An electrode wire for electrical discharge machining and a preparation method thereof

Abstract

The present invention discloses an electrode wire for electric discharge machining and a preparation method thereof, including: 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, and the intermediate layer is a copper-zinc alloy; the surface of the intermediate layer has pits, and the surface of the pits has micro-pits, and the size of the micro-pits is smaller than the size of the pits where they are located, and the surface layer discontinuously covers the outside of the intermediate layer and fills the pits and micro-pits. During the preparation process, a copper-zinc alloy is formed inside the electrode wire through electroplating, heat treatment and stretching processes, and pits and micro-pits are extruded on the surface of the intermediate layer. Applying the present invention can improve the cutting speed during wire electrical discharge machining.

Description

Technical Field

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

[0002] The basic working principle of wire cut electrical discharge machining (WEDM) is to use a continuously moving thin metal wire (referred to as the electrode wire) as an electrode to perform pulsed spark discharge on a workpiece to erode metal and cut it into shape.

[0003] Wire cut electrical discharge machining processes a workpiece through the discharge principle of electric sparks. Before machining, the workpiece is connected to the positive pole of a pulse power supply, and the electrode wire is connected to the negative pole of a high-frequency pulse power supply as a tool electrode, and the workpiece is cut using spark discharge. The pulse power supply provides the machining energy, and a special wire cutting working fluid is used during the machining process to remove the debris generated during machining. Under the action of a strong electric field, the surfaces of the cathode and anode are respectively bombarded by electron flows and ion flows, so that an instantaneous high-temperature heat source is formed in the electrode gap to melt and vaporize local metal, thereby forming corrosion pits on both the electrode wire and the workpiece. 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 channel, thus completing a spark discharge process. When the next pulse arrives, the above spark discharge process is continued to cut the workpiece into shape.

[0004] Cutting speed, cutting accuracy, and the surface finish of the workpiece after machining are evaluation indicators for the quality of wire cut electrical discharge machining technology, and each of the above indicators has a very large relationship with the performance of the electrode wire used.

[0005] To obtain a faster cutting speed, in the related prior art, a high-zinc alloy layer with a high zinc content is plated on the surface of the electrode wire. By using the low sublimation temperature of zinc, a high discharge vaporization pressure is achieved during the machining process, thereby increasing the cutting machining speed.

[0006] To increase the cutting machining speed, there is also related prior art that uses processes such as stretching to form cracks on the surface of the electrode wire. By using the cracks to increase the contact area between the surface of the electrode wire and the working fluid and improve the flushing efficiency of the working fluid on the electrode wire, the cooling effect of the electrode wire can be improved and the time of a single spark discharge can be shortened. In this way, the number of spark discharges per unit time is increased, and the speed of wire cut electrical discharge machining is improved. At the same time, tips can be formed at the edges of the cracks, and the tips are more likely to discharge, which can also increase the speed of wire cut electrical discharge machining.

[0007] However, with the progress of wire electrical discharge machining, the surface of the electrode wire is gradually consumed, and the high-zinc alloy layer on the surface and the crack structure on the surface gradually disappear. The above-mentioned high-zinc surface metal vaporization effect and crack effect are reduced, and the cutting speed will slow down accordingly. SUMMARY OF THE INVENTION

[0008] The present invention provides an electrode wire for electric spark discharge machining and a preparation method thereof, which are used to solve the problem of slow cutting speed caused by the consumption of the electrode wire in the prior art.

[0009] The present invention adopts the following technical scheme: An electrode wire for electric spark 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, and the intermediate layer is a copper-zinc alloy; the surface of the intermediate layer has pits, and the surface of the pits has micro-pits, the size of the micro-pits is smaller than the size of the pits where they are located, and the surface layer discontinuously covers the outside of the intermediate layer and fills the pits and micro-pits.

[0010] The present invention has the following beneficial effects:

[0011] 1. When this electrode wire is used for wire electrical discharge machining, as the machining process progresses, the surface layer of the electrode wire is gradually consumed by discharge corrosion, exposing the intermediate layer of the electrode wire. The surface of the intermediate layer has pits and micro-pits on the surface of the pits. When the surface layer is first consumed by discharge corrosion during the machining process, the exposed surface area of the intermediate layer increases. Thus, when the working fluid flushes and cools the electrode wire, the contact area between the surface of the electrode wire and the working fluid is greatly increased, which can improve the flushing and cooling efficiency of the working fluid for the electrode wire, shorten the time of a single spark discharge, that is, increase the number of spark discharges per unit time, and thus improve the speed of wire electrical discharge machining.

[0012] 2. Tips will be formed at the open edges of the pits and micro-pits. The tips are more prone to discharge. Therefore, when wire electrical discharge machining is carried out, the reaction time for the electrode wire to generate electric sparks can be reduced, thereby accelerating the speed of wire electrical discharge machining;

[0013] 3. Since the surface layer discontinuously covers the outside of the intermediate layer, tips will also be formed at the discontinuous parts of the surface layer. The tips are more prone to discharge. Therefore, when wire electrical discharge machining is carried out, the reaction time for the electrode wire to generate electric sparks can be reduced, thereby accelerating the speed of wire electrical discharge machining.

[0014] Preferably, the thickness of the intermediate layer is 1-50 μm, and the thickness of the surface layer is 0.1-20 μm. During the preparation process, the thicknesses of the finally formed surface layer and intermediate layer are related to the thickness of the galvanized layer. If the galvanized layer is too thin, it cannot function as a functional layer. If the galvanized layer is too thick, the outermost galvanized layer cannot participate in the alloying reaction. The ranges of the thicknesses of the surface layer and intermediate layer obtained through preparation with a suitable galvanized layer thickness are as above.

[0015] Preferably, the thickness of the intermediate layer is 5-40 μm, and the thickness of the surface layer is 0.1-15 μm. Specifically, the thickness of the intermediate layer can be 5-30 μm, 10-40 μm, 10-30 μm, or 20-30 μm; the thickness of the surface layer can be 0.1-10 μm, 1-15 μm, 1-10 μm, 5-15 μm, or 5-10 μm.

[0016] Preferably, along the radial direction of the electrode wire, the depth of the pit is 0.1-20 μm, and the depth of the micro-pit is 0.05-10 μm. The pits and micro-pits with the above dimensions can ensure that when the pit and micro-pit structures are exposed, the electrode wire has a sufficiently large contact area with the working fluid, and at the same time, it can ensure that the tips formed at the edges of the pits and micro-pits have a good tip discharge effect, thereby improving the speed of wire electrical discharge machining.

[0017] Preferably, along the radial direction of the electrode wire, the depth of the pit is 0.1-10 μm, and the depth of the micro-pit is 0.05-5 μm. Specifically, along the radial direction of the electrode wire, the depth of the pit can be 0.5-10 μm, 1-10 μm, 0.5-5 μm, or 1-5 μm, and the depth of the micro-pit can be 0.05-3 μm, 0.05-2 μm, 0.05-1 μm, 0.1-5 μm, 0.1-3 μm, 0.1-2 μm, or 0.1-1 μm.

[0018] Preferably, the surface layer contains carbon element and zinc element. Among them, the zinc element ensures that the surface layer has an excellent gasification and erosion effect, improving the cutting speed; the presence of the carbon element not only increases the conductivity of the electrode wire, improves the cutting speed, but also increases the hardness of the surface layer, which is beneficial to the formation of the pit and micro-pit structures on the surface of the intermediate layer.

[0019] Preferably, by mass percentage, the carbon element content in the surface layer is ≥0.5%, and the zinc element content is ≥60%. The above component contents ensure that there are sufficient zinc element and carbon element in the surface layer, which is conducive to the full play of the relevant components.

[0020] Preferably, the intermediate layer also has cracks. Similarly to the foregoing, tips are formed at the cracks, and the tips are more likely to discharge electricity. Therefore, 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. In addition, the cracks can also play a similar role to the above-mentioned pits to a certain extent, that is, the cutting speed can be increased by increasing the contact area between the electrode wire and the working fluid. Therefore, after the surface layer is consumed, the pit, micro-pit and crack structures of the intermediate layer can further accelerate the cutting speed.

[0021] Preferably, the intermediate layer and / or the core material are exposed at the discontinuity of the surface layer. The exposed intermediate layer or core material can improve the electrical conductivity of the surface layer, which is beneficial to enhancing the transmission of discharge energy, and further enhancing the cutting speed. At the same time, the exposure of the intermediate layer or core material can form a discontinuity on the surface layer. As mentioned above, the discontinuity can increase the cutting speed.

[0022] Preferably, the core material is copper or copper alloy.

[0023] To solve the above technical problems, the present invention also adopts the following technical solution: A preparation method of an electrode wire for electric spark discharge machining, comprising the following steps:

[0024] S100: Provide a pure copper bus bar or a copper alloy bus bar;

[0025] S101: Galvanize the surface of the bus bar. The electroplating solution includes additives, so as to form a galvanized layer on the surface of the bus bar to make a first wire blank. Among them, the additive is a saccharide organic compound, and the current density range of electroplating is 5-150 A / dm 2 ;

[0026] S102: Heat-treat the first wire blank. The copper element in the bus bar and the zinc element in the galvanized layer diffuse into each other during the heat treatment process to form an intermediate layer, and make a second wire blank. The second wire blank has a core material, an intermediate layer and a surface layer in sequence from inside to outside;

[0027] S103: Stretch and stress-relieve anneal the second wire blank to make a finished electrode wire. By applying the above preparation method provided by the present invention, since saccharide organic compounds are added to the electroplating solution, the saccharide organic compounds can adsorb on the surfaces of the bus bar and the galvanized layer crystals, slow down the reduction reaction of zinc ions, make the crystallization speed of the galvanized layer slow down and the grains of the galvanized layer refined, and further make the formed galvanized layer have brittle and hard characteristics. At the same time, in this preparation method, the current density range during electroplating is controlled to be 5-150 A / dm 2, within this current density range, the crystal grains of the zinc-plated layer will be further refined, and more sugar organic compounds will be adsorbed on the surface of the zinc-plated layer crystals, so that the sugar organic compounds can better slow down the reduction reaction of zinc ions, and the zinc-plated layer finally obtained will be denser, brittle and hard. In the subsequent heat treatment process, an alloying reaction occurs between the zinc-plated layer and the busbar. In this process, the sugar organic compounds between the grains form a harder mixture of copper, zinc, carbon and other elements and their oxides with copper and zinc elements. Structurally, the surface layer transformed from the zinc-plated layer has irregular tiny particles distributed on the side facing the middle layer. After being stretched by the die, cracks appear on the surface layer and are distributed outside the middle layer in a block or sheet structure. In this way, the hard and brittle mixture and its oxides are pressed into the middle layer in the form of blocks or sheets to form pits. At the same time, the irregular tiny particles are squeezed on the inner surface of the pits to form micro-pits. In this way, the middle layer inside the finished electrode wire has pits and micro-pits that can increase its surface area, which has a better flushing effect. At the same time, tips are formed at the open edges of the pits and micro-pits, which are easy to discharge and can improve its cutting efficiency during the electric spark wire cutting process.

[0028] Preferably, the heat treatment temperature in step S102 is 300-500° C., the heat treatment time is 1-50 h, and the intermediate layer formed is β-phase copper-zinc alloy and / or β-phase copper-zinc alloy. ’ β-phase copper-zinc alloy. β-phase copper-zinc alloy or β ’ The copper-zinc alloy has a higher conductivity, which can improve the discharge efficiency and thus increase the cutting speed.

[0029] In order to solve the above technical problems, the present invention also adopts the following technical solution: a method for preparing an electrode wire for electric spark discharge machining, comprising the following steps:

[0030] S200: Provide copper busbar or copper alloy busbar;

[0031] S201: zinc is plated on the surface of the busbar, and the electroplating solution includes an additive, so as to form a zinc coating on the surface of the busbar to produce a first wire blank, wherein the additive is a sugar organic compound, and the current density of the electroplating is in the range of 5-150A / dm 2 ;

[0032] S202: heat treating the first wire blank, wherein the copper element in the busbar and the zinc element in the galvanized layer diffuse mutually during the heat treatment process to form a copper-zinc alloy layer, thereby manufacturing a second wire blank, wherein the second wire blank has a core material, a copper-zinc alloy layer and a surface layer in sequence from the inside to the outside;

[0033] S203: stretching the second wire blank to form a third wire blank;

[0034] S204: Heat-treat the third wire blank to produce a fourth wire blank, which sequentially has a core material, an intermediate layer, and a surface layer from the inside out;

[0035] S205: Stretch and stress-relieve anneal the fourth wire blank to produce a finished electrode wire.

[0036] Similarly to the foregoing, through a unique electroplating process, the intermediate layer in the finally formed finished electrode wire has pits and micro-pits, improving the cutting speed.

[0037] Preferably, the heat treatment temperature in step S202 is 100 - 250 °C, the heat treatment time is 3 - 20 h, and the formed copper-zinc alloy layer includes a γ-phase copper-zinc alloy. After plating, alloying is first carried out at a lower heat treatment temperature to produce a γ-phase copper-zinc alloy. Since the γ-phase copper-zinc alloy is harder, it will break and generate cracks during the subsequent stretching process. The electric field formed between the electrode wire and the workpiece will also have differences in strength locally. The electric field will be further enhanced at the locations where cracks are formed. Therefore, the discharge will preferentially occur at the edges of the cracks. Compared with the situation where there are no cracks in the intermediate layer, using the electrode wire with cracks in the intermediate layer can improve the reaction time for the electrode wire to generate electric sparks, thereby accelerating the speed of wire electrical discharge machining. At the same time, the cracks can also, to a certain extent, have an effect similar to the above-mentioned pits and micro-pits in increasing the contact area between the intermediate layer and the working fluid.

[0038] Preferably, the heat treatment temperature in step S204 is 300 - 550 °C, the heat treatment time is 1 - 50 h, and the formed intermediate layer is a β-phase copper-zinc alloy and / or a β ’ phase copper-zinc alloy. Through heat treatment, the γ-phase copper-zinc alloy is transformed into a β-phase copper-zinc alloy and / or a β ’ phase copper-zinc alloy. In this way, the finally formed β-phase copper-zinc alloy or β ’ phase copper-zinc alloy as the intermediate layer has not only pits but also cracks. At the same time, the β-phase copper-zinc alloy and the β ’ phase copper-zinc alloy have better electrical conductivity than the γ-phase copper-zinc alloy, and can further improve the cutting speed.

[0039] To solve the above technical problems, the present invention also adopts the following technical solution: A preparation method of an electrode wire for electric spark discharge machining, comprising the following steps:

[0040] S300: Provide a pure copper bus bar or a copper alloy bus bar;

[0041] S301: Galvanize the surface of the bus bar. The electroplating solution includes an additive, so as to form a galvanized layer on the surface of the bus bar and produce a first wire blank. Among them, the additive is a saccharide organic compound, and the current density range of electroplating is 5 - 150 A / dm 2 ;

[0042] S302: Stretch the first wire blank to produce a second wire blank;

[0043] S303: Heat-treat the second wire blank, causing the copper element in the bus bar and the zinc element in the galvanized layer to diffuse into each other during the heat treatment to form an intermediate layer, and produce a third wire blank. The third wire blank has a core material, an intermediate layer, and a surface layer in sequence from the inside out;

[0044] S304: Stretch and stress-relieve anneal the third wire blank to produce a finished electrode wire.

[0045] Similarly to the above, through a unique electroplating process, the intermediate layer in the finally formed finished electrode wire has pits and micropits, improving the cutting speed. In addition, since stretching is carried out immediately after electroplating, the dense and brittle galvanized layer is easily broken, making it easy for the internal bus bar to extrude out of the galvanized layer. In this way, the core material and the intermediate layer inside the finally produced electrode wire are easy to extrude out of the surface layer. The core material and the intermediate layer have better conductivity, can improve the discharge efficiency, and thus enhance the cutting speed.

[0046] The heat treatment temperature in step S303 is 200 - 500 °C, the heat treatment time is 1 - 50 h, and the formed intermediate layer is β-phase copper-zinc alloy and / or β ’ phase copper-zinc alloy and / or γ-phase copper-zinc alloy. By using different process parameters for the heat treatment in step S303, the intermediate layer in the finally prepared electrode wire shows different phases. The β-phase copper-zinc alloy and the β ’ phase copper-zinc alloy are softer on the one hand and are more easily extruded to form pits and micropits during the subsequent stretching process, so the effect of improving the flushing effect is more obvious; on the other hand, the β-phase copper-zinc alloy and the β ’ phase copper-zinc alloy have better conductivity, can improve the discharge efficiency, and thus enhance the cutting speed. Although the γ-phase copper-zinc alloy is harder and the pits and micropits extruded are shallower compared to the β-phase copper-zinc alloy and the β ’ phase copper-zinc alloy, and the effect on improving the flushing effect is a little smaller, but the γ-phase copper-zinc alloy has a high zinc content and obvious gasification effect during wire electrical discharge machining, and can also enhance the wire cutting speed.

[0047] Preferably, the concentration of the additive in the electroplating solution is 8 - 25 g / L.

[0048] Preferably, the saccharide organic compound is one or a mixture of maltose, lactose, dextrin, and sucrose.

[0049] 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

[0050] Figure 1 It is a schematic diagram of a partial cross-section of an electrode wire produced by using the preparation method provided by the present invention;

[0051] Figure 2 It is a surface electron microscope image of the electrode wire in Example 1 before corrosion;

[0052] Figure 3 It is a surface electron microscope image of the electrode wire in Example 1 after corrosion;

[0053] Figure 4 It is a schematic diagram of a partial cross-section of another electrode wire produced by using the preparation method provided by the present invention;

[0054] Figure 5 It is a surface electron microscope image of the electrode wire in Example 4 before corrosion;

[0055] Figure 6 It is a surface electron microscope image of the electrode wire in Example 4 after corrosion;

[0056] Figure 7 It is a schematic diagram of a partial cross-section of another electrode wire produced by using the preparation method provided by the present invention;

[0057] Figure 8 It is a surface electron microscope image of the electrode wire in Example 7 before corrosion;

[0058] Figure 9 It is a surface electron microscope image of the electrode wire in Example 7 after corrosion;

[0059] Figure 10 It is a schematic diagram of a partial cross-section of another electrode wire produced by using the preparation method provided by the present invention;

[0060] Figure 11 It is a surface electron microscope image of the electrode wire in Example 10 before corrosion;

[0061] Figure 12 It is a surface electron microscope image of the electrode wire in Example 10 after corrosion.

[0062] Among them, 1. core material, 2. intermediate layer, 20. pit, 200. micro-pit, 21. crack, 22. β-phase copper-zinc alloy, 23. γ-phase copper-zinc alloy, 3. surface layer. Detailed Description of the Invention

[0063] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0064] Before illustrating a specific embodiment, the structural features of the electrode wire for electric spark discharge machining provided by the present invention and the principle of its preparation method are described:

[0065] When preparing the busbar, a brass busbar is generally used, specifically, it is generally made of CuZn37 brass or CuZn40 brass. The busbar can also be prepared using red copper (i.e. pure copper), or a copper alloy other than brass.

[0066] Sugar organic compounds are added to the electroplating solution. Sugar organic compounds can be adsorbed on the surface of the busbar and the zinc-plated layer crystals, thereby slowing down the reduction reaction of zinc ions, which will slow down the crystallization speed of the zinc-plated layer and refine the grains of the zinc-plated layer, thereby making the zinc-plated layer formed by plating have the characteristics of brittleness and hardness. At the same time, the current density range during electroplating is controlled to 5-150A / dm 2 , within this current density range, the crystal grains of the zinc-plated layer will be further refined, and more sugar organic compounds will be adsorbed on the surface of the zinc-plated layer crystals, so that the sugar organic compounds can better slow down the reduction reaction of zinc ions, and the zinc-plated layer finally obtained will be denser, brittle and hard. Then, in the subsequent heat treatment process, an alloying reaction occurs between the zinc-plated layer and the busbar, in which the sugar organic compounds between the grains form a harder mixture of copper, zinc, carbon and other elements and their oxides with copper and zinc elements. Structurally, the surface layer transformed from the zinc-plated layer has irregular tiny particles distributed on the side facing the middle layer. After being stretched by the die, cracks appear on the surface layer and are distributed outside the middle layer in block or sheet structures, so that the hard and brittle mixture and its oxides are pressed into the middle layer in the form of blocks or sheets to form pits, and at the same time, the irregular tiny particles are squeezed on the inner surface of the pits to form micro-pits. The size of the current density range plays an important role in the preparation process. If the current density is too small, it will not play the role of promoting the grain refinement of the galvanized layer. If the current density is too large, it will affect the galvanizing effect and make the galvanized layer black and burnt. It should also be noted that because the micro-pits are formed by the irregular tiny particles on the surface layer facing the middle layer on the inner surface of the pits, and the irregular tiny particles on the surface are not regular and smooth, there may be certain concave structures. After the mold is stretched, when the pits and micro-pits are formed, the adjacent micro-pits may be relatively flat structures, or there may be certain protrusions.

[0067] In addition, during the actual production and processing, due to the volatilization of some components, wear and tear, etc., there may be certain gaps between the surface layer and the pits and micro-pits. In this embodiment, the above-mentioned filling includes both the situation where the pits and micro-pits are completely filled, and the situation where the pits and micro-pits are not completely filled with the surface layer and there are gaps. On the same electrode wire, the above-mentioned two situations of complete filling and incomplete filling may exist at the same time.

[0068] During the heat treatment stage in the preparation process, zinc elements in the galvanized layer and copper elements in the core material diffuse into each other to form a copper-zinc alloy (i.e., the alloying process). Under different heat treatment process parameters, the copper-zinc alloy can be in the β phase or γ phase or β phase + γ phase. Among them, the β phase can also be the β ’ phase. For the convenience of description, the β phase is used to represent in the following embodiments, that is, the β phase in the following text means one or both of the β phase and the β ’ phase have.

[0069] Viewed from the position, the pits are formed at the interface between the intermediate layer and the surface layer, and the micropits are formed on the surface of the pits; in terms of size comparison, the depth of the pits is 0.1 - 20 μm, and the depth of the micropits is 0.05 - 10 μm. The depths of the above pits and micropits refer to the data obtained by cutting the electrode wire transversely and measuring the radial dimensions of the pits and micropits at different positions on its cross-section. The sizes of the pits and micropits at different positions are within the above range. The pits and micropits both show an irregular distribution. In addition, it should be noted that under certain process conditions, there are cracks in the intermediate layer inside the electrode wire, and there are significant differences in the morphology between the cracks and the pits and micropits. The cracks are in the shape of long and narrow slits, while the pits and micropits are in the shape of open pits. Based on the above differences in the structural morphology, the pits and micropits play a greater role in increasing the contact area between the intermediate layer and the working fluid. In addition, the cracks are formed by the fracture of the copper-zinc alloy layer during the stretching process, while the pits and micropits are formed by the extrusion of the intermediate layer by the surface layer during the stretching process.

[0070] In actual manufacturing, the wire diameter specification of the selected bus bar is generally between 0.5 - 1.2 mm. The thickness of the intermediate layer of the prepared electrode wire finished product is 1 - 50 μm, and the thickness of the surface layer is 0.1 - 20 μm. It should be noted that the thicknesses of the above intermediate layer and surface layer refer to the data obtained by cutting the electrode wire transversely and measuring the radial dimensions of the intermediate layer and surface layer at different positions on its cross-section. The sizes of the intermediate layer and surface layer at different positions are within the above range.

[0071] In terms of mass percentage, the carbon element content in the surface layer of the electrode wire prepared in this embodiment is ≥0.5%, and the zinc element content is ≥60%.

[0072] The present invention provides three preparation methods. The following Examples 1 - 3 adopt the first preparation method, and the cross-section of the prepared electrode wire finished product refers to Figure 1 as shown, and the surface SEM images of the electrode wire before and after corrosion refer to Figure 2 and Figure 3 as shown; the following Examples 4 - 6 adopt the second preparation method, and the cross-section of the prepared electrode wire finished product refers to Figure 4 as shown, and the surface SEM images of the electrode wire before and after corrosion refer to Figure 5 andFigure 6 as shown; Examples 7-12 below adopted the third preparation method. Among them, the cross-section of the finished electrode wire made in Examples 7-9 refers to Figure 7 as shown in, and the surface SEM images of the electrode wire before and after corrosion refer to Figure 8 and Figure 9 as shown; the cross-section of the finished electrode wire made in Examples 10-12 refers to Figure 10 as shown in, and the surface SEM images of the electrode wire before and after corrosion refer to Figure 11 and Figure 12 as shown. In the present invention, the SEM image of the electrode wire after corrosion is obtained by observing with an electron microscope after chemically corroding the surface layer of the electrode wire. Specifically, a section of the electrode wire product is cut off and placed in dilute hydrochloric acid (mass fraction 10%-20%) for 30-120 s to corrode the surface layer, and the intermediate layer can be exposed.

[0073] Example 1: This example provides a preparation method for an electrode wire for electric discharge machining, and the preparation method includes the following steps:

[0074] S100: Provide a CuZn37 brass bus bar with a wire diameter specification of 1.2 mm;

[0075] S101: Electroplate zinc on the outer surface of the above-mentioned brass bus bar. The electroplating solution includes additives, so as to form a zinc coating with a thickness of 20 μm on the surface of the bus bar to make the first wire blank. Among them, the electroplating current density range is 150 A / dm 2 , and the additive is one or a mixture of maltose, lactose, dextrin and sucrose, and the concentration of the additive in the electroplating solution is 12 g / L;

[0076] S102: Perform heat treatment on the first wire blank. The heat treatment temperature is 420 °C and the heat treatment time is 10 h. The copper element in the bus bar and the zinc element in the zinc coating diffuse with each other during the heat treatment process to form a β-phase copper-zinc alloy, and the second wire blank is made. The second wire blank has a core material, a β-phase copper-zinc alloy as the intermediate layer and a surface layer from the inside to the outside in sequence;

[0077] S103: Stretch and stress relieve the second wire blank to make a finished electrode wire with a wire diameter specification of 0.25 mm. The cross-section of the finished electrode wire is as Figure 1 shown in. In this step, the surface layer 3 breaks and forms cracks during the stretching process, and the intermediate layer 2 extrudes the cracks during the stretching process, that is, the final electrode wire shows that the surface layer 3 intermittently covers the intermediate layer 2. In addition, the surface layer 3 is extruded and embedded into the intermediate layer 2 during the stretching process, forming pits 20 on the intermediate layer 2 and micro-pits 200 in the pits 20.

[0078] Example 2: This example provides a method for preparing an electrode wire for electric discharge machining, and the preparation method includes the following steps:

[0079] S100: Provide a CuZn40 brass bus bar with a wire diameter specification of 1 mm;

[0080] S101: Electroplate zinc on the outer surface of the above-mentioned brass bus bar. The electroplating solution includes additives, so as to form a zinc plating layer with a thickness of 12 μm on the surface of the bus bar, and make the first wire blank. Among them, the electroplating current density range is 100 A / dm 2 , the additive is one or a mixture of maltose, lactose, dextrin and sucrose, and the concentration of the additive in the electroplating solution is 8 g / L;

[0081] S102: Perform heat treatment on the first wire blank. The heat treatment temperature is 500 °C and the heat treatment time is 1 h. The copper element in the bus bar and the zinc element in the zinc plating layer diffuse with each other during the heat treatment process to form a β-phase copper-zinc alloy, and make the second wire blank. The second wire blank has a core material, a β-phase copper-zinc alloy as an intermediate layer and a surface layer from the inside to the outside in sequence;

[0082] S103: Stretch and stress relieve the second wire blank to make an electrode wire finished product with a wire diameter specification of 0.25 mm. The cross-section of the electrode wire finished product is referenced Figure 1 as shown in. In this step, the surface layer 3 breaks and forms cracks during the stretching process, and the intermediate layer 2 extrudes the cracks during the stretching process, that is, the final electrode wire shows that the surface layer 3 intermittently covers the outside of the intermediate layer 2. In addition, the surface layer 3 is extruded and embedded into the intermediate layer 2 during the stretching process, forming pits 20 on the intermediate layer 2 and micro-pits 200 in the pits 20.

[0083] Example 3: This example provides a method for preparing an electrode wire for electric discharge machining, and the preparation method includes the following steps:

[0084] S100: Provide a CuZn37 brass bus bar with a wire diameter specification of 0.5 mm;

[0085] S101: Electroplate zinc on the outer surface of the above-mentioned brass bus bar. The electroplating solution includes additives, so as to form a zinc plating layer with a thickness of 3 μm on the surface of the bus bar, and make the first wire blank. Among them, the electroplating current density range is 5 A / dm 2 , the additive is one or a mixture of maltose, lactose, dextrin and sucrose, and the concentration of the additive in the electroplating solution is 25 g / L;

[0086] S102: Heat-treat the first wire blank at a heat-treatment temperature of 300 °C for 50 h. During the heat treatment, copper elements in the bus bar and zinc elements in the galvanized layer diffuse into each other to form a β-phase copper-zinc alloy, producing a second wire blank. The second wire blank has, from the inside out, a core material, a β-phase copper-zinc alloy as the intermediate layer, and a surface layer.

[0087] S103: Stretch and stress-relieve anneal the second wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm. The cross-section of the finished electrode wire is shown in Figure 1 . In this step, the surface layer 3 breaks and forms cracks during the stretching process, and the intermediate layer 2 extrudes into these cracks during the stretching process, such that the final electrode wire appears as the surface layer 3 intermittently covering the outside of the intermediate layer 2. Additionally, the surface layer 3 squeezes and embeds into the intermediate layer 2 during the stretching process, forming pits 20 on the intermediate layer 2 and micro-pits 200 within the pits 20.

[0088] Applying the preparation methods provided in the above Examples 1 to 3, within the finished electrode wire produced, the intermediate layer 2 has pits 20 and micro-pits 200 that can increase its surface area, which can improve the cutting efficiency during wire electrical discharge machining. As shown in Figure 2 and Figure 3 , initially, the surface layer 3 of the electrode wire has cracks, exposing the internal intermediate layer 2 (for this electrode wire, that is, the β-phase copper-zinc alloy 22). As the wire electrical discharge machining progresses, the surface layer 3 is consumed by discharge corrosion, and the intermediate layer 2 below the surface layer 3 is exposed, and the pits 20 and micro-pits 200 on the surface of the intermediate layer 2 can be seen. Additionally, since the surface layer intermittently covers the outside of the intermediate layer, tips are formed at the intermittent locations of the surface layer. The tips are more prone to discharging, so during wire electrical discharge machining, the reaction time for the electrode wire to generate electrical discharges can be reduced, thereby accelerating the speed of wire electrical discharge machining.

[0089] Example 4: This example provides a method for preparing an electrode wire for electrical discharge machining, including the following steps:

[0090] S200: Provide a CuZn40 brass bus bar with a wire diameter specification of 0.8 mm.

[0091] S201: Electroplate zinc on the outer surface of the above brass bus bar. The electroplating solution includes additives, thereby plating a galvanized layer with a thickness of 8 μm on the surface of the bus bar to produce a first wire blank. Among them, the electroplating current density range is 70 A / dm 2 , and the additives are one or a mixture of maltose, lactose, dextrin, and sucrose, and the concentration of the additives in the electroplating solution is 25 g / L.

[0092] S202: Heat-treat the first wire blank at a heat-treatment temperature of 130°C for 20 h. During the heat treatment, the copper element in the bus bar and the zinc element in the galvanized layer diffuse into each other to form a γ-phase copper-zinc alloy, thereby producing a second wire blank. The second wire blank sequentially has a core material, a γ-phase copper-zinc alloy, and a surface layer from the inside out;

[0093] S203: Stretch the second wire blank to produce a third wire blank with a wire diameter specification of 0.3 mm. Both the surface layer and the γ-phase copper-zinc alloy break during the stretching process, cracks are generated in the surface layer, and cracks are generated in the γ-phase copper-zinc alloy;

[0094] S204: Heat-treat the third wire blank at a heat-treatment temperature of 300°C for 50 h to produce a fourth wire blank. The γ-phase copper-zinc alloy is transformed into a β-phase copper-zinc alloy serving as an intermediate layer;

[0095] S205: Stretch and stress-relief anneal the fourth wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm. The cross-section of the finished electrode wire is as Figure 4 shown in. The surface layer 3 is extruded and embedded into the intermediate layer 2 during the stretching process, pits 20 are formed on the intermediate layer 2, and micro-pits 200 are formed in the pits 20. The intermediate layer 2 extrudes the cracks during the stretching process and enables the surface layer 3 to intermittently cover the outside of the intermediate layer 2, and part of the core material 1 can also be extruded from the broken intermediate layer 2.

[0096] Example 5: This example provides a method for preparing an electrode wire for electric discharge machining, including the following steps:

[0097] S200: Provide a CuZn40 brass bus bar with a wire diameter specification of 1.2 mm;

[0098] S201: Electroplate zinc on the outer surface of the above-mentioned brass bus bar. The electroplating solution includes additives, so as to form a galvanized layer with a thickness of 15 μm on the surface of the bus bar to produce a first wire blank. Among them, the electroplating current density range is 120 A / dm 2 , the additive is one or a mixture of maltose, lactose, dextrin, and sucrose, and the concentration of the additive in the electroplating solution is 8 g / L;

[0099] S202: Heat-treat the first wire blank at a heat-treatment temperature of 250°C for 3 h. During the heat treatment, the copper element in the bus bar and the zinc element in the galvanized layer diffuse into each other to form a γ-phase copper-zinc alloy, thereby producing a second wire blank. The second wire blank sequentially has a core material, a γ-phase copper-zinc alloy, and a surface layer from the inside out;

[0100] S203: Stretch the second wire blank to produce a third wire blank with a wire diameter specification of 0.5 mm. Both the surface layer and the γ-phase copper-zinc alloy break during the stretching process, cracks are generated in the surface layer, and cracks are generated in the γ-phase copper-zinc alloy;

[0101] S204: Heat-treat the third wire blank at a heat-treatment temperature of 550 °C for 1 h to produce a fourth wire blank, and transform the γ-phase copper-zinc alloy into a β-phase copper-zinc alloy;

[0102] S205: Stretch and stress-relieve anneal the fourth wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm. The cross-section of the finished electrode wire is shown in the reference Figure 4 as shown. The surface layer 3 is extruded and embedded into the intermediate layer 2 during the stretching process, forming a pit 20 in the intermediate layer 2 and micro-pits 200 in the pit 20. The intermediate layer 2 extrudes the crack during the stretching process and makes the surface layer 3 discontinuously cover the outside of the intermediate layer 2, and part of the core material 1 can also be extruded from the broken intermediate layer 2.

[0103] Example 6: This example provides a method for preparing an electrode wire for electric discharge machining, including the following steps:

[0104] S200: Provide a CuZn37 brass bus bar with a wire diameter specification of 0.95 mm;

[0105] S201: Electroplate zinc on the outer surface of the above-mentioned brass bus bar. The electroplating solution includes additives, so as to deposit a zinc plating layer with a thickness of 11 μm on the surface of the bus bar to produce a first wire blank; wherein, the electroplating current density range is 90 A / dm 2 , and the additive is one or a mixture of maltose, lactose, dextrin and sucrose, and the concentration of the additive in the electroplating solution is 16 g / L;

[0106] S202: Heat-treat the first wire blank at a heat-treatment temperature of 180 °C for 20 h. The copper element in the bus bar and the zinc element in the zinc plating layer diffuse into each other during the heat-treatment process to form a γ-phase copper-zinc alloy, and a second wire blank is produced. The second wire blank has a core material, a γ-phase copper-zinc alloy and a surface layer from the inside out;

[0107] S203: Stretch the second wire blank to produce a third wire blank with a wire diameter specification of 0.55 mm. Both the surface layer and the γ-phase copper-zinc alloy break during the stretching process, cracks are generated in the surface layer, and cracks are generated in the γ-phase copper-zinc alloy;

[0108] S204: Heat-treat the third wire blank at a heat-treatment temperature of 440 °C for 28 h to produce a fourth wire blank, and transform the γ-phase copper-zinc alloy into a β-phase copper-zinc alloy;

[0109] S205: Stretch and stress-relieve anneal the fourth wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm. The cross-section of the finished electrode wire is shown in the reference Figure 4As shown in the figure. The surface layer 3 is extruded and embedded into the intermediate layer 2 during the stretching process, forming a pit 20 on the intermediate layer 2 and micro-pits 200 in the pit 20. The intermediate layer 2 extrudes the crack during the stretching process and enables the surface layer 3 to intermittently cover the outside of the intermediate layer 2, and part of the core material 1 can also be extruded from the fractured intermediate layer 2.

[0110] It should be noted that in the above Examples 4 to 6, during the heat treatment process in step S202, the copper element in the bus bar and the zinc element in the galvanized layer diffuse into each other during the heat treatment process to form a γ-phase copper-zinc alloy, which means that the composition of the copper-zinc alloy layer formed during this process is mainly γ-phase copper-zinc alloy, but a small part of β-phase copper-zinc alloy may also be generated. It can be understood that the main purpose of this step is to obtain a γ-phase copper-zinc alloy so that during the subsequent step S203 of stretching, cracks are likely to be generated in the copper-zinc alloy layer (the γ-phase copper-zinc alloy is harder and is likely to generate cracks during stretching).

[0111] Applying the preparation method provided in the above Examples 4 to 6, on the outer surface of the intermediate layer 2 inside the finished electrode wire product, there are pits 20 and micro-pits 200 that can increase its surface area, which can improve the cutting efficiency during the wire electrical discharge machining process. As Figure 5 and Figure 6 As shown in the figure, initially, there are cracks on the surface layer 3 of the electrode wire, which can expose the internal core material 1 and intermediate layer 2 (for this electrode wire, that is, the β-phase copper-zinc alloy 22). As the wire electrical discharge machining progresses, the surface layer participates in the discharge corrosion and is consumed, and the intermediate layer located below the surface layer is exposed, and the pits and micro-pits on the surface of the intermediate layer can be seen. In addition, the final β-phase copper-zinc alloy as the intermediate layer has not only pits and micro-pits but also cracks. The strong electric field formed between the electrode wire and the workpiece will also have differences locally. The electric field will be further enhanced at the location where the crack 21 is formed. Therefore, the discharge will preferentially occur at the edge of the crack 21. Therefore, compared with the situation where no crack 21 is generated, applying this electrode wire with the crack 21 can improve the reaction time for the electrode wire to generate electric sparks, thereby accelerating the wire electrical discharge machining speed. At the same time, since part of the core material 1 and part of the intermediate layer 2 are exposed, the core material and the β-phase copper-zinc alloy can improve the discharge efficiency and can further improve the wire cutting speed.

[0112] Example 7: This example provides a preparation method for an electrode wire used in electric spark discharge machining, including the following steps:

[0113] S300: Provide a CuZn37 brass bus bar with a wire diameter specification of 0.88 mm;

[0114] S301: Electroplate zinc on the outer surface of the above brass bus bar. The electroplating solution includes additives, thereby plating a galvanized layer with a thickness of 11 μm on the surface of the bus bar to make the first wire blank; among them, the electroplating current density range is 80 A / dm2 , the additive is one or a mixture of maltose, lactose, dextrin and sucrose, and the concentration of the additive in the electroplating solution is 16 g / L;

[0115] S302: Stretch the first wire blank to make a second wire blank with a wire diameter specification of 0.45 mm. During this process, the dense and brittle galvanized layer breaks, and the internal bus bar extrudes from the break point out of the galvanized layer;

[0116] S303: Heat-treat the second wire blank. The heat-treatment temperature is 350 °C and the heat-treatment time is 50 h. The copper element in the bus bar and the zinc element in the galvanized layer diffuse into each other during the heat-treatment process to form a β-phase copper-zinc alloy, and a third wire blank is made. The third wire blank has a core material, a β-phase copper-zinc alloy and a surface layer from the inside out in sequence;

[0117] S304: Stretch and stress-relieve anneal the third wire blank to make a finished electrode wire with a wire diameter specification of 0.25 mm. The cross-section of the finished electrode wire is as Figure 7 shown in. The surface layer 3 is extruded and embedded into the intermediate layer 2 during the stretching process, forming a pit 20 on the intermediate layer 2 and forming a micropit 200 in the pit 20. The intermediate layer 2 extrudes the crack during the stretching process and makes the surface layer 3 discontinuously cover the outside of the intermediate layer 2, and part of the core material 1 can also be extruded from the broken intermediate layer 2.

[0118] Example 8: This example provides a method for preparing an electrode wire for electric discharge machining, including the following steps:

[0119] S300: Provide a CuZn37 brass bus bar with a wire diameter specification of 1.2 mm;

[0120] S301: Electroplate zinc on the outer surface of the above-mentioned brass bus bar. The electroplating solution includes an additive, so as to form a galvanized layer with a thickness of 6 μm on the surface of the bus bar and make a first wire blank; among them, the electroplating current density range is 40 A / dm 2 , the additive is one or a mixture of maltose, lactose, dextrin and sucrose, and the concentration of the additive in the electroplating solution is 8 g / L;

[0121] S302: Stretch the first wire blank to make a second wire blank with a wire diameter specification of 0.6 mm. During this process, the dense and brittle galvanized layer breaks, and the internal bus bar extrudes from the break point out of the galvanized layer;

[0122] S303: Heat-treat the second wire blank. The heat-treatment temperature is 500 °C and the heat-treatment time is 3 h. The copper element in the bus bar and the zinc element in the galvanized layer diffuse into each other during the heat-treatment process to form a β-phase copper-zinc alloy, and a third wire blank is made. The third wire blank has a core material, a β-phase copper-zinc alloy and a surface layer from the inside out in sequence;

[0123] S304: Stretch and stress-relieving anneal the third wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm. The cross-section of the finished electrode wire is referenced Figure 7 as shown in. During the stretching process, the surface layer 3 is extruded and embedded into the intermediate layer 2, forming a pit 20 on the intermediate layer 2 and forming micro-pits 200 in the pit 20. During the stretching process, the intermediate layer 2 extrudes the crack and causes the surface layer 3 to intermittently cover the outside of the intermediate layer 2, and part of the core material 1 can also be extruded from the fractured intermediate layer 2.

[0124] Example 9: This example provides a method for preparing an electrode wire for electric discharge machining, including the following steps:

[0125] S300: Provide a CuZn37 brass bus bar with a wire diameter specification of 0.8 mm;

[0126] S301: Electroplate zinc on the outer surface of the above brass bus bar. The electroplating solution includes additives, so as to form a zinc plating layer with a thickness of 12 μm on the surface of the bus bar to produce a first wire blank; wherein, the current density range of electroplating is 120 A / dm 2 , the additive is one or a mixture of maltose, lactose, dextrin and sucrose, and the concentration of the additive in the electroplating solution is 25 g / L;

[0127] S302: Stretch the first wire blank to produce a second wire blank with a wire diameter specification of 0.55 mm. During this process, the dense and brittle zinc plating layer fractures, and the internal bus bar is extruded from the fracture point out of the zinc plating layer;

[0128] S303: Heat-treat the second wire blank. The heat treatment temperature is 440 °C and the heat treatment time is 20 h. The copper element in the bus bar and the zinc element in the zinc plating layer diffuse into each other during the heat treatment process to form a β-phase copper-zinc alloy, producing a third wire blank. The third wire blank has a core material, a β-phase copper-zinc alloy and a surface layer from the inside out;

[0129] S304: Stretch and stress-relieving anneal the third wire blank to produce a finished electrode wire with a wire diameter specification of 0.25 mm. The cross-section of the finished electrode wire is referenced Figure 7 as shown in. During the stretching process, the surface layer 3 is extruded and embedded into the intermediate layer 2, forming a pit 20 on the intermediate layer 2 and forming micro-pits 200 in the pit 20. During the stretching process, the intermediate layer 2 extrudes the crack and causes the surface layer 3 to intermittently cover the outside of the intermediate layer 2, and part of the core material 1 can also be extruded from the fractured intermediate layer 2.

[0130] Applying the preparation methods provided in Examples 7 to 9 above, on the outer surface of the intermediate layer 2 inside the produced finished electrode wire, there are pits 20 and micro-pits 200 that can increase its surface area, which can improve its cutting efficiency during the wire electrical discharge machining process. As Figure 8 andFigure 9 As shown, there are cracks on the surface layer 3 of the original electrode wire, which can expose the internal intermediate layer 2 (for this electrode wire, that is, the β-phase copper-zinc alloy 22). As the wire electrical discharge machining progresses, the surface layer participates in the discharge corrosion and is consumed, and the intermediate layer located below the surface layer is exposed, and pits and micropits on the surface of the intermediate layer can be seen. In addition, the β-phase copper-zinc alloy that finally serves as the intermediate layer has cracks 21 in addition to pits and micropits. The strong electric field formed between the electrode wire and the workpiece will also have differences locally. The electric field will be further enhanced at the location where the cracks 21 are formed. Therefore, the discharge will preferentially occur at the edge of the cracks 21. Therefore, compared with the case where no cracks 21 are generated, applying the electrode wire with cracks 21 can improve the reaction time for the electrode wire to generate electric sparks, thereby accelerating the speed of wire electrical discharge machining. It should be noted that cracks can be generated on both the surface layer 3 and the intermediate layer 2 of the electrode wire. At the same time, since part of the core material and the β-phase copper-zinc alloy are exposed on the surface layer, the core material and the β-phase copper-zinc alloy can improve the discharge efficiency and can further improve the wire cutting speed.

[0131] Example 10: This example provides a method for preparing an electrode wire for electric spark discharge machining, including the following steps:

[0132] S300: Provide a CuZn37 brass bus bar with a wire diameter specification of 0.95 mm;

[0133] S301: Electroplate zinc on the outer surface of the above-mentioned brass bus bar. The electroplating solution includes additives, so as to form a zinc plating layer with a thickness of 11 μm on the surface of the bus bar to make the first wire blank; among them, the current density range of electroplating is 100 A / dm 2 , and the additive is one or a mixture of maltose, lactose, dextrin and sucrose, and the concentration of the additive in the electroplating solution is 16 g / L;

[0134] S302: Stretch the first wire blank to make a second wire blank with a wire diameter specification of 0.5 mm. In this process, the dense and brittle zinc plating layer breaks, and the internal bus bar extrudes from the fracture point to the zinc plating layer;

[0135] S303: Perform heat treatment on the second wire blank. The heat treatment temperature is 200 °C and the heat treatment time is 50 h. The copper element in the bus bar and the zinc element in the zinc plating layer diffuse into each other during the heat treatment process to form a β-phase copper-zinc alloy and a γ-phase copper-zinc alloy, and make the third wire blank. The third wire blank has a core material, a β-phase copper-zinc alloy, a γ-phase copper-zinc alloy and a surface layer from the inside to the outside in sequence;

[0136] S304: Stretch and stress relieve the third wire blank to make an electrode wire finished product. The cross-section of the electrode wire finished product is as Figure 10As shown in [the figure]. During the stretching process, the surface layer 3 is extruded and embedded into the intermediate layer 2, forming a pit 20 on the intermediate layer 2 and forming micro-pits 200 within the pit 20. During the stretching process, the intermediate layer 2 extrudes the crack and causes the surface layer 3 to intermittently cover the outside of the intermediate layer 2, and part of the core material 1 can also be extruded from the fractured intermediate layer 2.

[0137] Example 11: This example provides a method for preparing an electrode wire for electrical discharge machining, including the following steps:

[0138] S300: Provide a CuZn37 brass bus bar with a wire diameter specification of 1.2 mm;

[0139] S301: Electroplate zinc on the outer surface of the above-mentioned brass bus bar. The electroplating solution includes additives, thereby plating a zinc coating with a thickness of 4.5 μm on the surface of the bus bar to make the first wire blank; among them, the electroplating current density range is 30 A / dm 2 , and the additive is one or a mixture of maltose, lactose, dextrin, and sucrose, and the concentration of the additive in the electroplating solution is 8 g / L;

[0140] S302: Stretch the first wire blank to make a second wire blank with a wire diameter specification of 0.7 mm. During this process, the dense and brittle zinc coating fractures, and the internal bus bar is extruded from the fracture point out of the zinc coating;

[0141] S303: Heat-treat the second wire blank. The heat treatment temperature is 300 °C, and the heat treatment time is 22 h. The copper element in the bus bar and the zinc element in the zinc coating diffuse with each other during the heat treatment process to form β-phase copper-zinc alloy and γ-phase copper-zinc alloy, making the third wire blank. The third wire blank has a core material, β-phase copper-zinc alloy, γ-phase copper-zinc alloy, and a surface layer from the inside out in sequence;

[0142] S304: Stretch and stress-relieve anneal the third wire blank to make a finished electrode wire with a wire diameter specification of 0.25 mm. The cross-section of the finished electrode wire refers to Figure 10 As shown in [the figure]. During the stretching process, the surface layer 3 is extruded and embedded into the intermediate layer 2, forming a pit 20 on the intermediate layer 2 and forming micro-pits 200 within the pit 20. During the stretching process, the intermediate layer 2 extrudes the crack and causes the surface layer 3 to intermittently cover the outside of the intermediate layer 2, and part of the core material 1 can also be extruded from the fractured intermediate layer 2.

[0143] Example 12: This example provides a method for preparing an electrode wire for electrical discharge machining, including the following steps:

[0144] S300: Provide a pure copper bus bar with a wire diameter specification of 0.8 mm;

[0145] S301: Electroplate the outer surface of the above-mentioned brass busbar with zinc. The electroplating solution includes additives, so as to form a zinc plating layer with a thickness of 12 μm on the surface of the busbar, and make the first wire blank; among them, the current density range of electroplating is 110 A / dm 2 , the additive is one or a mixture of maltose, lactose, dextrin and sucrose, and the concentration of the additive in the electroplating solution is 25 g / L;

[0146] S302: Stretch the first wire blank to make a second wire blank with a wire diameter specification of 0.5 mm. In this process, the dense and brittle zinc plating layer breaks, and the internal busbar extrudes from the fracture point through the zinc plating layer;

[0147] S303: Heat-treat the second wire blank. The heat treatment temperature is 350 °C and the heat treatment time is 3 h. The copper element in the busbar and the zinc element in the zinc plating layer diffuse with each other during the heat treatment process to form β-phase copper-zinc alloy and γ-phase copper-zinc alloy, and make the third wire blank. The third wire blank has a core material, β-phase copper-zinc alloy, γ-phase copper-zinc alloy and a surface layer from the inside to the outside in sequence;

[0148] S304: Stretch and stress-relieving anneal the third wire blank to make an electrode wire finished product with a wire diameter specification of 0.25 mm. The cross-section of the electrode wire finished product is referred to Figure 10 as shown in. The surface layer 3 is extruded and embedded into the intermediate layer 2 during the stretching process, forming a pit 20 on the intermediate layer 2 and forming a micro-pit 200 in the pit 20. The intermediate layer 2 extrudes the crack during the stretching process and makes the surface layer 3 discontinuously cover the outside of the intermediate layer 2, and part of the core material 1 can also be extruded from the fractured intermediate layer 2.

[0149] Applying the preparation method provided in the above-mentioned Embodiments 10 to 12, inside the made electrode wire finished product, the outer surface of the intermediate layer 2 has pits 20 and micro-pits 200 that can increase its surface area, and can improve its cutting efficiency during the wire electrical discharge machining process. As Figure 11 and Figure 12As shown, initially, there are cracks on the surface layer 3 of the electrode wire, which can expose the internal intermediate layer 2 (for this electrode wire, that is, the γ-phase copper-zinc alloy 23). As the wire electrical discharge machining progresses, the surface layer participates in the discharge corrosion and is consumed, and the intermediate layer below the surface layer is exposed. Pits and micropits on the surface of the intermediate layer can be seen. In addition, the intermediate layer has cracks in addition to pits and micropits. The strong electric field formed between the electrode wire and the workpiece will also have differences locally. The electric field will be further enhanced at the location where the crack 21 is formed. Therefore, the discharge will preferentially occur at the edge of the crack 21. Therefore, compared with the situation where no crack 21 is generated, applying the electrode wire with the crack 21 can improve the reaction time for the electrode wire to generate electric sparks, thereby accelerating the speed of wire electrical discharge machining. It should be noted that cracks can be generated on both the surface layer 3 and the intermediate layer 2 of this electrode wire. At the same time, since part of the core material and the β-phase copper-zinc alloy are exposed on the surface layer, the core material and the β-phase copper-zinc alloy can improve the discharge efficiency and further enhance the wire cutting speed. After the surface layer of this electrode wire participates in the discharge corrosion and is consumed, the γ-phase copper-zinc alloy is first exposed. Since the γ-phase copper-zinc alloy has a high zinc content, its gasification effect is good, which can improve the wire cutting speed.

[0150] Comparative Example 1: Purchase a brass electrode wire with a wire diameter specification of 0.25 mm on the market;

[0151] Comparative Example 2: Purchase an electrode wire with a wire diameter specification of 0.25 mm and a galvanized layer on the market;

[0152] Comparative Example 3: Purchase a gamma electrode wire with a wire diameter specification of 0.25 mm on the market;

[0153] The following table is a structural comparison table of the electrode wires made in Examples 1 to 12 and the electrode wires purchased in Comparative Examples 1 to 3:

[0154]

[0155] Use the electrode wires made in Examples 1 to 12 and the electrode wires purchased in Comparative Examples 1 to 3 to conduct wire electrical discharge machining tests. The test conditions are shown in the following table:

[0156]

[0157]

[0158] The test results are shown in the following table:

[0159]

[0160] Through test comparison, it can be known that the electrode wire prepared by the preparation method provided by the present invention, due to the pits and micropits in its internal intermediate layer, can significantly improve the performance of the electrode wire, and further improve the cutting speed of wire electrical discharge machining.

[0161] In the present invention, unless otherwise clearly defined or limited in the embodiments, terms such as "installation", "connection", "attachment" and "fixation" in the embodiments shall be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or integrated. It can be understood that it can also be a mechanical connection, an electrical connection, etc. Of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the communication inside two components, or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific implementation situations.

[0162] 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. An electrode wire for 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 an alloy, and the intermediate layer is a copper-zinc alloy; characterized in that, the surface of the intermediate layer has pits, the surface of the pits has micro-pits, the size of the micro-pits is smaller than the size of the pits where they are located, and the surface layer discontinuously covers the outside of the intermediate layer and fills the pits and micro-pits; Along the radial direction of the electrode wire, the depth of the pits is 0.1 - 20 μm, and the depth of the micro-pits is 0.05 - 10 μm.

2. The electrode wire for electric discharge machining according to claim 1, wherein, The thickness of the intermediate layer is 1 - 50 μm, and the thickness of the surface layer is 0.1 - 20 μm.

3. The electrode wire for electric discharge machining according to claim 2, wherein, The thickness of the intermediate layer is 5 - 40 μm, and the thickness of the surface layer is 0.1 - 15 μm.

4. The electrode wire for electric discharge machining according to claim 1, characterized in that, Along the radial direction of the electrode wire, the depth of the pits is 0.1 - 10 μm, and the depth of the micro-pits is 0.05 - 5 μm.

5. The electrode wire for electric discharge machining according to claim 1, characterized in that, The surface layer contains carbon element and zinc element.

6. The electrode wire for electric discharge machining according to claim 5, characterized in that, In terms of mass percentage, the carbon element content in the surface layer is ≥ 0.5%, and the zinc element content is ≥ 60%.

7. The electrode wire for electric discharge machining according to claim 1, characterized in that, The intermediate layer also has cracks.

8. The wire electrode for electric discharge machining according to claim 1, characterized in that, The intermediate layer and / or the core material are exposed at the discontinuities of the surface layer.

9. The electrode wire for electric discharge machining according to claim 1, characterized in that, The core material is copper or a copper alloy.

10. A method for preparing an electrode wire for electric discharge machining, characterized in that, Including the following steps: S100: Provide a pure copper bus bar or a copper alloy bus bar; S101: Galvanize the surface of the busbar. The electroplating solution includes additives, so as to form a galvanized layer on the surface of the busbar and make a first wire blank. Among them, the additive is a saccharide organic compound, and the current density range for electroplating is 5-150 A / dm 2 ; S102: Heat-treat the first wire blank, and the copper element in the bus bar and the zinc element in the galvanized layer diffuse into each other during the heat treatment process to form an intermediate layer, and make a second wire blank. The second wire blank has a core material, an intermediate layer, and a surface layer in sequence from the inside to the outside; S103: Stretch and stress-relieving anneal the second wire blank to make a finished electrode wire.

11. The preparation method of the electrode wire for electric discharge machining according to claim 10, characterized in that, The heat treatment temperature in the step S102 is 300 - 500 °C, and the heat treatment time is 1 - 50 h. The formed intermediate layer is β-phase copper-zinc alloy and / or β ’ -phase copper-zinc alloy.

12. A method for preparing an electrode wire for electric discharge machining, characterized in that, Including the following steps: S200: Provide a pure copper bus bar or a copper alloy bus bar; S201: Zinc is plated on the surface of the busbar. The electroplating solution contains additives, so as to form a zinc plating layer on the surface of the busbar to make the first wire blank. Among them, the additive is a saccharide organic compound, and the current density range of electroplating is 5 - 150 A / dm 2 ; S202: Heat-treat the first wire blank, and the copper element in the bus bar and the zinc element in the galvanized layer diffuse into each other during the heat treatment process to form a copper-zinc alloy layer, and make a second wire blank. The second wire blank has a core material, a copper-zinc alloy layer, and a surface layer in sequence from the inside to the outside; S203: Stretch the second wire blank to make a third wire blank; S204: Heat-treat the third wire blank to make a fourth wire blank. The fourth wire blank has a core material, an intermediate layer, and a surface layer in sequence from the inside to the outside; S205: Stretch and stress-relieving anneal the fourth wire blank to make a finished electrode wire.

13. The preparation method of the electrode wire for electric discharge machining according to claim 12, characterized in that, The heat treatment temperature in step S202 is 100 - 250 °C, the heat treatment time is 3 - 20 h, and the formed copper-zinc alloy layer includes γ-phase copper-zinc alloy.

14. The preparation method of the electrode wire for electrical discharge machining according to claim 12, characterized in that, The heat treatment temperature in the step S204 is 300 - 550 °C, the heat treatment time is 1 - 50 h, and the formed intermediate layer is β-phase copper-zinc alloy and / or β ’ -phase copper-zinc alloy.

15. A preparation method of an electrode wire for electric discharge machining, characterized in that, Including the following steps: S300: Provide a pure copper bus bar or a copper alloy bus bar; S301: Galvanize the surface of the busbar. The electroplating solution includes additives, so as to form a galvanized layer on the surface of the busbar and make the first wire blank. Among them, the additive is a saccharide organic compound, and the current density range of electroplating is 5 - 150 A / dm 2 ; S302: Stretch the first wire blank to make a second wire blank; S303: Heat-treat the second wire blank, and the copper element in the bus bar and the zinc element in the galvanized layer diffuse into each other during the heat treatment process to form an intermediate layer, and make a third wire blank. The third wire blank has a core material, an intermediate layer, and a surface layer in sequence from the inside to the outside; S304: Stretch and stress-relieving anneal the third wire blank to make a finished electrode wire.

16. The preparation method of the electrode wire for electric discharge machining according to claim 15, characterized in that, The heat treatment temperature in the step S303 is 200-500 °C, the heat treatment time is 1-50 h, and the formed intermediate layer is β-phase copper-zinc alloy and / or β ’ -phase copper-zinc alloy and / or γ-phase copper-zinc alloy.

17. The method for preparing an electrode wire for electric discharge machining according to any one of claims 10 to 16, characterized in that, The concentration of the additive in the electroplating solution is 8 - 25 g / L.

18. The preparation method of the electrode wire for electric discharge machining according to any one of claims 10 to 16, characterized in that, The saccharide organic compound is one or a mixture of more than one of maltose, lactose, dextrin, and sucrose.

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