JP2004330352A - Electrode wire for wire electric discharge machining, and surface reforming method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode wire for wire electric discharge machining and a surface reforming method using the same, which electrode wire has excellent discharge characteristics and can achieve the surface reforming of a workpiece. <P>SOLUTION: The electrode wire 10 for the wire electric discharge machining has at least one coating layer around a core material 11. A Ti or Ti alloy layer 12 is provided around the core material 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５３】
表１に示すように、実施例１〜３の各電極線は、従来例１と比較して放電加工速度が１０〜２５％も向上していた。また、実施例１〜３の各電極線を用いて放電加工を行った被加工物と従来例１の電極線を用いて放電加工を行った被加工物とを比較すると、従来例１の電極線を用いて放電加工を行った被加工物は腐食が著しかった。これに対して、実施例１〜３の各電極線を用いて放電加工を行った被加工物は全く腐食が認められず、優れた耐食性を示した。このことから、実施例１〜３の各電極線を用いて被加工物の放電加工を行うことで、被加工物の表面に耐食性に優れた被膜を形成できることがわかる。
【００５４】
比較例１の電極線は、耐食性は優れていたものの、被覆層におけるＣｕ−Ｚｎ合金層のＺｎ濃度が低すぎるため、放電加工速度の向上が殆ど認められなかった。また、比較例２の電極線は、Ｃｕ−Ｚｎ合金層のＺｎ濃度が高すぎるため、伸線加工中に断線が生じ、電極線を作製することができなかった。
【００５５】
【発明の効果】
以上要するに本発明によれば、放電特性が良好で、かつ、被加工物の表面改質が可能なワイヤ放電加工用電極線が得られるという優れた効果を発揮する。
【図面の簡単な説明】
【図１】本発明の好適一実施形態に係るワイヤ放電加工用電極線の横断面図である。
【図２】本発明の別の好適一実施形態に係るワイヤ放電加工用電極線の横断面図である。
【図３】本発明の更に別の好適一実施形態に係るワイヤ放電加工用電極線の横断面図である。
【図４】図１の変形例を示す横断面図である。
【図５】図２の変形例を示す横断面図である。
【図６】図３の変形例を示す横断面図である。
【符号の説明】
１０ ワイヤ放電加工用電極線
１１ 心材
１２ Ｔｉ層（Ｔｉ又はＴｉ合金層）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrode wire for wire electric discharge machining and a method for modifying the surface of a workpiece using the electrode wire for wire electric discharge machining.
[0002]
[Prior art]
As an electrode wire for wire electric discharge machining, an electrode wire of a Cu—Zn alloy is used. This electrode wire is excellent in discharge characteristics such as processing speed and processing accuracy, and has further advantageous characteristics in terms of cost.
[0003]
Until now, as this type of electrode wire, a single alloy wire (Cu-35 wt% Zn alloy (65/35 brass)) containing 32 to 36 wt% Zn has been used. In processing electrode wires, high-speed processability has been particularly emphasized. For this reason, for example, a Cu—Zn alloy layer having a higher Zn concentration than before is provided around a core material made of a Cu alloy such as a Cu-2.0 wt% Sn alloy or a Cu-0.3 wt% Sn alloy. A coated electrode wire for electric discharge machining has been proposed (see, for example, Patent Document 1).
[0004]
In addition, as a method of modifying the processing surface of the workpiece by electric discharge machining, the workpiece is arranged in a machining fluid, and silicon is mixed in a powder state in the machining fluid, and is mixed with the machining surface of the workpiece. A method for forming a coating has been proposed (for example, see Patent Document 2).
[0005]
[Patent Document 1]
JP-A-5-339664 [Patent Document 2]
JP-A-2-83119 [0006]
[Problems to be solved by the invention]
Conventional general-purpose single alloy wire (65/35 brass wire) and the electrode wire described in Patent Document 1 are intended to improve the processing speed and the accuracy of the processed surface of the workpiece, and The surface of the material cannot be modified.
[0007]
The method described in Patent Literature 2 can form a film on the processing surface of a workpiece, but requires a step of mixing silicon powder into a processing liquid, and thus requires a large number of steps for electric discharge machining. There was a problem. Further, the method described in Patent Literature 2 requires a circulation device for uniformly dispersing the silicon powder in the working fluid, and thus has a problem in that the cost of the device is increased. Further, the method described in Patent Document 2 is mainly applied to a die engraving machine for processing a mold or the like, and does not use a wire-shaped (or linear) electrode. Therefore, it has been difficult to process a lead frame mold or a thick workpiece requiring fine processing.
[0008]
In view of the above circumstances, an object of the present invention, which has been devised in consideration of the above circumstances, is to provide an electrode wire for wire electric discharge machining having good discharge characteristics and capable of surface modification of a workpiece, and a surface modification method using the same. To provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an electrode wire for wire electric discharge machining according to the first invention is an electrode wire for wire electric discharge machining provided with at least one coating layer around a core material, wherein the coating layer is Ti or a Ti alloy. It has a layer.
[0010]
Further, the electrode wire for wire electric discharge machining according to the second invention is an electrode wire for wire electric discharge machining provided with at least one coating layer around a core material, wherein a Ti or Ti alloy layer is provided on the outer periphery of the core material. Things.
[0011]
Further, in the electrode wire for wire electric discharge machining according to the third invention, in the electrode wire for wire electric discharge machining provided with at least one coating layer around the core, a Ti or Ti alloy layer is provided on the outer periphery of the core. The Cu or Zn alloy layer is provided on the outer periphery of the Ti or Ti alloy layer.
[0012]
Further, in the electrode wire for wire electric discharge machining according to the fourth invention, in the electrode wire for wire electric discharge machining provided with at least one coating layer around the core, a Cu-Zn alloy layer is provided on the outer periphery of the core, A Ti or Ti alloy layer is provided on the outer periphery of the Cu-Zn alloy layer.
[0013]
Here, the coating layer may have a pure Zn layer as the outermost layer. Further, it is preferable that the Zn concentration of the Cu—Zn alloy layer is 32 to 46% by weight. In addition, the heartwood is
Pure Cu wire,
Cu-0.02-0.2% by weight Zr alloy wire,
Cu-0.15 to 0.25 wt% Sn-0.15 to 0.25 wt% In alloy wire,
Cu-0.15 to 0.70% by weight Sn alloy wire,
Cu-0.15 to 0.70 wt% In alloy wire,
Cu-5-30% by weight Zn alloy wire,
An alloy wire obtained by adding at least one of Zr, Cr, Si, Mg, Al, Fe, P, Ni, Ag, and Sn to Cu-5 to 30% by weight Zn;
Cu-0.2-20% by weight Ag alloy wire,
Fe-based alloy wire,
Copper-coated steel wire,
Copper alloy coated steel wire,
Or it is preferable to be comprised with a copper and a copper alloy covering composite wire.
[0014]
By arranging a Ti or Ti alloy layer as a coating layer on the outer periphery of a core material having good conductivity, an electrode wire for wire electric discharge machining having good discharge characteristics and capable of modifying the surface of a workpiece is obtained. Can be
[0015]
On the other hand, the surface modification method using the electrode wire for wire electric discharge machining according to the present invention performs the electric discharge machining of the workpiece using the electrode wire for wire electric discharge machining described above, and performs a process between the workpiece and the wire electrode. A discharge composed of a simple substance of Ti or a Ti alloy or a compound thereof constituting the coating layer of the electrode wire is formed on the processed surface of the workpiece by the discharge energy, and the surface of the workpiece is modified. Do the quality.
[0016]
By performing electrical discharge machining of a workpiece using the above-described electrode wire for wire electrical discharge machining, electrical discharge machining can be performed with good discharge characteristics, and surface modification of the workpiece can be performed.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.
[0018]
FIG. 1 shows a cross-sectional view of an electrode wire for wire electric discharge machining according to a preferred embodiment of the present invention.
[0019]
As shown in FIG. 1, an electrode wire 10 for wire electric discharge machining according to the present embodiment is provided with a Ti layer (or a Ti alloy layer) 12 on the outer periphery of a core material 11. The coating layer of the electrode wire 10 is constituted by a single layer of the Ti layer 12.
[0020]
The ratio (t / D) between the thickness t of the coating layer and the diameter D is 0.10 to 0.20, preferably 0.12 to 0.15. In the present embodiment, since the coating layer is one layer of the Ti layer 12, t / D can be rephrased as a ratio between the thickness of the Ti layer 12 and the diameter D.
[0021]
The heartwood 11 is
Pure Cu wire,
Cu-0.02-0.2% by weight Zr alloy wire,
Cu-0.15 to 0.25 wt% Sn-0.15 to 0.25 wt% In alloy wire,
Cu-0.15 to 0.70% by weight Sn alloy wire,
Cu-0.15 to 0.70 wt% In alloy wire,
Cu-5-30% by weight Zn alloy wire,
An alloy wire obtained by adding at least one of Zr, Cr, Si, Mg, Al, Fe, P, Ni, Ag, and Sn to Cu-5 to 30% by weight Zn;
Cu-0.2-20% by weight Ag alloy wire,
Fe-based alloy wire,
Copper-coated steel wire,
Copper alloy coated steel wire,
Or, it is composed of copper and copper alloy coated composite wire. Here, as the Fe-based alloy, an alloy having high conductivity is preferable. By constituting the core material 11 with these wires, the conductivity of the electrode wires 10 is improved, and the discharge characteristics can be improved.
[0022]
Next, a surface modification method using the electrode wire for wire electric discharge machining according to the present embodiment will be described.
[0023]
Electric discharge machining (cutting) is performed on a workpiece (not shown) using the above-described electrode wire 10. The electric discharge machining is performed in a state where the workpiece is arranged in the machining fluid. The working fluid is mainly composed of oil (for example, liquid hydrocarbon such as kerosene) or silicon oil.
[0024]
Next, by applying a voltage between the workpiece and the electrode wire 10 (wire electrode), a discharge is generated between the workpiece and the wire electrode. Due to the discharge energy, the coating layer of the electrode wire 10 evaporates, and a coating composed of a simple substance of Ti (or Ti alloy) and / or a compound thereof constituting the coating layer is formed on the processing surface of the workpiece. Then, the surface of the workpiece is modified. When the Ti in the coating layer evaporates, the Ti reacts with the working fluid to generate a Ti compound, for example, TiC.
[0025]
Next, the operation of the present embodiment will be described.
[0026]
According to the electrode wire 10 according to the present embodiment, a Ti layer 12 having excellent corrosion resistance is provided as a coating layer on the outer periphery of a core material 11 having high conductivity and high heat resistance. By performing the electric discharge machining, the Ti (or Ti alloy) constituting the coating layer migrates (adheres) as a consumable powder to the machining surface of the workpiece (not shown) during the electric discharge machining, and A film is formed on the processed surface. Since the Ti compound constituting the coating has extremely high hardness and excellent wear resistance, the surface of the workpiece is modified by forming the coating, thereby improving the corrosion resistance and wear resistance of the workpiece surface. . Here, since the film on the surface of the workpiece can be formed simultaneously with the wire electric discharge machining, the surface can be easily and inexpensively modified.
[0027]
Further, the electrode wire 10 according to the present embodiment can perform complicated fine processing of a workpiece and processing of a thick workpiece, similarly to the conventional electrode wire for wire electric discharge machining. Therefore, it can be easily applied to a lead frame mold requiring fine processing and a thick workpiece having a thickness of 300 mm or more.
[0028]
As described above, according to the electrode wire 10 according to the present embodiment, electric discharge machining can be performed with discharge characteristics equal to or higher than that of the conventional electrode wire, and the surface modification of the workpiece can be performed simultaneously with the electric discharge machining. Since it can be performed, the surface modification process can be simplified, and a significant improvement in productivity can be expected. As a result, the production cost of the workpiece can be reduced.
[0029]
In the surface modification method using the electrode wire 10 according to the present embodiment, the case where the surface modification is performed simultaneously with the processing (cutting) of the workpiece has been described, but the cutting is not performed and the surface modification is performed. Only quality may be performed. For example, the workpiece is cut out in advance using a general-purpose brass electrode wire or the like, and the vicinity of the processed surface of the cut out workpiece is subjected to electric discharge machining using the electrode wire 10 according to the present embodiment. Alternatively, only the surface modification of the workpiece can be performed.
[0030]
Next, another embodiment of the present invention will be described with reference to the accompanying drawings.
[0031]
FIG. 2 shows a cross-sectional view of an electrode wire for wire electric discharge machining according to another preferred embodiment of the present invention. The same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description of these members will be omitted.
[0032]
As shown in FIG. 2, the electrode wire 20 for wire electric discharge machining according to the present embodiment is provided with a Ti layer (or a Ti alloy layer) 22 on the outer periphery of the core material 11 and a Cu—Zn alloy on the outer periphery of the Ti layer 22. The layer 23 is provided. The coating layer of the electrode wire 20 is composed of two layers, a Ti layer 22 and a Cu—Zn alloy layer 23.
[0033]
The ratio (t / D) between the thickness t of the coating layer and the diameter D is 0.10 to 0.20, preferably 0.12 to 0.15. In the present embodiment, since the coating layer is two layers of the Ti layer 22 and the Cu—Zn alloy layer 23, there is a ratio between the layer thickness of each of the layers 23 and 24 and the diameter D. The ratio between the thickness of the Ti layer 22 and the diameter D is 0.05 to 0.10, preferably 0.05 to 0.08. The ratio between the thickness of the Cu—Zn alloy layer 23 and the diameter D is 0.05 to 0.10, preferably 0.07 to 0.09. Here, the layer thickness of the Ti layer 22 and the layer thickness of the Cu—Zn alloy layer 23 are appropriately determined according to a balance between discharge characteristics and surface modification properties.
[0034]
The reason why the Zn concentration of the Cu—Zn alloy constituting the Cu—Zn alloy layer 23 is set to 32 to 46% by weight is that if the Zn concentration is less than 32% by weight, the discharge characteristics of the electrode wire 20 are significantly reduced. is there. On the other hand, if the Zn concentration exceeds 46% by weight, the wire drawing processability is remarkably reduced, and the wire is broken during the wire drawing process.
[0035]
The electrode wire 20 according to the present embodiment has a structure in which a Cu—Zn alloy layer 23 is provided on the outer periphery of the electrode wire 10 according to the previous embodiment. According to the electrode wire 20 according to the present embodiment, by forming the Cu—Zn alloy layer 23 having excellent discharge characteristics on the outer layer side of the coating layer, the electric discharge machining speed of the electrode wire 20 is greatly improved. Further, since the Ti layer 22 is provided on the inner layer side of the coating layer, the surface of the workpiece can be modified at the time of electric discharge machining, similarly to the electrode wire 10 according to the previous embodiment. .
[0036]
FIG. 3 shows a cross-sectional view of an electrode wire for wire electric discharge machining according to still another preferred embodiment of the present invention. The same members as those in FIG. 2 are denoted by the same reference numerals, and detailed description of these members will be omitted.
[0037]
As shown in FIG. 3, the electrode wire 30 for wire electric discharge machining according to the present embodiment has a structure in which the Ti layer (or Ti alloy layer) 22 and the Cu- The position where the Zn alloy layer 23 is formed is reversed.
[0038]
Also in the electrode wire 30 according to the present embodiment, similarly to the electrode wire 20 according to the previous embodiment, improvement of the electric discharge machining speed of the electrode wire 30 and surface modification of the workpiece at the time of electric discharge machining are simultaneously achieved. can do.
[0039]
On the other hand, as shown in a modified example of the electrode wires 10, 20, 30 in FIGS. 1 to 3 as electrode wires 40, 50, 60 in FIGS. 4 to 6, a pure Zn layer 44 is provided as the outermost layer of the coating layer. It may be. Here, the ratio between the layer thickness of the pure Zn layer 44 and the diameter D in the coating layer is 0.01 to 0.05, preferably 0.01 to 0.03. If this ratio is too small, that is, if the layer thickness of the pure Zn layer 44 is too thin, good discharge performance of the pure Zn layer 44 cannot be sufficiently exhibited, and an improvement in the electric discharge machining speed cannot be expected. If this ratio is too large, that is, if the thickness of the pure Zn layer 44 is too thick, the ratio of the cross-sectional area of the pure Zn layer 44 to the entire electrode wire increases, and the tensile strength and conductivity of the electrode wire itself increase. As a result, a decrease in the electric discharge machining speed cannot be expected.
[0040]
Each of the electrode wires 40, 50, and 60 has a pure Zn layer 44 having a predetermined thickness on the outermost layer of the coating layer, so that the electric discharge machining speed is further improved as compared with the electrode wires 10, 20, and 30. improves. In addition, since the Ti layers 12 and 22 are provided on the inner layer side of the pure Zn layer 44, the surface modification of the workpiece can be performed simultaneously with the electric discharge machining.
[0041]
As described above, the embodiments of the present invention are not limited to the above-described embodiments, and it is needless to say that various other embodiments are also possible.
[0042]
【Example】
Next, the present invention will be described based on examples, but the present invention is not limited to these examples.
[0043]
(Example 1)
A Cu-0.19Sn-0.2In alloy wire having a diameter of 4.0 mm (unit:% by weight) was used as a core material, and this core material was inserted into a Ti pipe having a thickness of 0.7 mm, followed by drawing and heat treatment. Was repeated to produce an electrode wire having a wire diameter of 0.25 mm.
[0044]
(Example 2)
A Cu-0.19Sn-0.2In alloy wire having a diameter of 4.0 mm (unit:% by weight) was used as a core material, and this core material was inserted into a 0.3 mm-thick Ti pipe and subjected to wire drawing. Adjust the wire diameter to 4.0 mm. After inserting the wire into a 0.4 mm-thick Cu-35Zn alloy pipe (unit: wt%), an electrode wire having a wire diameter of 0.25 mm was produced by repeatedly performing wire drawing and heat treatment.
[0045]
(Example 3)
The electrode wire having a wire diameter of 0.25 mm produced in Example 1 was subjected to electro-Zn plating with a thickness of 0.005 mm, and then subjected to wire drawing to produce an electrode wire having a wire diameter of 0.25 mm. .
[0046]
(Comparative Example 1)
A Cu-0.19Sn-0.2In alloy wire having a diameter of 4.0 mm (unit:% by weight) was used as a core material, and this core material was inserted into a 0.3 mm-thick Ti pipe and subjected to wire drawing. Adjust the wire diameter to 4.0 mm. After inserting the wire into a 0.4 mm thick Cu-30Zn alloy pipe (unit:% by weight), an electrode wire having a wire diameter of 0.25 mm was produced by repeatedly performing wire drawing and heat treatment.
[0047]
(Comparative Example 2)
A Cu-0.19Sn-0.2In alloy wire having a diameter of 4.0 mm (unit:% by weight) was used as a core material, and this core material was inserted into a 0.3 mm-thick Ti pipe and subjected to wire drawing. Adjust the wire diameter to 4.0 mm. A 0.4 mm-thick Cu-48Zn alloy layer was hot-extrusion-coated on the outer periphery of the wire, and then wire drawing and heat treatment were repeatedly performed to produce an electrode wire having a wire diameter of 0.25 mm.
[0048]
(Conventional example 1)
An electrode wire having a diameter of 0.25 mm was prepared using a single alloy of Cu-35Zn (unit: wt%).
[0049]
Table 1 shows the core material composition, the structure of the coating layer, the electric discharge machining speed, and the corrosion resistance in each of the electrode wires of Examples 1 to 3, Comparative Examples 1 and 2, and Conventional Example 1.
[0050]
The measurement of the electric discharge machining speed was performed by using the electrode wires of Examples 1 to 3, Comparative Examples 1 and 2, and Conventional Example 1 and made of a steel material (SKD-11 [JIS standard]) and having a thickness of 50 mm. It was measured by performing electrical discharge machining on the object. Here, the electric discharge machining speed is a relative value when the electric discharge machining speed of the electrode wire of Conventional Example 1 is 1.0.
[0051]
The corrosion resistance was evaluated by immersing each processed workpiece in aqua regia for 10 minutes and observing the appearance of the corrosion of the processed workpiece. Here, the evaluation of corrosion resistance was evaluated as ○ when no corrosion was observed, and as × when corrosion was remarkable.
[0052]
[Table 1]

[0053]
As shown in Table 1, in each of the electrode wires of Examples 1 to 3, the electric discharge machining speed was improved by 10 to 25% as compared with Conventional Example 1. Further, when a workpiece subjected to electrical discharge machining using each of the electrode wires of Examples 1 to 3 and a workpiece subjected to electrical discharge machining using the electrode wire of Conventional Example 1 are compared, the electrode of Conventional Example 1 The workpiece subjected to electric discharge machining using the wire was significantly corroded. On the other hand, the workpieces subjected to electrical discharge machining using the electrode wires of Examples 1 to 3 showed no corrosion at all, and exhibited excellent corrosion resistance. From this, it is understood that a film excellent in corrosion resistance can be formed on the surface of the workpiece by performing electric discharge machining of the workpiece using each of the electrode wires of Examples 1 to 3.
[0054]
Although the electrode wire of Comparative Example 1 was excellent in corrosion resistance, the improvement of the electric discharge machining speed was hardly recognized because the Zn concentration of the Cu—Zn alloy layer in the coating layer was too low. In the electrode wire of Comparative Example 2, since the Zn concentration of the Cu—Zn alloy layer was too high, the wire was broken during the wire drawing, and the electrode wire could not be manufactured.
[0055]
【The invention's effect】
In short, according to the present invention, an excellent effect of obtaining an electrode wire for wire electric discharge machining having good discharge characteristics and capable of modifying the surface of a workpiece is obtained.
[Brief description of the drawings]
FIG. 1 is a transverse sectional view of an electrode wire for wire electric discharge machining according to a preferred embodiment of the present invention.
FIG. 2 is a cross sectional view of an electrode wire for wire electric discharge machining according to another preferred embodiment of the present invention.
FIG. 3 is a cross-sectional view of an electrode wire for wire electric discharge machining according to still another preferred embodiment of the present invention.
FIG. 4 is a transverse sectional view showing a modification of FIG.
FIG. 5 is a transverse sectional view showing a modification of FIG. 2;
FIG. 6 is a cross-sectional view showing a modification of FIG.
[Explanation of symbols]
Reference Signs List 10 electrode wire for wire electric discharge machining 11 core material 12 Ti layer (Ti or Ti alloy layer)

Claims (8)

An electrode wire for wire electric discharge machining comprising at least one coating layer provided around a core material, wherein the coating layer has a Ti or Ti alloy layer. An electrode wire for wire electric discharge machining comprising a core material and at least one coating layer provided thereon, wherein a Ti or Ti alloy layer is provided on an outer periphery of the core material. In an electrode wire for wire electric discharge machining having at least one coating layer provided around a core, a Ti or Ti alloy layer is provided on the outer periphery of the core, and a Cu-Zn alloy layer is provided on the outer periphery of the Ti or Ti alloy layer. An electrode wire for wire electric discharge machining. In an electrode wire for wire electric discharge machining provided with at least one coating layer around a core material, a Cu-Zn alloy layer is provided on the outer periphery of the core material, and a Ti or Ti alloy layer is provided on the outer periphery of the Cu-Zn alloy layer. An electrode wire for wire electric discharge machining. The electrode wire for wire electric discharge machining according to any one of claims 1 to 4, wherein the coating layer has a pure Zn layer as an outermost layer. The electrode wire according to any one of claims 3 to 5, wherein the Cu-Zn alloy layer has a Zn concentration of 32 to 46% by weight. The above heartwood is
Pure Cu wire,
Cu-0.02-0.2% by weight Zr alloy wire,
Cu-0.15 to 0.25 wt% Sn-0.15 to 0.25 wt% In alloy wire,
Cu-0.15 to 0.70% by weight Sn alloy wire,
Cu-0.15 to 0.70 wt% In alloy wire,
Cu-5-30% by weight Zn alloy wire,
An alloy wire obtained by adding at least one of Zr, Cr, Si, Mg, Al, Fe, P, Ni, Ag, and Sn to Cu-5 to 30% by weight Zn;
Cu-0.2-20% by weight Ag alloy wire,
Fe-based alloy wire,
Copper-coated steel wire,
Copper alloy coated steel wire,
Or copper and copper alloy coated composite wire,
The electrode wire for wire electric discharge machining according to any one of claims 1 to 6, comprising: An electrical discharge machining of a workpiece is performed using the electrode wire for wire electrical discharge machining according to any one of claims 1 to 7, a discharge is generated between the workpiece and the wire electrode, and an electrode wire is formed by the discharge energy. An electrode for wire electric discharge machining, wherein a coating composed of a simple substance of Ti or Ti alloy or a compound thereof constituting a coating layer is formed on a processing surface of a workpiece, and the surface of the workpiece is modified. Surface modification method using wires.

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