead to abnormal discharge between the electrode and the hole wall, causing problems such as reduced micro-hole surface quality and dimensional accuracy. Although the porous electrode for EDM micro-hole processing can also achieve the internal flushing processing method, the preparation of the porous electrode is extremely difficult due to the extremely small diameter of the porous electrode used for EDM deep micro-holes.

[0004] Therefore, there is an urgent need for a porous electrode forming method that can be used for electrospark machining of deep and micro holes to solve the above technical problems. Summary of the invention

[0005] In order to solve the shortcomings and deficiencies of the prior art, a porous electrode forming method for electrospark machining of deep micro-holes is provided, thereby solving the problem that the existing porous motors are extremely difficult to prepare due to their extremely small diameter.

[0006] In order to achieve the purpose of the present invention, a porous electrode forming method for electrospark machining of deep micro-holes is provided, and the specific steps are as follows:

[0007] Step 1, preparation of suspension: 20 vol.%-40 vol.% of nanoparticles, 1 vol.% of dispersion stabilizer, and 1 vol.% of binder are mixed together, and deionized water is added and stirred for 24 hours to obtain a suspension;

[0008] The nanoparticles are connected together by a binder during the low-temperature freezing process and the high-temperature sintering process to form a microporous structure. The mass fraction of the nanoparticles will affect the microporous structure: within a certain range, as the mass fraction of the nanoparticles increases, the porosity of the micropores will decrease.

[0009] Since the dispersion stabilizer has good water absorption, the mass fraction of the dispersion stabilizer cannot be too high, otherwise the suspension will become colloidal. In addition, too much dispersion stabilizer will make it difficult to remove during the high-temperature sintering step, and will remain in the microporous structure, reducing the effective micropore area of ​​the microporous structure. At the same time, too little dispersion stabilizer cannot prevent the nanoparticles from settling.

[0010] The binder can bind the nanoparticles together during the freezing process and high-temperature sintering process, thus improving the strength of the microporous structure;

[0011] Deionized water is easy to solidify and easy to sublime after solidification, which facilitates subsequent low-temperature freezing and freeze-drying.

[0012] Step 2, low temperature freezing: injecting the suspension obtained in step 1 into a capillary metal tube and then placing it in a low temperature environment of -50°C to -10°C for freezing;

[0013] The lower the ambient temperature, the faster the freezing speed, and the thickness of the microporous structure and the equivalent diameter of a single micropore decrease. Conversely, when freezing is carried out at a higher ambient temperature, the thickness of the micropore layer and the diameter of a single micropore increase.

[0014] Step 3, freeze drying: placing the capillary metal tube frozen in step 2 in a vacuum environment at -70°C for 48 hours to allow the ice crystals in the capillary metal tube to sublime;

[0015] The purpose of the freeze-drying step is to sublime the ice crystals in the capillary metal tube, and the structure left in the gaps between the ice crystals is a microscopic porous structure constructed by nanoparticles.

[0016] Step 4, impurity removal: the capillary metal tube obtained in step 3 is placed in a vacuum or inert gas environment at 400°C for 1 hour to thermally decompose the excess dispersion stabilizer and binder;

[0017] Step 5, high temperature sintering: sintering the capillary metal tube obtained in step 4 at a certain temperature T in a vacuum or inert gas environment for 6-12 hours to obtain a porous electrode blank;

[0018] Step 6: Electric spark grinding: The porous electrode blank obtained in step 5 is subjected to electric spark grinding to obtain a porous electrode.

[0019] As a further improvement of the above solution, the material used for the nanoparticles in step 1 is any one of copper, tungsten, tungsten carbide and graphite.

[0020] As a further improvement of the above scheme, the dispersion stabilizer in step one includes any one or more of sodium carboxymethyl cellulose, sodium polyacrylate, polypropylene alcohol, polyvinyl alcohol, and polyethylene glycol.

[0021] As a further improvement of the above solution, the binder in step 1 is poly (2-ethyl-2-oxazoline).

[0022] As a further improvement of the above scheme, a magnetic stirrer is used for stirring in step 1.

[0023] As a further improvement of the above solution, the capillary metal tube in step 2 is a copper tube or a tungsten tube.

[0024] As a further improvement of the above solution, the temperature T in step five is 40%-80% of the melting point of the nano-particle material.

[0025] As a further improvement of the above scheme, the microscopic porous structure in the porous electrode blank obtained in step five is in the form of anisotropic lamellar, isotropic lamellar, grid or radial.

[0026] As a further improvement of the above solution, the diameter of the porous electrode obtained in step six is ​​≤100 μm.

[0027] The beneficial effects of the present invention are:

[0028] Compared with the prior art, the present invention provides a porous electrode forming method for electrospark machining of deep micro-holes. The diameter of the prepared porous electrode can reach less than 100 μm, and the porous electrode has a microscopic porous structure constructed of nanoparticles, which can realize the circulation of working fluid inside the electrode, and transport the working fluid with a certain speed and pressure to the deep of the small hole, slowing down the accumulation of electro-corrosion products, and improving the machining accuracy and efficiency of the micro-holes. Different degrees of electrospark grinding can be performed according to the machining requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of preparing a porous electrode according to the present invention;

[0030] Figure 2 A schematic diagram of the morphology of the porous electrode prepared in the present invention;

[0031] Figure 3 A microstructure diagram of a cross section of a porous electrode prepared in the present invention;

[0032] Figure 4 for Figure 3 A magnified view of middle;

[0033] Figure 5 This is a microstructure diagram of the longitudinal section of the porous electrode prepared in the present invention. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings:

[0035] Embodiment 1

[0036] according to Figure 1 As shown, the present invention provides a porous electrode forming method for electrospark machining deep micro-holes, and the specific steps are as follows:

[0037] Step 1, preparation of suspension: 20 vol.% of copper nanoparticles, 1 vol.% of dispersion stabilizer, and 1 vol.% of poly (2-ethyl-2-oxazoline) are mixed together, and deionized water is added and stirred with a magnetic stirrer for 24 hours to obtain a suspension. The dispersion stabilizer is selected from any one or more of sodium carboxymethyl cellulose, sodium polyacrylate, polypropylene alcohol, polyvinyl alcohol, and polyethylene glycol.

[0038] Step 2, low-temperature freezing: inject the suspension obtained in step 1 into a capillary metal tube and then place it in a low-temperature environment of -50°C for freezing; the capillary metal tube can be a copper tube or a tungsten tube.

[0039] Step 3, freeze drying: placing the capillary metal tube frozen in step 2 in a vacuum environment at -70°C for 48 hours to allow the ice crystals in the capillary metal tube to sublime;

[0040] Step 4, impurity removal: the capillary metal tube obtained in step 3 is placed in a vacuum or inert gas environment at 400°C for 1 hour to thermally decompose the excess dispersion stabilizer and binder;

[0041] Step 5, high temperature sintering: the capillary metal tube obtained in step 4 is sintered at 430°C, 758°C and 870°C respectively for 6 hours in a vacuum or inert gas environment to obtain a porous electrode blank. The microscopic porous structure of the obtained porous electrode blank is anisotropic lamellar, isotropic lamellar, grid-like, and radial.

[0042] Step 6, electric spark grinding: the porous electrode blank obtained in step 5 is subjected to electric spark grinding to obtain a porous electrode, wherein the diameter of the obtained porous electrode is ≤ 100 μm.

[0043] Embodiment 2

[0044] according to Figure 1 As shown, the present invention provides a porous electrode forming method for electrospark machining deep micro-holes, and the specific steps are as follows:

[0045] Step 1, preparation of suspension: 30 vol.% of tungsten nanoparticles, 1 vol.% of dispersion stabilizer, and 1 vol.% of poly (2-ethyl-2-oxazoline) are mixed together, and deionized water is added and stirred with a magnetic stirrer for 24 hours to obtain a suspension. The dispersion stabilizer includes any one or more of sodium carboxymethyl cellulose, sodium polyacrylate, polypropylene alcohol, polyvinyl alcohol, and polyethylene glycol.

[0046] Step 2, low-temperature freezing: inject the suspension obtained in step 1 into a capillary metal tube and then place it in a low-temperature environment of -30°C for freezing; the capillary metal tube can be a copper tube or a tungsten tube.

[0047] Step 3, freeze drying: placing the capillary metal tube frozen in step 2 in a vacuum environment at -70°C for 48 hours to allow the ice crystals in the capillary metal tube to sublime;

[0048] Step 4, impurity removal: the capillary metal tube obtained in step 3 is placed in a vacuum or inert gas environment at 400°C for 1 hour to thermally decompose the excess dispersion stabilizer and binder;

[0049] Step 5, high temperature sintering: the capillary metal tube obtained in step 4 is sintered at 1360°C, 2385°C and 2735°C for 8 hours in a vacuum or inert gas environment to obtain a porous electrode blank. The microscopic porous structure of the obtained porous electrode blank is anisotropic lamellar, isotropic lamellar, grid-like and radial.

[0050] Step 6, electric spark grinding: the porous electrode blank obtained in step 5 is subjected to electric spark grinding to obtain a porous electrode, wherein the diameter of the obtained porous electrode is ≤ 100 μm.

[0051] Embodiment 3

[0052] according to Figure 1 As shown, the present invention provides a porous electrode forming method for electrospark machining deep micro-holes, and the specific steps are as follows:

[0053] Step 1, suspension preparation: 40 vol.% of tungsten carbide nanoparticles, 1 vol.% of a dispersion stabilizer, and 1 vol.% of poly (2-ethyl-2-oxazoline) are mixed together, and deionized water is added and stirred with a magnetic stirrer for 24 hours to obtain a suspension. The dispersion stabilizer includes any one or more of sodium carboxymethyl cellulose, sodium polyacrylate, polypropylene alcohol, polyvinyl alcohol, and polyethylene glycol.

[0054] Step 2, low-temperature freezing: inject the suspension obtained in step 1 into a capillary metal tube and then place it in a low-temperature environment of -10°C for freezing; the capillary metal tube can be a copper tube or a tungsten tube.

[0055] Step 3, freeze drying: placing the capillary metal tube frozen in step 2 in a vacuum environment at -70°C for 48 hours to allow the ice crystals in the capillary metal tube to sublime;

[0056] Step 4, impurity removal: the capillary metal tube obtained in step 3 is placed in a vacuum or inert gas environment at 400°C for 1 hour to thermally decompose the excess dispersion stabilizer and binder;

[0057] Step 5, high temperature sintering: the capillary metal tube obtained in step 4 is sintered at 1145°C, 2010°C and 2300°C for 12 hours in a vacuum or inert gas environment to obtain a porous electrode blank. The microscopic porous structure of the porous electrode blank is anisotropic lamellar, isotropic lamellar, grid-like and radial.

[0058] Step 6, electric spark grinding: the porous electrode blank obtained in step 5 is subjected to electric spark grinding to obtain a porous electrode, wherein the diameter of the obtained porous electrode is ≤ 100 μm.

[0059] Embodiment 4

[0060] according to Figure 1 As shown, the present invention provides a porous electrode forming method for electrospark machining deep micro-holes, and the specific steps are as follows:

[0061] Step 1, preparation of suspension: 25 vol.% of graphite nanoparticles, 1 vol.% of a dispersing stabilizer, and 1 vol.% of poly(2-ethyl-2-oxazoline) are mixed together, and after adding deionized water, a magnetic stirrer is used to stir for 24 hours to obtain a suspension. The dispersing stabilizer includes any one or more of sodium carboxymethyl cellulose, sodium polyacrylate, polypropylene alcohol, polyvinyl alcohol, and polyethylene glycol.

[0062] Step 2, low-temperature freezing: inject the suspension obtained in step 1 into a capillary metal tube and then place it in a low-temperature environment of -40°C for freezing; the capillary metal tube can be a copper tube or a tungsten tube.

[0063] Step 3, freeze drying: placing the capillary metal tube frozen in step 2 in a vacuum environment at -70°C for 48 hours to allow the ice crystals in the capillary metal tube to sublime;

[0064] Step 4, impurity removal: the capillary metal tube obtained in step 3 is placed in a vacuum or inert gas environment at 400°C for 1 hour to thermally decompose the excess dispersion stabilizer and binder;

[0065] Step 5, high temperature sintering: the capillary metal tube obtained in step 4 is sintered at 1460°C, 2255°C and 2925°C respectively for 8 hours in a vacuum or inert gas environment to obtain a porous electrode blank. The microscopic porous structure of the obtained porous electrode blank is anisotropic lamellar, isotropic lamellar, grid-like and radial.

[0066] Step 6, electric spark grinding: the porous electrode blank obtained in step 5 is subjected to electric spark grinding to obtain a porous electrode, wherein the diameter of the obtained porous electrode is ≤ 100 μm.

[0067] Embodiment 5

[0068] according to Figure 1 As shown, the present invention provides a porous electrode forming method for electrospark machining deep micro-holes, and the specific steps are as follows:

[0069] Step 1, preparation of suspension: 35 vol.% copper nanoparticles, 1 vol.% dispersion stabilizer, and 1 vol.% binder are mixed together, deionized water is added, and the mixture is stirred for 24 hours using a magnetic stirrer to obtain a suspension. The dispersion stabilizer includes any one or more of sodium carboxymethyl cellulose, sodium polyacrylate, polypropylene alcohol, polyvinyl alcohol, and polyethylene glycol.

[0070] Step 2, low-temperature freezing: inject the suspension obtained in step 1 into a capillary metal tube and then place it in a low-temperature environment of -20°C for freezing; the capillary metal tube can be a copper tube or a tungsten tube.

[0071] Step 3, freeze drying: placing the capillary metal tube frozen in step 2 in a vacuum environment at -70°C for 48 hours to allow the ice crystals in the capillary metal tube to sublime;

[0072] Step 4, impurity removal: the capillary metal tube obtained in step 3 is placed in a vacuum or inert gas environment at 400°C for 1 hour to thermally decompose the excess dispersion stabilizer and binder;

[0073] Step 5, high temperature sintering: sinter the capillary metal tube obtained in step 4 at 815°C for 10 hours in a vacuum or inert gas environment to obtain a porous electrode blank. The microscopic porous structure of the porous electrode blank is anisotropic lamellar, isotropic lamellar, grid-like, or radial.

[0074] Step 6, electric spark grinding: the porous electrode blank obtained in step 5 is subjected to electric spark grinding to obtain a porous electrode, wherein the diameter of the obtained porous electrode is ≤ 100 μm.

[0075] The microstructure of the prepared porous electrode cross section and longitudinal section is shown in Figure 2-Figure 5 shown.

[0076] The above embodiments are not limited to the technical solutions of the embodiments themselves, and the embodiments can be combined with each other to form new embodiments. The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any modification or equivalent replacement that does not deviate from the spirit and scope of the present invention shall be included in the scope of the technical solutions of the present invention.

Claims

1. A method for forming a porous electrode for electrospark machining of deep micro-holes, characterized in that: The specific steps are as follows: Step 1, preparation of suspension: 20 vol.%-40 vol.% of nanoparticles, 1 vol.% of dispersion stabilizer, and 1 vol.% of binder are mixed together, and deionized water is added and stirred for 24 hours to obtain a suspension; Step 2, low temperature freezing: injecting the suspension obtained in step 1 into a capillary metal tube and then placing it in a low temperature environment of -50°C to -10°C for freezing; Step 3, freeze drying: placing the capillary metal tube frozen in step 2 in a vacuum environment at -70°C for 48 hours to allow the ice crystals in the capillary metal tube to sublime; Step 4, impurity removal: the capillary metal tube obtained in step 3 is placed in a vacuum or inert gas environment at 400°C for 1 hour to thermally decompose the excess dispersion stabilizer and binder; Step 5, high temperature sintering: sintering the capillary metal tube obtained in step 4 at a certain temperature T in a vacuum or inert gas environment for 6-12 hours to obtain a porous electrode blank; Step 6: Electric spark grinding: The porous electrode blank obtained in step 5 is subjected to electric spark grinding to obtain a porous electrode.

2. A porous electrode forming method for electrospark machining of deep micro-holes according to claim 1, characterized in that: The material of the nanoparticles in step 1 is any one of copper, tungsten, tungsten carbide and graphite.

3. The method for forming a porous electrode for electrospark machining deep micro-holes according to claim 1, characterized in that: The dispersion stabilizer in step 1 includes any one or more of sodium carboxymethyl cellulose, sodium polyacrylate, polypropylene alcohol, polyvinyl alcohol, and polyethylene glycol.

4. The method for forming a porous electrode for electrospark machining of deep micro-holes according to claim 1, characterized in that: The binder in the step 1 is poly (2-ethyl-2-oxazoline).

5. The method for forming a porous electrode for electrospark machining of deep micro-holes according to claim 1, characterized in that: The stirring in step 1 is performed using a magnetic stirrer.

6. The method for forming a porous electrode for electrospark machining of deep micro-holes according to claim 1, characterized in that: The capillary metal tube in step 2 is a copper tube or a tungsten tube.

7. The method for forming a porous electrode for electrospark machining of deep micro-holes according to claim 2, characterized in that: The temperature T in step five is 40%-80% of the melting point of the nanoparticle material.

8. A porous electrode forming method for electrospark machining deep micro holes according to any one of claim 1, characterized in that: The microscopic porous structure of the porous electrode blank obtained in step 5 is in the form of anisotropic lamellar, isotropic lamellar, grid or radial.

9. A porous electrode forming method for electrospark machining deep micro-holes according to any one of claim 1, characterized in that: The diameter of the porous electrode obtained in step 6 is ≤100 μm.

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