CN111570942A

CN111570942A - Side wall insulated cathode of jet electrochemical machining tool

Info

Publication number: CN111570942A
Application number: CN202010352896.5A
Authority: CN
Inventors: 王盼盼; 何亚峰; 徐波; 干为民; 郭魂
Original assignee: Changzhou Institute of Technology
Current assignee: Changzhou Institute of Technology
Priority date: 2020-04-29
Filing date: 2020-04-29
Publication date: 2020-08-25

Abstract

The invention relates to a side wall insulated spray electrochemical machining tool cathode, wherein a Laval spray pipe-shaped electrolyte channel is arranged in the tool cathode, and an insulating layer is arranged on the outer peripheral surface of the tool cathode; the electrolyte channel sequentially consists of a stable section, a reducing section, a throat part and a gradually expanding section from an electrolyte inlet to an electrolyte outlet to form the Laval nozzle-shaped electrolyte channel; the stable section is an electrolyte inlet, and the tail part of the divergent section is an electrolyte outlet. According to the invention, the tool cathode of the Laval spraying tubular electrolyte channel is adopted, so that the electrolyte in the Laval spraying tubular electrolyte channel is in a laminar state when passing through the Laval spraying tubular channel, the liquid trajectory of the electrolyte has no obvious irregular pulsation, the flow velocity is uniform, and the precision of a processing area is higher and the surface quality is better; in addition, the invention adopts a low-temperature plasma spraying method to realize the insulation of the side wall of the cathode of the tool, thereby avoiding the stray corrosion caused by the electrolytic reaction and improving the precision of the processed hole.

Description

Side wall insulated cathode of jet electrochemical machining tool

Technical Field

The invention relates to the technical field of electrolytic machining devices, in particular to a cathode of a jet electrolytic machining tool with an insulated side wall.

Background

Electrolytic machining is a machining method for etching and removing metal materials by dissolving an electrochemical anode in electrolyte and realizing the machining and forming of workpieces. In the processing process, the tool cathode and the workpiece anode are not in a direct contact state all the time, the electrochemical reaction generated on the tool cathode only relates to oxygen evolution reaction without material dissolution, and the surface internal stress does not exist in the processing, so that the workpiece processing deformation is small, and the tool is not lost; the workpiece material is removed in an ionic state, and the whole process is cold processing, so that the surface quality of the formed workpiece is good, and no cold hardening layer or processing line exists; the processing material is wide, the molding period is short, and the processing can be carried out on the materials with complicated shapes and difficult processing such as various holes, complicated three-dimensional molded surfaces, cavities and the like at high speed. Although the electrolytic machining has many advantages, the electrolytic machining also has some defects, the electrolytic machining process is influenced by various physical factors, the process parameters influencing the machining quality are more, multiple sets of process tests are needed to obtain the mature electrolytic machining process parameters of certain machined parts, the preparation tests not only occupy a large amount of working time, but also cannot estimate consumed process raw materials, and are waste of resources, so that the preparation period of the electrolytic machining is longer; in addition, the further development of electrolytic machining is greatly limited by low machining precision, low machining stability and the like. Therefore, the design of the cathode shape of the tool and the development of the experimental device in the electrochemical machining require a lot of time, and these factors are not favorable for the popularization of the electrochemical machining application.

The electrochemical machining system is shown in figure 1 and comprises 61-a power supply, 62-a feeding device, 63-a Z axis, 1-a tool cathode, 4-an electrolyte inlet, 7-a workpiece anode (namely a workpiece to be machined), 8-a working tank and 9-an electrolyte outlet pipe. However, in order to realize the processing of size and shape, the following specific process conditions must be provided:

(1) a small gap (called the machining gap) is maintained between the workpiece anode and the tool cathode (mostly the forming tool cathode), typically in the range of 0.1-1 mm;

(2) the electrolyte continuously flows through the machining gap at a high speed (6-30m/s) to ensure that dissolved products on the anode of the workpiece and heat generated when the electrolytic current passes through the electrolyte are taken away and depolarized;

(3) the workpiece anode and the tool cathode are respectively connected with a direct current power supply (generally 10-24V), and under the two process conditions, the current density of the machining gap between the two electrodes can reach 10-100A/cm²An order of magnitude;

(4) the part of the workpiece anode corresponding to the raised part of the tool cathode dissolves faster than other parts, the workpiece is continuously dissolved according to the end profile of the tool along with the continuous and slow feeding of the tool cathode to the workpiece anode, electrolytic products are continuously taken away by the high-speed flowing electrolyte, and finally the forming shape of the tool is 'copied' on the workpiece.

The design of the cathode of the electrochemical machining tool has the following problems to be solved: (1) the electrolytic machining generally uses a rod-shaped standard cathode, the electrolyte generally adopts a mode of taking internal spraying as a main mode and taking external spraying as an auxiliary mode, namely, the internal spraying and the external spraying are simultaneously carried out when a workpiece is cut in and cut out, and the flow field is easy to guarantee at the moment. After the cathode of the tool is cut into the anode of the workpiece, the clearance between the anode of the workpiece and the cathode of the tool is very small, and the external spraying is mainly dependent on the internal spraying when the external spraying is out of action. During internal spraying, the pressure and the flow rate of the electrolyte in the machining gap are not uniform, so that the surface quality, the machining efficiency and the precision of the workpiece are difficult to ensure. (2) Suppression of stray corrosion electric field: the electric field cannot be completely confined in a desired processing area in the processing process, and an area which is far away from the cathode of the tool on the anode of the workpiece is influenced by a stray electric field to be corroded and removed although the current density is low and the electric field is relatively weak, so that stray corrosion of the cathode of the tool is caused, a side gap is expanded when a three-dimensional structure is processed, and finally the cathode of the tool is caused to generate a tapered side wall.

Disclosure of Invention

In order to solve the technical problems that the quality of a machined workpiece is difficult to ensure due to the fact that the flow velocity of electrolyte in a machining gap is not uniform during internal spraying and stray corrosion is caused in the electrolytic process, the cathode of the electrolytic machining tool with the insulated side wall is provided. The tool cathode solves the technical problem that the surface quality, the processing efficiency and the precision of a workpiece are difficult to ensure due to the fact that a flow field is irregularly distributed and is in a laminar flow state caused by a conventional electrolyte channel in the tool cathode, and also realizes the insulation of the side wall of the tool cathode, namely the insulation of the electrolyte passing through the peripheral surface, so that stray corrosion is avoided.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a side wall insulated spray electrochemical machining tool cathode having a Laval spray tube shaped electrolyte passage therein, the tool cathode having an insulating layer on an outer peripheral surface thereof.

Further, the electrolyte channel sequentially comprises a stable section, a reducing section, a throat part and a gradually expanding section from an electrolyte inlet to an electrolyte outlet; the electrolyte inlet is one end of the stabilizing section, and the tail part of the divergent section is the electrolyte outlet.

Furthermore, the length of the stabilizing section is 60mm, the inner diameter of the stabilizing section is 10mm, and the wall thickness is 1 mm-1.5 mm.

Still further, the length of the tapered section is 40mm, and the angle of the cone apex angle α of the tapered section is 5 °.

Furthermore, the length of the divergent section is 10-11 mm, the inner diameter of the outlet of the divergent section is 7-8 mm, and the angle of the cone apex angle beta of the divergent section is 8-10 degrees.

Furthermore, the length of the throat part is 9 mm-10 mm, and the inner diameter of the throat part is 4 mm-5 mm.

Still further, the junction of throat portion and the divergent section is the curved line structure.

Preferably, the curvature radius of the junction of the throat part and the divergent section is 1 mm-3 mm.

Further, the insulating layer is a nano alumina insulating layer.

Further, the preparation method of the insulating layer comprises the following steps: preheating the tool cathode to 400 ℃, preparing an insulating layer on the peripheral surface of the tool cathode by adopting a low-temperature plasma spraying method, wherein the insulating layer is prepared on the peripheral surface of the lower part of the tool cathode, the current-carrying gas of the low-temperature plasma spraying method is argon and hydrogen, the flow rate of the argon is 50-100L/min, the flow rate of the hydrogen is 5-10L/min, the spraying time is 5-30 s, and the spraying distance is 30-40 mm.

The section of a cathode electrolyte channel of a tool for conventional jet electrolytic machining is linear, electrolyte enters from an inlet of the electrolyte channel and then is in a turbulent flow state, a flow field is irregularly distributed, and the flow velocity is uneven, so that the surface quality, the machining efficiency and the precision of a workpiece subjected to electrolytic machining are difficult to guarantee. The liquid electrolyte is generally lower than gas compressibility, and the Laval nozzle for gas actually plays a role of a gas flow velocity amplifier, but the liquid electrolyte is much smaller than gas under compression, and the Laval nozzle-shaped electrolyte channel is designed to ensure that the inner diameter of a stable section at an electrolyte inlet is equal to the inner diameter at an electrolyte outlet, so that the uniform flowing effect of the electrolyte in the electrolyte channel can be realized; if the angle of the cone vertex angle of the tapered section and the tapered section is too large or too small, the flow velocity of the electrolyte is not uniform; the throat part of the water-cooled generator is a transition area, the size of the throat part and the inner diameter of an outlet of a divergent section are critical, the improper size of the throat part influences the flow state of electrolyte in the transition area and influences the flow state of the electrolyte at an electrolyte outlet of the divergent section, and the proper inner diameter of the outlet of the divergent section can enable the electrolyte not to expand or compress but to be parallel and uniform jet flow.

The beneficial technical effects are as follows: during jet electrolysis, the interior of the tool cathode is in a turbulent flow state, the problems of irregular distribution of an electrolyte flow field and uneven flow velocity caused by the electrolyte channel in the tool cathode are solved by adopting the tool cathode of the Laval spraying tubular electrolyte channel, the electrolyte in the tool cathode is in a laminar flow state when passing through the Laval spraying tubular electrolyte channel, and the electrolyte liquid track has no obvious irregular pulsation and is uniform in flow velocity; by usingWhen the tool cathode of the invention is used for processing high-temperature alloy, the current density is as high as 2000A/cm²The precision of the processing area is higher and the surface quality is better; in addition, because an electric field exists between the surface of the side wall of the tool cathode and the workpiece in the feeding process of the workpiece cathode, the side wall of the tool cathode which is not subjected to insulation treatment and the workpiece anode form an electrolytic cell, electrolytic reaction occurs, and metal corresponding to the surface of the side wall of the tool cathode is continuously dissolved, so that stray corrosion is caused, the inner wall of an electrochemical machining small hole is in a horn shape, and the precision of the hole is reduced.

Drawings

FIG. 1 is a schematic diagram of an electrochemical machining system in which 61-power supply, 62-feed, 63-Z axis, 1-tool cathode, 4-electrolyte inlet, 7-workpiece, 8-work cell, 9-electrolyte outlet tube.

FIG. 2 is a schematic cross-sectional view of a tool cathode with insulated side walls according to example 1 of the present invention, wherein 1 is a tool cathode, 2 is an electrolyte channel, 3 is an insulating layer, 4 is an electrolyte inlet, 5 is an electrolyte outlet, 21 is a stabilizing section, 22 is a tapering section, 23 is a throat, and 24 is a diverging section.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Unless specifically stated otherwise, the numerical values set forth in these examples do not limit the scope of the invention. Techniques, methods known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

Example 1

A cathode of a side wall insulated jet electrochemical machining tool is shown in a schematic cross-sectional structure view in fig. 2, a Laval nozzle-shaped electrolyte channel 2 is arranged in the tool cathode 1, and a nano alumina insulating layer 3 is arranged on the outer peripheral surface of the lower part of the tool cathode 1.

The electrolyte channel sequentially comprises a stable section 21, a tapered section 22, a throat 23 and a divergent section 24 from an electrolyte inlet to an electrolyte outlet; the electrolyte inlet 4 is one end of the stable section 21, and the tail part of the divergent section 24 is the electrolyte outlet 5;

wherein, the length L1 of the stable section 21 is designed to be 60mm, the inner diameter d1 is designed to be 10mm, and the wall thickness h is designed to be 1 mm-1.5 mm; (ii) a Designing the length L2 of the tapered section 22 to be 40mm, and the angle of the cone vertex angle alpha of the tapered section 22 to be 5 degrees; designing the length L4 of the divergent section 24 to be 10-11 mm, the inner diameter d4 of an outlet of the divergent section 24 to be 7-8 mm, and the angle of the cone apex angle beta of the divergent section 24 to be 8-10 degrees; the length L3 of the throat part 23 is designed to be 9 mm-10 mm, and the inner diameter d3 is designed to be 4 mm-5 mm; the junction of the throat 23 and the divergent section 24 is designed to be of a curve structure, and the curvature radius r is 1 mm-3 mm.

The preparation method of the nano alumina insulating layer 3 comprises the following steps: preheating the tool cathode 1 to 400 ℃, and preparing a nano aluminum oxide insulating layer 3 on the peripheral surface of the lower part of the tool cathode 1 by adopting a low-temperature plasma spraying method, wherein the current-carrying gas of the low-temperature plasma spraying method is argon and hydrogen, the flow rate of the argon is 50L/min-100L/min, the flow rate of the hydrogen is 5L/min-10L/min, the spraying time is 5 s-30 s, and the spraying distance is 30 mm-40 mm; the thickness of the prepared insulating layer can be adjusted according to the spraying time and the spraying distance.

In the process of low-temperature plasma spraying, the sprayed nano alumina particles are accelerated to the ultrahigh speed of 300-1200 m/s by supersonic carrier gas, impact the surface of a substrate under the condition of being lower than the melting point of the nano alumina material, generate plastic deformation by utilizing kinetic energy, and are combined with the sprayed substrate to form a nano alumina insulating layer on the surface of the substrate. The low-temperature plasma spraying method can avoid residual thermal stress generated by the nano aluminum oxide insulating coating and adverse chemical reaction in the spraying process due to low-temperature operation; in addition, the low-temperature plasma spraying method has high spraying efficiency, greatly preserves the microstructure of the sprayed particles, and has the advantages of small thickness of the prepared nano aluminum oxide insulating layer, insulating the cathode of the tool to the side wall, avoiding stray corrosion and improving the precision of the processed hole to a certain extent.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims

1. A side wall insulated spray electrochemical machining tool cathode, characterized in that the tool cathode (1) has a laval spray tube-like electrolyte passage (2) therein, and the outer circumferential surface of the tool cathode (1) has an insulating layer (3).

2. A side wall insulated spray electrochemical machining tool cathode according to claim 1, characterized in that the electrolyte channel (2) comprises in sequence from the electrolyte inlet (4) to the electrolyte outlet (5) a stabilizing section (21), a tapering section (22), a throat (23), a diverging section (24); the electrolyte inlet (4) is one end of the stable section (21), and the tail part of the divergent section (24) is the electrolyte outlet (4).

3. A side wall insulated spray electrochemical machining tool cathode according to claim 2, wherein the length of the stabilizing section (21) is 60mm, the inner diameter of the stabilizing section (21) is 10mm, and the wall thickness is 1mm to 1.5 mm.

4. A side wall insulated spray electrochemical machining tool cathode according to claim 2, characterized in that the length of the tapered section (22) is 40mm and the angle of the cone apex angle α of the tapered section (22) is 5 °.

5. A side wall insulated spray electrochemical machining tool cathode according to claim 2, wherein the length of the diverging section (24) is 10mm to 11mm, the inside diameter of the outlet of the diverging section (24) is 7mm to 8mm, and the angle of the cone apex angle β of the diverging section (24) is 8 ° to 10 °.

6. A side wall insulated spray electrochemical machining tool cathode according to claim 2, wherein the throat (23) has a length of 9mm to 10mm and the throat (23) has an inner diameter of 4mm to 5 mm.

7. A side wall insulated spray electrochemical machining tool cathode according to claim 2, wherein the junction of the throat (23) and the diverging section (24) is a curvilinear configuration.

8. A side wall insulated spray electrochemical machining tool cathode according to claim 7, wherein the radius of curvature at the junction of the throat (23) and the diverging section (24) is between 1mm and 3 mm.

9. A side wall insulated spray electrochemical machining tool cathode according to any of claims 1 to 8, characterized in that the insulating layer (3) is a nano alumina insulating layer.

10. A side wall insulated spray electrochemical machining tool cathode according to claim 9, characterized in that the insulating layer (3) is prepared by: preheating the tool cathode (1) to 400 ℃, preparing an insulating layer (3) on the peripheral surface of the tool cathode (1) by adopting a low-temperature plasma spraying method, wherein the insulating layer (3) is prepared on the peripheral surface of the lower part of the tool cathode (1), the current-carrying gas of the low-temperature plasma spraying method is argon and hydrogen, the flow rate of the argon is 50L/min-100L/min, the flow rate of the hydrogen is 5L/min-10L/min, the spraying time is 5 s-30 s, and the spraying distance is 30 mm-40 mm.