A method for forming a multi-hole electrode for electric discharge machining of deep micro-holes

Abstract

The application provides a multi-hole electrode forming method for electric spark machining of deep micro-holes, and belongs to the technical field of special machining. The method is prepared through a process of suspension preparation-low-temperature freezing-freeze drying-impurity removal-high-temperature sintering-electric spark grinding. The diameter of the prepared multi-hole electrode can reach below 100 microns. The multi-hole electrode has a micro-porous structure constructed by nanoparticles, can realize circulation of working liquid in the electrode, can deliver the working liquid with a certain speed and pressure to the deep part of the small hole, can slow down accumulation of electric erosion products, and can improve machining precision and machining efficiency of the micro-hole. The electric spark grinding treatment can be performed in different degrees according to machining requirements.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of special processing, and particularly relates to a multi-hole electrode forming method for electric spark machining of deep micro-holes. BACKGROUND

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

[0003] At present, in the application of electric spark micro-hole machining technology for high-precision deep micro-hole machining, there are many problems such as difficulty in effectively discharging the electric erosion particles generated by discharge and low machining efficiency. The electric erosion particles are not discharged in time, which will also cause abnormal discharge between the electrode and the hole wall, causing problems such as reduction of micro-hole surface quality and dimensional accuracy. Although the multi-hole electrode for electric spark small hole machining can also realize the machining mode of internal flushing, the diameter of the multi-hole electrode for electric spark machining of deep micro-holes is extremely small, and the preparation of the multi-hole electrode is extremely difficult.

[0004] Therefore, there is an urgent need for a multi-hole electrode forming method for electric spark machining of deep micro-holes to solve the above technical problems. SUMMARY

[0005] In order to solve the shortcomings and deficiencies of the prior art, a multi-hole electrode forming method for electric spark machining of deep micro-holes is provided, so as to solve the problem that the existing multi-hole motor is extremely difficult to prepare due to its extremely small diameter.

[0006] In order to achieve the purpose of the present application, a multi-hole electrode forming method for electric spark machining of deep micro-holes is provided, and the specific steps are as follows:

[0007] Step 1, preparation of suspension: 20vol.%-40vol.% of nanoparticles are mixed with 1vol.% of dispersion stabilizer and 1vol.% of binder, and after adding deionized water, stirring for 24h obtains a suspension;

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

[0009] Since the dispersing stabilizer has good water absorption, the mass fraction of the dispersing stabilizer cannot be too high, otherwise the suspension will become gelatinous; in addition, too much dispersing stabilizer will be difficult to remove in the high-temperature sintering step and will remain in the micro-porous structure, reducing the effective micro-pore area of the micro-porous structure, while too little dispersing stabilizer cannot prevent the nanoparticles from settling;

[0010] The binder can bond the nanoparticles together in the freezing process and the high-temperature sintering process, improving the strength of the micro-porous structure;

[0011] Deionized water has the characteristics of easy freezing and easy sublimation after freezing, facilitating subsequent low-temperature freezing and freeze-drying.

[0012] Step two, low-temperature freezing: after the suspension obtained in step one is injected into the capillary metal tube, it is placed in a low-temperature environment of -50℃ to -10℃ for freezing;

[0013] The lower the environmental temperature, the faster the freezing speed, and the lower the lamella thickness and the equivalent diameter of the single micro-pore of the micro-porous structure; conversely, the higher the environmental temperature, the higher the lamella thickness and the diameter of the single micro-pore.

[0014] Step three, freeze-drying: the capillary metal tube after freezing in step two is placed in a vacuum environment of -70℃ for 48h, so that the ice crystals in the capillary metal tube sublimate;

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

[0016] Step four, impurity removal: the capillary metal tube obtained in step three is placed in an environment of 400℃ in vacuum or with inert gas for 1h, so that the excess dispersing stabilizer and binder are thermally decomposed;

[0017] Step five, high-temperature sintering: the capillary metal tube obtained in step four is sintered at a certain temperature T in vacuum or with inert gas for 6-12h, obtaining a porous electrode blank;

[0018] Step six, electric spark grinding: the porous electrode blank obtained in step five is subjected to electric spark grinding, thereby obtaining a porous electrode.

[0019] As a further improvement of the above scheme, the material of the nanoparticles in step one is selected from any one of copper, tungsten, tungsten carbide and graphite.

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

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

[0022] As a further improvement of the above-mentioned scheme, the stirring in the step one uses a magnetic stirrer.

[0023] As a further improvement of the above-mentioned scheme, the capillary metal tube in the step two is a copper tube or a tungsten tube.

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

[0025] As a further improvement of the above-mentioned scheme, the micro-porous structure in the porous electrode initial blank obtained in the step five is a hetero-directional lamellar structure, a homo-directional lamellar structure, a grid structure, or a radial structure.

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

[0027] The present application has the following beneficial effects:

[0028] Compared with the prior art, the present application provides a method for forming a porous electrode for electric spark machining of deep and small holes, the diameter of the prepared porous electrode can be ≤100 μm, and the porous electrode has a micro-porous structure constructed by nanoparticles, so that the working liquid can flow in the electrode, the working liquid with a certain speed and pressure can be delivered to the deep part of the small hole, the accumulation of electric erosion products is slowed down, and the machining precision and efficiency of the small hole are improved, and different degrees of electric spark grinding can be performed according to the machining requirements. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A schematic diagram of the preparation of the porous electrode of the present application;

[0030] Figure 2 A schematic diagram of the appearance of the porous electrode prepared by the present application;

[0031] Figure 3 A microstructure diagram of the cross section of the porous electrode prepared by the present application;

[0032] Figure 4 A schematic diagram of the appearance of the porous electrode prepared by the present application; Figure 3 An enlarged view of A in FIG. 6;

[0033] Figure 5 A microstructure diagram of the longitudinal section of the porous electrode prepared by the present application. DETAILED DESCRIPTION

[0034] The specific embodiments of the present application are further described in detail below with reference to the accompanying drawings:

[0035] Example One

[0036] According to Figure 1 As shown in FIG. 1, the present application provides a method for forming a porous electrode for electric spark machining of deep micro holes, and the specific steps are as follows:

[0037] Step one, preparation of a suspension: 20 vol.% of copper nanoparticles and 1 vol.% of a dispersion stabilizer, 1 vol.% of poly(2 ethyl 2 oxazoline) are mixed together, and after adding deionized water, the suspension is obtained by stirring for 24 h using a magnetic stirrer. The dispersion stabilizer is selected from any one or several of sodium carboxymethyl cellulose, sodium polyacrylate, polypropylene alcohol, polyvinyl alcohol, and polyethylene glycol.

[0038] Step two, low-temperature freezing: the suspension obtained in step one is injected into a capillary metal tube and then placed in a low-temperature environment of -50°C for freezing; the capillary metal tube is selected from a copper tube or a tungsten tube.

[0039] Step three, freeze-drying: the capillary metal tube after freezing in step two is placed in a vacuum environment of -70°C for drying for 48 h, so that the ice crystals in the capillary metal tube sublimate;

[0040] Step four, impurity removal: the capillary metal tube obtained in step three is placed in an environment of 400°C, vacuum or inert gas, and heat treated for 1 h, so that the excess dispersion stabilizer and binder are thermally decomposed;

[0041] Step five, high-temperature sintering: the capillary metal tube obtained in step four is sintered at temperatures of 430°C, 758°C and 870°C, respectively, in a vacuum or inert gas environment for 6 h, to obtain a porous electrode blank. The micro-porous structure of the obtained porous electrode blank is heterodirectional lamellar, homodirectional lamellar, grid-shaped, and radial.

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

[0043] Example Two

[0044] According to Figure 1 As shown in FIG. 1, the present application provides a method for forming a porous electrode for electric spark machining of deep micro holes, and the specific steps are as follows:

[0045] Step one, suspension preparation: 30vol.% of tungsten nanoparticles are mixed with 1vol.% of dispersion stabilizer, 1vol.% of poly(2 ethyl 2 oxazoline), and after adding deionized water, stirring for 24h using a magnetic stirrer to obtain a suspension. The dispersion stabilizer includes any one or several of sodium carboxymethyl cellulose, sodium polyacrylate, polyacrylic alcohol, polyvinyl alcohol, and polyethylene glycol.

[0046] Step two, low-temperature freezing: the suspension obtained in step one is injected into a capillary metal tube and then placed in a low-temperature environment of -30℃ for freezing; the capillary metal tube is selected from a copper tube or a tungsten tube.

[0047] Step three, freeze-drying: the capillary metal tube after freezing in step two is placed in a vacuum environment of -70℃ for drying for 48h, so that the ice crystals in the capillary metal tube sublimate;

[0048] Step four, impurity removal: the capillary metal tube obtained in step three is placed in an environment of 400℃, vacuum or inert gas, and heat treated for 1h, so that the excess dispersion stabilizer and binder are thermally decomposed;

[0049] Step five, high-temperature sintering: the capillary metal tube obtained in step four is sintered at a temperature of 1360℃, 2385℃ and 2735℃, respectively, in a vacuum or inert gas environment for 8h to obtain a porous electrode blank. The micro-porous structure of the obtained porous electrode blank is heterodirectional lamellar, homodirectional lamellar, grid, and radial.

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

[0051] Example three

[0052] According to Figure 1 , the present application provides a porous electrode forming method for electric spark machining deep micro-holes, and the specific steps are as follows:

[0053] Step one, suspension preparation: 40vol.% of tungsten carbide nanoparticles are mixed with 1vol.% of dispersion stabilizer, 1vol.% of poly(2 ethyl 2 oxazoline), and after adding deionized water, stirring for 24h using a magnetic stirrer to obtain a suspension. The dispersion stabilizer includes any one or several of sodium carboxymethyl cellulose, sodium polyacrylate, polyacrylic alcohol, polyvinyl alcohol, and polyethylene glycol.

[0054] Step two, low-temperature freezing: the suspension obtained in step one is injected into a capillary metal tube and then placed in a low-temperature environment of -10℃ for freezing; the capillary metal tube is selected from a copper tube or a tungsten tube.

[0055] Step three, freeze-drying: the frozen capillary metal tube of step two is dried in a vacuum environment at -70°C for 48h, so that the ice crystals in the capillary metal tube sublimate;

[0056] Step four, impurity removal: the capillary metal tube obtained in step three is placed in an environment of 400°C, vacuum or inert gas, and kept for 1h, so that the excess dispersant and binder are thermally decomposed;

[0057] Step five, high-temperature sintering: the capillary metal tube obtained in step four is sintered at a temperature of 1145°C, 2010°C and 2300°C respectively in a vacuum or inert gas environment for 12h, to obtain a porous electrode blank. The micro-porous structure of the obtained porous electrode blank is hetero-directional lamellar, homodirectional lamellar, grid, and radial.

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

[0059] Example four

[0060] According to Figure 1 As shown in the figure, the present application provides a porous electrode forming method for electric spark machining deep micro-holes, and the specific steps are as follows:

[0061] Step one, preparation of suspension: 25vol.% of graphite nanoparticles are mixed with 1vol.% of dispersant and 1vol.% of poly(2-ethyl 2-oxazoline), and after adding deionized water, the suspension is obtained by stirring for 24h using a magnetic stirrer. The dispersant includes any one or several of sodium carboxymethyl cellulose, sodium polyacrylate, polypropylene alcohol, polyvinyl alcohol, and polyethylene glycol.

[0062] Step two, low-temperature freezing: the suspension obtained in step one is injected into a capillary metal tube and then frozen in a low-temperature environment at -40°C. The capillary metal tube is made of copper or tungsten.

[0063] Step three, freeze-drying: the frozen capillary metal tube of step two is dried in a vacuum environment at -70°C for 48h, so that the ice crystals in the capillary metal tube sublimate;

[0064] Step four, impurity removal: the capillary metal tube obtained in step three is placed in an environment of 400°C, vacuum or inert gas, and kept for 1h, so that the excess dispersant and binder are thermally decomposed;

[0065] Step five, high-temperature sintering: the capillary metal tube obtained in step four is sintered at a temperature of 1460℃, 2255℃ and 2925℃ respectively for 8h in a vacuum or inert gas environment to obtain a porous electrode blank. The micro-porous structure of the porous electrode blank obtained is heterodirectional lamellar, homodirectional lamellar, grid-shaped and radial.

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

[0067] Example five

[0068] According to Figure 1 As shown in FIG. 1, the present application provides a porous electrode forming method for electric spark machining deep micro-holes, and the specific steps are as follows:

[0069] Step one, preparation of suspension: 35vol.% copper nanoparticles are mixed with 1vol.% dispersion stabilizer and 1vol.% binder, and after adding deionized water, the suspension is obtained by stirring for 24h using a magnetic stirrer. The dispersion stabilizer includes any one or several of sodium carboxymethyl cellulose, sodium polyacrylate, polyacrylic alcohol, polyvinyl alcohol and polyethylene glycol.

[0070] Step two, low-temperature freezing: the suspension obtained in step one is injected into a capillary metal tube and then placed in a low-temperature environment of -20℃ for freezing; the capillary metal tube is selected from a copper tube or a tungsten tube.

[0071] Step three, freeze-drying: the capillary metal tube after freezing in step two is placed in a vacuum environment of -70℃ for drying for 48h, so that the ice crystals in the capillary metal tube sublimate;

[0072] Step four, impurity removal: the capillary metal tube obtained in step three is placed in a temperature of 400℃ in a vacuum or inert gas environment for 1h to make the excess dispersion stabilizer and binder thermally decompose;

[0073] Step five, high-temperature sintering: the capillary metal tube obtained in step four is sintered at a temperature of 815℃ in a vacuum or inert gas environment for 10h to obtain a porous electrode blank. The micro-porous structure of the porous electrode blank obtained is heterodirectional lamellar, homodirectional lamellar, grid-shaped and radial.

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

[0075] The microstructure diagrams of the cross section and longitudinal section of the prepared porous electrode are shown in FIG. 2. Figures 2-5 As shown in FIG. 2.

[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 application and not to limit them, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered in the scope of the technical solutions of the present application.

Claims

1. A method for forming a multi-hole electrode for electric discharge machining of deep micro-holes, characterized by: The specific steps are as follows: Step one, preparation of the suspension: 20vol.%-40vol.% of nanoparticles and 1vol.% of dispersion stabilizer and 1vol.% of binder are mixed together, and after adding deionized water, stirring for 24h to obtain the suspension; wherein the material of the nanoparticles is any one of copper, tungsten, tungsten carbide and graphite, the dispersion stabilizer includes any one or several of sodium carboxymethyl cellulose, sodium polyacrylate, polyvinyl alcohol, polyethylene glycol, and the binder is poly(2-ethyl 2-oxazoline); Step two, low-temperature freezing: the suspension obtained in step one is injected into a capillary metal tube and then placed in a low-temperature environment of-50℃ to-10℃ for freezing; wherein the capillary metal tube is selected from a copper tube or a tungsten tube; Step three, freeze-drying: the capillary metal tube after freezing in step two is placed in a vacuum environment of-70℃ for drying for 48h, so that the ice crystals in the capillary metal tube sublimate; Step four, impurity removal: the capillary metal tube obtained in step three is placed in an environment of 400℃, vacuum or inert gas, and heat treated for 1h, so that the excess dispersion stabilizer and binder are thermally decomposed; Step five, high-temperature sintering: the capillary metal tube obtained in step four is sintered at a certain temperature T in a vacuum or inert gas environment for 6-12h to obtain a porous electrode blank; wherein the temperature T is 40%-80% of the melting point of the nanoparticle material; Step six, electric spark grinding: the porous electrode blank obtained in step five is subjected to electric spark grinding, so as to obtain a porous electrode.

2. The method according to claim 1, wherein the method is characterized by: The stirring in step one is performed by using a magnetic stirrer.

3. The method according to claim 1, wherein the method is characterized by: The micro-porous structure of the porous electrode blank obtained in step five is anisotropic lamellar, isotropic lamellar, grid, and radial.

4. The method according to claim 1, wherein the method is characterized by: The diameter of the porous electrode obtained in step six is ≤100μm.

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