JP2002126949A - Electrode wire for wire electric discharge machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new electrode wire capable of attaining higher processing speed. SOLUTION: This electrode wire is constituted mainly of a core wire of Cu or a Cu alloy and an alloy covering layer formed on the surface of the core wire, or a core wire of Cu or a Cu alloy, an alloy covering layer formed on the surface of the core wire, and a ZnO layer formed thereon. The alloy covering layer is formed out of a γ phase of a Cu-Zn alloy or a mixed phase of the γ phase and a βphase thereof, and covers 30% or more of the surface of the core wire. Preferably, irregularity with 20 μm or less difference in elevation are formed at least on the surface of the alloy covered layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode wire for wire electric discharge machining.

[0002]

2. Description of the Related Art In wire electric discharge machining, a discharge is generated between a traveling electrode wire for wire electric discharge machining (hereinafter, simply referred to as an "electrode wire") and a workpiece, and is melted and cut by generated heat. It is a processing method. It has the feature of being able to perform free-form and high-precision machining even with difficult-to-cut materials.
Its applications are expanding in many fields, mainly in die machining.

[0003] A typical electrode wire is a so-called brass electrode wire having a composition of 65 to 60 wt% Cu-35 to 40 wt% Zn. As can be seen from various reports, Zn has an effect of improving the discharge characteristics, and Zn in the electrode wire composition.
The processing speed can be improved by increasing the amount. However, when the Zn content exceeds 35 to 40% by weight, the effect of the decrease in conductivity increases, and the improvement in the processing speed reaches a peak. In addition, problems such as the difficulty in cold drawing due to the formation of a large amount of β phase also occur. For these reasons, the brass electrode wire having the above composition is most often used.

However, recently, an electrode wire having a coating layer (hereinafter, referred to as a "coated electrode wire") has been proposed as an electrode wire capable of greatly improving the processing speed, and is being used in a small amount. This coated electrode wire has a coating layer of several μm to several tens μm formed on the surface of the core wire. The core wire is made of Cu or a Cu alloy having high strength and high conductivity, and the coating layer is made of a Cu—Zn alloy having a high Zn content exceeding 40% by weight. By adopting such a layer structure, both high conductivity and high discharge characteristics can be obtained, and high-speed processing can be performed as compared with an electrode wire made of brass.

[0005]

Not only the coated electrode wire but also the conventional electrode wire has a uniform surface composition and a smooth surface property in most cases. Such a surface causes concentration of electric discharge during electric discharge machining, which is one of the causes for reducing the machining speed.

Nevertheless, the reason why the surface properties of the electrode wire are smooth is that the electrode wire is manufactured by drawing a highly ductile conductive material such as brass. Even in the conventional coated electrode wire described above, the surface layer is almost always a relatively ductile and uniform β single phase, and the surface properties are smooth.

With such a uniform surface, discharge occurs on the surface of the electrode wire close to the workpiece, and as a result, the concentration of discharge tends to occur. A recent electric discharge machine is provided with a function of avoiding the concentration of the electric discharge and controlling the electric discharge so that a stable electric discharge is possible. When this control function is activated, the disconnection is difficult, but the applied voltage is reduced, so that the processing speed is reduced. The frequency of operation of this control function appears as a difference in machining speed between electrode wires. That is, in general, an electrode wire having a high processing speed also means an electrode wire in which concentration of discharge hardly occurs.

An object of the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel electrode wire capable of obtaining a higher processing speed.

[0009]

The present invention for solving the above-mentioned problems is an electrode wire mainly composed of a core wire of Cu or Cu alloy and an alloy coating layer provided on the surface of the core wire. Is a γ phase of a Cu—Zn alloy, or γ
It is composed of a mixed phase of a phase and a β phase, and the alloy coating layer covers 30% or more of the core wire surface. And preferably, at least the height difference 2
In this case, irregularities within 0 μm are provided.

[0010] Another embodiment of the present invention relates to a method for producing Cu or C
An electrode wire mainly composed of a u-alloy core wire, an alloy coating layer provided on the surface of the core wire, and a ZnO layer provided thereon, wherein the alloy coating layer is a γ phase of a Cu—Zn alloy. Or a mixed phase of a γ phase and a β phase, and the alloy coating layer covers at least 30% of the surface of the core wire. Preferably, at least the surface of the alloy coating layer has a height difference of not more than 20 μm. It has.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to increase the processing speed of an electrode wire, it is not sufficient to simply improve the discharge characteristics of a surface layer. In order to disperse the discharge points, it is also important to make the composition of the electrode wire surface non-uniform or to make the electrode wire surface uneven. As a specific example, when the surface layer is a Cu-Zn alloy-based electrode wire, the surface layer is formed by mixing a high Zn content and a low Zn content, or a wire having a brittle layer only on the surface is used. It is important to intentionally provide irregularities on the surface of the electrode wire core by wire drawing.

Therefore, in the present invention, as described above, the composition of the electrode wire surface is made non-uniform, and preferably, the surface is provided with irregularities. As another embodiment, a ZnO layer is provided on the outermost surface of these electrode wires.

[0013] In the present invention, Cu-
The reason for using the γ phase or the mixed phase of the γ phase and the β phase of the Zn alloy is that by doing so, it is possible to improve the processing speed and form irregularities on the electrode wire surface at the same time. The γ phase contains 60% by weight or more of Zn, whereas the β phase contains only about 45% by weight. Therefore, the processing speed can be improved by using the γ phase or the mixed phase of the γ phase and the β phase for the alloy coating layer.

Although it is originally difficult to wire the brittle γ phase, when the wire is drawn as a coating layer for the ductile core wire, the γ phase in which cracks are generated is divided as the working progresses, and gradually. It is embedded in a ductile core wire, and as a result, irregularities are formed on the surface. That is, γ of moderate thickness
If the coating layer is a phase or a mixed phase of a γ phase and a β phase, irregularities can be easily formed on the electrode wire surface only by wire drawing.

In the present invention, the rate at which the alloy coating layer covers the surface of the core wire is set to 30% or more.
If it is less than 0%, the influence of the core wire itself becomes large, and the processing speed is reduced.

The reason why the height difference of the irregularities provided on the surface of the alloy coating layer is preferably within 20 μm is that the depth at which the brass-based electrode wire is consumed by general electric discharge machining is at most 20 μm. is there. That is, even if a height difference of 20 μm or more is provided, it does not contribute to further improvement of the processing speed. In the process of forming too large irregularities,
A crack deeper than that will be formed, which may cause disconnection in wire drawing.

This alloy coating layer can be formed, for example, by subjecting the core wire to hot dip galvanizing and then performing a heat treatment at a desired temperature. Further, in order to form irregularities on the surface of the alloy coating layer, it is only necessary to perform wire drawing as described above.

In another embodiment of the invention, the top layer comprises Zn
An O layer is provided, and its thickness is preferably 10 ° to 1 μm. The ZnO layer has an effect of reducing the distance between the electrode wire and the workpiece, that is, the so-called discharge gap, so that the applied energy can be efficiently used for processing. For this purpose, a thickness of 10 ° or more is required, but when the thickness exceeds 1 μm, the lower layer γ
The effect of the phase or the mixed phase of the γ phase and the β phase is lost.

Although the thickness of the ZnO layer is not necessarily required to be uniform, it is desirable that the thickness of the ZnO layer does not significantly reduce the difference in height of the irregularities provided on the surface of the alloy coating layer. This ZnO layer can be easily formed by adjusting the atmosphere when forming the alloy layer coating layer, and the thickness of the layer can also be adjusted.

[0020]

Next, the present invention will be further described with reference to examples. (Example 1) 8 mm in diameter 8 manufactured by hot extrusion
Cold drawing and heat treatment were repeatedly applied to a 0 wt% Cu-20 wt% Zn wire to produce a core wire having a diameter of 0.8 mm. A Zn plating layer having a predetermined thickness was formed on the surface of the core wire by a hot-dip plating method. Subsequently, heat treatment was performed to form a diffusion layer. Table 1 shows the heat treatment conditions and the average thickness of the alloy coating layer formed after the heat treatment.

[0021]

【table 1】

Thereafter, the cold drawing and heat treatment operations were repeated again to finally obtain an electrode wire for wire electric discharge machining of the present invention having a diameter of 0.25 mm. The structure of the obtained electrode wire was examined and shown in Table 2.

[0023]

[Table 2]

Next, the electric discharge machining speed of the electrode wire of the present invention was evaluated. The used EDM is Mitsubishi Electric DWC-11
The SKD-11 having a thickness of 30 mm, which is a common iron-based mold material, was processed by using the SKD-11. In recent electric discharge machining, machining is performed by controlling two types of pulses, a high-energy pulse for machining and a low-energy pulse for stabilizing a discharge state. Therefore, the former pulse current value Ip and the stop time OFF,
In addition, the latter pulse current value SA and stop time SB were set. As for the duration of the two types of pulses, the processing machine side determines the discharge state and performs automatic control.

This time, as recommended by Mitsubishi Electric, Ip =
400A, OFF = 5.5 μs, SA = 235A, OF
F was set to 6.0 μs. 3 minutes straight machining distance of 5
The measurement was repeated twice to determine the average processing speed. Table 3 shows the processing speed measurement results of the obtained electrode wires.

[0026]

[Table 3]

(Comparative Example 1) The coating ratio of the alloy coating layer was 23
%, An electrode wire was obtained in the same manner as in Example, and the processing speed was determined. As a result, the processing speed is 3.26 mm / mi.
n.

(Comparative Example 2) The coating ratio of the alloy coating layer was 93
%, And an electrode wire was obtained in the same manner as in Example except that the height difference between the concavities and convexities was set to 22 μm, and the processing speed was obtained. As a result, the processing speed was 4.29 mm / min, and no further increase in the processing speed was observed.

(Comparative Example 3) Conventional coated electrode wire (core wire; 8
0/20, surface layer; β-phase) provided with a ZnO layer on the surface, and the processing speed was determined in the same manner as in the example. As a result, the processing speed was 3.76 mm / min.

(Conventional Examples 1 and 2) Conventional coated electrode wires (core wire: 80/20, surface layer: β phase) (conventional example 1) and brass electrode wires (Cu / Zn ratio = 65/35) (conventional example) The processing speed was determined in the same manner as in Example using 2). as a result,
The processing speed was 3.76 and 3.05 mm / min, respectively.

From the above results, the processing speed of the electrode wire of the present invention is remarkably improved to a maximum of about 20% with respect to the conventional coated electrode wire and about 48% with respect to the conventional brass electrode wire. It is clear that.

[0032]

As described above, the electrode wire for wire electric discharge machining of the present invention has a remarkably high machining speed as compared with the conventional coated electrode wire or brass electrode wire. In a manufacturing process using an electric discharge machine, since the machining speed determines the amount of product produced per hour, an improvement in the machining speed directly leads to a cost reduction. Therefore, if the electrode wire for wire electric discharge machining according to the present invention is used, the cost can be significantly reduced as compared with the related art.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Iwao Iwao 12-7-202 Futami-cho, Nishinomiya-shi, Hyogo F-term (reference) 3C059 AA01 AB05 DA06 DB03 DC02

Claims (4)

[Claims] 1. An electrode wire mainly composed of a core wire of Cu or Cu alloy and an alloy coating layer provided on the surface of the core wire, wherein the alloy coating layer is made of a Cu—Zn alloy γ.
An electrode wire for wire electric discharge machining, comprising a phase or a mixed phase of a γ phase and a β phase, wherein the alloy coating layer covers 30% or more of the surface of the core wire. 2. A height difference 2 at least on the surface of the alloy coating layer.
2. The electrode wire according to claim 1, wherein irregularities of 0 μm or less are provided. 3. An electrode wire mainly composed of a core wire of Cu or Cu alloy, an alloy coating layer provided on the surface of the core wire, and a ZnO layer provided thereon.
The alloy coating layer is a γ phase of a Cu—Zn alloy, or a γ phase and β
An electrode wire for wire electric discharge machining, wherein the electrode wire is composed of a mixed phase with a phase, and the alloy coating layer covers 30% or more of the core wire surface. 4. A height difference 2 at least on the surface of the alloy coating layer.
4. The electrode wire according to claim 3, wherein irregularities within 0 μm are provided.