Electrode wire for low-speed wire electric discharge machining

Abstract

The present invention discloses an electrode wire for low-speed wire electric discharge machining, the electrode wire for low-speed wire electric discharge machining including a core material, an intermediate layer located outside the core material, and a surface layer located outside the intermediate layer, the core material being a metal or alloy, the intermediate layer being a copper-zinc alloy, and the surface layer containing elemental carbon, the carbon content of the surface of the low-speed wire electric discharge machining electrode being 0.2 to 60 wt%. The electrode wire for low-speed wire electric discharge machining of the present invention has excellent electrical conductivity in the surface layer, can maintain a high cutting speed for a long time, has high machining accuracy, and is manufactured using a simple process.

Description

[Technical Field]

[0001] The present invention is in the field of electric spark wire-cut electrical discharge machining, and more particularly relates to an electrode wire for low speed wire electrical discharge machining. [Background technology]

[0002] The basic operating principle of wire-cut electrical discharge machining (WEDM) is to use a continuously moving, thin metal wire as an electrode to generate pulsed spark discharges on the workpiece to corrode and remove metal, resulting in cutting and shaping. When using wire-cut electrical discharge machining, the workpiece is connected to the positive pole of a pulsed power supply, and the wire electrode is connected to the negative pole of a high-frequency pulsed power supply as the tool electrode. The pulsed power supply provides the machining energy, and a dedicated wire-cut working fluid is used to remove the debris generated during the machining process. When energized, a strong electric field causes the surfaces of the positive and negative electrodes to be bombarded with electron and ion flows, respectively. This creates an instantaneous high-temperature heat source in the gap between the workpiece and the wire electrode, melting and vaporizing the local metal, forming corrosion pits on the wire electrode and workpiece, and evaporating the working fluid. The vaporized working fluid and the vapor of the workpiece material expand rapidly and instantaneously, and the combined action of this thermal expansion and the washing of the working fluid expels the molten and vaporized workpiece material from the discharge gap, completing one spark discharge process. The above spark discharge process is repeated to cut and shape the workpiece.

[0003] The process parameters of electric spark wire EDM, such as cutting speed, cutting accuracy, and surface finish of the workpiece after machining, are not only affected by the electric spark wire EDM equipment, but are also closely related to the performance of the electrode wire used.

[0004] During the technological development process, electrode wire for electric spark wire cut EDM has undergone four generations of product updates and development: pure copper wire, brass wire, galvanized wire, and covered wire. Covered wire is made by plating the surface of the electrode wire with a certain thickness of a high-zinc alloy layer (i.e., an alloy layer with a high zinc content). Utilizing the properties of the high-zinc alloy, it achieves higher vaporization pressure, which helps improve machining speed. Based on the composition of the plated high-zinc alloy, covered wire is classified into gamma-covered wire, beta-covered wire, and composite-covered wire. Covered wire is one of the most widely used types of electrode wire today.

[0005] However, certain defects still exist in the practical application of coated wire in manufacturing and processing: the high-zinc alloy surface layer is easily melted and vaporized, and has low electrical discharge corrosion resistance, so that the high-zinc alloy surface layer is quickly consumed during electric spark wire-cut electrical discharge machining, making it difficult for the surface layer to function for a long time, and as the high-zinc alloy surface layer disappears, the cutting speed and cutting accuracy also decrease. Summary of the Invention

[0006] The present invention aims to solve at least to some extent one of the technical problems in the related art by providing an electrode wire for low-speed wire electric discharge machining, which has an excellent surface layer conductivity, can maintain a high cutting speed for a long time, has high cutting accuracy, and is manufactured by a simple process.

[0007] According to one aspect of the present invention, there is provided an electrode wire for low-speed wire electric 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 alloy, the intermediate layer is a copper-zinc alloy, the surface layer contains carbon, and the carbon content of the surface of the electrode wire for low-speed wire electric discharge machining is 0.2 to 60 wt %.

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

[0009] 1. The surface layer of the electrode wire for low-speed wire EDM of the present invention contains carbon elements and has high conductivity, which improves the current transmission efficiency of the electrode wire during electric spark discharge machining and increases the cutting speed.

[0010] 2. The surface layer of the electrode wire for low-speed wire EDM of the present invention contains carbon, which has a high melting point, so that the surface of the electrode wire has high discharge corrosion resistance, and during electric spark discharge machining, the surface layer of the electrode wire maintains a relatively stable structure for a long time, ensuring that the surface layer of the electrode wire can function for a long time and maintaining a high cutting speed of the electrode wire. Furthermore, the high discharge corrosion resistance of the electrode wire surface can maintain a more stable discharge gap between the electrode wire and the workpiece during electric spark discharge machining, achieving a more uniform and stable discharge intensity and improving the cutting precision of the workpiece.

[0011] 3. By limiting the carbon element content on the surface of the electrode wire for low-speed wire EDM of the present invention to a range of 0.2 to 60 wt%, it is possible to ensure that the electrode wire has a high cutting speed, achieve both high cutting speed and high cutting accuracy, and ensure ease of production and manufacturing of the electrode wire. Carbon has a high melting point and a high vaporization temperature, making it difficult to vaporize during electric spark discharge machining. Increasing the carbon element content on the surface of the electrode wire improves the electrical conductivity of the electrode wire and is advantageous for increasing the cutting speed. However, a decrease in the content of easily vaporizable components on the surface of the electrode wire reduces the vaporization cleaning effect on the surface, adversely affecting the cutting speed. Furthermore, if the surface carbon element content is too high, the structure of the surface layer of the electrode wire is prone to peeling, making it more difficult to produce and process the electrode wire.

[0012] Preferably, the carbon element content in the surface of the low-speed wire electrode for electrical discharge machining is 1 to 20 wt%. By limiting the carbon element content in the surface of the wire electrode within this range, high cutting speed and high cutting accuracy can be ensured when electric spark discharge machining is performed using the wire electrode. Specifically, the carbon element content in the surface of the low-speed wire electrode for electrical discharge machining may be 1 to 15 wt%, 1 to 10 wt%, 1.5 to 20 wt%, 1.5 to 15 wt%, or 1.5 to 10 wt%.

[0013] Preferably, the carbon element in the surface layer is at least partially present as elemental carbon, which has high electrical conductivity and a high melting point, and the presence of the carbon element in the surface layer as elemental carbon is advantageous in further improving the electrical conductivity of the electrode wire and the discharge corrosion resistance of the surface, thereby improving the cutting speed and cutting accuracy.

[0014] Preferably, the carbon element contains graphite and / or amorphous carbon. Graphite and amorphous carbon have excellent electrical conductivity, and an electrode wire whose surface layer contains graphite and / or amorphous carbon has a higher cutting speed.

[0015] Preferably, the surface layer intermittently covers the outside of the intermediate layer, and the intermediate layer and / or the core material are exposed through the cutouts in the surface layer. Because the surface layer intermittently covers the outside of the intermediate layer, a tip is formed in the cutouts in the surface layer. Because the tip is more likely to discharge, the reaction time for the electrode wire to generate an electric spark during electric discharge machining can be shortened, thereby further improving the cutting speed of the electric spark wire. Furthermore, the exposed intermediate layer or core material can further improve the electrical conductivity of the surface layer, which is advantageous for improving the transmission of discharge energy and further improving the cutting speed.

[0016] Preferably, the copper-zinc alloy of the intermediate layer is at least one of a β-phase copper-zinc alloy, a β'-phase copper-zinc alloy, and a γ-phase copper-zinc alloy. β-phase copper-zinc alloys and β'-phase copper-zinc alloys have high electrical conductivity, improving discharge efficiency and further increasing cutting speed. γ-phase copper-zinc alloys have a high zinc content, demonstrating a clear vaporization cleaning effect during electric spark wire cutting and also advantageous for improving cutting speed. The β'-phase can remain stable below a certain temperature and has an ordered lattice. Above this temperature, the β'-phase transforms into an irregular β-phase. Generally, the transformation between the β and β' phases cannot be suppressed, but has little effect on mechanical and electrical properties. Therefore, in the context of this application, unless clearly distinguished, a reference to the "β-phase" also refers to the "β'-phase."

[0017] Preferably, the intermediate layer has cracks. Since the cracks form tips that are more likely to discharge, the reaction time for the electrode wire to generate an electric spark during wire-cut electrical discharge machining can be shortened, thereby improving the cutting speed of the wire. Furthermore, the cracks also increase the contact area between the electrode wire and the working fluid, thereby improving the cutting speed. Therefore, after the surface layer is completely consumed, the cracked structure of the intermediate layer can further improve the cutting speed.

[0018] Preferably, the core material is copper or a copper alloy, which has excellent electrical conductivity, and the use of such a core material ensures that the electrode wire has excellent performance.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of energy spectrum measurement using a scanning electron microscope of the carbon content on the surface of the electrode wire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, the embodiments of the present invention will be described in detail. The embodiments described below with reference to the drawings are illustrative and are intended to interpret the present invention, but should not be understood as limiting the present invention.

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0023] Before describing specific embodiments, the components, structural features, and a method for measuring the contents of related components of the electrode wire for low-speed wire electric discharge machining according to the present invention will be described.

[0024] When manufacturing bus bars, brass bus bars are generally used, specifically CuZn37 brass or CuZn40 brass. Bus bars may also be manufactured using tough pitch copper (i.e., pure copper), copper alloys other than brass, or other metals or alloys.

[0025] The carbon content of the surface of the electrode wire in the present invention refers to the carbon element content of the outermost surface portion of the electrode wire in the circumferential direction that comes into contact with the environment. The surface of the electrode wire here differs from the surface layer of the electrode wire, which is a layer structure having a certain thickness at the outermost portion of the electrode wire, and the outermost portion of the surface layer that comes into contact with the environment constitutes part or all of the surface of the electrode wire.

[0026] The carbon content on the surface of an electrode wire can be measured using methods known in the art for measuring elemental components. In an embodiment of the present invention, the carbon content on the surface of an electrode wire is measured using a scanning electron microscope (SEM) for energy spectroscopy. Specifically, as shown in FIG. 1, a conventional laboratory SEM and energy spectrometer are used to place an electrode wire sample in a sample chamber. A rectangular measurement area is selected from the surface of the electrode wire displayed by the SEM and subjected to energy spectroscopy. The rectangular area has a short side length of 1 to 2 times the radius of the electrode wire and a long side length of 1 to 5 times the short side length. The distribution of elements in different regions of the same electrode wire is not necessarily the same. Therefore, the carbon content of multiple different regions of the same electrode wire is measured using the above method, and the average of the carbon contents in each region is used to determine the carbon content on the surface of the electrode wire. In the following embodiment of the present invention, 10 different regions of the same electrode wire are selected, and the carbon content on the surface of each region is measured using the above SEM energy spectroscopy. The average of the 10 carbon contents obtained is then used as the carbon content on the surface of the corresponding electrode wire.

[0027] The carbon content of the electrode wire surface is within the range of 0.2 to 60 wt%. If the carbon content of the electrode wire surface is too low, the carbon content, which has high conductivity and melting point, is low, and the role of improving the current transmission efficiency of the electrode wire during electric spark discharge machining (ESD), improving the cutting speed, and maintaining the surface layer's function for a long time and improving the cutting accuracy is unclear. On the other hand, if the carbon content of the electrode wire surface is too high, the high melting point and high vaporization temperature of carbon significantly reduce the vaporization cleaning effect of the electrode wire surface, reducing the cutting speed. If the surface carbon content is too high, the structure of the surface layer of the electrode wire is easily peeled off, making the production and processing of the electrode wire more difficult. Controlling the carbon content of the electrode wire surface within the above range ensures that the electrode wire has a high cutting speed, achieving both high cutting speed and high cutting accuracy, and ensuring ease of production and manufacturing of the electrode wire.

[0028] The β' phase can maintain a stable state below a certain temperature and has an ordered lattice. Above that temperature, the β' phase transforms into a disordered β phase. Generally, the transformation between the β and β' phases cannot be suppressed, but the impact on mechanical and electrical properties is small. For ease of explanation, the following examples will be expressed as the β phase, and any reference to the β phase also refers to the β' phase. In other words, the β phase below refers to one or both of the β and β' phases.

[0029] Example 1 The electrode wire for low-speed wire electric discharge machining of this embodiment is: Step S100 provides a CuZn37 brass bus bar having a wire diameter of 1.2 mm; Step S101: plating a surface of the bus bar with zinc using an electroplating solution containing an additive to form a 10 μm zinc plating layer on the surface of the bus bar, wherein the additive is a mixture of one or more of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 15 g / L; Step S102: heat-treating the first wire blank in a flowing air atmosphere at a heat treatment temperature of 240°C for 45 hours, so that the additive is decomposed by heat during the heat treatment, thereby producing a second wire blank having, from the inside to the outside, a core material, a β-phase copper-zinc alloy layer, a γ-phase copper-zinc alloy layer, and a surface layer in this order; and step S103 of subjecting the second wire blank to a multi-mode continuous tensile and stress annealing process to produce a finished electrode wire having a wire diameter of 0.25 mm.

[0030] The carbon content of the electrode wire surface manufactured by the above process was measured using a scanning electron microscope and an energy spectrometer. The carbon content of the surface of 10 different locations was measured, and the average value was taken as the carbon content of the electrode wire surface. The electrical conductivity and adhesion state of the surface layer of the electrode wire manufactured by the above process were also measured. The measurement results are shown in Table 1.

[0031] The electrode wire manufactured by the above process was measured using an Agie E350 machine. The material of the measured workpiece was 8407, the dimensions of the measured workpiece were 6 mm (length) x 6 mm (width) x 50 mm (thickness), and the number of measuring cuts was selected as "1 cut and 4 trimmings." The measurement results are shown in Table 2.

[0032] Example 2 The electrode wire for low-speed wire electric discharge machining of this embodiment is: Step S100 provides a CuZn40 brass bus bar having a wire diameter of 0.5 mm; Step S101: plating a surface of the bus bar with zinc using an electroplating solution containing an additive to form a 20 μm zinc plating layer on the surface of the bus bar, wherein the additive is a mixture of one or more of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 10 g / L; Step S102: heat-treating the first wire blank in a flowing air atmosphere at a heat treatment temperature of 450°C for 25 hours, so that the additive is decomposed by heat during the heat treatment, thereby producing a second wire blank having, from the inside to the outside, a core material, a β-phase copper-zinc alloy layer, and a surface layer in this order; and step S103 of subjecting the second wire blank to a multi-mode continuous tensile and stress annealing process to produce a finished electrode wire having a wire diameter of 0.25 mm.

[0033] The carbon content of the electrode wire surface manufactured by the above process was measured using a scanning electron microscope and an energy spectrometer. The carbon content of the surface of 10 different locations was measured, and the average value was taken as the carbon content of the electrode wire surface. The electrical conductivity and adhesion state of the surface layer of the electrode wire manufactured by the above process were also measured. The measurement results are shown in Table 1.

[0034] The electrode wire manufactured by the above process was measured using an Agie E350 machine. The material of the measured workpiece was 8407, the dimensions of the measured workpiece were 6 mm (length) x 6 mm (width) x 50 mm (thickness), and the number of measuring cuts was selected as "1 cut and 4 trimmings." The measurement results are shown in Table 2.

[0035] Example 3 The electrode wire for low-speed wire electric discharge machining of this embodiment is: Step S100 provides a CuZn40 brass bus bar having a wire diameter of 1 mm; Step S101: plating a surface of the bus bar with zinc using an electroplating solution containing an additive to form a 5 μm zinc plating layer on the surface of the bus bar, wherein the additive is a mixture of one or more of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 20 g / L; Step S102: heat-treating the first wire blank in a flowing air atmosphere at a heat treatment temperature of 175°C for 30 hours, so that the additive is decomposed by heat during the heat treatment, thereby producing a second wire blank having, from the inside to the outside, a core material, a γ-phase copper-zinc alloy layer, and a surface layer in this order; and step S103 of subjecting the second wire blank to a multi-mode continuous tensile and stress annealing process to produce a finished electrode wire having a wire diameter of 0.25 mm.

[0036] The carbon content of the electrode wire surface manufactured by the above process was measured using a scanning electron microscope and an energy spectrometer. The carbon content of the surface of 10 different locations was measured, and the average value was taken as the carbon content of the electrode wire surface. The electrical conductivity and adhesion state of the surface layer of the electrode wire manufactured by the above process were also measured. The measurement results are shown in Table 1.

[0037] The electrode wire manufactured by the above process was measured using an Agie E350 machine. The material of the measured workpiece was 8407, the dimensions of the measured workpiece were 6 mm (length) x 6 mm (width) x 50 mm (thickness), and the number of measuring cuts was selected as "1 cut and 4 trimmings." The measurement results are shown in Table 2.

[0038] Example 4 The electrode wire for low-speed wire electric discharge machining of this embodiment is: Step S200 provides a CuZn40 brass bus bar having a wire diameter of 1.2 mm; Step S201: plating a surface of the bus bar with zinc using an electroplating solution containing an additive to form a 25 μm zinc plating layer on the surface of the bus bar, wherein the additive is a mixture of one or more of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 24 g / L; Step S202: subjecting the first wire blank to multimode continuous drawing to produce a second wire blank having a wire diameter of 0.55 mm; Step S203: heat-treating the second wire blank in a flowing air atmosphere at a heat treatment temperature of 450°C for 35 hours, so that the additive is decomposed by heat during the heat treatment, thereby producing a third wire blank having, from the inside to the outside, a core material, a β-phase copper-zinc alloy layer, and a surface layer in this order; and step S204 of subjecting the third wire blank to a multi-mode continuous tensile and stress annealing treatment to produce a finished electrode wire having a wire diameter specification of 0.25 mm.

[0039] The carbon content of the electrode wire surface manufactured by the above process was measured using a scanning electron microscope and an energy spectrometer. The carbon content of the surface of 10 different locations was measured, and the average value was taken as the carbon content of the electrode wire surface. The electrical conductivity and adhesion state of the surface layer of the electrode wire manufactured by the above process were also measured. The measurement results are shown in Table 1.

[0040] The electrode wire manufactured by the above process was measured using an Agie E350 machine. The material of the measured workpiece was 8407, the dimensions of the measured workpiece were 6 mm (length) x 6 mm (width) x 50 mm (thickness), and the number of measuring cuts was selected as "1 cut and 4 trimmings." The measurement results are shown in Table 2.

[0041] Example 5 The electrode wire for low-speed wire electric discharge machining of this embodiment is: Step S200 provides a CuZn37 brass bus bar having a wire diameter of 0.95 mm; Step S201: plating a surface of the bus bar with zinc using an electroplating solution containing an additive to form a 15 μm zinc plating layer on the surface of the bus bar, wherein the additive is a mixture of one or more of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 22 g / L; Step S202: subjecting the first wire blank to multimode continuous drawing to produce a second wire blank having a wire diameter of 0.5 mm; Step S203: heat-treating the second wire blank in a flowing air atmosphere at a heat treatment temperature of 350°C for 35 hours, so that the additive is decomposed by heat during the heat treatment, thereby producing a third wire blank having, from the inside to the outside, a core material, a β-phase copper-zinc alloy layer, and a surface layer in this order; and step S204 of subjecting the third wire blank to a multi-mode continuous tensile and stress annealing treatment to produce a finished electrode wire having a wire diameter specification of 0.25 mm.

[0042] The carbon content of the electrode wire surface manufactured by the above process was measured using a scanning electron microscope and an energy spectrometer. The carbon content of the surface of 10 different locations was measured, and the average value was taken as the carbon content of the electrode wire surface. The electrical conductivity and adhesion state of the surface layer of the electrode wire manufactured by the above process were also measured. The measurement results are shown in Table 1.

[0043] The electrode wire manufactured by the above process was measured using an Agie E350 machine. The material of the measured workpiece was 8407, the dimensions of the measured workpiece were 6 mm (length) x 6 mm (width) x 50 mm (thickness), and the number of measuring cuts was selected as "1 cut and 4 trimmings." The measurement results are shown in Table 2.

[0044] Example 6 The electrode wire for low-speed wire electric discharge machining of this embodiment is: Step S200 provides a CuZn37 brass bus bar having a wire diameter of 0.7 mm; Step S201: plating a surface of the bus bar with zinc using an electroplating solution containing an additive to form a zinc plating layer of 8 μm on the surface of the bus bar, wherein the additive is a mixture of one or more of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 12 g / L; Step S202: subjecting the first wire blank to multimode continuous drawing to produce a second wire blank having a wire diameter of 0.4 mm; Step S203: heat-treating the second wire blank in a flowing air atmosphere at a heat treatment temperature of 150°C for 30 hours, so that the additive is decomposed by heat during the heat treatment, thereby producing a third wire blank having, from the inside to the outside, a core material, a γ-phase copper-zinc alloy layer, and a surface layer in this order; and step S204 of subjecting the third wire blank to a multi-mode continuous tensile and stress annealing treatment to produce a finished electrode wire having a wire diameter specification of 0.25 mm.

[0045] The carbon content of the electrode wire surface manufactured by the above process was measured using a scanning electron microscope and an energy spectrometer. The carbon content of the surface of 10 different locations was measured, and the average value was taken as the carbon content of the electrode wire surface. The electrical conductivity and adhesion state of the surface layer of the electrode wire manufactured by the above process were also measured. The measurement results are shown in Table 1.

[0046] The electrode wire manufactured by the above process was measured using an Agie E350 machine. The material of the measured workpiece was 8407, the dimensions of the measured workpiece were 6 mm (length) x 6 mm (width) x 50 mm (thickness), and the number of measuring cuts was selected as "1 cut and 4 trimmings." The measurement results are shown in Table 2.

[0047] (Control Example 1) The electrode wire for low-speed wire electric discharge machining of Comparative Example 1 is Step S100 provides a CuZn40 brass bus bar having a wire diameter of 0.5 mm; Step S101: plating a surface of the bus bar with zinc using an electroplating solution containing an additive to form a 35 μm zinc plating layer on the surface of the bus bar, wherein the additive is a mixture of one or more of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 25 g / L; Step S102: heat-treating the first wire blank in a flowing air atmosphere at a heat treatment temperature of 450°C for 25 hours to produce a second wire blank having, from the inside to the outside, a core material, a β-phase copper-zinc alloy layer, and a surface layer; and step S103 of subjecting the second wire blank to a multi-mode continuous tensile and stress annealing process to produce a finished electrode wire having a wire diameter of 0.25 mm.

[0048] (Control Example 2) The electrode wire for low-speed wire electric discharge machining of Comparative Example 2 is Step S100 provides a CuZn40 brass bus bar having a wire diameter of 1 mm; Step S101: plating a surface of the bus bar with zinc using an electroplating solution containing an additive to form a 2 μm zinc plating layer on the surface of the bus bar, wherein the additive is a mixture of one or more of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 6 g / L; Step S102: heat-treating the first wire blank in a flowing air atmosphere at a heat treatment temperature of 175°C for 30 hours to produce a second wire blank having, from the inside to the outside, a core material, a γ-phase copper-zinc alloy layer, and a surface layer; and step S103 of subjecting the second wire blank to a multi-mode continuous tensile and stress annealing process to produce a finished electrode wire having a wire diameter of 0.25 mm.

[0049] (Control Example 3) The electrode wire for low-speed wire electric discharge machining of Comparative Example 3 is Step S200 provides a CuZn37 brass bus bar having a wire diameter of 0.95 mm; Step S201: plating a surface of the bus bar with zinc using an electroplating solution containing an additive to form a 28 μm zinc plating layer on the surface of the bus bar, wherein the additive is a mixture of one or more of fructooligosaccharide, sorbitol, dextrin, sucrose, lactose, and maltose, and the concentration of the additive in the electroplating solution is 35 g / L; Step S202: subjecting the first wire blank to multimode continuous drawing to produce a second wire blank having a wire diameter of 0.5 mm; Step S203: heat-treating the second wire blank in a flowing air atmosphere at a heat treatment temperature of 350°C for 35 hours to produce a third wire blank having, from the inside to the outside, a core material, a β-phase copper-zinc alloy layer, and a surface layer; and step S204 of subjecting the third wire blank to a multi-mode continuous tensile and stress annealing treatment to produce a finished electrode wire having a wire diameter specification of 0.25 mm.

[0050] The carbon content of the electrode wires of Comparative Examples 1 to 3 was measured using a scanning electron microscope and an energy spectrometer. The carbon content of the surface of each electrode wire was measured at 10 different locations, and the average value was taken as the carbon content of the surface of the corresponding electrode wire. The electrical conductivity and adhesion state of the surface layer of the electrode wires manufactured in Comparative Examples 1 to 3 were measured. The measurement results are shown in Table 1.

[0051] The electrode wires manufactured in the above Comparative Examples 1 to 3 were measured using an E350 machine manufactured by Agie Co., Ltd. The material of the measured workpiece was 8407, the dimensions of the measured workpiece were 6 mm (length) x 6 mm (width) x 50 mm (thickness), and the number of measuring cutting edges was selected as "1 cut and 4 trimmings." The measurement results are shown in Table 2.

[0052] Analysis of the measurement results shows that the electrode wire of the present invention has a surface carbon content in the range of 0.2 to 60 wt%, and has high cutting speed, high cutting accuracy, and excellent surface adhesion. If the surface carbon content of the electrode wire is low, the electrical conductivity of the electrode wire is low, and the cutting speed and cutting accuracy are also low. If the surface carbon content of the electrode wire exceeds the corresponding range, the cutting speed also decreases and the surface layer peels off.

[0053] Comparative Example 1: Purchased brass electrode wire with a wire diameter of 0.25 mm Comparative Example 2: Purchased coated electrode wire with a wire diameter of 0.25 mm Comparative Example 3: Purchased gamma-coated electrode wire with a wire diameter of 0.25 mm The electrical conductivity of the electrode wires manufactured by the processes of Comparative Examples 1 to 3 was measured. The measurement results are shown in Table 1.

[0054] The electrode wires manufactured by the processes of Comparative Examples 1 to 3 were measured using an E350 machine manufactured by Agie Co., Ltd. The material of the measured workpiece was 8407, the dimensions of the measured workpiece were 6 mm (length) x 6 mm (width) x 50 mm (thickness), and the number of measuring cutting edges was selected as "1 cut and 4 trimmings." The measurement results are shown in Table 2.

[0055] Analysis of the measurement results shows that the electrode wire of the present invention has superior cutting speed and cutting accuracy compared to conventional brass wire and plated wire.

[0056] Table 1. Measurement results of the carbon content, conductivity, and adhesion state of the surface layer on the electrode wire surface of the Examples, Control Examples, and Comparative Examples. [Table 1]

[0057] Table 2: Measurement results of cutting speed and cutting accuracy of electrode wires in Examples, Control Examples, and Comparative Examples [Table 2]

[0058] Although the embodiments of the present invention have been shown and described above, the above embodiments are illustrative and should not be understood as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A core material and an intermediate layer positioned outside the core material; a surface layer located outside the intermediate layer, the core material is a metal or an alloy, the intermediate layer is a copper-zinc alloy; The surface layer is an electrode wire for low-speed wire electric discharge machining containing carbon elements, The carbon element content on the surface of the low-speed wire electric discharge machining electrode wire is 0.2 to 60 wt %. Electrode wire for low-speed wire electric discharge machining.

2. The carbon element content on the surface of the low-speed wire electric discharge machining electrode wire is 1 to 20 wt %.

2. The electrode wire for low-speed wire electric discharge machining according to claim 1.

3. The carbon element in the surface layer is at least partially present as elemental carbon.

2. The electrode wire for low-speed wire electric discharge machining according to claim 1.

4. The carbon element includes graphite and / or amorphous carbon.

4. The electrode wire for low-speed wire electric discharge machining according to claim 3.

5. The surface layer discontinuously covers the outside of the intermediate layer, and the intermediate layer and / or the core material are exposed through the cutouts in the surface layer.

5. The electrode wire for low-speed wire electric discharge machining according to claim 1.

6. The copper-zinc alloy of the intermediate layer is at least one of a β-phase copper-zinc alloy, a β'-phase copper-zinc alloy, and a γ-phase copper-zinc alloy.

5. The electrode wire for low-speed wire electric discharge machining according to claim 1.

7. The intermediate layer has cracks.

5. The electrode wire for low-speed wire electric discharge machining according to claim 1.

8. The core material is copper or a copper alloy.

5. The electrode wire for low-speed wire electric discharge machining according to claim 1.

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