A wire electrode for slow wire electrical discharge machining

Abstract

The present invention discloses a wire electrode for slow wire electrical discharge machining, comprising: a core material; an intermediate layer located outside the core material; and a surface layer located outside the intermediate layer; wherein the core material is a metal or an alloy, the intermediate layer is a copper-zinc alloy, and the surface layer contains carbon elements; the carbon element content on the surface of the wire electrode is 0.2-60 wt%. The wire electrode for slow wire electrical discharge machining of the present invention has good surface layer conductivity, can maintain a high cutting machining speed for a long time, has high machining accuracy and a simple preparation process.

Description

Technical Field

[0001] The present invention belongs to the field of wire electrical discharge machining, and particularly relates to a wire electrode for slow wire electrical discharge machining. Background Art

[0002] Wire cut Electrical Discharge Machining (WEDM for short), its basic working principle is to use a continuously moving thin metal wire as an electrode to perform pulsed spark discharge on the workpiece to be machined to erode metal and cut into shape. When machining a workpiece by wire cut electrical discharge machining, the workpiece is connected to the positive pole of the pulsed power supply, and the wire electrode is connected to the negative pole of the high-frequency pulsed power supply as the tool electrode. The pulsed power supply provides the machining energy, and at the same time, a special wire cutting working fluid is applied during the machining process to remove the debris generated during the machining. When working with electricity, under the action of a strong electric field, the surfaces of the positive and negative poles are respectively bombarded by electron flow and ion flow, so that an instantaneous high-temperature heat source is formed in the gap between the workpiece and the wire electrode, causing local metal to melt and vaporize. Thus, corrosion pits are formed on the wire electrode and the workpiece, and at the same time, the working fluid is vaporized. The vaporized working fluid and the workpiece material vapor expand rapidly instantaneously. Under the combined action of this thermal expansion and the flushing of the working fluid, the melted and vaporized workpiece material is ejected from the discharge gap, and thus a spark discharge process is completed. Repeat the above spark discharge process to cut the workpiece into shape.

[0003] Process indexes such as the cutting speed, cutting accuracy, and surface finish of the workpiece after machining in wire cut electrical discharge machining are not only affected by the wire cut electrical discharge machining equipment, but also have a close relationship with the performance of the wire electrode used.

[0004] In the process of technological development, the wire electrode for wire cut electrical discharge machining has experienced four generations of product updates and developments: pure copper wire, brass wire, galvanized wire, and coated wire. A certain thickness of high-zinc alloy layer (i.e., an alloy layer with a high zinc content) is plated on the surface of the coated wire. By using the characteristics of the high-zinc alloy, a higher vaporization pressure can be achieved, which helps to improve the machining speed. According to the different compositions of the plated high-zinc alloy, the coated wire can be divided into γ-coated wire, β-coated wire, and composite coated wire. The coated wire is a type of wire electrode widely used at present.

[0005] However, the coated wire still has certain defects in actual production and machining applications. Since the surface high-zinc alloy is easy to melt and vaporize and has poor discharge corrosion resistance, as the wire cut electrical discharge machining progresses, the surface high-zinc alloy layer is consumed relatively quickly and it is difficult to play the surface role for a long time. As the surface high-zinc alloy layer disappears, the cutting machining speed slows down accordingly, and the cutting machining accuracy also decreases accordingly. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this purpose, an object of the present invention is to provide a wire electrode for slow wire electrical discharge machining, the wire electrode having good surface conductivity, being able to maintain a high cutting speed for a long time, having high cutting accuracy and a simple preparation process.

[0007] According to one aspect of the present invention, there is provided a wire electrode for slow wire electrical discharge machining, comprising: a core material; an intermediate layer located outside the core material; and a surface layer located outside the intermediate layer; wherein, the core material is a metal or an alloy, the intermediate layer is a copper-zinc alloy, and the surface layer contains carbon; the carbon element content on the surface of the wire electrode is 0.2 - 60 wt%.

[0008] The present invention has the following beneficial effects:

[0009] 1. The surface layer of the wire electrode for slow wire electrical discharge machining of the present invention contains carbon, which has a high conductivity, improves the current transmission efficiency during electrical discharge machining of the wire electrode, and improves the cutting speed.

[0010] 2. The surface layer of the wire electrode for slow wire electrical discharge machining of the present invention contains carbon. Since carbon has a high melting point, the wire electrode surface has high resistance to discharge corrosion. During the electrical discharge machining process, the surface layer of the wire electrode can maintain a relatively stable structure for a long time, ensuring that the surface layer of the wire electrode functions for a long time and maintaining the high cutting speed of the wire electrode. At the same time, the high resistance to discharge corrosion of the wire electrode surface enables the discharge gap between the wire electrode and the workpiece to be maintained more stably during the electrical discharge machining process, achieving a more uniform and stable discharge intensity and improving the cutting accuracy of the workpiece.

[0011] 3. The carbon element content on the surface of the wire electrode for slow wire electrical discharge machining of the present invention is limited within the range of 0.2 - 60 wt%, which can ensure that the wire electrode has a high cutting rate, taking into account both high cutting speed and high cutting accuracy, and ensuring that the wire electrode is easy to produce and manufacture. Carbon has the characteristics of high melting point and high vaporization temperature and is difficult to vaporize during electrical discharge machining. As the carbon element content on the wire electrode surface increases, although the conductivity of the wire electrode is improved, which is beneficial to improving the cutting speed, at the same time, the content of easily vaporizable components on the wire electrode surface is reduced, reducing the surface vaporization erosion effect and having an adverse impact on the cutting speed. In addition, too high a surface carbon element content will also cause the surface layer structure of the wire electrode to be easily detached, increasing the production and processing difficulty of the wire electrode.

[0012] Preferably, the carbon element content on the surface of the electrode wire is 1-20 wt%. Limiting the carbon element content on the surface of the electrode wire within the above range can ensure high cutting speed and cutting accuracy during electrical discharge machining using the electrode wire. Specifically, the carbon element content on the surface of the electrode wire can be 1-15 wt%, 1-10 wt%, 1.5-20 wt%, 1.5-15 wt%, 1.5-10 wt%.

[0013] Preferably, at least part of the carbon element in the surface layer exists in the form of elemental carbon. Elemental carbon has high electrical conductivity and melting point. The existence of the carbon element in the surface layer in the form of elemental carbon is conducive to further improving the electrical conductivity and surface discharge corrosion resistance of the electrode wire, thereby improving the cutting speed and cutting accuracy.

[0014] Preferably, the elemental carbon includes graphite and / or amorphous carbon. Graphite and amorphous carbon have excellent electrical conductivity. The electrode wire with graphite and / or amorphous carbon in the surface layer has a higher cutting speed.

[0015] Preferably, the surface layer discontinuously covers the outside of the intermediate layer, and the intermediate layer and / or the core material are exposed at the discontinuity of the surface layer. The surface layer discontinuously covers the outside of the intermediate layer, and a tip will be formed at the discontinuity of the surface layer. The tip is more likely to discharge. During wire electrical discharge machining, it can reduce the reaction time for the electrode wire to generate electrical discharge, thereby further accelerating the wire electrical discharge machining speed. At the same time, the exposed intermediate layer or core material can further improve the electrical conductivity of the surface layer, which is beneficial to enhancing the transmission of discharge energy, and further enhancing the cutting speed.

[0016] Preferably, the copper-zinc alloy of the intermediate layer is at least one of β-phase copper-zinc alloy, β' ’ -phase copper-zinc alloy, and γ-phase copper-zinc alloy. The β-phase copper-zinc alloy and β' ’ -phase copper-zinc alloy have high electrical conductivity, which can improve the discharge efficiency and thus enhance the cutting speed; the γ-phase copper-zinc alloy has a high zinc content, and the gasification and erosion effect are obvious during wire electrical discharge machining, which is also beneficial to the improvement of the cutting speed. The β' phase can remain stable below a specific temperature. It has an ordered crystal lattice. If the temperature exceeds this specific temperature, the β' phase will become a disordered β phase. According to the general view, the conversion between the β phase and the β' phase cannot be inhibited, but it has little impact on their mechanical and electrical characteristics. Therefore, in the context of this application, unless clearly distinguished, when referring to the β phase, it also means referring to the β' phase.

[0017] Preferably, the intermediate layer has cracks. Tips are formed at the cracks, and the tips are more likely to discharge electricity. During wire electrical discharge machining, the reaction time for the electrode wire to generate electric sparks can be reduced, thereby accelerating the wire electrical discharge machining speed. Additionally, the cracks can also increase the cutting speed by enlarging the contact area between the electrode wire and the working fluid. Therefore, after the surface layer is consumed, the crack structure of the intermediate layer can further accelerate the cutting speed.

[0018] Preferably, the core material is copper or a copper alloy. Copper and copper alloys have excellent electrical conductivity. Using such a core material ensures that the electrode wire has excellent performance.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the energy spectrum test of the surface carbon content of the electrode wire of the present invention by scanning electron microscopy. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Embodiments of the present invention will be described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] Embodiments of the present invention will be described below with reference to the accompanying drawings.

[0023] Before presenting the specific embodiments, the composition, structural features, and test methods for the content of related components of the wire electrode for slow wire electrical discharge machining provided by the present invention are described as follows:

[0024] When preparing the bus bar, brass bus bars are generally used. Specifically, they are generally made of CuZn37 brass or CuZn40 brass. It is also possible to use pure copper (i.e., copper) to prepare the bus bar, or copper alloys other than brass to prepare the bus bar, or other metals or alloys to prepare the bus bar.

[0025] In the present invention, the surface carbon content of the electrode wire refers to the carbon element content in the outermost circumferential part of the electrode wire product that is in contact with the environment. Here, the surface of the electrode wire is different from the surface layer of the electrode wire. The surface layer of the electrode wire is the outermost layer structure with a certain thickness of the electrode wire, and the outermost part of the surface layer in contact with the environment constitutes part or all of the surface of the electrode wire.

[0026] The surface carbon content of the electrode wire can be measured by elemental composition test methods known in the art. In the embodiments of the present invention, the method of performing an energy spectrum test on the surface of the electrode wire under an electron scanning electron microscope is used to measure the surface carbon content of the electrode wire. Specifically, as Figure 1As shown, using conventional laboratory electron scanning electron microscope and energy spectrometer equipment, the electrode wire sample is placed in the sample chamber, and a rectangular test area is selected on the surface of the electrode wire shown by the electron scanning electron microscope for energy spectrum determination. The short side length of the rectangular area is 1-2 times the radius of the electrode wire, and the long side length is 1-5 times the short side length. At different parts of the same electrode wire, the distribution of each element is not completely the same. The carbon content is measured by the above method at multiple different parts of the same electrode wire, and the average value of the carbon content at each different part is taken to obtain the surface carbon content of the electrode wire. In the following embodiments of the present invention, 10 different parts are taken on the same electrode wire, and the surface carbon content of each part is measured respectively by the above electron scanning electron microscope energy spectrum test method. Then, the average value of the 10 obtained carbon content values is taken as the surface carbon content of the corresponding electrode wire.

[0027] The surface carbon content of the electrode wire is in the range of 0.2-60wt%. When the surface carbon content of the electrode wire is too low, the carbon content with high conductivity and high melting point is relatively low, and its functions of improving the current transmission efficiency during electrical discharge machining of the electrode wire, increasing the cutting speed, and maintaining the long-term effect of the surface layer and improving the cutting accuracy are not obvious; while when the surface carbon content of the electrode wire is too high, due to the characteristics of high melting point and high gasification temperature of carbon, the gasification erosion effect on the surface of the electrode wire will be greatly reduced, reducing the cutting speed, and the too high surface carbon element content will also make the surface layer structure of the electrode wire easy to fall off, increasing the production and processing difficulty of the electrode wire. Controlling the surface carbon content of the electrode wire within the above range can ensure that the electrode wire has a high cutting rate, taking into account both high cutting speed and high cutting accuracy, and ensuring that the electrode wire is easy to produce and manufacture.

[0028] The β' phase can remain stable below a specific temperature and has an ordered lattice. If the temperature exceeds this specific temperature, the β' phase will become the disordered β phase. According to the general view, the conversion between the β phase and the β' phase cannot be inhibited, but it has little impact on their mechanical and electrical characteristics. For the convenience of description, in the following embodiments, the β phase is used to express, and when referring to the β phase, it always means referring to the β' phase, that is, the β phase in the following text represents one or both of the β phase and the β' phase.

[0029] Example 1:

[0030] The following process is used to prepare the slow wire electrical discharge machining electrode wire of this embodiment:

[0031] S100: Provide a CuZn37 brass bus bar with a wire diameter specification of 1.2mm;

[0032] S101: Galvanize the surface of the bus bar with a plating solution containing additives to form a 10-μm thick galvanized layer on the surface of the bus bar, and produce the first wire blank. The additive is one or a mixture of more than one of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the plating solution is 15 g / L.

[0033] S102: Heat-treat the first wire blank in a flowing air atmosphere. The heat-treatment temperature is 240 °C and the heat-treatment time is 45 h. The additive decomposes upon heating during the heat treatment to produce the second wire blank. The second wire blank has a core material, a β-phase copper-zinc alloy layer, a γ-phase copper-zinc alloy layer, and a surface layer from the inside out.

[0034] S103: Perform multi-mode continuous drawing and stress-relieving annealing on the second wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm.

[0035] Measure the surface carbon content of the electrode wire prepared by the above process using an electron scanning electron microscope and an energy spectrometer. Measure the surface carbon content at 10 different positions and take the average value as the surface carbon content of the electrode wire. Also determine the conductivity and surface adhesion of the electrode wire prepared by the above process. The test results are shown in Table 1.

[0036] Test the electrode wire prepared by the above process using an Archie E350 machine. The test workpiece material is 8407, the test workpiece size is 6 mm (length) * 6 mm (width) * 50 mm (thickness), and the test machining tool passes are selected as "one cut and four repairs". The test results are shown in Table 2.

[0037] Example 2:

[0038] Prepare the slow wire electrical discharge machining electrode wire of this example using the following process:

[0039] S100: Provide a CuZn40 brass bus bar with a wire diameter specification of 0.5 mm.

[0040] S101: Galvanize the surface of the bus bar with a plating solution containing additives to form a 20-μm thick galvanized layer on the surface of the bus bar, and produce the first wire blank. The additive is one or a mixture of more than one of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the plating solution is 10 g / L.

[0041] S102: Heat-treat the first wire blank in a flowing air atmosphere. The heat-treatment temperature is 450 °C and the heat-treatment time is 25 h. The additive decomposes upon heating during the heat treatment to produce the second wire blank. The second wire blank has a core material, a β-phase copper-zinc alloy layer, and a surface layer from the inside out.

[0042] S103: Perform multi-mode continuous stretching and stress-relieving annealing on the second wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm.

[0043] Measure the surface carbon content of the electrode wire prepared by the above process using an electron scanning electron microscope and an energy spectrometer. Measure the surface carbon content at 10 different locations and take the average value as the surface carbon content of the electrode wire. Also determine the conductivity and surface adhesion of the electrode wire prepared by the above process. The test results are shown in Table 1.

[0044] Test the electrode wire prepared by the above process using an Archie E350 machine. The workpiece material for testing is 8407, the workpiece size is 6 mm (length) * 6 mm (width) * 50 mm (thickness), and the number of machining passes for testing is selected as "one cut and four repairs". The test results are shown in Table 2.

[0045] Example 3:

[0046] Prepare the slow wire electrical discharge machining electrode wire for this example using the following process:

[0047] S100: Provide a CuZn40 brass bus bar with a wire diameter specification of 1 mm;

[0048] S101: Galvanize the surface of the bus bar using an electroplating solution containing additives to form a 5-μm galvanized layer on the surface of the bus bar, producing a first wire blank. The additives are one or a mixture of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additives in the electroplating solution is 20 g / L;

[0049] S102: Perform heat treatment on the first wire blank in a flowing air atmosphere. The heat treatment temperature is 175 °C and the heat treatment time is 30 h. The additives decompose during the heat treatment to produce a second wire blank. The second wire blank has a core material, a γ-phase copper-zinc alloy layer, and a surface layer from the inside out;

[0050] S103: Perform multi-mode continuous stretching and stress-relieving annealing on the second wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm.

[0051] Measure the surface carbon content of the electrode wire prepared by the above process using an electron scanning electron microscope and an energy spectrometer. Measure the surface carbon content at 10 different locations and take the average value as the surface carbon content of the electrode wire. Also determine the conductivity and surface adhesion of the electrode wire prepared by the above process. The test results are shown in Table 1.

[0052] The electrode wire prepared by the above process was tested by the Aqi E350 machine. The test workpiece material was 8407, the test workpiece size was 6mm (length) * 6mm (width) * 50mm (thickness), and the test processing knife number was "cut four repairs". The test results are shown in Table 2.

[0053] Embodiment 4:

[0054] The electrode wire for wire-cut electrospark machining in this embodiment is prepared by the following process:

[0055] S200: Provides CuZn40 brass busbar with a wire diameter of 1.2mm;

[0056] S201: using an electroplating solution containing an additive to zinc-plate the surface of the busbar, thereby forming a 25 μm zinc-plated layer on the surface of the busbar to prepare a first wire blank, wherein the additive is a mixture of one or more of oligofructose, sorbitol, dextrin, sucrose, lactose and maltose, and the concentration of the additive in the electroplating solution is 24 g / L;

[0057] S202: performing multi-mode continuous stretching on the first wire blank to produce a second wire blank, wherein the wire diameter specification of the second wire blank is 0.55 mm;

[0058] S203: heat treating the second wire blank in a flowing air atmosphere at a temperature of 450° C. for 35 hours, wherein the organic additive is thermally decomposed during the heat treatment process to form a third wire blank, wherein the third wire blank has a core material, a β-phase copper-zinc alloy layer, and a surface layer in order from the inside to the outside;

[0059] S204: performing multi-mode continuous stretching and stress relief annealing on the third wire blank to produce a finished electrode wire with a wire diameter of 0.25 mm.

[0060] The electrode wire prepared by the above process was used to measure the carbon content on the surface of the electrode wire using an electron scanning electron microscope and an energy spectrometer. The surface carbon content of 10 different parts was measured and the average value was taken as the surface carbon content of the electrode wire. The conductivity and surface adhesion of the electrode wire prepared by the above process were also determined. The test results are shown in Table 1.

[0061] The electrode wire prepared by the above process was tested by the Aqi E350 machine. The test workpiece material was 8407, the test workpiece size was 6mm (length) * 6mm (width) * 50mm (thickness), and the test processing knife number was "cut four repairs". The test results are shown in Table 2.

[0062] Embodiment 5:

[0063] The electrode wire for wire-cut electrospark machining in this embodiment is prepared by the following process:

[0064] S200: Provide a CuZn37 brass busbar with a wire diameter specification of 0.95 mm;

[0065] S201: Zinc plate the surface of the busbar using an electroplating solution containing additives, thereby plating and forming a 15-μm zinc coating on the surface of the busbar to produce a first wire blank, wherein the additive is one or a mixture of multiple of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 22 g / L;

[0066] S202: Perform multi-mode continuous drawing on the first wire blank to produce a second wire blank with a wire diameter specification of 0.5 mm;

[0067] S203: Under a flowing air atmosphere, perform heat treatment on the second wire blank at a heat treatment temperature of 350 °C for a heat treatment time of 35 h. The organic additive decomposes upon heating during the heat treatment to produce a third wire blank, and the third wire blank sequentially has a core material, a β-phase copper-zinc alloy layer, and a surface layer from the inside out;

[0068] S204: Perform multi-mode continuous drawing and stress relief annealing on the third wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm.

[0069] Measure the surface carbon content of the electrode wire prepared by the above process using an electron scanning electron microscope and an energy spectrometer. Measure the surface carbon content at 10 different positions and take the average value as the surface carbon content of the electrode wire. And determine the conductivity and surface adhesion of the electrode wire prepared by the above process. The test results are shown in Table 1.

[0070] Test the electrode wire prepared by the above process using an Archie E350 machine. The test workpiece material is 8407, the test workpiece size is 6 mm (length) * 6 mm (width) * 50 mm (thickness), and the test machining tool passes are selected as "one cut and four repairs". The test results are shown in Table 2.

[0071] Example 6:

[0072] Prepare the slow wire electrical discharge machining electrode wire of this example using the following process:

[0073] S200: Provide a CuZn37 brass busbar with a wire diameter specification of 0.7 mm;

[0074] S201: Zinc plate the surface of the busbar using an electroplating solution containing additives, thereby plating and forming an 8-μm zinc coating on the surface of the busbar to produce a first wire blank, wherein the additive is one or a mixture of multiple of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 12 g / L;

[0075] S202: Continuously stretch the first wire blank through multiple dies to produce a second wire blank with a wire diameter specification of 0.4 mm.

[0076] S203: Heat-treat the second wire blank in a flowing air atmosphere at a heat-treatment temperature of 150 °C for 30 h. The organic additive decomposes upon heating during the heat treatment to produce a third wire blank. The third wire blank has a core material, a γ-phase copper-zinc alloy layer, and a surface layer from the inside out.

[0077] S204: Continuously stretch the third wire blank through multiple dies and perform stress relief annealing to produce a finished electrode wire with a wire diameter specification of 0.25 mm.

[0078] Measure the surface carbon content of the electrode wire prepared by the above process using an electron scanning electron microscope and an energy spectrometer. Measure the surface carbon content at 10 different positions and take the average value as the surface carbon content of the electrode wire. Also determine the conductivity and surface adhesion of the electrode wire prepared by the above process. The test results are shown in Table 1.

[0079] Test the electrode wire prepared by the above process using an Archie E350 machine. The workpiece material for testing is 8407, the workpiece size is 6 mm (length) * 6 mm (width) * 50 mm (thickness), and the test machining tool passes are selected as "one cut and four repairs". The test results are shown in Table 2.

[0080] Comparative Example 1: Prepare the electrode wire for slow wire electrical discharge machining in Comparative Example 1 using the following process:

[0081] S100: Provide a CuZn40 brass bus bar with a wire diameter specification of 0.5 mm.

[0082] S101: Galvanize the surface of the bus bar using an electroplating solution containing an additive to form a 35-μm galvanized layer on the surface of the bus bar to produce a first wire blank. The additive is one or a mixture of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 25 g / L.

[0083] S102: Heat-treat the first wire blank in a flowing air atmosphere at a heat-treatment temperature of 450 °C for 25 h to produce a second wire blank. The second wire blank has a core material, a β-phase copper-zinc alloy layer, and a surface layer from the inside out.

[0084] S103: Continuously stretch the second wire blank through multiple dies and perform stress relief annealing treatment to produce a finished electrode wire with a wire diameter specification of 0.25 mm.

[0085] Comparative Example 2: Prepare the electrode wire for slow wire electrical discharge machining in Comparative Example 2 using the following process:

[0086] S100: Provide a CuZn40 brass busbar with a wire diameter specification of 1 mm;

[0087] S101: Galvanize the surface of the busbar using a plating solution containing additives to form a 2-μm thick galvanized layer on the surface of the busbar, thereby producing a first wire blank. The additives are one or a mixture of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additives in the plating solution is 6 g / L;

[0088] S102: Heat-treat the first wire blank in a flowing air atmosphere at a heat-treatment temperature of 175 °C for 30 h to produce a second wire blank. The second wire blank sequentially has a core material, a γ-phase copper-zinc alloy layer, and a surface layer from the inside out;

[0089] S103: Perform multi-mode continuous drawing and stress-relieving annealing on the second wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm.

[0090] Comparative Example 3: Prepare an electrode wire for slow wire electrical discharge machining in Comparative Example 3 using the following process:

[0091] S200: Provide a CuZn37 brass busbar with a wire diameter specification of 0.95 mm;

[0092] S201: Galvanize the surface of the busbar using a plating solution containing additives to form a 28-μm thick galvanized layer on the surface of the busbar, thereby producing a first wire blank. The additives are one or a mixture of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additives in the plating solution is 35 g / L;

[0093] S202: Perform multi-mode continuous drawing on the first wire blank to produce a second wire blank with a wire diameter specification of 0.5 mm;

[0094] S203: Heat-treat the second wire blank in a flowing air atmosphere at a heat-treatment temperature of 350 °C for 35 h to produce a third wire blank. The third wire blank sequentially has a core material, a β-phase copper-zinc alloy layer, and a surface layer from the inside out;

[0095] S204: Perform multi-mode continuous drawing and stress-relieving annealing on the third wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm.

[0096] The electrode wires of Comparative Examples 1-3 above were measured for the surface carbon content using an electron scanning electron microscope and an energy spectrometer. The surface carbon content of 10 different parts of each electrode wire was measured, and the average value was taken as the surface carbon content of the corresponding electrode wire. And the conductivity and surface adhesion of the electrode wires prepared in Comparative Examples 1-3 above were determined. The test results are shown in Table 1.

[0097] The electrode wires prepared in Comparative Examples 1-3 above were tested using an Archie E350 machine. The workpiece material for the test was 8407, the workpiece size was 6 mm (length) * 6 mm (width) * 50 mm (thickness), and the test machining tool passes were selected as "one cut and four repairs". The test results are shown in Table 2.

[0098] According to the analysis of the test results, the surface carbon content of the electrode wire of the present invention is in the range of 0.2-60 wt%, and it has a high cutting speed, high cutting processing accuracy and tight surface adhesion. When the surface carbon content of the electrode wire is less, the conductivity of the electrode wire is lower, and the cutting speed and cutting processing accuracy are lower. When the surface carbon content of the electrode wire exceeds the relevant range, the cutting speed will also decrease, and the surface layer will show a peeling phenomenon.

[0099] Comparative Example 1: A brass electrode wire with a wire diameter specification of 0.25 mm obtained by procurement;

[0100] Comparative Example 2: A composite coated electrode wire with a wire diameter specification of 0.25 mm obtained by procurement;

[0101] Comparative Example 3: A γ-coated electrode wire with a wire diameter specification of 0.25 mm obtained by procurement.

[0102] Determine the conductivity of the electrode wires prepared by the processes of Comparative Examples 1-3 above. The test results are shown in Table 1.

[0103] The electrode wires prepared by the processes of Comparative Examples 1-3 above were tested using an Archie E350 machine. The workpiece material for the test was 8407, the workpiece size was 6 mm (length) * 6 mm (width) * 50 mm (thickness), and the test machining tool passes were selected as "one cut and four repairs". The test results are shown in Table 2.

[0104] According to the analysis of the test results, the electrode wire of the present invention has more excellent cutting processing speed and cutting processing accuracy compared with conventional brass wires and coated wires.

[0105] Table 1: Test results of surface carbon content, conductivity and surface adhesion of electrode wires in examples, comparative examples and comparative cases

[0106]

[0107]

[0108] Table 2: Test Results of Electrode Wire Cutting Processing Speed and Cutting Processing Precision for Examples, Comparative Examples, and Control Examples

[0109]

[0110] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A wire electrode for slow wire electrical discharge machining, comprising: A core material; An intermediate layer, which is located outside the core material; And A surface layer, which is located outside the intermediate layer; Wherein, the core material is a metal or an alloy, the intermediate layer is a copper-zinc alloy, and the surface layer contains carbon elements; It is characterized in that the carbon element content on the surface of the wire electrode is 0.2-60 wt%; at least part of the carbon element in the surface layer exists in the form of elemental carbon.

2. The wire electrode for slow wire electrical discharge machining according to claim 1, characterized in that, The carbon element content on the surface of the wire electrode is 1-20 wt%.

3. The wire electrode for slow wire electrical discharge machining according to claim 1, characterized in that, The elemental carbon includes graphite and / or amorphous carbon.

4. The wire electrode for slow wire electrical discharge machining according to any one of claims 1-3, characterized in that, The surface layer discontinuously covers the outside of the intermediate layer, and the intermediate layer and / or the core material are exposed at the discontinuities of the surface layer.

5. The wire electrode for slow wire electrical discharge machining according to any one of claims 1-3, characterized in that, The intermediate copper-zinc alloy is at least one of β-phase copper-zinc alloy, β ’ '-phase copper-zinc alloy, and γ-phase copper-zinc alloy.

6. The wire electrode for slow wire electrical discharge machining according to any one of claims 1-3, characterized in that, The intermediate layer has cracks.

7. The wire electrode for slow wire electrical discharge machining according to any one of claims 1-3, characterized in that, The core material is copper or a copper alloy.

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