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

Abstract

The present invention discloses an electrode wire for electric discharge wire cutting and a preparation method thereof, which includes a brass core material, and also includes a copper-zinc alloy layer and a surface layer outside the brass core material. The surface layer is distributed in a sheet-like or granular form on the surface of the copper-zinc alloy layer, and the copper-zinc alloy layer is exposed at the gaps between the sheet-like or granular forms of the surface layer. A number of micropores are distributed in the surface layer and at the interface between the surface layer and the copper-zinc alloy layer, and the size of the micropores in the surface layer is smaller than the size of the micropores at the interface between the surface layer and the copper-zinc alloy layer. During the preparation process, a zinc-plated layer is electroplated on the surface of the brass core material, a saccharide organic matter additive is added to the electroplating solution, and the first stretching extrusion, annealing heat treatment and the second stretching extrusion are carried out to obtain the finished electrode wire. The electrode wire for electric discharge machining of the present invention can improve the cutting processing speed.

Description

[0001] This application is a divisional application of the invention patent application with the application number 202111210891.X, the application date of October 18, 2021, and the invention name of "An electrode wire for electric discharge machining and its preparation method". Technical Field

[0002] The present invention relates to the technical field of wire electrical discharge machining, and specifically relates to an electrode wire for electric discharge machining and its preparation method. Background Art

[0003] Electric discharge machining, abbreviated as EDM (Electrical Discharge Machining), was first invented by Lazarenko in the Soviet Union in 1943. Its principle is to rely on the continuous electric sparks generated between the electrodes to erode the electrode material for machining.

[0004] Electric discharge machining can be divided into electric discharge profiling machining, electric discharge grinding machining, wire electrical discharge machining, etc. according to the form of the tool electrode and the running mode of the tool electrode relative to the workpiece.

[0005] The basic principle of wire electrical discharge machining is as follows. In order to generate electric sparks, a sufficiently strong voltage must be applied between the workpiece and the tool electrode, and this voltage should be higher than the breakdown voltage of the gap between the workpiece and the tool electrode. In the initial stage of applying voltage between the workpiece and the tool electrode, a very strong electric field will be generated, and positive and negative ions will gather at the closest position between the workpiece and the tool electrode. Under the action of the electric field, electrons and positive ions will be accelerated by the electric field to a very high speed. Electrons move towards the positive electrode, and positive ions move towards the negative electrode, forming an ionization channel and breaking down the insulating medium between the workpiece and the tool electrode. In this stage, countless collisions will occur between electrons and positive ions, and they will respectively impact the surfaces of the positive and negative electrodes at high speed. The kinetic energy is converted into heat energy, forming a plasma region and generating an extremely high temperature, which can reach 10,000 °C. Part of the materials on the workpiece and the tool electrode are instantaneously melted or vaporized by the high temperature, and corrosion pits are formed on both the workpiece and the tool electrode. At the same time, the liquid insulating medium between the workpiece and the tool electrode also vaporizes at high temperature. During the above process, the vaporization of the materials and the liquid medium will generate a bubble with a rapidly expanding volume. Then the current is interrupted, and the suddenly decreasing temperature causes the explosion of the bubble, flushing the remaining melted materials in the discharge pit into the liquid insulating medium. The materials eroded by the electric sparks are cooled in the liquid insulating medium, forming micro-spheres, which are washed away by the liquid insulating medium, and the intermittent insulation state is restored, forming a discharge cycle. This process is repeated tens of thousands to hundreds of thousands of times per second.

[0006] Wire electrical discharge machining (WEDM) can be further divided into fast wire WEDM and slow wire WEDM according to the material of the cutting wire and the wire feeding direction. Fast wire WEDM generally uses molybdenum wire with a high melting point, which moves reciprocally for discharge machining. Its advantages are low cost, but the disadvantages are that due to the loss of the molybdenum wire during repeated use, the machining accuracy and the surface finish of the machined part are poor. Slow wire WEDM is unidirectional wire feeding, and generally uses copper and copper alloy materials as the electrode wire. Because it is unidirectional wire feeding, the loss of the electrode wire can be compensated by wire feeding. Therefore, the cost is higher than that of fast wire WEDM. In general slow wire discharge machining, the first rough cut is followed by several finishing cuts, such as less than 7 times, to complete the machining process. Since multiple finishing cuts can be realized for precision machining, the dimensional accuracy of the cut workpiece is relatively high and the surface finish is relatively good.

[0007] For slow wire WEDM, improving the cutting speed, cutting accuracy and surface finish has always been pursued by users. The commonly used brass electrode wire in the market has a low cost and can meet the basic machining requirements, but its disadvantages are slow cutting speed, and the machining accuracy and surface finish are average. With the upgrading of the manufacturing industry and the increasing requirements for product quality, the brass electrode wire can no longer meet the needs. Therefore, more and more customers have begun to turn to using coated wires. The coated wires in the market can generally be divided into three categories according to the coating structure composition and uses.

[0008] The first category is high-precision coated wire. The coating of this type of coated wire is pure zinc or high-zinc alloy. Since zinc and high-zinc alloy have certain ductility, generally, the surface of the coating is smooth and the coating is thin. During precision finishing machining, the discharge is stable, which can reduce the micro-cracks generated on the workpiece due to the capacitance effect. The surface finish of the cut workpiece is good, and it is commonly used in precision machining with more than 4 cuts. The disadvantage is that the zinc coating is not resistant to electro-discharge corrosion and is easy to fall off, and the cutting speed is slow.

[0009] The second category is high-speed coated wire. The coating of this type of coated wire is generally β-phase or β + γ-phase, or β'+γ-phase or β'-phase composition. The coating is thick, more corrosion-resistant than the zinc coating, and the gasification flushing effect is strong and continuous, so the cutting speed is fast. The disadvantages are that the thick coating and the deep cracks seriously reduce the electrical conductivity of the electrode wire surface, causing the high-speed electrode wire to fail to discharge under the weak discharge energy during precision finishing, resulting in short circuits, and also making the discharge uniformity poor during precision finishing. Therefore, it is not suitable for precision machining with more than 4 cuts.

[0010] The third category is improved coated wire. This type of coated wire is faster than the high-precision coated wire and can also adapt to multi-pass precision finishing compared with the high-speed coated wire. It is a type of coated wire that is widely used in the current market.

[0011] Objectively speaking, users' pursuit of processing efficiency is eternal. However, the coated wires of the above existing technologies still have deficiencies in terms of cutting speed and other aspects. Summary of the Invention

[0012] One technical problem to be solved by the present invention is to provide an electrode wire for electric discharge machining, which can improve the cutting speed.

[0013] One technical solution of the present invention is to provide an electrode wire for electric discharge machining, including a brass core material, and further including a copper-zinc alloy layer and a surface layer outside the brass core material; the surface layer is distributed in a sheet or granular form on the surface of the copper-zinc alloy layer, and the copper-zinc alloy layer is exposed at the gaps between the sheet or granular forms of the surface layer; a number of micropores are distributed in the surface layer and at the interface between the surface layer and the copper-zinc alloy layer, and the size of the micropores in the surface layer is smaller than the size of the micropores at the interface between the surface layer and the copper-zinc alloy layer.

[0014] After adopting the above structure, the electrode wire for electric discharge machining of the present invention has the following advantages:

[0015] A number of micropores are distributed in the surface layer and at the interface between the surface layer and the copper-zinc alloy layer. The micropores greatly increase the contact area between the surface of the electrode wire and the liquid insulating medium, further improving the cooling effect of the electrode wire, and can significantly improve the cutting speed of the electrode wire during rough machining. Moreover, the surface layer distributed in a sheet or granular form on the surface of the electrode wire can effectively improve the persistence of the flushing effect during the discharge process, thereby ensuring the high cutting speed of the electrode wire of the present invention.

[0016] Further, the size of each micropore in the cross-section of the electrode wire is 0.01 - 2.8 μm.

[0017] Further, the surface layer covers 60% - 95% of the surface area of the copper-zinc alloy layer. After adopting the above structure, relatively speaking, the larger the area of the surface layer covering the surface of the electrode wire, the faster the cutting speed and the better the surface finish of the cut workpiece.

[0018] Further, the thickness of the surface layer is 2 - 7 μm. After adopting the above structure, the thickness of the covering layer is in the preferred range, which can maintain the conductivity required for fine machining, and enable the ionization channel to be smoothly formed within a discharge cycle during fine machining, generating electric discharge machining, so that the tool dressing is in place to further improve the surface finish of the cut workpiece.

[0019] Further, the component of the copper-zinc alloy layer is β'+γ phase or β' phase. After adopting the above phase structure, the gasification flushing effect and persistence of the electrode wire of the present invention are further enhanced, thereby further improving the cutting speed.

[0020] Further, the thickness of the copper-zinc alloy layer is 4-10 μm. After adopting the above thickness of the copper-zinc alloy layer, the gasification flushing effect and sustainability of the electrode wire of the present invention are further enhanced, and the cutting speed is further improved.

[0021] Another technical problem to be solved by the present invention is to provide a preparation method for an electrode wire for electric discharge machining according to any one of the above technical solutions. The prepared electrode wire includes a brass core, a copper-zinc alloy layer outside the brass core, and a surface layer. The surface layer is distributed in a sheet or granular form on the surface of the copper-zinc alloy layer, and the copper-zinc alloy layer is exposed at the gaps between the sheets or granules of the surface layer. A number of micropores are distributed in the surface layer and at the interface between the surface layer and the copper-zinc alloy layer, and the size of the micropores in the surface layer is smaller than the size of the micropores at the interface between the surface layer and the copper-zinc alloy layer. This electrode wire can improve the cutting processing speed.

[0022] Another technical solution of the present invention is to provide a preparation method for an electrode wire for electric discharge machining according to any one of the above technical solutions, including the following steps:

[0023] 1) Prepare a brass core with a diameter of 0.6-0.9 mm;

[0024] 2) Electroplate a zinc coating on the surface of the brass core obtained in step 1), and add a saccharide organic additive to the electroplating solution to obtain a dense and brittle zinc coating containing the saccharide organic additive component. The concentration of the saccharide organic additive is 8-25 g / L;

[0025] 3) Subject the wire blank obtained after electroplating to the first stretching and extrusion through a wire drawing die to a diameter of 0.47-0.62 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° with the axis, and obtain a wire blank obtained by the first stretching and extrusion with a zinc coating having a number of cracks;

[0026] 4) Heat-treat the wire blank obtained by the first stretching and extrusion with a number of cracks to obtain a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with a number of cracks;

[0027] 5) Subject the heat-treated wire blank to the second stretching and extrusion through a wire drawing die to obtain an electrode wire finished product with a diameter of 0.15-0.30 mm.

[0028] After adopting the above steps, the prepared electrode wire for electric discharge machining includes a brass core, a copper-zinc alloy layer outside the brass core, and a surface layer. The surface layer is distributed in a sheet or granular form on the surface of the copper-zinc alloy layer, and the copper-zinc alloy layer is exposed at the gaps between the sheets or granules of the surface layer. A number of micropores are distributed in the surface layer and at the interface between the surface layer and the copper-zinc alloy layer, and the size of the micropores in the surface layer is smaller than the size of the micropores at the interface between the surface layer and the copper-zinc alloy layer.

[0029] The electrode wire material prepared by the above method has micropores distributed in the surface layer and at the interface between the surface layer and the copper-zinc alloy layer. The micropores greatly increase the contact area between the surface of the electrode wire and the liquid insulating medium, further improving the cooling effect of the electrode wire, significantly enhancing the cutting speed of the electrode wire during rough machining, and the surface layer distributed in flakes or particles on the surface of the electrode wire can effectively improve the persistence of the flushing effect during the discharge process, thereby ensuring the high cutting speed of the electrode wire of the present invention.

[0030] Further, in step 1), the electroplating speed is 200 - 400 m / min, the current is 965 - 1350 A, the voltage is 5.2 - 7 V, and the thickness of the galvanized layer is 4.5 - 9 μm.

[0031] Further, in step 4), the heat treatment temperature is 200 - 400 °C, the heat treatment time is 2 h - 10 h, it is cooled in the furnace to below 150 °C before taking out of the furnace, and air is continuously filled during the heat treatment process.

[0032] Further, the saccharide organic additive is sucrose, lactose, and / or maltose. After adopting the above steps, the density and brittleness of the galvanized layer in step 2) are better.

[0033] Further, in step 3), the first drawing and extrusion processing rate is 35% - 65%; in step 5), the second drawing and extrusion processing rate is 55% - 95%. After adopting the above steps, the wire blank with a dense and brittle galvanized layer obtained by the first drawing and extrusion can be further cracked along a direction perpendicular to the axis and at an acute angle greater than 30° with the axis, so as to ensure the coverage rate of the surface layer, and it can ensure that the surface layer of the electrode wire after the second drawing and extrusion is distributed in flakes or particles more in line with the requirements of fast cutting speed and high surface finish. It is not difficult to understand that the acute angle greater than 30° is an acute angle above 30° and below 90°.

[0034] Additional aspects and advantages of the present invention will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of the outer shape structure of the wire blank with a galvanized layer having several cracks obtained by the first drawing and extrusion of the electrode wire of the present invention.

[0036] Figure 2 is a schematic diagram of the cross-sectional structure of the wire blank with a galvanized layer having several cracks obtained by the first drawing and extrusion of the electrode wire of the present invention.

[0037] Figure 3 is a schematic diagram of the cross-sectional structure of the wire blank after heat treatment of the wire blank obtained by the first drawing and extrusion of the electrode wire of the present invention.

[0038] Figure 4 It is a schematic cross-sectional structure diagram of the finished electrode wire obtained by the second stretching and extrusion of the electrode wire of the present invention.

[0039] As shown in the figure: 1, crack; 2, brass core; 3, galvanized layer; 4, surface layer; 5, copper-zinc alloy layer; 6, micropores. Detailed implementation manners

[0040] The following further describes the detailed implementation manners of the present invention with reference to the accompanying drawings. It should be noted here that the description of these detailed implementation manners is used to help understand the present invention, but does not constitute a limitation on the present invention. In addition, the technical features involved in the following detailed implementation manners of the present invention can be combined with each other as long as they do not conflict with each other.

[0041] Such as Figure 1 , Figure 2 , Figure 3 , Figure 4 shown.

[0042] Before giving the specific embodiments of the electrode wire for electric discharge machining of the present invention, some supplementary explanations are made on the structural features, composition and preparation principle of the electrode wire for electric discharge machining of the present invention and its preparation method.

[0043] The above-mentioned brass core 2 generally uses cores such as CuZn37 brass or CuZn40 brass.

[0044] The flakes distributed on the surface of the electrode wire can also be understood as blocks.

[0045] The Chinese name of CuO is copper oxide. The Chinese name of ZnO is zinc oxide. The Chinese name of Cu2(OH)2CO3 is basic copper carbonate, commonly known as copper green.

[0046] The wire blank obtained by the first drawing and extrusion to obtain a galvanized layer 3 with several cracks 1 can be understood as follows: The galvanized layer of the electrode wire in the prior art has good ductility and plastic toughness without adding sugar organic additives. When it is drawn and extruded by a wire drawing die, the galvanized layer will become uniformly thinner, but no cracks will appear. In other words, in the electroplating process of the prior art in the electrode wire industry, boric acid and aluminum sulfate are generally added as pH buffers, and ammonium chloride is added as a conductive salt. Whether it is boric acid, aluminum sulfate, or ammonium chloride, etc., they are all non-sugar inorganic additives. In the present invention, inorganic additives such as boric acid, aluminum sulfate, and ammonium chloride are not added during the electroplating process, but sugar organic additives are added. The sugar organic additive can adsorb and inhibit the cathodic reduction reaction of zinc ions, increasing the cathodic polarization effect, making the crystallization rate of the galvanized layer slower, and the grains of the coating finer, and a dense, hard and brittle galvanized layer can be obtained. At the same time, the sugar organic additive is adsorbed in the galvanized layer, increasing the internal stress of the coating, making the hardness and brittleness of the galvanized layer increase. Therefore, the dense and hard and brittle galvanized layer is very easy to break when it is drawn and extruded by a wire drawing die, that is, several cracks 1 or several cracks 1 appear. The cracks 1 will crack perpendicular to the axis and at an acute angle with the axis, such as greater than 30°. Relative to the axis of the electrode wire, the cracks can be understood as transverse cracks and oblique cracks.

[0047] From another aspect: The process of electroplating to form metal crystals can be divided into two processes that occur simultaneously: the formation of crystal nuclei, that is, the generation of crystal nuclei, and the crystal growth process. The speed of these two processes determines the fineness of metal crystallization. During the electroplating process, when the generation rate of crystal nuclei is greater than the growth rate of crystal nuclei, a dense and closely arranged coating can be obtained. During the electroplating process, when adsorption occurs on the local surface of the electrode, it is quite difficult to carry out the electrode reaction on this part of the electrode surface. The electrode reaction either stops or slows down, which is equivalent to reducing the effective area of the electrode, increasing the effective current density passing through the electrode, and thus increasing the polarization effect. At the same time, when adsorption occurs on the entire surface of the electrode, the reaction particles have to pass through the adsorption layer on the interface before they can react, making the electrode reaction more difficult, which is equivalent to the electro-chemical reaction process being blocked, thus increasing the polarization effect. It is not difficult to understand that the electrode mentioned in this paragraph refers to the brass core material prepared in step 1). The present invention increases the generation rate of crystal nuclei by increasing the cathodic polarization effect during metal crystallization, facilitating the obtaining of a dense crystal coating. The galvanized layer that is dense in crystal and adsorbed with sugar organic additives will become quite hard and brittle and is very easy to break when it is drawn and extruded by a wire drawing die, that is, several cracks 1 appear.

[0048] The sugar organic additives described above are preferably sucrose, lactose, or / and maltose. It should be understood that it can be sucrose alone, or lactose alone, or maltose alone, or a mixture of two of them, or a mixture of all three of them.

[0049] A number of micropores 6 are distributed in the surface layer 4. During the electroplating process, the zinc plating layer 3 gradually thickens, the metal continuously crystallizes and grows, and then the sugar organic additive will be evenly adsorbed in the zinc plating layer 3. Therefore, the sugar organic additive in the zinc plating layer 3 decomposes at high temperature to generate micropores 6. The micropores 6 inside the surface layer 4 are more evenly distributed and smaller in size compared to the micropores 6 at the interface between the surface layer 4 and the alloy layer 5. The micropores 6 are also called microporous structures.

[0050] At the beginning of electroplating, the sugar organic additive will first be adsorbed on the outer surface of the brass core 2. The surface of the brass core 2 is not completely smooth, and there will inevitably be some defects on the surface of the brass core 2 during the preparation process, such as wire flow, scratches, etc. Therefore, more sugar organic additive is adsorbed at the defective parts on the surface of the brass core 2. After the first stretching extrusion and heat treatment, the copper-zinc alloy layer 5 and the surface layer 4 are formed. At this time, the sugar organic additive adsorbed at the defective parts on the original surface of the brass core 2 decomposes at high temperature during the heat treatment and appears at their interface to form micropores 6 with larger sizes and less uniform distribution. The surface layer 4 can also be called the covering layer.

[0051] The following further details an electrode wire for electrical discharge wire cutting and its preparation method according to the present invention with reference to embodiments.

[0052] Example 1

[0053] The preparation process is as follows:

[0054] 1) Prepare a CuZn37 brass core with a diameter of 0.82 mm.

[0055] 2) Electroplate a zinc plating layer on the surface of the brass core obtained in step 1). Add a sugar organic additive to the electroplating solution. The sugar organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 6.8 μm, the concentration of the sugar organic additive is 25 g / L, the electroplating speed is 240 m / min, the current is 1200 A, and the voltage is 6.2 V.

[0056] The electroplating solution formula is prior art, such as zinc sulfate 450 - 550 g / L. The same applies to the following Examples 2 - 15. For the sake of brevity, it will not be repeated in the following Examples 2 - 15. The present invention adds a sugar organic additive to this electroplating solution formula (the concentration of the sugar organic additive in this example is 25 g / L).

[0057] 3) The wire blanks obtained after electroplating are subjected to the first stretching and extrusion through a wire drawing die until the diameter reaches 0.6 mm. The dense and brittle zinc coating will crack along the direction perpendicular to the axis and at an acute angle greater than 30° with the axis, obtaining wire blanks with a zinc coating having several cracks after the first stretching and extrusion.

[0058] 4) The wire blanks obtained after the first stretching and extrusion with several cracks are heat-treated at a heat treatment temperature of 400 °C for a heat treatment time of 6 h, cooled in the furnace to below 150 °C and then taken out of the furnace. Air is continuously filled during the heat treatment process, obtaining heat-treated wire blanks with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0059] The heat treatment principle and process in step 4) are briefly described as follows: In the early stage of heat treatment, copper in the brass core material diffuses with zinc in the coating to form a zinc-copper alloy, and at this time the copper content is relatively low. At the same time, the sugar organic additives in the coating will decompose to produce C (carbon) and H2O (water) at high temperature because the dense coating isolates O2 (oxygen) in the environment. Then, micro-pores are formed in the coating. After that, O2 in the air atmosphere in the furnace penetrates into the coating from the outside to the inside along the micro-pores, reacts with C in the micro-pores to generate CO2, and reacts with copper and zinc around the micro-pores to generate CuO and ZnO. Due to the barrier of the micro-pores, copper in the core material cannot continue to diffuse into the coating. Therefore, with the micro-pores as the boundary, a copper-zinc alloy layer outside the brass core material and a surface layer are formed. Among them, the micro-pores in the surface layer are smaller in size, and the micro-pores at the interface between the surface layer and the alloy layer are larger in size.

[0060] At the same time, since the surface layer cannot be supplemented with copper elements from the brass core material, in the subsequent heat treatment process, in the area of the surface layer far from the micro-pores, copper and zinc elements form Cu-Zn intermetallic compounds at high temperature. Since there is no barrier of micro-pores in the copper-zinc alloy layer, copper and zinc elements can diffuse with the brass core material unhindered, forming a stable β' phase or β'+γ phase. It is not difficult to understand that β' is the low-temperature phase of the β phase, and the β phase is the high-temperature phase, and the two transform into each other with the change of temperature. During the cooling process, a part of the copper on the outer layer of the surface layer reacts with O2, CO2, and H2O in the environment to generate CuO and Cu2(OH)2CO3, thus obtaining heat-treated wire blanks with a continuous copper-zinc alloy layer and a surface layer with several cracks. The heat treatment principle and process described in the above two paragraphs are the same as those in the following Examples 2-15. For the sake of brevity, they will not be repeated in the following Examples 2-15.

[0061] 5) The heat-treated wire blank is subjected to a second drawing and extrusion through a wire drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and a copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. The surface layer coverage rate is 77%, the surface layer thickness is 4 μm, the size of each micropore in the surface layer (including the micropores in the surface layer and between the surface layer and the copper-zinc alloy layer, the same applies to Examples 2-15 below and will not be elaborated further) is 0.078-1.8 μm, the mass fraction of CuO in the surface layer is 4.3%, the mass fraction of ZnO is 53.8%, the mass fraction of Cu2(OH)2CO3 is 9.3%, the mass fraction of the Cu-Zn intermetallic compound is 32.6%, the thickness of the copper-zinc alloy layer is 8 μm, and the composition of the copper-zinc alloy layer is the β' phase.

[0062] Example 2

[0063] The preparation process is as follows:

[0064] 1) Prepare a CuZn40 brass core material with a diameter of 0.9 mm.

[0065] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1). Add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 9 μm, the concentration of the saccharide organic additive is 28 g / L, the electroplating speed is 200 m / min, the current is 1350 A, and the voltage is 7 V.

[0066] 3) The wire blank obtained after electroplating is subjected to a first drawing and extrusion through a wire drawing die to a diameter of 0.62 mm. The dense and brittle zinc coating will crack along the direction perpendicular to the axis and at an acute angle greater than 30° to the axis, obtaining a wire blank after the first drawing with a zinc coating having several cracks.

[0067] 4) The wire blank obtained after the first drawing and extrusion with several cracks is heat-treated. The heat treatment temperature is 400 °C, the heat treatment time is 10 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously filled during the heat treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0068] 5) The heat-treated wire blank is subjected to a second drawing and extrusion through a drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and a copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. The surface layer coverage rate is 80%, the surface layer thickness is 7 μm, the size of each micropore in the surface layer is 0.080 - 2.8 μm, the mass fraction of CuO in the surface layer is 4%, the mass fraction of ZnO is 55%, the mass fraction of Cu2(OH)2CO3 is 10%, the mass fraction of Cu-Zn intermetallic compound is 31%, the thickness of the copper-zinc alloy layer is 10 μm, and the composition of the copper-zinc alloy layer is β' phase.

[0069] Example 3

[0070] The preparation process is as follows:

[0071] 1) Prepare a CuZn37 brass core material with a diameter of 0.8 mm.

[0072] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1). Add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 6.5 μm, the concentration of the saccharide organic additive is 22 g / L, the electroplating speed is 250 m / min, the current is 1150 A, and the voltage is 6.5 V.

[0073] 3) The electroplated wire blank is subjected to a first drawing and extrusion through a drawing die to a diameter of 0.6 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° to the axis, obtaining a wire blank after the first drawing with a zinc coating having several cracks.

[0074] 4) The wire blank after the first drawing with several cracks is heat-treated. The heat treatment temperature is 320 °C, the heat treatment time is 3.5 h, and it is cooled in the furnace to below 150 °C and then taken out of the furnace. Air is continuously filled during the heat treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0075] 5) The heat-treated wire blank is subjected to a second drawing and extrusion through a drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and a copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. The surface layer coverage rate is 78%, the surface layer thickness is 3 μm, the size of each micropore in the surface layer is 0.035 - 1.6 μm, the mass fraction of CuO in the surface layer is 7.2%, the mass fraction of ZnO is 48.7%, the mass fraction of Cu2(OH)2CO3 is 5.1%, the mass fraction of Cu-Zn intermetallic compound is 39%, the thickness of the copper-zinc alloy layer is 6.8 μm, and the composition of the copper-zinc alloy layer is β'+γ phase.

[0076] Example 4

[0077] The preparation process is as follows:

[0078] 1) Prepare a CuZn37 brass core material with a diameter of 0.8 mm.

[0079] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1). Add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 7.8 μm, the concentration of the saccharide organic additive is 26 g / L, the electroplating speed is 235 m / min, the current is 1260 A, and the voltage is 6.7 V.

[0080] 3) Subject the wire blank obtained after electroplating to the first stretching and extrusion through a wire drawing die to a diameter of 0.61 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° to the axis, obtaining a wire blank after the first stretching with a zinc coating having several cracks.

[0081] 4) Heat-treat the wire blank after the first stretching with several cracks. The heat-treatment temperature is 350 °C, the heat-treatment time is 10 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously filled during the heat-treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0082] 5) Subject the heat-treated wire blank to the second stretching and extrusion through a wire drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and with the copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. Among them, the surface layer coverage rate is 82%, the surface layer thickness is 5.6 μm, the size of each micropore in the surface layer is 0.06 - 1.75 μm, the mass fraction of CuO in the surface layer is 5.2%, the mass fraction of ZnO is 51.8%, the mass fraction of Cu2(OH)2CO3 is 7.8%, the mass fraction of the Cu-Zn intermetallic compound is 35.2%, the thickness of the copper-zinc alloy layer is 8.3 μm, and the component of the copper-zinc alloy layer is β' phase.

[0083] Example 5

[0084] The preparation process is as follows:

[0085] 1) Prepare a CuZn40 brass core material with a diameter of 0.78 mm.

[0086] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1). Add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 6.3 μm, the concentration of the saccharide organic additive is 20 g / L, the electroplating speed is 270 m / min, the current is 1080 A, and the voltage is 5.9 V.

[0087] 3) Subject the wire blank obtained after electroplating to the first drawing and extrusion through a drawing die until the diameter reaches 0.6 mm. The dense and brittle zinc coating will crack along the direction perpendicular to the axis and at an acute angle greater than 30° with the axis, obtaining a wire blank obtained from the first drawing with a zinc coating having several cracks.

[0088] 4) Heat-treat the wire blank obtained from the first drawing with several cracks. The heat-treatment temperature is 375 °C, the heat-treatment time is 5 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously filled during the heat-treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0089] 5) Subject the heat-treated wire blank to the second drawing and extrusion through a drawing die until it reaches 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and with the copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. Among them, the surface layer coverage rate is 85%, the surface layer thickness is 3.5 μm, the size of each micropore in the surface layer is 0.05 - 1.78 μm, the mass fraction of CuO in the surface layer accounts for 4.9%, the mass fraction of ZnO accounts for 52.4%, the mass fraction of Cu2(OH)2CO3 accounts for 8.2%, the mass fraction of the Cu-Zn intermetallic compound accounts for 34.5%, the thickness of the copper-zinc alloy layer is 6.3 μm, and the composition of the copper-zinc alloy layer is the β' phase.

[0090] Example 6

[0091] The preparation process is as follows:

[0092] 1) Prepare a CuZn37 brass core material with a diameter of 0.76 mm.

[0093] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1). Add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 6.1 μm, the concentration of the saccharide organic additive is 24 g / L, the electroplating speed is 275 m / min, the current is 1090 A, and the voltage is 6 V.

[0094] 3) Subject the wire blank obtained after electroplating to the first drawing and extrusion through a drawing die until the diameter reaches 0.57 mm. The dense and brittle zinc coating will crack along the direction perpendicular to the axis and at an acute angle greater than 30° with the axis, obtaining a wire blank obtained from the first drawing with a zinc coating having several cracks.

[0095] 4) Heat-treat the wire blank obtained from the first stretching with several cracks. The heat-treatment temperature is 330 °C, the heat-treatment time is 3 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously introduced during the heat-treatment process to obtain a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0096] 5) The heat-treated wire blank is subjected to a second stretching and extrusion through a wire drawing die to 0.25 mm to obtain a finished electrode wire with a surface layer distributed in flakes or particles and a copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. Among them, the surface layer coverage rate is 81%, the surface layer thickness is 3.4 μm, the size of each micropore in the surface layer is 0.038 - 1.65 μm, the mass fraction of CuO in the surface layer is 6.8%, the mass fraction of ZnO is 49.6%, the mass fraction of Cu2(OH)2CO3 is 5.8%, the mass fraction of Cu-Zn intermetallic compound is 37.8%, the thickness of the copper-zinc alloy layer is 6 μm, and the composition of the copper-zinc alloy layer is β'+γ phase.

[0097] Example 7

[0098] The preparation process is as follows:

[0099] 1) Prepare a CuZn37 brass core material with a diameter of 0.74 mm.

[0100] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1). Add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 5.9 μm, the concentration of the saccharide organic additive is 18 g / L, the electroplating speed is 280 m / min, the current is 1030 A, and the voltage is 5.8 V.

[0101] 3) The wire blank obtained after electroplating is subjected to a first stretching and extrusion through a wire drawing die to a diameter of 0.56 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° with the axis, and a wire blank obtained from the first stretching with a zinc coating having several cracks is obtained.

[0102] 4) Heat-treat the wire blank obtained from the first stretching with several cracks. The heat-treatment temperature is 300 °C, the heat-treatment time is 4.5 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously introduced during the heat-treatment process to obtain a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0103] 5) The heat-treated wire blank is subjected to a second drawing and extrusion through a wire drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and a copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. Among them, the surface layer coverage rate is 76%, the surface layer thickness is 2.8 μm, the size of each micropore in the surface layer is 0.024 - 1.62 μm, the mass fraction of CuO in the surface layer is 8.0%, the mass fraction of ZnO is 46.9%, the mass fraction of Cu2(OH)2CO3 is 4.1%, the mass fraction of Cu-Zn intermetallic compound is 41%, the copper-zinc alloy layer thickness is 6.2 μm, and the copper-zinc alloy layer composition is β'+γ phase.

[0104] Example 8

[0105] The preparation process is as follows:

[0106] 1) Prepare a CuZn37 brass core material with a diameter of 0.72 mm.

[0107] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1), and add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 5.8 μm, the concentration of the saccharide organic additive is 16 g / L, the electroplating speed is 285 m / min, the current is 1020 A, and the voltage is 5.75 V.

[0108] 3) The wire blank obtained after electroplating is subjected to a first drawing and extrusion through a wire drawing die to a diameter of 0.55 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° to the axis, obtaining a wire blank after the first drawing with a zinc coating having several cracks.

[0109] 4) The wire blank obtained after the first drawing with several cracks is heat-treated. The heat treatment temperature is 340 °C, the heat treatment time is 8 h, and it is cooled in the furnace to below 150 °C and then taken out of the furnace. Air is continuously filled during the heat treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0110] 5) The heat-treated wire blank is subjected to a second drawing and extrusion through a wire drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and a copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. Among them, the surface layer coverage rate is 86%, the surface layer thickness is 3.2 μm, the size of each micropore in the surface layer is 0.042 - 1.68 μm, the mass fraction of CuO in the surface layer is 5.6%, the mass fraction of ZnO is 51.5%, the mass fraction of Cu2(OH)2CO3 is 7.4%, the mass fraction of Cu-Zn intermetallic compound is 35.5%, the copper-zinc alloy layer thickness is 5.9 μm, and the copper-zinc alloy layer composition is β' phase.

[0111] Example 9

[0112] The preparation process is as follows:

[0113] 1) Prepare a CuZn40 brass core material with a diameter of 0.7 mm.

[0114] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1). Add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 5.5 μm, the concentration of the saccharide organic additive is 15 g / L, the electroplating speed is 300 m / min, the current is 990 A, and the voltage is 5.7 V.

[0115] 3) Subject the wire blank obtained after electroplating to the first drawing and extrusion through a drawing die to a diameter of 0.53 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° to the axis, obtaining a wire blank after the first drawing with a zinc coating having several cracks.

[0116] 4) Heat-treat the wire blank after the first drawing with several cracks. The heat-treatment temperature is 285 °C, the heat-treatment time is 5.5 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously filled during the heat-treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0117] 5) Subject the heat-treated wire blank to the second drawing and extrusion through a drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and with the copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. Among them, the surface layer coverage rate is 80%, the surface layer thickness is 2.5 μm, the size of each micropore in the surface layer is 0.017 - 1.25 μm, the mass fraction of CuO in the surface layer is 8.4%, the mass fraction of ZnO is 46.2%, the mass fraction of Cu2(OH)2CO3 is 3.6%, the mass fraction of the Cu-Zn intermetallic compound is 41.8%, the thickness of the copper-zinc alloy layer is 6 μm, and the composition of the copper-zinc alloy layer is β'+γ phase.

[0118] Example 10

[0119] The preparation process is as follows:

[0120] 1) Prepare a CuZn37 brass core material with a diameter of 0.68 mm.

[0121] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1), and add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 5.4 μm, the concentration of the saccharide organic additive is 15 g / L, the electroplating speed is 320 m / min, the current is 988 A, and the voltage is 5.68 V.

[0122] 3) Perform the first stretching and extrusion of the wire blank obtained after electroplating through a wire drawing die to a diameter of 0.53 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° with the axis, obtaining a wire blank after the first stretching with a zinc coating having several cracks.

[0123] 4) Heat-treat the wire blank obtained after the first stretching with several cracks. The heat-treatment temperature is 330 °C, the heat-treatment time is 9 h, and it is cooled in the furnace to below 150 °C before taking out of the furnace. Air is continuously filled during the heat-treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0124] 5) Perform the second stretching and extrusion of the heat-treated wire blank through a wire drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and with the copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. The surface layer coverage rate is 95%, the surface layer thickness is 2.9 μm, the size of each micropore in the surface layer is 0.036 - 1.4 μm, the mass fraction of CuO in the surface layer is 5.9%, the mass fraction of ZnO is 50.9%, the mass fraction of Cu2(OH)2CO3 is 7.1%, the mass fraction of the Cu-Zn intermetallic compound is 36.1%, the thickness of the copper-zinc alloy layer is 5.8 μm, and the composition of the copper-zinc alloy layer is the β' phase.

[0125] Example 11

[0126] The preparation process is as follows:

[0127] 1) Prepare a CuZn37 brass core material with a diameter of 0.66 mm.

[0128] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1), and add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 5.3 μm, the concentration of the saccharide organic additive is 12 g / L, the electroplating speed is 345 m / min, the current is 985 A, and the voltage is 5.65 V.

[0129] 3) Perform the first stretching and extrusion of the wire blank obtained after electroplating through a wire drawing die to a diameter of 0.51 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° with the axis, obtaining a wire blank after the first stretching with a zinc coating having several cracks.

[0130] 4) Heat-treat the wire blank obtained from the first drawing with several cracks. The heat-treatment temperature is 280 °C, the heat-treatment time is 6 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously filled during the heat-treatment process to obtain a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0131] 5) Secondarily draw and extrude the heat-treated wire blank through a wire-drawing die to 0.25 mm to obtain a finished electrode wire with a surface layer distributed in flakes or particles and with the copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. Among them, the surface layer coverage rate is 75%, the surface layer thickness is 2.3 μm, the size of each micropore in the surface layer is 0.014 - 1.22 μm, the mass fraction of CuO in the surface layer accounts for 8.7%, the mass fraction of ZnO accounts for 45.7%, the mass fraction of Cu₂(OH)₂CO₃ accounts for 3.3%, the mass fraction of the Cu-Zn intermetallic compound accounts for 42.3%, the thickness of the copper-zinc alloy layer is 5.5 μm, and the component of the copper-zinc alloy layer is β'+γ phase.

[0132] Example 12

[0133] The preparation process is as follows:

[0134] 1) Prepare a CuZn37 brass core material with a diameter of 0.66 mm.

[0135] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1). Add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 5.2 μm, the concentration of the saccharide organic additive is 11 g / L, the electroplating speed is 350 m / min, the current is 980 A, and the voltage is 5.6 V.

[0136] 3) First draw and extrude the wire blank obtained after electroplating through a wire-drawing die to a diameter of 0.5 mm. The dense and brittle zinc coating will crack along the direction perpendicular to the axis and at an acute angle greater than 30° to the axis, and obtain a wire blank obtained from the first drawing with a zinc coating with several cracks.

[0137] 4) Heat-treat the wire blank obtained from the first drawing with several cracks. The heat-treatment temperature is 320 °C, the heat-treatment time is 8 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously filled during the heat-treatment process to obtain a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0138] 5) The heat-treated wire blank is subjected to a second drawing and extrusion through a wire drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or granules and a copper-zinc alloy layer exposed at the gaps between the flakes or granules on the surface layer. The surface layer coverage rate is 89%, the surface layer thickness is 2.6 μm, the size of each micropore in the surface layer is 0.024 - 1.18 μm, the mass fraction of CuO in the surface layer is 6.4%, the mass fraction of ZnO is 50.3%, the mass fraction of Cu2(OH)2CO3 is 6.6%, the mass fraction of Cu-Zn intermetallic compound is 36.7%, the thickness of the copper-zinc alloy layer is 5.3 μm, and the composition of the copper-zinc alloy layer is β' phase.

[0139] Example 13

[0140] The preparation process is as follows:

[0141] 1) Prepare a CuZn40 brass core material with a diameter of 0.65 mm.

[0142] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1), and add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 5.1 μm, the concentration of the saccharide organic additive is 11 g / L, the electroplating speed is 360 m / min, the current is 975 A, and the voltage is 5.55 V.

[0143] 3) The wire blank obtained after electroplating is subjected to a first drawing and extrusion through a wire drawing die to a diameter of 0.49 mm. The dense and brittle zinc coating will crack along the direction perpendicular to the axis and at an acute angle greater than 30° with the axis, obtaining a wire blank after the first drawing with a zinc coating having several cracks.

[0144] 4) The wire blank after the first drawing with several cracks is heat-treated. The heat treatment temperature is 320 °C, the heat treatment time is 2 h, and it is cooled in the furnace to below 150 °C and then taken out of the furnace. Air is continuously filled during the heat treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0145] 5) The heat-treated wire blank is subjected to a second drawing and extrusion through a wire drawing die to 0.25 mm, obtaining a finished electrode wire with a surface cover layer distributed in flakes or granules and a copper-zinc alloy layer exposed at the gaps between the flakes or granules on the surface layer. The surface layer coverage rate is 76%, the surface layer thickness is 2.2 μm, the size of each micropore in the surface layer is 0.015 - 1.05 μm, the mass fraction of CuO in the surface layer is 7.8%, the mass fraction of ZnO is 47.6%, the mass fraction of Cu2(OH)2CO3 is 4.5%, the mass fraction of Cu-Zn intermetallic compound is 40.1%, the thickness of the copper-zinc alloy layer is 5.2 μm, and the composition of the copper-zinc alloy layer is β'+γ phase.

[0146] Example 14

[0147] The preparation process is as follows:

[0148] 1) Prepare a CuZn37 brass core material with a diameter of 0.63 mm.

[0149] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1). Add a saccharide organic additive to the electroplating solution. The saccharide organic additive is sucrose or / and lactose or / and maltose. The coating thickness is 5 μm, the concentration of the saccharide organic additive is 10 g / L, the electroplating speed is 385 m / min, the current is 970 A, and the voltage is 5.5 V.

[0150] 3) Subject the wire blank obtained after electroplating to the first drawing and extrusion through a drawing die to a diameter of 0.47 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° with the axis, obtaining a wire blank after the first drawing with a zinc coating having several cracks.

[0151] 4) Heat-treat the wire blank after the first drawing with several cracks. The heat-treatment temperature is 260 °C, the heat-treatment time is 4 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously filled during the heat-treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0152] 5) Subject the heat-treated wire blank to the second drawing and extrusion through a drawing die to 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and with the copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. Among them, the surface layer coverage rate is 72%, the surface layer thickness is 2.1 μm, the size of each micropore in the surface layer is 0.012 - 0.95 μm, the mass fraction of CuO in the surface layer is 9.2%, the mass fraction of ZnO is 44.6%, the mass fraction of Cu2(OH)2CO3 is 2.7%, the mass fraction of the Cu-Zn intermetallic compound is 43.5%, the thickness of the copper-zinc alloy layer is 5 μm, and the composition of the copper-zinc alloy layer is β'+γ phase.

[0153] Example 15

[0154] The preparation process is as follows:

[0155] 1) Prepare a CuZn37 brass core material with a diameter of 0.6 mm.

[0156] 2) Electroplate a zinc coating on the surface of the brass core material obtained in step 1), add a saccharide organic additive to the electroplating solution, the saccharide organic additive being sucrose or / and lactose or / and maltose, the coating thickness being 4.5 μm, the concentration of the saccharide organic additive being 8 g / L, the electroplating speed being 400 m / min, the current being 965 A, and the voltage being 5.2 V.

[0157] 3) Subject the wire blank obtained after electroplating to the first stretching and extrusion through a wire drawing die until the diameter reaches 0.48 mm. The dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° to the axis, obtaining a wire blank after the first stretching with a zinc coating having several cracks.

[0158] 4) Heat-treat the wire blank obtained after the first stretching with several cracks. The heat treatment temperature is 200 °C, the heat treatment time is 6 h, and it is cooled in the furnace to below 150 °C before being taken out of the furnace. Air is continuously introduced during the heat treatment process, obtaining a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with several cracks.

[0159] 5) Subject the heat-treated wire blank to the second stretching and extrusion through a wire drawing die until it reaches 0.25 mm, obtaining a finished electrode wire with a surface layer distributed in flakes or particles and with the copper-zinc alloy layer exposed at the gaps between the flakes or particles on the surface layer. Among them, the surface layer coverage rate is 70%, the surface layer thickness is 2 μm, the size of each micropore in the surface layer is 0.010 - 0.92 μm, the mass fraction of CuO in the surface layer is 9.5%, the mass fraction of ZnO is 44%, the mass fraction of Cu2(OH)2CO3 is 2%, the mass fraction of the Cu-Zn intermetallic compound is 44.5%, the thickness of the copper-zinc alloy layer is 4 μm, and the composition of the copper-zinc alloy layer is β'+γ phase.

[0160] Comparative Examples 1 - 5:

[0161] Comparative Example 1: A 0.25 mm specification brass electrode wire purchased on the market;

[0162] Comparative Example 2: A 0.25 mm specification zinc-plated electrode wire purchased on the market, with a pure zinc coating;

[0163] Comparative Example 3: A 0.25 mm specification gamma electrode wire purchased on the market, with a γ-phase coating. This type of electrode wire is a commonly used coated electrode wire on the market;

[0164] Comparative Example 4: A 0.25 mm high-speed electrode wire purchased on the market, with a β'+γ phase coating.

[0165] Comparative Example 5: A 0.25 mm high-speed electrode wire purchased on the market, with a β'-phase coating.

[0166] Table 1. Process data sheets of Examples 1 to 15:

[0167]

[0168]

[0169] Table 2. Data sheets of overlay composition, coverage rate and internal micropores of Examples:

[0170]

[0171]

[0172] Slow wire electrical discharge machining test:

[0173] The slow wire machine tool used for testing is the Swiss AgieCharmilles CUT E350 machine tool which is widely used in the market. The machining material is SKH-9, the thickness of the workpiece is 30 mm, the shape is a 6*6 mm square punch, and the electrode wire with a specification of 0.25 mm is used. Under the condition of cutting one and trimming four (that is, rough cutting 1 pass and fine trimming 4 passes, a total of 5 passes of machining), face machining is carried out.

[0174] Compared with the workpieces machined with the electrode wires of Comparative Examples 1-5, the workpieces machined with the electrode wires of Examples 1-15 in Table 3 show obvious advantages in cutting speed and surface finish of the machined workpieces. That is, compared with Comparative Example 1, the cutting speed of the electrode wire of the present invention is increased by 18.69% - 27.41%, and the surface finish of the machined workpiece is increased by 20.58% - 28.03%.

[0175] Table 3. Specimen electrode wires and machining test data are shown in the following table:

[0176]

[0177]

[0178] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electrode wire for electrical discharge machining, comprising a brass core material, characterized in that: It also includes a copper-zinc alloy layer and a surface layer outside the brass core material; The surface layer is distributed in a sheet or granular form on the surface of the copper-zinc alloy layer, and the copper-zinc alloy layer is exposed at the gaps between the sheets or granules of the surface layer; A number of micropores are distributed in the surface layer and at the interface between the surface layer and the copper-zinc alloy layer, and the size of the micropores in the surface layer is smaller than the size of the micropores at the interface between the surface layer and the copper-zinc alloy layer; the size of each micropore in the cross-section of the electrode wire is 0.01 - 2.8 μm.

2. The electrode wire for electric discharge machining according to claim 1, characterized in that: The surface layer covers 60% - 95% of the surface area of the copper-zinc alloy layer.

3. The electrode wire for electric spark discharge machining according to claim 1, characterized in that: The thickness of the surface layer is 2 - 7 μm.

4. The electrode wire for electric spark discharging machining according to claim 1, wherein: The composition of the copper-zinc alloy layer is β'+γ phase or β' phase.

5. The electrode wire for electric discharge machining according to claim 1, wherein: The thickness of the copper-zinc alloy layer is 4 - 10 μm.

6. A method for preparing an electrode wire for electric discharge machining according to any one of claims 1-5, characterized in that: It includes the following steps: 1). Prepare a brass core material with a diameter of 0.6 - 0.9 mm; 2). Electroplate a zinc coating on the surface of the brass core material obtained in step 1), add a saccharide organic additive to the electroplating solution to obtain a dense and brittle zinc coating containing the saccharide organic additive component, and the concentration of the saccharide organic additive is 8 - 25 g / L; 3). Subject the wire blank obtained after electroplating to the first drawing and extrusion through a drawing die to a diameter of 0.47 - 0.62 mm, and the dense and brittle zinc coating will crack along a direction perpendicular to the axis and at an acute angle greater than 30° with the axis to obtain a wire blank obtained by the first drawing and extrusion with a zinc coating having a number of cracks; 4). Heat-treat the wire blank obtained by the first drawing and extrusion with a number of cracks to obtain a heat-treated wire blank with a continuous copper-zinc alloy layer and a surface layer with a number of cracks; 5). Subject the heat-treated wire blank to the second drawing and extrusion through a drawing die to obtain a finished electrode wire with a diameter of 0.15 - 0.30 mm.

7. The preparation method of the electrode wire for electric discharge machining according to claim 6, characterized in that: In step 2), the electroplating speed is 200 - 400 m / min, the current is 965 - 1350 A, the voltage is 5.2 - 7 V, and the thickness of the zinc coating is 4.5 - 9 μm.

8. The preparation method of the electrode wire for electric discharge machining according to claim 6, characterized in that: In step 4), the heat treatment temperature is 200 - 400 °C, the heat treatment time is 2 h - 10 h, it is cooled in the furnace to below 150 °C before being taken out of the furnace, and air is continuously filled during the heat treatment process.

9. The preparation method of the electrode wire for electric discharge machining according to claim 6, characterized in that: The saccharide organic additive is sucrose, lactose, and / or maltose.

10. The preparation method of the electrode wire for electrical discharge machining according to claim 6, characterized in that: In step 3), the processing rate of the first drawing and extrusion is 35% - 65%; in step 5), the processing rate of the second drawing and extrusion is 55% - 95%.

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